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Sample records for ag cd hg

  1. Biological interaction between transition metals (Ag, Cd and Hg), selenide/sulfide and selenoprotein P.

    PubMed

    Sasakura, C; Suzuki, K T

    1998-09-01

    The interaction between transition metals (Ag+, Cd2+ and Hg2+) and selenium (Se) in the bloodstream was studied in vitro by means of the HPLC--inductively coupled argon plasma-mass spectrometry (ICP MS) method. Transition metal ions and selenide (produced in vitro from selenite in the presence of glutathione) or sulfide (Na2S) formed a (metal-Se/S) complex, which then bound to a plasma protein, selenoprotein P (Sel P), to form a ternary complex, (metal-Se/S)-Sel P. The molar ratios of metals to Se were 1:1 for Hg/Se and Cd/Se, but either 1:1 or 2:1 for Ag/Se, depending on the ratio of their doses. The results indicate that the interaction between transition metals and Se occurs through the general mechanism, i.e., transition metal ions and selenide form the unit complex (metal-Se)n, and then the complex binds to selenoprotein P to form the ternary complex ¿(metal-Se)n¿m--seleno-protein P in the bloodstream. PMID:9833321

  2. Ion conduction in the Ag{sub 2}HgI{sub 4}-Cu{sub 2}HgI{sub 4} systems doped with Cd{sup 2+}, K{sup +}, and Na{sup +}

    SciTech Connect

    Nair, S.M.; Yahya, A.I.; Ahmad, A.

    1996-03-01

    Ion conductivities of face centered cubic Ag{sub 2}HgI{sub 4}-Cu{sub 2}HgI{sub 4} systems doped with Cd{sup 2+}, K{sup +}, and Na{sup +} were measured. In 67 mol% Ag{sub 2}HgI{sub 4} solid solution doped with Cd{sup 2+} ions, the phase transition occurs at a lower temperature than in the parent compounds and the system shows higher conductivity. The increase in conductivity is discussed in terms of vacancies produced. K{sup +} doped Ag{sub 2}HgI{sub 4} exhibits higher conductivity prior to the phase transition, which is attributed to lattice loosening. A decrease in conductivity is observed above 140{degrees}C. This is interpreted in terms of anion framework collapse. Na{sup +} doped Ag{sub 2}HgI{sub 4} shows high conductivity for the high temperature phase because of the small size of Na{sup +} ions. The activation energy for ionic motion for all the samples is calculated from the graph of log({delta}T) versus 1/T.

  3. Flowing Liquid Anode Atmospheric Pressure Glow Discharge as an Excitation Source for Optical Emission Spectrometry with the Improved Detectability of Ag, Cd, Hg, Pb, Tl, and Zn.

    PubMed

    Greda, Krzysztof; Swiderski, Krzysztof; Jamroz, Piotr; Pohl, Pawel

    2016-09-01

    A novel atmospheric pressure glow discharge generated in contact with a flowing liquid anode (FLA-APGD) was developed as the efficient excitation source for the optical emission spectrometry (OES) detection. Differences in the appearance and the electrical characteristic of the FLA-APGD and a conventional system operated with a flowing liquid cathode (FLC-APGD) were studied in detail and discussed. Under the optimal operating conditions for the FLA-APGD, the emission from the analytes (Ag, Cd, Hg, Pb, Tl, and Zn) was from 20 to 120 times higher as compared to the FLC-APGD. Limits of detections (LODs) established with a novel FLA-APGD system were on average 20 times better than those obtained for the FLC-APGD. A further improvement of the LODs was achieved by reducing the background shift interferences and, as a result, the LODs for Ag, Cd, Hg, Pb, Tl, and Zn were 0.004, 0.040, 0.70, 1.7, 0.035, and 0.45 μg L(-1), respectively. The precision of the FLA-APGD-OES method was evaluated to be within 2-5% (as the relative standard deviation of the repeated measurements). The method found its application in the determination of the content of Ag, Cd, Hg, Pb, Tl, and Zn in a certified reference material (CRM) of Lobster hepatopancreas (TORT-2), four brass samples as well as mineral water and tea leaves samples spiked with the analytes. In the case of brass samples, a reference method, i.e., inductively coupled plasma optical emission spectrometry (ICP-OES) was used. A good agreement between the results obtained with FLA-APGD-OES and the certified values for the CRM TORT-2 as well as the reference values obtained with ICP-OES for the brass samples was revealed, indicating the good accuracy of the proposed method. The recoveries obtained for the spiked samples of mineral water and tea leaves were within the range of 97.5-102%. PMID:27476678

  4. Syntheses, crystal structures and fluorescent properties of Cd(II), Hg(II) and Ag(I) coordination polymers constructed from 1H-1,2,4-triazole-1-acetic acid

    SciTech Connect

    Ding Degang; Xie Lixia; Fan Yaoting; Hou Hongwei; Xu Yan

    2009-06-15

    Three new d{sup 10} coordination polymers, namely [Cd(taa)Cl]{sub n}1, [Hg(taa)Cl]{sub n}2, and [Ag{sub 1.5}(taa)(NO{sub 3}){sub 0.5}]{sub n}3 (taa=1H-1,2,4-triazole-1-acatate anion) have been prepared and characterized by elemental analysis, IR, and single crystal X-ray diffraction. Compound 1 consists of two-dimensional layers constructed by carboxyl-linked helical chains, which are further linked through carboxyl group to generate a unique 3D open framework. Topological analysis reveals that the structure of 1 can be classified as an unprecedented (3,8)-connected network with the Schlaefli symbol (4.5{sup 2}){sub 2}(4{sup 2}.5{sup 8}.6{sup 14}.7{sup 3}.8). Compound 2 manifests a doubly interpenetrated decorated alpha-polonium cubic network with the Schlaefli symbol of (4{sup 10}.6{sup 2}.8{sup 3}). Compound 3 consists of 2D puckered layers made up of Ag centers and taa{sup -} bridges. In addition, all of these compounds are photoluminescent in the solid state with spectra that closely resemble those of the ligand precursor. - Graphical abstract: Three new compounds based on 1H-1,2,4-triazole-1-acetic acid and Cd(II), Hg(II) and Ag(I) salts display luminescent properties and may be potential candidates for luminescent materials.

  5. HgCdTe barrier infrared detectors

    NASA Astrophysics Data System (ADS)

    Kopytko, M.; Rogalski, A.

    2016-05-01

    In the last decade, new strategies to achieve high-operating temperature (HOT) detectors have been proposed, including barrier structures such as nBn devices, unipolar barrier photodiodes, and multistage (cascade) infrared detectors. The ability to tune the positions of the conduction and valence band edges independently in a broken-gap type-II superlattices is especially helpful in the design of unipolar barriers. This idea has been also implemented in HgCdTe ternary material system. However, the implementation of this detector structure in HgCdTe material system is not straightforward due to the existence of a valence band discontinuity (barrier) at the absorber-barrier interface. In this paper we present status of HgCdTe barrier detectors with emphasis on technological progress in fabrication of MOCVD-grown HgCdTe barrier detectors achieved recently at the Institute of Applied Physics, Military University of Technology. Their performance is comparable with state-of-the-art of HgCdTe photodiodes. From the perspective of device fabrication their important technological advantage results from less stringent surface passivation requirements and tolerance to threading dislocations.

  6. Synthesis of Starch-Stabilized Ag Nanoparticles and Hg2+ Recognition in Aqueous Media

    NASA Astrophysics Data System (ADS)

    Fan, Yingju; Liu, Zhen; Wang, Le; Zhan, Jinhua

    2009-10-01

    The starch-stabilized Ag nanoparticles were successfully synthesized via a reduction approach and characterized with SPR UV/Vis spectroscopy, TEM, and HRTEM. By utilizing the redox reaction between Ag nanoparticles and Hg2+, and the resulted decrease in UV/Vis signal, we develop a colorimetric method for detection of Hg2+ ion. A linear relationship stands between the absorbance intensity of the Ag nanoparticles and the concentration of Hg2+ ion over the range from 10 ppb to 1 ppm at the absorption of 390 nm. The detection limit for Hg2+ ions in homogeneous aqueous solutions is estimated to be ~5 ppb. This system shows excellent selectivity for Hg2+ over other metal ions including Na+, K+, Ba2+, Mg2+, Ca2+, Fe3+, and Cd2+. The results shown herein have potential implications in the development of new colorimetric sensors for easy and selective detection and monitoring of mercuric ions in aqueous solutions.

  7. MBE HgCdTe heterostructure detectors

    NASA Technical Reports Server (NTRS)

    Schulman, Joel N.; Wu, Owen K.

    1990-01-01

    HgCdTe has been the mainstay for medium (3 to 5 micron) and long (10 to 14 micron) wavelength infrared detectors in recent years. Conventional growth and processing techniques are continuing to improve the material. However, the additional ability to tailor composition and placement of doped layers on the tens of angstroms scale using molecular beam epitaxy (MBE) provides the opportunity for new device physics and concepts to be utilized. MBE-based device structures to be discussed here can be grouped into two categories: tailored conventional structures and quantum structures. The tailored conventional structures are improvements on familiar devices, but make use of the ability to create layers of varying composition, and thus band gap, at will. The heterostructure junction can be positioned independently of doping p-n junctions. This allows the small band gap region in which the absorption occurs to be separated from a larger band gap region in which the electric field is large and where unwanted tunneling can occur. Data from hybrid MBE/liquid phase epitaxy (LPE)/bulk structures are given. Quantum structures include the HgTe-CdTe superlattice, in which the band gap and transport can be controlled by alternating thin layers (tens of angstroms thick) of HgTe and CdTe. The superlattice has been shown to exhibit behavior which is non-alloy like, including very high hole mobilities, two-dimensional structure in the absorption coefficient, resonant tunneling, and anisotropic transport.

  8. Isothermal vapor phase epitaxy and rf sputtering for band gap engineered HgCdTe

    NASA Astrophysics Data System (ADS)

    Adamiec, Krzysztof; Gawron, Waldemar; Piotrowski, Jozef

    1997-06-01

    The present high quality HgCdTe photodetectors are based on heterostructures with complicated band gap and doping profiles. Such structures can be obtained by combination of Isothermal Vapor Phase Epitaxy (ISO VPE) and RDF sputtering of CdTe. Cadmium Telluride exhibits unique properties - transparency to IR light, low conductivity, nearly lattice match and chemically compatibility to HgCdTe. Thus, low defect densities and hence low surface state density at the CdTe/HgCdTe interface are expected, which in turn lead to low surface recombination velocities and long effective lifetimes. The immediate use of CdTe epilayer is passivation of HgCdTe. High quality layers HgCdTe have been grown on CdTe substrates by open tube ISO VPE. CdTe layers have been obtained by RF magnetron sputtering on to previously deposited HgCdTe layers in 400 LS Leybold AG System. The substrate temperature can be varied form 20 to 90 degrees C. Thermal treatment has been performed in Hg/H2 atmosphere in reusable chamber at temperatures 200-400 degrees C. The resulting heterostructures have been characterized by visual microscopy with Nomarski contrast, Hall measurements and IR transmittance. This technic and photolithography has been extensively used for successful fabrication of heterojunction contact photoresistors and heterostructure photodiodes.

  9. Syntheses, crystal structures and fluorescent properties of Cd(II), Hg(II) and Ag(I) coordination polymers constructed from 1H-1,2,4-triazole-1-acetic acid

    NASA Astrophysics Data System (ADS)

    Ding, De-Gang; Xie, Li-Xia; Fan, Yao-Ting; Hou, Hong-Wei; Xu, Yan

    2009-06-01

    Three new d10 coordination polymers, namely [Cd(taa)Cl] n1, [Hg(taa)Cl] n2, and [Ag 1.5(taa)(NO 3) 0.5] n3 (taa=1H-1,2,4-triazole-1-acatate anion) have been prepared and characterized by elemental analysis, IR, and single crystal X-ray diffraction. Compound 1 consists of two-dimensional layers constructed by carboxyl-linked helical chains, which are further linked through carboxyl group to generate a unique 3D open framework. Topological analysis reveals that the structure of 1 can be classified as an unprecedented (3,8)-connected network with the Schläfli symbol (4.5 2) 2(4 2.5 8.6 14.7 3.8). Compound 2 manifests a doubly interpenetrated decorated α-polonium cubic network with the Schläfli symbol of (4 10.6 2.8 3). Compound 3 consists of 2D puckered layers made up of Ag centers and taa - bridges. In addition, all of these compounds are photoluminescent in the solid state with spectra that closely resemble those of the ligand precursor.

  10. HgCdTe Research at FFI: Molecular Beam Epitaxy Growth and Characterization

    NASA Astrophysics Data System (ADS)

    Haakenaasen, R.; Selvig, E.; Tonheim, C. R.; Kongshaug, K. O.; Lorentzen, T.; Trosdahl-Iversen, L.; Andersen, J. B.; Gundersen, P.

    2010-07-01

    This paper presents results from recent work on molecular beam epitaxy growth of HgCdTe at the Norwegian Defence Research Establishment (FFI), including studies of material properties and fabrication of photodiodes and nanostructures. Systematic studies of defect morphology in HgTe and Hg1- x Cd x Te have revealed that there is a minimum in the area covered by defects just below the onset of Te precipitation. The shape and density of microvoids in HgTe can be used to determine the deviation from the optimal growth temperature. This can be further related to the optimal growth temperature of Hg1- x Cd x Te with any Cd mole fraction by thermodynamic calculations. A mechanism for the formation of microvoids and needles has been presented. Photoluminescence (PL) has been used to study layers without doping and with Hg vacancy, Ag, and In doping. Planar photodiodes with high dynamic resistance and good quantum efficiency were fabricated by ion-milling vacancy-doped mid-wave and long-wave infrared layers. Quantum wells (QWs) with good crystallinity and high PL light output have been grown. Surface patterning has been found to enhance light emission from HgCdTe thin-film and QW samples by ˜30%. Single-crystal HgTe and segmented HgTe/Te nanowires have been grown, and the resistivity of the nanowires has been measured by conductive atomic force microscopy (AFM), where the AFM tip has been used as a mobile electrode.

  11. Multilayered (Hg,Cd)Te infrared detector

    NASA Technical Reports Server (NTRS)

    Rae, W. G.

    1977-01-01

    Multilayered mercury-cadmium telluride photoconductive detectors were developed which are capable of providing individual coverage of three separate spectral wavelength bands without the use of beam splitters. The multilayered "three-color" detector on a single dewar takes the place of three separate detector/filter/dewar units and enables simpler and more reliable mechanical and optical designs for multispectral scanners and radiometers. Wavelength channel design goals (in micrometers) were: 10.1 to 11.0, 11.0 to 12.0, and 13.0. Detectivity for all channels was 1 x 10 to the 10th power cm-Hz 1/2/Watt. A problem occurred in finding an epoxy layer which had good infrared transmission properties and which also was chemically and mechanically compatible with HgCdTe processing techniques. Data on 6 candidate bonding materials are surveyed and discussed.

  12. Regional atmospheric deposition patterns of Ag, As, Bi, Cd, Hg, Mo, Sb and Tl in a 188,000 km 2 area in the European arctic as displayed by terrestrial moss samples-long-range atmospheric transport vs local impact

    NASA Astrophysics Data System (ADS)

    Reimann, Clemens; De Caritat, Patrice; Halleraker, Jo H.; Finne, Tor Erik; Boyd, Rognvald; Jæger, Øystein; Volden, Tore; Kashulina, Galina; Bogatyrev, Igor; Chekushin, Viktor; Pavlov, Vladimir; Äyräs, Matti; Räisänen, Marja Liisa; Niskavaara, Heikki

    The regional atmospheric deposition patterns of Ag, As, Bi, Cd, Hg, Mo, Sb and Tl have been mapped in a 188,000 km2 area of the European Arctic (N Finland, N Norway, NW Russia) using the moss technique. The Russian nickel mining and smelting industry (Nikel and Zapoljarnij (Pechenganikel) and Monchegorsk (Severonikel)) in the eastern part of the survey area represents two of the largest point sources for S0 2 and metal emissions on a world wide basis. In contrast, parts of northern Finland and northern Norway represent still some of the most pristine areas in Europe. The terrestrial mosses Hylocomium splendens and Pleurozium schreberi were used as monitors of airborne deposition. Samples in all three countries were collected during the summer of 1995 and analysed in one laboratory using ICP-MS. Maps for most elements clearly show elevated element concentrations near the industrial sites and delineate the extent of contamination. Pollution follows the main wind and topographical directions in the area (N-S). The gradients of deposition are rather steep. Background levels for all the elements are reached within 150-200 km from the industrial plants. The relative importance of long-range atmospheric transport of air pollutants from industrial point sources on the world wide increase of heavy metals observed in the atmosphere is thus debatable for many elements. Increasing population and traffic density, accompanied by increasing local dust levels, may play a much more important role than industrial emissions. The regional distribution patterns as displayed in the maps show some striking differences between the elements. The regional distribution of Hg and TI in the survey area is completely dominated by sources other than industry.

  13. Cd and Hg ions stimulate cell membrane potassium conductance

    SciTech Connect

    Jungwirth, A.; Paulmichl, M.; Lang, F. )

    1989-02-09

    Intracellular microelectrodes have been applied to study the effect of cadmium (Cd) and mercury (Hg) ions on cultured renal epitheloid Madin Darby Canine Kidney (MDCK) cells. Within 10 seconds Cd and within 50 seconds Hg hyperpolarize the cell membrane from - 53 {plus minus} 1 mV to - 68 {plus minus} 1 mV and - 67 {plus minus} 1 mV, resp., increase the potassium selectivity of the cell membrane (tk) from 0.33 {plus minus} 0.02 to 0.64 {plus minus} 0.03 and 0.77 {plus minus} 0.02, resp., and reduce the apparent cell membrane resistance from 40 {plus minus} 2 MOhm to 27 {plus minus} 2 MOhm and 22 {plus minus} 2 MOhm, resp.. Thus, both, Cd and Hg hyperpolarize the cell membrane by enhancement of the potassium conductance. The concentration required to elicit half maximal hyperpolarization is some 400 nmol/1 for either, Cd or Hg. Barium (1 mmol/1) depolarizes the cell membrane to - 34 {plus minus} 1 mV and virtually abolishes tk in the absence of Cd and Hg. In the presence of barium Cd leads to a transient, Hg to a sustained reappearance of tk and hyperpolarization. Thus, the Cd induced potassium conductance is blocked by barium with delay, the Hg induced potassium conductance is insensitive to barium. Quinidine (1 mmol/1) depolarizes the cell membrane to - 3 {plus minus}1 mV and abolishes the effect of both, Cd and Hg. In the nominal absence of extracellular calcium Cd leads to transient, Hg to sustained increase of tk and hyperpolarization of the cell membrane. In conclusion, both, CD and Hg at the low concentrations encountered during Cd and Hg intoxication enhance potassium conductance of MDCK cell membranes. However, the channels activated apparently differ.

  14. Hydrothermal single-crystal growth in the systems Ag/Hg/X/O (X = VV, AsV): crystal structures of (Ag3Hg)VO4, (Ag2Hg2)3(VO4)4, and (Ag2Hg2)2(HgO2)(AsO4)2 with the unusual tetrahedral cluster cations (Ag3Hg)3+ and (Ag2Hg2)4+ and crystal structure of AgHgVO4.

    PubMed

    Weil, Matthias; Tillmanns, Ekkehart; Pushcharovsky, Dmitry Yu

    2005-03-01

    Single crystals of (Ag3Hg)VO4 (I), (Ag2Hg2)3(VO4)4 (II), AgHgVO4 (III), and (Ag2Hg2)2(HgO2)(AsO4)2 (IV) were grown under hydrothermal conditions (250 degrees C, 5 d) from starting mixtures of elementary mercury, silver nitrate, ammonium vanadate, and disodium hydrogenarsenate, respectively. All crystal structures were determined from X-ray diffraction data, and their chemical compositions were confirmed by electron microprobe analysis. I crystallizes in the tillmannsite structure, whereas II-IV adopt new structure types: (I) I4, Z = 2, a = 7.7095(2) A, c = 4.6714(2) A, 730 structure factors, 24 parameters, R[F2 > 2sigma(F2)] = 0.0365; (II) I42d, Z = 4, a = 12.6295(13) A, c = 12.566(3) A, 1524 structure factors, 55 parameters, R[F2 > 2sigma(F2)] = 0.0508; (III) C2, Z = 4, a = 9.9407(18) A, b = 5.5730(8) A, c = 7.1210(19) A, beta = 94.561(10) degrees , 1129 structure factors, 48 parameters, R[F2 > 2sigma(F2)] = 0.0358; (IV) P31c, Z = 2, a = 6.0261(9) A, c = 21.577(4) A, 1362 structure factors, 52 parameters, R[F2 > 2sigma(F2)] = 0.0477. The most striking structural features of I, II, and IV are the formation of tetrahedral cluster cations (Ag3Hg)3+ and (Ag2Hg2)4+, respectively, built of statistically distributed Ag and Hg atoms with a metal-metal distance of about 2.72 A. The electronic structure of these clusters can formally be considered as two-electron-four-center bonding. The crystal structure of III differs from the protrusive structure types insofar as silver and mercury are located on distinct crystallographic sites without a notable metal-metal interaction >3.55 A. All crystal structures are completed by tetrahedral oxo anions XO4(3-) (X = VV, AsV) and for IV additionally by a mercurate group, HgO2(2-).

  15. Transient and diffusion analysis of HgCdTe

    NASA Technical Reports Server (NTRS)

    Clayton, J. C.

    1982-01-01

    Solute redistribution during directional solidification of HgCdTe is addressed. Both one-dimensional and two-dimensional models for solute redistribution are treated and model results compared to experiment. The central problem studied is the cause of radial inhomogeneities found in directionally solidified HgCdTe. A large scale gravity-driven interface instability, termed shape instability, is postulated to be the cause of radial inhomogeneities. Recommendations for future work, along with appropriate computer programs, are included.

  16. Dislocation reduction in HgCdTe grown on CdTe/Si

    NASA Astrophysics Data System (ADS)

    Wijewarnasuriya, Priyalal S.

    2016-05-01

    Bulk-grown CdZnTe (Zn = 3%) substrates are the natural choice for HgCdTe epitaxy since it is lattice matched to long wave LW-HgCdTe alloy. However, lack of large area CdZnTe substrates, high production costs, and more importantly, the difference in thermal expansion coefficients between CdZnTe and silicon Read out Integrated Circuits (ROIC) are some of the inherent drawbacks of CdZnTe substrates. Consequently, Hg1-xCdxTe detectors fabricated on silicon substrates are an attractive alternative. Recent developments in the molecular beam epitaxy (MBE) buffer layer growth technology on Si substrates has revolutionized the HgCdTe research and offered a new dimension to HgCdTe-based IR technology. Si substrates provide advantages in terms of relatively large area (3 to 6-inch diameter is easily obtained) compared to CZT substrate materials, durability during processing, and reliability to thermal cycling. Innovations in Si-based composite substrates made it possible to fabricate very large-format IR arrays that offer higher resolution, low-cost arrays and more dies per wafer. Between Si substrates and HgCdTe has large lattice mismatch of 19%. This leads to dislocation densities of low-107 cm-2 for optimal growth of HgCdTe on silicon-based substrates as compared to the mid-104 cm-2 dislocation density of HgCdTe grown on CdZnTe. This paper present dislocation reduction by two orders of magnitude using thermal cycle anneal under Hg environment on HgCdTe grown on Si substrates and as well as defect reduction in Cd(Se)Te buffer layers grown on Si Substrates.

  17. MBE HgCdTe for HDVIP Devices: Horizontal Integration in the US HgCdTe FPA Industry

    NASA Astrophysics Data System (ADS)

    Aqariden, F.; Elsworth, J.; Zhao, J.; Grein, C. H.; Sivananthan, S.

    2012-10-01

    Molecular beam epitaxy (MBE) growth of HgCdTe offers the possibility of fabricating multilayer device structures with an almost unlimited choice of infrared sensor designs for focal-plane array (FPA) fabrication. HgCdTe offers two major advantages that explain its dominance in the infrared photon detector marketplace. The thermal generation rate per unit volume of the material is lower and the quantum efficiency for photon absorption in the infrared is higher in HgCdTe than in any competing material—it yields devices with quantum efficiencies as high as 0.99. Recently, EPIR Technologies and DRS Infrared Technologies agreed to collaborate and examine: (i) the feasibility of employing MBE HgCdTe in the fabrication of high-density vertically interconnected photodiodes (HDVIPs), which are usually fabricated with liquid-phase epitaxy material, and (ii) the potential benefits of horizontal integration, with EPIR supplying the MBE materials to DRS for device and array fabrication. The team designed and developed passivation-absorber-passivation structures that are heavily used by DRS. This paper provides an overview of the characteristics of HDVIP devices and arrays fabricated from MBE HgCdTe and the anticipated advantages of horizontal integration in the industry. Material growth, device fabrication, and test results are presented.

  18. Raman spectroscopic investigations of Hg-Cd-Te melts

    NASA Technical Reports Server (NTRS)

    Morrobel-Sosa, Anny

    1987-01-01

    Raman scattering measurements are reported for a series of Hg sub1-xCd subxTe (with x less than or =0.2) materials from 295 K (room temperature) to 1126K (up to and above their liquidus temperatures), and for Hg sub1-xCd subxTe (x=0.3) at 285K. The samples were contained in high-temperature optically-flat fused silica cell. Variable temperature measurements were effected in a three-zone, high-temperature furnace equipped with optical windows, and monitored externally by three independently programmable temperature controllers. All studies were made in the backscattering geometry using the 5145 A line of an Ar+ ion laser, with incident power less than 250 mW, as the excitiation source. An intensity enhancement is observed for a mode in each of the compositions studied. The frequency of this mode varies with composition, 142/cm for HgTe, and 128/cm for both the Hg sub1-xCd subxTe (x=0.053 and 0.204) samples. In addition, a shift to lower frequency as a function of temperature is observed in all samples. This shift is most prominent for the x=0.053 sample. The temperature dependence of these modes as the liquidus temperatures are achieved and surpassed for these samples is presented as being associated with a structural transition in the Hg-rich compositions of the Hg sub1-xCd subxTe series. To our knowledge, this is the first reported study of Raman scattering by phonons in the melts of these materials.

  19. RF magnetron sputtering deposition of CdTe passivation on HgCdTe

    NASA Astrophysics Data System (ADS)

    Rutkowski, Jaroslaw; Adamiec, Krzysztof; Rogalski, Antoni

    1998-04-01

    In this study, we report the RF magnetron sputtering growth and characterization of CdTe passivant on bulk n-type HgCdTe. Our investigations include the HgCdTe surface preparation and in-situ pretreatment, deposition-induced surface damage, interface charge, CdTe film stoichiometry, and thermal stability. The metal-insulator-semiconductor test structures are processed and their electrical properties are measured by capacitance-voltage characteristics. The heterostructures are also characterized by reflectance measurement. In order to investigate the passivation properties of CdTe/HgCdTe heterostructures, we have modeled the band diagram of abrupt CdTe/HgCdTe heterojunction. The effect of sputtering growth condition parameters is also reported. The sputtering CdTe layers, exhibit excellent dielectric, insulating and mechano- chemical properties, as well as interface properties. The interfaces are characterized by slight accumulation and a small hysteresis. A carefully controlled growth process and surface pretreatment tailored to the specific material are required in order to obtain near flat band conditions on n- type materials. Additional informations on surface limitations are obtained from analyzing the I-V characteristics of photodiodes with metal gates covering the p-n junction surface location.

  20. Enhanced thermoelectric performance of CdO : Ag nanocomposites.

    PubMed

    Gao, Linjie; Wang, Shufang; Liu, Ran; Zha, Xinyu; Sun, Niefeng; Wang, Shujie; Wang, Jianglong; Fu, Guangsheng

    2016-07-26

    CdO : Ag nanocomposites with metallic Ag nanoparticles embedded in the polycrystalline CdO matrix were synthesized by the solid-state reaction method. The addition of Ag led to increased grain boundaries of CdO and created numerous CdO/Ag interfaces. By incorporating Ag into the CdO matrix, the power factor was increased which was probably due to the carrier energy filtering effect induced by the enhanced energy-dependent scattering of electrons. In addition, reduced thermal conductivity was also achieved by stronger phonon scattering from grain boundaries, CdO/Ag interfaces and Ag nanoparticles. These concomitant effects resulted in enhanced ZT values for all CdO : Ag nanocomposites, demonstrating that the strategy of introducing metallic Ag nanoparticles into the CdO host was very effective in optimizing the thermoelectric performance. PMID:27411573

  1. Impurity doping of HgTe--CdTe superlattices during growth by molecular-beam epitaxy

    SciTech Connect

    Wroge, M.L.; Peterman, D.J.; Feldman, B.J.; Morris, B.J.; Leopold, D.J.; Broerman, J.G.

    1989-03-01

    We demonstrate the use of In and Ag as n- and p-type dopants, respectively, to controllably dope (100)-oriented HgTe--CdTe superlattices during molecular-beam epitaxial (MBE) growth. When normalized by the superlattice growth rate, the low-temperature Hall-carrier concentrations of both In- and Ag-doped superlattices are shown to have an exponential dependence on the respective effusion-cell temperatures in the electron and hole concentration ranges of approx.10/sup 16/ to 10/sup 18/ cm/sup -3/ . The upper limit on the diffusion coefficient for In at the low MBE growth temperature of approx.160 /sup 0/C is determined to be 5 x 10/sup -15/ cm/sup 2/ /s by use of secondary-ion mass spectrometry. Hall-effect and current--voltage measurements verify that the combination of In and Ag doping allows the formation of p--n electrical junctions. These results provide the first evidence of p--n junction formation in a HgTe--CdTe superlattice.

  2. HgCdTe 256x256 NWIR FPA

    NASA Technical Reports Server (NTRS)

    Vural, Kadri; Blessinger, Michael; Chen, Jenkon; Kleinhans, William

    1989-01-01

    Researchers developed a HgCdTe 256x256 focal plane array (FPA) which operates in the 1 to 5 micron band. This is presently the largest demonstrated HgCdTe FPA. The detector material is HgCdTe on sapphire (PACE-1 technology) which has a low thermal expansion mismatch with silicon. The multiplexer is a CMOS FET-switch device processed through a commercial silicon foundry. The multiplexer input is direct injection and the charge capacity is about 2 times 10 to the 7th power electrons. The kTC limited read noise is 400 electrons. Researchers demonstrated high background imaging using the device. The broadband quantum efficiency is measured to be 59 percent. Dark currents less than 0.1 pA were measured at 77 K for detectors processed on PACE-1 material with 4.9 microns cutoff. The dark currents decrease as the temperature is lowered, and researchers are presently studying the T less than 77 K characteristics. The interconnect yield is greater than 95 percent. The devices are available for astronomical applications.

  3. Defect chemistry and characterization of (Hg, Cd)Te

    NASA Technical Reports Server (NTRS)

    Vydyanath, H. R.

    1981-01-01

    Single crystal samples of phosphorus doped Hg sub 0.8 Cd sub 0.2 Te were anneald at temperatures varying from 450 C to 600 C in various Hg atmospheres. The samples were quenched to room temperature from the annealing temperatures. Hall effect and mobility measurements were performed at 77 K on all these samples. The results indicate the crystals to be p type for a total phosphorus concentration of 10 to the 19th power/cu cm in all the samples. The hole concentration at 77 K increases with increasing Hg pressures at 450 C and 500 C contrary to the observation in undoped crystals. Also, at low Hg pressures the concentration of holes in the phosphorus doped crystals is lower than in the undoped crystals. The hole concentration in all the samples is lower than the intrinsic carrier concentration at the annealing temperatures. The hole mobility in the doped crystals is similar to that in the undoped crystals. A defect model according to which phosphorus behaves as a single acceptor interstitially, occupying Te lattice sites while it acts as a single donor occupying Hg lattice sites was established. Equilibrum constants established for the incorporation of all the phosphorus species explain the experimental results

  4. 640 X 480 Pace HgCdTe FPA

    NASA Astrophysics Data System (ADS)

    Kozlowski, Lester J.; Bailey, Robert B.; Cabelli, Scott A.; Cooper, Donald E.; McComas, Gail D.; Vural, Kadri; Tennant, William E.

    1992-12-01

    A hybrid HgCdTe 640 X 480 infrared (IR) focal plane array (FPA) that meets the sensitivity, resolution, and field-of-view requirements of high-performance medium wavelength infrared (MWIR) imaging systems has been developed. The key technology making this large, high sensitivity device producible is the epitaxial growth of HgCdTe on a CdTe-buffered, sapphire substrate (referred to as PACE, for Producible Alternative to CdTe for Epitaxy; PACE-I refers to sapphire). The device offers TV resolution with excellent sensitivity at temperatures below 120 K. Mean NE(Delta) T as low as 13 mK has been achieved at operating temperatures < 130 K, which is about an order of magnitude better than has been achieved with PtSi 640 X 480 FPAs. In addition, the latter require cooling to

  5. Distribution and excretion of Cd, Hg, methyl-Hg and ZS in the predatory beetle Pterostichus niger (Coleoptera: Carabidae)

    SciTech Connect

    Lindqvist, L.; Block, M.; Tjaelve, H.

    1995-07-01

    Excretion and distribution of cadmium (Cd), and mercury (Hg), methylmercury (methyl-Hg), and zinc (Zn) were studied in the predatory beetle, Pterostichus niger. Specimens of P. niger were fed with insect larvae containing {sup 109}Cd, {sup 203}Hg, methyl-{sup 203}Hg, or {sup 65}Zn. After ingestion of the larvae, the metal contents in the beetles were measured daily for 30 d by {gamma}-spectrometry. Additional beetles were used for autoradiography 5, 15, and 19 d after ingestion of the metals. Excretion of the metals was fast during an initial interval but occurred thereafter at a slow rate. After 2 weeks, the contents of Cd and inorganic Hg had decreased to approximately 1% of the ingested amounts. For Zn and methyl-Hg, higher levels were retained in the beetles. Thus after 30 d, Zn content was 20% of the ingested amount, whereas for methyl-Hg 60% was retained in the body. Autoradiography showed high levels of all metals in the gut. For methyl-Hg, in contrast to inorganic Hg, there was also an evenly distributed labelling in most body tissues. This labelling was also seen for Zn, although at a lower lever than for methyl-Hg. Cadmium showed a localization in the integument, which was not seen for the other metals. The results show that patterns of uptake and excretion of the examined metals in P. niger vary considerably and that the distribution picture show specific features for the individual metals.

  6. High-Operating-Temperature HgCdTe Avalanche Photodiodes

    NASA Astrophysics Data System (ADS)

    Rothman, J.; Baier, N.; Ballet, P.; Mollard, L.; Fournier, M.; Gout, J. S.; Chamonal, J.-P.

    2009-08-01

    In this communication we report the first results of electro-optical characterization of planar heterostructure HgCdTe avalanche photodiodes (APDs), which enables the operation of APDs at high gain, at low bias, and with low dark current and/or at high operating temperature (HOT). The APD is based on a heterostructure in which the photons are detected in a wide-band-gap layer, and the photoelectrons are amplified in a vertical junction in a confined narrow-gap layer. The dark diffusion current and thermal background sensitivity of the device are limited by using a thin narrow-band-gap amplification layer. In addition, the defect-limited dark current is also expected to be reduced due to the reduced volume of the narrow-band-gap depletion layer. The electro-optical performance was characterized at T = 80 K and T = 200 K for two devices with a nominal thickness of the amplification layer of w = 100 nm and 500 nm, realized in x Cd = 0.3 Hg-vacancy-doped layers grown by molecular-beam epitaxy (MBE). The measurements show an average gain of < M< = 10 at a reverse bias of 5 V, which is slightly reduced compared with a conventional APD with x Cd = 0.3. The thermal diffusion current measured at low reverse bias, V b = 0.1 V, and at T = 200 K is about 0.1 mA/cm2 to 0.3 mA/cm2, which is a factor of 50 lower than standard x Cd = 0.3 n-on- p APDs. The quantum efficiency due to absorption in the gain layer is high (QEpeak > 30%), although no antireflecting coating was used, indicating that the device can also be used for high-operating-temperature thermal detection.

  7. Sputter cleaning and dry oxidation of CdTe, HgTe, and Hg 0.8Cd 0.2Te surfaces

    NASA Astrophysics Data System (ADS)

    Solzbach, U.; Richter, H. J.

    1980-07-01

    The analyses of CdTe, HgTe, and Hg 0.8Cd 0.2Te surfaces by XPS and LEED after Ar + sputtering and after the subsequent onset of a dry oxidation are described, and a quantitative evaluation of the XPS spectra is attempted. The results are: Ar + sputtering yields a perfect unreconstructed CdTe surface of stoichiometric composition, whereas the composition of sputtered HgTe and Hg 0.8Cd 0.2Te surfaces generally deviates from the stoichiometry of the respective compound. This deviation is a function of the energy of the Ar ions (1 to 15 keV) and is characterized by an increasing deficit in Hg as the ion energy is raised. The Hg deficit of sputtered Hg 0.8Cd 0.2Te surfaces is substitutionally compensated by an equivalent increase in Cd, and due to this substitution the resulting surfaces are sufficiently ordered to display a distinct LEED pattern. The oxidation of sputtered CdTe, HgTe, and Hg 0.8Cd 0.2Te surfaces in an O 2 atmosphere is an extremely slow process. Therefore, the surfaces to be oxidized were additionally exposed to UV radiation (low pressure mercury lamp), and due to UV generated ozone as an oxidizing agent ultrathin native oxide layers of up to 15 Å thickness were readily obtained. The predominant constituents of these native oxide layers on Hg 0.8Cd 0.2Te are concluded to be CdTeO 3 and TeO 2.

  8. The effect of electrode process on properties of HgCdTe detectors

    NASA Astrophysics Data System (ADS)

    Wang, Nili; Liu, Xiang-yang; Lan, Tian-yi; Liu, Shi-jia; Zhao, Shui-ping; Zhou, Qing; Li, Xiangyang

    2014-11-01

    Performance of HgCdTe devices was limited by many factors such as materials and techniques, etc. And the electrical characteristics of electrode contacts on HgCdTe played important roles - Because Ar Ion Beam Etching could make the conductivity type conversion of p-type HgCdTe material, it was used to obtain n-type electrode area on the slight-p type HgCdTe material. Variable magnetic field Hall measurements were performed on n-type and slight p-type HgCdTe material before and after Ar Ion Beam Etching at 77 K. The mobility spectrum analysis (MSA) technique was employed in this paper to obtain the electrical parameter of HgCdTe. Comparing the electrical parameters of HgCdTe before and after etching, we knew that Ar Ion etching formed high doping concentration n-type area on slight p-type HgCdTe. The minority carrier lifetime of HgCdTe was studied using the photoconductive decay technique. By measuring the minority carrier lifetime of the same HgCdTe material with or without n-type electrode, it was found that the minority carrier lifetime of slight p-type HgCdTe with n-type electrode was higher than HgCdTe that was without n-type electrode at low temperature. The results showed that the n-type electrode could improve the minority carrier lifetime of slight p-type HgCdTe. In addition, by changing the distance of the n-type electrode area to the photosensitive area, it was researched that the impact of n-type electrode area on the device performance. With the decrease of distance, the device performance improved. It was proved that n-type electrode areas also could improve the performance by device fabrication.

  9. Advances in HgCdTe APDs and LADAR Receivers

    NASA Technical Reports Server (NTRS)

    Bailey, Steven; McKeag, William; Wang, Jinxue; Jack, Michael; Amzajerdian, Farzin

    2010-01-01

    Raytheon is developing NIR sensor chip assemblies (SCAs) for scanning and staring 3D LADAR systems. High sensitivity is obtained by integrating high performance detectors with gain i.e. APDs with very low noise Readout Integrated Circuits. Unique aspects of these designs include: independent acquisition (non-gated) of pulse returns, multiple pulse returns with both time and intensity reported to enable full 3D reconstruction of the image. Recent breakthrough in device design has resulted in HgCdTe APDs operating at 300K with essentially no excess noise to gains in excess of 100, low NEP <1nW and GHz bandwidths and have demonstrated linear mode photon counting. SCAs utilizing these high performance APDs have been integrated and demonstrated excellent spatial and range resolution enabling detailed 3D imagery both at short range and long ranges. In this presentation we will review progress in high resolution scanning, staring and ultra-high sensitivity photon counting LADAR sensors.

  10. Can graphene make better HgCdTe infrared detectors?

    PubMed Central

    2011-01-01

    We develop a simple and low-cost technique based on chemical vapor deposition from which large-size graphene films with 5-10 graphene layers can be produced reliably and the graphene films can be transferred easily onto HgCdTe (MCT) thin wafers at room temperature. The proposed technique does not cause any thermal and mechanical damages to the MCT wafers. It is found that the averaged light transmittance of the graphene film on MCT thin wafer is about 80% in the mid-infrared bandwidth at room temperature and 77 K. Moreover, we find that the electrical conductance of the graphene film on the MCT substrate is about 25 times larger than that of the MCT substrate at room temperature and 77 K. These experimental findings suggest that, from a physics point of view, graphene can be utilized as transparent electrodes as a replacement for metal electrodes while producing better and cheaper MCT infrared detectors. PMID:21711816

  11. Properties of insulator interfaces with p-HgCdTe

    NASA Technical Reports Server (NTRS)

    Schacham, Samuel E.; Finkman, Eliezer

    1990-01-01

    Heat treatment at 70 C of low carrier concentration p-type HgCdTe samples (p sub o = 8 x 10 exp 14/cm) generates an inverted surface layer. A two day anneal process below 95 C did not affect the Hall coefficient, whereas an almost complete recovery was obtained by annealing at 120 C. While bulk electron mobility, obtained from PEM data, remained high (about 9 x 10 exp 4 sq cm/V s at 77 K), surface mobility is lower by more than an order of magnitude. Surface recombination velocity indicates a continuous improvement with increased temperature, and the activation energy remains equal to the vacancies energy level. The proposed mechanism is that of positive changes in the sulfide migrating towards the interface and generating an image inversion layer.

  12. High performance SWIR HgCdTe detector arrays

    NASA Astrophysics Data System (ADS)

    Bubulac, L. O.; Tennant, W. E.; Pasko, J. G.; Kozlowski, L. J.; Zandian, M.; Motamedi, M. E.; de Wames, R. E.; Bajaj, J.; Nayar, N.; McLevige, W. V.; Gluck, N. S.; Melendes, R.; Cooper, D. E.; Edwall, D. D.; Arias, J. M.; Hall, R.; D'Souza, A. I.

    1997-06-01

    Short wave infrared (SWIR) devices have been fabricated using Rockwell’s double layer planar heterostructure (DLPH) architecture with arsenic-ion implanted junctions. Molecular beam epitaxially grown HgCdTe/CdZnTe multilayer structures allowed the thin, tailored device geometries (typical active layer thickness was ˜3.5 µm and cap layer thickness was ˜0.4 µm) to be grown. A planar-mesa geometry that preserved the passivation advantages of the DLPH structure with enhanced optical collection improved the performance. Test detectors showed Band 7 detectors performing near the radiative limit (˜3-5X below theory). Band 5 detector performance was ˜4-50X lower than radiative limited performance, apparently due to Shockley-Hall-Read recombination. We have fabricated SWIR HgCdTe 256 × 12 × 2 arrays of 45 um × 45 µm detector on 45 µm × 60 µm centers and with cutoff wavelength which allows coverage of the Landsat Band 5 (1.5-1.75 µm) and Landsat Band 7 (2.08-2.35 µm) spectral regions. The hybridizable arrays have four subarrays, each having a different detector architecture. One of the Band 7 hybrids has demonstrated performance approaching the radiative theoretical limit for temperatures from 250 to 295K, consistent with test results. D* performance at 250K of the best subarray was high, with an operability of ˜99% at 1012 cm Hz1/2/W at a few mV bias. We have observed 1/f noise below 8E-17 AHz 1/2 at 1 Hz. Also for Band 7 test structures, Ge thin film diffractive microlenses fabricated directly on the back side of the CdZnTe substrate showed the ability to increase the effective collection area of small (nominally <20 µm µm) planar-mesa diodes to the microlens size of 48 urn. Using microlenses allows array performance to exceed 1-D theory up to a factor of 5.

  13. Progress in MOCVD growth of HgCdTe epilayers for HOT infrared detectors

    NASA Astrophysics Data System (ADS)

    Kebłowski, A.; Gawron, W.; Martyniuk, P.; Stepień, D.; Kolwas, K.; Piotrowski, J.; Madejczyk, P.; Kopytko, M.; Piotrowski, A.; Rogalski, A.

    2016-05-01

    In this paper we present progress in MOCVD growth of (100) HgCdTe epilayers achieved recently at the Institute of Applied Physics, Military University of Technology and Vigo System S.A. It is shown that MOCVD technology is an excellent tool in fabrication of different HgCdTe detector structures with a wide range of composition, donor/acceptor doping and without post grown annealing. Particular progress has been achieved in the growth of (100) HgCdTe epilayers for long wavelength infrared photoconductors operated in HOT conditions. The (100) HgCdTe photoconductor optimized for 13-μm attain detectivity equal to 6.5x109 Jones and therefore outperform its (111) counterpart. The paper also presents technological progress in fabrication of MOCVD-grown (111) HgCdTe barrier detectors. The barrier device performance is comparable with state-of-the-art of HgCdTe photodiodes. The detectivity of HgCdTe detectors is close to the value marked HgCdTe photodiodes. Dark current densities are close to the values given by "Rule 07".

  14. Oxidase-like mimic of Ag@Ag3PO4 microcubes as a smart probe for ultrasensitive and selective Hg(2+) detection.

    PubMed

    Chai, Dong-Feng; Ma, Zhuo; Qiu, Yunfeng; Lv, Yu-Guang; Liu, Hong; Song, Chao-Yu; Gao, Guang-Gang

    2016-02-21

    An oxidase-like mimic system based on facilely synthesized Ag@Ag3PO4 microcubes (Ag@Ag3PO4MCs) was designed and utilized to detect mercury ions with high selectivity and ultrasensitivity. Ag@Ag3PO4MCs with an average size of ca. 1.6 μm were synthesized by the reaction of [Ag(NH3)2](+) complex and Na2HPO4 and subsequent photoreduction under ultraviolet light. The as-prepared Ag@Ag3PO4MCs can effectively catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) and o-phenylenediamine (OPD) in the presence of dissolved oxygen in slightly acidic solution, exhibiting oxidase-like activities rather than peroxidase-like activity. Interestingly, the introduction of Ag nanoparticles (AgNPs) on the surfaces of Ag3PO4MCs can dramatically enhance the oxidase-like activities due to a synergistic effect between AgNPs and Ag3PO4MCs, as evidenced by the faster oxidation speed of TMB and OPD than that of native Ag3PO4MCs in the presence of dissolved oxygen. The enzyme kinetics can be well-explained by the Michaelis-Menten equation. As "poisoning" inhibitor, Hg(2+) ions can inhibit the enzyme reaction catalyzed by Ag3PO4MCs or Ag@Ag3PO4MCs. On the basis of this effect, a colorimetric Hg(2+) sensor was developed by the enzyme inhibition reaction of Ag3PO4MCs or Ag@Ag3PO4MCs. The excellent specific interaction of Hg-Ag or Hg(2+)-Ag(+) provides high selectivity for Hg(2+) over interfering metal ions. Meanwhile, the sensitivity of this sensor to Hg(2+) is extremely excellent with a limit of detection as low as 0.253 nM for Ag@Ag3PO4MCs. Considering the advantages of low detection limit, low cost, facile preparation, and visualization, the colorimetric Ag@Ag3PO4MCs sensor shows high promise for the testing of Hg(2+) in water samples. PMID:26763181

  15. Heavy metal tolerance (Cr, Ag AND Hg) in bacteria isolated from sewage

    PubMed Central

    Lima de Silva, Agostinho A.; de Carvalho, Márcia A. Ribeiro; de Souza, Sérgio A. L; Dias, Patrícia M. Teixeira; da Silva Filho, Renato G.; de Meirelles Saramago, Carmen S.; de Melo Bento, Cleonice A.; Hofer, Ernesto

    2012-01-01

    Samples of sewage from a university hospital and a chemistry technical school were analysed for the percentage of bacterial tolerance to chromium (Cr), silver (Ag) and mercury (Hg). Additionally, we investigated the effect of these metals on pigmentation and on some enzymatic activities of the metal tolerant strains isolated, as well as antimicrobial resistance in some metal tolerant Enterobacteriaceae strains. Tolerance to Cr was observed mainly in Gram positive bacteria while in the case of Ag and Hg the tolerant bacteria were predominately Gram negative. Hg was the metal for which the percentage of tolerance was significantly higher, especially in samples from the hospital sewage (4.1%). Mercury also had the most discernible effect on color of the colonies. Considering the effect of metals on the respiratory enzymes, one strain of Ag-tolerant Bacillus sp. and one of Hg-tolerant P. aeruginosa were unable to produce oxidase in the presence of Ag and Hg, respectively, while the expression of gelatinase was largely inhibited in various Gram negative strains (66% by Cr). Drug resistance in Hg-tolerant Enterobacteriaceae strains isolated from the university hospital sewage was greater than 80%, with prevalence of multiple resistance, while the Ag-tolerant strains from the same source showed about 34% of resistance, with the predominance of mono-resistance. Our results showed that, despite the ability of metal tolerant strains to survive and grow in the presence of these elements, the interactions with these metals may result in metabolic or phisiological changes in this group of bacteria. PMID:24031994

  16. Heavy metal tolerance (Cr, Ag AND Hg) in bacteria isolated from sewage.

    PubMed

    Lima de Silva, Agostinho A; de Carvalho, Márcia A Ribeiro; de Souza, Sérgio A L; Dias, Patrícia M Teixeira; da Silva Filho, Renato G; de Meirelles Saramago, Carmen S; de Melo Bento, Cleonice A; Hofer, Ernesto

    2012-10-01

    Samples of sewage from a university hospital and a chemistry technical school were analysed for the percentage of bacterial tolerance to chromium (Cr), silver (Ag) and mercury (Hg). Additionally, we investigated the effect of these metals on pigmentation and on some enzymatic activities of the metal tolerant strains isolated, as well as antimicrobial resistance in some metal tolerant Enterobacteriaceae strains. Tolerance to Cr was observed mainly in Gram positive bacteria while in the case of Ag and Hg the tolerant bacteria were predominately Gram negative. Hg was the metal for which the percentage of tolerance was significantly higher, especially in samples from the hospital sewage (4.1%). Mercury also had the most discernible effect on color of the colonies. Considering the effect of metals on the respiratory enzymes, one strain of Ag-tolerant Bacillus sp. and one of Hg-tolerant P. aeruginosa were unable to produce oxidase in the presence of Ag and Hg, respectively, while the expression of gelatinase was largely inhibited in various Gram negative strains (66% by Cr). Drug resistance in Hg-tolerant Enterobacteriaceae strains isolated from the university hospital sewage was greater than 80%, with prevalence of multiple resistance, while the Ag-tolerant strains from the same source showed about 34% of resistance, with the predominance of mono-resistance. Our results showed that, despite the ability of metal tolerant strains to survive and grow in the presence of these elements, the interactions with these metals may result in metabolic or phisiological changes in this group of bacteria.

  17. Mode of incorporation of phosphorus in Hg(0.8)Cd(0.2)Te

    NASA Technical Reports Server (NTRS)

    Vydyanath, H. R.; Abbott, R. C.; Nelson, D. A.

    1983-01-01

    Selim and Kroeger (1977) have studied the mode of incorporation of phosphorus in CdTe. According to their findings, phosphorus behaves amphoterically in CdTe acting as an acceptor interstitially and on Te lattice sites, and as a triple donor on Cd lattice sites. The present investigation is concerned with the role of phosphorus in Hg(0.8)Cd(0.2)Te, taking into account Hall-effect and mobility measurements on phosphorus-doped crystals quenched from a temperature in the range from 450 to 600 C subsequent to anneals in different partial pressures of Hg. It is found that the behavior of phosphorus in Hg(0.8)Cd(0.2)Te is similar to that established for CdTe, except that all the electrically active phosphorus defect centers in Hg(0.8)Cd(0.2)Te appear to be only singly ionized. At low Hg pressure, phosphorus is incorporated as a single donor occupying Hg lattice sites, and at high Hg pressure, as a single acceptor on interstitial sites and Te lattice sites.

  18. Ohmic Contact of Au/Mo on Hg1- x Cd x Te

    NASA Astrophysics Data System (ADS)

    Liu, Dan; Lin, Chun; Zhou, Songmin; Hu, Xiaoning

    2016-06-01

    The contact resistance between Au/Mo and HgCdTe was investigated. The influence of thermal annealing on metal-semiconductor contact on short and middle-wavelength HgCdTe is also discussed in this paper. The specific contact resistance ρ c (300 K, 80 K) of Au/Mo/HgCdTe was measured by the transmission line method. Good ohmic contacts can be formed with Au/Mo on long-wavelength infrared p-HgCdTe ( x = 0.23) with a low specific contact resistivity of 3.78E-04 Ωcm2 measured at 80 K. For the mid-wavelength infrared p-HgCdTe ( x = 0.30), the metal-semiconductor contact is ohmic, and the minimum specific contact resistivity of 7.40E-04 Ωcm2 is obtained after annealing at 120°C/10 min. The as-deposited contact between Au/Mo and the short-wavelength infrared HgCdTe ( x = 0.47) shows non-ohmic behavior. After annealing at 120°C/5 min, although the contact behavior is still a Schottky contact, the contact resistance decreases. For the n-HgCdTe ( x = 0.27), the metal-semiconductor contact is ohmic with a specific contact resistivity of 5.70E-04 Ωcm2 at 80 K.

  19. Mode of incorporation of phosphorus in Hg(0.8)Cd(0.2)Te

    NASA Astrophysics Data System (ADS)

    Vydyanath, H. R.; Abbott, R. C.; Nelson, D. A.

    1983-03-01

    Selim and Kroeger (1977) have studied the mode of incorporation of phosphorus in CdTe. According to their findings, phosphorus behaves amphoterically in CdTe acting as an acceptor interstitially and on Te lattice sites, and as a triple donor on Cd lattice sites. The present investigation is concerned with the role of phosphorus in Hg(0.8)Cd(0.2)Te, taking into account Hall-effect and mobility measurements on phosphorus-doped crystals quenched from a temperature in the range from 450 to 600 C subsequent to anneals in different partial pressures of Hg. It is found that the behavior of phosphorus in Hg(0.8)Cd(0.2)Te is similar to that established for CdTe, except that all the electrically active phosphorus defect centers in Hg(0.8)Cd(0.2)Te appear to be only singly ionized. At low Hg pressure, phosphorus is incorporated as a single donor occupying Hg lattice sites, and at high Hg pressure, as a single acceptor on interstitial sites and Te lattice sites.

  20. HgTe-CdTe-InSb heterostructures by molecular beam epitaxy

    SciTech Connect

    Ballingall, J.M.; Leopold, D.J.; Peterman, D.J.

    1985-08-01

    HgTe-CdTe heterostructures have been grown by molecular beam epitaxy on (100) InSb substrates. Separate elemental Hg and Te beams were used for the HgTe growth at a substrate temperature of 160 C. X-ray diffraction measurements indicate that thin epitaxial layers are of high crystalline quality. Secondary-ion mass spectroscopy measurements show substantial In and Sb diffusion into the epitaxial layers with a concentration enhancement at the HgTe-CdTe interface. 9 references.

  1. Large format MBE HgCdTe on silicon detector development for astronomy

    NASA Astrophysics Data System (ADS)

    Hanold, Brandon J.; Figer, Donald F.; Lee, Joong; Kolb, Kimberly; Marcuson, Iain; Corrales, Elizabeth; Getty, Jonathan; Mears, Lynn

    2015-08-01

    The Center for Detectors at Rochester Institute of Technology and Raytheon Vision Systems (RVS) are leveraging RVS capabilities to produce large format, short-wave infrared HgCdTe focal plane arrays on silicon (Si) substrate wafers. Molecular beam epitaxial (MBE) grown HgCdTe on Si can reduce detector fabrication costs dramatically, while keeping performance competitive with HgCdTe grown on CdZnTe. Reduction in detector costs will alleviate a dominant expense for observational astrophysics telescopes. This paper presents the characterization of 2.5μm cutoff MBE HgCdTe/Si detectors including pre- and post-thinning performance. Detector characteristics presented include dark current, read noise, spectral response, persistence, linearity, crosstalk probability, and analysis of material defects.

  2. Optical study of HgCdTe infrared photodetectors using internal photoemission spectroscopy

    SciTech Connect

    Lao, Yan-Feng; Unil Perera, A. G.; Wijewarnasuriya, Priyalal S.

    2014-03-31

    We report a study of internal photoemission spectroscopy (IPE) applied to a n-type Hg{sub 1−x}Cd{sub x}Te/Hg{sub 1−y}Cd{sub y}Te heterojunction. An exponential line-shape of the absorption tail in HgCdTe is identified by IPE fittings of the near-threshold quantum yield spectra. The reduction of quantum yield (at higher photon energy) below the fitting value is explained as a result of carrier-phonon scatterings. In addition, the obtained bias independence of the IPE threshold indicates a negligible electron barrier at the heterojunction interface.

  3. Lattice defects in semiconducting Hg/1-x/Cd/x/Te alloys. III - Defect structure of undoped Hg0.6Cd0.4Te

    NASA Technical Reports Server (NTRS)

    Vydyanath, H. R.; Donovan, J. D.; Nelson, D. A.

    1981-01-01

    Hall effect measurements were carried out on undoped Hg0.6Cd0.4Te crystals quenched to room temperature subsequent to equilibration at temperatures varying from 450 to 720 C under various partial pressures of Hg. The variation of the hole concentration as a function of the partial pressure of Hg indicates that the native acceptor defects are doubly ionized. Native donor defects are found to be negligible in concentration and the p-type to n-type conversion is shown to be due to residual donors and not due to native donor defects. Thermodynamic constant for the incorporation of the doubly ionized native acceptor defect has been established.

  4. Energy loss rate of a charged particle in HgTe/(HgTe, CdTe) quantum wells

    SciTech Connect

    Chen, Qinjun; Sin Ang, Yee; Wang, Xiaolin; Lewis, R. A.; Zhang, Chao

    2013-11-04

    The energy loss rate (ELR) of a charged particle in a HgTe/(HgTe, CdTe) quantum well is investigated. We consider scattering of a charged particle by the bulk insulating states in this type of topological insulator. It is found that the ELR characteristics due to the intraband excitation have a linear energy dependence while those due to interband excitation depend on the energy exponentially. An interesting quantitative result is that for a large range of the incident energy, the mean inelastic scattering rate is around a few terahertz.

  5. Recent progress in MBE grown HgCdTe materials and devices at UWA

    NASA Astrophysics Data System (ADS)

    Gu, R.; Lei, W.; Antoszewski, J.; Madni, I.; Umana-Menbreno, G.; Faraone, L.

    2016-05-01

    HgCdTe has dominated the high performance end of the IR detector market for decades. At present, the fabrication costs of HgCdTe based advanced infrared devices is relatively high, due to the low yield associated with lattice matched CdZnTe substrates and a complicated cooling system. One approach to ease this problem is to use a cost effective alternative substrate, such as Si or GaAs. Recently, GaSb has emerged as a new alternative with better lattice matching. In addition, implementation of MBE-grown unipolar n-type/barrier/n-type detector structures in the HgCdTe material system has been recently proposed and studied intensively to enhance the detector operating temperature. The unipolar nBn photodetector structure can be used to substantially reduce dark current and noise without impeding photocurrent flow. In this paper, recent progress in MBE growth of HgCdTe infrared material at the University of Western Australia (UWA) is reported, including MBE growth of HgCdTe on GaSb alternative substrates and growth of HgCdTe nBn structures.

  6. Estimation of Thickness and Cadmium Composition Distributions in HgCdTe Focal Plane Arrays

    NASA Astrophysics Data System (ADS)

    Mouzali, S.; Lefebvre, S.; Rommeluère, S.; Ferrec, Y.; Primot, J.

    2016-09-01

    Mercury cadmium telluride (HgCdTe) is one of the most commonly used material systems for infrared detection. The performance of infrared focal-plane arrays (IRFPAs) based on this material is limited by several noise sources. In this paper, we focus on the fixed pattern noise, which is related to disparities between the spectral responses of pixels. In our previous work, we showed that spectral nonuniformities in a HgCdTe IRFPA were caused by inhomogeneities of thickness and cadmium composition in the HgCdTe layer, using an optical description of the pixel structure. We propose to use this bidimensional dependence combined with experimental spectral responses to estimate disparities of thickness and cadmium composition in a specific HgCdTe-based IRFPA. The estimation methods and the resulting maps are presented, highlighting the accuracy of this nondestructive method.

  7. Acceptor states in heteroepitaxial CdHgTe films grown by molecular-beam epitaxy

    SciTech Connect

    Mynbaev, K. D.; Shilyaev, A. V. Bazhenov, N. L.; Izhnin, A. I.; Izhnin, I. I.; Mikhailov, N. N.; Varavin, V. S.; Dvoretsky, S. A.

    2015-03-15

    The photoluminescence method is used to study acceptor states in CdHgTe heteroepitaxial films (HEFs) grown by molecular-beam epitaxy. A comparison of the photoluminescence spectra of HEFs grown on GaAs substrates (CdHgTe/GaAs) with the spectra of CdHgTe/Si HEFs demonstrates that acceptor states with energy depths of about 18 and 27 meV are specific to CdHgTe/GaAs HEFs. The possible nature of these states and its relation to the HEF synthesis conditions and, in particular, to the vacancy doping occurring under conditions of a mercury deficiency during the course of epitaxy and postgrowth processing are discussed.

  8. Progress, challenges, and opportunities for HgCdTe infrared materials and detectors

    NASA Astrophysics Data System (ADS)

    Lei, Wen; Antoszewski, Jarek; Faraone, Lorenzo

    2015-12-01

    This article presents a review on the current status, challenges, and potential future development opportunities for HgCdTe infrared materials and detector technology. A brief history of HgCdTe infrared technology is firstly summarized and discussed, leading to the conclusion that HgCdTe-based infrared detectors will continue to be a core infrared technology with expanded capabilities in the future due to a unique combination of its favourable properties. Recent progress and the current status of HgCdTe infrared technology are reviewed, including material growth, device architecture, device processing, surface passivation, and focal plane array applications. The further development of infrared applications requires that future infrared detectors have the features of lower cost, smaller pixel size, larger array format size, higher operating temperature, and multi-band detection, which presents a number of serious challenges to current HgCdTe-based infrared technology. The primary challenges include well controlled p-type doping, lower cost, larger array format size, higher operating temperature, multi-band detection, and advanced plasma dry etching. Various new concepts and technologies are proposed and discussed that have the potential to overcome the existing primary challenges that are inhibiting the development of next generation HgCdTe infrared detector technology.

  9. Numerical study of near-, mid-, and long-infrared photon trapping in crystalline and amorphous HgCdTe metamaterials

    NASA Astrophysics Data System (ADS)

    Jung, Young Uk; Bendoym, Igor; Crouse, David T.

    2016-04-01

    Recently, mercury cadmium telluride (HgCdTe) films have been extensively studied for the metamaterial applications. Crystalline HgCdTe (c-HgCdTe) films attracted people's attention for the spectral detection when used as metasurfaces and demonstrated reduced volume size, increased operating temperature, and improved quantum efficiency. Amorphous HgCdTe (a-HgCdTe) films also have been studied due to their interesting properties. Such properties include film deposition on any substrate, direct growth on device, and higher operating temperatures with the low dark current. Hence, in this work, for the first time, we investigate and compare the use of c-HgCdTe and a-HgCdTe for the photon sorting metasurfaces in near-, mid-, and long-IR spectral range in the sensor applications.

  10. The Distribution Tail of LWIR HgCdTe-on-Si FPAs: a Hypothetical Physical Mechanism

    NASA Astrophysics Data System (ADS)

    Bubulac, L. O.; Benson, J. D.; Jacobs, R. N.; Stoltz, A. J.; Jaime-Vasquez, M.; Almeida, L. A.; Wang, A.; Wang, L.; Hellmer, R.; Golding, T.; Dinan, J. H.; Carmody, M.; Wijewarnasuriya, P. S.; Lee, M. F.; Vilela, M. F.; Peterson, J.; Johnson, S. M.; Lofgreen, D. F.; Rhiger, D.

    2011-03-01

    A model is proposed to explain disparities found in the operability values and histograms for long-wavelength infrared HgCdTe focal-plane arrays fabricated on Si substrates compared with those fabricated on CdZnTe. The starting point for the model is the close agreement between the aerial density of discrete species (particles, contamination spots, crystalline defects on Si surface) in various interfaces in the HgCdTe/CdTe/Si structure and the density of failed pixels in the array. The density of discrete species is acquired by applying a newly developed variation of the secondary-ion mass spectrometry (SIMS) depth-profiling technique to samples that have been deuterated to enhance detection. A mechanism of selective activation of threading dislocations in a HgCdTe layer on Si is proposed to link discrete species with failed detector pixels.

  11. Cyclotron resonance in HgTe/CdTe-based heterostructures in high magnetic fields

    PubMed Central

    2012-01-01

    Cyclotron resonance study of HgTe/CdTe-based quantum wells with both inverted and normal band structures in quantizing magnetic fields was performed. In semimetallic HgTe quantum wells with inverted band structure, a hole cyclotron resonance line was observed for the first time. In the samples with normal band structure, interband transitions were observed with wide line width due to quantum well width fluctuations. In all samples, impurity-related magnetoabsorption lines were revealed. The obtained results were interpreted within the Kane 8·8 model, the valence band offset of CdTe and HgTe, and the Kane parameter EP being adjusted. PMID:23013642

  12. Occurrence of toxic metals (Hg, Cd and Pb) in fresh and canned tuna: public health implications.

    PubMed

    Storelli, Maria M; Barone, Grazia; Cuttone, Giuseppe; Giungato, Daniele; Garofalo, Rita

    2010-11-01

    Hg, Pb and Cd levels in fresh and canned tuna were determined and assessed by comparing element levels in these samples with maximum permissible limits set by European legislation. The estimated weekly intakes by human consuming both fresh and canned tuna were also evaluated for possible consumer health risks. Among tested metals, Hg had the highest concentrations, followed by Pb and Cd either in fresh tuna or canned tuna. None of the tested samples surpassed the European regulatory limits fixed for Cd and Pb, whereas 8.9% of the tuna cans and 20% of fresh tuna samples exceeded standard for Hg. The size of tuna was a determining factor of Hg burden. A high intake of Hg surpassing the toxicological reference value established by WHO, was associated with consumption of larger size tuna specimens. Also canned tuna consumption with Hg concentrations higher than 1 μg kg(-1), strongly increased the consumer exposure. In contrast, Cd and Pb weekly intakes through consumption either of fresh tuna or canned tuna did not exceed the toxicological reference values established by WHO, and consequently there was no human health risk. A continuous surveillance system of Hg content in these fishery products is crucial for consumer protection.

  13. Occurrence of toxic metals (Hg, Cd and Pb) in fresh and canned tuna: public health implications.

    PubMed

    Storelli, Maria M; Barone, Grazia; Cuttone, Giuseppe; Giungato, Daniele; Garofalo, Rita

    2010-11-01

    Hg, Pb and Cd levels in fresh and canned tuna were determined and assessed by comparing element levels in these samples with maximum permissible limits set by European legislation. The estimated weekly intakes by human consuming both fresh and canned tuna were also evaluated for possible consumer health risks. Among tested metals, Hg had the highest concentrations, followed by Pb and Cd either in fresh tuna or canned tuna. None of the tested samples surpassed the European regulatory limits fixed for Cd and Pb, whereas 8.9% of the tuna cans and 20% of fresh tuna samples exceeded standard for Hg. The size of tuna was a determining factor of Hg burden. A high intake of Hg surpassing the toxicological reference value established by WHO, was associated with consumption of larger size tuna specimens. Also canned tuna consumption with Hg concentrations higher than 1 μg kg(-1), strongly increased the consumer exposure. In contrast, Cd and Pb weekly intakes through consumption either of fresh tuna or canned tuna did not exceed the toxicological reference values established by WHO, and consequently there was no human health risk. A continuous surveillance system of Hg content in these fishery products is crucial for consumer protection. PMID:20728500

  14. Low Temperature, Rapid Thermal Cycle Annealing of HgCdTe Grown on CdTe/Si

    NASA Astrophysics Data System (ADS)

    Simingalam, Sina; Brill, Gregory; Wijewarnasuriya, Priyalal; Rao, Mulpuri V.

    2015-05-01

    The HgCdTe(MCT) grown on CdTe/Si substrate has a high dislocation density due to lattice mismatch. Thermal cycle annealing (TCA) is effective in reducing the dislocation density. The TCA at high temperatures results in inter-diffusion of the constituent elements across the MCT/CdTe interface. In this study, we observed a reduction in dislocation density with good surface morphology due to proper design of the TCA system, low annealing temperature, and large number of annealing cycles. The ampoule containing the samples is placed in direct contact with the graphite heating tube which helps in increasing the heating and cooling rates of the annealing cycle. To maintain Hg overpressure, Hg is placed in the sample holder, instead of in the ampoule to avoid Hg condensation. The best results were obtained by cycling the annealing temperature between 290°C and 350°C. Anneals were performed by using 32, 64, 128 and 256 cycles. We obtained an etch pit density (EPD) as low as 1 × 106 cm-2. Lower EPD was not achieved either by increasing annealing temperature or number of annealing cycles. Through secondary ion mass spectroscopy analysis, we observed very little inter-diffusion of Cd across the MCT/CdTe interface for the 128 cycle annealing. These results show promise in bridging the gap in the device performance between the MCT material grown on CdTe/Si and CdZnTe substrates.

  15. Molecular Beam Epitaxy Growth of HgCdTe on Large-Area Si and CdZnTe Substrates

    NASA Astrophysics Data System (ADS)

    Reddy, M.; Peterson, J. M.; Vang, T.; Franklin, J. A.; Vilela, M. F.; Olsson, K.; Patten, E. A.; Radford, W. A.; Bangs, J. W.; Melkonian, L.; Smith, E. P. G.; Lofgreen, D. D.; Johnson, S. M.

    2011-08-01

    This paper presents the status of HgCdTe growth on large-area Si and CdZnTe substrates at Raytheon Vision Systems (RVS). The different technological tools that were used to scale up the growth from 4 inch to 6 inch diameter on Si and from 4 cm × 4 cm to 8 cm × 8 cm on CdZnTe without sacrificing the quality of the layers are described. Extremely high compositional uniformity and low macrodefect density were achieved for single- and two-color HgCdTe layers on both Si and CdZnTe substrates. Finally, a few examples of detector and focal-plane array results are included to highlight the importance of high compositional uniformity and uniformly low macrodefect density of the epitaxial layers in obtaining high operability and low cluster outages in single- and two-color focal-plane arrays (FPAs).

  16. Defect chemistry and characterization of Hg sub 1x Cd sub x Te

    NASA Technical Reports Server (NTRS)

    Vydyanath, H. R.

    1982-01-01

    Single crystal samples of undoped and doped Hg sub 1-x Cd sub x Te were annealed at varying temperatures and partial pressures of Hg. Hall effect and mobility measurements were carried out on these samples after quenching to room temperature. Based on the variation of the carrier concentration and the carrier mobility as a function of the partial pressure of Hg temperature, and dopant concentration, defect models were established for the doped and the undoped crystals. These models indicate that the native acceptor defects in both Hg0.8Cd0.2Te and Hg0.6Cd0.4Te doubly ionized and the native donor defects are negligible in concentration, implying that p to n conversion in these alloys occurs due only to residual donors. Incorporation mechanism of copper, indium, iodine, and phosphorus were investigated. A large concentration of indium is found to be paired with the native acceptor defects. Results on crystals doped with phosphorus indicate that phosphorus behaves amphoterically, acting as a donor on Hg lattice sites and as an acceptor intersitially on Te lattice sites. A majority of the phosphorus is found to be present as neutral species formed from the pairing reaction between phosphorus on Hg lattice sites and phosphorus in interstitial sites. Equilibrium constants for the intrinsic excitation reaction, as well as for the incorporation of the different dopants and the native acceptor defects were established.

  17. Investigation of linear-mode photon-counting HgCdTe APDs for astronomical observations

    NASA Astrophysics Data System (ADS)

    Bryan, Marta L.; Chapman, George; Hall, Donald N. B.; Jack, Michael D.; Jacobson, Shane M.; Wehner, Justin

    2012-07-01

    The unique linear avalanche properties of HgCdTe preserve the Poisson statistics of the incoming photons, opening up new opportunities for GHz bandwidth LADAR and space communications applications. Raytheon has developed and previously reported (1) unique linear mode photon counting arrays based on combining advanced HgCdTe linear mode APDs with their high gain SB415B readout. Their use of HgCdTe APDs preserves the Poisson statistics of the incoming photons, enabling (noiseless) photon counting. This technology is of great potential interest to infrared astronomy but requires extension of noiseless linear HgCdTe avalanching down to much lower bandwidths (100 to 0.001 Hz) with corresponding reductions in dark count rate. We have hybridized the SB415B readout to SWIR HgCdTe APDs optimized for low dark count rate and have characterized their photon counting properties at bandwidths down to 1 KHz. As bandwidth is reduced, the performance becomes limited by the intrinsic properties of the SB415B readout, particularly readout glow, stability and 1/f noise. We report the results of these measurements and the status of hybrid arrays utilizing a newly developed readout which draws on Raytheon’s astronomical readout heritage, specifically the Virgo charge integrating source follower, as a path to much lower dark count rate photon counting operation.

  18. Magnetotransport in double quantum well with inverted energy spectrum: HgTe/CdHgTe

    NASA Astrophysics Data System (ADS)

    Yakunin, M. V.; Suslov, A. V.; Popov, M. R.; Novik, E. G.; Dvoretsky, S. A.; Mikhailov, N. N.

    2016-02-01

    We present an experimental study of the double-quantum-well (DQW) system made of two-dimensional layers with inverted energy band spectrum: HgTe. The magnetotransport reveals a considerably larger overlap of the conduction and valence subbands than in known HgTe single quantum wells (QW), which may be regulated here by an applied gate voltage Vg. This large overlap manifests itself in a much higher critical field Bc separating the range above it with a plain behavior of the Hall magnetoresistance ρx y(B ) , where the quantum peculiarities shift linearly with Vg, and the range below with a complicated behavior. In the latter case, specific structures in ρx y(B ) are formed like a double-N -shaped ρx y(B ) , reentrant sign-alternating quantum Hall effect with transitions into a zero-filling-factor state, etc., which are clearly manifested here due to better magnetic quantization at high fields, as compared to the features seen earlier in a single HgTe QW. The coexisting electrons and holes were found in the whole investigated range of positive and negative Vg as revealed (i) from fits to the low-field N -shaped ρx y(B ) , (ii) from the Fourier analysis of oscillations in ρx x(B ) , and (iii) from a specific behavior of ρx y(B ) at high positive Vg. A peculiar feature here is that the found electron density n remains almost constant in the whole range of investigated Vg while the hole density p drops down from the value a factor of 6 larger than n at extreme negative Vg to almost zero at extreme positive Vg passing through the charge-neutrality point. We show that this difference between n and p stems from an order of magnitude larger density of states for holes in the lateral valence subband maxima than for electrons in the conduction subband minimum. We analyze our observations on the basis of a calculated picture of magnetic levels in a DQW and suggest that their specificity is due to (i) a nonmonotonic course of the valence subband magnetic levels and an

  19. High-value utilization of lignin to synthesize Ag nanoparticles with detection capacity for Hg²⁺.

    PubMed

    Shen, Zuguang; Luo, Yuqiong; Wang, Qun; Wang, Xiaoying; Sun, Runcang

    2014-09-24

    This study reports the rapid preparation of silver nanoparticles (AgNPs) from Tollens' reagent under microwave irradiation. In the synthesis, lignin with reducing groups and spatial three-dimensional structure was used as reducing and stabilizing agents without other chemical reagents, and the effects of the ratio of lignin to Ag(+), reaction temperature, and heating time on the synthesis of AgNPs were investigated. The obtained AgNPs were further characterized by UV-vis, Malvern particle size, TEM, XRD, and XPS analyses. The structural changes of lignin before and after reaction were also studied by FT-IR, (1)H NMR, (13)C NMR, and GC-MS. The results revealed that the obtained AgNPs were mostly spherical with diameters of around 24 nm. The optimum reaction conditions were a ratio 50 mg of lignin to 0.3 mM of Ag(+), a microwave irradiation temperature of 60 °C, and a heating time of 10 min. Moreover, AgNPs redispersed well in water and ethanol after centrifugation for the removal of lignin. During the formation of AgNPs, lignin was oxidized, and the side chains of lignin were partly disrupted into small molecules, such as hydrocarbon and alcohol. The resultant lignin-AgNPs showed highly selective sensing detection for Hg(2+), and the color of the lignin-AgNP solution containing Hg(2+) decreased gradually with increasing amounts of Hg(2+) within seconds, but the other 19 metal ions had little effect on the color and surface plasmon absorption band of the lignin-AgNPs. Also, there was a linear relationship between the absorbance and Hg(2+) concentration, with a limit of detection concentration of 23 nM. This study provides not only a new way to take advantage of agricultural and forestry residues, but also a green and rapid method for the synthesis of AgNPs to detect the toxic ion Hg(2+) selectively and sensitively.

  20. Nonlinear terahertz response of HgTe/CdTe quantum wells

    SciTech Connect

    Chen, Qinjun; Sanderson, Matthew; Zhang, Chao

    2015-08-24

    Without breaking the topological order, HgTe/CdTe quantum wells can have two types of bulk band structure: direct gap type (type I) and indirect gap type (type II). We report that the strong nonlinear optical responses exist in both types of bulk states under a moderate electric field in the terahertz regime. Interestingly, for the type II band structure, the third order conductivity changes sign when chemical potentials lies below 10 meV due to the significant response of the hole excitation close to the bottom of conduction band. Negative nonlinear conductivities suggest that HgTe/CdTe quantum wells can find application in the gain medium of a laser for terahertz radiation. The thermal influences on nonlinear optical responses of HgTe/CdTe quantum wells are also studied.

  1. HgCdTe long-wavelength infrared photovoltaic detectors formed by reactive ion etching

    NASA Astrophysics Data System (ADS)

    Nguyen, Tam T.; Dell, John M.; Musca, Charles A.; Antoszewski, Jarek; Faraone, Lorenzo

    2002-12-01

    Reactive ion etching (RIE) is known to type convert p-type HgCdTe to n-type, thus providing a method for p-n junction formation for photodiode fabrication. Mid-wavelength infrared (MWIR) n-on-p photodiodes fabricated using RIE induced p-to-n type conversion have already been demonstrated and show excellent performance. This paper will report on the successful application of RIE junction formation technology for long-wavelength infrared (LWIR) HgCdTe photodiodes, and compares the device performance of photodiodes fabricated on vacancy and extrinsically doped p-type HgCdTe. The diode current versus bias voltage (I-V) characteristic of these devices have also been measured as a function of temperature in the range 20K to 200K with various junction areas. These results are compared in the light of detailed Hall measurement data obtained from type converted materials.

  2. Inductively coupled plasma etching of HgCdTe IRFPAs detectors at cryogenic temperature

    NASA Astrophysics Data System (ADS)

    Chen, Y. Y.; Ye, Z. H.; Sun, C. H.; Zhang, S.; Hu, X. N.; Ding, R. J.; He, L.

    2016-05-01

    To fabricate various advanced structures with HgCdTe material, the Inductively Coupled Plasma enhanced Reactive Ion Etching system is indispensable. However, due to low damage threshold and complicated behaviors of mercury in HgCdTe, the lattice damage and induced electrical conversion is very common. According to the diffusion model during etching period, the mercury interstitials, however, may not diffuse deep into the material at cryogenic temperature. In this report, ICP etching of HgCdTe at cryogenic temperature was implemented. The etching system with cryogenic assembly is provided by Oxford Instrument. The sample table was cooled down to 123K with liquid nitrogen. The mask of SiO2 with a contact layer of ZnS functioned well at this temperature. The selectivity and etching velocity maintained the same as reported in the etching of room temperature. Smooth and clean surfaces and profiles were achieved with an optimized recipe.

  3. HgCdTe: Recent Trends in the Ultimate IR Semiconductor

    NASA Astrophysics Data System (ADS)

    Kinch, Michael A.

    2010-07-01

    Since its introduction in the early 1970s, HgCdTe has become the general workhorse of the global infrared (IR) industry. Despite a significant lack of investment in the basic science of this materials system since 1990, huge advances have been made in HgCdTe focal-plane array (FPA) technology, resulting in the current availability of a wide variety of large-area FPAs, for all IR spectral bands, both monocolor and multicolor, with the capability for both passive and active imaging. The current status of the many technologies relevant to the continued good health of HgCdTe is discussed herein, with regard to both their present limitations and possible opportunities for improvement.

  4. Surface electrons in inverted layers of p-HgCdTe

    NASA Technical Reports Server (NTRS)

    Schacham, Samuel E.; Finkman, Eliezer

    1990-01-01

    Anodic oxide passivation of p-type HgCdTe generates an inversion layer. Extremely high Hall mobility data for electrons in this layer indicated the presence of a two-dimensional electron gas. This is verified by use of the Shubnikov-de Haas effect from 1.45 to 4.15 K. Data are extracted utilizing a numerical second derivative of dc measurement. Three sub-bands are detected. Their relative occupancies are in excellent agreement with theory and with experimental results obtained on anodic oxide as accumulation layers of n-type HgCdTe. The effective mass derived is comparable to what was expected.

  5. Thin-Film HgCdTe For Mosaic Focal Planes

    NASA Astrophysics Data System (ADS)

    Krikorian, E.

    1981-02-01

    Hgl-xCdxTe is becoming increasingly important for the preparation of both monolithic and hybrid infrared focal plane arrays. The preparation of such devices utilizing thin film HgCdTe is very attractive due to its cost-effective feature. Based on a study carried out at General Dynamics, sputtering, which minimizes the vapor pressure problems of HgCdTe deposition, promises to be a relatively simple, inexpensive and versatile technique for preparing high quality single crystal Hgl-xCdxTe films with electronic properties suitable for array (large area) fabrication. This paper reports on the initial results of this study which support this claim.

  6. Recent progress in LWIR HOT photoconductors based on MOCVD grown (100) HgCdTe

    NASA Astrophysics Data System (ADS)

    Gawron, W.; Kębłowski, A.; Kopytko, M.; Madejczyk, P.; Martyniuk, P.; Pędzińska, M.; Piotrowski, A.; Piotrowski, J.; Rogalski, A.; Romanis, M.; Sosna, A.

    2016-10-01

    Hg1-x Cd x Te photoconductors grown in (100) crystallographic orientation are prone to demonstrating high crystalline quality, which results in a lower number of generation-recombination centers, lower noise and high responsivity. This work presents the optimum growth conditions and results of the characterization both of layers and high operating temperature (HOT) long wavelength infrared (LWIR) photoconductive devices based on them. The (100) HgCdTe photoconductor attains D*(13 μm) equal to 6.5 × 109 cmHz1/2W-1 at 200 K and therefore outperforms its (111)B counterpart.

  7. HgCdTe Photoconductive Mixers for 2-8 THz

    NASA Technical Reports Server (NTRS)

    Betz, A. L.; Boreiko, R. T.; Sivananthan, S.; Ashokan, R.

    2001-01-01

    Heterodyne spectroscopy has been taken to wavelengths as short as 63 micrometers with Schottky-diode mixers. Schottkys, however, are relatively insensitive compared to superconducting mixers such as the hot-electron microbolometer (HEB), which has an effective quantum efficiency of 3% at 120 micrometers (2.5 THz). Although HEB sensitivities are bound to improve, there will always be losses associated with antenna coupling of radiation into sub-micron size devices. Another approach to far infrared (FIR) mixer design is to use a photoconductive device which can be made much larger than a wavelength, and thus act as its own antenna. For example, HgCdTe photodiodes have been used as mixers in the lambda = 10 micrometers band for over 25 years, with sensitivities now only a factor of 2 from the quantum-noise-limit. HgCdTe can also be applied at FIR wavelengths, but surprisingly little work has been done to date. The exception is the pioneering work of Spears and Kostiuk and Spears, who developed HgCdTe photomixers for the 20-120 micrometer region. The spectral versatility of the HgCdTe alloy is well recognized for wavelengths as long as 8-20 micrometers. What is not so recognized, however, is that theoretically there is no long wavelength limit for appropriately composited HgCdTe. Although Spears successfully demonstrated a photoconductive response from HgCdTe at 120 micrometers, this initial effort was apparently never followed up, in part because of the difficulty of controlling the HgCdTe alloy composition with liquid-phase-epitaxy (LPE) techniques. With the availability of precise molecular-beam-epitaxy (MBE) since the early 1990's, it is now appropriate to reconsider HgCdTe for detector applications longward of lambda = 20 micrometers. We recently initiated an effort to fabricate detectors and mixers using II-VI materials for FIR wavelengths. Of particular interest are device structures called superlattices, which offer a number of advantages for high sensitivity

  8. Temperature-driven massless Kane fermions in HgCdTe crystals

    NASA Astrophysics Data System (ADS)

    Teppe, F.; Marcinkiewicz, M.; Krishtopenko, S. S.; Ruffenach, S.; Consejo, C.; Kadykov, A. M.; Desrat, W.; But, D.; Knap, W.; Ludwig, J.; Moon, S.; Smirnov, D.; Orlita, M.; Jiang, Z.; Morozov, S. V.; Gavrilenko, V. I.; Mikhailov, N. N.; Dvoretskii, S. A.

    2016-08-01

    It has recently been shown that electronic states in bulk gapless HgCdTe offer another realization of pseudo-relativistic three-dimensional particles in condensed matter systems. These single valley relativistic states, massless Kane fermions, cannot be described by any other relativistic particles. Furthermore, the HgCdTe band structure can be continuously tailored by modifying cadmium content or temperature. At critical concentration or temperature, the bandgap collapses as the system undergoes a semimetal-to-semiconductor topological phase transition between the inverted and normal alignments. Here, using far-infrared magneto-spectroscopy we explore the continuous evolution of band structure of bulk HgCdTe as temperature is tuned across the topological phase transition. We demonstrate that the rest mass of Kane fermions changes sign at critical temperature, whereas their velocity remains constant. The velocity universal value of (1.07+/-0.05) × 106 m s-1 remains valid in a broad range of temperatures and Cd concentrations, indicating a striking universality of the pseudo-relativistic description of the Kane fermions in HgCdTe.

  9. Temperature-driven massless Kane fermions in HgCdTe crystals

    PubMed Central

    Teppe, F.; Marcinkiewicz, M.; Krishtopenko, S. S.; Ruffenach, S.; Consejo, C.; Kadykov, A. M.; Desrat, W.; But, D.; Knap, W.; Ludwig, J.; Moon, S.; Smirnov, D.; Orlita, M.; Jiang, Z.; Morozov, S. V.; Gavrilenko, V.I.; Mikhailov, N. N.; Dvoretskii, S. A.

    2016-01-01

    It has recently been shown that electronic states in bulk gapless HgCdTe offer another realization of pseudo-relativistic three-dimensional particles in condensed matter systems. These single valley relativistic states, massless Kane fermions, cannot be described by any other relativistic particles. Furthermore, the HgCdTe band structure can be continuously tailored by modifying cadmium content or temperature. At critical concentration or temperature, the bandgap collapses as the system undergoes a semimetal-to-semiconductor topological phase transition between the inverted and normal alignments. Here, using far-infrared magneto-spectroscopy we explore the continuous evolution of band structure of bulk HgCdTe as temperature is tuned across the topological phase transition. We demonstrate that the rest mass of Kane fermions changes sign at critical temperature, whereas their velocity remains constant. The velocity universal value of (1.07±0.05) × 106 m s−1 remains valid in a broad range of temperatures and Cd concentrations, indicating a striking universality of the pseudo-relativistic description of the Kane fermions in HgCdTe. PMID:27573209

  10. Temperature-driven massless Kane fermions in HgCdTe crystals.

    PubMed

    Teppe, F; Marcinkiewicz, M; Krishtopenko, S S; Ruffenach, S; Consejo, C; Kadykov, A M; Desrat, W; But, D; Knap, W; Ludwig, J; Moon, S; Smirnov, D; Orlita, M; Jiang, Z; Morozov, S V; Gavrilenko, V I; Mikhailov, N N; Dvoretskii, S A

    2016-08-30

    It has recently been shown that electronic states in bulk gapless HgCdTe offer another realization of pseudo-relativistic three-dimensional particles in condensed matter systems. These single valley relativistic states, massless Kane fermions, cannot be described by any other relativistic particles. Furthermore, the HgCdTe band structure can be continuously tailored by modifying cadmium content or temperature. At critical concentration or temperature, the bandgap collapses as the system undergoes a semimetal-to-semiconductor topological phase transition between the inverted and normal alignments. Here, using far-infrared magneto-spectroscopy we explore the continuous evolution of band structure of bulk HgCdTe as temperature is tuned across the topological phase transition. We demonstrate that the rest mass of Kane fermions changes sign at critical temperature, whereas their velocity remains constant. The velocity universal value of (1.07±0.05) × 10(6) m s(-1) remains valid in a broad range of temperatures and Cd concentrations, indicating a striking universality of the pseudo-relativistic description of the Kane fermions in HgCdTe.

  11. Temperature-driven massless Kane fermions in HgCdTe crystals.

    PubMed

    Teppe, F; Marcinkiewicz, M; Krishtopenko, S S; Ruffenach, S; Consejo, C; Kadykov, A M; Desrat, W; But, D; Knap, W; Ludwig, J; Moon, S; Smirnov, D; Orlita, M; Jiang, Z; Morozov, S V; Gavrilenko, V I; Mikhailov, N N; Dvoretskii, S A

    2016-01-01

    It has recently been shown that electronic states in bulk gapless HgCdTe offer another realization of pseudo-relativistic three-dimensional particles in condensed matter systems. These single valley relativistic states, massless Kane fermions, cannot be described by any other relativistic particles. Furthermore, the HgCdTe band structure can be continuously tailored by modifying cadmium content or temperature. At critical concentration or temperature, the bandgap collapses as the system undergoes a semimetal-to-semiconductor topological phase transition between the inverted and normal alignments. Here, using far-infrared magneto-spectroscopy we explore the continuous evolution of band structure of bulk HgCdTe as temperature is tuned across the topological phase transition. We demonstrate that the rest mass of Kane fermions changes sign at critical temperature, whereas their velocity remains constant. The velocity universal value of (1.07±0.05) × 10(6) m s(-1) remains valid in a broad range of temperatures and Cd concentrations, indicating a striking universality of the pseudo-relativistic description of the Kane fermions in HgCdTe. PMID:27573209

  12. Bioavailability of Cd, Zn and Hg in Soil to Nine Recombinant Luminescent Metal Sensor Bacteria

    PubMed Central

    Bondarenko, Olesja; Rõlova, Taisia; Kahru, Anne; Ivask, Angela

    2008-01-01

    A set of nine recombinant heavy metal-specific luminescent bacterial sensors belonging to Gram-negative (Escherichia and Pseudomonas) and Gram-positive (Staphylococcus and Bacillus) genera and containing various types of recombinant metal-response genetic elements was characterized for heavy metal bioavailability studies. All nine strains were induced by Hg and Cd and five strains also by Zn. As a lowest limit, the sensors were detecting 0.03 μg·L-1 of Hg, 2 μg·L-1 of Cd and 400 μg·L-1 of Zn. Limit of determination of the sensors depended mostly on metal-response element, whereas the toxicity of those metals towards the sensor bacteria was mostly dependent on the type of the host bacterium, with Gram-positive strains being more sensitive than Gram-negative ones. The set of sensors was used to evaluate bioavailability of Hg, Cd and Zn in spiked soils. The bioavailable fraction of Cd and Zn in soil suspension assay (2.6 – 5.1% and 0.32 – 0.61%, of the total Cd and Zn, respectively) was almost comparable for all the sensors, whereas the bioavailability of Hg was about 10-fold higher for Gram-negative sensor cells (30.5% of total Hg), compared to Gram-positive ones (3.2% of the total Hg). For Zn, the bioavailable fraction in soil-water suspensions and respective extracts was comparable (0.37 versus 0.33% of the total Zn). However, in the case of Cd, for all the sensors used and for Hg concerning only Gram-negative sensor strains, the bioavailable fraction in soil-water suspensions exceeded the water-extracted fraction about 14-fold, indicating that upon direct contact, an additional fraction of Cd and Hg was mobilized by those sensor bacteria. Thus, for robust bioavailability studies of heavy metals in soils any type of genetic metal-response elements could be used for the construction of the sensor strains. However, Gram-positive and Gram-negative senor strains should be used in parallel as the bioavailability of heavy metals to those bacterial groups may be

  13. Bioaccumulation of As, Cd, Cr, Hg(II), and MeHg in killifish (Fundulus heteroclitus) from amphipod and worm prey.

    PubMed

    Dutton, Jessica; Fisher, Nicholas S

    2011-08-15

    Elevated metal levels in fish are a concern for the fish themselves, their predators, and possibly humans who consume contaminated seafood. Metal bioaccumulation models often rely on assimilation efficiencies (AEs) of ingested metals and loss rate constants after dietary exposure (k(ef)s). These models can be used to better understand processes regulating metal accumulation and can be used to make site-specific predictions of metal concentrations in animal tissues. Fish often consume a varied diet, and prey choice can influence these two parameters. We investigated the trophic transfer of As, Cd, Cr, Hg(II), and methylmercury (MeHg) from a benthic amphipod (Leptocheirus plumulosus) and an oligochaete (Lumbriculus variegatus) to killifish (Fundulus heteroclitus) using gamma-emitting radioisotopes. Except for MeHg, AEs varied between prey type. AEs were highest for MeHg (92%) and lowest for Cd (2.9-4.5%) and Cr (0.2-4%). Hg(II) showed the largest AE difference between prey type (14% amphipods, 24% worms). For Cd and Hg(II) k(ef)s were higher after consuming amphipods than consuming worms. Tissue distribution data shows that Cd and Hg(II) were mainly associated with the intestine, whereas As and MeHg were transported throughout the body. Calculated trophic transfer factors (TTFs) suggest that MeHg is likely to biomagnify at this trophic step at all ingestion rates, whereas As, Cd, Cr, and Hg(II) will not. Data collected in this study and others indicate that using one prey item to calculate AE and k(ef) could lead to an over- or underestimation of these parameters. PMID:21658746

  14. Extranuclear dynamics of 111Ag(→111Cd) doped in AgI nanoparticles

    NASA Astrophysics Data System (ADS)

    Sato, W.; Mizuuchi, R.; Irioka, N.; Komatsuda, S.; Kawata, S.; Taoka, A.; Ohkubo, Y.

    2014-08-01

    Dynamic behavior of the extranuclear field relative to the 111Ag(→111Cd) probe nucleus introduced in a superionic conductor silver iodide (AgI) was investigated by means of the time-differential perturbed angular correlation technique. For poly-N-vinyl-2-pyrrolidone (PVP)-coated AgI nanoparticles, we observed nuclear spin relaxation of the probe at room temperature. This result signifies that Ag+ ions in the polymer-coated sample make hopping motion from site to site at this low temperature. The activation energy for the dynamic motion was successfully estimated to be 46(10) meV. The first atomic-level observation of the temperature-dependent dynamic behavior of Ag+ ions in the polymer-coated AgI is reported.

  15. Exploiting the higher specificity of silver amalgamation: selective detection of mercury(II) by forming Ag/Hg amalgam.

    PubMed

    Deng, Li; Ouyang, Xiangyuan; Jin, Jianyu; Ma, Cheng; Jiang, Ying; Zheng, Jing; Li, Jishan; Li, Yinhui; Tan, Weihong; Yang, Ronghua

    2013-09-17

    Heavy metal ion pollution poses severe risks in human health and the environment. Driven by the need to detect trace amounts of mercury, this article demonstrates, for the first time, that silver/mercury amalgamation, combining with DNA-protected silver nanoparticles (AgNPs), can be used for rapid, easy and reliable screening of Hg(2+) ions with high sensitivity and selectivity over competing analytes. In our proposed approach, Hg(2+) detection is achieved by reducing the mercury species to elemental mercury, silver atoms were chosen as the mercury atoms' acceptors by forming Ag/Hg amalgam. To signal fluorescently this silver amalgamation event, a FAM-labeled ssDNA was employed as the signal reporter. AgNPs were grown on the DNA strand that resulted in greatly quenching the FAM fluorescence. Formation of Ag/Hg amalgam suppresses AgNPs growth on the DNA, leading to fluorescence signal increase relative to the fluorescence without Hg(2+) ions, as well as marked by fluorescence quenching. This FAM fluorescence enhancement can be used for detection of Hg(2+) at the a few nanomolar level. Moreover, due to excellent specificity of silver amalgamation with mercury, the sensing system is highly selective for Hg(2+) and does not respond to other metal ions with up to millimolar concentration levels. This sensor is successfully applied to determination of Hg(2+) in tap water, spring water and river water samples. The results shown herein have important implications in the development of new fluorescent sensors for the fast, easy, and selective detection and quantification of Hg(2+) in environmental and biological samples. PMID:23937672

  16. Distribution of the surface potential of epitaxial HgCdTe

    SciTech Connect

    Novikov, V. A. Grigoryev, D. V.; Bezrodnyy, D. A.; Dvoretsky, S. A.

    2014-09-08

    We studied the distribution of surface potential of the Hg{sub 1−x}Cd{sub x}Te epitaxial films grown by molecular beam epitaxy. The studies showed that the variation of the spatial distribution of surface potential in the region of the V-defect can be related to the variation of the material composition of epitaxial film. The V-defect is characterized by increased of Hg content with respect to the composition of the solid solution of Hg{sub 1−x}Cd{sub x}Te epitaxial film. In this paper, it was demonstrated that the unformed V-defects can be observed together with the macroscopic V-defects on the epitaxial film surface. These unformed V-defects can allow the creation of a complex surface potential distribution profile due to the redistribution of the solid solution composition.

  17. Influence of photoresist feature geometry on ECR plasma-etched HgCdTe trenches

    NASA Astrophysics Data System (ADS)

    Benson, J. David; Stoltz, Andrew J., Jr.; Kaleczyc, Andrew W.; Martinka, Mike; Almeida, Leo A.; Boyd, Phillip R.; Dinan, John H.

    2002-12-01

    Factors that affect width and aspect ratio in electron cyclotron resonance (ECR) etched HgCdTe trenches are investigated. The ECR etch bias and anisotropy are determined by photoresist feature erosion rate. The physical characteristics of the trenches are attributed to ECR plasma etch chemistry.

  18. Arsenic complexes optical signatures in As-doped HgCdTe

    SciTech Connect

    Gemain, F.; Robin, I. C.; Brochen, S.; Ballet, P.; Gravrand, O.; Feuillet, G.

    2013-04-08

    In this paper, the optical signatures of arsenic complexes in As-doped HgCdTe samples grown by molecular beam epitaxy are clearly identified using comparison between photoluminescence spectra, Extended X-Ray Absorption Fine Structure, and Hall measurements. The ionization energies of the different complexes are measured both by photoluminescence and Hall measurements.

  19. LWIR HgCdTe: Innovative detectors in an incumbent technology

    NASA Technical Reports Server (NTRS)

    Tennant, William E.

    1990-01-01

    HgCdTe is the current material of choice for high performance imagers operating at relatively high temperatures. Its lack of technological maturity compared with silicon and wide-band gap III-V compounds is more than offset by its outstanding IR sensitivity and by the relatively benign effect of its materials defects. This latter property has allowed non-equilibrium growth techniques, metal oxide chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE), to produce device quality long wavelength infrared (LWIR) HgCdTe even on common substrates like GaAs and GaAs/Si. Detector performance in these exotic materials structures is comparable in many ways with devices in equilibrium-grown material. Lifetimes are similar. RoA values at 77K as high as several hundred have been seen in HgCdTe/GaAs/Si with 9.5 micron cut-off wavelength. HgCdTe/GaAs layers with approx. 15 micron cut-off wavelengths have given average 77K RoAs of greater than 2. Hybrid focal plane arrays have been evaluated with excellent operability.

  20. Lateral Diffusion Length Changes in HgCdTe Detectors in a Proton Environment

    NASA Technical Reports Server (NTRS)

    Hubbs, John E.; Marshall, Paul W.; Marshall, Cheryl J.; Gramer, Mark E.; Maestas, Diana; Garcia, John P.; Dole, Gary A.; Anderson, Amber A.

    2007-01-01

    This paper presents a study of the performance degradation in a proton environment of very long wavelength infrared (VLWIR) HgCdTe detectors. The energy dependence of the Non-Ionizing Energy Loss (NIEL) in HgCdTe provides a framework for estimating the responsivity degradation in VLWIR HgCdTe due to on orbit exposure from protons. Banded detector arrays that have different detector designs were irradiated at proton energies of 7, 12, and 63 MeV. These banded detector arrays allovedin sight into how the fundamental detector parameters degraded in a proton environment at the three different proton energies. Measured data demonstrated that the detector responsivity degradation at 7 MeV is 5 times larger than the degradation at 63 MeV. The comparison of the responsivity degradation at the different proton energies suggests that the atomic Columbic interaction of the protons with the HgCdTe detector is likely the primary mechanism responsible for the degradation in responsivity at proton energies below 30 MeV.

  1. Development of megapixel HgCdTe detector arrays with 15 micron cutoff

    NASA Astrophysics Data System (ADS)

    Forrest, William J.; McMurtry, Craig W.; Dorn, Meghan; Pipher, Judith; Cabrera, Mario S.

    2016-10-01

    I. HistoryHgCdTe is a versatile II-VI semiconductor with a direct-bandgap tunable via the Hg:Cd ratio. Hg:Cd ratio = 53:47 (2.5 micron cutoff) was used on the NICMOS instrument on HST and the 2MASS. Increasing Hg:Cd ratio to 70:30 leads to a 5.4 micron cutoff, utilized in NEOWISE and many JWST instruments. Bailey, Wu et al. (1998) motivated extending this technology to 10 microns and beyond. Bacon, McMurtry et al. (2003, 2004) indicated significant progress toward this longwave (LW) goal.Warm-Spitzer has pioneered passive cooling to below 30 K in space, enabling the JWST mission.II. CurrentNASA's proposed NEOcam mission selected HgCdTe with a 10.6 micron cutoff because it promises natural Zodiacal background limited sensitivity with modest cooling (40 K). Teledyne Imaging Systems (TIS) is producing megapixel arrays with excellent performance (McMurtry, Lee, Dorn et al. (2013)) for this mission.III. FutureModest cooling requirements (circa 30 K) coupled with megapixel arrays and LW sensitivity in the thermal IR make HgCdTe attractive for many infrared instruments. For instance, the spectral signature of a terrestrial planet orbiting in the habitable zone of a nearby star will be the deep and wide absorption by CO_2 centered at 15 microns (Seager and Deming, 2010). LW instruments can enhance Solar System missions, such as exploration of the Enceladus geysers (Spencer, Buratti et al. 2006). Passive cooling will be adequate for these missions. Modern ground-based observatories will benefit from infrared capability out to the N band (7.5-13.6 microns). The required detector temperatures (30-40 K) are easily achievable using commercially available mechanical cryo-coolers (refrigerators).IV. Progress to dateTIS is developing megapixel HgCdTe arrays sensitive out to 15 microns under the direction of the University of Rochester. As a first step, we have produced arrays with a 13 micron cutoff. The initial measurements indicate very promising performance. We will present the

  2. Development of megapixel HgCdTe detector arrays with 15 micron cutoff

    NASA Astrophysics Data System (ADS)

    Forrest, William J.; McMurtry, Craig W.; Dorn, Meghan L.; Pipher, Judith; Cabrera, Mario S.

    2016-06-01

    I. HistoryHgCdTe is a versatile II-VI semiconductor with a direct-bandgap tunable via the Hg:Cd ratio. Hg:Cd ratio = 53:47 (2.5 micron cutoff) was used on the NICMOS instrument on HST and the 2MASS. Increasing Hg:Cd ratio to 70:30 leads to a 5.4 micron cutoff, utilized in NEOWISE and many JWST instruments. Bailey, Wu et al. (1998) motivated extending this technology to 10 microns and beyond. Bacon, McMurtry et al. (2003, 2004) indicated significant progress toward this longwave (LW) goal.Warm-Spitzer has pioneered passive cooling to below 30 K in space, enabling the JWST mission.II. CurrentNASA's proposed NEOcam mission selected HgCdTe with a 10.6 micron cutoff because it promises natural Zodiacal background limited sensitivity with modest cooling (40 K). Teledyne Imaging Systems (TIS) is producing megapixel arrays with excellent performance (McMurtry, Lee, Dorn et al. (2013)) for this mission.III. FutureModest cooling requirements (circa 30 K) coupled with megapixel arrays and LW sensitivity in the thermal IR make HgCdTe attractive for many infrared instruments. For instance, the spectral signature of a terrestrial planet orbiting in the habitable zone of a nearby star will be the deep and wide absorption by CO_2 centered at 15 microns (Seager and Deming, 2010). LW instruments can enhance Solar System missions, such as exploration of the Enceladus geysers (Spencer, Buratti et al. 2006). Passive cooling will be adequate for these missions. Modern ground-based observatories will benefit from infrared capability out to the N band (7.5-13.6 microns). The required detector temperatures (30-40 K) are easily achievable using commercially available mechanical cryo-coolers (refrigerators).IV. Progress to dateTIS is developing megapixel HgCdTe arrays sensitive out to 15 microns under the direction of the University of Rochester. As a first step, we have produced arrays with a 13 micron cutoff. The initial measurements indicate very promising performance. We will present the

  3. Defect chemistry and characterization Hg(1-x)Cd(x)Te

    NASA Astrophysics Data System (ADS)

    Vydyanath, H. R.; Donovan, J. C.

    Iodine doped single crystal samples of mercury cadmium telluride were annealed at temperatures varying from 450 C to 600 C in Hg vapor and quenched to room temperature. Hall effect measurements at 77 K on the crystals cooled to room temperature indicate the samples to be n-type after anneals at high Hg pressures whereas they turn p-type after anneals at low Hg pressures; the electron concentration increases with increase in Hg pressure. The results are explained on the basis that the crystals are saturated with (Hg,Cd)I2, with a fraction of the iodine being present as donor occupying tellurium lattice sites and a fraction being present as acceptors resulting from the iodine on tellurium lattice sites pairing with the doubly ionized native acceptor defects. The solubility of the donor species increases with increase in Hg pressure, whereas that of the acceptor species increases with decrease in Hg pressure. Equilibrium constants for the incorporation of the iodine species as well as the pairing reaction were established.

  4. Defect chemistry and characterization Hg(1-x)Cd(x)Te

    NASA Technical Reports Server (NTRS)

    Vydyanath, H. R.; Donovan, J. C.

    1981-01-01

    Iodine doped single crystal samples of mercury cadmium telluride were annealed at temperatures varying from 450 C to 600 C in Hg vapor and quenched to room temperature. Hall effect measurements at 77 K on the crystals cooled to room temperature indicate the samples to be n-type after anneals at high Hg pressures whereas they turn p-type after anneals at low Hg pressures; the electron concentration increases with increase in Hg pressure. The results are explained on the basis that the crystals are saturated with (Hg,Cd)I2, with a fraction of the iodine being present as donor occupying tellurium lattice sites and a fraction being present as acceptors resulting from the iodine on tellurium lattice sites pairing with the doubly ionized native acceptor defects. The solubility of the donor species increases with increase in Hg pressure, whereas that of the acceptor species increases with decrease in Hg pressure. Equilibrium constants for the incorporation of the iodine species as well as the pairing reaction were established.

  5. Adsorption of Ag, Cu and Hg from aqueous solutions using expanded perlite.

    PubMed

    Ghassabzadeh, Hamid; Mohadespour, Ahmad; Torab-Mostaedi, Meisam; Zaheri, Parisa; Maragheh, Mohammad Ghannadi; Taheri, Hossein

    2010-05-15

    The aim of the present work was to investigate the ability of expanded perlite (EP) to remove of silver, copper and mercury ions from aqueous solutions. Batch adsorption experiments were carried out and the effect of pH, adsorbent dosage, contact time and temperature of solution on the removal process has been investigated. The optimum pH for the adsorption was found to be 6.5. Adsorption of these metal ions reached their equilibrium concentration in 120, 240 and 180 min for Ag (I), Cu (II) and Hg (II) ions, respectively. Experimental data were also evaluated in terms of kinetic characteristics of adsorption and it was found that adsorption process for these metal ions followed well pseudo-second-order kinetics. Using Langmuir isotherm model, maximum adsorption capacity of EP was found to be 8.46, 1.95 and 0.35 mg/g for Ag (I), Cu (II) and Hg (II) ions, respectively. Finally, the thermodynamic parameters including, the change of free energy (DeltaG degrees ), enthalpy (DeltaH degrees ) and entropy (DeltaS degrees ) of adsorption were calculated for each metal ion. The results showed that the adsorption of these metal ions on EP was feasible and exothermic at 20-50 degrees C.

  6. Biomonitoring potential of five sympatric Tillandsia species for evaluating urban metal pollution (Cd, Hg and Pb)

    NASA Astrophysics Data System (ADS)

    Sánchez-Chardi, Alejandro

    2016-04-01

    The present study quantifies non essential heavy metals highly toxic for biological systems (Pb, Hg and Cd) in five autochthonous epiphytic plants from Tillandsia genus (T. recurvata, T. meridionalis, T. duratii, T. tricholepis, T. loliacea) according to different traffic levels (reference, low, medium and high polluted sites) in Asunción (Paraguay). The three metals increased in polluted sites following Pb (till 62.99 ppm in T. tricholepis) > Cd (till 1.35 ppm in T. recurvata) > Hg (till 0.36 ppm in T. recurvata) and Pb and Cd levels were directly related to traffic flow. Although the species showed similar bioaccumulation pattern (namely, higher levels of metals in polluted sites), enrichment factors (maximum EF values 37.00, 18.16, and 11.90 for Pb, Hg, and Cd, respectively) reported T. tricholepis as the most relevant bioindicator due to its wide distribution and abundance in study sites, low metal content in control site and high metal contents in polluted sites, and significant correlations with traffic density of Pb and Cd. This study emphasizes the necessity of biomonitoring air pollution in areas out of air monitoring control such as Asunción, where the high levels of metal pollution especially Pb, may represent an increment of risk for the human population inhabiting this urban area.

  7. Cladding technique for development of Ag In Cd decoupler

    NASA Astrophysics Data System (ADS)

    Teshigawara, M.; Harada, M.; Saito, S.; Kikuchi, K.; Kogawa, H.; Ikeda, Y.; Kawai, M.; Kurishita, H.; Konashi, K.

    2005-08-01

    To develop a Ag (silver)-In (indium)-Cd (cadmium) alloy decoupler, a method is needed to bond the decoupler between two plates of the Al alloy (A6061-T6). We found that a better HIP condition was temperature, pressure and holding time at 803 K, 100 MPa and 1 h, respectively, for small test pieces ( ϕ 22 mm in diam. × 5 mm in height). Especially, a sandwich case (a Ag-In plate with thickness of 0.5 mm between two Ag-Cd plates with thickness of 1.25 mm) gave easier (or better) bonding results. Though a hardened layer is found in the bonding layer, the rupture strength of the bonding layer is more than 30 MPa, which is higher than the design stress in our application.

  8. Responses of membrane protection enzyme system of tobacco leaves on Hg, Cd and Pb stresses in soil.

    PubMed

    Yan, Chong Ling; Lin, Peng; Wang, Xiao Rong

    2002-09-01

    Pot experiment was used to study the responses of membrane protection enzyme system of tobacco leaves on Hg, Cd and Pb stresses in soil. The results showed that POD activity gradually increased with increasing concetrations of Hg, Cd and Pb. CAT and SOD activity gradually decreased under three heavy metals common existing and SOD variation curve showed unimodal curve under single or two elements existing with increase of concentration of Hg, Cd and Pb. The effects of Hg, Cd and Pb in soil: three elemets together > two elements together > single element only. The effects resulted in an imbalance--activated oxygen produce and scavenge and physiological biochemical process disorder. There was a synergistic action for the effect of Hg, Cd and Pb in soil on membrane protection enzyme system in tobacco leaves.

  9. Investigation of Substrate Effects on Interface Strain and Defect Generation in MBE-Grown HgCdTe

    NASA Astrophysics Data System (ADS)

    Gu, R.; Lei, W.; Antoszewski, J.; Faraone, L.

    2016-09-01

    Si, Ge, and GaAs have been extensively investigated as alternative substrates for molecular-beam epitaxy (MBE) growth of HgCdTe and, at present, are widely used for HgCdTe-based infrared focal-plane arrays. However, the problem of high dislocation density in HgCdTe layers grown on these lattice-mismatched substrates has yet to be resolved. In this work, we investigated another alternative substrate, GaSb, which has a significantly smaller lattice mismatch with HgCdTe in comparison with Si, Ge, and GaAs, and is readily available as large-area, epiready wafers at much lower cost in comparison with lattice-matched CdZnTe substrates. The resultant stress due to lattice and thermal mismatch between the HgCdTe epilayer and various substrates has been calculated in this work using the elasticity matrix, and the corresponding stress distribution simulated using ANSYS. The simulated structures were matched by experimental samples involving MBE growth of HgCdTe on GaAs, GaSb, and CdZnTe substrates, and were characterized via reflection high-energy electron diffraction and x-ray diffraction analysis, followed by etch pit density (EPD) analysis. In comparison with other alternative substrates, GaSb is shown to have lower interface stress and lower EPD, rendering it an interesting and promising alternative substrate material for HgCdTe epitaxy.

  10. HgCdTe MWIR Back-Illuminated Electron-Initiated Avalanche Photodiode Arrays

    NASA Astrophysics Data System (ADS)

    Reine, M. B.; Marciniec, J. W.; Wong, K. K.; Parodos, T.; Mullarkey, J. D.; Lamarre, P. A.; Tobin, S. P.; Gustavsen, K. A.; Williams, G. M.

    2007-08-01

    This paper reports data for back-illuminated planar n-on-p HgCdTe electron-initiated avalanche photodiode (e-APD) 4 × 4 arrays with large unit cells (250 × 250 μm2). The arrays were fabricated from p-type HgCdTe films grown by liquid phase epitaxy (LPE) on CdZnTe substrates. The arrays were bump-mounted to fanout boards and characterized in the back-illuminated mode. Gain increased exponentially with reverse bias voltage, and the gain versus bias curves were quite uniform from element to element. The maximum gain measured was 648 at -11.7 V for a cutoff wavelength of 4.06 μm at 160 K. For the same reverse-bias voltage, the gains measured at 160 K for elements with two different cutoff wavelengths (3.54 μm and 4.06 μm at 160 K) show an exponential increase with increasing cutoff wavelength, in agreement with Beck’s empirical model for gain versus voltage and cutoff wavelength in HgCdTe e-APDs. Spot scan data show that both the V = 0 response and the gain at V = -5.0 V are spatially uniform over the large junction area. To the best of our knowledge, these are the first spot scan data for avalanche gain ever reported for HgCdTe e-APDs. Capacitance versus voltage data are consistent with an ideal abrupt junction having a donor concentration equal to the indium concentration in the LPE film.

  11. Investigation of magnetoabsorption at different temperatures in HgTe/CdHgTe quantum-well heterostructures in pulsed magnetic fields

    SciTech Connect

    Platonov, V. V.; Kudasov, Yu. B.; Makarov, I. V.; Maslov, D. A.; Surdin, O. M.; Zholudev, M. S.; Ikonnikov, A. V.; Gavrilenko, V. I.; Mikhailov, N. N.; Dvoretsky, S. A.

    2015-12-15

    The magnetoabsorption in magnetic fields as high as 40 T is investigated at T > 77 K in HgTe/CdHgTe quantum-well heterostructures (d{sub QW} ≈ 8 nm). The spectra reveal two lines associated both with intraband transition from the lower Landau level in the conduction band and with interband transition. It is shown that the band structure in these systems changes from inverted to normal with increasing temperature.

  12. Comparative study of Hg xCd 1-xTe films grown on CdTe thin films previously deposited from two different techniques

    NASA Astrophysics Data System (ADS)

    Ali, A.; Abbas Shah, N.; Maqsood, A.

    2009-04-01

    High quality cadmium telluride (CdTe) thin films were grown on glass substrates with two different techniques, two evaporation source (TES) and closed space sublimation (CSS). Further to the above mercury telluride (HgTe) was then deposited by using single source on both CdTe thin films for obtaining Hg xCd 1-xTe samples. The crystalline structure of the Hg xCd 1-xTe sample grown from CSS-CdTe showed the preferential (1 1 1) orientation with smoother and larger grain size than those of TES-CdTe. The optical transmission for TES-CdTe sample was above 90% in the 1000-1500 nm range whereas it was significantly below 80% for CSS-CdTe sample. The optical transmission for TES-Hg xCd 1-xTe and CSS-Hg xCd 1-xTe was ˜60%. The resistivity at room temperature of TES-CdTe and CSS-CdTe was ˜3.33×10 9 Ω cm and ˜2.20×10 8 Ω cm, respectively, while the resistivity of TES-Hg xCd 1-xTe and CSS-Hg xCd 1-xTe samples was ˜1.73 Ω cm and ˜5.34×10 5 Ω cm, respectively. The comparative study of ternary compound prepared with the above techniques has been carried out for the first time.

  13. HgCdTe heterostructures on Si (310) substrates for midinfrared focal plane arrays

    SciTech Connect

    Yakushev, M. V. Brunev, D. V.; Varavin, V. S.; Vasilyev, V. V.; Dvoretskii, S. A.; Marchishin, I. V.; Predein, A. V.; Sabinina, I. V.; Sidorov, Yu. G.; Sorochkin, A. V.

    2011-03-15

    Results of studies of the molecular beam epitaxial growth of HgCdTe alloys on Si substrates as large as 100 mm in diameter are presented. Optimum conditions for obtaining HgCdTe/Si(310) heterostructures of the device quality for the spectral range of 3-5 {mu}m are determined. The results of measurements and discussion of photoelectric parameters of an infrared photodetector of a format of 320 Multiplication-Sign 256 elements with a step of 30 {mu}m based on a hybrid assembly of a matrix photosensitive cell with a Si multiplexer are presented. A high stability of photodetector parameters to thermocycling from room temperature to liquid-nitrogen temperature is shown.

  14. Development of a HgCdTe photomixer and impedance matched GaAs FET amplifier

    NASA Technical Reports Server (NTRS)

    Shanley, J. F.; Paulauskas, W. A.; Taylor, D. R.

    1982-01-01

    A research program for the development of a 10.6 micron HgCdTe photodiode/GaAs field effect transistor amplifier package for use at cryogenic temperatures (77k). The photodiode/amplifier module achieved a noise equivalent power per unit bandwidth of 5.7 times 10 to the 20th power W/Hz at 2.0 GHz. The heterodyne sensitivity of the HgCdTe photodiode was improved by designing and building a low noise GaAs field effect transistor amplifier operating at 77K. The Johnson noise of the amplifier was reduced at 77K, and thus resulted in an increased photodiode heterodyne sensitivity.

  15. Extending the operating temperature, wavelength and frequency response of HgCdTe heterodyne detectors

    NASA Technical Reports Server (NTRS)

    Spears, D. L.

    1980-01-01

    Near ideal optical heterodyne performance was obtained at GHz IF frequencies in the 10 micrometer wavelength region with liquid nitrogen cooled HgCdTe photodiodes. Heterodyne NEP's as low as 2.7 x 10 to the minus 20th power W/Hz at 100MHz, 5.4 x 10 to the minus 20th power W/Hz at 1.5 GHz, and 9.4 x 19 to the minus 20th power W/Hz at 3 GHz were achieved. Various physical phenomena which occur within a photodiode and affect heterodyne operation were examined in order to assess the feasibility of extending the operating temperature, wavelength, and frequency response of these HgCdTe photomixers.

  16. Linear Mode HgCdTe Avalanche Photodiodes for Photon Counting Applications

    NASA Technical Reports Server (NTRS)

    Sullivan, William, III; Beck, Jeffrey; Scritchfield, Richard; Skokan, Mark; Mitra, Pradip; Sun, Xiaoli; Abshire, James; Carpenter, Darren; Lane, Barry

    2015-01-01

    An overview of recent improvements in the understanding and maturity of linear mode photon counting with HgCdTe electron-initiated avalanche photodiodes is presented. The first HgCdTe LMPC 2x8 format array fabricated in 2011 with 64 micron pitch was a remarkable success in terms of demonstrating a high single photon signal to noise ratio of 13.7 with an excess noise factor of 1.3-1.4, a 7 ns minimum time between events, and a broad spectral response extending from 0.4 micron to 4.2 micron. The main limitations were a greater than 10x higher false event rate than expected of greater than 1 MHz, a 5-7x lower than expected APD gain, and a photon detection efficiency of only 50% when greater than 60% was expected. This paper discusses the reasons behind these limitations and the implementation of their mitigations with new results.

  17. The structural and electronic properties of amorphous HgCdTe from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Zhao, Huxian; Chen, Xiaoshuang; Lu, Jianping; Shu, Haibo; Lu, Wei

    2014-01-01

    Amorphous mercury cadmium telluride (a-MCT) model structures, with x being 0.125 and 0.25, are obtained from first-principles calculations. We generate initial structures by computation alchemy method. It is found that most atoms in the network of amorphous structures tend to be fourfold and form tetrahedral structures, implying that the chemical ordered continuous random network with some coordination defects is the ideal structure for a-MCT. The electronic structure is also concerned. The gap is found to be 0.30 and 0.26 eV for a-Hg0.875Cd0.125Te and a-Hg0.75Cd0.25Te model structures, independent of the composition. By comparing with the properties of crystalline MCT with the same composition, we observe a blue-shift of energy band gap. The localization of tail states and its atomic origin are also discussed.

  18. Magnetoabsorption in narrow-gap HgCdTe epitaxial layers in the terahertz range

    SciTech Connect

    Ikonnikov, A. V. Zholudev, M. S.; Gavrilenko, V. I.; Mikhailov, N. N.; Dvoretskii, S. A.

    2013-12-15

    The magnetoabsorption and photoconductivity spectra are investigated in the terahertz (THz) range at a temperature of T = 4.2 K for n-Hg{sub 1−x}Cd{sub x}Te bulk epitaxial layers of various compositions (both semiconductor and semimetallic) grown by molecular-beam epitaxy. Within the framework of the Kane 8 · 8 model, the electron and hole Landau levels are calculated. It is shown that, in contrast to the results of previous investigations, all observed resonance lines are related to transitions between the Landau levels of free carriers (the cyclotron resonance in the conduction band and the transitions between heavy-hole and electron Landau levels), which is evidence of the high purity and structural perfection of the samples. The possibility of using zero-gap Hg{sub 1−x}Cd{sub x}Te solid solutions as THz photodetectors tunable by magnetic field is shown.

  19. Computer modeling of carrier transport in (Hg,Cd)Te photodiodes

    NASA Astrophysics Data System (ADS)

    Summers, C. J.; Darling, B.; Martin, B. G.

    1986-04-01

    A numerical technique has been used to solve the carrier transport equations for several (Hg,Cd)Te photodiode configurations, namely n+pp+, n+np, and pin. Of particular interest are the fundamental recombination mechanisms of radiative and Auger. Results clearly demonstrate the importance of Auger type 1 and 7 mechanisms on the n and p sides of the junction, respectively, in limiting carrier lifetimes. For example, it was found that for defect-free Hg(1-x)Cd(x)Te alloys with x = 0.2 and hole concentration less than 4 x 10 to the 14th cu cm adjacent to the depletion region, the Auger recombination rate can be reduced below the radiative rate. An analysis of the spatial dependence of the electron mobility shows that the presence of high carrier concentrations and electric field strengths can reduce the mobility and consequently have an effect on the sensitivity and temporal response of the photodiode.

  20. Convective Influence on Radial Segregation During Unidirectional Solidification of the Binary Alloy HgCdTe

    NASA Technical Reports Server (NTRS)

    Watring, D. A.; Gillies, D. C.; Lehoczky, S. L.; Szofran, F. R.; Alexander, H.

    1996-01-01

    In order to simulate the space environment for basic research into the crystal growth mechanism, Hg(0.8)Cd(0.2)Te crystals were grown by the vertical Bridgman-Stockbarger method in the presence of an applied axial magnetic field. The influence of convection, by magneto hydrodynamic damping, on mass transfer in the melt and segregation at the solid-liquid interface was investigated by measuring the axial and radial compositional variations in the grown samples. The reduction of convective mixing in the melt through the application of the magnetic field is found to have a large effect on radial segregation and interface morphology in the grown crystals. Direct comparisons are made with a Hg(0.8)Cd(0.2)Te crystal grown without field and also in the microgravity environment of space during the second United States Microgravity Payload Mission (USMP-2).

  1. Recent progress on HgCdTe at the national laboratory for infrared physics in china

    NASA Astrophysics Data System (ADS)

    Chu, Junhao; Tang, Dingyuan

    1996-08-01

    The characterization of impurities, defects, uniformity and some fundamental properties for the bulk and epitaxial HgCdTe (MCT) material, undoped and doped with Sb, As, Fe, have been investigated recently in the authors’ laboratory by means of photoluminescence, magneto-photoconductivity, quantum capacitance spectroscopy, transport measurements, and other contactless and nonde-structive methods such as the infrared, far-infrared, and millimeter wave measurements. This paper reports a portion of these new results.

  2. Monte Carlo Treatment of Displacement Damage in Bandgap Engineered HgCdTe Detectors

    NASA Technical Reports Server (NTRS)

    Fodness, Bryan C.; Marshall, Paul W.; Reed, Robert A.; Jordan, Thomas M.; Pickel, James C.; Jun, Insoo; Xapsos, Michael A.; Burke, Edward A.

    2003-01-01

    The conclusion are: 1. Description of NIEL calculation for short, mid, and longwave HgCdTe material compositions. 2. Full recoil spectra details captured and analyzed Importance of variance in high Z materials. 3. Can be applied directly to calculate damage distributions in arrays. 4. Future work will provide comparisons of measured array damage with calculated NIEL and damage energy distributions. 5. Technique to assess the full recoil spectrum behavior is extendable to other materials.

  3. Investigation of vaporization and condensation processes of thin layers of CdHgTe from laser erosion plasma in Hg atmosphere

    NASA Astrophysics Data System (ADS)

    Kotlyarchuk, B. K.; Popovych, D. I.; Savchuk, V. K.; Savitsky, V. G.

    1996-04-01

    The article sets out to investigate spatial-time and spectral characteristics of laser erosive vapour-plasma torch (EVT), formed at the time of vaporization of mercury chalcogenides targets. Its influence on the synthesis processes and electrophysical properties of HgTe and CdHgTe layers, condensed in mercury vapour, is described. It is shown, that the laser radiation flux density and Hg vapour pressure in the reaction chamber are dominating factors, which determine the character of gas-dynamic spread, EVT composition and electrophysical characteristics of condensed mercury chalcogenides layers.

  4. Toxic metals (Hg, Cd, and Pb) in fishery products imported into Italy: suitability for human consumption.

    PubMed

    Storelli, Maria M; Normanno, Giovanni; Barone, Grazia; Dambrosio, Angela; Errico, Luigi; Garofalo, Rita; Giacominelli-Stuffler, Roberto

    2012-01-01

    Mercury, cadmium, and lead concentrations were determined in various fishery products (fishes, cephalopod molluscs, and crustaceans) imported into Italy from many European and non-European coastal countries. Considerable differences were found in the concentrations of these metals among the products tested. The highest mean Hg concentration was found in fishes (0.21 μg g(-1) wet weight), whereas cephalopods had the highest mean Cd concentration (0.35 μg g(-1) wet weight). Swordfish (0.80 μg g(-1) wet weight), longtail tuna (0.53 μg g(-1) wet weight), and thornback ray (0.52 μg g(-1) wet weight) had the highest concentrations of Hg, whereas maximum Cd concentrations were found in samples of common cuttlefish (0.85 μg g(-1) wet weight) and common octopus (0.64 μg g(-1) wet weight). The majority of the samples analyzed were in compliance with European Union legislation, except for a few cases. The calculated mean weekly intakes of Hg, Cd, and Pb through consumption of the fishery products tested were all below the legislated respective provisional tolerable weekly intakes. In general, the samples analyzed were considered safe to eat with regard to the metal concentrations found and the allowable intakes based on legislation. Nevertheless, the consumption of some species may be of significant importance for consumer health. PMID:22221377

  5. Thermophysical Properties and Structural Transition of Hg(0.8)Cd(0.2)Te Melt

    NASA Technical Reports Server (NTRS)

    Li, C.; Scripa, R. N.; Ban, H.; Lin, B.; Su, C.; Lehoczky, S. L.

    2004-01-01

    Thermophysical properties, namely, density, viscosity, and electrical conductivity of Hg(sub o.8)Cd(sub 0.2)Te melt were measured as a function of temperature. A pycnometric method was used to measure the melt density in the temperature range of 1072 to 1122 K. The viscosity and electrical conductivity were simultaneously determined using a transient torque method from 1068 to 1132 K. The density result from this study is within 0.3% of the published data. However, the current viscosity result is approximately 30% lower than the existing data. The electrical conductivity of Hg(sub o.8)Cd(sub 0.2)Te melt as a function of temperature, which is not available in the literature, is also determined. The analysis of the temperature dependent electrical conductivity and the relationship between the kinematic viscosity and density indicated that the structure of the melt appeared to be homogeneous when the temperature was above 1090 K. A structural transition occurred in the Hg(sub 0.8)Cd(0.2)Te melt as the temperature was decreased from 1090 K to the liquidus temperature.

  6. Interactions between photoexcited NIR emitting CdHgTe quantum dots and graphene oxide

    NASA Astrophysics Data System (ADS)

    Jagtap, Amardeep M.; Varade, Vaibhav; Konkena, Bharathi; Ramesh, K. P.; Chatterjee, Abhijit; Banerjee, Arup; Pendyala, Naresh Babu; Koteswara Rao, K. S. R.

    2016-02-01

    Hydrothermally grown mercury cadmium telluride quantum dots (CdHgTe QDs) are decorated on graphene oxide (GO) sheets through physisorption. The structural change of GO through partial reduction of oxygen functional groups is observed with X-ray photoelectron spectroscopy in GO-QDs composites. Raman spectroscopy provides relatively a small change (˜1.1 times) in D/G ratio of band intensity and red shift in G band from 1606 cm-1 to 1594 cm-1 in GO-CdHgTe QDs (2.6 nm) composites, which indicates structural modification of GO network. Steady state and time resolved photoluminescence (PL) spectroscopy shows the electronic interactions between photoexcited near infrared emitting CdHgTe QDs and GO. Another interesting observation is PL quenching in the presence of GO, and it is quite effective in the case of smaller size QDs (2.6 nm) compared to the larger size QDs (4.2 nm). Thus, the observed PL quenching is attributed to the photogenerated electron transfer from QDs to GO. The photoexcited electron transfer rate decreases from 2.2 × 109 to 1.5 × 108 s-1 with increasing particle size from 2.6 to 4.2 nm. Photoconductivity measurements on QDs-GO composite devices show nearly 3 fold increase in the current density under photo-illumination, which is a promising aspect for solar energy conversion and other optoelectronic applications.

  7. Update on Linear Mode Photon Counting with the HgCdTe Linear Mode Avalanche Photodiode

    NASA Technical Reports Server (NTRS)

    Beck, Jeffrey D.; Kinch, Mike; Sun, Xiaoli

    2014-01-01

    The behavior of the gain-voltage characteristic of the mid-wavelength infrared cutoff HgCdTe linear mode avalanche photodiode (e-APD) is discussed both experimentally and theoretically as a function of the width of the multiplication region. Data are shown that demonstrate a strong dependence of the gain at a given bias voltage on the width of the n- gain region. Geometrical and fundamental theoretical models are examined to explain this behavior. The geometrical model takes into account the gain-dependent optical fill factor of the cylindrical APD. The theoretical model is based on the ballistic ionization model being developed for the HgCdTe APD. It is concluded that the fundamental theoretical explanation is the dominant effect. A model is developed that combines both the geometrical and fundamental effects. The model also takes into account the effect of the varying multiplication width in the low bias region of the gain-voltage curve. It is concluded that the lower than expected gain seen in the first 2 × 8 HgCdTe linear mode photon counting APD arrays, and higher excess noise factor, was very likely due to the larger than typical multiplication region length in the photon counting APD pixel design. The implications of these effects on device photon counting performance are discussed.

  8. Single-Photon-Sensitive HgCdTe Avalanche Photodiode Detector

    NASA Technical Reports Server (NTRS)

    Huntington, Andrew

    2013-01-01

    The purpose of this program was to develop single-photon-sensitive short-wavelength infrared (SWIR) and mid-wavelength infrared (MWIR) avalanche photodiode (APD) receivers based on linear-mode HgCdTe APDs, for application by NASA in light detection and ranging (lidar) sensors. Linear-mode photon-counting APDs are desired for lidar because they have a shorter pixel dead time than Geiger APDs, and can detect sequential pulse returns from multiple objects that are closely spaced in range. Linear-mode APDs can also measure photon number, which Geiger APDs cannot, adding an extra dimension to lidar scene data for multi-photon returns. High-gain APDs with low multiplication noise are required for efficient linear-mode detection of single photons because of APD gain statistics -- a low-excess-noise APD will generate detectible current pulses from single photon input at a much higher rate of occurrence than will a noisy APD operated at the same average gain. MWIR and LWIR electron-avalanche HgCdTe APDs have been shown to operate in linear mode at high average avalanche gain (M > 1000) without excess multiplication noise (F = 1), and are therefore very good candidates for linear-mode photon counting. However, detectors fashioned from these narrow-bandgap alloys require aggressive cooling to control thermal dark current. Wider-bandgap SWIR HgCdTe APDs were investigated in this program as a strategy to reduce detector cooling requirements.

  9. Phytoremediation of Hg and Cd from industrial effluents using an aquatic free floating macrophyte Azolla pinnata.

    PubMed

    Rai, Prabhat Kumar

    2008-01-01

    The level of heavy metal pollution in Singrauli, an industrial region in India, was assessed and the phytoremediation capacity of a small water fern, Azolla pinnata R.BR (Azollaceae), was observed to purify waters polluted by two heavy metals, i.e., mercury (Hg) and cadmium (Cd) under a microcosm condition. Azolla pinnata is endemic to India and is an abundant and easy-growing free-floating water fern usually found in the rice fields, polluted ponds, and reservoirs of India. The fern was grown in 24 40-L aquariums containing Hg2+ and Cd2+ ions each in concentrations of 0.5, 1.0, and 3.0 mgL(-1) during the course of this study. The study revealed an inhibition of Azolla pinnata growth by 27.0-33.9% with the highest in the presence of Hg (II) ions at 0.5 mgL(-1) in comparison to the control After 13 days of the experiment, metal contents in the solution were decreased up to 70-94%. In the tissues of Azolla pinnata, the concentration of selected heavy metals during investigation was recorded between 310 and 740 mgKg(-1) dry mass, with the highest levelfoundfor Cd (II) treatment at 3.0 mgL(-1) containing a metal solution. PMID:19260224

  10. Density, Electrical Conductivity and Viscosity of Hg(0.8)Cd(0.2)Te Melt

    NASA Technical Reports Server (NTRS)

    Li, C.; Scripa, R. N.; Ban, H.; Su, C.-H.; Lehoczky, S. L.

    2004-01-01

    The density, viscosity, and electrical conductivity of Hg(0.8)Cd(0.2)Te melt were measured as a function of temperature. A pycnometric method was used to measure the melt density in the temperature range of 1072 to 1122 K. The viscosity and electrical conductivity were determined using a transient torque method from 1068 to 1132 K. The density result from this study is within 0.3% of the published data. However, the current viscosity result is approximately 30% lower than the existing data. The electrical conductivity of Hg(0.8)Cd(0.2)Te melt as a function of temperature, which is not available in the literature, is also determined. The analysis of the temperature dependent electrical conductivity and the relationship between the kinematic viscosity and density indicated that the structure of the melt appeared to be homogeneous when the temperature was above 1090 K. A structural transition occurred in the Hg(0.8)Cd(0.2)Te melt as the temperature was decreased to below 1090 K

  11. Ultrasensitive electrochemical sensor for Hg(2+) by using hybridization chain reaction coupled with Ag@Au core-shell nanoparticles.

    PubMed

    Li, Zongbing; Miao, Xiangmin; Xing, Ke; Peng, Xue; Zhu, Aihua; Ling, Liansheng

    2016-06-15

    A novel electrochemical biosensor for Hg(2+) detection was reported by using DNA-based hybridization chain reaction (HCR) coupled with positively charged Ag@Au core-shell nanoparticles ((+)Ag@Au CSNPs) amplification. To construct the sensor, capture probe (CP ) was firstly immobilized onto the surface of glass carbon electrode (GCE). In the presence of Hg(2+), the sandwiched complex can be formed between the immobilized CP on the electrode surface and the detection probe (DP) modified on the gold nanoparticles (AuNPs) based on T-Hg(2+)-T coordination chemistry. The carried DP then opened two ferrocene (Fc) modified hairpin DNA (H1 and H2) in sequence and propagated the happen of HCR to form a nicked double-helix. Numerous Fc molecules were formed on the neighboring probe and produced an obvious electrochemical signal. Moreover, (+)Ag@Au CSNPs were assembly onto such dsDNA polymers as electrochemical signal enhancer. Under optimal conditions, such sensor presents good electrochemical responses for Hg(2+) detection with a detection limit of 3.6 pM. Importantly, the methodology has high selectivity for Hg(2+) detection. PMID:26852203

  12. Ultrasensitive electrochemical sensor for Hg(2+) by using hybridization chain reaction coupled with Ag@Au core-shell nanoparticles.

    PubMed

    Li, Zongbing; Miao, Xiangmin; Xing, Ke; Peng, Xue; Zhu, Aihua; Ling, Liansheng

    2016-06-15

    A novel electrochemical biosensor for Hg(2+) detection was reported by using DNA-based hybridization chain reaction (HCR) coupled with positively charged Ag@Au core-shell nanoparticles ((+)Ag@Au CSNPs) amplification. To construct the sensor, capture probe (CP ) was firstly immobilized onto the surface of glass carbon electrode (GCE). In the presence of Hg(2+), the sandwiched complex can be formed between the immobilized CP on the electrode surface and the detection probe (DP) modified on the gold nanoparticles (AuNPs) based on T-Hg(2+)-T coordination chemistry. The carried DP then opened two ferrocene (Fc) modified hairpin DNA (H1 and H2) in sequence and propagated the happen of HCR to form a nicked double-helix. Numerous Fc molecules were formed on the neighboring probe and produced an obvious electrochemical signal. Moreover, (+)Ag@Au CSNPs were assembly onto such dsDNA polymers as electrochemical signal enhancer. Under optimal conditions, such sensor presents good electrochemical responses for Hg(2+) detection with a detection limit of 3.6 pM. Importantly, the methodology has high selectivity for Hg(2+) detection.

  13. Radioactivity in HgCdTe devices: potential source of "snowballs"

    NASA Astrophysics Data System (ADS)

    McCullough, P.

    2009-12-01

    We hypothesize that the "snowballs" observed in HgCdTe infrared detectors are caused by natural radioactivity in the devices themselves. As characterized by Hilbert (2009) in the WFC3 flight IR array (FPA165), "snowballs" are transient events that instantaneously saturate a few pixels and deposit a few hundred thousand electrons over a ~5-pixel (~100-um) diameter region. In 2008, prior to flight of detector FPA165, Hilbert (2009) detected 21 snowballs during thermal vaccum test three (TV3) and inferred a rate of ~1100 ± 200 snowballs per year per cm2 of the HgCdTe detector. Alpha particles emitted from either (or both) naturally radioactive thorium and/or uranium, at ~1 ppm concentrations within the device, can explain the observed characteristics of the "snowballs." If thorium is present, up to four distinctly observable snowballs should appear at the same location on the pixel array over the course of many years. While the indium in the bump bonds is almost entirely the radioactive isotope In-115, and 12% of the cadmium is naturally radioactive Cd-113, both of those emit only betas, which are too penetrating and not energetic enough to match the observed characteristics of "snowballs." Also, the Cd-113 emission rate is much less than that of the observed snowballs.

  14. Molecular beam epitaxy of CdTe on GaAs substrates and HgCdTe on CdTe/GaAs alternate substrates

    SciTech Connect

    Lange, M.D.

    1993-12-31

    Two aspects of molecular-beam epitaxy (MBE) of the infrared sensitive semiconductor Hg{sub 1-x}Cd{sub x}Te were investigated: control of the substrate temperature by infrared pyrometer in addition to rear thermocouple, and improvement of CdTe/GaAs alternate substrates. Pyrometer behavior was recorded while controlling the temperatures of growing Hg{sub 1-x}Cd{sub x}Te with a frontal thermocoupled that contacted their surfaces. These recordings were interpreted in terms of emission and absorption, transmission and reflection, and thin-film interference. Based on these results, temperature control by rear thermocouple was reexamined, resulting in improved technique of that temperature control method as well. A temperature control technique combining both the pyrometer and the rear thermocoupled was developed; and evidence is presented and the rear thermocouple was developed; and evidence is presented for the resulting improvement in crystalline and electrical quality of MBE Hg{sub 1-x}Cd{sub x}Te. Investigations of Hg{sub 1-x}Cd{sub x}Te MBE onto more afforadable, larger, and more rugged CdTe/GaAs alternate substrates focused chiefly on improving the MBE of CdTe onto GaAs. This heteroepitaxy was studied primarily in terms of the influences on CdTe crystalline quality of the mismatches in bonding character, lattice spacing, thermal expansion, and charge imbalance between these two zincblende crystals. A novel dual epitaxial relationship, CdTe(331)B/GaAs(112)B and CdTe (112)B/GaAs(112)B, was discovered in these investigations; and the nonparellel orientation proves superior to the parallel orientation and to both orientations of the previously known CdTe(111)B/GaAs(001) and CdTe(001)/GaAs(001) dual epitaxial relationship. A charge imbalance model, applied to these four heterointerfaces, predicts the balancing of that charge by movement of electrons into or out of the heterointerfacial dangling bonds, which exist due to the lattice mismatch.

  15. Structural and optical properties of core–shell Ag{sub 2}S/HgS nanostructures

    SciTech Connect

    Basyach, Priyanka; Choudhury, Amarjyoti

    2013-07-15

    Graphical abstract: - Highlights: • Core–shell Ag{sub 2}S/HgS nanostructures are successfully synthesized. • The particle size and the structure were confirmed through TEM images. • The absorbance analysis reveals red shift with increasing shell concentration. • A transition from TYPE 1 to TYPE 2 core–shell nanostructure is observed. - Abstract: Here we report on a two-step synthesis route for fabrication of core–shell Ag{sub 2}S/HgS nanostructures. Nanoscale Ag{sub 2}S semiconductors are prepared by a standard redox reaction using AgNO{sub 3} and CS{sub 2} as the reactants in PVP. HgS layers are developed on Ag{sub 2}S cores through S-S bonding at the interface separating the two systems. The properties of these core–shell nanostructures are studied via various spectroscopic and microscopic tools like UV–Vis absorption spectra, photoluminescence spectra, X-ray diffraction pattern and transmission electron microscopic images. Change in optical properties is observed while varying the shell thickness in the sample. A detailed study on the luminescence properties reveal transition from TYPE 1 to TYPE 2 core–shell nanostructures is observed with increasing shell thickness.

  16. LPE growth and characterization of 1.3 μm (Hg, Cd)Te layers

    NASA Astrophysics Data System (ADS)

    Janik, E.; Ferah, M.; Legros, R.; Triboulet, R.; Brossat, T.; Riant, Y.

    1985-08-01

    The growth of epitaxial layers of Cd xHg 1- xTe with x=0.7, suitable for optoelectronic applications, is obtained. The growth is performed by LPE from a Te-rich solution in a closed tube tipping system, on hydroplane polished CdTe or Cd 1- yZn yTe substrates. The growth apparatus and procedure are described. Layers of thickness 10-40 μm, grown at 500-600°C, were obtained. Attention was paid mainly to the surface morphological quality and good decantation from the layers. The surface morphology was observed by Nomarski contrast photography, the profile concentration measured by electron microprobe, and back reflection Laue patterns are presented also. We report, also, the results of measurements of the optical and electrical parameters of grown layers and the characteristics of photodiodes made from them.

  17. Possible link between Hg and Cd accumulation in the brain of long-finned pilot whales (Globicephala melas).

    PubMed

    Gajdosechova, Zuzana; Brownlow, Andrew; Cottin, Nicolas T; Fernandes, Mariana; Read, Fiona L; Urgast, Dagmar S; Raab, Andrea; Feldmann, Jörg; Krupp, Eva M

    2016-03-01

    The bioaccumulation of metals was investigated by analysis of liver, kidney, muscle and brain tissue of a pod of 21 long-finned pilot whales (Globicephala melas) of all ages stranded in Scotland, UK. The results are the first to report cadmium (Cd) passage through the blood-brain barrier of pilot whales and provide a comprehensive study of the long-term (up to 35 years) mammalian exposure to the environmental pollutants. Additionally, linear accumulation of mercury (Hg) was observed in all studied tissues, whereas for Cd this was only observed in the liver. Total Hg concentration above the upper neurochemical threshold was found in the sub-adult and adult brains and methylmercury (MeHg) of 2.2mg/kg was found in the brain of one individual. Inter-elemental analysis showed significant positive correlations of Hg with selenium (Se) and Cd with Se in all studied tissues. Furthermore, differences in the elemental concentrations in the liver and brain tissues were found between juvenile, sub-adult and adult groups. The highest concentrations of manganese, iron, zinc, Se, Hg and MeHg were noted in the livers, whereas Cd predominantly accumulated in the kidneys. High concentrations of Hg and Cd in the tissues of pilot whales presented in this study reflect ever increasing toxic stress on marine mammals.

  18. A dry method to synthesize dendritic Ag2Se nanostructures utilizing CdSe quantum dots and Ag thin films.

    PubMed

    Hu, Lian; Zhang, Bingpo; Xu, Tianning; Li, Ruifeng; Wu, Huizhen

    2015-01-01

    Dendritic Ag2Se nanostructures are synthesized in a dry environment by UV irradiating the hybrids composed of CdSe quantum dots (QDs) and silver (Ag). UV irradiation on CdSe QDs induces a photooxidation effect on the QD surface and leads to the formation of SeO2 components. Then SeO2 reacts with the Ag atoms in either Ag film or QD layer to produce the Ag2Se. The growth mechanism of Ag2Se dendrites on solid Ag films is explored and explained by a diffusion limited aggregation model in which the QD layer provides enough freedom for Ag2Se motion. Since the oxidation of the CdSe QDs is the critical step for the Ag2Se dendrites formation this dry chemical interaction between QDs and Ag film can be applied in the study of the QD surface chemical properties. With this dry synthesis method, the Ag2Se dendrites can also be facilely formed at the designed area on Ag substrates. PMID:25483981

  19. A dry method to synthesize dendritic Ag2Se nanostructures utilizing CdSe quantum dots and Ag thin films

    NASA Astrophysics Data System (ADS)

    Hu, Lian; Zhang, Bingpo; Xu, Tianning; Li, Ruifeng; Wu, Huizhen

    2015-01-01

    Dendritic Ag2Se nanostructures are synthesized in a dry environment by UV irradiating the hybrids composed of CdSe quantum dots (QDs) and silver (Ag). UV irradiation on CdSe QDs induces a photooxidation effect on the QD surface and leads to the formation of SeO2 components. Then SeO2 reacts with the Ag atoms in either Ag film or QD layer to produce the Ag2Se. The growth mechanism of Ag2Se dendrites on solid Ag films is explored and explained by a diffusion limited aggregation model in which the QD layer provides enough freedom for Ag2Se motion. Since the oxidation of the CdSe QDs is the critical step for the Ag2Se dendrites formation this dry chemical interaction between QDs and Ag film can be applied in the study of the QD surface chemical properties. With this dry synthesis method, the Ag2Se dendrites can also be facilely formed at the designed area on Ag substrates.

  20. Interview with Paul W. Kruse on the Early History of HgCdTe, Conducted on October 22, 1980

    NASA Astrophysics Data System (ADS)

    Reine, Marion B.

    2015-09-01

    This paper presents an interview with Dr Paul W. Kruse (1927-2012) on the early history of the semiconductor alloy mercury cadmium telluride (HgCdTe or Hg1- x Cd x Te) at the Honeywell Corporate Research Center near Minneapolis, Minnesota. Conducted on October 22, 1980, the interview covers two main areas. One area is the story of how the HgCdTe research effort came about at the Honeywell Research Center in the early 1960s, what technical choices were made and when, and what technical challenges were overcome and how. The other area is the organization, culture, environment and personnel at the Honeywell Research Center that made the early HgCdTe research programs so successful. HgCdTe has emerged as the highest-performance, most widely applicable infrared detector material. HgCdTe continues to satisfy a broad variety of advanced military and space applications. It is illustrative to look back on the early history of this remarkable semiconductor alloy to help to understand why its technological development as an infrared detector has been so successful.

  1. High-Performance MWIR HgCdTe on Si Substrate Focal Plane Array Development

    NASA Astrophysics Data System (ADS)

    Bommena, R.; Ketharanathan, S.; Wijewarnasuriya, P. S.; Dhar, N. K.; Kodama, R.; Zhao, J.; Buurma, C.; Bergeson, J. D.; Aqariden, F.; Velicu, S.

    2015-09-01

    The development of low noise-equivalent differential temperature (NEDT), high-operability midwave infrared (MWIR) focal plane arrays (FPAs) fabricated from molecular beam epitaxial (MBE)-grown HgCdTe on Si-based substrates is reported. High-quality n-type MWIR HgCdTe layers with a cutoff wavelength of 4.90 μm at 77 K and a carrier concentration of 1-2 × 1015 cm-3 were grown on CdTe/Si substrates by MBE. Highly uniform composition and thickness over 3-inch areas were demonstrated, and low surface defect densities (voids ~5 × 102 cm-2, micro-defects ~5 × 103 cm-2) and etch pit density (~3.5 × 106 cm-2) were measured. This material was used to fabricate 320 × 256, 30 μm pitch FPAs with planar device architecture; arsenic implantation was used to achieve p-type doping. Radiometric and noise characterization was also performed. A low NEDT of 13.8 m K at 85 K for a 1 ms integration time with f/#2 optics was measured. The NEDT operability was 99% at 120 K with a mean dark current noise of 8.14 × 10-13 A/pixel. High-quality thermal images were obtained from the FPA up to a temperature of 150 K.

  2. Cytidine-stabilized gold nanocluster as a fluorescence turn-on and turn-off probe for dual functional detection of Ag(+) and Hg(2+).

    PubMed

    Zhang, Yuanyuan; Jiang, Hui; Wang, Xuemei

    2015-04-22

    In this study, we have developed a label-free, dual functional detection strategy for highly selective and sensitive determination of aqueous Ag(+) and Hg(2+) by using cytidine stabilized Au NCs and AuAg NCs as fluorescent turn-on and turn off probes, respectively. The Au NCs and AuAg NCs showed a remarkably rapid response and high selectivity for Ag(+) and Hg(2+) over other metal ions, and relevant detection limit of Ag(+) and Hg(2+) is ca. 10 nM and 30 nM, respectively. Importantly, the fluorescence enhanced Au NCs by doping Ag(+) can be conveniently reusable for the detection of Hg(2+) based on the corresponding fluorescence quenching. The sensing mechanism was based on the high-affinity metallophilic Hg(2+)-Ag(+) interaction, which effectively quenched the fluorescence of AuAg NCs. Furthermore, these fluorescent nanoprobes could be readily applied to Ag(+) and Hg(2+) detection in environmental water samples, indicating their possibility to be utilized as a convenient, dual functional, rapid response, and label-free fluorescence sensor for related environmental and health monitoring.

  3. High Resolution X-ray Diffraction Studies of MBE-Grown HgCdTe Layers on Bulk-Grown CdZnTe Substrate

    NASA Astrophysics Data System (ADS)

    Amarasinghe, Priyanthi M.; Qadri, Syed B.; Wijewarnasuriya, Priyalal S.

    2015-08-01

    The structural properties of molecular beam epitaxially (MBE)-grown Hg1- x Cd x Te epilayers on CdZnTe (211) substrate have been investigated using high-resolution x-ray topography and rocking curves. High-resolution x-ray diffraction 2 θ- θ scans of (422) reflections were utilized in calculating the out-of-plane lattice parameters of the HgCdTe layer and the CdZnTe substrate. The lattice strain of the HgCdTe layer was evaluated using the in-plane measurements of the (311) reflection. Etching seemed to improve the surface of the substrate by removing any damage caused by polishing or any post-processing. In spite of some localized line dislocations, a remarkable quality of the MBE-grown HgCdTe layer was observed. The full width at half maximum values of the HgCdTe layer and the CdZnTe substrate were determined as 43 arc-s and 16.2 arc-s, respectively.

  4. Determination of in vitro bioaccessibility of Pb, As, Cd and Hg in selected traditional Indian medicines

    PubMed Central

    Jayawardene, Innocent; Saper, Robert; Lupoli, Nicola; Sehgal, Anusha; Wright, Robert O.; Amarasiriwardena, Chitra

    2011-01-01

    In vitro bioaccessibility of Pb, As, Cd and Hg in five traditional Indian medicine samples was measured as a determinant of bioavailability. The method is based on simulation of human digestion in the passage of material from the gastric to intestinal portions of the gastrointestinal tract. Total concentration and concentration in extracts from gastric and intestinal phases were analyzed for Pb, As and Cd by dynamic reaction cell inductively coupled plasma mass spectrometry (DRC-ICP-MS) and for Hg by direct mercury analyzer (DMA). Total lead ranged from 1.9 to 36000 µg g−1. In each of the samples bioaccessibility of lead was significantly higher (range 28–88%) in the gastric phase than in the intestinal phase (range 1.4–75.4%). Only Ekangvir Ras had measurable arsenic (304 µg g−1). Its bioaccessibility in the gastric phase and intestinal phase was 82.6% and 78.1%, respectively. Only Ayu-Nephro-Tone had measurable cadmium (14.4 µg g−1). Its bioaccessibility in the gastric phase and intestinal phase was 80.5% and 2.2%, respectively. Three samples had measurable mercury (range 37 µg g−1–10000 µg g−1). Mercury in these samples was not bioaccessible. For the samples with measurable amount of metal, the estimated daily amount of bioaccessible (EDAB) metal was calculated. When compared with the most liberal published safety guideline, EDAB-Pb in Mahayograj Guggulu and Ekangvir Ras were 37 and 45 fold greater. When compared with the most conservative published safety guideline, all samples had higher EDAB-Pb or EDAB-As than the suggested limits. The EDAB-Cd and EDAB-Hg were acceptably below published safety limits. PMID:21643429

  5. Dry etched SiO2 Mask for HgCdTe Etching Process

    NASA Astrophysics Data System (ADS)

    Chen, Y. Y.; Ye, Z. H.; Sun, C. H.; Deng, L. G.; Zhang, S.; Xing, W.; Hu, X. N.; Ding, R. J.; He, L.

    2016-09-01

    A highly anisotropic etching process with low etch-induced damage is indispensable for advanced HgCdTe (MCT) infrared focal plane array (IRFPA) detectors. The inductively coupled plasma (ICP) enhanced reactive ion etching technique has been widely adopted in manufacturing HgCdTe IRFPA devices. An accurately patterned mask with sharp edges is decisive to accomplish pattern duplication. It has been reported by our group that the SiO2 mask functions well in etching HgCdTe with high selectivity. However, the wet process in defining the SiO2 mask is limited by ambiguous edges and nonuniform patterns. In this report, we patterned SiO2 with a mature ICP etching technique, prior to which a thin ZnS film was deposited by thermal evaporation. The SiO2 film etching can be terminated at the auto-stopping point of the ZnS layer thanks to the high selectivity of SiO2/ZnS in SF6 based etchant. Consequently, MCT etching was directly performed without any other treatment. This mask showed acceptable profile due to the maturity of the SiO2 etching process. The well-defined SiO2 pattern and the etched smooth surfaces were investigated with scanning electron microscopy and atomic force microscope. This new mask process could transfer the patterns exactly with very small etch-bias. A cavity with aspect-ratio (AR) of 1.2 and root mean square roughness of 1.77 nm was achieved first, slightly higher AR of 1.67 was also get with better mask profile. This masking process ensures good uniformity and surely benefits the delineation of shrinking pixels with its high resolution.

  6. Contribution of the graded region of a HgCdTe diode to its saturation current

    NASA Technical Reports Server (NTRS)

    Schacham, S. E.; Finkman, E.

    1990-01-01

    Experimental results show that the contribution of the graded region to the current of Hg(1-x)Cd(x)Te diodes is not negligible, as compared to that of the p type bulk. The theoretical analysis reveals the influence of the electric field present outside the depletion region on the current generated by the graded region. The analysis shows the importance of the lifetime profile in the graded region, which is a function of the specific recombination mechanism and its dependence on the local dopant concentration. The effect of parameters such as substrate concentration, surface concentration, and junction depth on this current is discussed.

  7. Evidence of non-local impact ionization in CNT and HgCdTe

    NASA Astrophysics Data System (ADS)

    Marsland, J. S.; Atanu, A. G.

    2009-11-01

    Two aspects of the non-local nature of impact ionization, dead space and resonance, are investigated. The very small excess noise factor measured for mercury cadmium telluride photodiodes can only be explained if the hole to electron ionization coefficient ratio, k, is very small and the impact ionization dead space is also considered. A maximum value of k for HgCdTe is estimated in this paper. In addition, recent measurements of the reverse photocurrent in single wall carbon nanotubes show a well defined flat region at a multiplication of 1.6. This is argued to be evidence for resonant behaviour in impact ionization for carbon nanotubes.

  8. Intrinsic Spin Hall Effect Induced by Quantum Phase Transition in HgCdTe Quantum Wells

    SciTech Connect

    Yang, Wen; Chang, Kai; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-03-19

    Spin Hall effect can be induced both by the extrinsic impurity scattering and by the intrinsic spin-orbit coupling in the electronic structure. The HgTe/CdTe quantum well has a quantum phase transition where the electronic structure changes from normal to inverted. We show that the intrinsic spin Hall effect of the conduction band vanishes on the normal side, while it is finite on the inverted side. This difference gives a direct mechanism to experimentally distinguish the intrinsic spin Hall effect from the extrinsic one.

  9. Conceptual design and applications of HgCdTe infrared photodiodes for heterodyne systems

    NASA Technical Reports Server (NTRS)

    Sirieix, M. B.; Hofheimer, H.

    1980-01-01

    The significance of HgCdTe photodiodes are discussed relative to their existance in heterodyne detection systems operating in the 9 to 11 micrometer CO2 laser wavelength region. Their successful fabrication as well as the physical properties of the materials are described. The implementation of controlled industrial processes are reported with emphasis on the yield of predictable and repeatable detector characteristics to the discriminating systems, demands for high cutoff frequencies, quantum efficiency, and reliability. The most salient production steps and diode characteristics are presented. Measured results from production units are also given.

  10. Relativistic M-subshell radiationless transition probabilities and energies for Zn, Cd and Hg

    SciTech Connect

    Sampaio, J.M.; Parente, F.; Indelicato, P.; Marques, J.P.

    2014-09-15

    Theoretical calculations of radiationless transition probabilities and energies for M-subshell vacancies in Zn, Cd, and Hg are tabulated using the Dirac–Fock method. Transition probabilities between an initial vacancy state and a final two-vacancies state are presented for each initial and final atomic angular momentum quantum number. Calculations were performed in the single configuration approach with the Breit interaction, self-energy and (Uehling) vacuum polarization corrections included in the self-consistent method. Higher-order retardation corrections and QED effects were also included as perturbations.

  11. High-sensitivity assay for Hg (II) and Ag (I) ion detection: A new class of droplet digital PCR logic gates for an intelligent DNA calculator.

    PubMed

    Cheng, Nan; Zhu, Pengyu; Xu, Yuancong; Huang, Kunlun; Luo, Yunbo; Yang, Zhansen; Xu, Wentao

    2016-10-15

    The first example of droplet digital PCR logic gates ("YES", "OR" and "AND") for Hg (II) and Ag (I) ion detection has been constructed based on two amplification events triggered by a metal-ion-mediated base mispairing (T-Hg(II)-T and C-Ag(I)-C). In this work, Hg(II) and Ag(I) were used as the input, and the "true" hierarchical colors or "false" green were the output. Through accurate molecular recognition and high sensitivity amplification, positive droplets were generated by droplet digital PCR and viewed as the basis of hierarchical digital signals. Based on this principle, YES gate for Hg(II) (or Ag(I)) detection, OR gate for Hg(II) or Ag(I) detection and AND gate for Hg(II) and Ag(I) detection were developed, and their sensitively and selectivity were reported. The results indicate that the ddPCR logic system developed based on the different indicators for Hg(II) and Ag(I) ions provides a useful strategy for developing advanced detection methods, which are promising for multiplex metal ion analysis and intelligent DNA calculator design applications.

  12. High-sensitivity assay for Hg (II) and Ag (I) ion detection: A new class of droplet digital PCR logic gates for an intelligent DNA calculator.

    PubMed

    Cheng, Nan; Zhu, Pengyu; Xu, Yuancong; Huang, Kunlun; Luo, Yunbo; Yang, Zhansen; Xu, Wentao

    2016-10-15

    The first example of droplet digital PCR logic gates ("YES", "OR" and "AND") for Hg (II) and Ag (I) ion detection has been constructed based on two amplification events triggered by a metal-ion-mediated base mispairing (T-Hg(II)-T and C-Ag(I)-C). In this work, Hg(II) and Ag(I) were used as the input, and the "true" hierarchical colors or "false" green were the output. Through accurate molecular recognition and high sensitivity amplification, positive droplets were generated by droplet digital PCR and viewed as the basis of hierarchical digital signals. Based on this principle, YES gate for Hg(II) (or Ag(I)) detection, OR gate for Hg(II) or Ag(I) detection and AND gate for Hg(II) and Ag(I) detection were developed, and their sensitively and selectivity were reported. The results indicate that the ddPCR logic system developed based on the different indicators for Hg(II) and Ag(I) ions provides a useful strategy for developing advanced detection methods, which are promising for multiplex metal ion analysis and intelligent DNA calculator design applications. PMID:27140307

  13. Effect of Lattice Mismatch on HgCdTe LPE Film Surface Morphology

    NASA Astrophysics Data System (ADS)

    Sun, Quanzhi; Wei, Yanfeng; Zhang, Juan; Sun, Ruiyun

    2016-09-01

    A new type of crystal defect, which we call a rough structure, is reported in this work. The rough structure appears in large lattice mismatch regions whereas a normal surface appears in the regions where there is a small lattice mismatch on the same substrate. Experiments proved that under normal liquid-phase epitaxy growth conditions, the appearance of a rough structure is related to the lattice mismatch between the substrate and the film. Statistical data indicated that for Hg1- x Cd x Te films with different Cd compositions x, a rough structure appeared on the film surface when the lattice mismatch was outside the range of 0.02-0.11%. The rough structure may result from the misfit dislocations resulting from strain relaxation. When there was a small surface crystal orientation deviation from (111), dense growth ripples appeared instead of the rough structure. A super-flat surface sometimes appeared inside the rough structure regions.

  14. Fast, high-yield synthesis of amphiphilic Ag nanoclusters and the sensing of Hg2+ in environmental samples

    NASA Astrophysics Data System (ADS)

    Xia, Nan; Yang, Jie; Wu, Zhikun

    2015-05-01

    We report the high-yield (74%) synthesis of Ag30(Capt)18 (abbreviated as Ag30) in a very time-saving fashion (half an hour). The cluster composition was determined by high-resolution mass spectrometry combined with TG analysis, and the structure was probed by 1D and 2D NMR. Interestingly, the nanoclusters can dissolve in water and methanol, as well as in most organic solvents such as ethanol, acetone, acetonitrile, dichloromethane and ethyl acetate with the assistance of acetic acid. Such a good solubility in a range of various polar solvents was not reported previously in nanoclusters' research and is important for applications. An important result from this work is that Ag30 can sense a low concentration of Hg2+ in environmental samples (including lake water and soil solution), indicating that Ag30 can be a potential colorimetric probe for Hg2+. The sensing mechanism was revealed to be related to the anti-galvanic reduction process.We report the high-yield (74%) synthesis of Ag30(Capt)18 (abbreviated as Ag30) in a very time-saving fashion (half an hour). The cluster composition was determined by high-resolution mass spectrometry combined with TG analysis, and the structure was probed by 1D and 2D NMR. Interestingly, the nanoclusters can dissolve in water and methanol, as well as in most organic solvents such as ethanol, acetone, acetonitrile, dichloromethane and ethyl acetate with the assistance of acetic acid. Such a good solubility in a range of various polar solvents was not reported previously in nanoclusters' research and is important for applications. An important result from this work is that Ag30 can sense a low concentration of Hg2+ in environmental samples (including lake water and soil solution), indicating that Ag30 can be a potential colorimetric probe for Hg2+. The sensing mechanism was revealed to be related to the anti-galvanic reduction process. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00705d

  15. The side-passivation research on LWIR HgCdTe detector

    NASA Astrophysics Data System (ADS)

    Xu, Qinfei; Tang, Hengjing; Gong, Haimei

    2008-03-01

    In order to prevent Hg running over from the exposing side of HgCdTe LWIR detector with little photosensitive region, side-passivation detectors are fabricated. Then several experiments are done to characterize the side-passivation effect. Firstly, a SEM micrograph is shown, and it makes clear that wet etching and side-passivation can remove part of defect induced by IBE. Secondly, the performance measurement indicates that the performance of side-passivation detector is superior to the general one, especially for detectors with little photosensitive region. Thirdly, hot dipping is done to say that the thermal stability of side-passivation detectors is superior to general ones. And with the exception of this, the less the photosensitive region width is, the stronger the ability of protection is. Last but not the least, the detectivity of not only general detectors but also side-passivation ones increases obviously. As a whole, the performance of side-passivation detectors increases more largely than general ones. Above all, side-wall passivating film can passivate the sensitivity of detector's surface and block Hg out of the surface effectively. The results can provide experimental reference for IR semiconductor detector.

  16. Ultimate performance of new infrared HgCdTe focal plane arrays

    NASA Astrophysics Data System (ADS)

    Osipov, V. V.; Ponomarenko, Vladimir P.; Selyakov, A. Y.

    1999-06-01

    We theoretically study physical processes in new promising hybrid IR FPAs based on HgCdTe p-n junctions and analyze them ultimate performance for 3 - 5 micrometers and 8 - 10 micrometers spectral ranges. Architecture of these FPAs are much simpler than that of existing FPAs: IR-sensitive HgCdTe p-n junctions are used as switches themselves, and capacitors used as strong elements occupy all the area under each p-n junction. These capacitors can be produced on the base of dielectrics with relatively high permittivity (of TiO2, type or integrated ferroelectrics). In contrast to CCD and CID, the proposed FPA does not use charge transfer between electrodes separated in space. We formulate requirements to the parameters of photosensitive elements and storage capacitors to reach the largest integration time and threshold characteristics close to the theoretical limits. It is shown that in principle the considered FPAs have unique parameters and 1/f noise of amplifiers can be suppressed in them. FPA for 3 - 5 micrometers spectral range with p-n junction of 20 X 20 micrometers 2 area can operate in BLIP mode at background temperature 300 K;its photosignal integration time equal to the persistence of human eye and format can reach 1024 X 1024 pixels. For 8 - 10 micrometers range these parameters are 300 microsecond(s) and 256 X 256 pixels, respectively, when TiO2 storage capacitors are used.

  17. Thermal cycling reliability of indirect hybrid HgCdTe infrared detectors

    NASA Astrophysics Data System (ADS)

    Chen, Xing; He, Kai; Wang, Jian-xin; Zhang, Qin-yao

    2013-09-01

    Thermal cycling reliability is one of the most important issues whether the HgCdTe infrared focal plane array detectors can be applied to both military and civil fields. In this paper, a 3D finite element model for indirect hybrid HgCdTe infrared detectors is established. The thermal stress distribution and thermally induced warpage of the detector assembly as a function of the distance between the detector chip and Si-ROIC, the thickness and the materials properties of electrical lead board in cryogenic temperature are analyzed. The results show that all these parameters have influences on the thermal stress distribution and warpage of the detector assembly, especially the coefficient of thermal expansion(CTE) of electrical lead board. The thermal stress and warpage in the assembly can be avoided or minimized by choosing the appropriate electrical lead board. Additionally, the warpage of some indirect hybrid detectors assembly samples is measured in experiment. The experimental results are in good agreement with the simulation results, which verifies that the results are calculated by finite element method are reasonable.

  18. Fundamental limits of MWIR HgCdTe barrier detectors operating under non-equilibrium mode

    NASA Astrophysics Data System (ADS)

    Kopytko, M.; Jóźwikowski, K.; Rogalski, A.

    2014-10-01

    The paper presents numerical considerations of temperature-dependent performance of different mid-wave infrared HgCdTe detectors (with p- and n-type active layer) for non-equilibrium operation. Current-voltage characteristics of double heterostructure PpN photodiode, pBppN barrier photodiode, nBnn and nBnnN barrier detectors are compared to find an optimal architecture for high-operating temperature conditions. Using our model, the calculated characteristics of the devices are fitted to the experimental results for HgCdTe photodiode grown on GaAs substrate by metal organic chemical vapour deposition. The performance of photodiodes with p-type absorber are limited by the generation current associated with the Shockley-Read-Hall process, while nBnn type devices (with the n-type absorber) indicate a diffusion limited dark currents associated with Auger processes. At high values of the reverse bias (over 1 V), the trap states located at dislocations lead to strong band-to-band and trap-assisted tunnelling due to high electric field within the depletion layer.

  19. Development of a P-I-N HgCdTe photomixer for laser heterodyne spectrometry

    NASA Technical Reports Server (NTRS)

    Bratt, Peter R.

    1987-01-01

    An improved HgCdTe photomixer technology was demonstrated employing a p-i-n photodiode structure. The i-region was near intrinsic n-type HgCdTe; the n-region was formed by B+ ion implantation; and the p-region was formed either by a shallow Au diffusion or by a Pt Schottky barrier. Experimental devices in a back-side illuminated mesa diode configuration were fabricated, tested, and delivered. The best photomixer was packaged in a 24-hour LN2 dewar along with a cooled GaAs FET preamplifier. Testing was performed by mixing black-body radiation with a CO2 laser beam and measuring the IF signal, noise, and signal-to-noise ratio in the GHz frequency range. Signal bandwidth for this photomixer was 1.3 GHz. The heterodyne NEP was 4.4 x 10 to the -20 W/Hz out to 1 GHz increasing to 8.6 x 10 to the -10 W/Hz at 2 GHz. Other photomixers delivered on this program had heterodyne NEPs at 1 GHz ranging from 8 x 10 to the -20 to 4.4 x 10 to the -19 W/Hz and NEP bandwidths from 2 to 4 GHz.

  20. Numerical Device Modeling, Analysis, and Optimization of Extended-SWIR HgCdTe Infrared Detectors

    NASA Astrophysics Data System (ADS)

    Schuster, J.; DeWames, R. E.; DeCuir, E. A.; Bellotti, E.; Dhar, N.; Wijewarnasuriya, P. S.

    2016-09-01

    Imaging in the extended short-wavelength infrared (eSWIR) spectral band (1.7-3.0 μm) for astronomy applications is an area of significant interest. However, these applications require infrared detectors with extremely low dark current (less than 0.01 electrons per pixel per second for certain applications). In these detectors, sources of dark current that may limit the overall system performance are fundamental and/or defect-related mechanisms. Non-optimized growth/device processing may present material point defects within the HgCdTe bandgap leading to Shockley-Read-Hall dominated dark current. While realizing contributions to the dark current from only fundamental mechanisms should be the goal for attaining optimal device performance, it may not be readily feasible with current technology and/or resources. In this regard, the U.S. Army Research Laboratory performed physics-based, two- and three-dimensional numerical modeling of HgCdTe photovoltaic infrared detectors designed for operation in the eSWIR spectral band. The underlying impetus for this capability and study originates with a desire to reach fundamental performance limits via intelligent device design.

  1. History-Dependent Impact Ionization Theory Applied to HgCdTe e-APDs

    NASA Astrophysics Data System (ADS)

    Rothman, Johan; Mollard, Laurent; Goût, Sylvain; Bonnefond, Leo; Wlassow, Jerôme

    2011-08-01

    The variation of the gain and the excess noise factor in HgCdTe avalanche photodiodes (APDs) with different junction geometries are compared with published theoretical and numerical work. It is shown that, although some features of the gain curves are reproduced, such as the constant exponential increase in the gain, the theoretical work fails to predict the observed variation of the gain as a function of multiplication layer width. In contrast, a new analytical gain model based on local impact ionization coefficients and a first direct comparison of the prediction of history-dependent impact ionization theory are shown to give a good general fit to the experimental gain data. A generic model of the gain in HgCdTe APDs has been obtained by fitting the analytical local model to gain curves of APDs with various geometries and cut-off wavelengths. The study of different hypotheses on the electric field dependence of the dead-space length and the saturation value of the impact ionization coefficient has shown that a variable dead-space effect has a direct impact on the excess noise of APDs, which is why exact excess noise measurements are necessary to achieve a pertinent estimation of the nonlocal impact ionization function.

  2. Advances in linear and area HgCdTe APD arrays for eyesafe LADAR sensors

    NASA Astrophysics Data System (ADS)

    Jack, Michael D.; Asbrock, James F.; Anderson, C.; Bailey, Steven L.; Chapman, George; Gordon, E.; Herning, P. E.; Kalisher, Murray H.; Kosai, Kim; Liquori, V.; Randall, Valerie; Rosbeck, Joseph P.; Sen, Sanghamitra; Wetzel, P.; Halmos, Maurice J.; Trotta, Patrick A.; Hunter, Andrew T.; Jensen, John E.; de Lyon, Terence J.; Johnson, W.; Walker, B.; Trussel, Ward; Hutchinson, Andy; Balcerak, Raymond S.

    2001-11-01

    HgCdTe APDs and APD arrays offer unique advantages for high-performance eyesafe LADAR sensors. These include: operation at room temperature, low-excess noise, high gain, high-quantum efficiency at eyesafe wavelengths, GHz bandwidth, and high-packing density. The utility of these benefits for systems are being demonstrated for both linear and area array sensors. Raytheon has fabricated 32 element linear APD arrays utilizing liquid phase epitaxy (LPE), and packaged and integrating these arrays with low-noise amplifiers. Typical better APDs configured as 50-micron square pixels and fabricated utilizing RIE, have demonstrated high fill factors, low crosstalk, excellent uniformity, low dark currents, and noise equivalent power (NEP) from 1-2 nW. Two units have been delivered to NVESD, assembled with range extraction electronics, and integrated into the CELRAP laser radar system. Tests on these sensors in July and October 2000 have demonstrated excellent functionality, detection of 1-cm wires, and range imaging. Work is presently underway under DARPA's 3-D imaging Sensor Program to extend this excellent performance to area arrays. High-density arrays have been fabricated using LPE and molecular beam epitaxy (MBE). HgCdTe APD arrays have been made in 5 X 5, 10 X 10 and larger formats. Initial data shows excellent typical better APD performance with unmultiplied dark current < 10 nA; and NEP < 2.0 nW at a gain of 10.

  3. Electrical Characteristics of Mid-wavelength HgCdTe Photovoltaic Detectors Exposed to Gamma Irradiation

    NASA Astrophysics Data System (ADS)

    Qiao, H.; Hu, W. D.; Li, T.; Li, X. Y.; Chang, Y.

    2016-09-01

    The study of electrical characteristics of mid-wavelength HgCdTe photodiodes irradiated by steady-state gamma rays has been carried out. The measurement of the current-voltage curves during irradiation revealed an abnormal variation of zero biased resistance R 0, and it didn't tend to change monotonically as observed in the case of post irradiation measurement. The irradiation effect was dominated by bulk effect inferred from the fitting calculations, and the generation-recombination current in the depletion region was drastically affected by gamma irradiation. Another irradiation effect was the linear increase of the series resistance with irradiation dosage which was related with the change of transportation parameters of carriers. The influence of hydrogenation on the gamma irradiation effects was also studied for comparison with the same batch of HgCdTe photodiodes, and it was found that R 0 for the hydrogenated devices showed similar change to those without hydrogenation. The series resistance, however, gave a totally different irradiation effect from the non-hydrogenated detectors and showed little change up to nearly 1 Mrad(Si) of gamma irradiation, which may be explained by the annihilation of hydrogen radicals with the defects caused by gamma irradiation.

  4. Comparison of Measured Leakage Current Distributions with Calculated Damage Energy Distributions in HgCdTe

    NASA Technical Reports Server (NTRS)

    Marshall, C. J.; Ladbury, R.; Marshall, P. W.; Reed, R. A.; Howe, C.; Weller, B.; Mendenhall, M.; Waczynski, A.; Jordan, T. M.; Fodness, B.

    2006-01-01

    This paper presents a combined Monte Carlo and analytic approach to the calculation of the pixel-to-pixel distribution of proton-induced damage in a HgCdTe sensor array and compares the results to measured dark current distributions after damage by 63 MeV protons. The moments of the Coulombic, nuclear elastic and nuclear inelastic damage distribution were extracted from Monte Carlo simulations and combined to form a damage distribution using the analytic techniques first described in [I]. The calculations show that the high energy recoils from the nuclear inelastic reactions (calculated using the Monte Car10 code MCNPX [2]) produce a pronounced skewing of the damage energy distribution. The nuclear elastic component (also calculated using the MCNPX) has a negligible effect on the shape of the damage distribution. The Coulombic contribution was calculated using MRED [3,4], a Geant4 [4,5] application. The comparison with the dark current distribution strongly suggests that mechanisms which are not linearly correlated with nonionizing damage produced according to collision kinematics are responsible for the observed dark current increases. This has important implications for the process of predicting the on-orbit dark current response of the HgCdTe sensor array.

  5. Comparison of Measured Dark Current Distributions with Calculated Damage Energy Distributions in HgCdTe

    NASA Technical Reports Server (NTRS)

    Marshall, C. J.; Marshall, P. W.; Howe, C. L.; Reed, R. A.; Weller, R. A.; Mendenhall, M.; Waczynski, A.; Ladbury, R.; Jordan, T. M.

    2007-01-01

    This paper presents a combined Monte Carlo and analytic approach to the calculation of the pixel-to-pixel distribution of proton-induced damage in a HgCdTe sensor array and compares the results to measured dark current distributions after damage by 63 MeV protons. The moments of the Coulombic, nuclear elastic and nuclear inelastic damage distributions were extracted from Monte Carlo simulations and combined to form a damage distribution using the analytic techniques first described in [1]. The calculations show that the high energy recoils from the nuclear inelastic reactions (calculated using the Monte Carlo code MCNPX [2]) produce a pronounced skewing of the damage energy distribution. While the nuclear elastic component (also calculated using the MCNPX) contributes only a small fraction of the total nonionizing damage energy, its inclusion in the shape of the damage across the array is significant. The Coulombic contribution was calculated using MRED [3-5], a Geant4 [4,6] application. The comparison with the dark current distribution strongly suggests that mechanisms which are not linearly correlated with nonionizing damage produced according to collision kinematics are responsible for the observed dark current increases. This has important implications for the process of predicting the on-orbit dark current response of the HgCdTe sensor array.

  6. Dislocation Reduction in HgCdTe Mesa Structures Formed on CdTe/Si

    NASA Astrophysics Data System (ADS)

    Simingalam, Sina; Pattison, James; Chen, Yuanping; Wijewarnasuriya, Priyalal; Rao, Mulpuri V.

    2016-09-01

    Mercury cadmium telluride (MCT) epilayers have been grown on CdTe/Si using molecular beam epitaxy and 8- μm-deep mesa structures formed using plasma etching. Following previous work done on etching mesas and subjecting material to thermal cycle annealing, we set out to determine the limits and underlying physics of dislocation reduction in mesa-etched and annealed MCT. This paper describes the dependence of dislocation reduction on anneal time, cycle annealing, temperature, and etch depth. We show dislocation density reduction below 3 × 105 cm-2 in 10- μm-wide, long-bar mesas along the [0bar{1}1] orientation with only a 5-min anneal at 400°C.

  7. Method development for Cd and Hg determination in biodiesel by electrothermal atomic absorption spectrometry with emulsion sample introduction.

    PubMed

    Aranda, Pedro R; Gásquez, José A; Olsina, Roberto A; Martinez, Luis D; Gil, Raúl A

    2012-11-15

    A novel method for analysis of biodiesel by electrothermal atomic absorption spectrometry is described. This analytical strategy involves sample preparation as emulsions for routine and reliable determination of Cd and Hg. Several experimental conditions were investigated, including emulsion stability and composition, furnace temperature program and matrix modification. Different calibration strategies were also evaluated, being the analyte addition method preferred both for Cd and Hg. The accuracy was verified through comparison with an acid digestion in a microwave closed system. The injection repeatability was evaluated as the average relative standard deviation (R.S.D %) for five successive firings and was better than 4.4% for Cd and 5.4% Hg respectively. The detection limits, evaluated by the 3σ concept of calculation (n=10), were of 10.2 μg kg(-1) (0.9 μg L(-1)) for Hg and 0.3 μg kg(-1) (0.04 μg L(-1)) for Cd. This method was successfully applied to the determination of Cd and Hg in biodiesel samples obtained from local vendors.

  8. Minority carrier lifetime in iodine-doped molecular beam epitaxy-grown HgCdTe

    SciTech Connect

    Madni, I.; Umana-Membreno, G. A.; Lei, W.; Gu, R.; Antoszewski, J.; Faraone, L.

    2015-11-02

    The minority carrier lifetime in molecular beam epitaxy grown layers of iodine-doped Hg{sub 1−x}Cd{sub x}Te (x ∼ 0.3) on CdZnTe substrates has been studied. The samples demonstrated extrinsic donor behavior for carrier concentrations in the range from 2 × 10{sup 16} cm{sup −3} to 6 × 10{sup 17} cm{sup −3} without any post-growth annealing. At a temperature of 77 K, the electron mobility was found to vary from 10{sup 4} cm{sup 2}/V s to 7 × 10{sup 3} cm{sup 2}/V s and minority carrier lifetime from 1.6 μs to 790 ns, respectively, as the carrier concentration was increased from 2 × 10{sup 16} cm{sup −3} to 6 × 10{sup 17} cm{sup −3}. The diffusion of iodine is much lower than that of indium and hence a better alternative in heterostructures such as nBn devices. The influence of carrier concentration and temperature on the minority carrier lifetime was studied in order to characterize the carrier recombination mechanisms. Measured lifetimes were also analyzed and compared with the theoretical models of the various recombination processes occurring in these materials, indicating that Auger-1 recombination was predominant at higher doping levels. An increase in deep-level generation-recombination centers was observed with increasing doping level, which suggests that the increase in deep-level trap density is associated with the incorporation of higher concentrations of iodine into the HgCdTe.

  9. Fast, high-yield synthesis of amphiphilic Ag nanoclusters and the sensing of Hg(2+) in environmental samples.

    PubMed

    Xia, Nan; Yang, Jie; Wu, Zhikun

    2015-06-14

    We report the high-yield (74%) synthesis of Ag30(Capt)18 (abbreviated as Ag30) in a very time-saving fashion (half an hour). The cluster composition was determined by high-resolution mass spectrometry combined with TG analysis, and the structure was probed by 1D and 2D NMR. Interestingly, the nanoclusters can dissolve in water and methanol, as well as in most organic solvents such as ethanol, acetone, acetonitrile, dichloromethane and ethyl acetate with the assistance of acetic acid. Such a good solubility in a range of various polar solvents was not reported previously in nanoclusters' research and is important for applications. An important result from this work is that Ag30 can sense a low concentration of Hg(2+) in environmental samples (including lake water and soil solution), indicating that Ag30 can be a potential colorimetric probe for Hg(2+). The sensing mechanism was revealed to be related to the anti-galvanic reduction process. PMID:25891837

  10. In-situ ellipsometry studies of adsorption of Hg on CdTe(211)B/Si(211) and molecular beam epitaxy growth of HgCdTe(211)B

    NASA Astrophysics Data System (ADS)

    Badano, G.; Chang, Y.; Garland, J. W.; Sivananthan, S.

    2004-06-01

    We study the adsorption of Hg on CdTe(211)B using an 88-wavelength spectroscopic ellipsometer mounted on a commercial, molecular beam epitaxy (MBE) chamber. A detailed analysis of the pseudo-dielectric function shows that Hg is present at the surface both in chemisorbed and physisorbed form. Effective medium models for a mixture of chemisorbed and physisorbed Hg on the microscopically rough CdTe surface could not fit our data. However, a proposed model in which a partial layer of physisorbed Hg sits on top of a partial layer of chemisorbed Hg fits the measured pseudo-dielectric function well and yields precise values for the thicknesses of the chemisorbed and the physisorbed Hg layers. These values change in the expected manner as a function of Hg flux, temperature, and Te coverage. An analysis of the uncertainty in the measured thicknesses is carried out in detail, and a study of the limitations of the ellipsometer used for this study is presented. The effects of these limitations on the precision and accuracy of in-situ data are enumerated.

  11. State-of-the-Art HgCdTe at Raytheon Vision Systems

    NASA Astrophysics Data System (ADS)

    Fulk, C.; Radford, W.; Buell, D.; Bangs, J.; Rybnicek, K.

    2015-09-01

    Dark current density data recorded over the past 14 years at Raytheon Vision Systems on short-wavelength infrared (SWIR) and medium-wavelength infrared (MWIR) devices were examined. This included HgCdTe detector arrays grown by liquid-phase epitaxy on CdZnTe and molecular beam epitaxy on both silicon and CdZnTe substrates. This study analyzed zero-bias resistance-area product and current-voltage measurements from test structure assemblies included on every detector wafer. The data span cutoff wavelengths from 1.7 μm to 7.5 μm and operating temperatures from 40 K to 300 K. A basis is derived for a simple manufacturing trend model for a wide range of cutoffs and temperatures. This model uses a function similar to Tennant's Rule'07 but includes a generation-recombination (GR) term. Dark current densities below the test set limit are extrapolated assuming GR-limited performance. Model assumptions are tested using sensor chip assembly (SCA) median dark current density values at the same inverse cutoff-temperature products. This model allows probabilistic determination of array manufacturability and prediction of yield, and provides a statistical basis for Raytheon's state-of-the-art performance.

  12. Fractionation distribution and preliminary ecological risk assessment of As, Hg and Cd in ornithogenic sediments from the Ross Sea region, East Antarctica.

    PubMed

    Lou, Chuangneng; Liu, Xiaodong; Nie, Yaguang; Emslie, Steven D

    2015-12-15

    To evaluate mobility of toxic elements and their potential ecological risk caused by seabird biovectors, the fractionation distributions of arsenic (As), mercury (Hg) and cadmium (Cd) were investigated in three ornithogenic sediment profiles from the Ross Sea region, East Antarctica. The results show residual As holds a dominant position, and Hg mainly derives from residual, organic matter-bound and humic acid-bound fractions, indicating weak mobility of As and Hg. However, exchangeable Cd occupies a considerable proportion in studied samples, suggesting Cd has strong mobility. The preliminary evaluation of Sediment Quality Guidelines (SGQs) shows adverse biological effects may occur occasionally for As and Cd, and rarely for Hg. Using Risk Assessment Code (RAC), the ecological risk is assessed at moderate, low and very high for As, Hg and Cd pollution, respectively. Organic matter derived from guano is the main factor controlling the mobility of Hg and Cd through adsorption and complexation.

  13. Numerical modeling of HgCdTe solidification: effects of phase diagram double-diffusion convection and microgravity level

    NASA Astrophysics Data System (ADS)

    Bune, Andris V.; Gillies, Donald C.; Lehoczky, Sandor L.

    1997-07-01

    A numerical model of HgCdTe solidification was implemented using finite the element code FIDAP. Model verification was done using both experimental data and numerical test problems. The model was used to eluate possible effects of double- diffusion convection in molten material, and microgravity level on concentration distribution in the solidified HgCdTe. Particular attention was paid to incorporation of HgCdTe phase diagram. It was found, that below a critical microgravity amplitude, the maximum convective velocity in the melt appears virtually independent on the microgravity vector orientation. Good agreement between predicted interface shape and an interface obtained experimentally by quenching was achieved. The results of numerical modeling are presented in the form of video film.

  14. Theoretical Study of Midwave Infrared HgCdTe nBn Detectors Operating at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Akhavan, Nima Dehdashti; Jolley, Gregory; Umana-Membreno, Gilberto A.; Antoszewski, Jarek; Faraone, Lorenzo

    2015-09-01

    We report a theoretical study of mercury cadmium telluride (HgCdTe) unipolar n-type/barrier/ n-type (nBn) detectors for midwave infrared (MWIR) applications at elevated temperatures. The results obtained indicate that the composition, doping, and thickness of the barrier layer in MWIR HgCdTe nBn detectors can be optimized to yield performance levels comparable with those of ideal HgCdTe p- n photodiodes. It is also shown that introduction of an additional barrier at the back contact layer of the detector structure (nBnn+) leads to substantial suppression of the Auger generation-recombination (GR) mechanism; this results in an order-of-magnitude reduction in the dark current level compared with conventional nBn or p- n junction-based detectors, thus enabling background-limited detector operation above 200 K.

  15. Quantum chemistry insight into Mg-substitution in chlorophyll by toxic heavy metals: Cd, Hg and Pb

    NASA Astrophysics Data System (ADS)

    Bechaieb, Rim; Ben Akacha, Azaiez; Gérard, Hélène

    2016-10-01

    In this paper, we examined the structural, electronic and energetic data associated to the Mg-substitution in chlorophyll by three major toxic pollutants: Cd2+, Hg2+ and Pb2+. We evidenced a highly versatile bonding of the cations with the pheophytin ligand, with a strong out-of-plane distortion for Hg and Pb. The binding energies ranged from slightly stronger than Mg2+ in the case of Hg2+ to much smaller for Pb2+. Nevertheless, our various approaches of free cations solvation allowed us to evidence that Mg-substitution should be possible for all title elements.

  16. Spatial noise limited NETD performance of a HgCdTe hybrid focal plane array

    NASA Astrophysics Data System (ADS)

    Gopal, Vishnu

    1996-04-01

    This paper presents a model for theoretically estimating the residual spatial noise in a direct injection readout hybrid focal plane array (FPA) consisting of photovoltaic detectors. The procedure consists of computing the response of the pixels after taking into account the nonlinearity induced by the transfer function in the hybrid configuration and the estimated r.m.s. response nonuniformity from the known input parameters of the detector and readout arrays. A linear two point nonuniformity compensation algorithm is applied to the computed pixel responses to calculate the residual spatial noise. Signal-to-spatial noise ratio is then used to estimate the spatial noise limited NETD performance of MWIR and LWIR Hg 1- x Cd x Te hybrid FPAs.

  17. Optical Properties of Hg1- x- y Cd x Dy y Se Crystals

    NASA Astrophysics Data System (ADS)

    Kovalyuk, T. T.; Maryanchuk, P. D.; Maistruk, É. V.; Koziarskyi, D. P.

    2013-12-01

    Results of investigations of the optical properties of Hg1- x- y Cd x Dy y Se crystals by the Bridgeman method are presented. Based on independent measurements of the reflection and transmission coefficients with a Nicolet 6700 spectrometer at Т = 300 K for wavelengths 0.9 ≤ λ ≤ 26.6 μm, values of the refractive and absorption indices and of the absorption coefficient are determined for the examined crystals. From the dependences α = f(hν) it is established that direct interband optical transitions are allowed in the crystals, and values of the gap width are determined. The effects of the temperature on the transmission coefficient and on the gap width at Т = 118-297 K are investigated.

  18. Characterization of the Microstructure of HgCdTe with p-Type Doping

    NASA Astrophysics Data System (ADS)

    Lobre, C.; Jouneau, P.-H.; Mollard, L.; Ballet, P.

    2014-08-01

    Nitrogen, phosphorus, arsenic, and antimony ions were implanted in Hg0.3Cd0.7Te (MCT) layers under the same implantation conditions. An identical annealing process was then applied to these layers to eradicate implantation damage and to activate the impurities. Implantation damage was investigated by direct visualization, by use of bright-field scanning transmission electron microscopy (BF-STEM). Secondary-ion mass spectrometry was used to investigate impurity diffusion on annealing. The combination of these two techniques revealed the significant effect of structural implantation damage on the diffusion process. Annealed layers were then investigated by high-resolution STEM imaging and energy-dispersive x-ray spectroscopy in STEM (STEM-EDX). This approach enables direct visualization and, therefore, further description of arsenic and antimony-rich nanocrystals.

  19. Low dark current LWIR HgCdTe focal plane arrays at AIM

    NASA Astrophysics Data System (ADS)

    Haiml, M.; Eich, D.; Fick, W.; Figgemeier, H.; Hanna, S.; Mahlein, M.; Schirmacher, W.; Thöt, R.

    2016-05-01

    Cryogenically cooled HgCdTe (MCT) quantum detectors are unequalled for applications requiring high imaging as well as high radiometric performance in the infrared spectral range. Compared with other technologies, they provide several advantages, such as the highest quantum efficiency, lower power dissipation compared to photoconductive devices, and fast response times, hence outperforming micro-bolometer arrays. AIM will present its latest results on n-on-p as well as p-on-n low dark current planar MCT photodiode focal plane detector arrays at cut-off wavelengths >11 μm at 80 K. Dark current densities below the Rule'07 have been demonstrated for n-on-p devices. Slightly higher dark current densities and excellent cosmetics with very low cluster and point defect densities have been demonstrated for p-on-n devices.

  20. Diode Characterization of Rockwell LWIR HgCdTe Detector Arrays

    NASA Astrophysics Data System (ADS)

    Bacon, Candice; Pipher, Judith L.; Forrest, William J.; McMurtry, Craig W.; Garnett, James D.

    2003-03-01

    Future infrared space missions will undoubtedly employ passively cooled focal planes (T ~ 30K), as well as passively cooled telescopes. Most long-wave detector arrays (e.g. Si:As IBC) require cooling to temperatures of ~ 6-8K. We have been working with Rockwell to produce 10μm cutoff HgCdTe detector arrays that, at temperatures of ~ 30K, exhibit sufficiently low dark current and sufficiently high detective quantum efficiency to be interesting for astronomy. In pursuit of these goals, Rockwell Scientific Company has delivered twelve 256 x 256 arrays (several of them engineering arrays), with cutoff wavelengths at 30K between 7.4 and 11μm for characterization at Rochester. Seven of these arrays utilize advanced structure diodes with differing capacitances arranged in rows (banded arrays), and the materials properties of the HgCdTe also vary significantly from array to array. Of ultimate interest to astronomy is the fraction of pixels with dark current below the target value of ~ 100e-/s with 10-60mV of actual reverse bias across the diodes at T ~ 30K. These arrays were developed for the purpose of selecting diode architecture: we use this fraction as one criterion for selection. We have determined from these experiments the optimal diode architecture for future array development. Measurement of the dark current as a function of reverse bias and temperature allows us to ascertain the extent to which trap-to-band tunneling dominates the dark current at this temperature. We present the results for one representative array, UR008.

  1. Gated IR imaging with 128 × 128 HgCdTe electron avalanche photodiode FPA

    NASA Astrophysics Data System (ADS)

    Beck, Jeff; Woodall, Milton; Scritchfield, Richard; Ohlson, Martha; Wood, Lewis; Mitra, Pradip; Robinson, Jim

    2007-04-01

    The next generation of IR sensor systems will include active imaging capabilities. One example of such a system is a gated-active/passive system. The gated-active/passive system promises long-range target detection and identification. A detector that is capable of both active and passive modes of operation opens up the possibility of a self-aligned system that uses a single focal plane. The detector would need to be sensitive in the 3-5 μm band for passive mode operation. In the active mode, the detector would need to be sensitive in eye-safe range, e.g. 1.55 μm, and have internal gain to achieve the required system sensitivity. The MWIR HgCdTe electron injection avalanche photodiode (e-APD) not only provides state-of-the-art 3-5 μm spectral sensitivity, but also high avalanche photodiode gain without minimal excess noise. Gains of greater than 1000 have been measured in MWIR e-APDs with a gain independent excess noise factor of 1.3. This paper reports the application of the mid-wave HgCdTe e-APD for near-IR gated-active/passive imaging. Specifically a 128x128 FPA composed of 40 μm pitch, 4.2 μm to 5 μm cutoff, APD detectors with a custom readout integrated circuit was designed, fabricated, and tested. Median gains as high as 946 at 11 V bias with noise equivalent inputs as low as 0.4 photon were measured at 80 K. A gated imaging demonstration system was designed and built using commercially available parts. High resolution gated imagery out to 9 km was obtained with this system that demonstrated predicted MTF, precision gating, and sub 10 photon sensitivity.

  2. First principles study on electronic structure and elastic properties of LaCd and LaHg

    SciTech Connect

    Devi, Hansa E-mail: gita-pagare@yahoo.co.in; Pagare, Gitanjali E-mail: gita-pagare@yahoo.co.in; Chouhan, S. S. E-mail: gita-pagare@yahoo.co.in; Sanyal, Sankar P.

    2014-04-24

    Full -potential linearized augmented plane wave method (FP- LAPW) has been used for the comparative study of electronic structure and elastic properties of CsCl-type LaCd and LaHg intermetallic compounds using generalized gradient approximation (GGA). The density of states at the Fermi Level, N (E{sub F}), is found to be 0.06 and 3.03 states/eV for LaCd and LaHg respectively. We report elastic constants for these compounds for the first time. The ductility/brittleness of these compounds has been analyzed using Pugh rule and Cauchy’s pressure.

  3. Comprehensive investigation of HgCdTe metalorganic chemical vapor deposition

    NASA Technical Reports Server (NTRS)

    Raupp, Gregory B.

    1993-01-01

    The principal objective of this experimental and theoretical research program was to explore the possibility of depositing high quality epitaxial CdTe and HgCdTe at very low pressures through metalorganic chemical vapor deposition (MOCVD). We explored two important aspects of this potential process: (1) the interaction of molecular flow transport and deposition in an MOCVD reactor with a commercial configuration, and (2) the kinetics of metal alkyl source gas adsorption, decomposition and desorption from the growing film surface using ultra high vacuum surface science reaction techniques. To explore the transport-reaction issue, we have developed a reaction engineering analysis of a multiple wafer-in-tube ultrahigh vacuum chemical vapor deposition (UHV/CVD) reactor which allows an estimate of wafer or substrate throughput for a reactor of fixed geometry and a given deposition chemistry with specified film thickness uniformity constraints. The model employs a description of ballistic transport and reaction based on the pseudo-steady approximation to the Boltzmann equation in the limit of pure molecular flow. The model representation takes the form of an integral equation for the flux of each reactant or intermediate species to the wafer surfaces. Expressions for the reactive sticking coefficients (RSC) for each species must be incorporated in the term which represents reemission from a wafer surface. The interactions of MOCVD precursors with Si and CdTe were investigated using temperature programmed desorption (TPD) in ultra high vacuum combined with Auger electron spectroscopy (AES). These studies revealed that diethyltellurium (DETe) and dimethylcadmium (DMCd) adsorb weakly on clean Si(100) and desorb upon heating without decomposing. These precursors adsorb both weakly and strongly on CdTe(111)A, with DMCd exhibiting the stronger interaction with the surface than DETe.

  4. Reduction of Ag(I), Au(III), Cu(II), and Hg(II) by Fe(II)/Fe(III) hydroxysulfate green rust.

    PubMed

    O'Loughlin, Edward J; Kelly, Shelly D; Kemner, Kenneth M; Csencsits, Roseann; Cook, Russell E

    2003-11-01

    Green rusts are mixed Fe(II)/Fe(III) hydroxides that are found in many suboxic environments where they are believed to play a central role in the biogeochemical cycling of iron. X-ray absorption fine structure analysis of hydroxysulfate green rust suspensions spiked with aqueous solutions of AgCH(3)COO, AuCl(n)(OH)(4-n), CuCl(2), or HgCl(2) showed that Ag(I), Au(III), Cu(II), and Hg(II) were readily reduced to Ag(0), Au(0), Cu(0), and Hg(0). Imaging of the resulting solids from the Ag(I)-, Au(III)-, and Cu(II)-amended green rust suspensions by transmission electron microscopy indicated the formation of submicron-sized particles of Ag(0), Au(0), and Cu(0). The facile reduction of Ag(I), Au(III), Cu(II), and Hg(II) to Ag(0), Au(0), Cu(0), and Hg(0), respectively, by green rust suggests that the presence of green rusts in suboxic soils and sediments can have a significant impact on the biogeochemistry of silver, gold, copper, and mercury, particularly with respect to their mobility.

  5. Ultra-Low Dark Current HgCdTe Detector in SWIR for Space Applications

    NASA Astrophysics Data System (ADS)

    Cervera, C.; Boulade, O.; Gravrand, O.; Lobre, C.; Guellec, F.; Sanson, E.; Ballet, P.; Santailler, J. L.; Moreau, V.; Zanatta, J. P.; Fieque, B.; Castelein, P.

    2016-09-01

    This paper presents recent developments at Commissariat à l'Energie atomique, Laboratoire d'Electronique et de Technologie de l'Information infrared laboratory on processing and characterization of p-on-n HgCdTe (MCT) planar infrared focal plane arrays (FPAs) in short-wave infrared (SWIR) spectral band for the astrophysics applications. These FPAs have been grown using both liquid phase epitaxy and molecular beam epitaxy on a lattice-matched CdZnTe substrate. This technology exhibits lower dark current and lower series resistance in comparison with n-on-p vacancy-doped architecture and is well adapted for low flux detection or high operating temperature. This architecture has been evaluated for space applications in long-wave infrared and very-long-wave infrared spectral bands with cut-off wavelengths from 10 μm up to 17 μm at 78 K and is now evaluated for the SWIR range. The metallurgical nature of the absorbing layer is also examined and both molecular beam epitaxy and liquid phase epitaxy have been investigated. Electro-optical characterizations have been performed on individual photodiodes from test arrays, whereas dark current investigation has been performed with a fully functional readout integrated circuit dedicated to low flux operations.

  6. Magnetic field effects on edge and bulk states in topological insulators based on HgTe/CdHgTe quantum wells with strong natural interface inversion asymmetry

    NASA Astrophysics Data System (ADS)

    Durnev, M. V.; Tarasenko, S. A.

    2016-02-01

    We present a theory of the electron structure and the Zeeman effect for the helical edge states emerging in two-dimensional topological insulators based on HgTe/HgCdTe quantum wells with strong natural interface inversion asymmetry. The interface inversion asymmetry, reflecting the real atomistic structure of the quantum well, drastically modifies both bulk and edge states. For the in-plane magnetic field, this asymmetry leads to a strong anisotropy of the edge-state effective g factor, which becomes dependent on the edge orientation. The interface inversion asymmetry also couples the counterpropagating edge states in the out-of-plane magnetic field leading to the opening of the gap in the edge-state spectrum by arbitrary small fields.

  7. On the stability of the spectral responsivity of cryogenically cooled photoconductive HgCdTe infrared detectors

    NASA Astrophysics Data System (ADS)

    Theocharous, E.

    2006-08-01

    The spectral responsivity of cryogenically cooled HgCdTe detectors was observed to drift slowly with time. The magnitude of the drift was shown to be strongly dependent on wavelength. The origin of the drift was investigated and was shown to arise due to a thin film of water ice depositing on the active area of the cold detector. The presence of the ice film (which is a dielectric film) interacts with the detector structure thus altering its absorbance characteristics and gives rise to the observed drifts. The drifts were temporarily eliminated by evacuating the detector dewars while baking them at 50 °C for about 48 h. This work demonstrates that HgCdTe infrared detectors should be evacuated and baked at least annually and in some cases (depending on the quality of the dewar and the measurement uncertainty required) more frequently. These observations are particularly relevant to HgCdTe detectors mounted in dewars which utilise rubber O-rings, as the ingress of moisture was found to be particularly serious in this type of dewar. This paper also identified other sources of drift present in the output of cryogenically cooled photoconductive HgCdTe detectors whose origins are currently not understood.

  8. Status of HgCdTe Barrier Infrared Detectors Grown by MOCVD in Military University of Technology

    NASA Astrophysics Data System (ADS)

    Kopytko, M.; Jóźwikowski, K.; Martyniuk, P.; Gawron, W.; Madejczyk, P.; Kowalewski, A.; Markowska, O.; Rogalski, A.; Rutkowski, J.

    2016-09-01

    In this paper we present the status of HgCdTe barrier detectors with an emphasis on technological progress in metalorganic chemical vapor deposition (MOCVD) growth achieved recently at the Institute of Applied Physics, Military University of Technology. It is shown that MOCVD technology is an excellent tool for HgCdTe barrier architecture growth with a wide range of composition, donor /acceptor doping, and without post-grown annealing. The device concept of a specific barrier bandgap architecture integrated with Auger-suppression is as a good solution for high-operating temperature infrared detectors. Analyzed devices show a high performance comparable with the state-of-the-art of HgCdTe photodiodes. Dark current densities are close to the values given by "Rule 07" and detectivities of non-immersed detectors are close to the value marked for HgCdTe photodiodes. Experimental data of long-wavelength infrared detector structures were confirmed by numerical simulations obtained by a commercially available software APSYS platform. A detailed analysis applied to explain dark current plots was made, taking into account Shockley-Read-Hall, Auger, and tunneling currents.

  9. Electrostatic assembles and optical properties of Au CdTe QDs and Ag/Au CdTe QDs

    NASA Astrophysics Data System (ADS)

    Yang, Dongzhi; Wang, Wenxing; Chen, Qifan; Huang, Yuping; Xu, Shukun

    2008-09-01

    Au-CdTe and Ag/Au-CdTe assembles were firstly investigated through the static interaction between positively charged cysteamine-stabilized CdTe quantum dots (QDs) and negatively charged Au or core/shell Ag/Au nano-particles (NCs). The CdTe QDs synthesized in aqueous solution were capped with cysteamine which endowed them positive charges on the surface. Both Au and Ag/Au NCs were prepared through reducing precursors with gallic acid obtained from the hydrolysis of natural plant poly-phenols and favored negative charges on the surface of NCs. The fluorescence spectra of CdTe QDs exhibited strong quenching with the increase of added Au or Ag/Au NCs. Railey resonance scattering spectra of Au or Ag/Au NCs increased firstly and decreased latter with the concentration of CdTe QDs, accompanied with the solution color changing from red to purple and colorless at last. Experimental results on the effects of gallic acid, chloroauric acid tetrahydrate and other reagents demonstrated the static interaction occurred between QDs and NCs. This finding reveals the possibilities to design and control optical process and electromagnetic coupling in hybrid structures.

  10. Fabrication and application of a new modified electrochemical sensor using nano-silica and a newly synthesized Schiff base for simultaneous determination of Cd2+, Cu2+ and Hg2+ ions in water and some foodstuff samples.

    PubMed

    Afkhami, Abbas; Soltani-Felehgari, Farzaneh; Madrakian, Tayyebeh; Ghaedi, Hamed; Rezaeivala, Majid

    2013-04-10

    A new chemically modified carbon paste electrode was constructed and used for rapid, simple, accurate, selective and highly sensitive simultaneous determination of cadmium, copper and mercury using square wave anodic stripping voltammetry (SWASV). The carbon paste electrode was modified by N,N'-bis(3-(2-thenylidenimino)propyl)piperazine coated silica nanoparticles. Compared with carbon paste electrode, the stripping peak currents had a significant increase at the modified electrode. Under the optimized conditions (deposition potential, -1.100 V vs. Ag/AgCl; deposition time, 60s; resting time, 10s; SW frequency, 25 Hz; pulse amplitude, 0.15 V; dc voltage step height, 4.4 mV), the detection limit was 0.3, 0.1 and 0.05 ng mL(-1) for the determination of Cd(2+), Cu(2+) and Hg(2+), respectively. The complexation reaction of the ligand with several metal cations in methanol was studied and the stability constants of the complexes were obtained. The effects of different cations and anions on the simultaneous determination of metal ions were studied and it was found that the electrode is highly selective for the simultaneous determination of Cd(2+), Cu(2+) and Hg(2+). Furthermore, the present method was applied to the determination of Cd(2+), Cu(2+) and Hg(2+) in water and some foodstuff samples.

  11. Fabrication and application of a new modified electrochemical sensor using nano-silica and a newly synthesized Schiff base for simultaneous determination of Cd2+, Cu2+ and Hg2+ ions in water and some foodstuff samples.

    PubMed

    Afkhami, Abbas; Soltani-Felehgari, Farzaneh; Madrakian, Tayyebeh; Ghaedi, Hamed; Rezaeivala, Majid

    2013-04-10

    A new chemically modified carbon paste electrode was constructed and used for rapid, simple, accurate, selective and highly sensitive simultaneous determination of cadmium, copper and mercury using square wave anodic stripping voltammetry (SWASV). The carbon paste electrode was modified by N,N'-bis(3-(2-thenylidenimino)propyl)piperazine coated silica nanoparticles. Compared with carbon paste electrode, the stripping peak currents had a significant increase at the modified electrode. Under the optimized conditions (deposition potential, -1.100 V vs. Ag/AgCl; deposition time, 60s; resting time, 10s; SW frequency, 25 Hz; pulse amplitude, 0.15 V; dc voltage step height, 4.4 mV), the detection limit was 0.3, 0.1 and 0.05 ng mL(-1) for the determination of Cd(2+), Cu(2+) and Hg(2+), respectively. The complexation reaction of the ligand with several metal cations in methanol was studied and the stability constants of the complexes were obtained. The effects of different cations and anions on the simultaneous determination of metal ions were studied and it was found that the electrode is highly selective for the simultaneous determination of Cd(2+), Cu(2+) and Hg(2+). Furthermore, the present method was applied to the determination of Cd(2+), Cu(2+) and Hg(2+) in water and some foodstuff samples. PMID:23522108

  12. Temperature-sensitive junction transformations for mid-wavelength HgCdTe photovoltaic infrared detector arrays by laser beam induced current microscope

    SciTech Connect

    Qiu, Weicheng; Hu, Weida Lin, Tie; Yin, Fei; Zhang, Bo; Chen, Xiaoshuang; Lu, Wei; Cheng, Xiang'ai Wang, Rui

    2014-11-10

    In this paper, we report on the disappearance of the photosensitive area extension effect and the unusual temperature dependence of junction transformation for mid-wavelength, n-on-p HgCdTe photovoltaic infrared detector arrays. The n-type region is formed by B{sup +} ion implantation on Hg-vacancy-doped p-type HgCdTe. Junction transformations under different temperatures are visually captured by a laser beam induced current microscope. A physical model of temperature dependence on junction transformation is proposed and demonstrated by using numerical simulations. It is shown that Hg-interstitial diffusion and temperature activated defects jointly lead to the p-n junction transformation dependence on temperature, and the weaker mixed conduction compared with long-wavelength HgCdTe photodiode contributes to the disappearance of the photosensitive area extension effect in mid-wavelength HgCdTe infrared detector arrays.

  13. High-Operating Temperature HgCdTe: A Vision for the Near Future

    NASA Astrophysics Data System (ADS)

    Lee, D.; Carmody, M.; Piquette, E.; Dreiske, P.; Chen, A.; Yulius, A.; Edwall, D.; Bhargava, S.; Zandian, M.; Tennant, W. E.

    2016-09-01

    We review recent advances in the HgCdTe material quality and detector performance achieved at Teledyne using molecular beam epitaxy growth and the double-layer planar hetero-junction (DLPH) detector architecture. By using an un-doped, fully depleted absorber, Teledyne's DLPH architecture can be extended for use in high operating temperatures and other applications. We assess the potential achievable performance for long wavelength infrared (LWIR) hetero-junction p-lightly-doped n or p-intrinsic- n (p-i-n) detectors based on recently reported results for 10.7 μm cutoff 1 K × 1 K focal plane arrays (FPAs) tested at temperatures down to 30 K. Variable temperature dark current measurements show that any Shockley-Read-Hall currents in the depletion region of these devices have lifetimes that are reproducibly greater than 100 ms. Under the assumption of comparable lifetimes at higher temperatures, it is predicted that fully-depleted background radiation-limited performance can be expected for 10- μm cutoff detectors from room temperature to well below liquid nitrogen temperatures, with room-temperature dark current nearly 400 times lower than predicted by Rule 07. The hetero-junction p-i-n diode is shown to have numerous other significant potential advantages including minimal or no passivation requirements for pBn-like processing, low 1/ f noise, compatibility with small pixel pitch while maintaining high modulation transfer function, low crosstalk and good quantum efficiency. By appropriate design of the FPA dewar shielding, analysis shows that dark current can theoretically be further reduced below the thermal equilibrium radiative limit. Modeling shows that background radiation-limited LWIR HgCdTe operating with f/1 optics has the potential to operate within √2 of background-limited performance at 215 K. By reducing the background radiation by 2/3 using novel shielding methods, operation with a single-stage thermo-electric-cooler may be possible. If the

  14. Multi-color IRFPAs made from HgCdTe grown by MOVPE

    NASA Astrophysics Data System (ADS)

    Jones, C. L.; Hipwood, L. G.; Price, J.; Shaw, C. J.; Abbott, P.; Maxey, C. D.; Lau, H. W.; Catchpole, R. A.; Ordish, M.; Knowles, P.; Gordon, N. T.

    2007-04-01

    The drive towards improved target recognition has led to an increasing interest in detection in more than one infrared band. This paper describes the design, fabrication and performance of two-colour and three-colour infrared detectors made from HgCdTe grown by Metal Organic Vapour Phase Epitaxy (MOVPE). The detectors are staring, focal plane arrays consisting of HgCdTe mesa-diode arrays bump bonded to silicon read-out integrated circuits (ROICs). Each mesa diode has one connection to the ROIC and the colours are selected by varying the applied bias. Results will be presented for both two-colour and three-colour devices. In a two-colour n-p-n design the cut-off wavelengths are defined by the compositions of the two n-type absorbers and the doping and composition of the p-type layer are chosen to prevent transistor action. The bias polarity is used to switch the output between colours. This design has been used to make MW/LW detectors with a MW band covering 3 to 5 μm and a LW band covering 5 to 10 μm. In a three-colour n-p-n design the cut-off wavelengths are defined by the compositions of the two n-type absorbers and the p-type absorber, which has an intermediate cut-off wavelength. The absorbers are separated from each other by electronic barriers consisting of wide band-gap material. At low applied bias these barriers prevent photo-electrons generated in the p-type absorber from escaping and the device then gives an output from one of the n-type absorbers. At high applied bias the electronic barrier is pulled down and the device gives an output from both the p-type absorber and one of the n-type absorbers. Thus by varying the polarity and magnitude of the bias it is possible to obtain three-colours from a two-terminal device. This design has been used to make a SW/MW/MW detector with cut-off wavelengths of approximately 3, 4 and 6 μm.

  15. Passivation Effect of Atomic Layer Deposition of Al2O3 Film on HgCdTe Infrared Detectors

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Ye, Zhen-Hua; Sun, Chang-Hong; Chen, Yi-Yu; Zhang, Tian-Ning; Chen, Xin; Lin, Chun; Ding, Ring-Jun; He, Li

    2016-09-01

    The passivation effect of atomic layer deposition of (ALD) Al2O3 film on a HgCdTe infrared detector was investigated in this work. The passivation effect of Al2O3 film was evaluated by measuring the minority carrier lifetime, capacitance versus voltage ( C- V) characteristics of metal-insulator-semiconductor devices, and resistance versus voltage ( R- V) characteristics of variable-area photodiodes. The minority carrier lifetime, C- V characteristics, and R- V characteristics of HgCdTe devices passivated by ALD Al2O3 film was comparable to those of HgCdTe devices passivated by e-beam evaporation of ZnS/CdTe film. However, the baking stability of devices passivated by Al2O3 film is inferior to that of devices passivated by ZnS/CdTe film. In future work, by optimizing the ALD Al2O3 film growing process and annealing conditions, it may be feasible to achieve both excellent electrical properties and good baking stability.

  16. Biomonitoring of Cd, Cr, Hg and Pb in the Baluarte River basin associated to a mining area (NW Mexico).

    PubMed

    Ruelas-Inzunza, J; Green-Ruiz, C; Zavala-Nevárez, M; Soto-Jiménez, M

    2011-08-15

    With the purpose of knowing seasonal variations of Cd, Cr, Hg and Pb in a river basin with past and present mining activities, elemental concentrations were measured in six fish species and four crustacean species in Baluarte River, from some of the mining sites to the mouth of the river in the Pacific Ocean between May 2005 and March 2006. In fish, highest levels of Cd (0.06 μg g ⁻¹ dry weight) and Cr (0.01 μg g⁻¹) were detected during the dry season in Gobiesox fluviatilis and Agonostomus monticola, respectively; the highest levels of Hg (0.56 μg g⁻¹) were detected during the dry season in Guavina guavina and Mugil curema. In relation to Pb, the highest level (1.65 μg g⁻¹) was detected in A. monticola during the dry season. In crustaceans, highest levels of Cd (0.05 μg g⁻¹) occurred in Macrobrachium occidentale during both seasons; highest concentration of Cr (0.09 μg g⁻¹) was also detected in M. occidentale during the dry season. With respect to Hg, highest level (0.20 μg g⁻¹) was detected during the rainy season in Macrobrachium americanum; for Pb, the highest concentration (2.4 μg g⁻¹) corresponded to Macrobrachium digueti collected in the dry season. Considering average concentrations of trace metals in surficial sediments from all sites, Cd (p<0.025), Cr (p<0.10) and Hg (p<0.15) were significantly higher during the rainy season. Biota sediment accumulation factors above unity were detected mostly in the case of Hg in fish during both seasons. On the basis of the metal levels in fish and crustacean and the provisional tolerable weekly intake of studied elements, people can eat up to 13.99, 0.79 and 2.34 kg of fish in relation to Cd, Hg and Pb, respectively; regarding crustaceans, maximum amounts were 11.33, 2.49 and 2.68 kg of prawns relative to levels of Cd, Hg and Pb, respectively.

  17. HgCdTe technology in Germany: the past, the present, and the future

    NASA Astrophysics Data System (ADS)

    Cabanski, W.; Ziegler, J.

    2009-05-01

    The first HgCdTe (MCT) activities at AEG-Telefunken in Germany were started in 1976. As part of the closing of AEG, the Heilbronn based IR-technology division was established as a spin-off company in 1995, under the brand name of AIM Infrarot-Module GmbH. A rapidly growing team of scientists focused on the detector-dewar-cooler technology and the development of linear photoconductive MCT arrays by applying the solid-state-recrystallization (SSR) technique for MCT growth, depositing and thinning MCT on sapphire substrates and oxide passivation. In 1979, after successful development of an own MCT-technology base, AEG-Telefunken entered into a license agreement with Texas Instruments for US Common Module (CM) technology in order to speed up the entry into full scale production with a transfer of MCT-material, dewar and cooler processes. CMs are still manufactured in small numbers. At the same time, a proprietary pc-MCT technology, independent of the CM production line, was developed and continuously matured and is today successfully applied in various custom designs like detectors for smart ammunition, for commercial and space applications. In 1982 started the development of 2nd Gen. photovoltaic MCT detectors, based on liquid-phase-epitaxy (LPE) in tilting and dipping technique and on planar array technology with Hg-Diffusion and ion implantation for pn-junction formation and CdTe/ZnS passivation. Linear MCT arrays in the 8-10,5 μm wavelength range with state of the art electro-optical performance have rapidly been demonstrated. Within the frame of the European anti-tank program TRIGAT, a two-way know-how-transfer between AEGTelefunken and SOFRADIR was established for linear LW MCT array processing, flip-chip-technology and dewar technology. Today, AIM's 2nd Gen. portfolio is based on MCT-LPE in dipping technique on CdZnTe substrates, characterized by a very low defect and dislocation density for 0,9 μm to 15μm wavelength application. Array processing is performed

  18. Linear HgCdTe IR FPA 288×4 with bidirectional scanning

    NASA Astrophysics Data System (ADS)

    Vasilyev, V. V.; Predein, A. V.; Varavin, V. S.; Mikhailov, N. N.; Dvoretsky, S. A.; Gumenjuk-Sichevska, J. V.; Golenkov, A. G.; Reva, V. P.; Sabinina, I. V.; Sidorov, Yu. G.; Susliakov, A. O.; Sizov, F. F.; Aseev, A. L.

    2010-09-01

    The long wavelength (8-12 μm) IR FPA 288×4 based on a hybrid assembly of n+-p diode photosensitive arrays (PA) of HgCdTe (MCT) MBE-grown structures and time delay integration (TDI) readout integrated circuits (ROIC) with bidirectional scanning have been developed, fabricated, and investigated. The p-type MCT structures were obtained by thermal annealing of as-grown n-type material in inert atmosphere. The MCT photosensitive layer with the composition 0.20-0.23 of mole fraction of CdTe was surrounded by the wide gap layers to decrease the recombination rate and surface leakage current. The diode arrays were fabricated by planar implantation of boron ions into p-MCT. The typical dark currents were about 4-7 nA at the reverse bias voltage of 150 mV. The differential resistance R was up to R0 = 1.6×107 Ω zero bias voltage, which corresponded to R0A ˜70 Ω ·cm2 and to the maximal value Rmax = 2.1 × 108 Ω. The bidirectional TDI deselecting ROIC was developed and fabricated by 1.0-μm CMOS technology with two metallic and two polysilicon layers. The IR FPAs were free of defect channels and have the average values of responsivity Sλ = 2.27×108 V/W, the detectivity Dλ * = 2.13 × 1011 cm × Hz1/2 × Wt1, and the noise equivalent temperature difference NETD = 9 mK.

  19. Distribution and relationships of As, Cd, Pb and Hg in freshwater fish from five French fishing areas.

    PubMed

    Noël, Laurent; Chekri, Rachida; Millour, Sandrine; Merlo, Mathilde; Leblanc, Jean-Charles; Guérin, Thierry

    2013-02-01

    The concentrations of arsenic, cadmium, mercury and lead in 149 muscle samples of eight freshwater fish species (European eel, bream, common carp, European catfish, roach, perch, pike and pikeperch) from five different French fishing areas from contaminated and control sites were measured by inductively coupled plasma mass spectrometry after microwave digestion under pressure. No significant correlation was found between the condition factor (CF), based on the length-mass relationship, and As, Cd and Pb levels in all the samples analysed, but a positive correlation was detected between CF and Hg levels (P<0.0001, R=0.49). Positive correlations with body length were only found for Hg in roach (P<0.05, R=0.32) and Pb in bream (P<0.05, R=0.48) and correlations with both body weight and length were also found for Hg in pike (P<0.05, R=0.90 and 0.86) and Cd in European eel (P<0.01, R=-0.35 and -0.37). The average content and the standard deviation in fish muscle samples was 0.007±0.012, 0.102±0.077, 0.142±0.097 and 0.035±0.053 mg kg(-1) of wet mass for Cd, As, Hg and Pb, respectively. Significant differences were established between groups of predatory fish and non-predatory fish for Hg and Pb, and between control and contaminated sites in the whole selection and also within feeding guilds, i.e. the values of Hg in the benthophagic fish were significantly different between these sites. Finally, these results were also compared for each species with previous French and European studies.

  20. Terahertz magneto-optics in the ferromagnetic semiconductor HgCdCr2Se4

    NASA Astrophysics Data System (ADS)

    Huisman, T. J.; Mikhaylovskiy, R. V.; Telegin, A. V.; Sukhorukov, Yu. P.; Granovsky, A. B.; Naumov, S. V.; Rasing, Th.; Kimel, A. V.

    2015-03-01

    The magneto-optical response of the ferromagnetic semiconductor HgCdCr2Se4 at terahertz (THz) frequencies is studied using polarization sensitive THz time-domain spectroscopy. It is shown that the polarization state of broadband terahertz pulses, with a spectrum spanning from 0.2 THz to 2.2 THz, changes as an even function of the magnetization of the medium. Analysing the ellipticity and the rotation of the polarization of the THz radiation, we show that these effects originate from linear birefringence and dichroism, respectively, induced by the magnetic ordering. These effects are rather strong and reach 102 rad/m at an applied field of 1 kG which saturates the magnetization of the sample. Our observation serves as a proof-of-principle showing strong effects of the magnetic order on the response of a medium to electric fields at THz frequencies. These experiments also suggest the feasibility of spin-dependent transport measurements on a sub-picosecond timescale.

  1. Cd Hg Te (1.3 µm - 1.55 µm) Avalanche Photodiode

    NASA Astrophysics Data System (ADS)

    Meslage, J.; Pichard, G.; Fragnon, M.; Royer, M.; Nguyen Duy, M.; Biosrobert, C.; Morvan, D.

    1983-11-01

    The particular Cd0.7 Hg0.3Te band structure:almost equality of band gap and spin orbit splitting, provides good ionization properties to this alloy : a high ionization coefficients ratio is expected. The devices elaboration is made by planar technology. A N+/N/P+ structure is achieved by ions implantation followed by a diffusion process. A diffused guard ring allows to avoid surface and junction edge effects. The I (V) characteristic shows a breakdown voltage (VB) of about 100 V. The dark current at 0.95 VB, amounts 100nA.Photodiodes sensitivity is typiclly of 0.7. A/W when M=1.Multiplication coefficients as high as 40 have been measured, the photoresponse spatial homogeneity in gain mode has been also controlled with a lOμm size spot : no microplasma effect have been observed. Photodetectors sensitivity, measured at 500 MHz, remains identical in avalanche operating mode. Good linearity is obtained when plotting P-N schottky noise versus light intensity No excess noise was observed. The study of the avalanche photodiode noise, synchronous with 1.3. μm DEL emission, at 30 MHz with a 1 MHz bandwith has been carried out in relation to the multiplication factor, and has led to an estimation of the ionization coefficient ratio.

  2. Complex Behavior of Time Response of HgCdTe HOT Photodetectors

    NASA Astrophysics Data System (ADS)

    Pawluczyk, J.; Piotrowski, J.; Pusz, W.; Koźniewski, A.; Orman, Z.; Gawron, W.; Piotrowski, A.

    2015-09-01

    We report on the time response of higher-operating-temperature (HOT, T ˜200 K to 300 K) fast long-cutoff-wavelength infrared (LWIR) HgCdTe photodetectors. For a long time, photoconductive and photoelectromagnetic devices operating near room temperature have been used as fast (sub-nanosecond) photodetectors. Unfortunately, such devices suffer from relatively low detectivity. Recent efforts have focused on heterojunction photodiodes that offer both fast response and high performance. This paper presents computer simulations and experimental studies that reveal mechanisms limiting the time response and design rules to achieve short response time of HOT LWIR photodiodes operating at both zero and reverse bias. Complex time response curves with fast and slow components have been observed. The latter has been found to be mainly determined by the ambipolar diffusion of photogenerated charge carriers and by the diffusion capacitance combined with the built-in or external series resistance. The limitations are especially pronounced in zero-biased photodiodes characterized by large diffusion capacitance, where series resistance of only 1 Ω significantly reduces the response speed of devices with 100 μm × 100 μm photosensitive area.

  3. HgCdTe APD-based linear-mode photon counting components and ladar receivers

    NASA Astrophysics Data System (ADS)

    Jack, Michael; Wehner, Justin; Edwards, John; Chapman, George; Hall, Donald N. B.; Jacobson, Shane M.

    2011-05-01

    Linear mode photon counting (LMPC) provides significant advantages in comparison with Geiger Mode (GM) Photon Counting including absence of after-pulsing, nanosecond pulse to pulse temporal resolution and robust operation in the present of high density obscurants or variable reflectivity objects. For this reason Raytheon has developed and previously reported on unique linear mode photon counting components and modules based on combining advanced APDs and advanced high gain circuits. By using HgCdTe APDs we enable Poisson number preserving photon counting. A metric of photon counting technology is dark count rate and detection probability. In this paper we report on a performance breakthrough resulting from improvement in design, process and readout operation enabling >10x reduction in dark counts rate to ~10,000 cps and >104x reduction in surface dark current enabling long 10 ms integration times. Our analysis of key dark current contributors suggest that substantial further reduction in DCR to ~ 1/sec or less can be achieved by optimizing wavelength, operating voltage and temperature.

  4. New developments in HgCdTe APDs and LADAR receivers

    NASA Astrophysics Data System (ADS)

    McKeag, William; Veeder, Tricia; Wang, Jinxue; Jack, Michael; Roberts, Tom; Robinson, Tom; Neisz, James; Andressen, Cliff; Rinker, Robert; Cook, T. Dean; Amzajerdian, Farzin

    2011-06-01

    Raytheon is developing NIR sensor chip assemblies (SCAs) for scanning and staring 3D LADAR systems. High sensitivity is obtained by integrating high performance detectors with gain, i.e., APDs with very low noise Readout Integrated Circuits (ROICs). Unique aspects of these designs include: independent acquisition (non-gated) of pulse returns, multiple pulse returns with both time and intensity reported to enable full 3D reconstruction of the image. Recent breakthrough in device design has resulted in HgCdTe APDs operating at 300K with essentially no excess noise to gains in excess of 100, low NEP <1nW and GHz bandwidths and have demonstrated linear mode photon counting. SCAs utilizing these high performance APDs have been integrated and demonstrated excellent spatial and range resolution enabling detailed 3D imagery both at short range and long ranges. In the following we will review progress in real-time 3D LADAR imaging receiver products in two areas: (1) scanning 256 × 4 configuration for the Multi-Mode Sensor Seeker (MMSS) program and (2) staring 256 × 256 configuration for the Autonomous Landing and Hazard Avoidance Technology (ALHAT) lunar landing mission.

  5. 1024 x 1024 tactical IR HgCdTe staring sensor system

    NASA Astrophysics Data System (ADS)

    Barrios, Steven R.; Bogosyan, Arsen; Chan, Gilbert Y.; Gubala, Michael J.; Huey, Herbert; Kwok, Raymond S.; Lawrence, Raymond G.; Muzilla, Mark; Yang, John W.

    2000-12-01

    Boeing has demonstrated Mid-Wave Infrared (MWIR) imaging performance of a large format tactical sensor based on a 1024x1024 focal plane array (FPA). The ultra-high density infrared (IR) sensor system consists of a 10.47 mm aperture optics, a 10242 Mercury Cadmium Telluride (HgCdTe) FPA, a Sterling cycle integrated cooler dewar assembly (IDA), and a pre-processor with advanced algorithms for data correction and image enhancement. In this paper, we will present measured performance parameters of the staring sensor system including minimum resolvable temperature (MRT), noise equivalent temperature difference (NEDT), and noise equivalent irradiance (NEI). Key features and attributes of the integrated hardware will also be described. A similar instrument to enhance situational awareness is under evaluation as part of a panoramic camera system to demonstrate feasibility of sensor-guided landing in adverse environments for heavy transports such as the Boeing C17 aircraft. Considerations are underway to utilize the camera as part of the Joint Strike Fighter (JSF) sensor suite. We will introduce other system applications for which the large format imagery can be strategically employed and discuss its operational advantages.

  6. Si (211) substrate thinning technology for HgCdTe focal plane arrays on Si substrates

    NASA Astrophysics Data System (ADS)

    Zhang, Shan; Wang, Chenfei; Cao, Juying; Hu, Xiaoning

    2010-10-01

    A wet chemical etching method for (211)Si substrates was demonstrated in this paper. The morphologies and cleanness of (211) Si surface etched in different mixture ratio HF-HNO3-HAC solutions have been studied by using optical microscope and the surface profile measuring system (SPMS). The analysis of the surface images indicated that the Si etched by the HF-HNO3-HAC (2:15:5) has the smoother surface, and the wet chemical etching can effectively eliminate the damage introduced by the chemo-mechanical polishing. An auto wet chemical etching agitator which can move in the vertical orientation was used. The wet chemical etching rate of (211) Si was obtained in the room temperature and the transmitted spectra of (211) Si with different thickness were measured by Fourier Transform Infrared Spectroscopy (FTIR) and compared. It is confirmed that the Si with different thickness make no difference to the spectral response in mid-wave. By using this novel technology, the Si substrate of HgCdTe/Si detector was removed completely with the HF-HNO3- HAC (2:15:5) solution. It is obvious that the wet chemical etching method can remove the (211) Si substrates with no damage and detector can work better.

  7. Loading Ag nanoparticles on Cd(II) boron imidazolate framework for photocatalysis

    NASA Astrophysics Data System (ADS)

    Liu, Min; Zhang, De-Xiang; Chen, Shumei; Wen, Tian

    2016-05-01

    An amine-functionalized Cd(II) boron imidazolate framework (BIF-77) with three-dimensional open structure has been successfully synthesized, which can load Ag nanoparticles (NPs) for photocatalytic degradation of methylene blue (MB).

  8. Influence of Ag doping concentration on structural and optical properties of CdS thin film

    SciTech Connect

    Kumar, Pragati; Saxena, Nupur; Gupta, Vinay; Agarwal, Avinash

    2015-05-15

    This work shows the influence of Ag concentration on structural properties of pulsed laser deposited nanocrystalline CdS thin film. X-ray photoelectron spectroscopy (XPS) studies confirm the dopant concentration in CdS films and atomic concentration of elements. XPS studies show that the samples are slightly sulfur deficient. GAXRD scan reveals the structural phase transformation from cubic to hexagonal phase of CdS without appearance of any phase of CdO, Ag{sub 2}O or Ag{sub 2}S suggesting the substitutional doping of Ag ions. Photoluminescence studies illustrate that emission intensity increases with increase in dopant concentration upto 5% and then decreases for higher dopant concentration.

  9. Zn, Cu, Cd and Hg binding to metallothioneins in harbour porpoises Phocoena phocoena from the southern North Sea

    PubMed Central

    Das, Krishna; De Groof, Arnaud; Jauniaux, Thierry; Bouquegneau, Jean-Marie

    2006-01-01

    Background Harbour porpoises Phocoena phocoena from the southern North Sea are known to display high levels of Zn and Hg in their tissues linked to their nutritional status (emaciation). The question arises regarding a potential role of metallothioneins (MTs) with regard to these high metal levels. In the present study, metallothionein detection and associated Zn, Cd, Cu and Hg concentrations were investigated in the liver and kidney of 14 harbour porpoises collected along the Belgian coast. Results Metallothioneins seemed to play a key role in essential metal homeostasis, as they were shown to bind 50% of the total hepatic Zn and 36% of the total hepatic Cu concentrations. Renal MTs also participated in Cd detoxification, as they were shown to bind 56% of the total renal Cd. Hg was mainly found in the insoluble fraction of both liver and kidney. Concomitant increases in total Zn concentration and Zn bound to MTs were observed in the liver, whereas Zn concentration bound to high molecular weight proteins remained constant. Cu, Zn and Cd were accumulated preferentially in the MT fraction and their content in this fraction increased with the amount in the hepatocytosol. Conclusion MTs have a key role in Zn and Cu homeostasis in harbour porpoises. We demonstrated that increasing hepatic Zn concentration led to an increase in Zn linked to MTs, suggesting that these small proteins take over the Zn overload linked to the poor body condition of debilitated harbour porpoises. PMID:16464247

  10. Nondestructive Characterization of Residual Threading Dislocation Density in HgCdTe Layers Grown on CdZnTe by Liquid-Phase Epitaxy

    NASA Astrophysics Data System (ADS)

    Fourreau, Y.; Pantzas, K.; Patriarche, G.; Destefanis, V.

    2016-09-01

    The performance of mercury cadmium telluride (MCT)-based infrared (IR) focal-plane arrays is closely related to the crystalline perfection of the HgCdTe thin film. In this work, Te-rich, (111)B-oriented HgCdTe epilayers grown by liquid-phase epitaxy on CdZnTe substrates have been studied. Surface atomic steps are shown on as-grown MCT materials using atomic force microscopy (AFM) and white-light interferometry (WLI), suggesting step-flow growth. Locally, quasiperfect surface spirals are also evidenced. A demonstration is given that these spirals are related to the emergence of almost pure screw threading dislocations. A nondestructive and quantitative technique to measure the threading dislocation density is proposed. The technique consists of counting the surface spirals on the as-grown MCT surface from images obtained by either AFM or WLI measurements. The benefits and drawbacks of both destructive—chemical etching of HgCdTe dislocations—and nondestructive surface imaging techniques are compared. The nature of defects is also discussed. Finally, state-of-the-art threading dislocation densities in the low 104 cm-2 range are evidenced by both etch pit density (EPD) and surface imaging measurements.

  11. "Turn on" and label-free core-shell Ag@SiO2 nanoparticles-based metal-enhanced fluorescent (MEF) aptasensor for Hg2+

    NASA Astrophysics Data System (ADS)

    Pang, Yuanfeng; Rong, Zhen; Xiao, Rui; Wang, Shengqi

    2015-03-01

    A turn on and label-free fluorescent apasensor for Hg2+ with high sensitivity and selectivity has been demonstrated in this report. Firstly, core-shell Ag@SiO2 nanoparticles (NPs) were synthetized as a Metal-Enhanced Fluorescent (MEF) substrate, T-rich DNA aptamers were immobilized on the surface of Ag@SiO2 NPs and thiazole orange (TO) was selected as fluorescent reporter. After Hg2+ was added to the aptamer-Ag@SiO2 NPs and TO mixture buffer solution, the aptamer strand can bind Hg2+ to form T-Hg2+-T complex with a hairpin structure which TO can insert into. When clamped by the nucleic acid bases, the fluorescence quanta yield of TO will be increased under laser excitation and emitted a fluorescence emission. Furthermore, the fluorescence emission can be amplified largely by the MEF effect of the Ag@SiO2 NPs. The whole experiment can be finished within 30 min and the limit of detection is 0.33 nM even with interference by high concentrations of other metal ions. Finally, the sensor was applied for detecting Hg2+ in different real water samples with satisfying recoveries over 94%.

  12. "Turn on" and label-free core−shell Ag@SiO2 nanoparticles-based metal-enhanced fluorescent (MEF) aptasensor for Hg2+

    PubMed Central

    Pang, Yuanfeng; Rong, Zhen; Xiao, Rui; Wang, Shengqi

    2015-01-01

    A turn on and label-free fluorescent apasensor for Hg2+ with high sensitivity and selectivity has been demonstrated in this report. Firstly, core−shell Ag@SiO2 nanoparticles (NPs) were synthetized as a Metal-Enhanced Fluorescent (MEF) substrate, T-rich DNA aptamers were immobilized on the surface of Ag@SiO2 NPs and thiazole orange (TO) was selected as fluorescent reporter. After Hg2+ was added to the aptamer-Ag@SiO2 NPs and TO mixture buffer solution, the aptamer strand can bind Hg2+ to form T-Hg2+-T complex with a hairpin structure which TO can insert into. When clamped by the nucleic acid bases, the fluorescence quanta yield of TO will be increased under laser excitation and emitted a fluorescence emission. Furthermore, the fluorescence emission can be amplified largely by the MEF effect of the Ag@SiO2 NPs. The whole experiment can be finished within 30 min and the limit of detection is 0.33 nM even with interference by high concentrations of other metal ions. Finally, the sensor was applied for detecting Hg2+ in different real water samples with satisfying recoveries over 94%. PMID:25819733

  13. Electrical and Optical Studies of Defect Structure of HgCdTe Films Grown by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Świątek, Z.; Ozga, P.; Izhnin, I. I.; Fitsych, E. I.; Voitsekhovskii, A. V.; Korotaev, A. G.; Mynbaev, K. D.; Varavin, V. S.; Dvoretsky, S. A.; Mikhailov, N. N.; Yakushev, M. V.; Bonchyk, A. Yu.; Savytsky, H. V.

    2016-07-01

    Electrical and optical studies of defect structure of HgCdTe films grown by molecular beam epitaxy (MBE) are performed. It is shown that the peculiarity of these films is the presence of neutral defects formed at the growth stage and inherent to the material grown by MBE. It is assumed that these neutral defects are the Te nanocomplexes. Under ion milling, they are activated by mercury interstitials and form the donor centers with the concentration of 1017 cm-3, which makes it possible to detect such defects by measurements of electrical parameters of the material. Under doping of HgCdTe with arsenic using high temperature cracking, the As2 dimers are present in the arsenic flow and block the neutral Te nanocomplexes to form donor As2Te3 complexes. The results of electrical studies are compared with the results of studies carried out by micro-Raman spectroscopy.

  14. Chemical analysis of anodic oxide layers based on Hg/sub 1-x/Cd/sub x/Te

    SciTech Connect

    Korsak, T.E.

    1987-02-01

    The goal of this work is to study the application of the photometric method in analyzing the composition of Hg/sub 1-x/Cd/sub x/Te solid solution anodic oxide with high accuracy and without preliminary separation of the elements. In order to determine cadmium content, a photometric measurement on a complex of this element with xylenol orange was used. Mercury concentration was determined using an extraction photometric method based on benzene extraction of chloride complexes of mercury anions with crystal violet. Tellurium content was determined by extraction with dichloroethane of bromide complexes of tellurium with diantipyrylpropylmethane. The authors synthesized diantipyrylpropylmethane as described. They studied single crystal Hg/sub 1-x/Cd/sub x/Te samples of random orientation with x = 0.2 and n-type conductivity.

  15. Proton-Induced Transients and Charge Collection Mechanisms in a LWlR HgCdTe Focal Plane Array

    NASA Technical Reports Server (NTRS)

    Marshall, Paul; Hubbs, John E.; Arrington, Douglas C.; Reed, Robert A.; Gee, George; Pickel, Jim C.; Ramos, Rudolfo A.; Marshall, Cheryl J.

    2003-01-01

    Low noise performance of IR detectors is required, even in the presence of charged particles. Galactic cosmic rays, trapped protons & solar energetic particles. Particle induced transients identified as an important source of noise on ESA's ISO satellite. Also observed on NICMOS Instrument on NASA% Hubble Space Telescope. Tools to analyse particle induced transients have been developed. To date, comparisons of model have been made to flight data for a HgCdTe array exposed to trapped protons, and to a Si array exposed to laboratory protons. We report ground based proton transient measurements in a modem LWlR HgCdTe array operating under cryogenic conditions. Demonstration of charge collection mechanisms. Provide benchmarks for modeling tools.

  16. Synthesis and Cell Imaging of a Near-Infrared Fluorescent Magnetic "CdHgTe-Dextran-Magnetic Layered Double Hydroxide-Fluorouracil" Composite.

    PubMed

    Jin, XueQin; Zhang, Min; Gou, GuoJing; Ren, Jie

    2016-05-01

    In this article, a water-soluble near-infrared quantum dots of CdHgTe were prepared and subsequently combined with the drug delivery system "dextran-magnetic layered double hydroxide-fluorouracil" (DMF) to build a new nanostructure platform in form of CdHgTe@DMF, in which the fluorescent probe function of quantum dots and the magnetic targeting transport and slow-release curative effect of DMF were blended availably together. The luminescent property particle size, and internal structure of the composite were characterized using fluorescence spectrophotometer, ultraviolet spectrophotometer, laser particle size distribution, TEM, X-ray diffraction, and Fourier transform infrared. The experimental study on fluorescent tags effect and magnetic targeting performance of the multifunctional platform were performed by fluorescent confocal imaging. The results showed that the CdHgTe could be grafted successfully onto the surface of DMF by electrostatic coupling. The CdHgTe@DMF composite showed super-paramagnetic and photoluminescence property in the near-infrared wavelength range of 575-780 nm. Compared with CdHgTe, the CdHgTe@DMF composite could significantly improve the cell imaging effect, the label intensity increased with the magnetic field intensity, and obeyed the linear relationship Dmean = 1.758 + 0.0075M under the conditions of magnetic field interference. It can be implied that the CdHgTe@DMF may be an effective multifunction tool applying to optical bioimaging and magnetic targeted therapy.

  17. Synthesis and Cell Imaging of a Near-Infrared Fluorescent Magnetic "CdHgTe-Dextran-Magnetic Layered Double Hydroxide-Fluorouracil" Composite.

    PubMed

    Jin, XueQin; Zhang, Min; Gou, GuoJing; Ren, Jie

    2016-05-01

    In this article, a water-soluble near-infrared quantum dots of CdHgTe were prepared and subsequently combined with the drug delivery system "dextran-magnetic layered double hydroxide-fluorouracil" (DMF) to build a new nanostructure platform in form of CdHgTe@DMF, in which the fluorescent probe function of quantum dots and the magnetic targeting transport and slow-release curative effect of DMF were blended availably together. The luminescent property particle size, and internal structure of the composite were characterized using fluorescence spectrophotometer, ultraviolet spectrophotometer, laser particle size distribution, TEM, X-ray diffraction, and Fourier transform infrared. The experimental study on fluorescent tags effect and magnetic targeting performance of the multifunctional platform were performed by fluorescent confocal imaging. The results showed that the CdHgTe could be grafted successfully onto the surface of DMF by electrostatic coupling. The CdHgTe@DMF composite showed super-paramagnetic and photoluminescence property in the near-infrared wavelength range of 575-780 nm. Compared with CdHgTe, the CdHgTe@DMF composite could significantly improve the cell imaging effect, the label intensity increased with the magnetic field intensity, and obeyed the linear relationship Dmean = 1.758 + 0.0075M under the conditions of magnetic field interference. It can be implied that the CdHgTe@DMF may be an effective multifunction tool applying to optical bioimaging and magnetic targeted therapy. PMID:27039355

  18. Noise processes modeling in HgCdTe infrared photodiode detectors

    NASA Astrophysics Data System (ADS)

    Burlakov, Igor D.; Selyakov, Andrew Y.; Ponomarenko, Vladimir P.; Filachev, Anatoly M.

    2010-04-01

    A numerical model of the current noise spectral density in elements of infrared focal plane array based on HgCdTe photodiodes has been developed. Model is based on Langevine method and applied to the photodiode with p+-n-junction and base of finite length d. Dominated dark current diffusion mechanism and random nature of thermal generationrecombination and scattering processes determined the diffusion current fluctuations has been taken into account. The model main peculiar properties are the stochastic boundary conditions on the interface between the depletion and quasineutral regions. Current noise spectral density of the diode with thin base d < Lp, where Lp is the hole diffusion length in n-region, has been calculated. In thin base diodes with blocking contact to substrate, in which recombination velocity S = 0, a noise suppression effect is revealed. At noticeable reverse junction biases |qV| > 3kT the diffusion current noise suppression is to be observed in whole frequency band ωtfl << 1, where tfl is the hole flight time through the depletion region. In this case the diffusion current noise spectral density is less than in diodes with thick base (d >> Lp) by a factor th(d/Lp). At slight biases |qV| < 3kT the diffusion current noise suppression occurs only in limited frequency band ωτ < 1, where τ is the minority carriers lifetime. At high frequencies ωτ >> 1 diffusion current noise comes out of fluctuations caused by scattering processes and is independent on the diode structure. Photocurrent noise spectral density has been calculated too. Model developed is useful for the photodiode elements and arrays optimization.

  19. ECR Ar/CH4/H2 plasma damage in HgCdTe

    NASA Astrophysics Data System (ADS)

    Kim, Eui-Tae; Han, Myung-Soo; Kwon, J. H.; Hahn, Suk-Ryong; Song, Kyung H.; Lee, Sang G.; Lee, Tae Seok; Lee, Y. S.; Kim, Jae Mook

    1998-10-01

    The capacitance-voltage (C-V) and the Hall effect measurements were used, in order to study electron cyclotron resonance (ECR) plasma damage in HgCdTe (MCT). In this study using ECR treatments of MCT and C-V measurements, we observed that the type conversion of MCT surface largely depended on the ECR etching conditions, when MCT was etched by ECR plasma as a function of the ECR power and dc bias. The n-type conversion was not observed when the p-type MCT was etched under the condition of ECR power 150 W and dc bias -20 V. As dc bias of ECR increased over -40 V at the constant ECR power 150 W, the p-type MCT was converted to n-type. The p-type MCT was also converted to n-type when ECR power increased to 500 W at the constant dc bias -20 V. These results probably were due to the inter-diffusion of a large amount of excess mercury, liberated during the ECR treatment, into MCT, which were similar to the results of ion milling process. Another interesting result, observed in C-V measurements, was the p- type conversion from n-type MCT when the n-type MCT was etched under the condition of ECR power 150 W and dc bias -20 V. As dc bias of ECR increased over -40 V, the C-V curve was the results of n-type MCT characteristics. We considered that a low dc bias of -20 V, the hydrogen passivation and the deficiency of mercury in the etched surface were dominant and resulted in conversion to p-type. As dc bias increased over -40 V, the inter-diffusion of excess mercury into MCT was dominant and associated with keeping the n-type characteristics.

  20. HgCdTe Detectors for Space and Science Imaging: General Issues and Latest Achievements

    NASA Astrophysics Data System (ADS)

    Gravrand, O.; Rothman, J.; Cervera, C.; Baier, N.; Lobre, C.; Zanatta, J. P.; Boulade, O.; Moreau, V.; Fieque, B.

    2016-09-01

    HgCdTe (MCT) is a very versatile material system for infrared (IR) detection, suitable for high performance detection in a wide range of applications and spectral ranges. Indeed, the ability to tailor the cutoff frequency as close as possible to the needs makes it a perfect candidate for high performance detection. Moreover, the high quality material available today, grown either by molecular beam epitaxy or liquid phase epitaxy, allows for very low dark currents at low temperatures, suitable for low flux detection applications such as science imaging. MCT has also demonstrated robustness to the aggressive environment of space and faces, therefore, a large demand for space applications. A satellite may stare at the earth, in which case detection usually involves a lot of photons, called a high flux scenario. Alternatively, a satellite may stare at outer space for science purposes, in which case the detected photon number is very low, leading to low flux scenarios. This latter case induces very strong constraints onto the detector: low dark current, low noise, (very) large focal plane arrays. The classical structure used to fulfill those requirements are usually p/ n MCT photodiodes. This type of structure has been deeply investigated in our laboratory for different spectral bands, in collaboration with the CEA Astrophysics lab. However, another alternative may also be investigated with low excess noise: MCT n/ p avalanche photodiodes (APD). This paper reviews the latest achievements obtained on this matter at DEFIR (LETI and Sofradir common laboratory) from the short wave infrared (SWIR) band detection for classical astronomical needs, to long wave infrared (LWIR) band for exoplanet transit spectroscopy, up to very long wave infrared (VLWIR) bands. The different available diode architectures ( n/ p VHg or p/ n, or even APDs) are reviewed, including different available ROIC architectures for low flux detection.

  1. Dislocations as a Noise Source in LWIR HgCdTe Photodiodes

    NASA Astrophysics Data System (ADS)

    Jóźwikowski, Krzysztof; Jóźwikowska, Alina; Martyniuk, Andrzej

    2016-10-01

    The effect of dislocation on the 1/ f noise current in long-wavelength infrared (LWIR) reverse biased HgCdTe photodiodes working at liquid nitrogen (LN) temperature was analyzed theoretically by using a phenomenological model of dislocations as an additional Shockley-Read-Hall (SRH) generation-recombination (G-R) channel in heterostructure. Numerical analysis was involved to solve the set of transport equations in order to find a steady state values of physical parameters of the heterostructure. Next, the set of transport equations for fluctuations (TEFF) was formulated and solved to obtain the spectral densities (SD) of the fluctuations of electrical potential, quasi-Fermi levels, and temperature. The SD of mobility fluctuations, shot G-R noise, and thermal noise were also taken into account in TEFF. Additional expressions for SD of 1/ f fluctuations of the G-R processes were derived. Numerical values of the SD of noise current were compared with the experimental results of Johnson et al. Theoretical analysis has shown that the dislocations increase the G-R processes and this way cause the growth of G-R dark current. Despite the fact that dislocations increase both shot G-R noise and 1/ f G-R noise, the main cause of 1/ f current noise in LN cooled LWIR photodiodes are fluctuations of the carriers mobility determined by 1/ f fluctuations of relaxation times. As the noise current is proportional to the total diode current, growth of G-R dark current caused by dislocations leads to the growth of noise current.

  2. Dislocations as a Noise Source in LWIR HgCdTe Photodiodes

    NASA Astrophysics Data System (ADS)

    Jóźwikowski, Krzysztof; Jóźwikowska, Alina; Martyniuk, Andrzej

    2016-02-01

    The effect of dislocation on the 1/f noise current in long-wavelength infrared (LWIR) reverse biased HgCdTe photodiodes working at liquid nitrogen (LN) temperature was analyzed theoretically by using a phenomenological model of dislocations as an additional Shockley-Read-Hall (SRH) generation-recombination (G-R) channel in heterostructure. Numerical analysis was involved to solve the set of transport equations in order to find a steady state values of physical parameters of the heterostructure. Next, the set of transport equations for fluctuations (TEFF) was formulated and solved to obtain the spectral densities (SD) of the fluctuations of electrical potential, quasi-Fermi levels, and temperature. The SD of mobility fluctuations, shot G-R noise, and thermal noise were also taken into account in TEFF. Additional expressions for SD of 1/f fluctuations of the G-R processes were derived. Numerical values of the SD of noise current were compared with the experimental results of Johnson et al. Theoretical analysis has shown that the dislocations increase the G-R processes and this way cause the growth of G-R dark current. Despite the fact that dislocations increase both shot G-R noise and 1/f G-R noise, the main cause of 1/f current noise in LN cooled LWIR photodiodes are fluctuations of the carriers mobility determined by 1/f fluctuations of relaxation times. As the noise current is proportional to the total diode current, growth of G-R dark current caused by dislocations leads to the growth of noise current.

  3. Nernst and Seebeck effects in HgTe/CdTe topological insulator

    SciTech Connect

    Zhang, Yuan; Song, Juntao; Li, Yu-Xian

    2015-03-28

    The Seebeck and Nernst effects in HgTe/CdTe quantum wells are studied using the tight-binding Hamiltonian and the nonequilibrium Green's function method. The Seebeck coefficient, S{sub c}, and the Nernst coefficient, N{sub c}, oscillate as a function of E{sub F}, where E{sub F} is the Fermi energy. The Seebeck coefficient shows peaks when the Fermi energy crosses the discrete transverse channels, and the height of the nth peak of the S{sub c} is [ln2/(1/2 +|n|)] for E{sub F} > 0. For the case E{sub F} < 0, the values of the peaks are negative, but the absolute values of the first five peaks are the same as those for E{sub F} > 0. The 6th peak of S{sub c} reaches the value [ln2/1.35] due to a higher density of states. When a magnetic field is applied, the Nernst coefficient appears. However, the values of the peaks for N{sub c} are all positive. For a weak magnetic field, the temperature suppresses the oscillation of the Seebeck and Nernst coefficients but increases their magnitude. For a large magnetic field, because of the highly degenerate Landau levels, the peaks of the Seebeck coefficient at position E{sub F}=−12, 10, 28meV, and Nernst coefficient at E{sub F}=−7, 10meV are robust against the temperature.

  4. Heat capacity, enthalpy of mixing, and thermal conductivity of Hg(1-x)Cd(x)Te pseudobinary melts

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua

    1986-01-01

    Heat capacity and enthalpy of mixing of Hg(1-x)Cd(x)Te pseudobinary melts were calculated assuming an associated solution model for the liquid phase. The thermal conductivity of the pseudobinary melts for x = 0, 0.05, 0.1, and 0.2 was then calculated from the heat capacity values and the experimental values of thermal diffusivity and density for these melts. The thermal conductivity for the pseudobinary solid solution is also discussed.

  5. HgCdTe e-APD detector arrays with single photon sensitivity for space lidar applications

    NASA Astrophysics Data System (ADS)

    Sun, Xiaoli; Abshire, James B.; Beck, Jeffrey D.

    2014-05-01

    A multi-element HgCdTe electron initiated avalanche photodiode (e-APD) array has been developed for space lidar. The detector array was fabricated with 4.3μm cutoff HgCdTe with a spectral response from 0.4 to 4.3 μm. We have demonstrated a 4x4 e-APD array with 80 μm square elements followed by a custom cryogenic CMOS read-out integrated circuit (ROIC). The device operates at 77K inside a small closed-cycle cooler-Dewar with the support electronics integrated in a field programmable gate array. Measurements showed a unity gain quantum efficiency of about 90% at 1.5-1.6 μm wavelength. The bulk dark current of the HgCdTe e-APD at 77K was less than 50,000 input referred electrons/s at 12 V APD bias where the APD gain was 620 and the measured noise equivalent power (NEP) was 0.4 fW/Hz1/2. The electrical bandwidth of the device was about 6 MHz, mostly limited by the ROIC, but sufficient for the lidar application. Although the devices were designed for low bandwidth pulse detections, the high gain and low dark current enabled them to be used for single photon detections. Because the APD was biased below the break-down voltage, the output is linear to the input signal and there were no nonlinear effect such as dead-time and afterpulsing, and no need for gated operation. A new series of HgCdTe e-APDs have also been developed with a much wider bandwidth ROIC and higher APD gain, which is expected to give a much better performance in single photon detections.

  6. Sequencing Batch Reactor (SBR) for the removal of Hg2+ and Cd2+ from synthetic petrochemical factory wastewater.

    PubMed

    Malakahmad, Amirhossein; Hasani, Amirhesam; Eisakhani, Mahdieh; Isa, Mohamed Hasnain

    2011-07-15

    Petrochemical factories which manufacture vinyl chloride monomer and poly vinyl chloride (PVC) are among the largest industries which produce wastewater contains mercury and cadmium. The objective of this research is to evaluate the performance of a lab-scale Sequencing Batch Reactor (SBR) to treat a synthetic petrochemical wastewater containing mercury and cadmium. After acclimatization of the system which lasted 60 days, the SBR was introduced to mercury and cadmium in low concentrations which then was increased gradually to 9.03±0.02 mg/L Hg and 15.52±0.02 mg/L Cd until day 110. The SBR performance was assessed by measuring Chemical Oxygen Demand, Total and Volatile Suspended Solids as well as Sludge Volume Index. At maximum concentrations of the heavy metals, the SBR was able to remove 76-90% of Hg(2+) and 96-98% of Cd(2+). The COD removal efficiency and MLVSS (microorganism population) in the SBR was affected by mercury and cadmium concentrations in influent. Different species of microorganisms such as Rhodospirilium-like bacteria, Gomphonema-like algae, and sulfate reducing-like bacteria were identified in the system. While COD removal efficiency and MLVSS concentration declined during addition of heavy metals, the appreciable performance of SBR in removal of Hg(2+) and Cd(2+) implies that the removal in SBR was not only a biological process, but also by the biosorption process of the sludge.

  7. Density, Electrical Conductivity and Viscosity of Hg(sub 0.8)Cd(sub 0.2)Te Melt

    NASA Technical Reports Server (NTRS)

    Li, C.; Scripa, R. N.; Ban, H.; Lin, B.; Su, C.-H.; Lehoczky, S. L.

    2004-01-01

    The density, viscosity, and electrical conductivity of Hg(sub 0.8)Cd(sub 0.2)Te melt were measures as a function of temperature. A pycnometric method was used to measure the melt density in the temperature range of 1072 to 1122 K. The viscosity and electrical conductivity were determined using a transient torque method from 1068 to 1132 K. The density result from this study is within 0.3% of the published data. However, the current viscosity result is approximately 30% lower than the existing data. The electrical conductivity of Hg(sub 0.8)Cd(sub 0.2)Te melt as a function of temperature, which is not available in the literature, is also determined. The analysis of the temperature dependent electrical conductivity and the relationship between the kinematic viscosity and density indicated that the structure of the melt appeared to be homogeneous when the temperature was above 1090 K. A structural transition occurred in the Hg(sub 0.8)Cd(sub 0.2)Te melt as the temperature was decreased to below 1090 K.

  8. Advanced methods for preparation and characterization of infrared detector materials. [crystallization and phase diagrams of Hg sub 1-x Cd sub x Te

    NASA Technical Reports Server (NTRS)

    Lehoczy, S. L.

    1979-01-01

    Crystal growth of Hg sub 1-x Cd sub x Te and density measurements of ingot slices are discussed. Radial compositional variations are evaluated from the results of infrared transmission edge mapping. The pseudo-binary HgTe-CdTe phase diagram is examined with reference to differential thermal analysis measurements. The phase equilibria calculations, based on the 'regular association solution' theory (R.A.S.) are explained and, using the obtained R.A.S. parameters, the activities of Hg, Cd, and Te vapors and their partial pressures over the pseudo-binary melt are calculated.

  9. Indirect exchange interaction between magnetic impurities in the two-dimensional topological insulator based on CdTe/HgTe/CdTe quantum wells

    NASA Astrophysics Data System (ADS)

    Kurilovich, P. D.; Kurilovich, V. D.; Burmistrov, I. S.

    2016-10-01

    We study indirect exchange interaction between magnetic impurities in the (001) CdTe/HgTe/CdTe symmetric quantum well. We consider low temperatures and the case of the chemical potential placed in the energy gap of the two-dimensional quasiparticle spectrum. We find that the indirect exchange interaction is suppressed exponentially with the distance between magnetic impurities. The presence of inversion asymmetry results in oscillations of the indirect exchange interaction with the distance and generates additional terms which are noninvariant under rotations in the (001) plane. The indirect exchange interaction matrix has complicated structure with some terms proportional to the sign of the energy gap.

  10. RIE-induced n-on-p junction HgCdTe photodiodes: effects of passivant technology on bake stability

    NASA Astrophysics Data System (ADS)

    Dell, John M.; Antoszewski, Jarek; White, J. K.; Pal, Ravindra; Nguyen, Thuyen; Musca, Charles A.; Faraone, Lorenzo

    2001-11-01

    Reactive ion etching (RIE) of HgCdTe using CH4:H2 is known to generate p- to n-type conversion in both intrinsically doped and extrinsically doped p-type HgCdTe. The use of RIE to form n-on-p junctions in planar diodes has a number of advantages including state of the art diode performance, high uniformity, passivation of the junction at the surface throughout processing, the possibility of the formation of deep junctions, and removal of any need for high temperature processing after junction formation. However, it has long been believed that H2 based plasma junction formation techniques will be long-term unstable. Initial results are presented indicating that surface passivation plays a major role in determining the stability of planar junctions formed using H2 based RIE. Comparisons of ZnS and CdTe passivation for n-on p-junctions formed on x approximately 0.3 Hg1-xCdxTe show dramatic differences in 2 to 3 hour, 80 degrees C bake stability tests. Diodes fabricated using either passivant initially exhibit R0A performance close to the theoretical limit, but are degraded after a 2 hour, 80 degrees C bake. Diodes with CdTe passivation have moderate performance as fabricated, but exhibit improvement rather than degradation after 3 hour, 80 degrees C bake. Such results indicate that planar junctions formed using H2 based RIE may offer a viable technology for low cost, highly uniform, large area IR detector arrays if passivation issues are satisfactorily resolved. Finally, a dual layer ZnS/CdTe passivation process is introduced which results in bake-stable devices after a 17 hour, 80 degrees C bake.

  11. Pb-Zn-Cd-Hg multi isotopic characterization of the Loire River Basin, France

    NASA Astrophysics Data System (ADS)

    Millot, R.; Widory, D.; Innocent, C.; Guerrot, C.; Bourrain, X.; Johnson, T. M.

    2012-12-01

    The contribution of human activities such as industries, agriculture and domestic inputs, becomes more and more significant in the chemical composition (major ions and pollutants such as metals) of the dissolved load of rivers. Furthermore, this influence can also be evidenced in the suspended solid matter known to play an important role in the transport of heavy metals through river systems. Human factors act as a supplementary key process. Therefore the mass-balance for the budget of catchments and river basins include anthropogenic disturbances. The Loire River in central France is approximately 1010 km long and drains an area of 117,800 km2. Initially, the Loire upstream flows in a south to north direction originating in the Massif Central, and continues up to the city of Orléans, 650 km from the source. In the upper basin, the bedrock is old plutonic rock overlain by much younger volcanic rocks. The Loire River then follows a general east to west direction to the Atlantic Ocean. The intermediate basin includes three major tributaries flowing into the Loire River from the left bank: the Cher, the Indre and the Vienne rivers; the main stream flows westward and its valley stretches toward the Atlantic Ocean. Here, the Loire River drains the sedimentary series of the Paris Basin, mainly carbonate deposits. The lower Loire basin drains pre-Mesozoic basement of the Armorican Massif and its overlying Mesozoic to Cenozoic sedimentary deposits. The Loire River is one of the main European riverine inputs to the Atlantic ocean. Here we are reporting concentration and isotope data for heavy metals Zn-Cd-Pb-Hg in river waters and suspended sediments from the Loire River Basin. In addition, we also report concentration and isotope data for these metals for the different industrial sources within the Loire Basin, as well as data for biota samples such as mussels and oysters from the Bay of Biscay and North Brittany. These organisms are known to be natural accumulators of

  12. Extended x-ray absorption fine structure study of arsenic in HgCdTe: p-type doping linked to nonsubstitutional As incorporation in an unknown AsHg{sub 8} structure

    SciTech Connect

    Biquard, X.; Alliot, I.; Ballet, P.

    2009-11-15

    An extended x-ray absorption fine structure (EXAFS) investigation has been carried out on arsenic-doped Hg{sub 70}Cd{sub 30}Te samples. The incorporation of atomic arsenic has been achieved using a nonconventional radio-frequency plasma source in a molecular beam epitaxy reactor. Two samples from the same epitaxial wafer have been studied. One underwent a 400 deg. C activation annealing under Hg pressure, leading to n to p-type conversion. In the commonly admitted scenario, this conversion is associated with the annealing-induced migration of As from a Hg site to a Te site. This study shows that this is not the case. Before annealing, As is found to be involved in noncrystalline structures: 50% inside an As{sub 2}Te{sub 3} chalcogenide glass and 50% inside a new AsHg{sub 8} compact structure. After annealing, the As{sub 2}Te{sub 3} chalcogenide glass disappears, 31% of As occupies Hg sites and 69% incorporates inside this new AsHg{sub 8} compact structure that occupies Te sites. The EXAFS results are in excellent agreement with 77 K Hall-effect measurements. The new AsHg{sub 8} structure is found to have an acceptor behavior. Overall, this study provides an entirely new vision of extrinsic p-type doping of HgCdTe as well as the first experimental evidence of As site transfer induced by annealing.

  13. Self-regulated route to ternary hybrid nanocrystals of Ag-Ag2S-CdS with near-infrared photoluminescence and enhanced photothermal conversion

    NASA Astrophysics Data System (ADS)

    Zhu, Guoxing; Bao, Chunlin; Liu, Yuanjun; Shen, Xiaoping; Xi, Chunyan; Xu, Zheng; Ji, Zhenyuan

    2014-09-01

    Developing hybrid nanocrystals is a hot topic in materials science. Herein, a ternary hybrid nanocrystal, Ag-Ag2S-CdS, combining near infrared emission and photothermal conversion properties was demonstrated. The ternary Ag-Ag2S-CdS hybrid nanocrystals with cubic shape and uniform size were synthesized by a simple one-pot and one-step colloidal method. The growth process is self-regulated with the formation order of Ag2S, Ag, and CdS, sequentially. The formation of Ag originates from the partial reduction of Ag2S, while the formation of CdS is through an Ag2S catalytic mechanism based on its superionic feature. The obtained ternary hybrid nanocrystals show near infrared emission and photothermal conversion properties in a lab-on-a-particle system. Importantly, an enhanced effect is observed for the photothermal conversion, which is mainly due to the presence of heterointerfaces among the crystals. This work will not only advance the synthesis chemistry of multi-component hybrid nanocrystals but also provide a possible route for the design of advanced multi-model materials used in bio-related fields.Developing hybrid nanocrystals is a hot topic in materials science. Herein, a ternary hybrid nanocrystal, Ag-Ag2S-CdS, combining near infrared emission and photothermal conversion properties was demonstrated. The ternary Ag-Ag2S-CdS hybrid nanocrystals with cubic shape and uniform size were synthesized by a simple one-pot and one-step colloidal method. The growth process is self-regulated with the formation order of Ag2S, Ag, and CdS, sequentially. The formation of Ag originates from the partial reduction of Ag2S, while the formation of CdS is through an Ag2S catalytic mechanism based on its superionic feature. The obtained ternary hybrid nanocrystals show near infrared emission and photothermal conversion properties in a lab-on-a-particle system. Importantly, an enhanced effect is observed for the photothermal conversion, which is mainly due to the presence of

  14. Transmission electron microscopy of the induced damage by argon implantation in (111) HgCdTe at room temperature

    NASA Astrophysics Data System (ADS)

    Aguirre, Myriam H.; Cánepa, Horacio R.; Walsöe de Reca, Noemí E.

    2002-11-01

    HgCdTe (MCT) is an important semiconductor material used for infrared photovoltaic detectors. Although ion implantation is a widely used technique in the manufacture of devices based on MCT to obtain n/p junctions, a detailed understanding of the n-type behavior of the unannealed damage region has not yet been established. In this work, n/p junctions were formed by Ar++ implantation on MCT (111) grown by the isothermal vapor phase epitaxy method. Structural damage after implantation for different implantation doses (1013, 1014, and 1015 Ar++/cm2) was evaluated by transmission electron microscopy. At high doses, damage distribution exhibits a double region of defects. These were mainly vacancy dislocation loops and lines in the first region, whereas the second zone exhibited small dislocation loops. The observed n-type behavior after implantation was attributed to the generation and diffusion of Hg from the damaged region.

  15. Large-Format HgCdTe Dual-Band Long-Wavelength Infrared Focal-Plane Arrays

    NASA Astrophysics Data System (ADS)

    Smith, E. P. G.; Venzor, G. M.; Gallagher, A. M.; Reddy, M.; Peterson, J. M.; Lofgreen, D. D.; Randolph, J. E.

    2011-08-01

    Raytheon Vision Systems (RVS) continues to further its capability to deliver state-of-the-art high-performance, large-format, HgCdTe focal-plane arrays (FPAs) for dual-band long-wavelength infrared (L/LWIR) detection. Specific improvements have recently been implemented at RVS in molecular-beam epitaxy (MBE) growth and wafer fabrication and are reported in this paper. The aim of the improvements is to establish producible processes for 512 × 512 30- μm-unit-cell L/LWIR FPAs, which has resulted in: the growth of triple-layer heterojunction (TLHJ) HgCdTe back-to-back photodiode detector designs on 6 cm × 6 cm CdZnTe substrates with 300-K Fourier-transform infrared (FTIR) cutoff wavelength uniformity of ±0.1 μm across the entire wafer; demonstration of detector dark-current performance for the longer-wavelength detector band approaching that of single-color liquid-phase epitaxy (LPE) LWIR detectors; and uniform, high-operability, 512 × 512 30- μm-unit-cell FPA performance in both LWIR bands.

  16. Development of High-Performance eSWIR HgCdTe-Based Focal-Plane Arrays on Silicon Substrates

    NASA Astrophysics Data System (ADS)

    Park, J. H.; Pepping, J.; Mukhortova, A.; Ketharanathan, S.; Kodama, R.; Zhao, J.; Hansel, D.; Velicu, S.; Aqariden, F.

    2016-09-01

    We report the development of high-performance and low-cost extended short-wavelength infrared (eSWIR) focal-plane arrays (FPAs) fabricated from molecular beam epitaxial (MBE)-grown HgCdTe on Si-based substrates. High-quality n-type eSWIR HgCdTe (cutoff wavelength ˜2.68 μm at 77 K, electron carrier concentration 5.82 × 1015 cm-3) layers were grown on CdTe/Si substrates by MBE. High degrees of uniformity in composition and thickness were demonstrated over three-inch areas, and low surface defect densities (voids 9.56 × 101 cm-2, micro-defects 1.67 × 103 cm-2) were measured. This material was used to fabricate 320 × 256 format, 30 μm pitch FPAs with a planar device architecture using arsenic implantation to achieve p-type doping. The dark current density of test devices showed good uniformity between 190 K and room temperature, and high-quality eSWIR imaging from hybridized FPAs was obtained with a median dark current density of 2.63 × 10-7 A/cm2 at 193 K with a standard deviation of 1.67 × 10-7 A/cm2.

  17. Hole Transport in Arsenic-Doped Hg1- x Cd x Te with x ≥ 0.5

    NASA Astrophysics Data System (ADS)

    Umana-Membreno, G. A.; Kala, H.; Bains, S.; Akhavan, N. D.; Antoszewski, J.; Maxey, C. D.; Faraone, L.

    2016-09-01

    Hole transport in arsenic-doped p-type Hg1- x Cd x Te epitaxial layers with x ≥ 0.5 has been studied employing Hall-effect measurements and theoretical modeling of hole scattering mechanisms. The hole transport parameters extracted from four different Hg1- x Cd x Te films with x = 0.50, 0.56-0.58, 0.65, and 0.80, were analyzed using an iterative solution of Boltzmann's transport equation. Hole mobilities in the samples with x values of 0.5 and 0.56-0.58 were found to be predominantly limited by ionized impurity scattering, and exhibited relatively high impurity compensation ratios ≥2. The sample with x = 0.65 exhibited the highest hole mobility, a low compensation ratio of 1.05, and mobility characteristics were limited predominantly by polar optical phonon scattering at temperatures ≥200 K. Hole mobility in the sample with x = 0.80 was found to be limited by polar optical phonon scattering and ionized impurity scattering (compensation ratio 1.20-1.56). Although the sample temperatures employed were not sufficiently low to unambiguously discriminate the scattering strength of static strain and dislocations, the experimental hole mobility characteristics cannot be adequately modeled if these two mechanisms are neglected. The ionization energy of the arsenic acceptor impurities was found to exhibit a quadratic dependence on the CdTe mole fraction.

  18. Third-order nonlinear optical response of Ag-CdSe/PVA hybrid nanocomposite

    NASA Astrophysics Data System (ADS)

    Tripathi, S. K.; Kaur, Ramneek; Kaur, Jaspreet; Sharma, Mamta

    2015-09-01

    Hybrid nanocomposites of II-VI semiconductor nanoparticles are gaining great interest in nonlinear optoelectronic devices. Present work includes the characterization of CdSe polymer nanocomposite prepared by chemical in situ technique. From X-ray diffraction, the hexagonal wurtzite structure of nanoparticles has been confirmed with spherical morphology from transmission electron microscopy. Ag-CdSe hybrid polymer nanocomposite has been prepared chemically at different Ag concentrations. The presence of Ag in hybrid nanocomposite has been confirmed with energy-dispersive X-ray spectroscopy. The effect of varying Ag concentration on the linear and nonlinear optical properties of the nanocomposites has been studied. In linear optical parameters, the linear absorption coefficient, refractive index, extinction coefficient and optical conductivity have been calculated. The third-order nonlinear optical properties have been observed with open- and closed-aperture Z-scan technique. The large nonlinear refractive index ~10-5 cm2/W with self-focusing behaviour is due to the combined effect of quantum confinement and thermo-optical effects. The enhanced nonlinearity with increasing Ag content is due to the surface plasmon resonance, which enhances the local electric field near the nanoparticle surface. Thus, Ag-CdSe hybrid polymer nanocomposite has favourable nonlinear optical properties for various optoelectronic applications.

  19. Lattice defects in semiconducting Hg/1-x/Cd/x/Te alloys. I - Defect structure of undoped and copper doped Hg/0.8/Cd/0.2/Te. II - Defect structure of indium-doped Hg/0.8/Cd/0.2/Te

    NASA Technical Reports Server (NTRS)

    Vydyanath, H. R.

    1981-01-01

    Hall effect and mobility measurements were conducted on undoped Hg(0.8)Cd(0.2)Te crystals which were quenched to room temperature after being subjected to equilibration at temperatures ranging from 400 to 655 C in various Hg atmospheres. The variation of the hole concentration in the cooled crystals at 77 K as a function of Hg's partial pressure at the equilibration temperature, together with a comparison of the hole mobility in the undoped samples with that in copper-doped ones, yields a defect model for the undoped crystals according to which they are intrinsic at the equilibration temperatures and the native acceptor defects are doubly ionized. In the second part of this paper, the effects of indium doping are considered. The concentration of electrons obtained in the cooled crystals was found to be lower than the intrinsic carrier concentration at the equilibration temperatures. A defect model is proposed according to which most of the indium is incorporated as In2Te3(s) dissolved in the crystal, with only a small fraction of indium acting as single donors occupying Hg lattice sites.

  20. A Highly Sensitive Multi-Element HgCdTe E-APD Detector for IPDA Lidar Applications

    NASA Technical Reports Server (NTRS)

    Beck, Jeff; Welch, Terry; Mitra, Pradip; Reiff, Kirk; Sun, Xiaoli; Abshire, James

    2014-01-01

    An HgCdTe electron avalanche photodiode (e-APD) detector has been developed for lidar receivers, one application of which is integrated path differential absorption lidar measurements of such atmospheric trace gases as CO2 and CH4. The HgCdTe APD has a wide, visible to mid-wave-infrared, spectral response, high dynamic range, substantially improved sensitivity, and an expected improvement in operational lifetime. A demonstration sensor-chip assembly consisting of a 4.3 lm cutoff HgCdTe 4 9 4 APD detector array with 80 micrometer pitch pixels and a custom complementary metal-oxide-semiconductor readout integrated circuit was developed. For one typical array the APD gain was 654 at 12 V with corresponding gain normalized dark currents ranging from 1.2 fA to 3.2 fA. The 4 9 4 detector system was characterized at 77 K with a 1.55 micrometer wavelength, 1 microsecond wide, laser pulse. The measured unit gain detector photon conversion efficiency was 91.1%. At 11 V bias the mean measured APD gain at 77 K was 307.8 with sigma/mean uniformity of 1.23%. The average, noise-bandwidth normalized, system noise-equivalent power (NEP) was 1.04 fW/Hz(exp 1/2) with a sigma/mean of 3.8%. The measured, electronics-limited, bandwidth of 6.8 MHz was more than adequate for 1 microsecond pulse detection. The system had an NEP (3 MHz) of 0.4 fW/Hz(exp 1/2) at 12 V APD bias and a linear dynamic range close to 1000. A gain-independent quantum-limited SNR of 80% of full theoretical was indicative of a gain-independent excess noise factor very close to 1.0 and the expected APD mode quantum efficiency.

  1. Performance of MWIR and SWIR HgCdTe-based focal plane arrays at high operating temperatures

    NASA Astrophysics Data System (ADS)

    Melkonian, Leon; Bangs, James; Elizondo, Lee; Ramey, Ron; Guerrero, Ernesto

    2010-04-01

    Raytheon Vision Systems (RVS) is producing large format, high definition HgCdTe-based MWIR and SWIR focal plane arrays (FPAs) with pitches of 15 μm and smaller for various applications. Infrared sensors fabricated from HgCdTe have several advantages when compared to those fabricated from other materials -- such as a highly tunable bandgap, high quantum efficiencies, and R0A approaching theoretical limits. It is desirable to operate infrared sensors at elevated operating temperatures in order to increase the cooler life and reduce the required system power. However, the sensitivity of many infrared sensors, including those made from HgCdTe, declines significantly above a certain temperature due to the noise resulting from increasing detector dark current. In this paper we provide performance data on a MWIR and a SWIR focal plane array operating at temperatures up to 160K and 170K, respectively. The FPAs used in the study were grown by molecular beam epitaxy (MBE) on silicon substrates, processed into a 1536x1024 format with a 15 μm pixel pitch, and hybridized to a silicon readout integrated circuit (ROIC) via indium bumps to form a sensor chip assembly (SCA). This data shows that the noise equivalent delta temperature (NEDT) is background limited at f/3.4 in the SWIR SCA (cutoff wavelength of 3.7 μm at 130K) up to 140K and in the MWIR SCA (cutoff wavelength of 4.8 μm at 115K) up to 115K.

  2. Terahertz radiation from Cd{sub x}Hg{sub 1-x}Te photoexcited by femtosecond laser pulses

    SciTech Connect

    Krotkus, A.; Adomavicius, R.; Molis, G.; Urbanowicz, A.; Eusebe, H.

    2004-10-01

    Terahertz radiation from Cd{sub x}Hg{sub 1-x}Te samples excited by femtosecond Ti:sapphire laser pulses were measured by using an ultrafast photoconductive antenna manufactured from low-temperature grown GaAs. Terahertz fields radiated by the samples of all three investigated alloy compositions with x=0, 0.2, and 0.3 were of the same order of magnitude. No azimuthal angle dependence of the radiated signal was detected, which evidences that linear current surge effect is dominating over nonlinear optical rectification.

  3. Anthropogenic and geogenic Cd, Hg, Pb and Se sources of contamination in a brackish aquifer below agricultural fields

    NASA Astrophysics Data System (ADS)

    Mastrocicco, Micòl; Colombani, Nicolò; Di Giuseppe, Dario; Faccini, Barbara; Ferretti, Giacomo; Coltorti, Massimo

    2015-04-01

    Groundwater quality is often threatened by industrial, agricultural and land use practices (anthropogenic input). In deltaic areas is however difficult to distinguish between geogenic and anthropogenic inorganic contaminants pollution, since these phenomena can influence each other and often display a seasonal cycling. The effect of geogenic groundwater ionic strength (>10 g/l) on the mobility of trace elements like Cd, Hg, Pb and Se was studied in combination with the anthropogenic sources of these elements (fertilizers) in a shallow aquifer. The site is located in the Po river plain (Northern Italy) in an agricultural field belonging to a reclaimed deltaic environment, near Codigoro town. It is 6 ha wide and is drained by a subsurface drainage system made of PVC tile drains with a slope of 3‰, which provides gravity drainage towards two ditches that in turn discharge in a main channel. The whole area has been intensively cultivated with cereal rotation since 1960, mainly using synthetic urea as nitrogen fertilizer at an average rate of 180 kg-N/ha/y and pig slurry at an average rate of 60 kg-N/ha/y. The sediments were analyzed for major and trace elements via XRF, while major ions in groundwater were analyzed via IC and trace elements via ICP-MS. Three monitoring wells, with an inner diameter of 2 cm and screened down to 4 m below ground level, were set up in the field and sampled every four month from 2012 to 2014. The use of intensive depth profiles with resolution of 0.5 m in three different locations, gave insights into groundwater and sediment matrix interactions. To characterize the anthropogenic inputs synthetic urea and pig slurry were analyzed for trace elements via ICP-MS. The synthetic urea is a weak source of Cd and Hg (~1 ppb), while Se and Pb are found below detection limits. The pig slurry is a much stronger source of Se (~19 ppb) and Pb (~23 ppb) and a weak source of Cd (~3 ppb) and Hg (~2 ppb). Although, the mass loading rate pig slurry is

  4. Toward selective, sensitive, and discriminative detection of Hg(2+) and Cd(2+)via pH-modulated surface chemistry of glutathione-capped gold nanoclusters.

    PubMed

    Huang, Pengcheng; Li, Sha; Gao, Nan; Wu, Fangying

    2015-11-01

    Heavy metal pollution can exert severe effects on the environment and human health. Simple, selective, and sensitive detection of heavy metal ions, especially two or more, using a single probe, is thereby of great importance. In this study, we report a new and facile strategy for discriminative detection of Hg(2+) and Cd(2+) with high selectivity and sensitivity via pH-modulated surface chemistry of the glutathione-capped gold NCs (GSH-Au NCs). By simply adjusting pH values of the colloidal solution of the NCs, Hg(2+) could specifically turn off the fluorescence under acidic pH, however, Cd(2+) could exclusively turn on the fluorescence under alkaline pH. This enables the NCs to serve as a dual fluorescent sensor for Hg(2+) and Cd(2+). We demonstrate that these two opposing sensing modes are presumably due to different interaction mechanisms: Hg(2+) induces aggregation by dissociating GSH from the Au surface via robust coordination and, Cd(2+) could passivate the Au surface by forming a Cd-GSH complex with a compact structure. Finally, the present strategy is successfully exploited to separately determine Hg(2+) and Cd(2+) in environmental water samples.

  5. Toward selective, sensitive, and discriminative detection of Hg(2+) and Cd(2+)via pH-modulated surface chemistry of glutathione-capped gold nanoclusters.

    PubMed

    Huang, Pengcheng; Li, Sha; Gao, Nan; Wu, Fangying

    2015-11-01

    Heavy metal pollution can exert severe effects on the environment and human health. Simple, selective, and sensitive detection of heavy metal ions, especially two or more, using a single probe, is thereby of great importance. In this study, we report a new and facile strategy for discriminative detection of Hg(2+) and Cd(2+) with high selectivity and sensitivity via pH-modulated surface chemistry of the glutathione-capped gold NCs (GSH-Au NCs). By simply adjusting pH values of the colloidal solution of the NCs, Hg(2+) could specifically turn off the fluorescence under acidic pH, however, Cd(2+) could exclusively turn on the fluorescence under alkaline pH. This enables the NCs to serve as a dual fluorescent sensor for Hg(2+) and Cd(2+). We demonstrate that these two opposing sensing modes are presumably due to different interaction mechanisms: Hg(2+) induces aggregation by dissociating GSH from the Au surface via robust coordination and, Cd(2+) could passivate the Au surface by forming a Cd-GSH complex with a compact structure. Finally, the present strategy is successfully exploited to separately determine Hg(2+) and Cd(2+) in environmental water samples. PMID:26347906

  6. High operating temperature SWIR p+-n FPA based on MBE-grown HgCdTe/Si(0 1 3)

    NASA Astrophysics Data System (ADS)

    Bazovkin, V. M.; Dvoretsky, S. A.; Guzev, A. A.; Kovchavtsev, A. P.; Marin, D. V.; Polovinkin, V. G.; Sabinina, I. V.; Sidorov, G. Yu.; Tsarenko, A. V.; Vasil'ev, V. V.; Varavin, V. S.; Yakushev, M. V.

    2016-05-01

    The characteristics of SWIR (1.6-3 μm) 320 × 256 and 1024 × 1024 focal plane arrays (FPA's) based on n-type In-doped HgCdTe heteroepitaxial layers are reported. The HgCdTe layers were grown by molecular beam epitaxy on silicon substrates with ZnTe and CdTe buffer layers. p-n junctions were formed by arsenic ion implantation into HgCdTe film. Reverse current in the temperature range from 210 to 330 K was found to be limited by the diffusion mechanism. At the same time in the temperature range from 140 to 210 K the reverse current was dominated by the thermal generation of charge carriers through deep traps located in the middle of the band gap. At 170 K NETD was less than 40 mK.

  7. Properties of MIS structures based on graded-gap HgCdTe grown by molecular beam epitaxy

    SciTech Connect

    Voitsekhovskii, A. V. Nesmelov, S. N.; Dzyadookh, S. M.; Varavin, V. S.; Dvoretskii, S. A.; Mikhailov, N. N.; Sidorov, Yu. G.; Vasiliev, V. V.

    2008-11-15

    The effect of near-surface graded-gap layers on the electrical characteristics of MIS structures fabricated based on heteroepitaxial Hg{sub 1-x} Cd{sub x}Te films grown by molecular beam epitaxy with a two-layer SiO{sub 2}/Si{sub 3}N{sub 4} insulator and anodic oxide film is studied experimentally. It is shown that a larger modulation of capacitance (depth and width of the valley) is observed compared with the structures without the graded-gap layer. The field dependences of photovoltage of MIS structures with the graded-gap layers had a classical form and were characterized by a drop only in the enrichment region. For the structures without the graded-gap layer with x = 0.22, a drop in the voltage dependence of the photocurrent is observed in the region of pronounced inversion. This drop is governed by limitation of the space charge region by processes of tunneling generation via deep levels. The properties of the HgCdTe-insulator interfaces are studied.

  8. The spatial and temporal trends of Cd, Cu, Hg, Pb and Zn in Seine River floodplain deposits (1994-2000)

    USGS Publications Warehouse

    Grosbois, C.; Meybeck, Michel; Horowitz, A.; Ficht, A.

    2006-01-01

    Fresh floodplain deposits (FD), from 11 key stations, covering the Seine mainstem and its major tributaries (Yonne, Marne and Oise Rivers), were sampled from 1994 to 2000. Background levels for Cd, Cu, Hg, Pb, and Zn were established using prehistoric FD and actual bed sediments collected in small forested sub-basins in the most upstream part of the basin. Throughout the Seine River Basin, FD contain elevated concentrations of Cd, Cu, Hg, Pb and Zn compared to local background values (by factors > twofold). In the Seine River Basin, trace element concentrations display substantial downstream increases as a result of increasing population densities, particularly from Greater Paris (10 million inhabitants), and reach their maxima at the river mouth (Poses). These elevated levels make the Seine one of the most heavily impacted rivers in the world. On the other hand, floodplain-associated trace element levels have declined over the past 7 years. This mirrors results from contemporaneous suspended sediment surveys at the river mouth for the 1984-1999 period. Most of these temporal declines appear to reflect reductions in industrial and domestic solid wastes discharged from the main Parisian sewage plant (Seine Aval). ?? 2005 Elsevier B.V. All rights reserved.

  9. Theoretical Modeling of HOT HgCdTe Barrier Detectors for the Mid-Wave Infrared Range

    NASA Astrophysics Data System (ADS)

    Martyniuk, P.; Gawron, W.; Rogalski, A.

    2013-11-01

    This paper reports on theoretical modeling of medium-wavelength infrared HgCdTe barrier infrared detector (BIRD) photoelectrical performance. BIRD HgCdTe detectors were simulated with the commercially available software APSYS. Detailed analysis of the detector performance such as dark current, photocurrent, resistance-area product, detectivity versus applied bias, operating temperature, and structural parameters (absorber doping, barrier composition) was performed to determine the optimal operating conditions. It is shown that higher operation temperature conditions achievable with commonly used thermoelectric coolers allow detectivities of D = 9.5 × 1010 cmHz1/2/W and D * = 1.5 × 1011 cmHz1/2/W at T = 200 K to be obtained for the correct absorber doping for nBnnn+ and nBnpn+, respectively. R 0 A for the nBnnn+ detector was found to range from 200 Ω cm2 to 0.6 Ω cm2 at T = 200 K to 300 K, respectively.

  10. Ag2S/CdS/TiO2 Nanotube Array Films with High Photocurrent Density by Spotting Sample Method

    NASA Astrophysics Data System (ADS)

    Sun, Hong; Zhao, Peini; Zhang, Fanjun; Liu, Yuliang; Hao, Jingcheng

    2015-10-01

    Ag2S/CdS/TiO2 hybrid nanotube array films (Ag2S/CdS/TNTs) were prepared by selectively depositing a narrow-gap semiconductor—Ag2S (0.9 eV) quantum dots (QDs)—in the local domain of the CdS/TiO2 nanotube array films by spotting sample method (SSM). The improvement of sunlight absorption ability and photocurrent density of titanium dioxide (TiO2) nanotube array films (TNTs) which were obtained by anodic oxidation method was realized because of modifying semiconductor QDs. The CdS/TNTs, Ag2S/TNTs, and Ag2S/CdS/TNTs fabricated by uniformly depositing the QDs into the TNTs via the successive ionic layer adsorption and reaction (SILAR) method were synthesized, respectively. The X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectrum (XPS) results demonstrated that the Ag2S/CdS/TNTs prepared by SSM and other films were successfully prepared. In comparison with the four films of TNTs, CdS/TNTs, Ag2S/TNTs, and Ag2S/CdS/TNTs by SILAR, the Ag2S/CdS/TNTs prepared by SSM showed much better absorption capability and the highest photocurrent density in UV-vis range (320~800 nm). The cycles of local deposition have great influence on their photoelectric properties. The photocurrent density of Ag2S/CdS/TNTs by SSM with optimum deposition cycles of 6 was about 37 times that of TNTs without modification, demonstrating their great prospective applications in solar energy utilization fields.

  11. Local structure and site occupancy of Cd and Hg substitutions in CeTIn5 (T=Co, Rh, Ir)

    SciTech Connect

    Bauer, Eric D; Ronning, Filip; Thompson, J D; Sarrao, J L; Booth, C H; Bianchi, A D; Cho, J Y; Chan, J Y; Capan, C; Fisk, Z

    2009-01-01

    The CeTIn{sub 5} superconductors (T = Co, Rh, or Ir) have generated great interest due to their relatively high transition temperatures, non-Fermi liquid behavior, and their proximity to antiferromagnetic order and quantum critical points. In contrast to small changes with the T-species, electron doping in CeT(In{sub 1-x}M{sub x}){sub 5} with M = Sn and hole doping with Cd or Hg have a dramatic effect on the electronic properties at very low concentrations. The present work reports local structure measurements using the extended x-ray absorption fine-structure (EXAFS) technique that address the substituent atom distribution as a function of T, M, and x, in the vicinity of the superconducting phase. Together with previous measurements for M = Sn, the proportion of the M atom residing on the In(1) site, f{sub 1n(1)}, increases in the order M = Cd, Sn, and Hg, ranging from about 40% to 70%, showing a strong preference for each of these substituents to occupy the In(1) site (random occupation = 20%). In addition, f{sub In(1)} ranges from 70% to 100% for M = Hg in the order T = Co, Rh, and Ir. These fractions track the changes in the atomic radii of the various species, and help explain the sharp dependence of T{sub c} on substituting into the In site. However, it is difficult to reconcile the small concentrations of M with the dramatic changes in the ground state in the hole-doped materials with only an impurity scattering model. These results therefore indicate that while such substitutions have interesting local atomic structures with important electronic and magnetic consequences, other local changes in the electronic and magnetic structure are equally important in determining the bulk properties of these materials.

  12. Local structure and site occupancy of Cd and Hg substitutions in CeTIn_5 (T=Co, Rh, Ir)

    SciTech Connect

    Booth, Corwin H.; Bauer, Eric. D.; Bianchi, Andrea D.; Ronning, Fillip; Thompson, Joe D.; Sarrao, John L.; Cho, Jung Young; Chan, Julia Y.; Capan, Cigdem; Fisk, Zachary

    2009-04-22

    The CeTIn_5 superconductors (T=Co, Rh, or Ir) have generated great interest due to their relatively high transition temperatures, non-Fermi liquid behavior, and their proximity to antiferromagnetic order and quantum critical points. In contrast to small changes with the T-species, electron doping in CeT(In_1-x M_x)_5 with $M$=Sn and hole doping with Cd or Hg have a dramatic effect on the electronic properties at very low concentrations. The present work reports local structure measurements usingthe extended x-ray absorption fine-structure (EXAFS) technique that address the substituent atom distribution as a function of T, M, and x, in the vicinity of the superconducting phase. Together with previous measurements for M=Sn, the proportion of the $M$ atom residing on the In(1) site, f_\\textrm In(1), increases in the order M=Cd, Sn, and Hg, ranging from about 40\\percent to 70percent, showing a strong preference for each of these substituents to occupy the In(1) site (random occupation = 20percent). In addition, f_In(1) ranges from 70percent to 100percent for M=Hg in the order T=Co,Rh, and Ir. These fractions track the changes in the atomic radii of the various species, and help explain the sharp dependence of $T_c$ on substituting into the In site. However, it is difficult to reconcile the small concentrations of M with the dramatic changes in the ground state in the hole-doped materials with only an impurity scattering model. These results therefore indicate that while such substitutions have interesting local atomic structures with important electronic and magnetic consequences, other local changes in the electronic and magnetic structure are equally important in determining the bulk properties of these materials.

  13. Competing mechanism driving diverse pressure dependence of thermal conductivity of X Te (X =Hg ,Cd , and Zn)

    NASA Astrophysics Data System (ADS)

    Ouyang, Tao; Hu, Ming

    2015-12-01

    Effectively engineering the lattice thermal conductivity of materials is a key interest of the current thermal science community. Pressure or compressive strain is one of the most worthwhile processes to modify the thermal transport property of materials, due to its robust tunability and flexibility of realization. While it is well documented in the literature that the application of hydrostatic pressure normally increases the thermal conductivity of bulk materials, little work has been performed on abnormal pressure-dependent thermal conductivity and the governing mechanism has not been fully understood yet. In this paper, taking bulk telluride systems X Te (X =Hg ,Cd ,Zn ) as examples, we show, by combining first-principle calculation and the phonon Boltzmann transport equation, that the thermal conductivity presents diverse pressure dependence although they belong to the same group. The thermal conductivity of ZnTe is independent of pressure, while abnormal negative pressure dependence of thermal conductivity is observed in HgTe. As for CdTe, the trend falls in between HgTe and ZnTe and relies largely on the temperature. By comparing the key contributors of the lattice thermal conductivity, we find that the diverse pressure dependence of the lattice thermal conductivity is governed by the competition between the enhancement of group velocity of longitudinal acoustic and optic modes and the reduction of phonon relaxation time of transverse acoustic modes, with both effects being fully quantified by our calculation. Comparison with traditional bulk systems such as silicon further underpins the governing mechanism. The correlation between the diverse thermal transport phenomena and the nature of the atomic bonding is also qualitatively established. These findings are expected to deepen our understanding of manipulating phonon transport of bulk materials via simple compressive strain and are also helpful for related applications, such as optimizing thermoelectric

  14. Synthesis, Characterization and Thermal Studies of Zn(II), Cd(II) and Hg(II) Complexes of N-Methyl-N-Phenyldithiocarbamate: The Single Crystal Structure of [(C6H5)(CH3)NCS2]4Hg2

    PubMed Central

    Onwudiwe, Damian C.; Ajibade, Peter A.

    2011-01-01

    Zn(II), Cd(II) and Hg(II) complexes of N-methyl-N-phenyl dithiocarbamate have been synthesized and characterized by elemental analysis and spectral studies (IR, 1H and 13C-NMR). The single crystal X-ray structure of the mercury complex revealed that the complex contains a Hg centre with a distorted tetrahedral coordination sphere in which the dinuclear Hg complex resides on a crystallographic inversion centre and each Hg atom is coordinated to four S atoms from the dithiocarbamate moiety. One dithiocarbamate ligand acts as chelating ligand while the other acts as chelating bridging ligand between two Hg atoms, resulting in a dinuclear eight-member ring. The course of the thermal degradation of the complexes has been investigated using thermogravimetric and differential thermal analyses techniques. Thermogravimetric analysis of the complexes show a single weight loss to give MS (M = Zn, Cd, Hg) indicating that they might be useful as single source precursors for the synthesis of MS nanoparticles and thin films. PMID:21673933

  15. Development of aluminum (Al5083)-clad ternary Ag In Cd alloy for JSNS decoupled moderator

    NASA Astrophysics Data System (ADS)

    Teshigawara, M.; Harada, M.; Saito, S.; Oikawa, K.; Maekawa, F.; Futakawa, M.; Kikuchi, K.; Kato, T.; Ikeda, Y.; Naoe, T.; Koyama, T.; Ooi, T.; Zherebtsov, S.; Kawai, M.; Kurishita, H.; Konashi, K.

    2006-09-01

    To develop Ag (silver)-In (indium)-Cd (cadmium) alloy decoupler, a method is needed to bond the decoupler between Al alloy (Al5083) and the ternary Ag-In-Cd alloy. We found that a better HIP condition was temperature, pressure and holding time at 803 K, 100 MPa and 10 min. for small test pieces ( ϕ22 mm in dia. × 6 mm in height). Hardened layer due to the formation of AlAg 2 was found in the bonding layer, however, the rupture strength of the bonding layer is more than 30 MPa, the calculated design stress. Bonding tests of a large size piece (200 × 200 × 30 mm 3), which simulated the real scale, were also performed according to the results of small size tests. The result also gave good bonding and enough required-mechanical-strength.

  16. Phase Stability and Electronic Structure of In-Free Photovoltaic Materials Cu2IISnSe4 (II: Zn, Cd, Hg)

    NASA Astrophysics Data System (ADS)

    Nakamura, Satoshi; Maeda, Tsuyoshi; Wada, Takahiro

    2011-05-01

    We have theoretically evaluated the phase stability and electronic structure of Cu2CdSnSe4 and Cu2HgSnSe4 and compared the results with those of Cu2ZnSnSe4. The enthalpies of formation for kesterite (KS), stannite (ST), and wurtz-stannite (WST) phases of Cu2ZnSnSe4 (CZTSe), Cu2CdSnSe4, and Cu2HgSnSe4 were calculated by first-principles calculations. In Cu2CdSnSe4 and Cu2HgSnSe4, the stannite (ST) phase is the most stable among these phases. The valence band maximum (VBM) of ST-type Cu2CdSnSe4 consists of antibonding orbitals of Cu 3d and Se 4p, while the conduction band minimum (CBM) consists of antibonding orbitals of Sn 5s and Se 4p. The VBM of Cu2HgSnSe4 also consist of antibonding orbitals of Cu 3d and Se 4p. However, the CBM of Cu2HgSnSe4 consists of antibonding orbitals of Hg 6s, Sn 5s, and Se 4p.

  17. Determination of Cd, Cr, Hg and Pb in plastics from waste electrical and electronic equipment by inductively coupled plasma mass spectrometry with collision-reaction interface technology.

    PubMed

    Santos, Mirian C; Nóbrega, Joaquim A; Cadore, Solange

    2011-06-15

    A procedure based on the use of a quadrupole inductively coupled plasma-mass spectrometer equipped with a collision-reaction interface (CRI) for control of spectral overlap interferences was developed for simultaneous determination of Cd, Cr, Hg, and Pb in plastics from waste electrical and electronic equipment (WEEE). The injection of H(2) and He (80 and 60 mL min(-1), respectively) into the sampled plasma, colliding and reacting with potentially interfering polyatomic ions, allows interference-free determination of chromium via its isotopes (52)Cr and (53)Cr that are freed from overlap due to the occurrence of (40)Ar(12)C(+), (40)Ar(12)C(1)H(+), (36)S(16)O(+) or (1)H(36)S(16)O(+). Cadmium, Hg and Pb were directly determined via their isotopes (110)Cd, (111)Cd, (112)Cd, (199)Hg, (200)Hg, (201)Hg, (202)Hg, (206)Pb, (207)Pb, and (208)Pb, without using CRI. The CRI can be quickly activated or deactivated before each analyte measurement. Limits of detection for (52)Cr were 0.04 or 0.14 μg L(-1) with He or H(2) injected in CRI. Cadmium and Pb have LODs between 0.02 and 0.08 μg L(-1) and Hg had 0.93-0.98 μg L(-1), without using CRI. Analyte concentrations for samples varied from 16 to 43, 1 to 11, 4 to 12, and 5 to 13 mg kg(-1) for Cr, Cd, Hg and Pb, respectively.

  18. High frequency of circulating HBcAg-specific CD8 T cells in hepatitis B infection: a flow cytometric analysis

    PubMed Central

    Matsumura, S; Yamamoto, K; Shimada, N; Okano, N; Okamoto, R; Suzuki, T; Hakoda, T; Mizuno, M; Higashi, T; Tsuji, T

    2001-01-01

    Viral antigen-specific T cells are important for virus elimination. We studied the hepatitis B virus (HBV)-specific T cell response using flow cytometry. Three phases of HBV infection were studied: Group A, HBeAg (+) chronic hepatitis; Group B, HBeAb (+) HBV carrier after seroconversion; and Group C, HBsAb (+) phase. Peripheral T cells were incubated with recombinant HB core antigen (HBcAg), and intracytoplasmic cytokines were analysed by flow cytometry. HBcAg-specific CD4 and CD8 T cells were identified in all three groups and the number of IFN-γpositive T cells was greater than TNF-α-positive T cells. The frequency of IFN-γ-positive CD4 and CD8 T cells was highest in Group C, compared with Groups A and B. No significant difference in the HBcAg-specific T cell response was observed between Group A and Group B. The HBcAg-specific CD8 T cell response was diminished by CD4 depletion, addition of antibody against human leucocyte antigen (HLA) class I, class II or CD40L. Cytokine-positive CD8 T cells without HBcAg stimulation were present at a high frequency (7 of 13 cases) in Group B, but were rare in other groups. HBcAg-specific T cells can be detected at high frequency by a sensitive flow cytometric analysis, and these cells are important for controlling HBV replication. PMID:11472405

  19. Development of electrodeposited ZnTe layers as window materials in ZnTe/CdTe/CdHgTe multi-layer solar cells

    SciTech Connect

    Islam, A.B.M.O. Chaure, N.B.; Wellings, J.; Tolan, G.; Dharmadasa, I.M.

    2009-02-15

    Zinc telluride (ZnTe) thin films have been deposited on glass/conducting glass substrates using a low-cost electrodeposition method. The resulting films have been characterized using various techniques in order to optimize growth parameters. X-ray diffraction (XRD) has been used to identify the phases present in the films. Photoelectrochemical (PEC) cell and optical absorption measurements have been performed to determine the electrical conductivity type, and the bandgap of the layers, respectively. It has been confirmed by XRD measurement that the deposited layers mainly consist of ZnTe phases. The PEC measurements indicate that the ZnTe layers are p-type in electrical conduction and optical absorption measurements show that their bandgap is in the range 2.10-2.20 eV. p-Type ZnTe window materials have been used in CdTe based solar cell structures, following new designs of graded bandgap multi-layer solar cells. The structures of FTO/ZnTe/CdTe/metal and FTO/ZnTe/CdTe/CdHgTe/metal have been investigated. The results are presented in this paper using observed experimental data.

  20. Synthesis and characterization of La11+xHg45-x and RE11Hg44.5 (RE = Nd, Sm) as hettotypes of the Sm11Cd45 structure type

    NASA Astrophysics Data System (ADS)

    Tambornino, Frank; Schwärzer, Kuno; Hoch, Constantin

    2016-10-01

    The mercury-rich amalgams La11+xHg45-x and RE11Hg44.5 (space group F4bar3m (No. 216), La11+xHg45-x : a = 21.9342(19) Å, RE = Nd: a = 21.7384(14) Å; RE = Sm: a = 21.6555(4) Å), were synthesized by dissolving the respective rare earth metals in a mercury surplus and subsequently distilling off the excess. The compounds were characterized by single crystal and powder X-ray methods together with ab-initio band structure calculations. Both crystal structures deviate significantly and in different ways from their common aristotype, the Sm11Cd45 structure type. In La11+xHg45-x (x = 0.7(1)) two crystallographic sites show mixed occupancy, whereas in RE11Hg44.5 one of the Hg positions is fully unoccupied. Their band structures exhibit typical broad Hg d states at low energies, and a strong mixing of s and p states indicates a mercury sublattice with high connectivity.

  1. Defect chemistry and characterization of Hg(1-x)Cd(x)Te

    NASA Technical Reports Server (NTRS)

    Vydyanath, H. R.

    1981-01-01

    Undoped mercury cadmium telluride crystals were subjected to high temperature equilibration at temperatures ranging from 400 C to 655 C in various Hg atmospheres. Hall effect and mobility measurements were carried out on the crystals quenched to room temperature subsequent to the high temperature equilibration. The variation of the hole concentration in the cooled crystals at 77 K as a function of the partial pressure of Hg at the equlibration temperatures, together with a comparison of the hole mobility in the undoped samples with that in the copper and phosphorous doped samples yielded a defect model for the undoped crystals, according to which, the undoped crystals are essentially intrinsic at the equilibration temperatures and the native acceptor defects are doubly ionized. Native donor defects appear to be negligible in concentration, implying that the p to n conversion in these alloys is mainly due to residual foreign donor impurities. The thermodynamic constants for the intrinsic excitation process as well as for the incorporation of the doubly ionized native acceptor defects in the undoped crystals were obtained.

  2. Defect chemistry and characterization of Hg(1-x)Cd(x)Te

    NASA Astrophysics Data System (ADS)

    Vydyanath, H. R.

    Undoped mercury cadmium telluride crystals were subjected to high temperature equilibration at temperatures ranging from 400 C to 655 C in various Hg atmospheres. Hall effect and mobility measurements were carried out on the crystals quenched to room temperature subsequent to the high temperature equilibration. The variation of the hole concentration in the cooled crystals at 77 K as a function of the partial pressure of Hg at the equlibration temperatures, together with a comparison of the hole mobility in the undoped samples with that in the copper and phosphorous doped samples yielded a defect model for the undoped crystals, according to which, the undoped crystals are essentially intrinsic at the equilibration temperatures and the native acceptor defects are doubly ionized. Native donor defects appear to be negligible in concentration, implying that the p to n conversion in these alloys is mainly due to residual foreign donor impurities. The thermodynamic constants for the intrinsic excitation process as well as for the incorporation of the doubly ionized native acceptor defects in the undoped crystals were obtained.

  3. Dielectric functions and carrier concentrations of Hg{sub 1−x}Cd{sub x}Se films determined by spectroscopic ellipsometry

    SciTech Connect

    Lee, A. J.; Peiris, F. C.; Brill, G.; Doyle, K.; Myers, T. H.

    2015-08-17

    Spectroscopic ellipsometry, ranging from 35 meV to 6 eV, was used to determine the dielectric functions of a series of molecular beam epitaxy-grown Hg{sub 1−x}Cd{sub x}Se thin films deposited on both ZnTe/Si(112) and GaSb(112) substrates. The fundamental band gap as well as two higher-order electronic transitions blue-shift with increasing Cd composition in Hg{sub 1−x}Cd{sub x}Se, as expected. Representing the free carrier absorption with a Drude oscillator, we found that the effective masses of Hg{sub 1−x}Cd{sub x}Se (grown on ZnTe/Si) vary between 0.028 and 0.050 times the free electron mass, calculated using the values of carrier concentration and the mobility obtained through Hall measurements. Using these effective masses, we determined the carrier concentrations of Hg{sub 1−x}Cd{sub x}Se samples grown on GaSb, which is of significance as films grown on such doped-substrates posit ambiguous results when measured by conventional Hall experiments. These models can serve as a basis for monitoring Cd-composition during sample growth through in-situ spectroscopic ellipsometry.

  4. Density of dislocations in CdHgTe heteroepitaxial structures on GaAs(013) and Si(013) substrates

    NASA Astrophysics Data System (ADS)

    Sidorov, Yu. G.; Yakushev, M. V.; Varavin, V. S.; Kolesnikov, A. V.; Trukhanov, E. M.; Sabinina, I. V.; Loshkarev, I. D.

    2015-11-01

    Epitaxial layers of Cd x Hg1- x Te (MCT) on GaAs(013) and Si(013) substrates were grown by molecular beam epitaxy. The introduction of ZnTe and CdTe intermediate layers into the structures made it possible to retain the orientation close to that of the substrate in MCT epitaxial layers despite the large mismatch between the lattice parameters. The structures were investigated using X-ray diffraction and transmission electron microscopy. The dislocation families predominantly removing the mismatch between the lattice parameters were found. Transmission electron microscopy revealed Γ-shaped misfit dislocations (MDs), which facilitated the annihilation of threading dislocations. The angles of rotation of the lattice due to the formation of networks of misfit dislocations were measured. It was shown that the density of threading dislocations in the active region of photodiodes is primarily determined by the network of misfit dislocations formed in the MCT/CdTe heterojunction. A decrease in the density of threading dislocations in the MCT film was achieved by cyclic annealing under conditions of the maximally facilitated nonconservative motion of dislocations. The dislocation density was determined from the etch pits.

  5. Preparation, characterization, and bacteriostasis of AgNP-coated β-CD grafting cellulose beads.

    PubMed

    Wang, Ting; Li, Bin; Lin, Li

    2013-03-01

    A novel functional material of β-cyclodextrin (β-CD) grafting cellulose beads containing immobilized silver nanoparticles (AgNPs) is presented in this paper. The morphology was characterized by scanning electron microscopy, energy-dispersive X-ray, and X-ray photoelectron spectroscopy. Phenolphthalein probe molecule technique was used to detect the activity of the grafting β-CD, and the results demonstrated that the deposition of AgNPs had no influence on its encapsulation ability. Acid resistance of the AgNPs on the bead material was studied by atomic absorption spectrometry. The stability of the AgNPs was enhanced due to the grafting of β-CD. Tube dilution method was applied to study the bacteriostatic effect, and the minimal inhibitory doses of the novel material against Escherichia coli and Staphylococcus aureus were 12.5 and 25 mg, respectively. The minimal bactericidal doses for the two bacteria were 25 and 25 mg, respectively. PMID:23340866

  6. Tunable Visible Emission of Ag-Doped CdZnS Alloy Quantum Dots

    PubMed Central

    2010-01-01

    Highly luminescent Ag-ion-doped Cd1−xZnxS (0 ≤ x ≤ 1) alloy nanocrystals were successfully synthesized by a novel wet chemical precipitation method. Influence of dopant concentration and the Zn/Cd stoichiometric variations in doped alloy nanocrystals have been investigated. The samples were characterized by X-ray diffraction (XRD) and high resolution transmission electron microscope (HRTEM) to investigate the size and structure of the as prepared nanocrystals. A shift in LO phonon modes from micro-Raman investigations and the elemental analysis from the energy dispersive X-ray analysis (EDAX) confirms the stoichiometry of the final product. The average crystallite size was found increasing from 1.0 to 1.4 nm with gradual increase in Ag doping. It was observed that photoluminescence (PL) intensity corresponding to Ag impurity (570 nm), relative to the other two bands 480 and 520 nm that originates due to native defects, enhanced and showed slight red shift with increasing silver doping. In addition, decrease in the band gap energy of the doped nanocrystals indicates that the introduction of dopant ion in the host material influence the particle size of the nanocrystals. The composition dependent bandgap engineering in CdZnS:Ag was achieved to attain the deliberate color tunability and demonstrated successfully, which are potentially important for white light generation. PMID:20652135

  7. Novel signal inversion of laser beam induced current for femtosecond-laser-drilling-induced junction on vacancy-doped p-type HgCdTe

    SciTech Connect

    Qiu, W. C.; Wang, R.; Xu, Z. J.; Jiang, T.; Cheng, X. A.

    2014-05-28

    In this paper, experimental results of temperature-dependent signal inversion of laser beam induced current (LBIC) for femtosecond-laser-drilling-induced junction on vacancy-doped p-type HgCdTe are reported. LBIC characterization shows that the traps induced by femtosecond laser drilling are sensitive to temperature. Theoretical models for trap-related p-n junction transformation are proposed and demonstrated using numerical simulations. The simulations are in good agreement with the experimental results. The effects of traps and mixed conduction are possibly the main reasons that result in the novel signal inversion of LBIC microscope at room temperature. The research results provide a theoretical guide for practical applications of large-scale array HgCdTe infrared photovoltaic detectors formed by femtosecond laser drilling, which may act as a potential new method for fabricating HgCdTe photodiodes.

  8. Structural, electronic, elastic, thermodynamic and phonon properties of LaX (X = Cd, Hg and Zn) compounds in the B2 phase

    NASA Astrophysics Data System (ADS)

    Örnek, Osman; Arıkan, Nihat

    2016-07-01

    The ab initio computations have been performed to examine the structural, elastic, electronic and phonon properties of cubic LaX (X = Cd, Hg and Zn) compounds in the B2 phase. The optimized lattice constants, bulk modulus, and its pressure derivative and elastic constants are evaluated and compared with available data. Electronic band structures and total and partial densities of states (DOS) have been derived for LaX (X = Cd, Hg and Zn) compounds. The electronic band structures show metallic character; the conductivity is mostly governed by La-5d states for three compounds. Phonon-dispersion curves have been obtained using the first-principle linear-response approach of the density-functional perturbation theory. The specific heat capacity at a constant volume CV of LaX (X = Cd, Hg and Zn) compounds are calculated and discussed.

  9. Improved performance of HgCdTe infrared detector focal plane arrays by modulating light field based on photonic crystal structure

    SciTech Connect

    Liang, Jian; Hu, Weida Ye, Zhenhua; Li, Zhifeng; Chen, Xiaoshuang Lu, Wei; Liao, Lei

    2014-05-14

    An HgCdTe long-wavelength infrared focal plane array photodetector is proposed by modulating light distributions based on the photonic crystal. It is shown that a promising prospect of improving performance is better light harvest and dark current limitation. To optimize the photon field distributions of the HgCdTe-based photonic crystal structure, a numerical method is built by combining the finite-element modeling and the finite-difference time-domain simulation. The optical and electrical characteristics of designed HgCdTe mid-wavelength and long-wavelength photon-trapping infrared detector focal plane arrays are obtained numerically. The results indicate that the photon crystal structure, which is entirely compatible with the large infrared focal plane arrays, can significantly reduce the dark current without degrading the quantum efficiency compared to the regular mesa or planar structure.

  10. The effect of metal-semiconductor contact on the transient photovoltaic characteristic of HgCdTe PV detector.

    PubMed

    Cui, Haoyang; Xu, Yongpeng; Yang, Junjie; Tang, Naiyun; Tang, Zhong

    2013-01-01

    The transient photovoltaic (PV) characteristic of HgCdTe PV array is studied using an ultrafast laser. The photoresponse shows an apparent negative valley first, then it evolves into a positive peak. By employing a combined theoretical model of pn junction and Schottky potential, this photo-response polarity changing curves can be interpreted well. An obvious decreasing of ratio of negative valley to positive peak can be realized by limiting the illumination area of the array electrode. This shows that the photoelectric effect of Schottky barrier at metal-semiconductor (M/S) interface is suppressed, which will verify the correctness of the model. The characteristic parameters of transient photo-response induced from p-n junction and Schottky potential are extracted by fitting the response curve utilizing this model. It shows that the negative PV response induced by the Schottky barrier decreases the positive photovoltage generated by the pn junction.

  11. Defect study in molecular beam epitaxy-grown HgCdTe films with activated and unactivated arsenic

    SciTech Connect

    Izhnin, I. I.; Dvoretsky, S. A.; Mikhailov, N. N.; Varavin, V. S.; Mynbaev, K. D.; Fitsych, O. I.; Pociask-Bialy, M.; Sheregii, E.; Voitsekhovskii, A. V.

    2014-04-28

    A defect study was performed on molecular beam epitaxy-grown HgCdTe films in situ doped with arsenic. Doping was performed from either effusion cell or cracker cell, and studied were both as-grown samples and samples subjected to arsenic activation annealing. Electrical properties of the films were investigated with the use of ion milling as a means of “stirring” defects in the material. As a result of the study, it was confirmed that the most efficient incorporation of electrically active arsenic occurs at the cracking zone temperature of 700 °C. Interaction between arsenic and tellurium during the growth was observed and is discussed in the paper.

  12. Large area space qualified thermoelectrically (TE) cooled HgCdTe MW photovoltaic detectors for the Halogen Occultation Experiment (HALOE)

    NASA Technical Reports Server (NTRS)

    Norton, P. W.; Zimmermann, P. H.; Briggs, R. J.; Hartle, N. M.

    1986-01-01

    Large-area, HgCdTe MW photovoltaic detectors have been developed for the NASA-HALOE instrument scheduled for operation on the Upper Atmospheric Research Satellite. The photodiodes will be TE-cooled and were designed to operate in the 5.1-5.4 micron band at 185 K to measure nitric oxide concentrations in the atmosphere. The active area required 15 micron thick devices and a full backside common contact. Reflections from the backside contact doubled the effective thickness of the detectors. Optical interference from reflections was eliminated with a dual layer front surface A/R coating. Bakeout reliability was optimized by having Au metallization for both n and p interconnects. Detailed performance data and a model for the optical stack are presented.

  13. Magneto-Hydrodynamic Damping of Convection During Vertical Bridgman-Stockbarger Growth of HgCdTe

    NASA Technical Reports Server (NTRS)

    Watring, D. A.; Lehoczky, S. L.

    1996-01-01

    In order to quantify the effects of convection on segregation, Hg(0.8)Cd(0.2)Te crystals were grown by the vertical Bridgman-Stockbarger method in the presence of an applied axial magnetic field of 50 kG. The influence of convection, by magneto-hydrodynamic damping, on mass transfer in the melt and segregation at the solid-liquid interface was investigated by measuring the axial and radial compositional variations in the grown samples. The reduction of convective mixing in the melt through the application of the magnetic field is found to decrease radial segregation to the diffusion-limited regime. It was also found that the suppression of the convective cell near the solid-liquid interface results in an increase in the slope of the diffusion-controlled solute boundary layer, which can lead to constitutional supercooling.

  14. Dynamic conductivity of the bulk states of n-type HgTe/CdTe quantum well topological insulator

    SciTech Connect

    Chen, Qinjun; Sanderson, Matthew; Cao, J. C.; Zhang, Chao

    2014-11-17

    We theoretically studied the frequency-dependent current response of the bulk state of topological insulator HgTe/CdTe quantum well. The optical conductivity is mainly due to the inter-band process at high frequencies. At low frequencies, intra-band process dominates with a dramatic drop to near zero before the inter-band contribution takes over. The conductivity decreases with temperature at low temperature and increases with temperature at high temperature. The transport scattering rate has an opposite frequency dependence in the low and high temperature regime. The different frequency dependence is due to the interplay of the carrier-impurity scattering and carrier population near the Fermi surface.

  15. Comparing FDTD and Ray-Tracing Models in Numerical Simulation of HgCdTe LWIR Photodetectors

    NASA Astrophysics Data System (ADS)

    Vallone, Marco; Goano, Michele; Bertazzi, Francesco; Ghione, Giovanni; Schirmacher, Wilhelm; Hanna, Stefan; Figgemeier, Heinrich

    2016-09-01

    We present a simulation study of HgCdTe-based long-wavelength infrared detectors, focusing on methodological comparisons between the finite-difference time-domain (FDTD) and ray-tracing optical models. We performed three-dimensional simulations to determine the absorbed photon density distributions and the corresponding photocurrent and quantum efficiency spectra of isolated n-on- p uniform-composition pixels, systematically comparing the results obtained with FDTD and ray tracing. Since ray tracing is a classical optics approach, unable to describe interference effects, its applicability has been found to be strongly wavelength dependent, especially when reflections from metallic layers are relevant. Interesting cavity effects around the material cutoff wavelength are described, and the cases where ray tracing can be considered a viable approximation are discussed.

  16. SEMICONDUCTOR TECHNOLOGY: Influence of hydrogenation on the dark current mechanism of HgCdTe photovoltaic detectors

    NASA Astrophysics Data System (ADS)

    Hui, Qiao; Weida, Hu; Zhenhua, Ye; Xiangyang, Li; Haimei, Gong

    2010-03-01

    The influence of hydrogenation on the dark current mechanism of HgCdTe photovoltaic detectors is studied. The hydrogenation is achieved by exposing samples to a H2/Ar plasma atmosphere that was produced during a reactive ion etching process. A set of variable-area photomask was specially designed to evaluate the hydrogenation effect. It was found that the current-voltage characteristics were gradually improved when detectors were hydrogenated by different areas. The fitting results of experimental results at reverse bias conditions sustained that the improvement of current-voltage curves was due to the suppression of trap assisted tunneling current and the enhancement of minority lifetime in the depletion region. It was also found that the dominative forward current was gradually converted from a generation-recombination current to a diffusion current with the enlargement of the hydrogenation area, which was infered from the ideality factors by abstraction of forward resistance-voltage curves of different detectors.

  17. HgCdTe mid-wavelength IR photovoltaic detectors fabricated using plasma induced junction technology

    NASA Astrophysics Data System (ADS)

    Dell, J. M.; Antoszewski, J.; Rais, M. H.; Musca, C.; White, J. K.; Nener, B. D.; Faraone, L.

    2000-06-01

    Preliminary characterization results are presented for mid-wave infrared (MWIR) mercury cadmium telluride n-on-p photodiodes fabricated using a plasma induced type conversion junction formation technology. The diodes have been fabricated on three different vacancy doped p-type epitaxial starting materials, grown by liquid phase epitaxy (LPE) on CdZnTe, LPE on sapphire, and P/p isotype heterojunction material grown by molecular beam epitaxy (MBE) on CdZnTe. All materials had CdTe mole fraction in the active region of the device of ˜0.3. The process uses a H2/CH4 plasma generated in a parallel plate reactive ion etching (RIE) system to type convert the p-type material to n-type. The process is different from previously reported type conversion techniques in that it does not require a high temperature anneal, does not expose the junction at the surface to atmosphere after formation, and requires significantly fewer process steps than other planar processes. Homojunction devices fabricated using this process exhibit R0A values >107 Ω·cm2 at 80 K. The R0A is diffusion limited for temperatures >˜135 K. Results for responsivity, bias dependence of dynamic resistance — junction area product and 1/f noise show that the resulting diodes are comparable to the best planar diodes reported in the literature.

  18. Effect of Pb, Cd, Hg, As, and Cr on germination and root growth of Sinapis alba seeds

    SciTech Connect

    Fargasova, A. )

    1994-03-01

    Heavy metals have been widely recognized as highly toxic and dangerous. Plants, algae and bacteria respond to heavy metal toxicity by inducing different enzymes, creating ion influx/efflux for ionic balance and synthesizing small peptides. These peptides bind metal ions and reduce toxicity. Metals come from the natural weathering processes of the earth's crust, industrial discharge, pest or disease control agents applied to plants, urban run-off, mining, soil erosion, sewage effluents, air pollution fallout and other sources. Plants can be affected directly by air pollutants, as well as indirectly through the contamination of soil and water. At the same time, plant is a member of the food chain and may create a risk for man and animals through contamination of food supplies. In recent years a considerable progress has been made in the assay of trace elements in environmental plant samples. For higher plants, the accumulation of metals, especially cadmium, was tested when plants grew on sewage sludge-amended soils or in soils of cadmium residues from phosphate fertilizers. No reports were accessible to us on the direct effect of tested metals (Pb, Hg, Cr, As, Cd) on seed germination and root growth. The paucity of literature initiated our present work. In this study, an attempt has been made to investigate the acute toxicity of five metals (Cr[sup 6+], Cd[sup 2+], Hg[sup 2+], Pb[sup 2+], As[sup 5+]) which are widely spread in the environment and are widely recognized as highly toxic and dangerous. As the testing subject, mustard seeds (Sinapis alba) were used and their germination and root growth were observed. 12 refs., 1 tab.

  19. ZnO/Ag/CdO nanocomposite for visible light-induced photocatalytic degradation of industrial textile effluents.

    PubMed

    Saravanan, R; Mansoob Khan, M; Gupta, Vinod Kumar; Mosquera, E; Gracia, F; Narayanan, V; Stephen, A

    2015-08-15

    A ternary ZnO/Ag/CdO nanocomposite was synthesized using thermal decomposition method. The resulting nanocomposite was characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, UV-Vis spectroscopy, and X-ray photoelectron spectroscopy. The ZnO/Ag/CdO nanocomposite exhibited enhanced photocatalytic activity under visible light irradiation for the degradation of methyl orange and methylene blue compared with binary ZnO/Ag and ZnO/CdO nanocomposites. The ZnO/Ag/CdO nanocomposite was also used for the degradation of the industrial textile effluent (real sample analysis) and degraded more than 90% in 210 min under visible light irradiation. The small size, high surface area and synergistic effect in the ZnO/Ag/CdO nanocomposite is responsible for high photocatalytic activity. These results also showed that the Ag nanoparticles induced visible light activity and facilitated efficient charge separation in the ZnO/Ag/CdO nanocomposite, thereby improving the photocatalytic performance.

  20. Correlation Between Bands Structure and Magneto-Transport Properties in n-type HgTe/CdTe Superlattice with Relatively Thin CdTe Barrier

    SciTech Connect

    Braigue, M.; Nafidi, A.; Chaib, H.; Tirbiyine, A.; Hemine, J.; Idbaha, A.; Boulkassim, A.; El Gouti, T.; Massaq, M.; Talwar, Devki N.; SrinivasaVinod, M.

    2011-12-26

    Theoretical calculations of the electronic properties of n-type HgTe/CdTe superlattices (SLs) in the envelope function formalism have provided a reasonable agreement with the experimental data on the magneto-transport behavior. Numerical results of the band energies E(d{sub 2}), E(k{sub z}) and E(k{sub p}) in the direction of growth and in plane of the SLs predict that the system retains semiconductor characteristics for d{sub 1}/d{sub 2} = 2.69 and d{sub 2}<10 nm. For d{sub 2} = 3.2 nm the calculated effective band gap (E{sub g}({Gamma},4.2 K) = 48 meV) suggests that the material sample is a two-dimensional modulated nanostructure and a potential candidate to be used for the far infrared detection applications.

  1. Reduction of Ag{sup I}, Au{sup III}, Cu{sup II}, and Hg{sup II} by Fe{sup II}/Fe{sup III} hydroxysulfate green rust.

    SciTech Connect

    O'Loughlin, E. J.; Kelly, S. D.; Kemner, K. M.; Csencsits, R.; Cook, R. E.

    2003-11-01

    Green rusts are mixed Fe{sup II}/Fe{sup III} hydroxides that are found in many suboxic environments where they are believed to play a central role in the biogeochemical cycling of iron. X-ray absorption fine structure analysis of hydroxysulfate green rust suspensions spiked with aqueous solutions of AgCH{sub 3}COO, AuCl{sub n}(OH){sub 4-n}, CuCl{sub 2}, or HgCl{sub 2} showed that Ag{sup I}, Au{sup III}, Cu{sup II}, and Hg{sup II} were readily reduced to Ag{sup 0}, Au{sup 0}, Cu{sup 0}, and Hg{sup 0}. Imaging of the resulting solids from the Ag{sup I}-, Au{sup III}-, and Cu{sup II}-amended green rust suspensions by transmission electron microscopy indicated the formation of submicron-sized particles of Ag{sup 0}, Au{sup 0}, and Cu{sup 0}. The facile reduction of Ag{sup I}, Au{sup III}, Cu{sup II}, and Hg{sup II} to Ag{sup 0}, Au{sup 0}, Cu{sup 0}, and Hg{sup 0}, respectively, by green rust suggests that the presence of green rusts in suboxic soils and sediments can have a significant impact on the biogeochemistry of silver, gold, copper, and mercury, particularly with respect to their mobility.

  2. Formation mechanism and properties of CdS-Ag2S nanorod superlattices

    SciTech Connect

    Wang, Lin-Wang; Demchenko, Denis O.; Robinson, Richard D.; Sadtler, Bryce; Erdonmez, Can K.; Alivisatos, A. Paul; Wang, Lin-Wang

    2008-08-11

    The mechanism of formation of recently fabricated CdS-Ag{sub 2}S nanorod superlattices is considered and their elastic properties are predicted theoretically based on experimental structural data. We consider different possible mechanisms for the spontaneous ordering observed in these 1D nanostructures, such as diffusion-limited growth and ordering due to epitaxial strain. A simplified model suggests that diffusion-limited growth partially contributes to the observed ordering, but cannot account for the full extent of the ordering alone. The elastic properties of bulk Ag{sub 2}S are predicted using a first principles method and are fed into a classical valence force field (VFF) model of the nanostructure. The VFF results show significant repulsion between Ag{sub 2}S segments, strongly suggesting that the interplay between the chemical interface energy and strain due to the lattice mismatch between the two materials drives the spontaneous pattern formation.

  3. Concentration of Cd, Pb, Hg, and Se in Different Parts of Human Breast Cancer Tissues

    PubMed Central

    Mohammadi, Mehrnoosh; Riyahi Bakhtiari, Alireza; Khodabandeh, Saber

    2014-01-01

    Breast cancer is the major cause of cancer morbidity and mortality between women in the world. Metals involved in environmental toxicology are closely related to tumor growth and cancer. On the other hand, some metals such as selenium have anticarcinogenic properties. The aim of this study is to determine the concentration of cadmium, lead, mercury, and selenium in separated parts of tegmen, tumor, tumor adiposity, and tegmen adiposity of 14 breast cancer tissues which have been analyzed by graphite furnace atomic absorption (AA-670) and ICP-OES (ULTIMA 2CE). Our results show that Se and Hg have maximum and minimum concentration, respectively. Statistical analysis reveals no significant differences between metal accumulations in different parts of cancer tissues (P > 0.05) and this observation might be due to the close relation of separated parts of fatty breast organ. Thus, we could conclude that a high level of these heavy metals is accumulated in Iranian cancerous breasts and their presence can be one of the reasons of cancer appearance. PMID:24659998

  4. Numerical Simulation of Refractive-Microlensed HgCdTe Infrared Focal Plane Arrays Operating in Optical Systems

    NASA Astrophysics Data System (ADS)

    Li, Yang; Ye, Zhen-Hua; Hu, Wei-Da; Lei, Wen; Gao, Yan-Lin; He, Kai; Hua, Hua; Zhang, Peng; Chen, Yi-Yu; Lin, Chun; Hu, Xiao-Ning; Ding, Rui-Jun; He, Li

    2014-08-01

    The optoelectronic performance of the mid-wavelength HgCdTe infrared focal plane array (IRFPA) with refractive microlenses integrated on its CdZnTe substrate has been numerically simulated. A reduced light-distribution model based on scalar Kirchhoff diffraction theory was adopted to reveal the true behavior of IRFPAs operating in an optical system under imaging conditions. The pixel crosstalk obtained and the energy-gathering characteristics demonstrated that the microlenses can delay the rise in crosstalk when the image point shifts toward pixel boundaries, and can restrict the major optical absorption process in any case within a narrow region around the pixel center. The dependence of the microlenses' effects on the system's properties was also analyzed; this showed that intermediate relative aperture and small microlens radius are required for optimized device performance. Simulation results also indicated that for detectors farther from the center of the field of view, the efficacy of microlenses in crosstalk suppression and energy gathering is still maintained, except for a negligible difference in the lateral magnification from an ordinary array without microlenses.

  5. Research and development of HgZnTe as an infrared material

    NASA Technical Reports Server (NTRS)

    Wahi, A. K.; Lindau, I.; Spicer, W. E.

    1989-01-01

    Interfacial morphology and Fermi level pinning behavior at the interfaces of Al, Ag, and Pt with UHV-cleaved CdTe and ZnTe have been studied using X-ray and ultraviolet photoemission spectroscopies. Results are compared to metal/HgCdTe interface formation, where the weak HgTe bond and consequent ease of Hg loss strongly influence semiconductor disruption and metal-semiconductor intermising. For Al/CdTe, the strong Al-Te reaction yields a significantly more extensive Al-Te reacted region than has been observed for HgCdTe. The Al/ZnTe interface is observed to be more abrupt than Al/CdTe. The final Fermi level pinning positions, Ef-Evbm for Al, Ag, and Pt on p-type CdTe and p-ZnTe have been determined. Efi is found to be roughly the same for both CdTe and ZnTe, with the value for ZnTe lying approximately 0.2 eV closer to the VBM for all three metals. From these results, one would expect Schottky barriers of about the same height for these metals on p-CdTe and p-ZnTe; and also that, in principle, metal interfaces with the two alloys HgCdTe and HgZnTe would have the same properties. Comparisons and implications for electrical behavior of metal contacts to the alloys are discussed.

  6. The visible light photocatalytic activity enhancement of cotton cellulose nanofibers/In2S3/Ag-CdS nanocomposites

    NASA Astrophysics Data System (ADS)

    Pan, Jiaqi; Li, Jing; Zhang, Xiufang; Zheng, Yingying; Cui, Can; Zhu, Zhiyan; Li, Chaorong

    2016-07-01

    Cotton cellulose nanofibers (CCNFs)/In2S3/Ag-CdS nanocomposites were prepared by a typical technical route which combined electrospinning and a chemical method. The results showed that the CCNFs/In2S3/Ag-CdS nanocomposites had a remarkable visible light photocatalytic property and cycling stability, which displayed a significant enhancement compared with that of pure In2S3. Through analysis, this enhancement could be mainly attributed to the multilevel structure of the composites.

  7. Folic acid functionalized silver nanoparticles with sensitivity and selectivity colorimetric and fluorescent detection for Hg2+ and efficient catalysis

    NASA Astrophysics Data System (ADS)

    Su, Dongyue; Yang, Xin; Xia, Qingdong; Zhang, Qi; Chai, Fang; Wang, Chungang; Qu, Fengyu

    2014-09-01

    In this research, folic acid functionalized silver nanoparticles (FA-AgNPs) were selected as a colorimetric and a ‘turn on’ fluorescent sensor for detecting Hg2+. After being added into Hg2+, AgNPs can emit stable fluorescence at 440 nm when the excitation wavelength is selected at 275 nm. The absorbance and fluorescence of the FA-AgNPs could reflect the concentration of the Hg2+ ions. Thus, we developed a simple, sensitive analytical method to detect Hg2+ based on the colorimetric and fluorescence enhancement of FA-AgNPs. The sensor exhibits two linear response ranges between absorbance and fluorescence intensity with Hg2+ concentration, respectively. Meanwhile, a detection limit of 1 nM is estimated based on the linear relationship between responses with a concentration of Hg2+. The high specificity of Hg2+ with FA-AgNPs interactions provided the excellent selectivity towards detecting Hg2+ over other metal ions (Pb2+, Mg2+, Zn2+, Ni2+, Cu2+, Co2+, Ca2+, Mn2+, Fe2+, Cd2+, Ba2+, Cr6+ and Cr3+). This will provide a simple, effective and multifunctional colorimetric and fluorescent sensor for on-site and real-time Hg2+ ion detection. The proposed method can be applied to the analysis of trace Hg2+ in lake water. Additionally, the FA-AgNPs can be used as efficient catalyst for the reduction of 4-nitrophenol and potassium hexacyanoferrate (III).

  8. [Si(SiMe3)3]6Ge18M (M = Zn, Cd, Hg): neutral metalloid cluster compounds of germanium as highly soluble building blocks for supramolecular chemistry.

    PubMed

    Henke, Florian; Schenk, Christian; Schnepf, Andreas

    2009-11-14

    Very recently it was shown that the metalloid cluster compound {Ge(9)[Si(SiMe(3))(3)](3)}(-) can be used for subsequent reactions as the shielding of the cluster core is rather incomplete. So the reaction of with M(+) sources of group 11 metals gives metalloid cluster compounds of the formulae {MGe(18)[Si(SiMe(3))(3)](6)}(-) (M = Au, Ag, Cu). These reactions can be seen as first steps into a supramolecular chemistry with metalloid cluster compounds. However, further build-up reactions lead to insoluble products, thus better soluble starting materials are needed for further build-up reactions. Here the first neutral MGe(18)[Si(SiMe(3))(3)](6) (M = Hg, Cd, Zn) compounds are described, exhibiting a strongly enhanced solubility in inert solvents. Beside the synthesis, the structural properties as well as the bonding situations in these cluster compounds are discussed. PMID:20449189

  9. The future of large format HgCdTe arrays for astronomy

    NASA Technical Reports Server (NTRS)

    Vural, K.

    1994-01-01

    Rockwell has developed the 256 x 256 Near Infrared Camera and Multi-Object Spectrometer 3 (NICMOS3) FPA for the Hubble Space Telescope under funding from NASA through the University of Arizona. Since 1989, dozens of science grade devices have been delivered to astronomers throughout the world for ground based infrared observations. These devices have excellent sensitivity at 77 K with mean dark currents of 0.1 e(-)/s, noise of 25 e(-), and quantum efficiency of 55-70%. Pixel yields as high as 99.9% have been achieved. Our present plans are to develop a 1024 x 1024 focal plane array (FPA) with 2.5 micron cutoff and make it available to astronomers. Such large arrays are made possible by the advances in detector material size (3 in. diameter producible alternative to CdTe for epitaxy (PACE-I) wafers), multiplexer advances (ability to verify the design in detail and availability of advanced foundries), and novel hybridization and reliability approaches.

  10. The future of large format HgCdTe arrays for astronomy

    NASA Astrophysics Data System (ADS)

    Vural, K.

    1994-03-01

    Rockwell has developed the 256 x 256 Near Infrared Camera and Multi-Object Spectrometer 3 (NICMOS3) FPA for the Hubble Space Telescope under funding from NASA through the University of Arizona. Since 1989, dozens of science grade devices have been delivered to astronomers throughout the world for ground based infrared observations. These devices have excellent sensitivity at 77 K with mean dark currents of 0.1 e(-)/s, noise of 25 e(-), and quantum efficiency of 55-70%. Pixel yields as high as 99.9% have been achieved. Our present plans are to develop a 1024 x 1024 focal plane array (FPA) with 2.5 micron cutoff and make it available to astronomers. Such large arrays are made possible by the advances in detector material size (3 in. diameter producible alternative to CdTe for epitaxy (PACE-I) wafers), multiplexer advances (ability to verify the design in detail and availability of advanced foundries), and novel hybridization and reliability approaches.

  11. Slurry sampling flow injection chemical vapor generation inductively coupled plasma mass spectrometry for the determination of trace Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions.

    PubMed

    Chen, Wei-Ni; Jiang, Shiuh-Jen; Chen, Yen-Ling; Sahayam, A C

    2015-02-20

    A slurry sampling inductively coupled plasma mass spectrometry (ICP-MS) method has been developed for the determination of Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions using flow injection (FI) vapor generation (VG) as the sample introduction system. A slurry containing 2% m/v lotion, 2% m/v thiourea, 0.05% m/v L-cysteine, 0.5 μg mL(-1) Co(II), 0.1% m/v Triton X-100 and 1.2% v/v HCl was injected into a VG-ICP-MS system for the determination of Ge, As, Cd, Sb, Hg and Bi without dissolution and mineralization. Because the sensitivities of the analytes in the slurry and that of aqueous solution were quite different, an isotope dilution method and a standard addition method were used for the determination. This method has been validated by the determination of Ge, As, Cd, Sb, Hg and Bi in GBW09305 Cosmetic (Cream) reference material. The method was also applied for the determination of Ge, As, Cd, Sb, Hg and Bi in three cosmetic lotion samples obtained locally. The analysis results of the reference material agreed with the certified value and/or ETV-ICP-MS results. The detection limit estimated from the standard addition curve was 0.025, 0.1, 0.2, 0.1, 0.15, and 0.03 ng g(-1) for Ge, As, Cd, Sb, Hg and Bi, respectively, in original cosmetic lotion sample.

  12. [Concentration of Hg, Pb, Cd, Cr and As in liver Carcharhinus limbatus (Carcharhiniformes: Carcharhinidae) captured in Veracruz, Mexico].

    PubMed

    Mendoza-Díaz, Fernando; Serrano, Arturo; Cuervo-López, Liliana; López-Jiménez, Alejandra; Galindo, José A; Basañez-Muñoz, Agustin

    2013-06-01

    Pollution by heavy metals in marine ecosystems in the Gulf of Mexico is one of the hardest conservation issues to solve. Sharks as top predators are bioindicators of the marine ecosystem health, since they tend to bioaccumulate and biomagnify contaminants; they also represent a food source for local consumption. Thus, the objective of this study was to study the possible presence of heavy metals and a metalloid in livers of Carcharhinus limbatus. For this, a total of 19 shark livers were taken from animals captured nearby Tamihua, Veracruz, Mexico from December 2007 to April 2008. 12 out of the 19 captured sharks were males, one was an adult female, three were juvenile males, and three juvenile females. Four heavy metals (Hg, Pb, Cd, and Cr) and one metaloid (As) were analyzed in shark livers using an atomic absorption spectrophotometry with flame and hydride generator. Our results showed that the maximum concentrations found were: Hg = 0.69 mg/kg, Cd = 0.43 mg/kg, As = 27.37 mg/kg, Cr = 0.70 mg/kg. The minimum concentrations found were: As = 14.91 mg/kg, Cr = 0.35 mg/kg. The Pb could not be determined because the samples did not have the spectrophotometer minimum detectable amount (0.1 mg/kg). None of the 19 samples analyzed showed above the permissible limits established by Mexican and American laws. There was a correlation between shark size and Cr and As concentration (Pearson test). The concentration of Cr and As was observed to be higher in bigger animals. There was not a significant difference in heavy metals concentration between juveniles and adults; however, there was a difference between males and females. A higher Cr concentration was found in females when compared to males. None of the samples exceed the maximum limit established by the laws of Mexico and the United States of America. Much longer studies are needed with C. limbatus and other species caught in the region, in order to determine the degree of contaminants exposure in aquatic ecosystems

  13. Defects in the crystal structure of Cd{sub x}Hg{sub 1-x}Te layers grown on the Si (310) substrates

    SciTech Connect

    Yakushev, M. V. Gutakovsky, A. K.; Sabinina, I. V.; Sidorov, Yu. G.

    2011-07-15

    Microstructure of the CdTe (310) and CdHgTe (310) layers grown by molecular-beam epitaxy on Si substrates has been studied by the methods of transmission electron microscopy and selective etching. It is established that formation of antiphase domains in the CdHgTe/CdTe/ZnTe/Si(310) is determined by the conditions of formation of the ZnTe/Si interface. Monodomain layers can be obtained by providing conditions that enhance zinc adsorption. An increase in the growth temperature and in the pressure of Te{sub 2} vapors gives rise to antiphase domains and induces an increase in their density to the extent of the growth of poly-crystals. It is found that stacking faults exist in a CdHgTe/Si(310) heterostructure; these defects are anisotropically distributed in the bulk of grown layers. The stacking faults are predominantly located in one (111) plane, which intersects the (310) surface at an angle of 68 Degree-Sign . The stacking faults originate at the ZnTe/Si(310) interface. The causes of origination of stacking faults and of their anisotropic distribution are discussed.

  14. Approaching the N=82 shell closure with mass measurements of Ag and Cd isotopes

    SciTech Connect

    Breitenfeldt, M.; Baruah, S.; Rosenbusch, M.; Schweikhard, L.; Borgmann, Ch.; Boehm, Ch.; George, S.; Audi, G.; Lunney, D.; Minaya-Ramirez, E.; Naimi, S.; Beck, D.; Dworschak, M.; Herfurth, F.; Savreux, R.; Yazidjian, C.; Blaum, K.; Cakirli, R. B.; Casten, R. F.; Delahaye, P.

    2010-03-15

    Mass measurements of neutron-rich Cd and Ag isotopes were performed with the Penning trap mass spectrometer ISOLTRAP. The masses of {sup 112,114-124}Ag and {sup 114,120,122-124,126,128}Cd, determined with relative uncertainties between 2x10{sup -8} and 2x10{sup -7}, resulted in significant corrections and improvements of the mass surface. In particular, the mass of {sup 124}Ag was previously unknown. In addition, other masses that had to be inferred from Q values of nuclear decays and reactions have now been measured directly. The analysis includes various mass differences, namely the two-neutron separation energies, the applicability of the Garvey-Kelson relations, double differences of masses deltaV{sub pn}, which give empirical proton-neutron interaction strengths, as well as a comparison with recent microscopic calculations. The deltaV{sub pn} results reveal that for even-even nuclides around {sup 132}Sn the trends are similar to those in the {sup 208}Pb region.

  15. Effects of Gravity on the Double-Diffusive Convection during Directional Solidification of a Non-Dilute Alloy with Application to the HgCdTe

    NASA Technical Reports Server (NTRS)

    Bune, Andris; Gillies, Donald; Lehoczky, Sandor

    1999-01-01

    General 2-D and 3-D finite element model of non-dilute alloy solidification was used to simulate growth of HgCdTe in terrestrial and microgravity conditions. Parametric research was undertaken to investigate effects of gravity level, gravity vector orientation and growth velocity on the pattern of melt convection, shape of crystal/melt interface and radial thermal gradient. Verification of the model was undertaken by comparison with previously published results. For low growth velocities plane front solidification occurs. The location and the shape of the interface was determined using melting temperatures obtained from the HgCdTe liquidus curve. The low thermal conductivity of the solid HgCdTe causes thermal short circuit through the ampoule walls, resulting in curved isotherms in the vicinity of the interface. Double-diffusive convection in the melt is caused by radial temperature gradients and by material density inversion with temperature. Cooling from below and the rejection at the solid-melt interface of the heavier HgTe-rich solute each tend to reduce convection. Because of these complicating factors dimensional rather then non-dimensional modeling was performed. For gravity levels higher then 10(exp -7) of terrestrial one it was found that the maximum convection velocity is extremely sensitive to gravity vector orientation and can be reduced at least by 50% by choosing proper orientation of the ampoule. The predicted interface shape is in agreement with one obtained experimentally by quenching.

  16. Effects of Gravity on the Double-Diffusive Convection During Directional Solidification of a Non-Dilute Alloy with Application to HgCdTe

    NASA Technical Reports Server (NTRS)

    Bune, Andris V.; Gillies, Donald C.; Lehoczky, Sandor L.

    1999-01-01

    A general 2-D and 3-D finite element model of non-dilute alloy solidification was used to simulate growth of HgCdTe in terrestrial and microgravity conditions. Verification of the 3-D model was undertaken by comparison with previously published results on convection in an inclined cylinder. For low growth velocities, plane front solidification occurs. The location and the shape of the interface were determined using melting temperatures obtained from the HgCdTe liquidus curve. The low thermal conductivity of the solid HgCdTe causes a thermal short circuit through the ampoule walls, resulting in curved isotherms in the vicinity of the interface. Double-diffusive convection in the melt is caused by radial temperature gradients and by material density inversion due to the combined effects of composition and temperature. Cooling from below and the rejection at the solid-melt interface of the heavier HgTe-rich solute each tend to reduce convection. Because of these complicating factors, dimensional rather than non-dimensional modeling was performed. the predicted interface shape is in agreement with one obtained experimentally by quenching.

  17. Seasonal survey of contaminants (Cd and Hg) and micronutrients (Cu and Zn) in edible tissues of cephalopods from Tunisia: assessment of risk and nutritional benefits.

    PubMed

    Rjeibi, Moncef; Metian, Marc; Hajji, Tarek; Guyot, Thierry; Ben Chaouacha-Chekir, Rafika; Bustamante, Paco

    2015-01-01

    Concentrations of cadmium (Cd), copper (Cu), mercury (Hg), and zinc (Zn) were determined by atomic absorption spectrophotometry in the muscle tissues (arms and mantle) of 3 commercial cephalopods (Loligo vulgaris, Octopus vulgaris, and Sepia officinalis) caught in 3 different Tunisian coastal regions. The highest concentrations found correspond to the essential elements Cu and Zn. Octopuses and cuttlefish showed the highest levels of those elements whereas squid presented with significantly higher values of Hg in both muscular tissues. This may be related to different feeding behavior and detoxification processes among benthic and pelagic cephalopods. Variation of element concentrations between seasons was different between species and seemed to be mostly dependent on the sampling site. From a public health standpoint, average concentrations of Cd, Cu, Hg, and Zn measured in edible tissues of cephalopods from this study did not reveal, in general, any risk for consumers. The estimated target hazard quotients for Cd and Hg for consumers of the selected species were below 1 and within the safety range for human health. Moreover, their consumption could provide in an important contribution to the daily dietary intake of Cu for the Tunisian population, especially regarding the consumption of octopus and cuttlefish muscles. PMID:25427969

  18. Seasonal survey of contaminants (Cd and Hg) and micronutrients (Cu and Zn) in edible tissues of cephalopods from Tunisia: assessment of risk and nutritional benefits.

    PubMed

    Rjeibi, Moncef; Metian, Marc; Hajji, Tarek; Guyot, Thierry; Ben Chaouacha-Chekir, Rafika; Bustamante, Paco

    2015-01-01

    Concentrations of cadmium (Cd), copper (Cu), mercury (Hg), and zinc (Zn) were determined by atomic absorption spectrophotometry in the muscle tissues (arms and mantle) of 3 commercial cephalopods (Loligo vulgaris, Octopus vulgaris, and Sepia officinalis) caught in 3 different Tunisian coastal regions. The highest concentrations found correspond to the essential elements Cu and Zn. Octopuses and cuttlefish showed the highest levels of those elements whereas squid presented with significantly higher values of Hg in both muscular tissues. This may be related to different feeding behavior and detoxification processes among benthic and pelagic cephalopods. Variation of element concentrations between seasons was different between species and seemed to be mostly dependent on the sampling site. From a public health standpoint, average concentrations of Cd, Cu, Hg, and Zn measured in edible tissues of cephalopods from this study did not reveal, in general, any risk for consumers. The estimated target hazard quotients for Cd and Hg for consumers of the selected species were below 1 and within the safety range for human health. Moreover, their consumption could provide in an important contribution to the daily dietary intake of Cu for the Tunisian population, especially regarding the consumption of octopus and cuttlefish muscles.

  19. Decorating CdTe QD-Embedded Mesoporous Silica Nanospheres with Ag NPs to Prevent Bacteria Invasion for Enhanced Anticounterfeit Applications.

    PubMed

    Gao, Yangyang; Dong, Qigeqi; Lan, Shi; Cai, Qian; Simalou, Oudjaniyobi; Zhang, Shiqi; Gao, Ge; Chokto, Harnoode; Dong, Alideertu

    2015-05-13

    Quantum dots (QDs) as potent candidates possess advantageous superiority in fluorescence imaging applications, but they are susceptible to the biological circumstances (e.g., bacterial environment), leading to fluorescence quenching or lose of fluorescent properties. In this work, CdTe QDs were embedded into mesoporous silica nanospheres (m-SiO2 NSs) for preventing QD agglomeration, and then CdTe QD-embedded m-SiO2 NSs (m-SiO2/CdTe NSs) were modified with Ag nanoparticles (Ag NPs) to prevent bacteria invasion for enhanced anticounterfeit applications. The m-SiO2 NSs, which serve as intermediate layers to combine CdTe QDs with Ag NPs, help us establish a highly fluorescent and long-term antibacterial system (i.e., m-SiO2/CdTe/Ag NSs). More importantly, CdTe QD-embedded m-SiO2 NSs showed fluorescence quenching when they encounter bacteria, which was avoided by attaching Ag NPs outside. Ag NPs are superior to CdTe QDs for preventing bacteria invasion because of the structure (well-dispersed Ag NPs), size (small diameter), and surface charge (positive zeta potentials) of Ag NPs. The plausible antibacterial mechanisms of m-SiO2/CdTe/Ag NSs toward both Gram-positive and Gram-negative bacteria were established. As for potential applications, m-SiO2/CdTe/Ag NSs were developed as fluorescent anticounterfeiting ink for enhanced imaging applications.

  20. TEQUILA: NIR camera/spectrograph based on a Rockwell 1024x1024 HgCdTe FPA

    NASA Astrophysics Data System (ADS)

    Ruiz, Elfego; Sohn, Erika; Cruz-Gonzales, Irene; Salas, Luis; Parraga, Antonio; Perez, Manuel; Torres, Roberto; Cobos Duenas, Francisco J.; Gonzalez, Gaston; Langarica, Rosalia; Tejada, Carlos; Sanchez, Beatriz; Iriarte, Arturo; Valdez, J.; Gutierrez, Leonel; Lazo, Francisco; Angeles, Fernando

    1998-08-01

    We describe the configuration and operation modes of the IR camera/spectrograph: TEQUILA based on a 1024 X 1024 HgCdTe FPA. The optical system will allow three possible modes of operation: direct imaging, low and medium resolution spectroscopy and polarimetry. The basic system is being designed to consist of the following: 1) A LN(subscript 2) dewar that allocates the FPA together with the preamplifiers and a 24 filter position cylinder. 2) Control and readout electronics based on DSP modules linked to a workstation through fiber optics. 3) An opto-mechanical assembly cooled to -30 degrees that provides an efficient operation of the instrument in its various modes. 4) A control module for the moving parts of the instrument. The opto-mechanical assembly will have the necessary provision to install a scanning Fabry-Perot interferometer and an adaptive optics correction system. The final image acquisition and control of the whole instrument is carried out in a workstation to provide the observer with a friendly environment. The system will operate at the 2.1 m telescope at the Observatorio Astronomico Nacional in San Pedro Martir, B.C. (Mexico), and is intended to be a first-light instrument for the new 7.8m Mexican IR-Optical Telescope.

  1. RMS noise modeling and detection for high-reliability HgCdTe infrared focal plane arrays development

    NASA Astrophysics Data System (ADS)

    Cathignol, A.; Vauquelin, G.; Brunner, A.; Destefanis, V.; Rubaldo, L.; Maillard, M.; Runtz, M.

    2015-06-01

    This paper presents recent improvements introduced in production lines of Mid-Wavelength Infra-Red (MWIR) and Long-Wavelength Infra-Red (LWIR) HgCdTe detectors that increase performances, image quality, and reliability. This was achieved thanks to accurate characterization of RMS noise distributions. Based on many MWIR and LWIR devices RMS distributions, a RMS noise distribution model that accounts for both Background Limited diodes and 1/f noise affected isolated diodes is first proposed. Then, a figure of merit for quantifying the defective pixels is introduced. This figure of merit is shown to be easy to use and robust to statistical variability. Moreover, it does also very well correlate with physics : there is high correlation between the total number of calculated defects and other figures of merit that gauge the material quality or the low frequency noise. The ability to accurately and efficiently quantify RMS noise benefits to Sofradir in its development of highly reliable and performant technologies. Such benefits are illustrated on the latest Sofradir MWIR and LWIR technologies that are demonstrated to be very robust regarding thermal stress and thermal cycling. Finally those technologies are shown to reach high image quality and stability.

  2. First principles study of structural, electronic, elastic and thermal properties of YX (X = Cd, In, Au, Hg and Tl) intermetallics

    NASA Astrophysics Data System (ADS)

    Chouhan, Sunil Singh; Pagare, Gitanjali; Rajagopalan, M.; Sanyal, S. P.

    2012-08-01

    The structural, electronic, elastic and thermal properties of YX (X = Cd, In, Au, Hg and Tl) intermetallic compounds crystallizing in B2-type structure have been studied using first principles density functional theory within generalized gradient approximation (GGA) for the exchange correlation potential. Amongst all the YX compounds, YIn is stable in distorted tetragonal (P4/mmm) CuAu-type structure at ambient pressure with very small energy difference of 0.00681 Ry. but it undergoes to CsCl-type (B2 phase) structure at 23.3 GPa. Rest of the compounds are stable in B2 structure at ambient condition. The values of elastic moduli as a function of pressure are also reported. The ductility of these compounds has been analyzed using the Pugh rule. Our calculated results indicate that YTl is the most ductile amongst all the B2-YX compounds. YAu is the hardest and less compressible compound due to the largest bulk modulus. The elastic properties such as Young's modulus (E), Poisson's ratio (σ) and anisotropic ratio (A) are also predicted. The anisotropic factor is found to be unity for YHg which shows that this compound is isotropic.

  3. The quantum efficiency of HgCdTe photodiodes in relation to the direction of illumination and to their geometry

    NASA Technical Reports Server (NTRS)

    Rosenfeld, D.; Bahir, G.

    1993-01-01

    A theoretical study of the effect of the direction of the incident light on the quantum efficiency of homogeneous HgCdTe photodiodes suitable for sensing infrared radiation in the 8-12 microns atmospheric window is presented. The probability of an excess minority carrier to reach the junction is derived as a function of its distance from the edge of the depletion region. Accordingly, the quantum efficiency of photodiodes is presented for two geometries. In the first, the light is introduced directly to the area in which it is absorbed (opaque region), while in the second, the light passes through a transparent region before it reaches the opaque region. Finally, the performance of the two types of diodes is analyzed with the objective of finding the optimal width of the absorption area. The quantum efficiency depends strongly on the way in which the light is introduced. The structure in which the radiation is absorbed following its crossing the transparent region is associated with both higher quantum efficiency and homogeneity. In addition, for absorption region widths higher than a certain minimum, the quantum efficiency in this case is insensitive to the width of the absorption region.

  4. Effect of surface fields on the dynamic resistance of planar HgCdTe mid-wavelength infrared photodiodes

    NASA Astrophysics Data System (ADS)

    He, Kai; Zhou, Song-Min; Li, Yang; Wang, Xi; Zhang, Peng; Chen, Yi-Yu; Xie, Xiao-Hui; Lin, Chun; Ye, Zhen-Hua; Wang, Jian-Xin; Zhang, Qin-Yao

    2015-05-01

    This work investigates the effect of surface fields on the dynamic resistance of a planar HgCdTe mid-wavelength infrared photodiode from both theoretical and experimental aspects, considering a gated n-on-p diode with the surface potential of its p-region modulated. Theoretical models of the surface leakage current are developed, where the surface tunnelling current in the case of accumulation is expressed by modifying the formulation of bulk tunnelling currents, and the surface channel current for strong inversion is simulated with a transmission line method. Experimental data from the fabricated devices show a flat-band voltage of V F B = - 5.7 V by capacitance-voltage measurement, and then the physical parameters for bulk properties are determined from the resistance-voltage characteristics of the diode working at a flat-band gate voltage. With proper values of the modeling parameters such as surface trap density and channel electron mobility, the theoretical R 0 A product and corresponding dark current calculated from the proposed model as functions of the gate voltage Vg demonstrate good consistency with the measured values. The R 0 A product remarkably degenerates when Vg is far below or above VFB because of the surface tunnelling current or channel current, respectively; and it attains the maximum value of 5.7 × 10 7 Ω . cm 2 around the transition between surface depletion and weak inversion when V g ≈ - 4 V , which might result from reduced generation-recombination current.

  5. Analysis of beverages for Hg, As, Pb, and Cd with a field portable X-ray fluorescence analyzer.

    PubMed

    Anderson, David L

    2010-01-01

    Analytical capabilities of a handheld X-ray tube analyzer for analysis of beverages were evaluated. Sets of standard solutions for the elements Hg, As, Pb, and Cd were prepared with mass fractions up to 5000 mg/kg. A thirst quencher beverage was spiked with these elements up to mass fractions of 2500 mg/kg. Portions of these solutions were placed in standard X-ray fluorescence (XRF) cells, as well as the original container, and analyzed by using a field portable Innov-X alpha-6000s XRF tube-type analyzer. Uncorrected analyzer output usually yielded qualitative or semiquantitative results for the spiked beverages in X-ray cells. Average correction factors applied to analyzer output yielded accurate (in terms of z-scores) quantitative results for As above 20 mg/kg and qualitative or semiquantitative results for the other elements. Weighted quadratic fit calibrations provided accurate quantitative or semiquantitative results for all elements at levels above 20 mg/kg. The instrument's preset X-ray overlap correction algorithm worked well for the beverage spiked with all four elements. Spiked beverages analyzed through the wall of the original polyethylene terephthalate container produced accurate results within measurement uncertainties after application of "container wall" correction factors.

  6. Heterojunction depth in P+-on-n eSWIR HgCdTe infrared detectors: generation-recombination suppression

    NASA Astrophysics Data System (ADS)

    Schuster, J.; DeWames, R. E.; DeCuir, E. A.; Bellotti, E.; Dhar, N.; Wijewarnasuriya, P. S.

    2015-08-01

    A key design feature of P+-on-n HgCdTe detectors is the depth of the p-type region. Normally, homojunction architectures are utilized where the p-type region extends into the narrow-gap absorber layer. This facilitates the collection of photo-carriers from the absorber layer to the contact; however, this may result in excess generation-recombination (G-R) current if defects are present. Alternatively, properly adopting a heterojunction architecture confines the p-type region (and the majority of the electric field) solely to the wide-gap layer. Junction placement is critical since the detector performance is now dependent on the following sensitivity parameters: p-type region depth, doping, valence band offset, lifetime and detector bias. Understanding the parameter dependence near the hetero-metallurgical interface where the compositional grading occurs and the doping is varied as either a Gaussian or error function is vital to device design. Numerical modeling is now essential to properly engineer the electric field in the device to suppress G-R current while accounting for the aforementioned sensitivity parameters. The simulations reveal that through proper device design the p-type region can be confined to the wide-gap layer, reducing G-R related dark current, without significantly reducing the quantum efficiency at the operating bias V = -0.100V.

  7. Dark Current Characterization of SW HgCdTe IRFPAs Detectors on Si Substrate with Long Time Integration

    NASA Astrophysics Data System (ADS)

    Song, P. Y.; Ye, Z. H.; Huang, A. B.; Chen, H. L.; Hu, X. N.; Ding, R. J.; He, L.

    2016-09-01

    The dark currents of two short wave (SW) HgCdTe infrared focal plane arrays (IRFPA) detectors hybridized with direct injection (DI) readout and capacitance transimpedance amplifier (CTIA) with long time integration were investigated. The cutoff wavelength of the two SW IRFPAs is about 2.6 μm at 84 K. The dark current densities of DI and CTIA samples are approximately 8.0 × 10-12 A/cm2 and 7.2 × 10-10 A/cm2 at 110 K, respectively. The large divergence of the dark current density might arise from the injection efficiency difference of the two readouts. The low injection efficiency of the DI readout, compared with the high injection efficiency of the CTIA readout at low temperature, makes the dark current density of the DI sample much lower than that of the CTIA sample. The experimental value of injection efficiency of the DI sample was evaluated as 1.1% which is consistent with its theoretical value.

  8. β-CD Dimer-immobilized Ag Assembly Embedded Silica Nanoparticles for Sensitive Detection of Polycyclic Aromatic Hydrocarbons

    PubMed Central

    Hahm, Eunil; Jeong, Daham; Cha, Myeong Geun; Choi, Jae Min; Pham, Xuan-Hung; Kim, Hyung-Mo; Kim, Hwanhee; Lee, Yoon-Sik; Jeong, Dae Hong; Jung, Seunho; Jun, Bong-Hyun

    2016-01-01

    We designed a β-CD dimer on silver nanoparticles embedded with silica nanoparticles (Ag@SiO2 NPs) structure to detect polycyclic aromatic hydrocarbons (PAHs). Silica NPs were utilized as a template for embedding silver NPs to create hot spot structures and enhance the surface-enhanced Raman scattering (SERS) signal, and a thioether-bridged dimeric β-CD was immobilized on Ag NPs to capture PAHs. The assembled Ag NPs on silica NPs were confirmed by TEM and the presence of β-CD dimer on Ag@SiO2 was confirmed by UV-vis and attenuated total reflection-Fourier transform infrared spectroscopy. The β-CD dimer@Ag@SiO2 NPs were used as SERS substrate for detecting perylene, a PAH, directly and in a wide linearity range of 10−7 M to 10−2 M with a low detection limit of 10−8 M. Also, the β-CD dimer@Ag@SiO2 NPs exhibited 1000-fold greater sensitivity than Ag@SiO2 NPs in terms of their perylene detection limit. Furthermore, we demonstrated the possibility of detecting various PAH compounds using the β-CD dimer@Ag@SiO2 NPs as a multiplex detection tool. Various PAH compounds with the NPs exhibited their distinct SERS bands by the ratio of each PAHs. This approach of utilizing the assembled structure and the ligands to recognize target has potential for use in sensitive analytical sensors. PMID:27184729

  9. β-CD Dimer-immobilized Ag Assembly Embedded Silica Nanoparticles for Sensitive Detection of Polycyclic Aromatic Hydrocarbons

    NASA Astrophysics Data System (ADS)

    Hahm, Eunil; Jeong, Daham; Cha, Myeong Geun; Choi, Jae Min; Pham, Xuan-Hung; Kim, Hyung-Mo; Kim, Hwanhee; Lee, Yoon-Sik; Jeong, Dae Hong; Jung, Seunho; Jun, Bong-Hyun

    2016-05-01

    We designed a β-CD dimer on silver nanoparticles embedded with silica nanoparticles (Ag@SiO2 NPs) structure to detect polycyclic aromatic hydrocarbons (PAHs). Silica NPs were utilized as a template for embedding silver NPs to create hot spot structures and enhance the surface-enhanced Raman scattering (SERS) signal, and a thioether-bridged dimeric β-CD was immobilized on Ag NPs to capture PAHs. The assembled Ag NPs on silica NPs were confirmed by TEM and the presence of β-CD dimer on Ag@SiO2 was confirmed by UV-vis and attenuated total reflection-Fourier transform infrared spectroscopy. The β-CD dimer@Ag@SiO2 NPs were used as SERS substrate for detecting perylene, a PAH, directly and in a wide linearity range of 10-7 M to 10-2 M with a low detection limit of 10-8 M. Also, the β-CD dimer@Ag@SiO2 NPs exhibited 1000-fold greater sensitivity than Ag@SiO2 NPs in terms of their perylene detection limit. Furthermore, we demonstrated the possibility of detecting various PAH compounds using the β-CD dimer@Ag@SiO2 NPs as a multiplex detection tool. Various PAH compounds with the NPs exhibited their distinct SERS bands by the ratio of each PAHs. This approach of utilizing the assembled structure and the ligands to recognize target has potential for use in sensitive analytical sensors.

  10. New chalcogenide glasses in the CdTe-AgI-As{sub 2}Te{sub 3} system

    SciTech Connect

    Kassem, M.; Le Coq, D.; Boidin, R.; Bychkov, E.

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Determination of the glass-forming region in the pseudo-ternary CdTe-AgI-As{sub 2}Te{sub 3} system. Black-Right-Pointing-Pointer Characterization of macroscopic properties of the new CdTe-AgI-As{sub 2}Te{sub 3} glasses. Black-Right-Pointing-Pointer Characterization of the total conductivity of CdTe-AgI-As{sub 2}Te{sub 3} glasses. Black-Right-Pointing-Pointer Comparison between the selenide and telluride equivalent systems. -- Abstract: Chalcogenide glasses in the pseudo-ternary CdTe-AgI-As{sub 2}Te{sub 3} system were synthesized and the glass-forming range was determined. The maximum content of CdTe in this glass system was found to be equal to 15 mol.%. The macroscopic characterizations of samples have consisted in Differential Scanning Calorimetry, density, and X-ray diffraction measurements. The cadmium telluride addition does not generate any significant change in the glass transition temperature but the resistance of binary AgI-As{sub 2}Te{sub 3} glasses towards crystallisation is estimated to be decreasing on the base of {Delta}T = T{sub x} - T{sub g} parameter. The total electrical conductivity {sigma} was measured by complex impedance spectroscopy. First, the CdTe additions in the (AgI){sub 0.5}(As{sub 2}Te{sub 3}){sub 0.5} host glass, (CdTe){sub x}(AgI){sub 0.5-x/2}(As{sub 2}Te{sub 3}){sub 0.5-x/2} lead to a conductivity decrease at x {<=} 0.05. Then, the behaviour is reversed at 0.05 {<=} x {<=} 0.15. The obtained results are discussed by comparison with the equivalent selenide system.

  11. Toxic metal (Pb, Cd, Cr, and Hg) levels in Rapana venosa (Valenciennes, 1846), Eriphia verrucosa (Forskal, 1775), and sediment samples from the Black Sea littoral (Thrace, Turkey).

    PubMed

    Mülayim, A; Balkıs, H

    2015-06-15

    Rapana venosa (Valenciennes, 1846) and Eriphia verrucosa (Forskal, 1775) are the dominant benthic invertebrate species along the Thrace Coast of the western Black Sea. The aim of this study was to determine toxic metal (Hg, Cr, Cd, and Pb) accumulation levels in these species, as well as within littoral sediments from this area. Our results showed that all of the metals, except for Cd, were below that in average shale. The measured accumulation levels were mostly within the range of what is naturally found within the earth's crust. However, some study stations did have increased concentrations, indicating anthropogenic pollution in these areas. The Cd contents of E. verrucosa collected from all our study stations were well above the limits set by the Turkish Food Codex, especially in Kıyıköy, whereas Pb content was close to the limit at all stations and exceeded the limit in Kıyıköy, but Hg content was below the limit at all stations. Cd content of R. venosa exceeded the limit only in Kumköy. Pb content was below the limit, and Hg was at or slightly above the limit at all stations. PMID:25913797

  12. Toxic metal (Pb, Cd, Cr, and Hg) levels in Rapana venosa (Valenciennes, 1846), Eriphia verrucosa (Forskal, 1775), and sediment samples from the Black Sea littoral (Thrace, Turkey).

    PubMed

    Mülayim, A; Balkıs, H

    2015-06-15

    Rapana venosa (Valenciennes, 1846) and Eriphia verrucosa (Forskal, 1775) are the dominant benthic invertebrate species along the Thrace Coast of the western Black Sea. The aim of this study was to determine toxic metal (Hg, Cr, Cd, and Pb) accumulation levels in these species, as well as within littoral sediments from this area. Our results showed that all of the metals, except for Cd, were below that in average shale. The measured accumulation levels were mostly within the range of what is naturally found within the earth's crust. However, some study stations did have increased concentrations, indicating anthropogenic pollution in these areas. The Cd contents of E. verrucosa collected from all our study stations were well above the limits set by the Turkish Food Codex, especially in Kıyıköy, whereas Pb content was close to the limit at all stations and exceeded the limit in Kıyıköy, but Hg content was below the limit at all stations. Cd content of R. venosa exceeded the limit only in Kumköy. Pb content was below the limit, and Hg was at or slightly above the limit at all stations.

  13. Health risk of Hg, Pb, Cd, Zn, and Cu to the inhabitants around Huludao Zinc Plant in China via consumption of vegetables.

    PubMed

    Zheng, Na; Wang, Qichao; Zheng, Dongmei

    2007-09-20

    Huludao Zinc Plant in Huludao City, China is the largest zinc smelting plant in Asia. Heavy metals have contaminated its neighboring environment seriously. We collected 20 vegetables and the corresponding soil samples from eight sampling plots near Huludao Zinc Plant to investigate health risk of Hg, Pb, Cd, Zn, and Cu to the inhabitants around Huludao Zinc Plant in China via consumption of vegetables. Transfer factor (TF) values of Hg, Pb, Cd, Zn, and Cu from soil to vegetable and the target hazard quotients (THQs) to the possible health risks to local population through the food chain transfer were calculated accordingly. TF values of heavy metals from soil to vegetable decrease in the order of Cd>Zn>Cu>Pb>Hg. These TF values of leaves are higher than other tissues. Daily intakes of Hg, Pb, Cd, Zn, and Cu through the consumption of vegetables are 1.322, 574.3, 301.4, 5263, and 292.5 microg, respectively, for adults, and 1.029, 446.8, 234.5, 4095, and 227.6 microg, respectively, for children around Huludao Zinc Plant. This would lead to potential health risk, especially for children, since Cd or Pb individual THQ is high than 1. The total metal THQs (TTHQs) due to consumption of vegetables for adult and child are 5.79-9.90, 7.6-13.0, respectively. Comparing TTHQs in the sampling plots of different distances to Huludao Zinc Plant, it indicate that the health risks to inhabitants close to Huludao Zinc Plant (<500 m) is the highest, and at >1000 m distance is relatively higher than in 500-1000 m distance. However, the inhabitants who lived in 500-1000 m distance to Huludao Zinc Plant is also experiencing the adverse health risk due to TTHQ being higher than 1.

  14. Extending the Astronomical Application of Photon Counting HgCdTe Linear Avalanche Photo-Diode Arrays to Low Background Space Observations.

    NASA Astrophysics Data System (ADS)

    Hall, Donald

    The high quantum efficiency and very low dark current, together with the ability to set the wavelength cutoff from one to far beyond 5.5 microns, of large format HAWAII HgCdTe arrays have already made them the workhorse for NASA space astronomy (and related) observations in the 1 to 5.5 micron infrared. They have performed outstandingly on Hubble Wide Field Camera 3 and WISE (and also Deep Impact/EPOXI and OCO-2) and are crucial to the two major NASA Astrophysics missions, JWST and WFIRST, and to Euclid. The proposed investigation seeks to extend these benefits to the most demanding observations those that seek to wring information from only a few photons (starved due to either the intrinsic faintness of the source or the need for high spectral or time resolution) or to discriminate a weak signature against a bright source. We will characterize, and optimize for space astronomy observations, the unique linear avalanche properties of HgCdTe photo-diodes (HgCdTe L-APDs) that allow noiseless (i.e. faithfully preserves the Poisson statistics of the incoming photons) avalanche multiplication of individual photo-electrons. 2.5 micron HgCdTe L-APD technology, developed for infrared eye-safe LIDAR and range gated imaging, is already benefiting infrared wavefront sensing for ground based adaptive optics. In HgCdTe the L-APD gain and the onset voltage for tunneling current are exponential functions of bandgap while also varying with cryogenic operating temperature. The unique HgCdTe bandgap engineering that allows tuning of the cutoff wavelength can be used to critically improve avalanche performance for specific applications. We will thoroughly evaluate avalanche performance at several representative bandgaps so as to allow model prediction of performance over the critical 1 to 5 micron spectral interval. The proposed investigation will hybridize modest 32x32 arrays of HgCdTe L-APDs to photon counting readouts already developed under another award and characterize their

  15. Influence of reactive sulfide (AVS) and supplementary food on Ag, Cd and Zn bioaccumulation in the marine polychaete Neanthes arenaceodentata

    USGS Publications Warehouse

    Lee, J.-S.; Lee, B.-G.; Yoo, H.; Koh, C.-H.; Luoma, S.N.

    2001-01-01

    A laboratory bioassay determined the relative contribution of various pathways of Ag, Cd and Zn bioaccumulation in the marine polychaete Neanthes arenaceodentata exposed to moderately contaminated sediments. Juvenile worms were exposed for 25 d to experimental sediments containing 5 different reactive sulfide (acid volatile sulfides, AVS) concentrations (1 to 30 ??mol g-1), but with constant Ag, Cd, and Zn concentrations of 0.1, 0.1 and 7 ??mol g-1, respectively. The sediments were supplemented with contaminated food (TetraMin??) containing 3 levels of Ag-Cd-Zn (uncontaminated, 1?? or 5??1 metal concentrations in the contaminated sediment). The results suggest that bioaccumulation of Ag, Cd and Zn in the worms occurred predominantly from ingestion of contaminated sediments and contaminated supplementary food. AVS or dissolved metals (in porewater and overlying water) had a minor effect on bioaccumulation of the 3 metals in most of the treatments. The contribution to uptake from the dissolved source was most important in the most oxic sediments, with maximum contributions of 8% for Ag, 30% for Cd and 20% for Zn bioaccumulation. Sediment bioassays where uncontaminated supplemental food is added could seriously underestimate metal exposures in an equilibrated system; N. arenaceodentata feeding on uncontaminated food would be exposed to 40-60% less metal than if the food source was equilibrated (as occurs in nature). Overall, the results show that pathways of metal exposure are dynamically linked in contaminated sediments and shift as external geochemical characteristics and internal biological attributes vary.

  16. Investigation of surface potential in the V-defect region of MBE Cd{sub x}Hg{sub 1−x}Te film

    SciTech Connect

    Novikov, V. A. Grigoryev, D. V.

    2015-03-15

    Atomic-force microscopy is used to investigate the distribution of the contact-potential difference (surface potential) in Cd{sub x}Hg{sub 1−x}Te epitaxial films grown by molecular-beam epitaxy. Modification of the solid-solution composition near the V-defect results in a variation in the contact-potential difference. It is shown that the solid-solution composition varies by ∼0.05 (2.5 at %) towards increasing mercury content in the V-defect region, and a region of mercury depletion by 0.36 at % is observed at the V-defect periphery. From analysis of the surface-potential distribution, it is shown that the Cd{sub x}Hg{sub 1−x}Te epitaxial film contains unform V-defects with a diameter less than 1 μm in addition to macroscopic V-defects.

  17. Temperature dependence of thermal conductivity and thermoelectric effect in solid solutions of Cd/sub x/Hg/sub 1-x/Se

    SciTech Connect

    Paranchich, S.Yu.; Makogonenko, V.N.; Paranchich, L.D.

    1987-08-01

    Comparison of experimental and theoretical charged carrier concentration dependence of the thermoemf in Cd/sub 0.1/Hg/sub 0.9/Se indicates that the electron scattering is most likely from impurity ions as well as from piezoelectric and optical phonons at 80/sup 0/K. It has been shown that the thermoelectric efficiency parameter reaches 1.2 x 10/sup -3/ x /sup 0/K/sup -1/ at 400/sup 0/K for x = 0.05 and electron concentration 4.2 x 10/sup 17/ cm/sup -3/ in the solid solution Cd/sub x/Hg/sub 1-x/Se (0 less than or equal to x less than or equal to 0.4).

  18. A highly sensitive multi-element HgCdTe e-APD detector for IPDA lidar applications

    NASA Astrophysics Data System (ADS)

    Beck, Jeff; McCurdy, James; Skokan, Mark; Kamilar, Chris; Scritchfield, Richard; Welch, Terry; Mitra, Pradip; Sun, Xiaoli; Abshire, James; Reiff, Kirk

    2013-05-01

    A 16 element HgCdTe e-APD detector has been developed for lidar receivers that has significant improvements in sensitivity in the spectral range from < 1μm to 4 μm. A demonstration detector consisting of a 4x4 APD detector array, with 80 μm square elements, a custom CMOS readout integrated circuit (ROIC), a closed cycle cooler-Dewar, and support electronics has been designed, fabricated, and tested. The custom ROIC design provides > 6 MHz bandwidth with low noise and 21 selectable gains. Ninety-six arrays were fabricated with 69% of the arrays meeting the dark current spec in the center 4 pixels at 10 V bias where the APD gain was expected to be around 150. Measurements to 12 V on one array showed APD gains of 654 with a gain normalized dark currents of 1.2 fA to 3.2 fA. The lowest dark current array showed a maximum dark current of 6.2 pA at 10 V and 77 K. The 4.4 μm cutoff detector was characterized at an operating temperature of 77K with a 1.55 μm, 1μs wide, laser pulse. The photon conversion efficiency at unity gain was 91%. The mean measured APD gain at 77 K was 308 at 11V, the responsivity was 782 μV/pW, the average NEP was 1.04 fW/Hz1/2. The bandwidth was 6.8 MHz, and the broadband NEP was 2.97 pW. This detector offers a wide spectral response, dynamic range, and substantially improved sensitivity and lifetime for integrated path differential absorption (IPDA) lidar measurements of atmospheric trace gases such as CO2 and CH4.

  19. Effect of surface fields on the dynamic resistance of planar HgCdTe mid-wavelength infrared photodiodes

    SciTech Connect

    He, Kai; Wang, Xi; Zhang, Peng; Chen, Yi-Yu; Zhou, Song-Min; Xie, Xiao-Hui; Lin, Chun Ye, Zhen-Hua; Wang, Jian-Xin; Zhang, Qin-Yao; Li, Yang

    2015-05-28

    This work investigates the effect of surface fields on the dynamic resistance of a planar HgCdTe mid-wavelength infrared photodiode from both theoretical and experimental aspects, considering a gated n-on-p diode with the surface potential of its p-region modulated. Theoretical models of the surface leakage current are developed, where the surface tunnelling current in the case of accumulation is expressed by modifying the formulation of bulk tunnelling currents, and the surface channel current for strong inversion is simulated with a transmission line method. Experimental data from the fabricated devices show a flat-band voltage of V{sub FB}=−5.7 V by capacitance-voltage measurement, and then the physical parameters for bulk properties are determined from the resistance-voltage characteristics of the diode working at a flat-band gate voltage. With proper values of the modeling parameters such as surface trap density and channel electron mobility, the theoretical R{sub 0}A product and corresponding dark current calculated from the proposed model as functions of the gate voltage V{sub g} demonstrate good consistency with the measured values. The R{sub 0}A product remarkably degenerates when V{sub g} is far below or above V{sub FB} because of the surface tunnelling current or channel current, respectively; and it attains the maximum value of 5.7×10{sup 7} Ω · cm{sup 2} around the transition between surface depletion and weak inversion when V{sub g}≈−4 V, which might result from reduced generation-recombination current.

  20. Task-specific ionic liquids incorporating novel cations for the coordination and extraction of Hg2+ and Cd2+: synthesis, characterization, and extraction studies.

    PubMed

    Visser, Ann E; Swatloski, Richard P; Reichert, W Matthew; Mayton, Rebecca; Sheff, Sean; Wierzbicki, Andrzej; Davis, James H; Rogers, Robin D

    2002-06-01

    A series of hydrophobic task-specific ionic liquids designed to extract Hg2+ and Cd2+ from water were prepared by appending urea-, thiourea-, and thioether-substituted alkyl groups to imidazoles and combining the resulting cationic species with PF6-. The new ionic liquids were characterized and investigated for their metal ion extraction capabilities. When used in liquid/liquid extraction of Hg2+ and Cd2+ from aqueous solutions, the metal ion distribution ratios increased several orders of magnitude, regardless of whether the ionic liquids were used as the sole extracting phase or doped into a series of [1-alkyl-3-methylimidazolium][PF6] (alkyl = n-C4-C8) ionic liquids to form a 1:1 solution. In the 1:1 mixtures, as the length of the alkyl chain increased from butyl to hexyl to octyl, the metal ion distribution ratios increased. Increasing the ratio TSIL/[C4mim][PF6] resulted in higher distribution ratios for both Hg2+ and Cd2+. Overall, the thiourea- and urea-derivatized cations yielded the highest distribution ratios, and those for Hg2+ were higher than those for Cd2+; however, a change in aqueous-phase pH does not promote the stripping of metal ions from the extracting phase. The combination of these imidazolium cations and PF6- produced ionic liquids with decreased thermal stability in comparison to [C(n)mim]-[PF6]. Gaussian98 restricted Hartree-Fock geometry optimizations for one of the thiourea-appended cations shows the charge delocalization around the ring and suggests that the thiourea group may aid in deprotonating the imidazolium ring and may be responsible for the lowered thermal stability of these cations.

  1. Recent progress in the study of characterization and properties of HgCdTe at the National Laboratory for Infrared Physics in China

    NASA Astrophysics Data System (ADS)

    Chu, Junhao; Liu, Kun; Chang, Young; Liu, Pulin; Li, Biao; Guo, Shaoling; Chen, Minghui; Tang, Dingyuan

    1997-08-01

    The characterization of impurities, defects, uniformity and some fundamental properties for the bulk and epitaxial HgCdTe(MCT) material undoped and doped with Sb, As, Fe have been investigated recently in our laboratory by means of photoluminescence, magneto-photoconductivity, quantum capacitance spectroscopy, transport measurements and other contactless nd nondestructive methods such as the IR, far-IR and millimeter wave measurements. This paper reports a portion of these new results.

  2. Numerical study of the intrinsic recombination carriers lifetime in extended short-wavelength infrared detector materials: A comparison between InGaAs and HgCdTe

    NASA Astrophysics Data System (ADS)

    Wen, Hanqing; Bellotti, Enrico

    2016-05-01

    Intrinsic carrier lifetime due to radiative and Auger recombination in HgCdTe and strained InGaAs has been computed in the extended short-wavelength infrared (ESWIR) spectrum from 1.7 μm to 2.7 μm. Using the Green's function theory, both direct and phonon-assisted indirect Auger recombination rates as well as the radiative recombination rates are calculated for different cutoff wavelengths at 300 K with full band structures of the materials. In order to properly model the full band structures of strained InGaAs, an empirical pseudo-potential model for the alloy is fitted using the virtual crystal approximation with spin-orbit coupling included. The results showed that for InxGa1-xAs grown on InP substrate, the compressive strain, which presents in the film when the cutoff wavelength is longer than 1.7 μm, leads to decrease of Auger recombination rate and increase of radiative recombination rate. Since the dominant intrinsic recombination mechanism in this spectral range is radiative recombination, the overall intrinsic carrier lifetime in the strained InGaAs alloys is shorter than that in the relaxed material. When compared to the relaxed HgCdTe, both relaxed and compressively strained InGaAs alloys show shorter intrinsic carrier lifetime at the same cutoff wavelength in room temperature which confirms the potential advantage of HgCdTe as wide-band infrared detector material. While HgCdTe offers superior performance, ultimately the material of choice for ESWIR application will also depend on material quality and cost.

  3. Simultaneous determination of Cu 2+, Zn 2+, Cd 2+, Hg 2+ and Pb 2+ by using second-derivative spectrophotometry method

    NASA Astrophysics Data System (ADS)

    Han, Yanyan; Li, Yan; Si, Wei; Wei, Dong; Yao, Zhenxing; Zheng, Xianpeng; Du, Bin; Wei, Qin

    2011-09-01

    A new method of simultaneous determination of Cu 2+, Zn 2+, Cd 2+, Hg 2+ and Pb 2+ is proposed here by using the second-derivative spectrophotometry method. In pH = 10.35 Borax-NaOH buffer, using meso-tetra (3-methoxyl-4-hydroxylphenyl) porphyrin ([T-(3-MO-4-HP)P]) as chromomeric reagent, micelle solution was formed after Tween-80 surfactant was added into the solution containing Cu 2+, Zn 2+, Cd 2+, Hg 2+ and Pb 2+ ions. The original absorption spectrum of the above complexes was obtained after heating in the boiling water for 25 min. The second-derivative absorption peaks of five metal-porphyrin complexes can be separated from the original absorption spectrum by using chemometric tool. In this way, Cu 2+, Zn 2+, Cd 2+, Hg 2+ and Pb 2+ ions can be determined simultaneously. Under the optimal conditions, the linear ranges of the calibration curve were 0-0.60, 0-0.60, 0-0.40, 0-0.80 and 0-0.48 μg mL -1 for Cu 2+, Zn 2+, Cd 2+, Hg 2+ and Pb 2+, respectively. The molar absorptivity of these color systems were 1.38 × 10 5, 1.01 × 10 5, 3.24 × 10 5, 1.07 × 10 5 and 1.29 × 10 5 L mol -1 cm -1. The method developed in this paper has advantages in selectivity, sensitivity, operation and can effectively resolve spectra overlapping problem. This method has been applied to determine the real samples with satisfactory results.

  4. Magnetotransmission of unpolarized infrared radiation in Hg1 - x Cd x Cr2Se4 (0 ≤ x ≤ 1) single crystals studied using the voigt geometry

    NASA Astrophysics Data System (ADS)

    Sukhorukov, Yu. P.; Telegin, A. V.; Bebenin, N. G.; Patrakov, E. I.; Naumov, S. V.; Fedorov, V. A.; Menshchikova, T. K.

    2013-11-01

    The features characterizing the behavior of magnetotransmission in Hg1 - x Cd x Cr2Se4 single crystals are studied using natural light in the infrared spectral range. The relation between the changes in the magneto-optical properties and in the electron band structure is found. It is shown that the most significant changes in the magnetotransmission spectrum and the band structure occur within the 0.1 < x < 0.25 range.

  5. Modeling of electron energy spectra and mobilities in semi-metallic Hg{sub 1−x}Cd{sub x}Te quantum wells

    SciTech Connect

    Melezhik, E. O. Gumenjuk-Sichevska, J. V.; Sizov, F. F.

    2015-11-21

    Electron mobility, energy spectra, and intrinsic carrier concentrations in the n-type Hg{sub 0.32}Cd{sub 0.68}Te/Hg{sub 1−x}Cd{sub x}Te/Hg{sub 0.32}Cd{sub 0.68}Te quantum well (QW) in semi-metallic state are numerically modeled. Energy spectra and wave functions were calculated in the framework of the 8-band k-p Hamiltonian. In our model, electron scattering on longitudinal optical phonons, charged impurities, and holes has been taken into account, and the mobility has been calculated by an iterative solution of the Boltzmann transport equation. Our results show that the increase of the electron concentration in the well enhances the screening of the 2D electron gas, decreases the hole concentration, and can ultimately lead to a high electron mobility at liquid nitrogen temperatures. The increase of the electron concentration in the QW could be achieved in situ by delta-doping of barriers or by applying the top-gate potential. Our modeling has shown that for low molar composition x the concentration of holes in the well is high in a wide range of electron concentrations; in this case, the purity of samples does not significantly influence the electron mobility. These results are important in the context of establishing optimal parameters for the fabrication of high-mobility Hg{sub 1−x}Cd{sub x}Te quantum wells able to operate at liquid nitrogen temperature and thus suitable for applications in terahertz detectors.

  6. Development of Hg1-xCd xSe for 3rd Generation Focal Plane Arrays using Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Doyle, Kevin

    Hg1-xCd xSe grown on nearly lattice-matched GaSb substrates could serve as a new basis for infrared detector development. The preparation of the GaSb substrate surfaces and the growth of ZnTe1-xSex buffer layers via molecular beam epitaxy were investigated. ZnTe and ZnTe1- xSex layers were grown on GaSb substrates prepared with atomic hydrogen cleaning. The lattice constant of ZnTe1-xSex was tuned by controlling the ratio of Se/Te beam equivalent pressures, and ZnTe1- xSex was found to be lattice-matched to GaSb for x=0.01. Confocal photoluminescence measurements indicated that ZnTe0.99Se0.01 layers grown on GaSb have dislocation densities ˜7x104 cm-2, indicating that ZnTe0.99Se0.01/GaSb provides a high quality substrate with low dislocation densities for Hg1-xCd xSe growth. In parallel with the ZnTe1-xSe x/GaSb substrate development, the growth of Hg1- xCdxSe was studied via molecular beam epitaxy on GaSb substrates and Si substrates with ZnTe buffer layers. Growth rate, composition, and surface quality were evaluated for different growth parameters. Two sources of Se were used, an effusion cell loaded with 5N purity source material that produced a predominantly Se6 flux, and a disassociation source loaded with 6N purity source material that could produce either a predominantly Se2 or a predominantly Se6 flux. For a given substrate temperature and Hg overpressure, the growth rate was controlled by the Se flux and the x-value was controlled by the Cd/Se flux ratio. Growths under Hg-deficient conditions produced "needle" and "diamond"-shaped defects. The optimal substrate temperature was found to be 90- 110°C for growths performed with a predominantly Se 6 flux. from the effusion cell and a standard Hg flux of 2.5x10 -4 Torr. Previous studies of nominally undoped Hg1-xCd xSe samples have reported large background electron concentrations ranging from 1017-1018 cm-3 at temperatures as low as 4K. In the study reported here, the use of Se source material with 6N

  7. Availability of sediment-bound Cd, Co, and Ag to mussels

    SciTech Connect

    Gagnon, C.; Fisher, N.S.

    1995-12-31

    Ingested sediment is one potentially important source of metals for benthic organisms. The influence of physical and chemical properties of oxidized sediments on the bioavailability of metals to marine filter feeders is largely unknown. The authors examined the relative importance of specific sedimentary components that may exert control on the uptake of Cd, Co, and Ag in the mussel Mytilus edulis. Iron and manganese oxides, montmorillonite clay, silica, and natural sediment particles were triple labeled with the gamma emitters {sup 109}Cd, {sup 57}Co, and {sup 110m}Ag. Some particles were also coated with fulvic acid (FA) to simulate the influence of organic coating on metal bioavailability. Metals associated with FA-coated particles were generally absorbed by mussels to a greater extent than metals associated with uncoated particles. Desorption experiments with labeled particles at pH 5 were performed in parallel to simulate the behavior of food-bound metals in the acidic gut of bivalves. High correlations (r > 0.97) between the amount of desorbed metal under these conditions and the assimilation efficiency for metals from FA-coated particles were noted among coated particles but not uncoated particles (r < 0.6). These results suggest that the relation between metal partitioning to sediments and biological availability of the metal is not obvious, since the organic coatings and the acidic digestion process influence assimilation of sediment-bound metals.

  8. Determination of charge-carrier diffusion length in the photosensing layer of HgCdTe n-on-p photovoltaic infrared focal plane array detectors

    SciTech Connect

    Vishnyakov, A. V.; Stuchinsky, V. A. Brunev, D. V.; Zverev, A. V.; Dvoretsky, S. A.

    2014-03-03

    In the present paper, we propose a method for evaluating the bulk diffusion length of minority charge carriers in the photosensing layer of photovoltaic focal plane array (FPA) photodetectors. The method is based on scanning a strip-shaped illumination spot with one of the detector diodes at a low level of photocurrents j{sub ph} being registered; such scanning provides data for subsequent analysis of measured spot-scan profiles within a simple diffusion model. The asymptotic behavior of the effective (at j{sub ph} ≠ 0) charge-carrier diffusion length l{sub d} {sub eff} as a function of j{sub ph} for j{sub ph} → 0 inferred from our experimental data proved to be consistent with the behavior of l{sub d} {sub eff} vs j{sub ph} as predicted by the model, while the obtained values of the bulk diffusion length of minority carriers (electrons) in the p-HgCdTe film of investigated HgCdTe n-on-p FPA photodetectors were found to be in a good agreement with the previously reported carrier diffusion-length values for HgCdTe.

  9. The bulk generation-recombination processes and the carrier lifetime in mid-wave infrared and long-wave infrared liquid nitrogen cooled HgCdTe alloys

    NASA Astrophysics Data System (ADS)

    Jóźwikowski, K.; Kopytko, M.; Rogalski, A.

    2012-08-01

    Comprehensive study of the bulk generation-recombination mechanisms and the carrier lifetime in long wavelength and mid wavelength infrared indium-doped as well as arsenic- and mercury vacancies-doped HgCdTe ternary alloys at liquid nitrogen temperature has been done. The excess minority carrier lifetime in HgCdTe materials has been calculated by solving the set of non-linear transport equations under conditions of small deviation from equilibrium. The results of numerical calculations of the carrier lifetime determined by the Auger 1, Auger 7, and Shockley-Read-Hall mechanisms related to mercury vacancies have been compared with experimental data available in the literature. We re-examine the carrier lifetime, including the impact of the electrical screening on Coulomb interaction of carriers in the Auger process to explain certain inconsistency between theoretical prediction and experimental data especially in highly doped p-type HgCdTe material. Moreover, the marginal significance of the interband radiative recombination has been indicated.

  10. Synthesis, characterization, DFT and biological studies of isatinpicolinohydrazone and its Zn(II), Cd(II) and Hg(II) complexes

    NASA Astrophysics Data System (ADS)

    El-Gammal, O. A.; Rakha, T. H.; Metwally, H. M.; Abu El-Reash, G. M.

    2014-06-01

    Isatinpicolinohydrazone (H2IPH) and its Zn(II), Cd(II) and Hg(II) complexes have been synthesized and investigated using physicochemical techniques viz. IR, 1H NMR, 13C NMR, UV-Vis spectrometric methods and magnetic moment measurements. The investigation revealed that H2IPH acts as binegative tetradentate in Zn(II), neutral tridentate in Cd(II) and as neutral bidentate towards Hg(II) complex. Octahedral geometry is proposed for all complexes. The bond length, bond angle, chemical reactivity, energy components (kcal/mol), binding energy (kcal/mol) and dipole moment (Debyes) for all the title compounds were evaluated by DFT and also MEP for the ligand is shown. Theoretical infrared intensities of H2IPH and also the theoretical electronic spectra of the ligand and its complexes were calculated. The thermal behavior and the kinetic parameters of degradation were determined using Coats-Redfern and Horowitz-Metzger methods. The in vitro antibacterial studies of the complexes proved them as growth inhibiting agents. The DDPH antioxidant of the compounds have been screened. Antitumor activity, carried out in vitro on human mammary gland (breast) MCF7, have shown that Hg(II) complex exhibited potent activity followed by Zn(II), Cd(II) complexes and the ligand.

  11. Opto-electronic Properties of Mid-Wavelength: n Type II InAs/InAs1- x Sb x and Hg1- x Cd x Te

    NASA Astrophysics Data System (ADS)

    De Wames, Roger E.

    2016-09-01

    There is significant interest in mid-wavelength type II strained layer superlattices (SLSs) and HgCdTe material systems for background limited performance, operating at significantly higher temperature, T ≥ 150 K, than InSb, T ≈ 80-90 K. A precise knowledge of the electronic and optical properties of these materials is desirable since they determine detector performance and are needed for input parameters in self-consistent physics-based predictive models. Recently, data on the optical absorption coefficient, and the hole minority carrier lifetime has become available, suggesting that in the extrinsic region the limiting recombination processes in mid-wavelength type II Ga-free SLSs are radiative and Shockley-Read-Hall (SRH). These findings provide the opportunity for comparisons with mid-wavelength HgCdTe. The comparisons show that the radiative recombination coefficients are similar; however, the SRH lifetime limited to 9 μs for the SLS implies that the dark current density is expected to be limited by bulk generation-recombination (G-R) SRH processes for temperatures below 160 K; hence requiring heterojunction designs to suppress the G-R dark currents and be diffusion limited. Mid-wavelength infrared HgCdTe photodiodes are shallow p+n photovoltaic devices and because of the very long SRH hole lifetime are diffusion radiatively limited photodiodes down to 80 K.

  12. ZnS, CdS and HgS nanoparticles via alkyl-phenyl dithiocarbamate complexes as single source precursors.

    PubMed

    Onwudiwe, Damian C; Ajibade, Peter A

    2011-01-01

    The synthesis of II-VI semiconductor nanoparticles obtained by the thermolysis of certain group 12 metal complexes as precursors is reported. Thermogravimetric analysis of the single source precursors showed sharp decomposition leading to their respective metal sulfides. The structural and optical properties of the prepared nanoparticles were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) UV-Vis and photoluminescence spectroscopy. The X-ray diffraction pattern showed that the prepared ZnS nanoparticles have a cubic sphalerite structure; the CdS indicates a hexagonal phase and the HgS show the presence of metacinnabar phase. The TEM image demonstrates that the ZnS nanoparticles are dot-shaped, the CdS and the HgS clearly showed a rice and spherical morphology respectively. The UV-Vis spectra exhibited a blue-shift with respect to that of the bulk samples which is attributed to the quantum size effect. The band gap of the samples have been calculated from absorption spectra and werefound to be about 4.33 eV (286 nm), 2.91 eV (426 nm) and 4.27 eV (290 nm) for the ZnS, CdS and HgS samples respectively. PMID:22016607

  13. ZnS, CdS and HgS Nanoparticles via Alkyl-Phenyl Dithiocarbamate Complexes as Single Source Precursors

    PubMed Central

    Onwudiwe, Damian C.; Ajibade, Peter A.

    2011-01-01

    The synthesis of II-VI semiconductor nanoparticles obtained by the thermolysis of certain group 12 metal complexes as precursors is reported. Thermogravimetric analysis of the single source precursors showed sharp decomposition leading to their respective metal sulfides. The structural and optical properties of the prepared nanoparticles were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) UV-Vis and photoluminescence spectroscopy. The X-ray diffraction pattern showed that the prepared ZnS nanoparticles have a cubic sphalerite structure; the CdS indicates a hexagonal phase and the HgS show the presence of metacinnabar phase. The TEM image demonstrates that the ZnS nanoparticles are dot-shaped, the CdS and the HgS clearly showed a rice and spherical morphology respectively. The UV-Vis spectra exhibited a blue-shift with respect to that of the bulk samples which is attributed to the quantum size effect. The band gap of the samples have been calculated from absorption spectra and werefound to be about 4.33 eV (286 nm), 2.91 eV (426 nm) and 4.27 eV (290 nm) for the ZnS, CdS and HgS samples respectively. PMID:22016607

  14. Selected trace metals (As, Cd and Hg) distribution and contamination in the coastal wetland sediment of the northern Beibu Gulf, South China Sea.

    PubMed

    Gan, Huayang; Lin, Jinqin; Liang, Kai; Xia, Zhen

    2013-01-15

    Contamination with As, Cd and Hg, their spatial and temporal distribution are reported from the coastal wetland sediments of the northern Beibu Gulf, South China Sea. The content of As, Cd, Hg and TOC in surface sediments is 8.1±5.8 μg g⁻¹, 0.08±0.14μg g⁻¹, 0.034±0.028 μg g⁻¹ and 0.45±0.39%, respectively. The mean sedimentation rates are 0.93-1.37 cm year⁻¹ during 1920s to 2008 determined by ²¹⁰Pb and ¹³⁷Cs dating in three cores. The vertical profiles of As, Cd and Hg content in the cores retrieved from Qin and Nanliu River estuaries show increasing trends during 1985-2008 due to anthropogenic impact caused by local economic development. Locally the surface sediments have potential ecological risk of As to benthos according to the NOAA sediment quality guidelines.

  15. Facile electrochemical synthesis of CeO2@Ag@CdS nanotube arrays with enhanced photoelectrochemical water splitting performance.

    PubMed

    Zhao, Mi; Li, Haohua; Shen, Xiaoping; Ji, Zhenyuan; Xu, Keqiang

    2015-12-14

    In this work, for the first time, three-component CeO2@Ag@CdS heterostructured nanotube arrays with remarkable photoelectrochemical (PEC) performance have been synthesized by an electrodeposition method. In this configuration, the modification with Ag nanoparticles can significantly strengthen light absorption and provide an interior direct pathway to facilitate the separation and transport of photogenerated carriers. Therefore, the CeO2@Ag@CdS heterostructured nanotubes generate a remarkable photocurrent density of 2.14 mA cm(-2) at a potential of -0.2 V (vs. Ag/AgCl), which is 9.8 and 2.4 times higher than that of the two-component CeO2@Ag system (0.218 mA cm(-2)) and the CeO2@CdS system (0.879 mA cm(-2)), respectively. It also gives efficiency as high as 69% around 360 nm in the incident photon to electron conversion efficiency (IPCE) spectrum. Moreover, the stability of the photoelectrode was tested over 16 min. Furthermore, these results provide a valuable insight for the further development of such materials for PEC water splitting.

  16. Impact of a New Highly Sensitive HgCdTe Avalanche Photodiode Detector on Receiver Performance for the CO2 Sounder Lidar for the ASCENDS Mission

    NASA Astrophysics Data System (ADS)

    Sun, X.; Abshire, J. B.

    2013-12-01

    NASA Goddard Space Flight Center (GSFC) is currently developing a CO2 lidar as a candidate for the NASA's planned ASCENDS mission under the support of Earth Science Technology Office (ESTO) Instrument Incubator Program (IIP). As part of this work we have demonstrated new type of lower noise HgCdTe avalanche photodiode (APD) multi-element detector for the lidar receiver. This significantly improves the receiver sensitivity, lower the laser power, and reduce the receiver telescope size compared to InGaAs photomultiplier tubes (PMT) and APDs currently used. The HgCdTe APD arrays were designed and manufactured by DRS Technologies, Reconnaissance, Surveillance and Target Acquisition (RSTA) Division, which combines their mature HgCdTe APD detector in a hybrid package with a new custom cryogenic silicon preamplifier. The new detectors were specially designed for our airborne CO2 lidar and operate at ~ 77K inside a turn-key closed-cycle cooler. The detector has 80 μm square pixels in a 4x4 array, and >70% fill factor and was custom designed to match the optics of our airborne and eventually space-based CO2 lidar. The initial results of evaluating the detector at NASA GSFC showed the HgCdTe APD assembly has a quantum efficiency of ~90% near 1550-nm, >500 APD gain, 8-10 MHz electrical bandwidth, and an average noise equivalent power of <1fW/Hz1/2. The detector also has a much wider linear dynamic range than PMTs, since it operates in a linear analog mode and has variable gain. Given the wide range of surface reflectivities this is important for ASCENDS. The new detector also greatly improves our CO2 lidar's receiver sensitivity. Calculations show it enables us to reduce the laser transmitter power by half for the space borne instrument while staying with a conventional reasonably sized (~1.2 m) diameter receiver telescope. We will show analysis and laboratory test results of the CO2 lidar performance using a receiver with this new detector. We are also funded by NASA ESTO

  17. ROIC with on-chip sigma-delta AD converter for HgCdTe e-APD FPA

    NASA Astrophysics Data System (ADS)

    Chen, Guoqiang; Zhang, Junling; Wang, Pan; Zhou, Jie; Gao, Lei; Ding, Ruijun

    2013-10-01

    HgCdTe electron injection avalanche photodiodes (e-APDs) work at linear mode. A weak optical current signal is amplified orders of magnitude due to the internal avalanche mechanism and it has been demonstrated to be one of the most promising methods to focal-plane arrays (FPAs) for low-flux like hyper-spectral imaging and high-speed applications such as active imaging. This paper presents the design of a column-shared ADC for cooled e-APDs FPA. Designing a digital FPA requires fulfilling very stringent requirements in terms of power consumption, silicon area and speed. Among the various ADC architectures sigma-delta conversion is a promising solution for high-performance and medium size FPA such as 128×128. The performance of Sigma-delta ADC rather relies on the modulator structure which set over-sampling and noise shaping characteristics than on critical analog circuits. This makes them quite robust and flexible. A multistage noise shaping (MASH) 2-1 single bit architecture sigma-delta conversion with switched-capacitor circuits is designed for column-shared ADC, which is implanted in the GLOBALFOUNDRIES 0.35um CMOS process with 4-poly and 4-metal on the basis of a 100um pixel pitch. It operates under 3.3V supply and the output range of the quantizer is 2V. A quantization noise subtraction circuit in modulator is designed to subtract the quantization noise of first-stage modulator. The quantization noise of the modulator is shaped by a high-pass filter. The silicon area and power consumption are mainly determined by the decimation low pass filter. A cascaded integrator-comb (CIC) filter is designed as the digital decimator filter. CIC filter requires no multipliers and use limited storage thereby leading to more economical hardware implementation. The register word length of the filter in each stage is carefully dimensioned in order to minimize the required hardware. Furthermore, the digital filters operate with a reduced supply voltage to 1.5V. Simulation

  18. Persisting impact of historical mining activity to metal (Pb, Zn, Cd, Tl, Hg) and metalloid (As, Sb) enrichment in sediments of the Gardon River, Southern France.

    PubMed

    Resongles, Eléonore; Casiot, Corinne; Freydier, Rémi; Dezileau, Laurent; Viers, Jérôme; Elbaz-Poulichet, Françoise

    2014-05-15

    In this study, we assessed past and present influence of ancient mining activity on metal(loid) enrichment in sediments of a former mining watershed (Gardon River, SE France), that is now industrialized and urbanized. A sedimentary archive and current sediments were characterized combining geochemical analyses, zinc isotopic analyses and sequential extractions. The archive was used to establish local geochemical background and recorded (i) increasing enrichment factors (EFs) for Pb, Zn, Cd, Tl, Hg, As and Sb throughout the industrial era, (ii) a contamination peak in 1976 attributed to a tailings dam failure, and (iii) current levels in 2002 and 2011 similar to those of 1969, except for Sb and Hg, reflecting a persisting contamination pattern. Inter-element relationships and spatial distribution of EF values of current sediments throughout the watershed suggested that both ancient and current contamination had a common origin for Pb, Zn, Cd, Tl and As related to the exploitation of Pb/Zn mineralization while old Sb mines and coal extraction area were the main sources for Sb and Hg respectively. This prevailing mining origin was reflected for Zn by a relatively uniform isotopic composition at δ(66)Zn=0.23 ± 0.03‰, although slight decrease from 0.23‰ to 0.18‰ was recorded from upstream to downstream sites along the river course in relation with the contribution of the lighter δ(66)Zn signature (~0.08‰) of acid mine drainage impacted tributaries. Results from sequential extractions revealed that the potential mobility of the studied metal(loid)s varied in the order SbCd, with an increase of the mobile pool for Cd, Pb, Zn and to a lesser extent for As and Tl associated to increased enrichment. Altogether, these results tend to demonstrate that ancient mining activity still contributes to metal enrichment in the sediments of the Gardon River and that some of these metals may be mobilized toward the water compartment.

  19. Toxicity of Hg, Cu, Cd, and Cr on early developmental stages of Ciona intestinalis (Chordata, Ascidiacea) with potential application in marine water quality assessment.

    PubMed

    Bellas, J; Vázquez, E; Beiras, R

    2001-08-01

    The toxicity of mercury, copper, cadmium and chromium on sperm viability, fertilisation, embryogenesis and larval attachment of Ciona intestinalis was examined. Fertilisation rate (FR) showed a small decrease even at the highest metal concentration tested. The median effective concentrations (EC50) reducing rates of embryogenesis and larval attachment by 50% were 54 microg Hg/l (0.27 microM), 46 microg Cu/l (0.72 microM), 838 microg Cd/l (7.46 microM), 10,318 microg Cr/l (198 microM), and 35 microg Hg/l (0.18 microM), 34 microg Cu/l (0.54 microM) and 11,755 microg Cr/l (226 microM), respectively. Therefore, Hg is three times more toxic than Cu (on a molar basis), ca. 30 times more toxic than Cd and ca. 1000 times more toxic than Cr to early stages of C. intestinalis. Rates of larval attachment and embryogenesis were the most sensitive endpoints, although the latter is more advisable for routine assessment of seawater quality because of its greater simplicity. In addition to bivalves and sea-urchins, ascidian embryos can provide biological criteria for seawater quality standards taking into account the sensitivity of a chordate and contributing to the detection of harmful chemicals with no marked effect on the species currently in use in seawater quality bioassays.

  20. Optimization of simultaneous electrochemical determination of Cd(II), Pb(II), Cu(II) and Hg(II) at carbon nanotube-modified graphite electrodes.

    PubMed

    Pikna, L'ubomír; Heželová, Mária; Kováčová, Zuzana

    2015-01-01

    The health of the environment is worsening every day. Monitoring of potentially toxic elements and remediation of environmental pollution are necessary. Therefore, the research and development of simple, inexpensive, portable and effective sensors is important. Electrochemistry is a useful component of the field of environment monitoring. The present study focuses on evaluating and comparing three types of electrodes (PIGE, PIGE/MWCNT/HNO3 and PIGE/MWCNT/EDTA/HNO3) employed for the simultaneous electrochemical determination of four potentially toxic elements: Cd(II), Pb(II), Cu(II) and Hg(II). Cyclic voltammograms were measured in an acetate buffer. The LOD, LOQ, the standard and relative precisions of the method and a prediction intervals were calculated (according to the technical procedure DIN 32 645) for the three electrodes and for each measured element. The LOD for PIGE/CNT/HNO3 (the electrode with narrowest calculated prediction intervals) was 2.98 × 10(-7) mol L(-1) for Cd(II), 4.83 × 10(-7) mol L(-1) for Pb(II), 3.81 × 10(-7) mol L(-1) for Cu(II), 6.79 × 10(-7) mol L(-1) for Hg(II). One of the benefits of this study was the determination of the amount of Hg(II) in the mixture of other elements.

  1. Photocatalytic activity of CdS and Ag2S quantum dots deposited on poly(amidoamine) functionalized carbon nanotubes

    PubMed Central

    Neelgund, Gururaj M.; Oki, Aderemi

    2011-01-01

    Two novel ternary nanocatalysts, f-MWCNTs-CdS and f-MWCNTs-Ag2S were successfully constructed by covalent grafting of fourth generation (G4) hyperbranched, crosslinked poly(amidoamine) (PAMAM) to carboxylated multi-walled carbon nanotubes (MWCNTs-COOH) and subsequent deposition of CdS or Ag2S quantum dots (QDs). The structural transformation, surface potential, and morphology of functionalized MWCNTs (f-MWCNTs) and nanocatalysts were characterized by UV-vis spectrophotometer, Fourier transform infrared spectroscopy, powder X-ray diffraction, Raman spectroscopy, thermogravimetric analysis, scanning electron microscopy and energy dispersive spectroscopy. Transmission electron microscopy reveals the effective anchoring of QDs on f-MWCNTs. The catalytic activity of nanocatalysts was evaluated by photodegradation of methyl orange under illumination of UV light. The coupling of MWCNTs, PAMAM and CdS or Ag2S QDs significantly enhanced the catalytic efficiency of nanocatalysts. The rate constants for degradation of methyl orange in presence of nanocatalysts were calculated using the Langmuir-Hinshelwood model. Overall, the excellence in photodegradation was accomplished by hybridizing f-MWCNTs with CdS or Ag2S PMID:22267895

  2. Band bending at Al, In, Ag, and Pt interfaces with CdTe and ZnTe (110)

    SciTech Connect

    Wahi, A.K.; Miyano, K.; Carey, G.P.; Chiang, T.T.; Lindau, I.; Spicer, W.E. )

    1990-05-01

    Band bending behavior and interfacial chemistry for Al, In, Ag, and Pt overlayers on vacuum-cleaved {ital p}-CdTe and {ital p}-ZnTe (110) have been studied using ultraviolet photoelectron spectroscopy (UPS) and x-ray photoelectron spectroscopy (XPS). These metals provide a range of metal--substrate reactivities: Al reacts strongly with Te, Ag moderately, and In minimally, with no evidence seen for In reaction on ZnTe. Pt exhibits strong alloying behavior with both Cd and Zn. All four metals are found to yield Schottky barriers on CdTe and ZnTe, with a narrow range of final Fermi level positions, {ital E}{sub {ital fi}}={ital E}{sub {ital f}}{minus}{ital E}{sub VBM}, observed on CdTe, from 0.9 to 1.05{plus minus}0.1 eV, and on ZnTe from 0.65 to 1.0{plus minus}0.1 eV. The prediction of the MIGS model that a difference in barrier height exists for two semiconductors dependent upon their band lineup (valence band offset) is examined and found to agree with experiment for Ag, Pt, and Al, but not for In. For the highly reactive Al, no evidence for the overlayer metallicity required for metal-induced gap states (MIGS) to operate is seen on CdTe or ZnTe until after band bending has stabilized. Reaction and intermixing for Al, Ag, and Pt overlayers on CdTe and ZnTe indicate these interfaces are not ideal. The possible role of defects at these four metal/CdTe and metal/ZnTe interfaces is considered, and provides a consistent explanation for the final Fermi level positions observed.

  3. Thermal stability of Ag, Al, Sn, Pb, and Hg films reinforced by 2D (C, Si) crystals and the formation of interfacial fluid states in them upon heating. MD experiment

    NASA Astrophysics Data System (ADS)

    Polukhin, V. A.; Kurbanova, E. D.

    2016-02-01

    Molecular dynamics simulation is used to study the thermal stability of the interfacial states of metallic Al, Ag, Sn, Pb, and Hg films (i.e., the structural elements of superconductor composites and conducting electrodes) reinforced by 2D graphene and silicene crystals upon heating up to disordering and to analyze the formation of nonautonomous fluid pseudophases in interfaces. The effect of perforation defects in reinforcing 2D-C and 2D-Si planes with passivated edge covalent bonds on the atomic dynamics is investigated. As compared to Al and Ag, the diffusion coefficients in Pd and Hg films increase monotonically with temperature during thermally activated disordering processes, the interatomic distances decrease, the sizes decrease, drops form, and their density profile grows along the normal. The coagulation of Pb and Hg drops is accompanied by a decrease in the contact angle, the reduction of the interface contact with graphene, and the enhancement of its corrugation (waviness).

  4. Synthesis and properties of new CdSe-AgI-As{sub 2}Se{sub 3} chalcogenide glasses

    SciTech Connect

    Kassem, M.; Le Coq, D.; Fourmentin, M.; Hindle, F.; Bokova, M.; Cuisset, A.; Masselin, P.; Bychkov, E.

    2011-02-15

    Research highlights: {yields} Determination of the glass-forming region in the pseudo-ternary CdSe-AgI-As{sub 2}Se{sub 3} system. {yields} Characterization of macroscopic properties of the new CdSe-AgI-As{sub 2}Se{sub 3} glasses. {yields} Far infrared transmission of chalcogenide glasses. {yields} Characterization of the total conductivity of CdSe-AgI-As{sub 2}Se{sub 3} glasses. -- Abstract: The glass-forming region in the pseudo-ternary CdSe-AgI-As{sub 2}Se{sub 3} system was determined. Measurements including differential scanning calorimetry (DSC), density, and X-ray diffraction were performed. The effect resulting from the addition of CdSe or AgI has been highlighted by examining three series of different base glasses. The characteristic temperatures of the glass samples, including glass transition (T{sub g}), crystallisation (T{sub x}), and melting (T{sub m}) temperatures are reported and used to calculate their {Delta}T = T{sub x} - T{sub g} and their Hruby, H{sub r} = (T{sub x} - T{sub g})/(T{sub m} - T{sub x}), criteria. Evolution of the total electrical conductivity {sigma} and the room temperature conductivity {sigma}{sub 298} was also studied. The terahertz transparency domain in the 50-600 cm{sup -1} region was pointed for different chalcogenide glasses (ChGs) and the potential of the THz spectroscopy was suggested to obtain structural information on ChGs.

  5. A HgCdTe detector/FPA/sensor model for evaluation of VLWIR to SWIR sensors with an assessment of SWIR sensors for strategic and tactical missions

    NASA Astrophysics Data System (ADS)

    Richwine, Robert; Balcerak, Raymond; Freyvogel, Ken; Sood, Ashok

    2006-08-01

    This model was developed to provide a means for comparative assessments of HgCdTe FPA's and sensors operating in the infrared spectral bands that coincide with the atmospheric windows - (SW1(1.5-1.8μ), SW2(2-2.5μ), MW(3-5μ), and LW(8-12μ). As a true imaging model it also functions as an assessment tool for single-band imagery and for multi-color imagery. The HgCdTe model characterizes both n-on-p and p-on-n homojunctions and heterostructures. Diffusion and depletion dark currents and RoA's are calculated for the three common configurations (mesa heterojunction, planar ionimplanted or diffused junction, and the vertically integrated photodiode). The model places the specified FPA into an optical system, evaluates system performance (NEI, NETD, MRTD, and SNR) and creates two-point corrected imagery complete with 3D noise image effects. This model was exercised here as a predictive tool for performance of state-of-the- art detector arrays in optical systems in the four spectral bands (atmospheric windows) from the SW to the MW (1.5- 1.8, 2.0-2.5, 3.4-4.2 and 4.5-5.0 um) which are the bands commonly considered for hot target and plume exhaust detection. Results from the literature and model runs for various target and scene sets show promise for HgCdTe FPA's and sensors developed for the 2-2.5 μm band for a variety of missions such as threat detection from UAV or satellite platforms, perimeter defense, and high-altitude intercepts.

  6. Thermal Studies of Zn(II), Cd(II) and Hg(II) Complexes of Some N-Alkyl-N-Phenyl-Dithiocarbamates

    PubMed Central

    Onwudiwe, Damian C.; Ajibade, Peter A.

    2012-01-01

    The thermal decomposition of Zn(II), Cd(II) and Hg(II) complexes of N-ethyl-N-phenyl and N-butyl-N-phenyl dithiocarbamates have been studied using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The products of the decomposition, at two different temperatures, were further characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The results show that while the zinc and cadmium complexes undergo decomposition to form metal sulphides, and further undergo oxidation forming metal oxides as final products, the mercury complexes gave unstable volatiles as the final product. PMID:22949811

  7. Development of the HgCdTe Avalanche Photodiode Detectors and the Improvement in the CO2 Lidar Performance for the ASCENDS Mission

    NASA Astrophysics Data System (ADS)

    Sun, X.; Abshire, J. B.; Chen, J. R.; Ramanathan, A. K.; Mao, J.

    2015-12-01

    NASA Goddard Space Flight Center (GSFC) is developing the CO2 lidar as a candidate for the NASA's planned ASCENDS mission under the support of Earth Science Technology Office (ESTO) IIP and ATI-QRS programs. A new type of HgCdTe avalanche photodiode (APD) detector has been developed by the DRS Technologies under the IIP program. The new detectors achieved >70% quantum efficiency, including the effect of the fill factor, over the spectral range from 0.4 to 4.3 μm, which significantly improves the receiver performance of our CO2 lidar and enabled other remote sending measurements. The HgCdTe APD arrays have 80 μm square pixels in a 4x4 array along with a bank of 16 preamplifiers on the same chip carrier. Test results at both DRS and GSFC showed the HgCdTe APD array has achieved, an APD gain of 500-1000, 8-10 MHz electrical bandwidth, and an average noise equivalent power (NEP) of <0.5 fW/Hz1/2. It has demonstrated at least a 3 orders of magnitude dynamic range at a fixed APD gain setting. The gains of the APD and the preamplifier can also be adjusted to further extend the receiver dynamic range. During summer 2014 we successfully demonstrated airborne lidar measurements of column CO2 using one of these detectors. The Aerospace Corporation is currently building a 3U CubeSat with one of these detectors in a small closed-cycle cryocooler as the primary payload under the ESTO In-space Validation of Earth Science Technology (InVEST) program. The CubeSat is scheduled to be launched in late 2016 and will fly in a low Earth orbit and monitor the performance for at least a year. We have also updated the performance analysis of a space-based version of our CO2 lidar with the new HgCdTe APD detector. For the retrievals, a least-square-error method is used to fit the measured transmittances to a predetermined line shape function using 8 to 16 sampling wavelengths. The error in the derived total optical depth and the CO2 mixing ratio are estimated via the standard error

  8. Mid-Wave HgCdTe FPA Based on P on N Technology: HOT Recent Developments. NETD: Dark Current and 1/f Noise Considerations

    NASA Astrophysics Data System (ADS)

    Kerlain, A.; Brunner, A.; Sam-Giao, D.; Pére-Laperne, N.; Rubaldo, L.; Destefanis, V.; Rochette, F.; Cervera, C.

    2016-09-01

    For high operating temperature applications, variation of noise equivalent differential temperature (NETD or NEDT) with temperature is the most relevant figure of merit. NETD(T) models with and without taking into account systemic 1/f noise contribution are presented and compared to recent developments made on P on N technology at Sofradir and CEA-LETI. We show that for mature middle wave infrared HgCdTe technology, no 1/f noise contribution up to 220 K is measured and the focal plane array operation is only limited by the mean performance value degradation, not by an increase of defects.

  9. Near-surface variband layers with small composition gradient as factors for the effective increase in photoresponsivity of an infrared HgCdTe photoconductive device (photoresistor)

    NASA Astrophysics Data System (ADS)

    Drugova, Albina A.; Kholodnov, Vyacheslav A.

    1999-06-01

    It is shown that near-surface variband layers can afford the maximally possible photomodulation of conductivity of CdHgTe n-type samples for 8 - 12 and 3 - 5 micron light wavelengths. The photomodulation efficiency will be identical to that for absence of surface recombination. This is caused by the shaping of such photocarrier distribution which inhibits photocarrier diffusion to the surfaces even under small variband fields Evar. Therefore the number of defects in the variband layers can be decrease significantly at the cost of decrease in the gradient of mole composition of these layers.

  10. A model for the trap-assisted tunneling mechanism in diffused n-p and implanted n(+)-p HgCdTe photodiodes

    NASA Technical Reports Server (NTRS)

    Rosenfeld, David; Bahir, Gad

    1992-01-01

    This paper presents a theoretical model for the trap-assisted tunneling process in diffused n-on-p and implanted n(+)-on-p HgCdTe photodiodes. The model describes the connection between the leakage current associated with the traps and the trap characteristics: concentration, energy level, and capture cross sections. It is observed that the above two types of diodes differ the voltage dependence of the trap-assisted tunneling current and dynamic resistance. The model takes this difference into account and offers an explanation of the phenomenon. The good fit between measured and calculated dc characteristics of the photodiodes supports the validity of the model.

  11. Photophysical and photochemical aspects of coupled semiconductors. Charge-transfer processes in colloidal CdS-TiO sub 2 and CdS-AgI systems

    SciTech Connect

    Gopidas, K.R.; Bohorquez, M.; Kamat, P.V. )

    1990-08-09

    The mechanistic and kinetic details of the charge injection from excited CdS into a large bandgap semiconductor such as AgI and TiO{sub 2} have been investigated by coupling the two semiconductor systems in the colloidal form. The interaction between the two colloids led to the quenching of CdS emission. The rate constants for the charge injection from excited CdS into the conduction band of AgI and TiO{sub 2} colloids were determined to be 2.2 {times} 10{sup 7} and >5 {times} 10{sup 10} s{sup {minus}1}, respectively. Transmission electron microscopic analysis indicated the possibility of several CdS colloidal particles interacting with a single particle of TiO{sub 2} and participating in the charge injection process. Primary photochemical events in the CdS-TiO{sub 2} system were investigated by picosecond laser flash photolysis. The charge injected into the TiO{sub 2} colloid and trapped at the Ti{sup 4+} site was characterized from its broad absorption in the region of 500-760 nm. The extended lifetime of these trapped charge carriers indicated an improved charge separation in the coupled semiconductor system.

  12. Scanning laser microscopy of reactive ion etching induced n-type conversion in vacancy-doped p-type HgCdTe

    NASA Astrophysics Data System (ADS)

    Siliquini, J. F.; Dell, J. M.; Musca, C. A.; Faraone, L.

    1997-06-01

    Laser-beam-induced-current measurements have been used to characterize the extent of reactive ion etching (RIE) induced type conversion in vacancy-doped p-type Hg0.69Cdoverflow="scroll">0.31Te. The technique allows the spatial extent of RIE induced type conversion to be determined and the donor level concentration profile within the n-type converted region to be estimated. For the RIE processing conditions used (410 mT, CH4/Hoverflow="scroll">2, 0.4 W/cm2) and an etch depth of 0.2 μm, n-type conversion extending ˜1.5 μm into the semiconductor was observed. The simple and powerful approach developed in this work is of general application to the study of semiconductor junctions, and can be applied to a range of processing techniques used in the formation of p-n junctions in HgCdTe (e.g., epitaxially grown heterojunctions, ion implantation, ion milling and Hg in-diffusion).

  13. Determination of As, Cd, Pb, and Hg in urine using inductively coupled plasma mass spectrometry with the direct injection high efficiency nebulizer

    NASA Astrophysics Data System (ADS)

    Minnich, Michael G.; Miller, Derek C.; Parsons, Patrick J.

    2008-03-01

    The application of the large-bore direct injection high efficiency nebulizer (LB-DIHEN) for the determination of arsenic (As), cadmium (Cd), lead (Pb), and mercury (Hg) in urine by inductively coupled plasma mass spectrometry (ICP-MS) is described. The LB-DIHEN is compared with the standard method using a concentric pneumatic nebulizer and cyclonic spray chamber. In addition to the toxicological significance of As, Cd, Pb, and Hg, these elements represent a cross-section of analytical issues including spectral interferences (e.g., 40Ar 35Cl + on 75As + and 98Mo 16O + on 114Cd +) and memory effects (Hg). In this study, the low sample consumption of the LB-DIHEN is used to reduce the volume of urine needed for analysis, and to reduce the volume of final diluted sample required for analysis. Eliminating the spray chamber and reducing the dead volume of the nebulizer reduces memory effects, especially for analytes such as Hg. The Dynamic Reaction Cell (DRC) is used in this study to attenuate the background level of ArCl + in spite of the increase in the solvent load and, in turn, the urine matrix (chloride) delivered to the plasma by the LB-DIHEN. This is the first report on coupling the LB-DIHEN to a standard autosampler for unattended sample analysis. The robustness of direct injection nebulization for routine analysis and the issues associated with automation of the sample introduction process are discussed. Although the figures of merit (sensitivity, limit of detection, and precision) determined for both nebulizers are slightly poorer for the LB-DIHEN than for the concentric pneumatic nebulizer, there is not a clinically significant difference between the results for both sample introduction systems. The accuracy of results is assessed using archived urine materials that are circulated by several different proficiency testing (PT) programs and external quality assessment schemes (EQAS). Results obtained using the LB-DIHEN were within the acceptable range

  14. Highly Sensitive and Selective In-Situ SERS Detection of Pb2+, Hg2+, and Cd2+ Using Nanoporous Membrane Functionalized with CNTs

    PubMed Central

    Shaban, Mohamed; Galaly, A. R.

    2016-01-01

    Porous Anodic Alumina (PAA) membrane was functionalized with CoFe2O4 nanoparticles and used as a substrate for the growing of very long helical-structured Carbon Nanotubes (CNTs) with a diameter less than 20 nm. The structures and morphologies of the fabricated nanostructures were characterized by field emission- scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX), and Raman spectroscopy. By uploading the CNTs on PAA, the characteristic Raman peaks of CNTs and PAA showed 4 and 3 times enhancement, respectively, which leads to more sensitive Surface-Enhanced Raman Spectroscopy (SERS) substrates. For comparison, PAA and CNTs/PAA arrays were used as SERS substrates for the detection of Hg2+, Cd2+, and Pb2+. The proposed sensor demonstrated high sensitivity and selectivity between these heavy metal ions. CNTs/PAA sensor showed excellent selectivity toward Pb2+ over other metal ions, where the enhancement factor is decreased from ~17 for Pb2+ to ~12 for Hg2+ and to ~4 for Cd2+. Therefore, the proposed CNTs/PAA sensor can be used as a powerful tool for the determination of heavy metal ions in aqueous solutions. PMID:27143512

  15. Influence of High-Power Pulsed IR Laser Radiation on the Electrophysical Properties of Cd x Hg1- x Те Heteroepitaxial Layers

    NASA Astrophysics Data System (ADS)

    Talipov, N. Kh.

    2013-05-01

    Results of investigations into the electrophysical properties of p- and n-type Cd x Hg1- x Te heteroepitaxial layers grown by molecular beam and liquid phase epitaxy methods after exposure to high-power pulsed IR radiation of solid-state Nd3+:YAG and chemical DF lasers at wavelengths of 1.06 and 3.8-4.2 μm, respectively, are presented. It is demonstrated that the main types of defects resulting from pulsed irradiation are mercury vacancies that play the role of acceptors in this material. The spatial distribution of generated mercury vacancies depends on the intensity and wavelength of laser radiation: the defects generated by pulses of the Nd3+:YAG laser are concentrated only near the surface, whereas DF-laser radiation creates defects in the entire volume of the heteroepitaxial structures. It is established that irradiation with the Nd3+:YAG laser of the p-Cd x Hg1- x Te heteroepitaxial layers implanted by boron ions leads to the activation of implanted boron atoms as a result of melting and recrystallization of the irradiated surface layer.

  16. Toxic elements (As, Se, Cd, Hg, Pb) and their mineral and technogenic formations in the snow cover in the vicinity of the industrial enterprises of Tomsk

    NASA Astrophysics Data System (ADS)

    Talovskaya, A. V.; Filimonenko, E. A.; Osipova, N. A.; Lyapina, E. E.; azikov, E. G. Y.

    2014-08-01

    Snow samples were collected in four industrial areas of Tomsk where brickworks, factories for the production of reinforced concrete structures, machine repair industries and local boilers, petrochemical plant and thermal power station are located. Study of insoluble fraction of aerosols in snow and melted snow water was performed to determine the contents of the emissions from these facilities. The insoluble fraction of aerosols in snow is aerosol particles deposited on snow cover. As, Se, Cd, Hg, Pb concentration was analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Mineral modes of the elements were determined by scanning electron microscope. It was found the snow cover is mainly polluted by As, Se, Cd, Hg, Pb in the thermal power station impact area, by As - in the brickworks impact area, by Se - in the impact area of densely located factories for the production of reinforced concrete structures, machine repair industries and local boilers. The research results show that the mineral modes of As are associated with arsenopyrite, of Pb - with galena in the insoluble fraction of aerosols in snow.

  17. Simultaneous spectrophotometric determination of Cu2+, Hg2+, and Cd2+ ions using 2-(3-hydroxy-1-methylbut-2-enylideneamino)pyridine-3-ol.

    PubMed

    Tarighat, Maryam Abbasi; Mohammadi, Khosro

    2015-04-01

    New complexes of Cu2+, Hg2+, and Cd2+ with a recently synthesized Schiff base derived from 2-(3-hydroxy-1-methylbut-2-enylideneamino)pyridine-3-ol were applied for their simultaneous determination with artificial neural networks. A new analytical method using principal component-feed forward neural networks (PC-FFNNs) and principal component-radial basis function networks (PC-RBFNs) was used. Spectral data was reduced using principal component analysis and subjected to ANNs. The data obtained from synthetic mixtures of metal ions were processed by PC-FFNNs and PC-RBFNs. Performances of the proposed methods were tested with regard to relative standard error of prediction. Limit of detections and limit of quantifications were determined. The results obtained by PC-FFNNs and PC-RBFNs were compared to each other. Under the working conditions, the proposed methods were successfully applied to simultaneous determination of Hg2+, Cu2+, and Cd2+ in different water and soil samples. Concentrations of metal ions in the samples were also determined by flame atomic absorption spectrometry (FAAS) and standard addition method. The amounts of metal ions obtained by the proposed methods were in good agreement with those obtained by FAAS and standard addition method. PMID:25792026

  18. The influence of the magnetic field on the effect of drag of electrons by phonons in n-Cd{sub x}Hg{sub 1-x}Te

    SciTech Connect

    Aliyev, S. A.; Zulfigarov, E. I.; Selim-Zade, R. I.; Agayev, Z. F.

    2009-09-15

    Thermopower in n-Cd{sub 0.2}Hg{sub 0.8}Te (6-100 K) is studied. A large effect of drag of the charge carriers by phonons {alpha}{sub ph} is found. The influence of the magnetic field H on the drag thermopower is considered. It is established that the magnetic field exerts the effect mainly on the electron component of {alpha}{sub ph}. The data are interpreted in the context of the theory taking into account the effect of H on thermopower {alpha}{sub ph}, in which parameter A({epsilon}) proportional to the static force of the drag effect is introduced. By the experimental data {alpha}{sub ph}(T, H), T, and H dependences A({epsilon}) are determined. It is shown that, as H increases, A({epsilon}) sharply decreases. This explains a decrease in {alpha}{sub ph} in the magnetic field, power index k in dependence {alpha}{sub ph} {proportional_to} T{sup -}{kappa}, and narrowing the region of manifestation of the drag effect. It is established that at classically high fields, the drag effect in n-Cd{sub 0.2}Hg{sub 0.8}Te does not vanish.

  19. Active three-dimensional and thermal imaging with a 30-μm pitch 320×256 HgCdTe avalanche photodiode focal plane array

    NASA Astrophysics Data System (ADS)

    de Borniol, Eric; Rothman, Johan; Guellec, Fabrice; Vojetta, Gautier; Destéfanis, Gérard; Pacaud, Olivier

    2012-06-01

    Three-dimensional (3-D) flash light detection and ranging (LADAR) imaging is based on time of flight (TOF) measurement of a single laser pulse. The laser pulse coming back from the observed object will be detected only if the number of photons received by each pixel generates a signal greater than the pixel noise. In order to extract this weak photonic signal from the noise we use the high gain and low excess noise of the HgCdTe avalanche photodiode (APD) arrays developed at CEA/LETI. The sensor consists of a 30-μm pitch APD detector array hybridized to a 320×256 pixels ROIC for passive and active imaging. In passive mode the focal plane array behaves like a thermal imager and we measured 30 mK of noise-equivalent temperature difference. In active imaging mode, each pixel sensed the time of flight and the intensity two-dimensional (2-D) of a single laser pulse. Laboratory tests show a range noise of 11 cm for 4300 photoelectrons per pixel and detection limit under 100 photoelectrons. The sensor was also used during a field trial to record 2-D and 3-D real-time videos. The quality of the images obtained demonstrates the maturity of HgCdTe-APD-array technology.

  20. Toxicity and Traces of Hg, Pb and Cd in the Hepatopancreas, Gills and Muscles of Perna viridis from Jakarta Bay, Indonesia.

    PubMed

    Irnidayanti, Y

    2015-02-01

    Heavy metals contamination on the coast of Jakarta Bay has led to the level of pollution and can cause toxicity to organisms living in the sea, i.e., green mussels. Green mussels have the ability to detoxify metals entering their bodies. Their ability to accumulate metals is higher than other aquatic animals. This is due to their sedentary life which prevents them from avoiding the effects of pollution and their high tolerance to certain metals. The high concentration of metal content would be toxic to the cell because metal ions can act as oxidants and bind to organic and protein molecules. The results of the study showed that traces of heavy metals were detected in the hepatopancreas, gills, muscles and gonads organs of the mussels living in the waters of Muara Angke. Lead (Pb) and cadmium (Cd) were found in all four organs, while mercury (Hg) was not detected in the muscles. Traces of Hg and Cd were not detected in hepatopancreas, gills, muscles and gonads of green mussels in Panimbang, while Pb was detected by 0.00 1 in the male gonads and 0.01 in hepatopancreas. The concentration of Pb in the male gonads are still below the acceptable limit and concentration of Pb in the hepatopancreas is relatively equivalent to the acceptable limit. Metal detection in the organs above shows that the Muara Angke waters tend to be polluted and have an impact on the mussels weight loss as a result of heavy metal toxicity.

  1. The role of localized junction leakage in the temperature-dependent laser-beam-induced current spectra for HgCdTe infrared focal plane array photodiodes

    SciTech Connect

    Feng, A. L.; Li, G. E-mail: xschen@mail.sitp.ac.cn; He, G.; Sun, Z. Q.; Hu, W. D.; Chen, X. S. E-mail: xschen@mail.sitp.ac.cn; Yin, F.; Zhang, B.; Lu, W.

    2013-11-07

    We have performed the study on the dependence of laser beam induced current (LBIC) spectra on the temperature for the vacancy-doped molecular beam epitaxy grown Hg{sub 1−x}Cd{sub x}Te (x = 0.31) photodiodes by both experiment and numerical simulations. It is found that the measured LBIC signal has different distributions for different temperature extents. The LBIC profile tends to be more asymmetric with increasing temperature below 170 K. But the LBIC profile becomes more symmetric with increasing temperature above 170 K. Based on a localized leakage model, it is indicated that the localized junction leakage can lead to asymmetric LBIC signal, in good agreement with the experimental data. The reason is that the trap-assisted tunneling current is the dominant leakage current at the cryogenic temperature below 170 K while the diffusion current component becomes dominant above the temperature of 170 K. The results are helpful for us to better clarify the mechanism of the dependence of LBIC spectra on temperature for the applications of HgCdTe infrared photodiodes.

  2. A versatile and highly sensitive probe for Hg(II), Pb(II) and Cd(II) detection individually and totally in water samples.

    PubMed

    Zhou, Yu; Tian, Xiang-Li; Li, Yan-Song; Zhang, Yuan-Yuan; Yang, Li; Zhang, Jun-Hui; Wang, Xin-Rui; Lu, Shi-Ying; Ren, Hong-Lin; Liu, Zeng-Shan

    2011-12-15

    The detection of heavy metal ions using enzyme-linked immunosorbent assays (ELISA) has been reported by several research groups. However, highly sensitive and selective detection of total heavy metal ions using ELISA is a major technical limitation. Here we describe the development of a versatile and highly sensitive probe combining goat anti-mice IgG, colloidal gold nanoparticles (AuNPs) and horseradish peroxidase (HRP). We demonstrate the utility of this probe using three kinds of heavy metal complete antigens and three monoclonal antibodies (McAbs) in one ELISA system to establish a high-throughput screening protocol. The procedure was successfully applied to analysis of Hg(II), Pb(II) and Cd(II) individually and totally from different water samples. The sensitivities for the detection of Hg(II), Pb(II) and Cd(II) individually and totally are 27.4, 3.9, 15.8 and 18.2 nM, respectively. And all limit of detection (LODs) are lower than 1.2 nM. The recovery results obtained from the developed technique showed a good correlation (R(2)=0.983) with those from ICP-MS. The major advantage of the probe is the versatility and high sensibility. The probe could be potentially used, upon demand, as a sensitive and versatile detector for a broad range of applications. PMID:21975341

  3. Specific features of the spectra and relaxation kinetics of long-wavelength photoconductivity in narrow-gap HgCdTe epitaxial films and heterostructures with quantum wells

    SciTech Connect

    Rumyantsev, V. V. Ikonnikov, A. V.; Antonov, A. V.; Morozov, S. V.; Zholudev, M. S.; Spirin, K. E.; Gavrilenko, V. I.; Dvoretskii, S. A.; Mikhailov, N. N.

    2013-11-15

    The spectra and relaxation kinetics of interband photoconductivity are investigated in narrow-gap Hg{sub 1-x}Cd{sub x}Te epitaxial films with x = 0.19-0.23 and in structures with HgCdTe-based quantum wells (QWs), having an interband-transition energy in the range of 30-90 meV, grown by molecular-beam epitaxy on GaAs (013) substrates. A long-wavelength sensitivity band caused by impurities or defects is found in the spectra of the structures with quantum wells in addition to the interband photoconductivity. It is shown that the lifetimes of nonequilibrium carriers in the structures with QWs is less than in bulk samples at the same optical-transition energy. From the measured carrier lifetimes, the ampere-watt responsivity and the equivalent noise power for a film with x = 0.19 at a wavelength of 19 {mu}m are estimated. When investigating the relaxation kinetics of the photoconductivity at 4.2 K in high excitation regime, it is revealed that radiative recombination is dominant over other mechanisms of nonequilibrium-carrier recombination.

  4. Highly Sensitive and Selective In-Situ SERS Detection of Pb2+, Hg2+, and Cd2+ Using Nanoporous Membrane Functionalized with CNTs

    NASA Astrophysics Data System (ADS)

    Shaban, Mohamed; Galaly, A. R.

    2016-05-01

    Porous Anodic Alumina (PAA) membrane was functionalized with CoFe2O4 nanoparticles and used as a substrate for the growing of very long helical-structured Carbon Nanotubes (CNTs) with a diameter less than 20 nm. The structures and morphologies of the fabricated nanostructures were characterized by field emission- scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX), and Raman spectroscopy. By uploading the CNTs on PAA, the characteristic Raman peaks of CNTs and PAA showed 4 and 3 times enhancement, respectively, which leads to more sensitive Surface-Enhanced Raman Spectroscopy (SERS) substrates. For comparison, PAA and CNTs/PAA arrays were used as SERS substrates for the detection of Hg2+, Cd2+, and Pb2+. The proposed sensor demonstrated high sensitivity and selectivity between these heavy metal ions. CNTs/PAA sensor showed excellent selectivity toward Pb2+ over other metal ions, where the enhancement factor is decreased from ~17 for Pb2+ to ~12 for Hg2+ and to ~4 for Cd2+. Therefore, the proposed CNTs/PAA sensor can be used as a powerful tool for the determination of heavy metal ions in aqueous solutions.

  5. Spectroscopic, and electrochemical studies of [MCl2(η2-N,N-dpksc)] (M = Zn, Cd, Hg and dpksc = di-2-pyridylketone semicarbazone)

    NASA Astrophysics Data System (ADS)

    Bakir, Mohammed; McDermot, Covel; Johnson, Toni

    2013-05-01

    A series of group 12 metal chlorides of dpksc of the type [MCl2(η2-N,N-dpksc)] (M = Zn, Cd and Hg) were synthesized from the reactions between MCl2 and dpksc in refluxing CH3CN. Spectroscopic measurements performed on protophilic solutions of [MCl2(η2-N,N-dpksc)] divulged sensitivity of [MCl2(η2-N,N-dpksc)] to changes in their surroundings. Variable temperature 1H NMR studies revealed the amine protons to be more sensitive to temperature variations compared to the amide and aromatic protons. Electronic absorption spectral measurements disclosed acid-base inter-conversion between [MCl2(η2-N,N-dpksc)] and its conjugate base [MCl2(η2-N,N-dpksc-H)]-. In dmf, the acidity of [MCl2(η2-N,N-dpksc)] increases in the following order: [ZnCl2(η2-N,N-dpksc)] > [CdCl2(η2-N,N-dpksc)] > [HgCl2(η2-N,N-dpksc)]. The electrochemical properties of [MCl2(η2-N,N-dpksc)] are dominated by a series of irreversible redox transformations pointing to electrochemical decomposition of [MCl2(η2-N,N-dpksc)] upon electronic transfers.

  6. Simultaneous spectrophotometric determination of Cu2+, Hg2+, and Cd2+ ions using 2-(3-hydroxy-1-methylbut-2-enylideneamino)pyridine-3-ol.

    PubMed

    Tarighat, Maryam Abbasi; Mohammadi, Khosro

    2015-04-01

    New complexes of Cu2+, Hg2+, and Cd2+ with a recently synthesized Schiff base derived from 2-(3-hydroxy-1-methylbut-2-enylideneamino)pyridine-3-ol were applied for their simultaneous determination with artificial neural networks. A new analytical method using principal component-feed forward neural networks (PC-FFNNs) and principal component-radial basis function networks (PC-RBFNs) was used. Spectral data was reduced using principal component analysis and subjected to ANNs. The data obtained from synthetic mixtures of metal ions were processed by PC-FFNNs and PC-RBFNs. Performances of the proposed methods were tested with regard to relative standard error of prediction. Limit of detections and limit of quantifications were determined. The results obtained by PC-FFNNs and PC-RBFNs were compared to each other. Under the working conditions, the proposed methods were successfully applied to simultaneous determination of Hg2+, Cu2+, and Cd2+ in different water and soil samples. Concentrations of metal ions in the samples were also determined by flame atomic absorption spectrometry (FAAS) and standard addition method. The amounts of metal ions obtained by the proposed methods were in good agreement with those obtained by FAAS and standard addition method.

  7. Study of LWIR and VLWIR Focal Plane Array Developments: Comparison Between p-on- n and Different n-on- p Technologies on LPE HgCdTe

    NASA Astrophysics Data System (ADS)

    Gravrand, O.; Mollard, L.; Largeron, C.; Baier, N.; Deborniol, E.; Chorier, Ph.

    2009-08-01

    The very long infrared wavelength (>14 μm) is a very challenging range for the design of mercury cadmium telluride (HgCdTe) large focal plane arrays (FPAs). The need (mainly expressed by the space industry) for very long wave FPAs appears very difficult to fulfil. High homogeneity, low defect rate, high quantum efficiency, low dark current, and low excess noise are required. Indeed, for such wavelength, the corresponding HgCdTe gap becomes smaller than 100 meV and each step from the metallurgy to the technology becomes critical. This paper aims at presenting a status of long and very long wave FPAs developments at DEFIR (LETI-LIR/Sofradir joint venture). This study will focus on results obtained in our laboratory for three different ion implanted technologies: n-on- p mercury vacancies doped technology, n-on- p extrinsic doped technology, and p-on- n arsenic on indium technology. Special focus is given to 15 μm cutoff n/ p FPA fabricated in our laboratory demonstrating high uniformity, diffusion and shot noise limited photodiodes at 50 K.

  8. Characterization of leakage current mechanisms in long wavelength infrared HgCdTe photodiodes from a study of current-voltage characteristics under low illumination

    NASA Astrophysics Data System (ADS)

    Gopal, Vishnu; Hu, Weida

    2015-12-01

    This paper presents an improved method to characterize the current-voltage (I-V) characteristics of a HgCdTe photodiode under low illumination. Such characteristics exhibit relatively small but finite zero-bias minority carrier current. The open circuit voltage of the diode is generally small and remains un-noticed due to inappropriate measurement conditions. These characteristics are often mistaken as the dark characteristics of the diode. It is shown here that these kinds of lowly illuminated characteristics may be characterized by using a recently proposed model to analyze the illuminated I-V characteristics that make use of experimentally observed photo-current due to illumination and the resulting open circuit voltage in modelling the current characteristics of the photodiode. An example of long-wavelength HgCdTe diode's I-V characteristics under low illumination that was previously analyzed as dark characteristics is discussed here to illustrate the improved method and to further emphasize the importance of taking into account the influence of illumination on the current characteristics while investigating the leakage currents in infrared photodiodes. Our results show that, by taking into account the effect of illumination, the agreement between the theory and experiment has significantly improved.

  9. Small two-dimensional arrays of mid-wavelength infrared HgCdTe diodes fabricated by reactive ion etching-induced p-to-n-type conversion

    NASA Astrophysics Data System (ADS)

    Antoszewski, J.; Musca, C. A.; Dell, J. M.; Faraone, L.

    2003-07-01

    The reactive ion etching (RIE) technique has been shown to produce high-performance n-on-p junctions by localized-type conversion of p-type mid-wavelength infrared (MWIR) HgCdTe material. This paper presents variable area analysis of n-on-p HgCdTe test diodes and data on two-dimensional (2-D) arrays fabricated by RIE. All devices were fabricated on x = 0.30 to 0.31 liquid-phase epitaxy (LPE) grown p-type (p = ˜1 × 1016 cm-3) HgCdTe wafers obtained from Fermionics Corp. The diameter of the circular test diodes varied from 50 µm to 600 µm. The 8 × 8 arrays comprised of 50 µm × 50 µm devices on a 100-µm pitch, and all devices were passivated with 5000 Å of thermally deposited CdTe. At temperatures >145 K, all devices are diffusion limited; at lower temperatures, generation-recombination (G-R) current dominates. At the lowest measurement temperature (77 K), the onset of tunneling can be observed. At 77 K, the value of 1/R0A for large devices shows quadratic dependence on the junction perimeter/area ratio (P/A), indicating the effect of surface leakage current at the junction perimeter, and gives an extracted bulk value for R0A of 2.8 × 107 Ω cm2. The 1/R0A versus P/A at 195 K exhibits the well-known linear dependence that extrapolates to a bulk value for R0A of 17.5 Ω cm2. Measurements at 77 K on the small 8 × 8 test arrays were found to demonstrate very good uniformity with an average R0A = 1.9 × 106 Ω cm2 with 0° field of view and D* = 2.7 × 1011cm Hz1/2/W with 60° field of view looking at 300 K background.

  10. Efficient visible-light photocatalytic activity by band alignment in mesoporous ternary polyoxometalate-Ag2S-CdS semiconductors

    NASA Astrophysics Data System (ADS)

    Kornarakis, I.; Lykakis, I. N.; Vordos, N.; Armatas, G. S.

    2014-07-01

    Porous multicomponent semiconductor materials show improved photocatalytic performance due to the large and accessible pore surface area and high charge separation efficiency. Here we report the synthesis of well-ordered porous polyoxometalate (POM)-Ag2S-CdS hybrid mesostructures featuring a controllable composition and high photocatalytic activity via a two-step hard-templating and topotactic ion-exchange chemical process. Ag2S compounds and polyoxometalate cluster anions with different reduction potentials, such as PW12O403-, SiW12O404- and PMo12O403-, were employed as electron acceptors in these ternary heterojunction photocatalysts. Characterization by small-angle X-ray scattering, X-ray diffraction, transmission electron microscopy and N2 physisorption measurements showed hexagonal arrays of POM-Ag2S-CdS hybrid nanorods with large internal BET surface areas and uniform mesopores. The Keggin structure of the incorporated POM clusters was also verified by elemental X-ray spectroscopy microanalysis, infrared and diffuse-reflectance ultraviolet-visible spectroscopy. These new porous materials were implemented as visible-light-driven photocatalysts, displaying exceptional high activity in aerobic oxidation of various para-substituted benzyl alcohols to the corresponding carbonyl compounds. Our experiments show that the spatial separation of photogenerated electrons and holes at CdS through the potential gradient along the CdS-Ag2S-POM interfaces is responsible for the increased photocatalytic activity.Porous multicomponent semiconductor materials show improved photocatalytic performance due to the large and accessible pore surface area and high charge separation efficiency. Here we report the synthesis of well-ordered porous polyoxometalate (POM)-Ag2S-CdS hybrid mesostructures featuring a controllable composition and high photocatalytic activity via a two-step hard-templating and topotactic ion-exchange chemical process. Ag2S compounds and polyoxometalate cluster

  11. Testing WHAM-FTOX with laboratory toxicity data for mixtures of metals (Cu, Zn, Cd, Ag, Pb).

    PubMed

    Tipping, Edward; Lofts, Stephen

    2015-04-01

    The Windermere humic aqueous model using the toxicity function (WHAM-FTOX ) describes cation toxicity to aquatic organisms in terms of 1) accumulation by the organism of metabolically active protons and metals at reversible binding sites, and 2) differing toxic potencies of the bound cations. Cation accumulation (νi , in mol g(-1) ) is estimated through calculations with the WHAM chemical speciation model by assuming that organism binding sites can be represented by those of humic acid. Toxicity coefficients (αi ) are combined with νi to obtain the variable FTOX (= Σ αi νi ) which, between lower and upper thresholds (FTOX,LT , FTOX,UT ), is linearly related to toxic effect. Values of αi , FTOX,LT , and FTOX,LT are obtained by fitting toxicity data. Reasonable fits (72% of variance in toxic effect explained overall) were obtained for 4 large metal mixture acute toxicity experiments involving daphnids (Cu, Zn, Cd), lettuce (Cu, Zn, Ag), and trout (Zn, Cd, Pb). Strong nonadditive effects, most apparent in results for tests involving Cd, could be explained approximately by purely chemical competition for metal accumulation. Tentative interpretation of parameter values obtained from these and other experimental data suggests the following order of bound cation toxicity: H < Al < (Cu Zn Pb UO2 ) < (Cd Ag). Another trend is a strong increase in Cd toxicity relative to that of Zn as organism complexity increases (from bacteria to fish).

  12. Frequency of SNP -336A/G in the promoter region of CD209 in a population from northeastern Brazil.

    PubMed

    Costa, P N; Ferreira-Fernandes, H; de Oliveira, J S; Pereira, A C T C; Pinto, G R; Ferreira, G P

    2015-08-14

    Dendritic cells (DCs) mediate the initiation of the immune response against a variety of pathogens. The DC-SIGN receptor is encoded by the gene CD209 and is expressed on the surface of DCs. It binds to mannose-rich carbohydrates and enables the recognition of bacteria, fungi, parasites, and viruses. SNP -336A/G in the promoter region of CD209 influences the expression of the DC-SIGN receptor. Several studies have associated this SNP with an increased susceptibility to infectious diseases and the development of more severe forms of disease. Therefore, the aim of this study was to determine the prevalence of SNP -336A/G in a population from northeastern Brazil. We analyzed 181 individuals from the general population of Parnaíba, Piauí, Brazil, of which 37% were men and 63% were women. SNP -336A/G was detected by polymerase chain reaction and treatment with the restriction enzyme MscI and visualized by electrophoresis on an 8% polyacrylamide gel stained with silver nitrate. Of the individuals analyzed, 116 (64.1%) were homozygous AA, 57 (31.5%) were heterozygous (AG), and 8 (4.4%) were homozygous GG. The allele frequency of -336G was 20.2%. Genotype frequencies were in Hardy-Weinberg equilibrium. To the best of our knowledge, this is the first report to describe the frequency of the CD209 SNP -336A/G in a population in the State of Piauí. Further studies are needed to determine the relationship between this SNP and the vulnerability of this population to major infectious diseases.

  13. Encapsulation of Ln(III) ions/Ag nanoparticles within Cd(ii) boron imidazolate frameworks for tuning luminescence emission.

    PubMed

    Liu, Min; Chen, Shumei; Wen, Tian; Zhang, Jian

    2016-06-30

    Two Cd(ii) boron imidazolate frameworks (/) with different topologies have been synthesized by the targeted assembly of aromatic carboxylate, tetradentate imidazolate ligands, possessing tunable luminescence emission properties. Hydroxy-functional neutral shows an obvious blue shift of luminescence after loading Ag nanoparticles (NPs) while the first reported anionic in the BIF system with blue emission can tune the white-light emission via doping mixed Ln(3+) in an appropriate ratio (Ln = Eu and Tb). PMID:27321108

  14. Bioleaching mechanism of Zn, Pb, In, Ag, Cd and As from Pb/Zn smelting slag by autotrophic bacteria.

    PubMed

    Wang, Jia; Huang, Qifei; Li, Ting; Xin, Baoping; Chen, Shi; Guo, Xingming; Liu, Changhao; Li, Yuping

    2015-08-15

    A few studies have focused on release of valuable/toxic metals from Pb/Zn smelting slag by heterotrophic bioleaching using expensive yeast extract as an energy source. The high leaching cost greatly limits the practical potential of the method. In this work, autotrophic bioleaching using cheap sulfur or/and pyrite as energy matter was firstly applied to tackle the smelting slag and the bioleaching mechanisms were explained. The results indicated autotrophic bioleaching can solubilize valuable/toxic metals from slag, yielding maximum extraction efficiencies of 90% for Zn, 86% for Cd and 71% for In, although the extraction efficiencies of Pb, As and Ag were poor. The bioleaching performance of Zn, Cd and Pb was independent of leaching system, and leaching mechanism was acid dissolution. A maximum efficiency of 25% for As was achieved by acid dissolution in sulfursulfur oxidizing bacteria (S-SOB), but the formation of FeAsO4 reduced extraction efficiency in mixed energy source - mixed culture (MS-MC). Combined works of acid dissolution and Fe(3+) oxidation in MS-MC was responsible for the highest extraction efficiency of 71% for In. Ag was present in the slag as refractory AgPb4(AsO4)3 and AgFe2S3, so extraction did not occur.

  15. Effect of a boron implantation on the electrical properties of epitaxial HgCdTe with different material composition

    NASA Astrophysics Data System (ADS)

    Lyapunov, D. V.; Pishchagin, A. A.; Grigoryev, D. V.; Korotaev, A. G.; Voitsekhovskii, A. V.; Kokhanenko, A. P.; Iznin, I. I.; Savytskyy, H. V.; Bonchik, A. U.; Dvoretskii, S. A.; Mikhailov, N. N.

    2016-08-01

    In this work the experimental results of investigations of the dynamics of accumulation and spatial distribution of electrically active radiation defects when irradiating epitaxial films of Hg1-xCdxTe (MCT) with different material composition (x). The films, grown by molecular beam epitaxy (MBE) were irradiated by B ions at room temperature in the radiation dose range 1012 -1015 ions/cm2 and with ion energy 100 keV. The results give the differences in implantation profiles, damage accumulation and electrical properties as a function of the material composition of the films.

  16. New planar process for implementation of p-on-n HgCdTe heterostructure infrared photodectors

    NASA Astrophysics Data System (ADS)

    Bahir, Gad; Garber, Valery; Dust, Arie

    2003-01-01

    We report on a new, simple process to fabricate planar Hg1-xCdyTe/Hg1-xCdxTe heterostructure photodiodes with p-on-n configuration. The material used for this demonstration was a double-layer p-on-n heterostructure that was grown by a liquid-phase-epitaxy technique. The p-on-n planar devices consisted of an arsenic-doped p-type cap epilayer on top of a long-wavelength IR n-type active epilayer. The ion-beam-miling p-type conversion effect was used to delineate the active device element, and to isolate the planar device. Detailed analysis of the current characteristics of these diodes as a funciton of temperatuer, show that they have high performance, and that their dark current is diffusion-limited down to 60 K. The results show that over a wide range of cut-off wavelengths, the RoA product values are close to the theoretical limit. Light Beam Induced Current technique was used to characterize the lateral and vertical dimensions of the ion beam milling induced junction. Electro-optic properties of a 2D array of small diodes with a 40-μm pitch are presented, and demonstrate the potential of the new process for implementation of 2D arrays.

  17. Effects of morphology, diameter and periodic distance of the Ag nanoparticle periodic arrays on the enhancement of the plasmonic field absorption in the CdSe quantum dots

    NASA Astrophysics Data System (ADS)

    Kohnehpoushi, Saman; Eskandari, Mehdi; Ahmadi, Vahid; Yousefirad, Mansooreh; Nabavi, Elham

    2016-09-01

    In this work, the numerical calculations of plasmonic field absorption of Ag nanoparticles (Ag NPs) periodic arrays in the CdSe quantum dot (QD) film are investigated by the three-dimensional finite difference time domain (FDTD). Diameter (D), periodic distance (P), and morphology effects of Ag NPs are investigated on the improvement of the plasmonic field absorption in CdSe QD film. Results show that plasmonic field absorption in CdSe QD film is enhanced with reduction of D of Ag NPs until 5 nm and reduces thereafter. It is observed that with raising D of Ag NPs, optimum plasmonic field absorption in CdSe QD film is shifted toward the higher P. Moreover, with varying morphology of Ag NPs from spherical to cylindrical, cubic, ringing and pyramid, the plasmonic field absorption is considerably enhanced in CdSe QD film and position of quadrupole plasmon mode (QPPM) is shifted toward further wavelength. For cylindrical Ag NPs, the QPPM intensity increased with raising height (H) until 15 nm and reduces thereafter.

  18. Synthesis, characterization and evaluation of the photocatalytic performance of Ag-CdMoO{sub 4} solar light driven plasmonic photocatalyst

    SciTech Connect

    Adhikari, Rajesh; Malla, Shova; Gyawali, Gobinda; Sekino, Tohru; Lee, Soo Wohn

    2013-09-01

    Graphical abstract: - Highlights: • Ag-CdMoO{sub 4} solar light driven photocatalyst was successfully synthesized. • Photocatalyst exhibited strong absorption in the visible region. • Photocatalytic activity was significantly enhanced. • Enhanced activity was caused by the SPR effect induced by Ag nanoparticles. - Abstract: Ag-CdMoO{sub 4} plasmonic photocatalyst was synthesized in ethanol/water mixture by photo assisted co-precipitation method at room temperature. As synthesized powders were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) surface area analyzer. Photocatalytic activity was evaluated by performing the degradation experiment over methylene blue (MB) and indigo carmine (IC) as model dyes under simulated solar light irradiation. The results revealed that the Ag-CdMoO{sub 4} showed the higher photocatalytic performance as compared to CdMoO{sub 4} nanoparticles. Dispersion of Ag nanoparticles over the surface of CdMoO{sub 4} nanoparticles causes the surface plasmon resonance (SPR) and enhances the broad absorption in the entire visible region of the solar spectrum. Hence, dispersion of Ag nanoparticles over CdMoO{sub 4} nanoparticles could be the better alternative to enhance the absorption of visible light by scheelite crystal family for effective photocatalysis.

  19. Structural features of AgCaCdMg{sub 2}(PO{sub 4}){sub 3} and AgCd{sub 2}Mg{sub 2}(PO{sub 4}){sub 3}, two new compounds with the alluaudite-type structure, and their catalytic activity in butan-2-ol conversion

    SciTech Connect

    Kacimi, Mohammed; Ziyad, Mahfoud; Hatert, Frederic . E-mail: fhatert@ulg.ac.be

    2005-04-20

    AgCaCdMg{sub 2}(PO{sub 4}){sub 3} and AgCd{sub 2}Mg{sub 2}(PO{sub 4}){sub 3}, two new compounds with the alluaudite-type structure, were synthesized by a solid state reaction in air at 750 deg. C. The X-ray powder diffraction pattern of AgCaCdMg{sub 2}(PO{sub 4}){sub 3} indicates the presence of small amounts of (Ca, Mg){sub 3}(PO{sub 4}){sub 2} with the whitlockite structure, as impurity, whereas AgCd{sub 2}Mg{sub 2}(PO{sub 4}){sub 3} is constituted by pure alluaudite. The Rietveld refinements of the X-ray powder diffraction patterns indicate an ordered cationic distribution for AgCd{sub 2}Mg{sub 2}(PO{sub 4}){sub 3}, with Ag on A(2)', Cd on A(1) and M(1), and Mg on M(2), whereas a disordered distribution of Cd and Ca between the A(1) and M(1) sites is observed for AgCaCdMg{sub 2}(PO{sub 4}){sub 3}. The catalytic properties of these compounds has been measured in reaction of butan-2-ol dehydrogenation. In the absence of oxygen, both samples exhibit poor dehydrogenation activity. All samples displayed no dehydration activity. Introduction of oxygen into the feed changed totally the catalytic behavior of the catalysts. The production of methyl ethyl ketone increases with time on stream and the reaction temperature. AgCaCdMg{sub 2}(PO{sub 4}){sub 3} is more efficient than AgCd{sub 2}Mg{sub 2}(PO{sub 4}){sub 3}.

  20. White-light-exciting, layer-by-layer-assembled ZnCdHgSe quantum dots/polymerized ionic liquid hybrid film for highly sensitive photoelectrochemical immunosensing of neuron specific enolase.

    PubMed

    Yu, Xiangyang; Wang, Yanying; Chen, Xuemin; Wu, Kangbing; Chen, Danchao; Ma, Ming; Huang, Zhenjia; Wu, Wangze; Li, Chunya

    2015-04-21

    ZnCdHgSe quantum dots (QDs) functionalized with N-acetyl-l-cysteine were synthesized and characterized. Through layer-by-layer assembling, the ZnCdHgSe QDs was integrated with a polymerized 1-decyl-3-[3-pyrrole-1-yl-propyl]imidazolium tetrafluoroborate (PDPIT) ionic liquid film modified indium tin oxide (ITO) electrode to fabricated a photoelectrochemical interface for the immobilization of rabbit antihuman neuron specific enolase (anti-NSE). After being treated with glutaraldehyde vapor and bovine serum albumin successively, an anti-NSE/ZnCdHgSe QDs/PDPIT/ITO sensing platform was established. Simplely using a white-light LED as an excitation source, the immunoassay of neuron specific enolase (NSE) was achieved through monitoring the photocurrent variation. The polymerized ionic liquid film was demonstrated to be an important element to enhance the photocurrent response of ZnCdHgSe QDs. The anti-NSE/ZnCdHgSe QDs/PDPIT/ITO based immunosensor presents excellent performances in neuron specific enolase determination. The photocurrent variation before and after being interacted with NSE exhibits a good linear relationship with the logarithm of its concentration (log cNSE) in the range from 1.0 pg mL(-1) to 100 ng mL(-1). The limit of detection of this immunosensor is able to reach 0.2 pg mL(-1) (S/N = 3). The determination of NSE in clinical human sera was also demonstrated using anti-NSE/ZnCdHgSe QDs/PDPIT/ITO electrode. The results were found comparable with those obtained by using enzyme-linked immunosorbent assay method. PMID:25790014

  1. Distribution and accumulation of Cd, Cu, Hg, Pb and Zn in the surface sediments of El Tobari Lagoon, central-East Gulf of California: An ecosystem associated with agriculture and aquaculture activities.

    PubMed

    Jara-Marini, M E; Tapia-Alcaraz, J N; Dumer-Gutiérrez, J A; García-Rico, L; García-Hernández, J; Páez-Osuna, F

    2013-01-01

    The purpose of this research is to provide a comprehensive assessment of the concentration levels and spatial variability of cadmium (Cd), copper (Cu), mercury (Hg), lead (Pb) and zinc (Zn) in El Tobari Lagoon in surface sediments during two seasons for several geochemical variables that could explain the observed heavy metal variability. Seventy-two surface sediments samples were collected in 12 different sites of the El Tobari Lagoon. Sediment samples were dried and subjected to acid extraction using a microwave system and five metals (Cd, Cu, Hg, Pb and Zn) were measured using atomic adsorption spectrometry. A certificate sediment material and blanks were used as quality control purposes. The enrichment factor (EF) and the index of geoaccumulation (Igeo) were calculated as index of metals contamination for the sediments, using aluminum as the conservative element. The five metals examined in sediments from El Tobari Lagoon exhibited a linear correlation with Al as result of the large specific surface areas of these sediment components and the chemical affinities between them. The metals contents in sites of the El Tobari Lagoon were variable, and Cd, Cu and Hg presented a seasonal behavior. The enrichment factor and index of geoaccumulation analysis indicated that Cd and Hg exhibited a certain extent (EF for Cd ranged from 4.10 to 10.29; EF for Hg ranged from 2.77 to 12.89) of anthropogenic pollution, while Cu showed sporadic (EF ranged from 0.43 to 2.54) anthropogenic contamination. The highest concentrations of Cd, Cu and Hg were found in the sites that regularly received discharge effluents from agriculture and aquaculture.

  2. Numerical Modeling of SRH and Tunneling Mechanisms in High-Operating-Temperature MWIR HgCdTe Photodetectors

    NASA Astrophysics Data System (ADS)

    Vallone, Marco; Mandurrino, Marco; Goano, Michele; Bertazzi, Francesco; Ghione, Giovanni; Schirmacher, Wilhelm; Hanna, Stefan; Figgemeier, Heinrich

    2015-09-01

    A combined experimental and numerical simulation study is presented on two sets of nominally identical single-color back-illuminated midwave-infrared n-on- p photodetectors grown by liquid-phase epitaxy, p-doped with Hg vacancies and with Au, respectively. The present numerical model includes a novel formulation for band-to-band tunneling, which overcomes the intrinsic limitations of the classical Kane description without introducing numerical issues typical of other approaches. Our study confirms that adopting n-on- p architectures, avoiding metal vacancy doping, and reducing the acceptor density in the absorber region are prerequisites for obtaining high-operating-temperature photodetectors. A significant contribution to the dark current in both sets of devices is attributed to impact ionization, crucial to obtain a satisfactory explanation for the measured characteristics also at low to intermediate bias.

  3. High-Temperature Vaporization Behavior of Oxides II. Oxides of Be, Mg, Ca, Sr, Ba, B, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Zn, Cd, and Hg

    NASA Astrophysics Data System (ADS)

    Lamoreaux, R. H.; Hildenbrand, D. L.; Brewer, L.

    1987-07-01

    In order to assess the high-temperature vaporization behavior and equilibrium gas phase compositions over the condensed oxides of Be, Mg, Ca, Sr, Ba, B, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Zn, Cd, and Hg, the relevant thermodynamic and molecular constant data have been compiled and critically evaluated. Selected values of the Gibbs energy functions of condensed and vapor phases are given in the form of equations valid over wide temperature ranges, along with the standard entropies and enthalpies of formation. These data were used to generate plots of equilibrium partial pressures of vapor species as functions of temperature for representative environmental conditions ranging from reducing to oxidizing. The calculated partial pressures and compositions agree, for the most part, with experimental results obtained under comparable conditions. Maximum vaporization rates have been calculated using the Hertz-Knudsen equation. Literature references are given.

  4. Zn(II), Cd(II) and Hg(I) complexes of cinnamic acid: FT-IR, FT-Raman, 1H and 13C NMR studies

    NASA Astrophysics Data System (ADS)

    Kalinowska, M.; Świsłocka, R.; Lewandowski, W.

    2011-05-01

    The effect of zinc, cadmium(II) and mercury(I) ions on the electronic structure of cinnamic acid (phenylacrylic acid) was studied. In this research many miscellaneous analytical methods, which complement one another, were used: infrared (FT-IR), Raman (FT-Raman), nuclear magnetic resonance ( 1H, 13C NMR) and quantum mechanical calculations. The spectroscopic studies provide some knowledge on the distribution of the electronic charge in molecule, the delocalization energy of π-electrons and the reactivity of metal complexes. In the series of Zn(II) → Cd(II) → Hg(I) cinnamates: (1) systematic shifts of several bands in the experimental and theoretical IR and Raman spectra and (2) regular chemical shifts for protons 1H and 13C nuclei were observed.

  5. Low-temperature anomalies of the photoelectromagnetic effect in p-Cd{sub x}Hg{sub 1-x}Te due to recharging of surface states

    SciTech Connect

    Gassan-zade, S. G. Strikha, M. V.; Shepelsky, G. A.

    2008-04-15

    A number of anomalies inexplicable in the context of available theoretical models are observed in the photoelectromagnetic effect in p-Cd{sub x}Hg{sub 1-x}Te crystals. A general model of the photoelectromagnetic effect in semiconductors with a large ratio between the mobilities of electrons and holes is developed, taking into account the influence of space charge. The model allows the interpretation of all experimentally observed anomalies of the photoelectromagnetic effect, including the double sign inversion in magnetic field. Comparison of the theory with the experiment makes it possible to determine the parameters of the material. It is suggested that the space charge responsible for the anomalies of the photoelectromagnetic effect is associated with a high concentration of specific surface states ({approx}10{sup 13} cm{sup -3}) recharged when trapping nonequilibrium charge carriers.

  6. Development of high-speed, low-noise NIR HgCdTe avalanche photodiode arrays for adaptive optics and interferometry

    NASA Astrophysics Data System (ADS)

    Finger, Gert; Baker, Ian; Dorn, Reinhold; Eschbaumer, Siegfried; Ives, Derek; Mehrgan, Leander; Meyer, Manfred; Stegmeier, Jörg

    2010-07-01

    The most promising way to overcome the CMOS noise barrier of infrared AO sensors is the amplification of the photoelectron signal directly at the point of absorption inside the infrared pixel by means of the avalanche gain. HgCdTe eAPD arrays with cut off wavelengths of λc ~2.64 μm produced by SELEX-Galileo have been evaluated at ESO. The arrays were hybridized to an existing non-optimized ROIC developed for laser gated imaging which has a format of 320×256 pixels and four parallel video outputs. The avalanche gain makes it possible to reduce the read noise to < 7 e rms. The dark current requirements of IR wavefront sensing are also met.

  7. Reactive ion etching (RIE) induced p- to n-type conversion in extrinsically doped p-type HgCdTe

    SciTech Connect

    Musca, C.A.; Smith, E.P.G.; Siliquini, J.F.; Dell, J.M.; Antoszewski, J.; Faraone, L.; Piotrowski, J.

    1998-12-31

    Mercury annealing of reactive ion etching (RIE) induced p- to n-type conversion in extrinsically doped p-type epitaxial layers of HgCdTe (x = 0.31) has been used to reconvert n-type conversion sustained during RIE processing. For the RIE processing conditions used (400 mT, CH{sub 4}/H{sub 2}, 90 W) p- to n-type conversion was observed using laser beam induced current (LBIC) measurements. After a sealed tube mercury anneal at 200 C for 17 hours, LBIC measurements clearly indicated no n-type converted region remained. Subsequent Hall measurements confirmed that the material consisted of a p-type layer, with electrical properties equivalent to that of the initial as-grown wafer (N{sub A}-N{sub D} = 2 {times} 10{sup 16} cm{sup {minus}3}, {mu} = 350 cm{sup 2}.V{sup {minus}1}.s{sup {minus}1}).

  8. A model for the trap-assisted tunneling mechanism in diffused n-p and implanted n(+)-p HgCdTe photodiodes

    NASA Technical Reports Server (NTRS)

    Rosenfeld, David; Bahir, Gad

    1992-01-01

    A theoretical model for the trap-assisted tunneling process in diffused n-on-p and implanted n(+)-on-p HgCdTe photodiodes is presented. The model describes the traps and the trap characteristics: concentration, energy level, and capture cross sections. We have observed that the above two types of diodes differ in the voltage dependence of the trap-assisted tunneling current and dynamic resistance. Our model takes this difference into account and offers an explanation of the phenomenon. The good fit between measured and calculated DC characteristics of the photodiodes (for medium and high reverse bias and for temperatures from 65 to 140 K) supports the validity of the model.

  9. Preparation and photoelectrochemistry of p-HgIn/sub 2/Te/sub 4/ and p- and n-CdIn/sub 2/Te/sub 2/

    SciTech Connect

    Becker, R.S.; Zhou, G.D.; Elton, J.

    1986-10-23

    The photoelectrochemical properties of the two p-type title semiconductors were examined in several redox solutions for the first time. For p-HgIn/sub 2/Te/sub 4/, the quantum efficiency for carrier collection (phi/sub c/) is 94% at short circuit, and the monochromatic and polychromatic power efficiencies calculated from the three electrode cell experiments are 9.5% and 3%, respectively, in iron(III) triethanolamine solution with comparably high values in (Cr(III)EDTA)/sup -/. The flat-band potential (V/sub fb/) is at -0.70 V (vs. SCE) in the former two couples, and indirect and direct gap transitions exist at 0.88 and 1.04 eV, respectively. Stability studies indicate essentially 100% stability to photocorrosion in Fe(III)TEA. For p-CdIn/sub 2/Te/sub 4/, phi/sub c/ is also high at short circuit (91%) and the monochromatic power efficiency is even higher (11%) than for p-HgIn/sub 2/Te/sub 4/ while the polychromatic value is somewhat lower (2%); both calculated from three electrode cell experiments. The V/sub fb/ is at approximately -0.5V (vs. SCE), and both an indirect (1.16 eV) and a direct transition exist (1.24 eV). Data for both semiconductors in a polysulfide solution indicate considerably poorer PEC characteristics than for the other redox solutions.

  10. Elastic and optoelectronic properties of RbMF3 (M=Zn, Cd, Hg): A mBJ density functional calculation

    NASA Astrophysics Data System (ADS)

    Murtaza, G.; Hayatullah; Khenata, R.; Khalid, M. N.; Naeem, S.

    2013-02-01

    Bonding nature as well as the structural, elastic, electronic and optical properties of cubic fluoroperovskites RbMF3 (M=Zn, Cd and Hg) compounds have been calculated using a full-potential augmented plane (FPLAPW) method within the density functional theory. The exchange-correlation potential was treated with the generalized gradient approximation of Wu and Cohen (WC-GGA) to calculate the total energy. Moreover, the modified Becke-Johnson potential (TB-mBJ) was also applied for the electronic and optical properties. It is found that lattice constant increases while bulk modulus decreases with the change of cation (M) in going from Zn to Hg in RbMF3 in accordance with the experimental results. The calculations of the electronic band structure, density of states and charge density show that these compounds have an indirect energy band gap (M-Г) with a mixed ionic and covalent bonding. The optical properties (namely: the absorption coefficient and the reflectivity) were calculated for radiation up to 45.0 eV.

  11. Protection associated with a TB vaccine is linked to increased frequency of Ag85A-specific CD4(+) T cells but no increase in avidity for Ag85A.

    PubMed

    Metcalfe, Hannah J; Steinbach, Sabine; Jones, Gareth J; Connelley, Tim; Morrison, W Ivan; Vordermeier, Martin; Villarreal-Ramos, Bernardo

    2016-08-31

    There is a need to improve the efficacy of Bacille Calmette-Guérin (BCG) vaccination against tuberculosis in humans and cattle. Previously, we found boosting BCG-primed cows with recombinant human type 5 adenovirus expressing antigen 85A (Ad5-85A) increased protection against Mycobacterium bovis infection compared to BCG vaccination alone. The aim of this study was to decipher aspects of the immune response associated with this enhanced protection. We compared BCG-primed Ad5-85A-boosted cattle with BCG-vaccinated cattle. Polyclonal CD4(+) T cell libraries were generated from pre-boost and post-boost peripheral blood mononuclear cells - using a method adapted from Geiger et al. (2009) - and screened for antigen 85A (Ag85A) specificity. Ag85A-specific CD4(+) T cell lines were analysed for their avidity for Ag85A and their Ag85A epitope specificity was defined. Boosting BCG with Ad5-85A increased the frequencies of post-boost Ag85A-specific CD4(+) T cells which correlated with protection (reduced pathology). Boosting Ag85A-specific CD4(+) T cell responses did not increase their avidity. The epitope specificity was variable between animals and we found no clear evidence for a post-boost epitope spreading. In conclusion, the protection associated with boosting BCG with Ad5-85A is linked with increased frequencies of Ag85A-specific CD4(+) T cells without increasing avidity or widening of the Ag85A-specific CD4(+) T cell repertoire.

  12. 4482 Element Multispectral Hybrid PV/PC HgCdTe IRFPA for High Resolution Coverage of 3.7 - 15.4 Micrometers for the AIRS Instrument

    NASA Technical Reports Server (NTRS)

    Rutter, James; Libonate, Scott; Denley, Brian; Gurnee, Mark N.; Robillard, Gene

    1996-01-01

    The Atmospheric Infrared Sounder (AIRS) is a key facility instrument in the NASA Earth Observing System (EOS) program, being implemented to obtain comprehensive long-term measurements of earth processes affecting global change. The instrument performs passive IR remote sensing using a high resolution grating spectrometer with a wide spectral coverage (3.7 - 15.4 m) directing radiation onto a hybrid HgCdTe IRFPA operating at 58K in a vacuum package cooled to 155K. The hybrid HgCdTe FPA consists of twelve modules, 10 with multiplexed photovoltaic detectors and two with individually leaded out photoconductive detectors. The complex FPA has a large optical footprint, 53 mm x 66 mm, and receives energy dispersed from the grating through a precision filter assembly containing 17 narrow band filters. The backside illuminated PV detector arrays are fabricated from P-on-n double layer LPE grown heterojunction detectors in a bilinear format of 50 m x 100 m detectors, with from 232 to 420 detectors per module. For the MWIR bands four PV modules cover the 3.7 m to 8.22 m region. Low detector capacitance and low noise preamplifiers in the ROIC are key to achieving high sensitivities in these bands. Uniform quantum efficiencies and detectivities exceeding 3E13 cm-rtHz/W have been achieved. The LWIR region is covered by six PV modules spanning 8.8 m to 13.75 m. High detector resistance and very low ROIC preamplifier input noise are key to achieving high sensitivity. A detectivity exceeding 2E11 cm-rtHz/W has been achieved at the longest wavelength. Two additional PC modules cover the longest spectral bands out to 15.4 m. This high performance multispectral focal plane has been built and integrated with the dewar assembly, and is currently being integrated with the complete AIRS sensor.

  13. Latest developments of 10μm pitch HgCdTe diode array from the legacy to the extrinsic technology

    NASA Astrophysics Data System (ADS)

    Péré-Laperne, Nicolas; Berthoz, Jocelyn; Taalat, Rachid; Rubaldo, Laurent; Kerlain, Alexandre; Carrère, Emmanuel; Dargent, Loïc.

    2016-05-01

    Sofradir recently presented Daphnis, its latest 10 μm pitch product family. Both Daphnis XGA and HD720 are 10μm pitch mid-wave infrared focal plane array. Development of small pixel pitch is opening the way to very compact products with a high spatial resolution. This new product is taking part in the HOT technology competition allowing reductions in size, weight and power of the overall package. This paper presents the recent developments achieved at Sofradir to make the 10μm pitch HgCdTe focal plane array based on the legacy technology. Electrical and electro-optical characterizations are presented to define the appropriate design of 10μm pitch diode array. The technological tradeoffs are explained to lower the dark current, to keep high quantum efficiency with a high operability above 110K, F/4. Also, Sofradir recently achieved outstanding Modulation Transfer Function (MTF) demonstration at this pixel pitch, which clearly demonstrates the benefit to users of adopting 10μm pixel pitch focal plane array based detectors. Furthermore, the HgCdTe technology has demonstrated an increase of the operating temperature, plus 40K, moving from the legacy to the P-on-n one at a 15μm pitch in mid-wave band. The first realizations using the extrinsic P-on-n technology and the characterizations of diodes with a 10μm pitch neighborhood will be presented in both mid-wave and long-wave bands.

  14. Optical transitions in Cd{sub x}Hg{sub 1-x}Te-based quantum wells and their analysis with account for the actual band structure of the material

    SciTech Connect

    Bazhenov, N. L. Shilyaev, A. V.; Mynbaev, K. D.; Zegrya, G. G.

    2012-06-15

    Quantum-confinement levels in a Cd{sub x}Hg{sub 1-x}Te-based rectangular quantum well are calculated in the framework of the four-band Kane model taking into account mixing between the states of electrons and three types of holes (heavy, light, and spin-split holes). Comparison of the calculation results with experimental data on the photoluminescence of Cd{sub x}Hg{sub 1-x}Te-based quantum wells suggests that optical transitions involving the conduction and light-hole bands are possibly observed in the spectra.

  15. Effect of adherent bacteria and bacterial extracellular polymers upon assimilation by Macoma balthica of sediment-bound Cd, Zn and Ag

    USGS Publications Warehouse

    Harvey, Ronald W.; Luoma, Samuel N.

    1985-01-01

    Effects of adherent bacteria and bacterial extracellular polymer (exopolymer) upon uptake of particle-bound Cd, Zn and Ag by the deposit-feeding clam Macoma balthica were studied in the laboratory. Amorphous iron oxyhydroxide and unaltered and alkaline-extracted sediments were used as model particulates in separate, controlled deposit-feeding experiments. In general, amounts of metal taken up from ingested particles varied dramatically with the nature of the particle surface. Ingestion of contaminated iron oxide particles did not contribute to overall uptake of Cd and Ag in feeding clams, but accounted for 89 to 99% of total Zn uptake. Exopolymer adsorbed on iron oxide particles caused an increase in the biological availability of particle-bound metals in the order Ag>Cd>Zn, whereas adherent bacteria up to 3.2 X 1011 g-1 had no effect upon amounts of metal taken up from ingested particulates. At the higher Cd and Ag concentrations employed (3.6 X 10-7M), feeding rates declined with increasing amounts of iron oxide-bound exopolymer, suggesting behavioral avoidance due to increased metal availability. Much of the Cd (57 %) taken up by clams feeding on unaltered estuarine sediments originated from particulates, even though particle/solute distribution of Cd (86%) was similar to that in experiments with iron oxide particles. Uptake of Cd from alkalineextracted sediments was insignificant, as it was from unamended iron oxide. However, addition of exopolymer (10 mgg-1 sediment) caused a restoration nn bioavailability of sediment-bound Cd.

  16. Gum kondagogu reduced/stabilized silver nanoparticles as direct colorimetric sensor for the sensitive detection of Hg²⁺ in aqueous system.

    PubMed

    Rastogi, Lori; Sashidhar, R B; Karunasagar, D; Arunachalam, J

    2014-01-01

    A highly sensitive and selective method is reported for the colorimetric detection of Hg(2+) in aqueous system by using label free silver nanoparticles (Ag NPs). Ag NPs used in this method were synthesized by gum kondagogu (GK) which acted as both reducing and stabilizing agent. The average size of the GK-Ag NPs was found to be 5.0 ± 2.8 nm as revealed by transmission electron microscope (TEM) analysis and the nanoparticles were stable at various pH conditions (pH 4-11) and salt concentrations (5-100 mM). The GK reduced/stabilized Ag NPs (GK-Ag NPs) were directly used for the selective colorimetric reaction with Hg(2+) without any further modification. The bright yellow colour of Ag NPs was found to fade in a concentration dependent manner with the added Hg(+) ions. The fading response was directly correlated with increasing concentration of Hg(2+). More importantly, this response was found to be highly selective for Hg(2+) as the absorption spectra were found to be unaffected by the presence of other ions like; Na(+), K(+), Mg(2+), Ca(2+), Cu(2+), Ni(2+), Co(2+), As(3+), Fe(2+), Cd(2+), etc. The metal sensing mechanism is explained based on the turbidometric and X-ray diffraction (XRD) analysis of GK-Ag NPs with Hg(2+). The proposed method was successfully applied for the determination of Hg(2+) in various ground water samples. The reported method can be effectively used for the quantification of total Hg(2+) in samples, wherein the organic mercury is first oxidized to inorganic form by ultraviolet (UV) irradiation. The limit of quantification for Hg(2+) using the proposed method was as low as 4.9 × 10(-8) mol L(-1) (50 nM). The proposed method has potential application for on-field qualitative detection of Hg(2+) in aqueous environmental samples.

  17. Heavy metal (As, Cd, Hg, Pb, Cu, Zn, Se) concentrations in muscle and bone of four commercial fish caught in the central Adriatic Sea, Italy.

    PubMed

    Perugini, Monia; Visciano, Pierina; Manera, Maurizio; Zaccaroni, Annalisa; Olivieri, Vincenzo; Amorena, Michele

    2014-04-01

    Heavy metal (As, Cd, Cu, Pb, Zn, Hg and Se) concentrations in the muscle and bone of four fish species (Mullus barbatus, Merluccius merluccius, Micromesistius poutassou, and Scomber scombrus) from the central Adriatic Sea were measured and the relationships between fish size (length and weight) and metal concentrations in the tissues were investigated. Samples were analyzed by inductively coupled plasma-atomic emission spectrophotometry with automatic dual viewing. In the muscle, results of linear regression analysis showed that, except for mercury, significant relationships between metal concentrations and fish size were negative. Only mercury levels were positively correlated with Atlantic mackerel size (p < 0.05). No significant variations of heavy metal concentrations were observed in muscles of the examined species, but a significant difference (p < 0.01) was found for As, Cd, Pb, and Se concentrations in bone. All the investigated metals showed higher values in the muscle than in bone, except for lead and zinc. Regarding cadmium, lead, and mercury maximum levels, set for the edible portion by European legislation, several samples exceeded these values, confirming the heavy metal presence in species caught near the Jabuka Pit.

  18. Heavy metal (As, Cd, Hg, Pb, Cu, Zn, Se) concentrations in muscle and bone of four commercial fish caught in the central Adriatic Sea, Italy.

    PubMed

    Perugini, Monia; Visciano, Pierina; Manera, Maurizio; Zaccaroni, Annalisa; Olivieri, Vincenzo; Amorena, Michele

    2014-04-01

    Heavy metal (As, Cd, Cu, Pb, Zn, Hg and Se) concentrations in the muscle and bone of four fish species (Mullus barbatus, Merluccius merluccius, Micromesistius poutassou, and Scomber scombrus) from the central Adriatic Sea were measured and the relationships between fish size (length and weight) and metal concentrations in the tissues were investigated. Samples were analyzed by inductively coupled plasma-atomic emission spectrophotometry with automatic dual viewing. In the muscle, results of linear regression analysis showed that, except for mercury, significant relationships between metal concentrations and fish size were negative. Only mercury levels were positively correlated with Atlantic mackerel size (p < 0.05). No significant variations of heavy metal concentrations were observed in muscles of the examined species, but a significant difference (p < 0.01) was found for As, Cd, Pb, and Se concentrations in bone. All the investigated metals showed higher values in the muscle than in bone, except for lead and zinc. Regarding cadmium, lead, and mercury maximum levels, set for the edible portion by European legislation, several samples exceeded these values, confirming the heavy metal presence in species caught near the Jabuka Pit. PMID:24242233

  19. Heavy metals (Cd, Co, Cu, Ni, Pb, Fe, and Hg) content in four fish commonly consumed in Iran: risk assessment for the consumers.

    PubMed

    Hosseini, Mehdi; Nabavi, Seyed Mohammad Bagher; Nabavi, Seyedeh Narges; Pour, Nasrin Adami

    2015-05-01

    In this study, concentrations of Cd, Co, Cu, Ni, Pb, Fe, and Hg were determined in commercially valuable fish from Khuzestan shore, northwest of the Persian Gulf. It was also our intention to evaluate potential risks to human health associated with seafood consumption. The liver and skin showed higher metal concentrations than the muscle. The results showed that heavy metal concentrations in different food habitats increase in the following order: benthic omnivorous fish < zooplanktivore fish < phytoplanktivore fish < piscivore fish. Also, the comparison indicated that benthic species (Euryglossa orientalis, Otolithes ruber) were more contaminated than pelagic species (Liza abu and Psettodes erumei). Therefore, the concentration of heavy metals in edible part of fish species did not exceed the permissible limits proposed by Food and Agriculture Organization (FAO) (1983), WHO (1996), Regional Organization for the Protection of the Marine Environment (ROPME) (1999), and FAD (2001) which are suitable for human consumption, except for Ni and Cd in E. orientalis and Pb in O. ruber.

  20. The utilization of the Antarctic environmental specimen bank (BCAA) in monitoring Cd and Hg in an Antarctic coastal area in Terra Nova Bay (Ross Sea--Northern Victoria Land).

    PubMed

    Riva, S Dalla; Abelmoschi, M L; Magi, E; Soggia, F

    2004-07-01

    The first projects relating to levels of Cd and Hg on marine biota and sediments from Terra Nova Bay (Ross Sea--Antarctica) and their bioaccumulation and biomagnification in this trophic web have been carried out by research programmes pertaining to the Italian Antarctic Research Program (PNRA) since 1989. Making use of this data, and checking the same metals after 10 years thanks to the samples stored in the BCAA, we have looked for the levels of Cd and Hg in a coastal marine ecosystem of Terra Nova Bay, and have proposed using some organisms to monitor the levels of these two heavy metals in this environment where the Italian Base is located, using the data determinate in this work as background levels. In our work, the amount of Hg and Cd concentrations have been determined in biota from the inner shelf of Terra Nova Bay (Adamussium colbecki, Laternula elliptica, Odontaster validus, Sterechinus neumayeri, Trematomus bernacchii, Iridaea cordata, Phyllophora antarctica, Parborlasia corrugatus), and in two different size fractions of sieved marine sediments (<2000 microm and <63 microm). To widen the distribution of Cd and Hg in this ecosystem we have also investigated the fraction of these metals bound to the labile phase of the marine sediments, and their presence in the particulate matter found in pack-ice cores, recent snow, water column and sea microlayer.

  1. Bright white-light emission from Ag/SiO2/CdS-ZnS core/shell/shell plasmon couplers

    NASA Astrophysics Data System (ADS)

    Liao, Chen; Tang, Luping; Gao, Xiaoqin; Xu, Ruilin; Zhang, Huichao; Yu, Yongya; Lu, Changgui; Cui, Yiping; Zhang, Jiayu

    2015-12-01

    Well-defined plasmon couplers (PCs) that comprise a Ag core overcoated with a SiO2 shell with controlled thickness, followed by a monolayer of CdS-ZnS core-shell quantum dots (QDs) were synthesized to modify the emission from trap-rich CdS-ZnS QDs by adjusting the distance between the QDs and Ag nanoparticles (NPs). When the thickness of the SiO2 shell was 10 nm, because the shell could effectively suppress the non-radiative energy transfer from the semiconductor QDs to the metal NPs and the localized surface plasmon resonance (LSPR) of the Ag NPs spectrally matched the emission peak of the CdS-ZnS QDs to bring about strong plasmon coupling, optimum enhancements of the surface state emission (SSE) (17 times) and band-edge emission (BEE) (4 times) were simultaneously realized and the SSE to BEE intensity ratio was increased to 55%. As a result, a bright white-light source with 1931 Commission Internationale d'Eclairage (CIE) chromaticity coordinates of (0.32, 0.34) was realized by the superposition of the two emissions. The experimental results from Ag/SiO2/CdSe-ZnS and the Ag/SiO2/CdS:Mn-ZnS core/shell/shell PCs indicated that suppressing the non-radiative decay rate (knr) was the underlying mechanism for plasmon coupling fluorescence enhancement.

  2. CdS-Nanowires Flexible Photo-detector with Ag-Nanowires Electrode Based on Non-transfer Process

    NASA Astrophysics Data System (ADS)

    Pei, Yanli; Pei, Ruihan; Liang, Xiaoci; Wang, Yuhao; Liu, Ling; Chen, Haibiao; Liang, Jun

    2016-02-01

    In this study, UV-visible flexible resistivity-type photo-detectors were demonstrated with CdS-nanowires (NWs) percolation network channel and Ag-NWs percolation network electrode. The devices were fabricated on Mixed Cellulose Esters (MCE) membrane using a lithographic filtration method combined with a facile non-transfer process. The photo-detectors demonstrated strong adhesion, fast response time, fast decay time, and high photo sensitivity. The high performance could be attributed to the high quality single crystalline CdS-NWs, encapsulation of NWs in MCE matrix and excellent interconnection of the NWs. Furthermore, the sensing performance was maintained even the device was bent at an angle of 90°. This research may pave the way for the facile fabrication of flexible photo-detectors with high performances.

  3. CdS-Nanowires Flexible Photo-detector with Ag-Nanowires Electrode Based on Non-transfer Process

    PubMed Central

    Pei, Yanli; Pei, Ruihan; Liang, Xiaoci; Wang, Yuhao; Liu, Ling; Chen, Haibiao; Liang, Jun

    2016-01-01

    In this study, UV-visible flexible resistivity-type photo-detectors were demonstrated with CdS-nanowires (NWs) percolation network channel and Ag-NWs percolation network electrode. The devices were fabricated on Mixed Cellulose Esters (MCE) membrane using a lithographic filtration method combined with a facile non-transfer process. The photo-detectors demonstrated strong adhesion, fast response time, fast decay time, and high photo sensitivity. The high performance could be attributed to the high quality single crystalline CdS-NWs, encapsulation of NWs in MCE matrix and excellent interconnection of the NWs. Furthermore, the sensing performance was maintained even the device was bent at an angle of 90°. This research may pave the way for the facile fabrication of flexible photo-detectors with high performances. PMID:26899726

  4. Correlation Between Band Structure and Magneto- Transport Properties in HgTe/CdTe Two-Dimensional Far-Infrared Detector Superlattice

    NASA Astrophysics Data System (ADS)

    Braigue, M.; Nafidi, A.; Idbaha, A.; Chaib, H.; Sahsah, H.; Daoud, M.; Marí Soucase, B.; Mollar García, M.; Chander Singh, K.; Hartiti, B.

    2013-06-01

    Theoretical calculations of the electronic properties of n-type HgTe/CdTe superlattices (SLs) have provided an agreement with the experimental data on the magneto-transport behaviour. We have measured the conductivity, Hall mobility, Seebeck and Shubnikov-de Haas effects and angular dependence of the magneto-resistance. Our sample, grown by MBE, had a period d= d 1+ d 2 (124 layers) of d1=8.6 nm (HgTe) /d2=3.2 nm (CdTe). Calculations of the spectras of energy E( d 2), E( k z ) and E( k p ), respectively, in the direction of growth and in plane of the superlattice; were performed in the envelope function formalism. The energy E( d 2, Γ,4.2 K), shown that when d 2 increase the gap E g decrease to zero at the transition semiconductor to semimetal conductivity behaviour and become negative accusing a semimetallic conduction. At 4.2 K, the sample exhibits n type conductivity, confirmed by Hall and Seebeck effects, with a Hall mobility of 2.5 × 105 cm2/ V s. This allowed us to observe the Shubnikov-de Haas effect with n=3.20×1012 cm-2. Using the calculated effective mass (m^{*}_{E1}(EF) = 0.05 m0) of the degenerated electrons gas, the Fermi energy (2D) was E F =88 meV in agreement with 91 meV of thermoelectric power α. In intrinsic regime, α˜ T -3/2 and R H T 3/2 indicates a gap E g = E 1- HH 1=101 meV in agreement with calculated E g ( Γ,300 K)=105 meV. The formalism used here predicts that the system is semiconductor for d 1/ d 2=2.69 and d 2<100 nm. Here, d 2=3.2 nm and E g ( Γ,4.2 K)=48 meV so this sample is a two-dimensional modulated nano-semiconductor and far-infrared detector (12 μm< λ c <28 μm).

  5. Low-energy transitions in ^112Cd identified in the beta-decays of ^112Ag and ^112In

    NASA Astrophysics Data System (ADS)

    Green, K. L.; Garrett, P. E.; Demand, G. A.; Grinyer, G. F.; Leach, K. G.; Phillips, A. A.; Schumaker, M. A.; Svensson, C. E.; Wong, J.; Ball, G. C.; Bandyopadhyay, D. S.; Hackman, G.; Morton, A. C.; Pearson, C. J.; Austin, R. A. E.; Colosimo, S.; Cross, D.; Wood, J. L.; Kulp, W. D.; Yates, S. W.

    2008-10-01

    The Cd isotopes, especially ^112Cd, have been considered exceptional examples of vibrational nuclei. While many level lifetimes are known in ^112Cd, previous measurements lacked sensitivity to weak, low-energy branches that are often the most important transitions to establish collectivity. We have sought these branches through a high-statistics measurement of the β decay of ^112Ag and ^112In to ^112Cd using the 8π spectrometer at the TRIUMF-ISAC facility. The data were collected in scaled-down γ singles and γγ coincidence mode, and ˜100x10^6 events were sorted into a random-background-subtracted γγ matrix. New branches from levels below 2.5 MeV were observed, and a higher precision on several branching ratios, especially the 4^+ and 0^+ doublet of states at 1871 keV, has been achieved. Details of the analysis to date will be reported. Work supported in part by NSERC and the US DOE under grant DE-FG02-96ER40958.

  6. Ligational behavior of clioquinol antifungal drug towards Ag(I), Hg(II), Cr(III) and Fe(III) metal ions: Synthesis, spectroscopic, thermal, morphological and antimicrobial studies

    NASA Astrophysics Data System (ADS)

    El-Megharbel, Samy M.; Refat, Moamen S.

    2015-04-01

    This article presents a synthesis, characterization, theoretical and biological (anti-bacterial, and anti-fugal) evaluation studies of Ag(I), Hg(II), Cr(III) and Fe(III) complexes of clioquinol (CQ) drug ligand. Structures of the titled complexes cited herein were discussed using elemental analyses and spectral measurements e.g., IR, 1H NMR, and electronic studies. The results confirmed the formation of the clioquinol complexes by three molar ratios (1:1) for Ag(I), (1:2) for Hg(II) and (1:3) for both Cr(III) and Fe(III) metal ions. The clioquinol reacts as a bidentate chelate bound to all respected metal ions through the oxygen and nitrogen of quinoline-8-ol. The metal(II) ions coordinated to clioquinol ligand through deprotonation of sbnd OH terminal group. Infrared and 1H NMR spectral data confirm that coordination is via the oxygen of phenolic group and nitrogen atom of quinoline moiety. The molar conductance measurements of the CQ complexes in DMSO correspond to be non-electrolyte nature. Thus, these complexes may be formulated as [Ag(CQ)(H2O)2] H2O, [Hg(CQ)2]ṡ2H2O, [Cr(CQ)3] and [Fe(CQ)3]H2O. The Coats-Redfern method, the kinetic thermodynamic parameters like activation energies (E∗), entropies (ΔS∗), enthalpies (ΔH∗), and Gibbs free energies (ΔG∗) of the thermal decomposition reactions have been deduced from thermogravimetric curves (TG) with helpful of differential thermo gravimetric (DTG) curves. The narrow size distribution in nano-scale range for the clioquinol complexes have been discussed using X-ray powder diffraction (XRD), scanning electron microscope (SEM), and X-ray energy dispersive spectrometer (EDX) analyzer.

  7. High-Performance Fully Nanostructured Photodetector with Single-Crystalline CdS Nanotubes as Active Layer and Very Long Ag Nanowires as Transparent Electrodes.

    PubMed

    An, Qinwei; Meng, Xianquan; Sun, Pan

    2015-10-21

    Long and single-crystalline CdS nanotubes (NTs) have been prepared via a physical evaporation process. A metal-semiconductor-metal full-nanostructured photodetector with CdS NTs as active layer and Ag nanowires (NWs) of low resistivity and high transmissivity as electrodes has been fabricated and characterized. The CdS NTs-based photodetectors exhibit high performance, such as lowest dark currents (0.19 nA) and high photoresponse ratio (Ilight/Idark ≈ 4016) (among CdS nanostructure network photodetectors and NTs netwok photodetectors reported so far) and very low operation voltages (0.5 V). The photoconduction mechanism, including the formation of a Schottky barrier at the interface of Ag NW and CdS NTs and the effect of oxygen adsorption process on the Schottky barrier has also been provided in detail based on the studies of CdS NTs photodetector in air and vacuum. Furthermore, CdS NTs photodetector exhibits an enhanced photosensitivity as compared with CdS NWs photodetector. The enhancement in performance is dependent on the larger surface area of NTs adsorbing more oxygen in air and the microcavity structure of NTs with higher light absorption efficiency and external quantum efficiency. It is believed that CdS NTs can potentially be useful in the designs of 1D CdS-based optoelectronic devices and solar cells.

  8. AGS67E, an Anti-CD37 Monomethyl Auristatin E Antibody–Drug Conjugate as a Potential Therapeutic for B/T-Cell Malignancies and AML: A New Role for CD37 in AML

    PubMed Central

    Pereira, Daniel S.; Guevara, Claudia I.; Jin, Liqing; Mbong, Nathan; Verlinsky, Alla; Hsu, Ssucheng J.; Aviña, Hector; Karki, Sher; Abad, Joseph D.; Yang, Peng; Moon, Sung-Ju; Malik, Faisal; Choi, Michael Y.; An, Zili; Morrison, Kendall; Challita-Eid, Pia M.; Doñate, Fernando; Joseph, Ingrid B.J.; Kipps, Thomas J.; Dick, John E.; Stover, David R.

    2015-01-01

    CD37 is a tetraspanin expressed on malignant B cells. Recently, CD37 has gained interest as a therapeutic target. We developed AGS67E, an antibody–drug conjugate that targets CD37 for the potential treatment of B/T-cell malignancies. It is a fully human monoclonal IgG2 antibody (AGS67C) conjugated, via a protease-cleavable linker, to the microtubule-disrupting agent mono-methyl auristatin E (MMAE). AGS67E induces potent cytotoxicity, apoptosis, and cell-cycle alterations in many non-Hodgkin lymphoma (NHL) and chronic lymphocytic leukemia (CLL) cell lines and patient-derived samples in vitro. It also shows potent antitumor activity in NHL and CLL xenografts, including Rituxan-refractory models. During profiling studies to confirm the reported expression of CD37 in normal tissues and B-cell malignancies, we made the novel discovery that the CD37 protein was expressed in T-cell lymphomas and in AML. AGS67E bound to >80% of NHL and T-cell lymphomas, 100% of CLL and 100% of AML patient-derived samples, including CD34+CD38− leukemic stem cells. It also induced cytotoxicity, apoptosis, and cell-cycle alterations in AML cell lines and antitumor efficacy in orthotopic AML xenografts. Taken together, this study shows not only that AGS67E may serve as a potential therapeutic for B/T-cell malignancies, but it also demonstrates, for the first time, that CD37 is well expressed and a potential drug target in AML. PMID:25934707

  9. Temperature dependence of the carrier lifetime in narrow-gap Cd{sub x}Hg{sub 1–x}Te solid solutions: Radiative recombination

    SciTech Connect

    Bazhenov, N. L. Mynbaev, K. D.; Zegrya, G. G.

    2015-09-15

    The probability of the radiative recombination of carriers in narrow-gap semiconductors is analyzed for the example of Cd{sub x}Hg{sub 1–x}Te solid solutions. Expressions are derived for the imaginary part of the dielectric permittivity in terms of the three-band Kane’s model with consideration for the nonparabolic dependence of the carrier energy on the wave vector. It is shown that taking into account this nonparabolicity of the energy spectrum of carriers modifies the dependence of the imaginary part of the dielectric permittivity on frequency. Expressions for the probability of radiative recombination, derived in terms of the simple parabolic model and Kane’s model with and without the nonparabolicity effect taken into account, are compared. It is shown that the contributions to recombination from electron transitions to heavy- and light-hole bands are close and the contribution from light holes cannot be neglected when calculating the radiative-recombination probability.

  10. Can heavy metal pollution defend seed germination against heat stress? Effect of heavy metals (Cu(2+), Cd(2+) and Hg(2+)) on maize seed germination under high temperature.

    PubMed

    Deng, Benliang; Yang, Kejun; Zhang, Yifei; Li, Zuotong

    2016-09-01

    Heavy metal pollution, as well as greenhouse effect, has become a serious threat today. Both heavy metal and heat stresses can arrest seed germination. What response can be expected for seed germination under both stress conditions? Here, the effects of heavy metals (Cu(2+), Cd(2+) and Hg(2+)) on maize seed germination were investigated at 20 °C and 40 °C. Compared with 20 °C, heat stress induced thermodormancy. However, this thermodormancy could be significantly alleviated by the addition of a low concentration of heavy metals. Heavy metals, as well as heat stress induced H2O2 accumulation in germinating seeds. Interestingly, this low concentration of heavy metal that promoted seed germination could be partly blocked by DMTU (a specific ROS scavenger), irrespective of temperature. Accordingly, H2O2 addition reinforced this promoting effect on seed germination, which was induced by a low concentration of heavy metal. Furthermore, we found that the NADPH oxidase derived ROS was required for seed germination promoted by the heavy metals. Subsequently, treatment of seeds with fluridone (a specific inhibitor of ABA) or ABA significantly alleviated or aggravated thermodormancy, respectively. However, this alleviation or aggravation could be partly attenuated by a low concentration of heavy metals. In addition, germination that was inhibited by high concentrations of heavy metals was also partly reversed by fluridone. The obtained results support the idea that heavy metal-mediated ROS and hormone interaction can finally affect the thermodormancy release or not. PMID:27239687

  11. Photoluminescence of Hg{sub 1-x}Cd{sub x}Te based heterostructures grown by molecular-beam epitaxy

    SciTech Connect

    Mynbaev, K. D. Bazhenov, N. L.; Ivanov-Omskii, V. I.; Mikhailov, N. N.; Yakushev, M. V.; Sorochkin, A. V.; Remesnik, V. G.; Dvoretsky, S. A.; Varavin, V. S.; Sidorov, Yu. G.

    2011-07-15

    Photoluminescence (PL) of Hg{sub 1-x}Cd{sub x}Te-based heterostructures grown by molecular-beam epitaxy (MBE) on GaAs and Si substrates has been studied. It is shown that a pronounced disruption of the long-range order in the crystal lattice is characteristic of structures of this kind. It is demonstrated that the observed disordering is mostly due to the nonequilibrium nature of MBE and can be partly eliminated by postgrowth thermal annealing. Low-temperature spectra of epitaxial layers and structures with wide potential wells are dominated by the recombination peak of an exciton localized in density-of-states tails; the energy of this peak is substantially lower than the energy gap. In quantum-well (QW) structures at low temperatures, the main PL peak is due to carrier recombination between QW levels and the energy of the emitted photon is strictly determined by the effective (with the QW levels taken into account) energy gap.

  12. Can heavy metal pollution defend seed germination against heat stress? Effect of heavy metals (Cu(2+), Cd(2+) and Hg(2+)) on maize seed germination under high temperature.

    PubMed

    Deng, Benliang; Yang, Kejun; Zhang, Yifei; Li, Zuotong

    2016-09-01

    Heavy metal pollution, as well as greenhouse effect, has become a serious threat today. Both heavy metal and heat stresses can arrest seed germination. What response can be expected for seed germination under both stress conditions? Here, the effects of heavy metals (Cu(2+), Cd(2+) and Hg(2+)) on maize seed germination were investigated at 20 °C and 40 °C. Compared with 20 °C, heat stress induced thermodormancy. However, this thermodormancy could be significantly alleviated by the addition of a low concentration of heavy metals. Heavy metals, as well as heat stress induced H2O2 accumulation in germinating seeds. Interestingly, this low concentration of heavy metal that promoted seed germination could be partly blocked by DMTU (a specific ROS scavenger), irrespective of temperature. Accordingly, H2O2 addition reinforced this promoting effect on seed germination, which was induced by a low concentration of heavy metal. Furthermore, we found that the NADPH oxidase derived ROS was required for seed germination promoted by the heavy metals. Subsequently, treatment of seeds with fluridone (a specific inhibitor of ABA) or ABA significantly alleviated or aggravated thermodormancy, respectively. However, this alleviation or aggravation could be partly attenuated by a low concentration of heavy metals. In addition, germination that was inhibited by high concentrations of heavy metals was also partly reversed by fluridone. The obtained results support the idea that heavy metal-mediated ROS and hormone interaction can finally affect the thermodormancy release or not.

  13. Microwave-assisted ultrafast synthesis of silver nanoparticles for detection of Hg²⁺.

    PubMed

    Ma, Yun; Pang, Yuehong; Liu, Fei; Xu, Hanqi; Shen, Xiaofang

    2016-01-15

    Silver nanoparticles (AgNPs) were successfully prepared in aqueous solution by a one-pot procedure based on a rapid microwave-assisted green approach. L-Cysteine acted as a capping agent in the process of AgNP formation. The structural and morphological characteristics of the L-cysteine-capped AgNPs were investigated by the UV-vis, CD, FL, FTIR, XRD, TEM and EDX analysis. It was found that the well-dispersed crystalline AgNPs were formed after irradiation for 90 s and had sphere-like morphology. Such strategy may facilitate new ways to the synthesis of other metal nanoparticles, such as Au, Pt and Pd. In addition, the synthesized AgNPs were developed as a platform for the detection of Hg(2+) and showed a high sensitivity on the order of 1×10(-8) M. This sensing system could discriminate Hg(2+) from a wide range of cations (Ca(2+), Ba(2+), Mn(2+), etc.). The selectivity and sensitivity of AgNPs indicated its potential use as a sensor for Hg(2+) detection in the ecosystems.

  14. Microwave-assisted ultrafast synthesis of silver nanoparticles for detection of Hg2 +

    NASA Astrophysics Data System (ADS)

    Ma, Yun; Pang, Yuehong; Liu, Fei; Xu, Hanqi; Shen, Xiaofang

    2016-01-01

    Silver nanoparticles (AgNPs) were successfully prepared in aqueous solution by a one-pot procedure based on a rapid microwave-assisted green approach. L-Cysteine acted as a capping agent in the process of AgNP formation. The structural and morphological characteristics of the L-cysteine-capped AgNPs were investigated by the UV-vis, CD, FL, FTIR, XRD, TEM and EDX analysis. It was found that the well-dispersed crystalline AgNPs were formed after irradiation for 90 s and had sphere-like morphology. Such strategy may facilitate new ways to the synthesis of other metal nanoparticles, such as Au, Pt and Pd. In addition, the synthesized AgNPs were developed as a platform for the detection of Hg2 + and showed a high sensitivity on the order of 1 × 10- 8 M. This sensing system could discriminate Hg2 + from a wide range of cations (Ca2 +, Ba2 +, Mn2 +, etc.). The selectivity and sensitivity of AgNPs indicated its potential use as a sensor for Hg2 + detection in the ecosystems.

  15. AC susceptibility of the Hg0.3La0.7Ba2Ca3(Cu0.95Ag0.5)4O10+δ superconductor

    NASA Astrophysics Data System (ADS)

    Mostafa, M. F.; Hassen, A.

    2016-09-01

    In this work, the temperature, magnetic field and frequency dependence of the ac susceptibility of Hg0.3La0.7Ba2Ca3(Cu0.95Ag0.5)4O10+δ were studied. The superconductivity still survives even at this amount of Ag. The magnetic field dependence of the irreversibility line (IL) and the flux pinning of this compound are discussed and compared with those of low Ag content. The IL exhibits thermally activated behaviour. A collective creep of the vortex bundle also occurs for this level of doping. A crossover from a two- to a three-dimensional system is suggested at T/Tc = 0.75 and a magnetic field, Hdc = 0.04 T. Based on vortex glass phase transition theory, the effective pinning energy, ueff, was calculated. The change in the characteristic temperature of the studied compound and that of low Ag content samples are summarised. Comparisons with similar materials are discussed.

  16. Ag nanoclusters could efficiently quench the photoresponse of CdS quantum dots for novel energy transfer-based photoelectrochemical bioanalysis.

    PubMed

    Zhang, Ling; Sun, Yue; Liang, Yan-Yu; He, Jian-Ping; Zhao, Wei-Wei; Xu, Jing-Juan; Chen, Hong-Yuan

    2016-11-15

    Herein the influence of ultrasmall Ag nanoclusters (Ag NCs) against CdS quantum dots (QDs) in a photoelectrochemical (PEC) nanosystem was exploited for the first time, based on which a novel PEC bioanalysis was successfully developed via the efficient quenching effect of Ag NCs against the CdS QDs. In a model system, DNA assay was achieved by using molecular beacon (MB) probes anchored on a CdS QDs modified electrode, and the MB probes contain two segments that can hybridize with both target DNA sequence and the label of DNA encapsulated Ag NCs. After the MB probe was unfolded by the target DNA sequence, the labels of oligonucleotide encapsulated Ag NCs would be brought in close proximity to the CdS QDs electrode surface, and efficient photocurrent quenching of QDs could be resulted from an energy transfer process that originated from NCs. Thus, by monitoring the attenuation in the photocurrent signal, an elegant and sensitive PEC DNA bioanalysis could be accomplished. The developed biosensor displayed a linear range from 1.0pM to 10nM and the detection limit was experimentally found to be of 0.3pM. This work presents a feasible signaling principle that could act as a common basis for general PEC bioanalysis development. PMID:27315518

  17. Bioconcentration of Ag, Cd, Co, Mn and Zn in the Mangrove Oyster (Crassostrea gasar) and Preliminary Human Health Risk Assessment: A Radiotracer Study.

    PubMed

    Kuranchie-Mensah, Harriet; Teyssié, Jean-Louis; Oberhänsli, François; Tumnoi, Yutthana; Pouil, Simon; Warnau, Michel; Metian, Marc

    2016-09-01

    Bioaccumulation kinetics of five dissolved metals were determined in the mangrove oyster Crassostrea gasar, using corresponding radiotracers ((54)Mn, (57)Co, (65)Zn, (109)Cd and (110m)Ag). Additionally, their bioaccessibility to human consumers was estimated. Results indicated that over a 14-day exposure (54)Mn and (57)Co were linearly concentrated in oysters whereas (109)Cd, (65)Zn and (110m)Ag were starting to saturate (steady-state not reached). Whole-body concentration factors at 14 days (CF14d in toto) ranged from 187 ± 65 to 629 ± 179 with the lowest bioconcentration capacity for Co and the highest for Ag. Depuration kinetics were best described by a double-exponential model with associated biological half-lives ranging from 26 days (Ag) to almost 8 months (Zn and Cd). Bioaccessible fraction of the studied elements was estimated using in vitro digestions, which suggested that oysters consumed seasoned with lemon enhanced the accessibility of Cd, Mn and Zn to human consumers, but not Ag and Co. PMID:27194421

  18. Ag nanoclusters could efficiently quench the photoresponse of CdS quantum dots for novel energy transfer-based photoelectrochemical bioanalysis.

    PubMed

    Zhang, Ling; Sun, Yue; Liang, Yan-Yu; He, Jian-Ping; Zhao, Wei-Wei; Xu, Jing-Juan; Chen, Hong-Yuan

    2016-11-15

    Herein the influence of ultrasmall Ag nanoclusters (Ag NCs) against CdS quantum dots (QDs) in a photoelectrochemical (PEC) nanosystem was exploited for the first time, based on which a novel PEC bioanalysis was successfully developed via the efficient quenching effect of Ag NCs against the CdS QDs. In a model system, DNA assay was achieved by using molecular beacon (MB) probes anchored on a CdS QDs modified electrode, and the MB probes contain two segments that can hybridize with both target DNA sequence and the label of DNA encapsulated Ag NCs. After the MB probe was unfolded by the target DNA sequence, the labels of oligonucleotide encapsulated Ag NCs would be brought in close proximity to the CdS QDs electrode surface, and efficient photocurrent quenching of QDs could be resulted from an energy transfer process that originated from NCs. Thus, by monitoring the attenuation in the photocurrent signal, an elegant and sensitive PEC DNA bioanalysis could be accomplished. The developed biosensor displayed a linear range from 1.0pM to 10nM and the detection limit was experimentally found to be of 0.3pM. This work presents a feasible signaling principle that could act as a common basis for general PEC bioanalysis development.

  19. Development of a Method for Chemical-Mechanical Preparation of the Surface of CdZnTe Substrates for HgCdTe-Based Infrared Focal-Plane Arrays

    NASA Astrophysics Data System (ADS)

    Pelenc, D.; Merlin, J.; Etcheberry, A.; Ballet, P.; Baudry, X.; Brellier, D.; Destefanis, V.; Ferron, A.; Fougères, P.; Giotta, D.; Grangier, C.; Mollard, L.; Perez, A.; Rochette, F.; Rubaldo, L.; Vaux, C.; Vigneron, J.; Zanatta, J.-P.

    2014-08-01

    This paper reports the first implementation in our laboratory of a chemical-mechanical polishing (CMP) process for CdZnTe (CZT) substrates prepared for growth of HgCdTe layers by liquid phase epitaxy and molecular beam epitaxy. The process enables significant reduction of the thickness of the damaged zone induced by the mechanical polishing that must be etched away before epitaxy. Resulting improvements in surface morphology, in terms of waviness and density of point defects, are reported. The chemical state of surfaces polished by CMP was characterized by x-ray photoelectron spectroscopy. The chemical state was highly homogeneous; comparison with a reference surface is reported. End use assessment of this surface processing was compared with that of reference substrates by preparation of focal-plane arrays in the medium-wavelength infrared spectral range, by using epitaxial layers grown on substrates polished by different methods. The electro-optical performance of the detectors, in terms of photovoltaic noise operability, are reported. The results reveal that the state of this CMP surface is at the level of the best commercial substrates.

  20. Enhanced DSSCs efficiency via Cooperate co-absorbance (CdS QDs) and plasmonic core-shell nanoparticle (Ag@PVP)

    PubMed Central

    Amiri, Omid; Salavati-Niasari, Masoud; Bagheri, Samira; Yousefi, Amin Termeh

    2016-01-01

    This paper describes cooperate the co-absorbance (CdS QDs) and the plasmonic core-shell nanoparticles (Ag@PVP) of dye synthesized solar cells in which CdS QDs and Ag@PVP are incorporated into the TiO2 layer. Cooperative nanoparticles show superior behavior on enhancing light absorption in comparison with reference cells. Cooperated DSSC exhibits the best performance with the power conversion efficiency of 7.64% which is superior to that of the free–modified DSSC with the PCE of 5%. Detailed studies offer an effective approach to enhance the efficiency of dye synthesized solar cells. PMID:27143126

  1. Enhanced DSSCs efficiency via Cooperate co-absorbance (CdS QDs) and plasmonic core-shell nanoparticle (Ag@PVP)

    NASA Astrophysics Data System (ADS)

    Amiri, Omid; Salavati-Niasari, Masoud; Bagheri, Samira; Yousefi, Amin Termeh

    2016-05-01

    This paper describes cooperate the co-absorbance (CdS QDs) and the plasmonic core-shell nanoparticles (Ag@PVP) of dye synthesized solar cells in which CdS QDs and Ag@PVP are incorporated into the TiO2 layer. Cooperative nanoparticles show superior behavior on enhancing light absorption in comparison with reference cells. Cooperated DSSC exhibits the best performance with the power conversion efficiency of 7.64% which is superior to that of the free-modified DSSC with the PCE of 5%. Detailed studies offer an effective approach to enhance the efficiency of dye synthesized solar cells.

  2. Pb-Bi-Ag-Cu-(Hg) chemistry of galena and some associated sulfosalts. A review and some new data from Colorado California and Pennsylvania

    USGS Publications Warehouse

    Foord, Eugene E.; Shawe, Daniel R.

    1989-01-01

    Galena, associated with Pb-Bi-Ag sulfosalts and simple sulfides, contains varied amounts of Ag and Bi in the Dandy vein system, Idarado mine, Ouray, Colorado; the Jackass mine, Darwin District, California; and the Leadville district, Colorado. Silver- and bismuth-bearing galena associated with minor amounts of pyrite, chalcopyrite and sphalerite occur at the Pequea mine, Lancaster County, Pennsylvania. Ag and Bi contents in the Dandy suite of galena range from about 1.4 to 3.4 and 2.5 to 6.5 wt.% respectively, and are comparable or lower in galena from the other localities. Exsolved matildite is present in galena from the Dandy, Jackass and Leadville localities. The presence in significant amounts of both Ag and Bi in a Pb-rich sulfide system is necessary for formation of PbSss (galena solid-solution). If Ag (especially) and Bi (to a lesser extent) are absent, the galena formed will be essentially pure PbS. Some minor Sb may substitute for Bi. Compositional data for all of the galena samples are in agreement with a previously proposed linear relationship between a and Ag-Bi(Sb) content. Matildite and seven additional Pb-Bi-Ag-Cu sulfosalts have been identified from the Dandy vein system, based on electron-microprobe analyses and some X-ray powder-diffraction data.

  3. Confirmation of Auger-1 Minority-Carrier Lifetimes in Hg0.77Cd0.23Te and Prediction of Dark Current for Long-Wave Infrared Focal-Plane Arrays

    NASA Astrophysics Data System (ADS)

    Destefanis, V.; Kerlain, A.

    2016-09-01

    Minority-carrier lifetime measurements have been carried out on Hg0.77Cd0.23Te (111)B materials with gap suitable for detection in the Long-Wave Infrared (LWIR) band. The materials were grown on top of CdZnTe substrates using a liquid-phase epitaxy (LPE) process. From measurements done at 80 K, a clear difference in terms of minority-carrier lifetimes was obtained, as expected, between p-intrinsic (≤5 ns) and n-extrinsic doped samples (420 ns). Minority-carrier lifetimes were also measured as a function of temperature for the n-type samples. Auger-1-limited lifetimes were demonstrated over a wide temperature range (from 80 K to 300 K) with negligible Radiative or Shockley-Read-Hall lifetime contributions. Predictions of dark current densities are made from those lifetime measurements, assuming an Auger-1-limited lifetime. The agreement is very good between the predictions and dark current densities measured from p-on- n 640 × 512 pixels LWIR HgCdTe focal-plane arrays with 15- μm pitch from SOFRADIR, Agreement between predicted and measured dark currents and Rule'07 for LWIR is also demonstrated herein. Finally, minority-carrier lifetime measurements are demonstrated as a predictive method for focal-plane array performance. State-of-the-art dark currents from SOFRADIR p-on- n LWIR focal-plane arrays based upon high-quality HgCdTe materials are also illustrated.

  4. Comparison of a static and a dynamic in vitro model to estimate the bioaccessibility of As, Cd, Pb and Hg from food reference materials Fucus sp. (IAEA-140/TM) and Lobster hepatopancreas (TORT-2).

    PubMed

    Torres-Escribano, Silvia; Denis, Sylvain; Blanquet-Diot, Stéphanie; Calatayud, Marta; Barrios, Laura; Vélez, Dinoraz; Alric, Monique; Montoro, Rosa

    2011-01-01

    Bioaccessibility, the fraction of an element solubilized during gastrointestinal digestion and available for absorption, is a factor that should be considered when evaluating the health risk of contaminants from food. Static and dynamic models that mimic human physiological conditions have been used to evaluate bioaccessibility. This preliminary study compares the bioaccessibility of arsenic (As), cadmium (Cd), lead (Pb) and mercury (Hg) in two food certified reference materials (CRMs) (seaweed: Fucus sp., IAEA-140/TM; Lobster hepatopancreas: TORT-2), using two in vitro gastrointestinal digestion methods: a static method (SM) and a dynamic multicompartment method (TIM-1). There are significant differences (p<0.05) between the bioaccessible values of As, Cd, Pb and Hg obtained by SM and TIM-1 in the two CRMs. The specific form in which the elements studied are present in the CRM may help to explain the bioaccessibility values obtained.

  5. Structure of the quantum spin Hall states in HgTe/CdTe and InAs/GaSb/AlSb quantum wells

    NASA Astrophysics Data System (ADS)

    Klipstein, P. C.

    2015-01-01

    A solution of the k . p model is presented for bulk and quantum spin hall (QSH) edge states in semiconductor topological insulator (TI) quantum wells (QWs), bounded at the edge by an infinite wall potential. The edge states are exponentially localized, with a nonzero amplitude at the QW edge, and obey standard boundary conditions for the wave function and its derivative. Single helical edge states with spin locked to the direction of motion are found in the TI band gap (ETI) of QWs with both strong (HgTe/CdTe) and weak (InAs/GaSb/AlSb) s -p hybridization, but in the second case only below a small critical band gap, Ecrit˜1.6 meV . For ETI>Ecrit , there appear to be two degenerate states for each spin direction. It is suggested that Z2-like topological properties can still be maintained if one of these states is spurious or suppressed by disorder. The effect of interface band mixing, and band mixing due to structural inversion asymmetry and bulk inversion asymmetry is also considered. Simple model Hamiltonians are developed for the bulk and edge states which are calibrated against a bulk eight-band k . p calculation close to the TI transition. At the transition, the zero gap bulk states exhibit a spin splitting, essentially changing the Dirac point to a circle. In the TI phase, there is a small change in the dispersion of the QSH edge states. These results confirm the robustness of the QSH edge states to spatial symmetry breaking interactions.

  6. Low-Temperature Activation of Ion-Implanted Boron and Nitrogen Ions in Cd x Hg1- x Te Heteroepitaxial Layers

    NASA Astrophysics Data System (ADS)

    Voitsekhovskii, A. V.; Talipov, N. Kh.

    2013-12-01

    Processes of electrical activation of ion-implanted boron and nitrogen atoms in Cd x Hg1- x Te (CMT) heteroepitaxial layers grown by methods of molecular-beam epitaxy (HEL CMT MBE) and liquid-phase epitaxy (LPE CMT) have been investigated; likewise in bulk crystals of CMT with low-temperature annealings under anodic oxide. The possibility has been demonstrated of using anodic oxide as an efficient mask for postimplantation annealings of p-type HEL CMT MBE in the temperature interval Т = 200-250°C without disruption of the composition of the variband layer or alteration of the electrophysical properties of the structure. It has been established that in HEL CMT MBE the efficiency of activation of boron as a slowly diffusing donor impurity is lowered with growth of the dose of the B+ ions and is increased by thermal cycling from Т = 77 K to room temperature. Implanted nitrogen, in contrast to boron, is a rapidly diffusing acceptor impurity in CMT, efficiently compensating both radiation donor centers and activated boron. The degree of electrical activation of nitrogen grows substantially upon thermal cycling. It has been shown that the mobility spectrum is an efficient method for monitoring the process of electrical activation of boron in p-type HEL CMT MBE. Mesa photodiodes based on activated boron in p-type HEL CMT MBE with long-wavelength photosensitivity boundary λc = 11 μm, prepared here for the first time, had a high maximum value of the product of the differential resistance by the area of the photodiode R d A = (6 - 8)ṡ102 Ωṡcm2, product R 0 A = 5 - 6 Ωṡcm2 (at zero bias), and a diffusion ledge on the inverse branch of the current-voltage ( I- V) characteristic out to a bias voltage of 1.3 V.

  7. DNA Damage and Transcriptional Changes in the Gills of Mytilus galloprovincialis Exposed to Nanomolar Doses of Combined Metal Salts (Cd, Cu, Hg)

    PubMed Central

    Varotto, Laura; Domeneghetti, Stefania; Rosani, Umberto; Manfrin, Chiara; Cajaraville, Miren P.; Raccanelli, Stefano; Pallavicini, Alberto; Venier, Paola

    2013-01-01

    Aiming at an integrated and mechanistic view of the early biological effects of selected metals in the marine sentinel organism Mytilus galloprovincialis, we exposed mussels for 48 hours to 50, 100 and 200 nM solutions of equimolar Cd, Cu and Hg salts and measured cytological and molecular biomarkers in parallel. Focusing on the mussel gills, first target of toxic water contaminants and actively proliferating tissue, we detected significant dose-related increases of cells with micronuclei and other nuclear abnormalities in the treated mussels, with differences in the bioconcentration of the three metals determined in the mussel flesh by atomic absorption spectrometry. Gene expression profiles, determined in the same individual gills in parallel, revealed some transcriptional changes at the 50 nM dose, and substantial increases of differentially expressed genes at the 100 and 200 nM doses, with roughly similar amounts of up- and down-regulated genes. The functional annotation of gill transcripts with consistent expression trends and significantly altered at least in one dose point disclosed the complexity of the induced cell response. The most evident transcriptional changes concerned protein synthesis and turnover, ion homeostasis, cell cycle regulation and apoptosis, and intracellular trafficking (transcript sequences denoting heat shock proteins, metal binding thioneins, sequestosome 1 and proteasome subunits, and GADD45 exemplify up-regulated genes while transcript sequences denoting actin, tubulins and the apoptosis inhibitor 1 exemplify down-regulated genes). Overall, nanomolar doses of co-occurring free metal ions have induced significant structural and functional changes in the mussel gills: the intensity of response to the stimulus measured in laboratory supports the additional validation of molecular markers of metal exposure to be used in Mussel Watch programs. PMID:23355883

  8. Dopant in Near-Surface Semiconductor Layers of Metal-Insulator-Semiconductor Structures Based on Graded-Gap p-Hg0.78Cd0.22Te Grown by Molecular-Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Voitsekhovskii, A. V.; Nesmelov, S. N.; Dzyadukh, S. M.

    2016-02-01

    Peculiarities in determining the dopant concentration and dopant distribution profile in the near-surface layer of a semiconductor are investigated by measuring the admittance of metal-insulator-semiconductor structures (MIS structures) based on p-Hg0.78Cd0.22Te grown by molecular beam epitaxy. The dopant concentrations in the near-surface layer of the semiconductor are determined by measuring the admittance of MIS structures in the frequency range of 50 kHz to 1 MHz. It is shown that in this frequency range, the capacitance-voltage characteristics of MIS structures based on p-Hg0.78Cd0.22Te with a near-surface graded gap layer demonstrate a high-frequency behavior with respect to the recharge time of surface states located near the Fermi level for an intrinsic semiconductor. The formation time of the inversion layer is decreased by less than two times, if a near-surface graded-gap layer is created. The dopant distribution profile in the near-surface layer of the semiconductor is found, and it is shown that for structures based on p-Hg0.78Cd0.22Te with a near-surface graded-gap layer, the dopant concentration has a minimum near the interface with the insulator. For MIS structure based on n-Hg0.78Cd0.22Te, the dopant concentration is more uniformly distributed in the near-surface layer of the semiconductor.

  9. Peculiarities of Determining the Dopant Concentration in the Near-Surface Layer of a Semiconductor by Measuring the Admittance of MIS Structures Based on P-Hg0.78Cd0.22Te Grown by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Voitsekhovskii, A. V.; Nesmelov, S. N.; Dzyadukh, S. M.

    2016-06-01

    Peculiarities of determining the concentration and distribution profile of dopant in the near-surface layer of a semiconductor by measuring the admittance of MIS structures based on p-Hg0.78Cd0.22Te grown by molecular beam epitaxy are studied. A technique is proposed for the determining the concentration of dopant based on the measurement of the admittance of MIS structures in the frequency range of 50 kHz - 1 MHz. It is shown that in this frequency range, the capacitance-voltage characteristics of MIS structures based on p-Hg0.78Cd0.22Te with a near-surface graded-gap layer have a high- frequency behavior with respect to the recharge time of surface states located near the Fermi level of intrinsic semiconductor. The distribution profile of dopant in the nearsurface layer of the semiconductor is calculated. It is shown that in p-Hg0.78Cd0.22Te with a near-surface graded-gap layer, the dopant concentration has the lowest value near the interface with the insulator.

  10. Impacts of anthropogenic pressures on the water quality of the Gironde Estuary (SW France) from the Urban Agglomeration of Bordeaux: spatial characterization and inputs of trace metal elements (Ag, As, Cd, Cu, Pb and Zn)

    NASA Astrophysics Data System (ADS)

    Kessaci, Kahina; Coynel, Alexandra; Blanc, Gérard; Deycard, Victoria N.; Derriennic, Hervé; Schäfer, Jörg

    2014-05-01

    Recent European legislation (2000/60/CE) has listed eight trace metal elements as priority toxic substances for water quality. Urban metal inputs into hydrosystems are of increasing interest to both scientists and managers facing restrictive environmental protection policies, population increase and changing metal applications. The Gironde Estuary (SW France; 625 km2) is known for its metal/metalloid pollution originating from industrial (e.g. Cd, Zn, Cu, As, Ag, Hg) or agricultural sources (e.g. Cu) in the main fluvial tributaries (Garonne and Dordogne Rivers). However, little peer-reviewed scientific work has addressed the impact of urban sources on the Gironde Estuary, especially the Urban Agglomeration of Bordeaux (~1 million inhabitants) located on the downstream branch of the Garonne River. In this study, a snapshot sampling campaign was performed in 2011 for characterizing the spatial distribution of dissolved and particulate metal/metalloid (As, Ag, Cd, Pb, Zn, Cu) concentrations in three suburban watersheds: the Jalle of Blanquefort (330 km2), Eau Bourde (140 km2), and Peugue (112 km2). Furthermore, particulate metal Enrichment Factors (EF) were calculated using local geochemical background measured at the bottom of a sediment core (492 cm). Results indicated that metal concentrations displayed a high spatial variability depending on the suburban watershed and the studied element. Local concentrations anomalies were observed for: (i) As in the Eau Bourde River in dissolved (4.2 μg/l) and particulate phases (246 mg/kg; EF= 20) and attributed to a nearby industrial incinerator; (ii) Zn in the Peugue River with maximum dissolved and particulate concentrations of 87 μg/l and 1580 mg/kg (EF=17), respectively, probably due to urban habitation runoff; (iii) Ag in the Jalle of Blanquefort River with high dissolved (74 ng/l) and particulate concentrations (33.7 mg/kg; EF=117) due to industrial activities in the downstream part. Based on hydro

  11. Analysis of the auger recombination rate in P+N-n-N-N HgCdTe detectors for HOT applications

    NASA Astrophysics Data System (ADS)

    Schuster, J.; Tennant, W. E.; Bellotti, E.; Wijewarnasuriya, P. S.

    2016-05-01

    Infrared (IR) photon detectors must be cryogenically cooled to provide the highest possible performance, usually to temperatures at or below ~ 150K. Such low operating temperatures (Top) impose very stringent requirements on cryogenic coolers. As such, there is a constant push in the industry to engineer new detector architectures that operate at higher temperatures, so called higher operating temperature (HOT) detectors. The ultimate goal for HOT detectors is room temperature operation. While this is not currently possibly for photon detectors, significant increases in Top are nonetheless beneficial in terms of reduced size, weight, power and cost (SWAP-C). The most common HgCdTe IR detector architecture is the P+n heterostructure photodiode (where a capital letter indicates a wide band gap relative to the active layer or "AL"). A variant of this architecture, the P+N-n-N-N heterostructure photodiode, should have a near identical photo-response to the P+n heterostructure, but with significantly lower dark diffusion current. The P+N-n-N-N heterostructure utilizes a very low doped AL, surrounded on both sides by wide-gap layers. The low doping in the AL, allows the AL to be fully depleted, which drastically reduces the Auger recombination rate in that layer. Minimizing the Auger recombination rate reduces the intrinsic dark diffusion current, thereby increasing Top. Note when we use the term "recombination rate" for photodiodes, we are actually referring to the net generation and recombination of minority carriers (and corresponding dark currents) by the Auger process. For these benefits to be realized, these devices must be intrinsically limited and well passivated. The focus of this proceeding is on studying the fundamental physics of the intrinsic dark currents in ideal P+N-n-N-N heterostructures, namely Auger recombination. Due to the complexity of these devices, specifically the presence of multiple heterojunctions, numerical device modeling techniques must be

  12. Cluster formation in Ag{sub 2}O-P{sub 2}O{sub 5}-CdCl{sub 2} glass system

    SciTech Connect

    Das, S.S.; Singh, N.B.

    2008-11-03

    Ag{sub 2}O-P{sub 2}O{sub 5} and Ag{sub 2}O-P{sub 2}O{sub 5}-20 wt% CdCl{sub 2} glasses were prepared by melt quenching method and characterized with the help of several experimental techniques. Powder X-ray diffraction study indicated that the glasses are amorphous in nature. DSC studies showed that CdCl{sub 2} doped glass is chemically more durable. Electrical conductivity and ionic transference number measurements have shown that both the glasses are ionic conductors with Ag{sup +} ions as the charge carriers. The electrical conductivity of the doped glass is found to be higher than the undoped one. Structures of the glasses have been proposed on the basis of IR spectral analysis. From SEM studies it has been inferred that addition of 20 wt% CdCl{sub 2} modifies the morphology of Ag{sub 2}O-P{sub 2}O{sub 5} glass and in its presence formation of clusters composed of nanofibers occur.

  13. Application of hybrid SiO2-coated CdTe nanocrystals for sensitive sensing of Cu2+ and Ag+ ions.

    PubMed

    Cao, Yongqiang; Zhang, Aiyu; Ma, Qian; Liu, Ning; Yang, Ping

    2013-01-01

    A new ion sensor based on hybrid SiO2 -coated CdTe nanocrystals (NCs) was prepared and applied for sensitive sensing of Cu(2+) and Ag(+) for the selective quenching of photoluminescence (PL) of NCs in the presence of ions. As shown by ion detection experiments conducted in pure water rather than buffer solution, PL responses of NCs were linearly proportional to concentrations of Cu(2+) and Ag(+) ions < 3 and 7 uM, respectively. Much lower detection limits of 42.37 nM for Cu(2+) and 39.40 nM for Ag(+) were also observed. In addition, the NC quenching mechanism was discussed in terms of the characterization of static and transient optical spectra. The transfer and trapping of photoinduced charges in NCs by surface energy levels of CuS and Ag2 S clusters as well as surface defects generated by the exchange of Cu(2+) and Ag(+) ions with Cd(2+) ion in NCs, resulted in PL quenching and other optical spectra changes, including steady-state absorption and transient PL spectra. It is our hope that these results will be helpful in the future preparation of new ion sensors. PMID:23427119

  14. 3-D Modeling of Double-Diffusive Convection During Directional Solidification of a Non-Dilute Alloy with Application to the HgCdTe Growth Under Microgravity Conditions

    NASA Technical Reports Server (NTRS)

    Bune, Andris V.; Gillies, Donald C.; Lehoczky, Sandor L.

    1998-01-01

    A numerical calculation for a non-dilute alloy solidification was performed using the FIDAP finite element code. For low growth velocities plane front solidification occurs. The location and the shape of the interface was determined using melting temperatures from the HgCdTe liquidus curve. The low thermal conductivity of the solid HgCdTe causes thermal short circuit through the ampoule walls, resulting in curved isotherms in the vicinity of the interface. Double-diffusive convection in the melt is caused by radial temperature gradients and by material density inversion with temperature. Cooling from below and the rejection at the solid-melt interface of the heavier HgTe-rich solute each tend to reduce convection. Because of these complicating factors dimensional rather then non-dimensional modeling was performed. Estimates of convection contributions for various gravity conditions was performed parametrically. For gravity levels higher then 1 0 -7 of earth's gravity it was found that the maximum convection velocity is extremely sensitive to gravity vector orientation and can be reduced at least by factor of 50% for precise orientation of the ampoule in the microgravity environment. The predicted interface shape is in agreement with one obtained experimentally by quenching. The results of 3-D modeling are compared with previous 2-D finding. A video film featuring melt convection will be presented.

  15. Theoretical and experimental investigation of doping M in ZnSe (M = Cd, Mn, Ag, Cu) clusters: optical and bonding characteristics.

    PubMed

    Xu, Shuhong; Xu, Xiaojing; Wang, Chunlei; Zhao, Zengxia; Wang, Zhuyuan; Cui, Yiping

    2016-03-01

    The optical and bonding characteristics of doping ZnSe quantum dots (QDs) were investigated. Cd-, Mn-, Ag- and Cu-doped ZnSe were synthesized in aqueous solution. Theoretically, the intensity of the Cd-Se bond was similar to that of the Zn-Se bond, which illustrates that Cd can be doped into ZnSe materials at any ratio. We found that Mn-Se bonding was stronger than Zn-Se bonding. Ag-doped ZnSe nanoclusters show the same bonding and configuration as Cu-doped ZnSe. Moreover, Cd can be doped into ZnSe using both the substitution- and vacancy-doping method. For Mn-doped ZnSe clusters, small amounts of Mn impurity lead to stronger bonding with Se, but larger amounts of Mn impurity led to the formation of a Mn-Mn metal bond. The theoretical results show that it is difficult to form a vacancy-doping cluster for Mn-doped ZnSe materials. In experiments, the absorption and photoluminescence (PL) spectral wavelengths of Mn-doped ZnSe nanocrystals were the same as those of pure ZnSe nanocrystals, showing that the Mn impurity is not doped into ZnSe nanocrystals. Ag- and Cu-doped ZnSe nanocrystals have the same PL characteristics. The doping of an impurity is related to the solubility product, and not the bonding intensity.

  16. 210Po Activity and concentrations of selected trace elements (As, Cd, Cu, Hg, Pb, Zn) in the muscle tissue of tunas Thunnus albacares and Katsuwonus pelamis from the Eastern Pacific Ocean.

    PubMed

    Ruelas-Inzunza, Jorge; Soto-Jiménez, Martín Federico; Ruiz-Fernández, Ana Carolina; Bojórquez-Leyva, Humberto; Pérez-Bernal, Hascibe; Páez-Osuna, Federico

    2012-12-01

    Daily mineral intake (DMI) of Cu and Zn, percentage weekly intake (PWI) of As, Cd, Hg, Pb, and doses of (210)Po were estimated by using their elemental concentration in muscle of two tuna species and the average tuna consumption in Mexico. Skipjack tuna Katsuwonus pelamis had significantly (p < 0.05) higher levels of As (1.38 μg g(-1) dw) and Cu (1.85 μg g(-1) dw) than yellowfin tuna Thunnus albacares, whereas Pb concentrations (0.18 μg g(-1) dw) were significantly (p < 0.05) higher in T. albacares. The sequence of elemental concentrations in both species was Zn > Cu > As > Hg > Pb > Cd. In T. albacares, concentrations of Cd and Pb in muscle tissue were positively correlated (p < 0.05) with weight of specimens, while Cu was negatively correlated. DMI values were below 10 %. PWI figures (<2 %) are not potentially harmful to human health. (210)Po concentration in T. albacares and K. pelamis accounts for 13.5 to 89.7 % of the median individual annual dose (7.1 μSv) from consumption of marine fish and shellfish for the world population. PMID:22684512

  17. Characterisation of dark current in novel Hg 1- xCd xTe mid-wavelength infrared photovoltaic detectors based on n-on-p junctions formed by plasma-induced type conversion

    NASA Astrophysics Data System (ADS)

    Rais, M. H.; Musca, C. A.; Antoszewski, J.; Dell, J. M.; Nener, B. D.; Faraone, L.

    2000-06-01

    This paper reports initial characterisation results for planar mid-wavelength infrared (MWIR) photodiodes fabricated using a novel reactive ion plasma-induced n-on-p junction formation technology on vacancy-doped p-type HgCdTe grown by LPE on CdZnTe substrates. The junction is formed without the need for post-implant annealing typically required by ion implantation junction formation techniques to repair damage or to move the junction away from damaged regions. The dark current and dynamic resistance, Rd, of the fabricated photodiodes have been characterised as a function of temperature. At 80 K, the zero-bias dynamic resistance-junction area product ( R0A) of the diodes is 4.6×10 7 Ω cm 2, with the devices being diffusion limited down to ˜135 K. Dynamic resistance has been measured for temperatures between 80 and 195 K and biases between -200 and +150 mV. Modelling of the observed dark current has been undertaken using three distinct mechanisms, diffusion, generation-recombination, and trap-assisted tunnelling. The results show that the plasma-induced junction formation technique can produce high-performance planar HgCdTe photodiodes. The dark current mechanisms found in these devices are similar to those found in diodes formed using conventional ion implantation techniques.

  18. Le gisement Ag sbnd Hg de Zgounder (Jebel Siroua, Anti-Atlas, Maroc) : un épithermal néoprotérozoïque de type Imiter

    NASA Astrophysics Data System (ADS)

    Marcoux, Éric; Wadjinny, Ahmed

    2005-12-01

    The Zgounder ore deposit (Anti-Atlas, Morocco), is hosted in a PII-PIII Proterozoic volcanosedimentary series. Disseminated mineralization is dominated by mercuriferous native silver (2 to 30 wt.% Hg), with few silver sulfosalts (acanthite, pearceite), arsenopyrite and base-metal sulfides. Arsenic grade of arsenopyrite and homogenisation temperatures of fluid inclusions indicate initial conditions of high temperature (above 400 °C). Lead isotope compositions comfort a Late-Proterozoic age and a crustal origin for metals. Similarities are obvious with the neighbouring silver ore deposit of Imiter and lead to consider Zgounder as another example of Neoproterozoic epithermal deposit in the Anti-Atlas of Morocco, a region that appears more and more as a silver metallogenic province. To cite this article: É. Marcoux, A. Wadjinny, C. R. Geoscience 337 (2005).

  19. The evaluation of a HgCdTe photomixer with a Tunable Diode Laser (TDL) and the evaluation of TDL's as a local oscillator in a heterodyne detection system

    NASA Technical Reports Server (NTRS)

    Harward, C. N.; Kindle, E. C.

    1977-01-01

    Heterodyne systems would be much more versatile if a broadly tunable laser, such as a semiconductor diode laser (TDL), could be used as the local oscillator (LO). Previous studies have shown that while a TDL can be used as an LO, the TDL lack sufficient power to cause the signal-to-noise ratio to be shot noise limited. The heterodyne system with a HgCdTe photodiode as the LO was characterized and the beat frequency response of the heterodyne systems was mapped out.

  20. Dependence of the electrical parameters of MBE-grown Cd{sub x}Hg{sub 1} {sub -} {sub x}Te films on the level of doping with indium

    SciTech Connect

    Varavin, V. S. Dvoretskii, S. A.; Ikusov, D. G.; Mikhailov, N. N.; Sidorov, Yu. G.; Sidorov, G. Yu.; Yakushev, M. V.

    2008-06-15

    Dependences of the minority-carrier lifetime and electron mobility in Cd{sub x}Hg{sub 1-x}Te films on their indium-doping level are studied. Films with x {approx} 0.22 grown by molecular-beam epitaxy on GaAs substrates were in situ doped with indium across their entire thickness. The temperature dependences of the lifetime were studied in the temperature range 77-300 K. The decrease in the lifetime, observed as the doping level increases, is governed by the mechanism of Auger recombination. As the doping level becomes higher, the mobility decreases in qualitative agreement with theoretical calculations.

  1. Synthesis of amino functionalized magnetic graphenes composite material and its application to remove Cr(VI), Pb(II), Hg(II), Cd(II) and Ni(II) from contaminated water.

    PubMed

    Guo, Xiaoyao; Du, Bin; Wei, Qin; Yang, Jian; Hu, Lihua; Yan, Liangguo; Xu, Weiying

    2014-08-15

    In the present study, a kind of graphenes magnetic material (Fe3O4-GS) was prepared by compositing graphene sheet with ferroferric oxide, and shown to be effective for removing Cr(VI), Pb(II), Hg(II), Cd(II) and Ni(II) ions from aqueous solution. The synthesized sorbent was characterized by SEM, TEM, FTIR, XRD, XPS and BET, respectively. The pHZPC value of the sorbent was estimated to be 3.5 by alkaline-titration methods. Fe3O4-GS can be simply recovered from water with magnetic separation at low magnetic field within one minute. The sorption capacities of the metals were 17.29, 27.95, 23.03, 27.83 and 22.07 mg g(-1) for Cr(VI), Pb(II), Hg(II), Cd(II) and Ni(II), respectively. Kinetic data showed good correlation with pseudo-second-order equation and the Freundlich model was found to fit for the isotherm data of all the heavy metal ions. It was found that the metals sorption was accomplished mainly via chelation or ion exchange. The results of thermodynamic studies illustrate that the adsorption process was endothermic and spontaneous in nature. PMID:25016452

  2. Calculations of photo-induced X-ray production cross-sections in the energy range 1-150 keV and average fluorescence yields for Zn, Cd and Hg

    NASA Astrophysics Data System (ADS)

    Sampaio, J. M.; Guerra, M.; Parente, F.; Madeira, T. I.; Indelicato, P.; Santos, J. P.; Marques, J. P.

    2016-09-01

    In this paper, we calculate the K-, L- and M-shells X-ray production, and X-ray fluorescence cross-sections after photo-induced ionization, for Zn, Cd, and Hg, and for incident photon energy range from 1 to 150 keV. For this purpose, the corresponding average fluorescence yields for Zn, Cd, and Hg as well as the photoionization cross-sections were calculated using the Dirac-Fock method. Subshell fluorescence, intrashell and intershell yields are obtained consistently from radiative and radiationless transitions calculated in the exact same method. A comprehensive account of the relations between the X-ray production, X-ray fluorescence cross-sections and the photoionization cross-sections and these yields is presented. Comparisons are made with results from other authors. The obtained values for the photoionization cross-sections are in good agreement with the widely used data of Scofield in the studied energy range. However our results for the X-ray fluorescence cross sections seem to favor some data relatively to others. The energy dependence of the average fluorescence yields is discussed, in particular, the reliability of extrapolated data for lighter elements from measurements and calculations in heavier elements above the inner shell absorption edges is questioned. Tabulated data on photoionization and X-ray production cross-sections are presented for the incident photon energy range 1-150 keV in steps of 1 keV.

  3. Molecular structures, charge distributions, and vibrational analyses of the tetracoordinate Cu(II), Zn(II), Cd(II), and Hg(II) bromide complexes of p-toluidine investigated by density functional theory in comparison with experiments

    NASA Astrophysics Data System (ADS)

    Bardakçı, Tayyibe; Kumru, Mustafa; Altun, Ahmet

    2016-07-01

    The Cu(II), Zn(II), Cd(II), and Hg(II) bromide complexes of p-toluidine have been studied with B3LYP calculations by using def2-TZVP basis set at the metal atoms and using def2-TZVP and 6-311G+(d,p) basis sets at the remaining atoms. Both basis set combinations give analogous results, which validate the use of quickly converging 6-311G+(d,p) basis set in future studies. The molecular structures, atomic charge and spin distributions, and harmonic vibrational frequencies of the complexes have been calculated. The Zn, Cd and Hg complexes have been found to have distorted tetrahedral environments around the metal atoms whereas Cu complex has a square planar geometry. The NBO charge analysis have been found more accurate and less misleading compared with the Mulliken scheme. The present vibrational spectra calculations allow accurate assignment of the vibrational bands, which otherwise assigned tentatively in previous experimental-only studies.

  4. Synthesis, spectroscopic, antimicrobial and DNA cleavage studies of new Co(II), Ni(II), Cu(II), Cd(II), Zn(II) and Hg(II) complexes with naphthofuran-2-carbohydrazide Schiff base

    NASA Astrophysics Data System (ADS)

    Halli, Madappa B.; Sumathi, R. B.

    2012-08-01

    A series of Co(II), Ni(II), Cu(II), Cd(II), Zn(II) and Hg(II) complexes have been synthesized with newly synthesized Schiff base derived from naphthofuran-2-carbohydrazide and cinnamaldehyde. The elemental analyses of the complexes are confined to the stoichiometry of the type MLCl2 [M = Co(II) and Cu(II)], ML2Cl2 [M = Ni(II), Cd(II), Zn(II) and Hg(II)] respectively, where L is Schiff base ligand. Structures have been proposed from elemental analyses, IR, electronic, mass, 1H NMR, ESR spectral data, magnetic, and thermal studies. The measured low molar conductance values in DMF indicate that the complexes are non-electrolytes. Spectroscopic studies suggest coordination occurs through azomethine nitrogen and carbonyl oxygen of the ligand with the metal ions. The Schiff base and its complexes have been screened for their antibacterial (Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Salmonella typhi) and antifungal (Aspergillus niger, Aspergillus flavus, Cladosporium and Candida albicans) activities by minimum inhibitory concentration (MIC) method. The DNA cleavage studies by agarose gel electrophoresis method was studied for all the complexes.

  5. Calculations of photo-induced X-ray production cross-sections in the energy range 1-150 keV and average fluorescence yields for Zn, Cd and Hg

    NASA Astrophysics Data System (ADS)

    Sampaio, J. M.; Guerra, M.; Parente, F.; Madeira, T. I.; Indelicato, P.; Santos, J. P.; Marques, J. P.

    2016-09-01

    In this paper, we calculate the K-, L- and M-shells X-ray production, and X-ray fluorescence cross-sections after photo-induced ionization, for Zn, Cd, and Hg, and for incident photon energy range from 1 to 150 keV. For this purpose, the corresponding average fluorescence yields for Zn, Cd, and Hg as well as the photoionization cross-sections were calculated using the Dirac-Fock method. Subshell fluorescence, intrashell and intershell yields are obtained consistently from radiative and radiationless transitions calculated in the exact same method. A comprehensive account of the relations between the X-ray production, X-ray fluorescence cross-sections and the photoionization cross-sections and these yields is presented. Comparisons are made with results from other authors. The obtained values for the photoionization cross-sections are in good agreement with the widely used data of Scofield in the studied energy range. However our results for the X-ray fluorescence cross sections seem to favor some data relatively to others. The energy dependence of the average fluorescence yields is discussed, in particular, the reliability of extrapolated data for lighter elements from measurements and calculations in heavier elements above the inner shell absorption edges is questioned. Tabulated data on photoionization and X-ray production cross-sections are presented for the incident photon energy range 1-150 keV in steps of 1 keV.

  6. Synthesis of amino functionalized magnetic graphenes composite material and its application to remove Cr(VI), Pb(II), Hg(II), Cd(II) and Ni(II) from contaminated water.

    PubMed

    Guo, Xiaoyao; Du, Bin; Wei, Qin; Yang, Jian; Hu, Lihua; Yan, Liangguo; Xu, Weiying

    2014-08-15

    In the present study, a kind of graphenes magnetic material (Fe3O4-GS) was prepared by compositing graphene sheet with ferroferric oxide, and shown to be effective for removing Cr(VI), Pb(II), Hg(II), Cd(II) and Ni(II) ions from aqueous solution. The synthesized sorbent was characterized by SEM, TEM, FTIR, XRD, XPS and BET, respectively. The pHZPC value of the sorbent was estimated to be 3.5 by alkaline-titration methods. Fe3O4-GS can be simply recovered from water with magnetic separation at low magnetic field within one minute. The sorption capacities of the metals were 17.29, 27.95, 23.03, 27.83 and 22.07 mg g(-1) for Cr(VI), Pb(II), Hg(II), Cd(II) and Ni(II), respectively. Kinetic data showed good correlation with pseudo-second-order equation and the Freundlich model was found to fit for the isotherm data of all the heavy metal ions. It was found that the metals sorption was accomplished mainly via chelation or ion exchange. The results of thermodynamic studies illustrate that the adsorption process was endothermic and spontaneous in nature.

  7. Studies of the spin Hamiltonian parameters and defect structures for Ag2+ in NaF and CsCdF3 crystals

    NASA Astrophysics Data System (ADS)

    Zhang, Li-Juan; Wu, Shao-Yi; Ding, Chang-Chun; Hu, Xian-Fen; He, Jia-Jun

    2016-03-01

    The spin Hamiltonian parameters (g factors g//, g⊥, hyperfine structure constants A//, A⊥ and superhyperfine parameters Az‧, Ax‧ and Ay‧) and defect structures for Ag2+ in NaF and CsCdF3 crystals are theoretically studied using the improved perturbation formulas of these quantities for a 4d9 ion in a tetragonally elongated octahedron. The contributions from both the crystal-field and charge transfer mechanisms are taken into account, and the relevant model parameters are quantitatively obtained from the cluster approach in a consistent way. The impurity centers are found to undergo the relative tetragonal elongations of about 9.4% and 8.2% for Ag2+ in NaF and CsCdF3, respectively, along the C4 axis due to the Jahn-Teller effect. By employing the few adjustable parameters, the calculated spin Hamiltonian parameters based on the above uniform formulas and the local tetragonal elongation distortions agree well with the experimental data. Despite dominant ionicity of the hosts, the charge transfer contributions are actually important to the spin Hamiltonian parameters (e.g., about 20% for the g-shifts) due to strong covalency of impurity Ag2+.

  8. Fluorometric sensing of ultralow As(III) concentrations using Ag doped hollow CdS/ZnS bi-layer nanoparticles.

    PubMed

    Boxi, Siddhartha Sankar; Paria, Santanu

    2015-12-21

    Arsenic poisoning from drinking water has been an important global issue in recent years. Because of the high level toxicity of arsenic to human health, an easy, inexpensive, low level and highly selective detection technique is of great importance to take any early precautions. This study reports the synthesis of Ag doped hollow CdS/ZnS bi-layer (Ag-h-CdS/ZnS) nanoparticles for the easy fluorometric determination of As(iii) ions in the aqueous phase. The hollow bi-layer structures were synthesized by a sacrificial core method using AgBr as the sacrificial core and the core was removed by dissolution in an ammonium hydroxide solution. The synthesized nanoparticles were characterized using different instrumental techniques. A good linear relationship was obtained between fluorescence quenching intensity and As(iii) concentration in the range of 0.75-22.5 μg L(-1) at neutral pH with a limit of detection as low as 0.226 μg L(-1). PMID:26541652

  9. Effects of metal-bearing nanoparticles (Ag, Au, CdS, ZnO, SiO2) on developing zebrafish embryos.

    PubMed

    Lacave, José María; Retuerto, Ander; Vicario-Parés, Unai; Gilliland, Douglas; Oron, Miriam; Cajaraville, Miren P; Orbea, Amaia

    2016-08-12

    Due to the increasing commercialization of consumer and industrial products containing nanoparticles (NPs), an increase in the introduction of these materials into the environment is expected. NP toxicity to aquatic organisms depends on multiple biotic and abiotic factors, resulting in an unlimited number of combinations impossible to test in practice. The zebrafish embryo model offers a useful screening tool to test and rank the toxicity of nanomaterials according to those diverse factors. This work aims to study the acute and sublethal toxicity of a set of metal-bearing NPs displaying different properties, in comparison to that of the ionic and bulk forms of the metals, in order to establish a toxicity ranking. Soluble NPs (Ag, CdS and ZnO) showed the highest acute and sublethal toxicity, with LC50 values as low as 0.529 mg Ag l(-1) for Ag NPs of 20 nm, and a significant increase in the malformation prevalence in embryos exposed to 0.1 mg Cd l(-1) of CdS NPs of ∼4 nm. For insoluble NPs, like SiO2 NPs, acute effects were not observed during early embryo development due to the protective effect of the chorion. But effects on larvae could be expected, since deposition of fluorescent SiO2 NPs over the gill lamella and excretion through the intestine were observed after hatching. In other cases, such as for gold NPs, the toxicity could be attributed to the presence of additives (sodium citrate) in the NP suspension, as they displayed a similar toxicity when tested separately. Overall, the results indicated that toxicity to zebrafish embryos depends primarily on the chemical composition and, thus, the solubility of the NPs. Other characteristics, such as size, played a secondary role. This was supported by the observation that ionic forms of the metals were always more toxic than the nano forms, and bulk forms were the least toxic to the developing zebrafish embryos. PMID:27363512

  10. Effects of metal-bearing nanoparticles (Ag, Au, CdS, ZnO, SiO2) on developing zebrafish embryos

    NASA Astrophysics Data System (ADS)

    María Lacave, José; Retuerto, Ander; Vicario-Parés, Unai; Gilliland, Douglas; Oron, Miriam; Cajaraville, Miren P.; Orbea, Amaia

    2016-08-01

    Due to the increasing commercialization of consumer and industrial products containing nanoparticles (NPs), an increase in the introduction of these materials into the environment is expected. NP toxicity to aquatic organisms depends on multiple biotic and abiotic factors, resulting in an unlimited number of combinations impossible to test in practice. The zebrafish embryo model offers a useful screening tool to test and rank the toxicity of nanomaterials according to those diverse factors. This work aims to study the acute and sublethal toxicity of a set of metal-bearing NPs displaying different properties, in comparison to that of the ionic and bulk forms of the metals, in order to establish a toxicity ranking. Soluble NPs (Ag, CdS and ZnO) showed the highest acute and sublethal toxicity, with LC50 values as low as 0.529 mg Ag l‑1 for Ag NPs of 20 nm, and a significant increase in the malformation prevalence in embryos exposed to 0.1 mg Cd l‑1 of CdS NPs of ∼4 nm. For insoluble NPs, like SiO2 NPs, acute effects were not observed during early embryo development due to the protective effect of the chorion. But effects on larvae could be expected, since deposition of fluorescent SiO2 NPs over the gill lamella and excretion through the intestine were observed after hatching. In other cases, such as for gold NPs, the toxicity could be attributed to the presence of additives (sodium citrate) in the NP suspension, as they displayed a similar toxicity when tested separately. Overall, the results indicated that toxicity to zebrafish embryos depends primarily on the chemical composition and, thus, the solubility of the NPs. Other characteristics, such as size, played a secondary role. This was supported by the observation that ionic forms of the metals were always more toxic than the nano forms, and bulk forms were the least toxic to the developing zebrafish embryos.

  11. Effects of metal-bearing nanoparticles (Ag, Au, CdS, ZnO, SiO2) on developing zebrafish embryos

    NASA Astrophysics Data System (ADS)

    María Lacave, José; Retuerto, Ander; Vicario-Parés, Unai; Gilliland, Douglas; Oron, Miriam; Cajaraville, Miren P.; Orbea, Amaia

    2016-08-01

    Due to the increasing commercialization of consumer and industrial products containing nanoparticles (NPs), an increase in the introduction of these materials into the environment is expected. NP toxicity to aquatic organisms depends on multiple biotic and abiotic factors, resulting in an unlimited number of combinations impossible to test in practice. The zebrafish embryo model offers a useful screening tool to test and rank the toxicity of nanomaterials according to those diverse factors. This work aims to study the acute and sublethal toxicity of a set of metal-bearing NPs displaying different properties, in comparison to that of the ionic and bulk forms of the metals, in order to establish a toxicity ranking. Soluble NPs (Ag, CdS and ZnO) showed the highest acute and sublethal toxicity, with LC50 values as low as 0.529 mg Ag l-1 for Ag NPs of 20 nm, and a significant increase in the malformation prevalence in embryos exposed to 0.1 mg Cd l-1 of CdS NPs of ˜4 nm. For insoluble NPs, like SiO2 NPs, acute effects were not observed during early embryo development due to the protective effect of the chorion. But effects on larvae could be expected, since deposition of fluorescent SiO2 NPs over the gill lamella and excretion through the intestine were observed after hatching. In other cases, such as for gold NPs, the toxicity could be attributed to the presence of additives (sodium citrate) in the NP suspension, as they displayed a similar toxicity when tested separately. Overall, the results indicated that toxicity to zebrafish embryos depends primarily on the chemical composition and, thus, the solubility of the NPs. Other characteristics, such as size, played a secondary role. This was supported by the observation that ionic forms of the metals were always more toxic than the nano forms, and bulk forms were the least toxic to the developing zebrafish embryos.

  12. The effect of TiO{sub 2} and Ag nanoparticles on reproduction and development of Drosophila melanogaster and CD-1 mice

    SciTech Connect

    Philbrook, Nicola A.; Winn, Louise M.; Afrooz, A.R.M. Nabiul; Saleh, Navid B.; Walker, Virginia K.

    2011-12-15

    In the last two decades, nanoparticles (NPs) have found applications in a wide variety of consumer goods. Titanium dioxide (TiO{sub 2}) and silver (Ag) NPs are both found in cosmetics and foods, but their increasing use is of concern due to their ability to be taken up by biological systems. While there are some reports of TiO{sub 2} and Ag NPs affecting complex organisms, their effects on reproduction and development have been largely understudied. Here, the effects of orally administered TiO{sub 2} or Ag NPs on reproduction and development in two different model organisms were investigated. TiO{sub 2} NPs reduced the developmental success of CD-1 mice after a single oral dose of 100 or 1000 mg/kg to dams, resulting in a statistically significant increase in fetal deformities and mortality. Similarly, TiO{sub 2} NP addition to food led to a significant progeny loss in the fruit fly, Drosophila, as shown by a decline in female fecundity. Ag NP administration resulted in an increase in the mortality of fetal mice. Similarly in Drosophila, Ag NP feeding led to a significant decrease in developmental success, but unlike TiO{sub 2} NP treatment, there was no decline in fecundity. The distinct response associated with each type of NP likely reflects differences in NP administration as well as the biology of the particular model. Taken together, however, this study warns that these common NPs could be detrimental to the reproductive and developmental health of both invertebrates and vertebrates.

  13. Uncertainty evaluation in the analysis of biological samples by sector field inductively coupled plasma mass spectrometry. Part A: Measurements of Be, Cd, Hg, Ir, Pb, Pd, Pt, Rh, Sb, U, Tl and W in human serum.

    PubMed

    Bocca, Beatrice; Mattei, Daniela; Pino, Anna; Alimonti, Alessandro

    2010-08-30

    A protocol that utilises data (trueness/recovery, precision and robustness) from validation tests to calculate measurement uncertainty was described and applied to a sector field inductively coupled plasma mass spectrometry (SF-ICP-MS)-based method for the determination of Be, Cd, Hg, Ir, Pb, Pd, Pt, Rh, Sb, U, Tl and W in human serum. The method was validated according to criteria issued by international bodies such as AOAC, Eurachem and ISO and the uncertainty in the analytical measurements was estimated following the Eurachem/Citac guide. The methodology was based on dilution of human serum with water and analysis by serum-matched standard calibration. The method quantification limits ranged 0.02 microg/L (Tl, Ir) to 0.26 microg/L (Hg). The coefficients of regression were greater than 0.9991 over a range of two orders of magnitude of concentration. The mean trueness was 101% and the mean recovery on three levels of fortification (1-, 1.5-, and 2-times the baseline serum level) ranged between 93.3% and 106%. The maximum relative standard deviation values for repeatability and within-laboratory reproducibility were 12.8% and 13.5%. The method was robust to slight variations of some critical factors relevant to the sample preparation and SF-ICP-MS instrumentation. The relative expanded uncertainty over three levels of concentration ranged from 11.6% (Hg) to 27.6% (Pt), and the uncertainty on the within-laboratory reproducibility, which included factors such as time, analyst and calibration, represented the main contribution to the overall uncertainty.

  14. Temperature dependence of the carrier lifetime in Cd{sub x}Hg{sub 1−x}Te narrow-gap solid solutions with consideration for Auger processes

    SciTech Connect

    Bazhenov, N. L. Mynbaev, K. D.; Zegrya, G. G.

    2015-04-15

    The temperature dependence of the carrier lifetime in Cd{sub x}Hg{sub 1−x}Te narrow-gap solid solutions in the temperature range 5 K < T < 300 K is analyzed within the scope of a microscopic model. Main attention is given to an analysis of the Auger recombination mechanism governing the carrier lifetime at high temperatures. The Auger-recombination rates are calculated with consideration for specific features of the band structure of the narrow-gap semiconductor in microscopic theory. It is shown that strict account of the non-parabolicity of the electronic structure in terms of Kane’s model leads to a substantially different temperature dependence of the Auger-recombination rates, compared with the approach in which nonparabolicity is disregarded.

  15. Optical and magneto-optical effects in Hg{sub 1-x}Cd{sub x}Cr{sub 2}Se{sub 4} (0 ⩽ x ⩽ 1) single crystals

    SciTech Connect

    Sukhorukov, Yu. P. Telegin, A. V.; Bebenin, N. G.; Zainullina, R. I.; Mostovshchikova, E. V.; Viglin, N. A.; Gan’shina, E. A.; Zykov, G. S.; Fedorov, V. A.; Menshchikova, T. K.; Buchkevich, A. A.

    2015-09-15

    The concentration, temperature, and magnetic-field dependences of the magnetoreflection and magnetotransmission of natural light in the infrared spectral range and the Kerr effect in single crystals of ferromagnetic Hg{sub 1-x}Cd{sub x}Cr{sub 2}Se{sub 4} (0 ⩽ x ⩽ 1) spinels have been studied. A relationship of the magneto-optical properties to the electronic band structure of spinels has been established. The most significant changes in the spectra of magnetoreflection, magnetotransmission, and the Kerr effect are shown to be observed for 0.1 < x < 0.25 and are attributable to a rearrangement of the band structure as the composition changes.

  16. Effect of annealing on the kinetic properties and band parameters of Hg{sub 1−x−y}Cd{sub x}Eu{sub y}Se semiconductor crystals

    SciTech Connect

    Kovalyuk, T. T. Maistruk, E. V.; Maryanchuk, P. D.

    2014-12-15

    The results of studies of the kinetic properties of Hg{sub 1−x−y}Cd{sub x}Eu{sub y}Se semiconductor crystals in the ranges of temperatures T = 77–300 K and magnetic fields H = 0.5–5 kOe before and after heat treatment of the samples in Se vapors are reported. It is established that annealing of the samples in Se vapors induces a decrease in the electron concentration. From the concentration dependence of the electron effective mass at the Fermi level, the band gap, the matrix element of interband interaction, and the electron effective mass at the bottom of the conduction band are determined.

  17. A change in the electro-physical properties of narrow-band CdHgTe solid solutions acted upon by a volume discharge induced by an avalanche electron beam in the air at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Voitsekhovskii, A. V.; Grigor'ev, D. V.; Korotaev, A. G.; Kokhanenko, A. P.; Tarasenko, V. F.; Shulepov, M. A.

    2012-03-01

    The effect of a nanosecond volume discharge forming in an inhomogeneous electrical field at atmospheric pressure on the CdHgTe (MCT) epitaxial films of the p-type conduction with the hole concentration 2·1016 cm3 and mobility 500 cm2·V-1·s-1 is studied. The measurement of the electrophysical parameters of the MCT specimens upon irradiation shows that a layer exhibiting the n-type conduction is formed in the near-surface region of the epitaxial films. After 600 pulses and more, the thickness and the parameters of the layer are such that the measured field dependence of the Hall coefficient corresponds to the material of the n-type conduction. Analysis of the preliminary results reveals that the foregoing nanosecond volume discharge in the air at atmospheric pressure is promising for modification of electro-physical MCT properties.

  18. Identification of complexes containing glutathione with As(III), Sb(III), Cd(II), Hg(II), Tl(I), Pb(II) or Bi(III) by electrospray ionization mass spectrometry.

    PubMed

    Burford, Neil; Eelman, Melanie D; Groom, Katherine

    2005-10-01

    Electrospray ionization mass spectrometry (ESI-MS) of mixtures containing glutathione (GSH) and nitrates, oxides or chlorides of the heavy metals, arsenic, antimony, cadmium, mercury, thallium, lead or bismuth allows for definitive identification of complexes in the gas phase. In the positive ion mode, spectra show prominent m/z peaks that are assigned to monocations of general formulae [E(GSH)-xH]+ (E = Cd, Hg, Tl, Pb, As, Sb or Bi; x = 0, 1 or 2), [E(GSH)2-xH]+ (E = Hg, As, Sb, or Bi; x = 1 or 2), [E(GSH)3-xH]+ (E = As, Sb or Bi; x = 2), [E2(GSH)-xH]+ (E = Tl or Pb; x = 1 or 3), [E2(GSH)2-xH]+ (E = Bi; x = 5), [E2(GSH)3-xH]+ (E = Bi; x = 5), and/or [E3(GSH)-xH]+ (E = Tl; x = 2). Spectra obtained in the negative ion mode give m/z peaks observed in assigned to monoanionic species that correspond to some of the monocationic species listed above with two protons removed. The results demonstrate the potential application of ESI-MS as a versatile and efficient approach to study toxic heavy metals in biological systems. In addition, the observations provide a foundation database to understand the chemistry of these heavy metals with bio-molecules.

  19. Theoretical Studies on the Fe-M Interactions and 31P NMR in Fe(CO)3(EtPhPpy)2MX2 (X = NCS, SCN, Cl; M = Zn, Cd, Hg)

    NASA Astrophysics Data System (ADS)

    Huang, Xiao-xuan; Xu, Xuan; Xie, Mei-xiang

    2008-10-01

    To study the Fe-M interactions and their effects on 31P NMR, the structures of Fe(CO)3(EtPhPpy)2 1, Fe(CO)3(EtPhPpy)2M(NCS)2 (2: M = Zn, 3: M = Cd, 4: M = Hg) and Fe(CO)3(EtPhPpy)2CdX2 (5: X = C1, 6: X = SCN) were investigated by density functional theory (DFT) PBE0 method. The stabilities S of complexes follow S(2)>S(3)>S(4) and S(3)approxS(6)>S(5), indicating that 6 is stable and may be synthesized. The complexes with thiocyanate are more stable than that with chloride in Fe(CO)3(EtPhPpy)2CdX2. The strength / of Fe-M interactions follows I(2)approxI(3)Cd interactions of 3 and 6, which contain thiocyanate, are stronger than that of 5 with chloride. The charge-transfer, which enhances with the increasing of Fe-M interaction strength, comes from Et, Ph, py, CO groups towards P, Fe, and M atoms. Because the delocalization of thiocyanate disperses the charge of M2+, the charge-transfer of the complexes with thiocyanate is stronger than that with chloride. There is a σ-bond between Fe and Hg atoms in 4. However, in binuclear complexes except 4, the Fe-M interactions act as nFe→nm, σ-Fe→nM and σc-Fe→nM delocalization, and the N-M interactions mainly act as nN→nm delocalization. In binuclear complexes, due to the Fe→M interactions, the strong σFe-c→σ*Fe-P or σFe_Hg→σ*Fe-p delocalization and the charge-transfer, the electron density on P nucleus is increased, and thus upfield 31P chemical shifts are caused (compared with mononuclear complex 1).

  20. Pirquitasite, Ag2ZnSnS4

    PubMed Central

    Schumer, Benjamin N.; Downs, Robert T.; Domanik, Kenneth J.; Andrade, Marcelo B; Origlieri, Marcus J.

    2013-01-01

    Pirquitasite, ideally Ag2ZnSnS4 (disilver zinc tin tetra­sulfide), exhibits tetra­gonal symmetry and is a member of the stannite group that has the general formula A2BCX 4, with A = Ag, Cu; B = Zn, Cd, Fe, Cu, Hg; C = Sn, Ge, Sb, As; and X = S, Se. In this study, single-crystal X-ray diffraction data are used to determine the structure of pirquitasite from a twinned crystal from the type locality, the Pirquitas deposit, Jujuy Province, Argentina, with anisotropic displacement parameters for all atoms, and a measured composition of (Ag1.87Cu0.13)(Zn0.61Fe0.36Cd0.03)SnS4. One Ag atom is located on Wyckoff site Wyckoff 2a (symmetry -4..), the other Ag atom is statistically disordered with minor amounts of Cu and is located on 2c (-4..), the (Zn, Fe, Cd) site on 2d (-4..), Sn on 2b (-4..), and S on general site 8g. This is the first determination of the crystal structure of pirquitasite, and our data indicate that the space group of pirquitasite is I-4, rather than I-42m as previously suggested. The structure was refined under consideration of twinning by inversion [twin ratio of the components 0.91 (6):0.09 (6)]. PMID:23424398

  1. Use of ZnO:Tb down-conversion phosphor for Ag nanoparticle plasmon absorption using a He-Cd ultraviolet laser.

    PubMed

    Abbass, A E; Swart, H C; Kroon, R E

    2016-09-01

    Although noble metal nanoparticles (NPs) have attracted some attention for potentially enhancing the luminescence of rare earth ions for phosphor lighting applications, the absorption of energy by NPs can also be beneficial in biological and polymer applications where local heating is desired, e.g. photothermal applications. Strong interaction between incident laser light and NPs occurs only when the laser wavelength matches the NP plasmon resonance. Although lasers with different wavelengths are available and the NP plasmon resonance can be tuned by changing its size and shape or the dielectric medium (host material), in this work, we consider exciting the plasmon resonance of Ag NPs indirectly with a He-Cd UV laser using the down-conversion properties of Tb(3+) ions in ZnO. The formation of Ag NPs was confirmed by X-ray diffraction, transmission electron microscopy and UV-vis diffuse reflectance measurements. Radiative energy transfer from the Tb(3+) ions to the Ag NPs resulted in quenching of the green luminescence of ZnO:Tb and was studied by means of spectral overlap and lifetime measurements. The use of a down-converting phosphor, possibly with other rare earth ions, to indirectly couple a laser to the plasmon resonance wavelength of metal NPs is therefore successfully demonstrated and adds to the flexibility of such systems. Copyright © 2016 John Wiley & Sons, Ltd.

  2. A highly selective and sensitive fluorescent sensor for the rapid detection of Hg2 + based on phenylamine-oligothiophene derivative

    NASA Astrophysics Data System (ADS)

    Niu, Qingfen; Wu, Xingxing; Zhang, Shanshan; Li, Tianduo; Cui, Yuezhi; Li, Xiaoyan

    2016-01-01

    A fast-responsive fluorescent phenylamine-oligothiophene sensor 3TDDA was reported. This sensor exhibited highly selective and sensitive detection of Hg2 + ion in aqueous solution (THF/CH3CN/H2O, 45/50/5, v/v) through fluorescence quenching. The detection was not affected by the coexistence of other competitive metal ions such as Na+, K+, Ag+, Ca2 +, Fe3 +, Al3 +, Co2 +, Ni2 +, Zn2 +, Pb2 +, Cd2 +, Fe2 + and Cr3 +. A stoichiometric ratio (1:1) of the sensor and Hg2 + was determined by a Job's plot and mole-ratio curves. The binding of sensor 3TDDA and Hg2 + was also chemically reversible with EDTA. The detection limit was calculated as low as 4.392 × 10- 7 M.

  3. Preparation, spectroscopic, thermal, antihepatotoxicity, hematological parameters and liver antioxidant capacity characterizations of Cd(II), Hg(II), and Pb(II) mononuclear complexes of paracetamol anti-inflammatory drug

    NASA Astrophysics Data System (ADS)

    El-Megharbel, Samy M.; Hamza, Reham Z.; Refat, Moamen S.

    2014-10-01

    Keeping in view that some metal complexes are found to be more potent than their parent drugs, therefore, our present paper aimed to synthesized Cd(II), Hg(II) and Pb(II) complexes of paracetamol (Para) anti-inflammatory drug. Paracetamol complexes with general formula [M(Para)2(H2O)2]·nH2O have been synthesized and characterized on the basis of elemental analysis, conductivity, IR and thermal (TG/DTG), 1H NMR, electronic spectral studies. The conductivity data of these complexes have non-electrolytic nature. Comparative antimicrobial (bacteria and fungi) behaviors and molecular weights of paracetamol with their complexes have been studied. In vivo the antihepatotoxicity effect and some liver function parameters levels (serum total protein, ALT, AST, and LDH) were measured. Hematological parameters and liver antioxidant capacities of both Para and their complexes were performed. The Cd2+ + Para complex was recorded amelioration of antioxidant capacities in liver homogenates compared to other Para complexes treated groups.

  4. Effect of Ar and N{sub 2} addition on CH{sub 4}-H{sub 2} based chemistry inductively coupled plasma etching of HgCdTe

    SciTech Connect

    Boulard, F.; Baylet, J.; Cardinaud, C.

    2009-07-15

    Mercury cadmium telluride (MCT) CH{sub 4}-H{sub 2} based chemistry inductively coupled plasma (ICP) etching mechanisms are investigated. The effect of Ar and N{sub 2} addition in the mixture on plasma and MCT surface characteristics are studied by Langmuir probe, mass spectrometry, and x-ray photoelectron spectroscopy (XPS). In the authors' conditions, the HgTe faster removal than CdTe leads to the formation of a CdTe rich layer in the first 30 s of plasma exposure. Ion flux intensity and composition are only slightly influenced by N{sub 2} addition while a strong effect is shown on neutral species by the formation of NH{sub 3}, HCN, and the increase in CH{sub 3} radical density. At the opposite, Ar addition to the gas mixture leads to a total ion flux increase and promote CH{sub 3}{sup +} formation while small changes are observed on neutral species. In our low pressure and high density conditions, same order of magnitude of ion and neutral CH{sub 3} flux on MCT surface is found, suggesting a chemical contribution of CH{sub 3}{sup +} ions in MCT etching. This is confirmed by a strong correlation of the MCT etching yield versus total (neutral and ionic) CH{sub 3} flux. These results suggest that the etching is limited by the supply of CH{sub 3} to the surface.

  5. HgZnTe-based detectors for LWIR NASA applications

    NASA Technical Reports Server (NTRS)

    Patten, Elizabeth A.; Kalisher, Murray H.

    1990-01-01

    The initial goal was to grow and characterize HgZnTe and determine if it indeed had the advantageous properties that were predicted. Researchers grew both bulk and liquid phase epitaxial HgZnTe. It was determined that HgZnTe had the following properties: (1) microhardness at least 50 percent greater than HgCdTe of equivalent bandgap; (2) Hg annealing rates of at least 2 to 4 times longer than HgCdTe; and (3) higher Hg vacancy formation energies. This early work did not focus on one specific composition (x-value) of HgZnTe since NASA was interested in HgZnTe's potential for a variety of applications. Since the beginning of 1989, researchers have been concentrating, however, on the liquid phase growth of very long wavelength infrared (VLWIR) HgZnTe (cutoff approx. equals 17 microns at 65K) to address the requirements of the Earth Observing System (EOS). Since there are no device models to predict the advantages in reliability one can gain with increased microhardness, surface stability, etc., one must fabricate HgZnTe detectors and assess their relative bake stability (accelerated life test behavior) compared with HgCdTe devices fabricated in the same manner. Researchers chose to fabricate HIT detectors as a development vehicle for this program because high performance in the VLWIR has been demonstrated with HgCdTe HIT detectors and the HgCdTe HIT process should be applicable to HgZnTe. HIT detectors have a significant advantage for satellite applications since these devices dissipate much less power than conventional photoconductors to achieve the same responsivity.

  6. Highly selective, sensitive and fast-responsive fluorescent sensor for Hg2 +

    NASA Astrophysics Data System (ADS)

    Niu, Qingfen; Wu, Xingxing; Li, Tianduo; Cui, Yuezhi; Zhang, Shanshan; Li, Xiaoyan

    2016-06-01

    A phenylamine-oligothiophene-based fluorescent sensor 2TBEA was reported. This sensor exhibited highly selective, sensitive and rapid detection of Hg2 + ion in THF/H2O (7/3, v/v) solution through fluorescence quenching. The detection was unaffected by the coexistence of other competitive metal cations including Na+, K+, Ag+, Ca2 +, Fe3 +, Al3 +, Co2 +, Cu2 +, Ni2 +, Zn2 +, Pb2 +, Cd2 +, Fe2 + and Cr3 +. A1:1 binding ratio for 2TBEA - Hg2 + was demonstrated by Job's plot and mole-ratio curves. The coordination process was chemically reversible with EDTA. The detection limit was evaluated to be as low as 6.164 × 10- 8 M.

  7. FAS -670 A/G polymorphism may be associated with the depletion of CD4(+) T lymphocytes in HIV-1 infection.

    PubMed

    Hermes, Renata Bezerra; Santana, Bárbara Brasil; Lima, Sandra Souza; Neris Martins Feitosa, Rosimar; de Oliveira Guimarães Ishak, Marluísa; Ishak, Ricardo; Vallinoto, Antonio Carlos Rosário

    2015-10-01

    In this study, the polymorphisms in the FAS and FASL genes was investigated in a sample of 198 HIV-1-seropositive individuals and 191 seronegative controls to evaluate a possible association between polymorphisms and the infection. The identification of the A and G alleles of the FAS -670 polymorphism was accomplished through polymerase chain reaction assays followed by digestion with the restriction enzyme MvaI. The identification of the A and G alleles of the FAS -124 polymorphism and the T and delT alleles of the FAS -169 polymorphism were performed using the amplification-created restriction site method followed by restriction fragment length polymorphism reactions. The comparative analysis of allelic and genotypic frequencies between the groups did not reveal any significant differences. However, the quantitative analysis of CD4(+) T lymphocytes suggests that the G allele of the FAS -670 A/G polymorphism can be a protective factor against the depletion of these cells in the course of an HIV-1 infection. Polymorphisms in the FAS and FASL genes were not associated with the number of CD8(+) T lymphocytes or the plasma viral load. Our findings suggest that the FAS -670 polymorphism may be associated with apoptosis of CD4(+) T lymphocytes after infection by HIV-1. PMID:26429326

  8. FAS -670 A/G polymorphism may be associated with the depletion of CD4(+) T lymphocytes in HIV-1 infection.

    PubMed

    Hermes, Renata Bezerra; Santana, Bárbara Brasil; Lima, Sandra Souza; Neris Martins Feitosa, Rosimar; de Oliveira Guimarães Ishak, Marluísa; Ishak, Ricardo; Vallinoto, Antonio Carlos Rosário

    2015-10-01

    In this study, the polymorphisms in the FAS and FASL genes was investigated in a sample of 198 HIV-1-seropositive individuals and 191 seronegative controls to evaluate a possible association between polymorphisms and the infection. The identification of the A and G alleles of the FAS -670 polymorphism was accomplished through polymerase chain reaction assays followed by digestion with the restriction enzyme MvaI. The identification of the A and G alleles of the FAS -124 polymorphism and the T and delT alleles of the FAS -169 polymorphism were performed using the amplification-created restriction site method followed by restriction fragment length polymorphism reactions. The comparative analysis of allelic and genotypic frequencies between the groups did not reveal any significant differences. However, the quantitative analysis of CD4(+) T lymphocytes suggests that the G allele of the FAS -670 A/G polymorphism can be a protective factor against the depletion of these cells in the course of an HIV-1 infection. Polymorphisms in the FAS and FASL genes were not associated with the number of CD8(+) T lymphocytes or the plasma viral load. Our findings suggest that the FAS -670 polymorphism may be associated with apoptosis of CD4(+) T lymphocytes after infection by HIV-1.

  9. Performance of 12- μm- to 15- μm-Pitch MWIR and LWIR HgCdTe FPAs at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Strong, Roger L.; Kinch, Michael A.; Armstrong, John M.

    2013-11-01

    Infrared (IR) focal-plane arrays (FPAs) with higher operating temperatures and smaller pitches enable reduced size, weight, and power in infrared systems. We have characterized a large number of medium- and long-wavelength IR (MWIR and LWIR) FPAs as a function of temperature and cutoff wavelength to determine the impact of these parameters on their performance. The 77-K cutoff wavelength range for the MWIR arrays was 5.0 μm to 5.6 μm, and 8.6 μm to 11.3 μm for the LWIR. The dark currents in DRS's high-density vertically integrated photodiode (HDVIP)® FPAs (based on a front-side- illuminated, via-interconnected, cylindrical-geometry N+/N/P architecture) are dominated by Auger-7 recombination from 120 K to 200 K for the MWIR and 70 K to 100 K for the LWIR. In these temperature ranges the FPA operability is generally limited not by dark current defects but by noise defects. Pixels with high 1/ f noise should produce a tail in the root-mean-square (rms) noise distribution. We have found that the skewness of the rms noise distribution is the simplest measure of an array's 1/ f noise, and that the rms noise skewness typically shows little variation over these temperature ranges. The temperature dependence of the defect counts in normal arrays (wet etched prior to CdTe interdiffusion) increases as n i, while nonstandard arrays (ion milled or plasma etched prior to CdTe interdiffusion) can have high 1/ f noise and defect counts that vary as n {i/2}. Our models indicate that, if the dominant dark current is due to diffusion, then the 1/ f noise varies as n {i/2}, whereas if depletion current dominates, then the 1/ f noise varies as n i. Systemic 1/ f noise is not an issue for DRS's standard MWIR FPAs at 110 K to 160 K, or for standard LWIR FPAs at 77 K to 100 K.

  10. Hg0 absorption in potassium persulfate solution*

    PubMed Central

    Ye, Qun-feng; Wang, Cheng-yun; Wang, Da-hui; Sun, Guan; Xu, Xin-hua

    2006-01-01

    The aqueous phase oxidation of gaseous elemental mercury (Hg0) by potassium persulfate (KPS) catalyzed by Ag+ was investigated using a glass bubble column reactor. Concentration of gaseous mercury and potassium persulfate were measured by cold vapor atom absorption (CVAA) and ion chromatograph (IC), respectively. The effects of pH value, concentration of potassium persulfate and silver nitrate (SN), temperature, Hg0 concentration in the reactor inlet and tertiary butanol (TBA), free radical scavenger, on the removal efficiency of Hg0 were studied. The results showed that the removal efficiency of Hg0 increased with increasing concentration of potassium persulfate and silver nitrate, while temperature and TBA were negatively effective. Furthermore, the removal efficiency of Hg0 was much better in neutral solution than in both acidic and alkaline solution. But the influence of pH was almost eliminated by adding AgNO3. High Hg0 concentration has positive effect. The possible reaction mechanism of gaseous mercury was also discussed. PMID:16615172

  11. Effect of the Graded-Gap Layer Composition on the Formation of n + -n - -p Structures in Boron-Implanted Heteroepitaxial Cd x Hg1- x Te Layers

    NASA Astrophysics Data System (ADS)

    Talipov, N. Kh.; Voitsekhovskii, А. V.; Grigor'ev, D. V.

    2014-07-01

    Processes of formation of n + -n--p-structures in boron-implanted heteroepitaxial (HEL) CdxHg1-xTe (CMT) layers of p-type grown by molecular beam epitaxy (HEL CMT MBE) with different compositions of the upper graded-gap layer are studied. It is shown that the surface composition (xs) of HEL CMT MBE significantly affects both the electrical parameters of the implanted layer and the spatial distribution of radiation defects of donor type. For HEL CMT MBE with the small surface composition xs = 0.22-0.33, it is found that the layer electron concentration (Ns) is decreased after saturation with accumulation of radiation defects, as the dose of B+ ions is increased in the range of D = 1ṡ1011-3ṡ1015 сm-2. An increase of the surface composition up to xs = 0.49-0.56 results in a significant decrease in Ns and a disappearance of the saturation of concentration in the whole dose range. The value of Ns monotonically increases with the energy (E) of boron ions and composition xs. It is found that for B+-ion energies E = 20-100 keV, the depth of the surface n + -layer increases with increasing energy and exceeds the total projected path of boron ions. However, in the energy range E = 100-150 keV, the depth of n+-layer stops increasing with the increase of the surface composition. The depth (dn) of a lightly doped n--layer monotonically decreases with increasing energy of boron ions in the entire range of E = 20-150 keV. With increasing dose (D) of B+ ions in the interval D = 1ṡ1014-1ṡ1015сm-2, deep n--layers with dn = 4-5 μm are formed only in the HEL CMT MBE with xs = 0.22-0.33. For the samples with xs = 0.49-0.56, the depth changes in the interval dn = 1.5-2.5 μm. At D ≤ 3ṡ1013сm-2, n + -n--p-structure is not formed for all surface compositions, if implantation is performed at room temperature. However, implantation at T = 130°C leads to the formation of a deep n--layer. Planar photodiodes with the n-p-junction area of A = 35×35 μm2 made on the basis of

  12. Approach to spatialize local to long-range atmospheric metal input (Cd, Cu, Hg, Pb) in epiphytic lichens over a meso-scale area (Pyrénées-Atlantiques, southwestern France).

    PubMed

    Barre, Julien P G; Deletraz, Gaëlle; Frayret, Jérôme; Pinaly, Hervé; Donard, Olivier F X; Amouroux, David

    2015-06-01

    Geographically based investigations into atmospheric bio-monitoring usually provide information on concentration or occurrence data and spatial trends of specific contaminants over a specified study area. In this work, an original approach based on geographic information system (GIS) was used to establish metal contents (Hg, Cu, Pb, and Cd) in epiphytic lichens from 90 locations as atmospheric bio-monitors over a meso-scale area (Pyrénées-Atlantiques, southwestern France). This approach allows the integration of the heterogeneity of the territory and optimization of the sampling sites based on both socioeconomical and geophysical parameters (hereafter defined as urban, industrial, agricultural, and forested areas). The sampling strategy was first evaluated in several sites (n = 15) over different seasons and years in order to follow the temporal variability of the atmospheric metal input in lichens. The results demonstrate that concentration ranges remain constant over different sampling periods in "rural" areas (agricultural and forested). Higher variability is observed in the "anthropized" urban and industrial areas in relation to local atmospheric inputs. In this context, metal concentrations in lichens over the whole study show that (1) Hg and Cd are homogeneous over the whole territory (0.14 ± 0.04 and 0.38 ± 0.26 mg/kg, respectively), whereas (2) Cu and Pb are more concentrated in "anthropized" areas (9.3 and 11.9 mg/kg, respectively) than in "rural" ones (6.8 and 6.0 mg/kg, respectively) (Kruskall-Wallis, K(Cu) = 13.7 and K(Pb) = 9.7, p < 0.00001). They also showed a significant local enrichment for all metals in many locations in the Pays Basque (West) mainly due to metal and steel industrial activities. This confirms the local contribution of this contamination source over a wider geographic scale. A multiple linear regression model was applied to give an integrated spatialization of the data. This showed significant

  13. Approach to spatialize local to long-range atmospheric metal input (Cd, Cu, Hg, Pb) in epiphytic lichens over a meso-scale area (Pyrénées-Atlantiques, southwestern France).

    PubMed

    Barre, Julien P G; Deletraz, Gaëlle; Frayret, Jérôme; Pinaly, Hervé; Donard, Olivier F X; Amouroux, David

    2015-06-01

    Geographically based investigations into atmospheric bio-monitoring usually provide information on concentration or occurrence data and spatial trends of specific contaminants over a specified study area. In this work, an original approach based on geographic information system (GIS) was used to establish metal contents (Hg, Cu, Pb, and Cd) in epiphytic lichens from 90 locations as atmospheric bio-monitors over a meso-scale area (Pyrénées-Atlantiques, southwestern France). This approach allows the integration of the heterogeneity of the territory and optimization of the sampling sites based on both socioeconomical and geophysical parameters (hereafter defined as urban, industrial, agricultural, and forested areas). The sampling strategy was first evaluated in several sites (n = 15) over different seasons and years in order to follow the temporal variability of the atmospheric metal input in lichens. The results demonstrate that concentration ranges remain constant over different sampling periods in "rural" areas (agricultural and forested). Higher variability is observed in the "anthropized" urban and industrial areas in relation to local atmospheric inputs. In this context, metal concentrations in lichens over the whole study show that (1) Hg and Cd are homogeneous over the whole territory (0.14 ± 0.04 and 0.38 ± 0.26 mg/kg, respectively), whereas (2) Cu and Pb are more concentrated in "anthropized" areas (9.3 and 11.9 mg/kg, respectively) than in "rural" ones (6.8 and 6.0 mg/kg, respectively) (Kruskall-Wallis, K(Cu) = 13.7 and K(Pb) = 9.7, p < 0.00001). They also showed a significant local enrichment for all metals in many locations in the Pays Basque (West) mainly due to metal and steel industrial activities. This confirms the local contribution of this contamination source over a wider geographic scale. A multiple linear regression model was applied to give an integrated spatialization of the data. This showed significant

  14. Metal-controlled assembly tuning the topology and dimensionality of coordination polymers of Ag(I), Cd(II) and Zn(II) with the flexible 2-(1 H-imidazole-1-yl)acetic acid (Hima)

    NASA Astrophysics Data System (ADS)

    Wang, Yong-Tao; Tang, Gui-Mei; Wu, Yue; Qin, Xu-Yan; Qin, Da-Wei

    2007-04-01

    Three new, inorganic-organic coordination polymers based on a versatile linking unit 2-(1 H-imidazole-1-yl)acetate (ima) and Ag I, Cd II and Zn II ions, exhibiting one to three dimensionalities and different topology structures, have been prepared in water medium and structurally characterized by single-crystal X-ray diffraction analysis. Reaction of AgNO 3 with Hima afforded a neutral one-dimensional (1-D) chains [Ag(ima)] n ( 1) which exhibits a pseudo two-dimensional (2-D) layered architecture through π-π stacking interaction between imidazole rings and intermolecular Ag⋯Ag interactions. Reaction of CdCl 2 with Hima yielded neutral 2-D coordination polymers [Cd(ima) 2] n ( 2) possessing (6, 3) topology structures, which further stack into 3-D supramolecular networks through C-H⋯O weak interactions. While Zn(NO 3) 2 was used, a non-centric 3-D coordination polymer [Zn(ima) 2] n ( 3) featuring a 3-fold interpenetrating diamondoid net was isolated. Among these polymers, the building block ima anion exhibits different coordination modes. These results indicate that the versatile nature of this flexible ligand, together with the coordination preferences of the metal ions, play a critical role in construction of these novel coordination polymers. The spectral, thermal and SHG (second-harmonic generation) properties of these new materials have also been investigated.

  15. Collective and noncollective states in Cd116 studied via the β decays of Ag116m1,m2,gs

    NASA Astrophysics Data System (ADS)

    Batchelder, J. C.; Wood, J. L.; Garrett, P. E.; Green, K. L.; Rykaczewski, K. P.; Bilheux, J.-C.; Bingham, C. R.; Carter, H. K.; Fong, D.; Grzywacz, R.; Hamilton, J. H.; Hartley, D. J.; Hwang, J. K.; Krolas, W.; Kulp, W. D.; Larochelle, Y.; Piechaczek, A.; Ramayya, A. V.; Spejewski, E. H.; Stracener, D. W.; Tantawy, M. N.; Winger, J. A.; Zganjar, E. F.

    2009-11-01

    We have reinvestigated the β decay of the three isomers of Ag116 at the Holifield Radioactive Ion Beam Facility (HRIBF). Through the use of half-life information, we have been able to construct individual decay schemes for each isomer and correct what was a puzzling inconsistency with the published data, namely the β feeding of 2+ states by a 5+ isomer. Our results indicate that the feeding of these levels arises from a 3+ isomer in Ag116. A total of 271γ-ray transitions (159 new) were assigned to 148 levels (94 new) from the β decay of Ag116m1,m2,gs. Significant deviations are observed from IBM-2 calculations for the decay of the 0+ and 2+ members of the previously assigned three-phonon quintuplet. Candidate states for the quadrupole-octupole quintuplet states and πg9/2-πp1/2, πg9/2-πp3/2, νh11/2-νs1/2, νh11/2-νd3/2, and νh11/2-νd5/2 broken-pair states are assigned.

  16. Fluorometric selective detection of fluoride ions in aqueous media using Ag doped CdS/ZnS core/shell nanoparticles.

    PubMed

    Boxi, Siddhartha Sankar; Paria, Santanu

    2016-01-14

    The presence of fluoride ions in drinking water plays an important role in human health. For that reason, maintaining the optimum concentration of fluoride ions in drinking water is essential, as both low and excess (above the permissible level) concentrations can cause different health problems, such as fluorosis, urolithiasis, kidney failure, cancer, and can even lead to death. So, development of a simple and low cost method for the detection of fluoride ions in water is highly desirable. In this study, a fluorometric method based on Ag-CdS/Ag-ZnS core/shell nanoparticles is developed for fluoride ion detection. The method was tested in aqueous solution at different pH values. The selectivity and sensitivity of the fluorescence probe was checked in the presence of other anions (Cl(-), Br(-), I(-), NO3(-) SO4(2-), HCO3(-), HPO4(2-), CH3COO(-), and H2PO4(-)) and found there is no significant interference of these associated ions. The fluoride ion concentration was varied in the range 190-22 800 μg L(-1) and a lower detection limit was obtained as 99.7 μg L(-1).

  17. Fluorometric selective detection of fluoride ions in aqueous media using Ag doped CdS/ZnS core/shell nanoparticles.

    PubMed

    Boxi, Siddhartha Sankar; Paria, Santanu

    2016-01-14

    The presence of fluoride ions in drinking water plays an important role in human health. For that reason, maintaining the optimum concentration of fluoride ions in drinking water is essential, as both low and excess (above the permissible level) concentrations can cause different health problems, such as fluorosis, urolithiasis, kidney failure, cancer, and can even lead to death. So, development of a simple and low cost method for the detection of fluoride ions in water is highly desirable. In this study, a fluorometric method based on Ag-CdS/Ag-ZnS core/shell nanoparticles is developed for fluoride ion detection. The method was tested in aqueous solution at different pH values. The selectivity and sensitivity of the fluorescence probe was checked in the presence of other anions (Cl(-), Br(-), I(-), NO3(-) SO4(2-), HCO3(-), HPO4(2-), CH3COO(-), and H2PO4(-)) and found there is no significant interference of these associated ions. The fluoride ion concentration was varied in the range 190-22 800 μg L(-1) and a lower detection limit was obtained as 99.7 μg L(-1). PMID:26645767

  18. Study of damage induced by room-temperature Al ion implantation in Hg{sub 0.8}Cd{sub 0.2}Te by x-ray diffuse scattering

    SciTech Connect

    Renault, P.O.; Declemy, A.; Leveque, P.; Fayoux, C.; Bessiere, M.; Lefebvre, S.; Corbel, C.; Baroux, L.

    1997-07-01

    Ion-implantation is a widely used doping technique in II{endash}VI semiconductors. Nevertheless, ion-implantation damage has to be better understood to properly control this process. In order to investigate the implantation-induced defects in such compounds, room-temperature implantations of 320 keV Al ions have been performed on crystalline samples of [111] Hg{sub 1{minus}x}Cd{sub x}Te (x{approx}20{percent}) for doses ranging from 10{sup 13} to 10{sup 15}cm{sup {minus}2}. We report the first measurements of x-ray diffuse scattering close to different Bragg reflections on such as-implanted samples. The evolution of the diffuse intensity as a function of the dose has been observed. The defect-induced diffuse intensity arises mainly from interstitial dislocation loops. Nevertheless, vacancy loops are observed above 3{times}10{sup 14}Al/cm{sup 2}. The mean radius of the dislocation loops increases in size by three to four times when the dose rises from 10{sup 13} to 10{sup 15}cm{sup {minus}2}. Finally, the saturation of point defects has been observed independently of their clustering at about 5{times}10{sup 13}Al/cm{sup 2}, that is in the same range as the saturation dose of the sheet electron concentration. {copyright} {ital 1997 American Institute of Physics.}

  19. A novel cellulose-dioctyl phthate-baker's yeast biosorbent for removal of Co(II), Cu(II), Cd(II), Hg(II) and Pb(II).

    PubMed

    Mahmoud, Mohamed E; Yakout, Amr A; Abed El Aziz, Marwa T; Osman, Maher M; Abdel-Fattah, Tarek M

    2015-01-01

    In this work, dioctyl phthalate (Dop) was used as a highly plasticizing material to coat and link the surface of basic cellulose (Cel) with baker's yeast for the formation of a novel modified cellulose biosorbent (Cel-Dop-Yst). Characterization was accomplished by Fourier Transform Infrared Spectroscopy (FT-IR), Thermogravimetric analysis (TGA) and Scanning Electron Microscope (SEM) measurements. The feasibility of using Cel-Dop-Yst biosorbent as an efficient material for removal of Co(II), Cu(II), Cd(II), Hg(II) and Pb(II) ions was explored using the batch equilibrium technique along with various experimental controlling parameters. The optimum pH values for removal of these metal ions were characterized in the range of 5.0-7.0. Cel-Dop-Yst was identified as a highly selective biosorbent for removal of the selected divalent metal ions. The Cel-Dop-Yst biosorbent was successfully implemented in treatment and removal of these divalent metal ions from industrial wastewater, sea water and drinking water samples using a multistage microcolumn technique. PMID:26121022

  20. Subcellular partitioning of non-essential trace metals (Ag, As, Cd, Ni, Pb, and Tl) in livers of American (Anguilla rostrata) and European (Anguilla anguilla) yellow eels.

    PubMed

    Rosabal, Maikel; Pierron, Fabien; Couture, Patrice; Baudrimont, Magalie; Hare, Landis; Campbell, Peter G C

    2015-03-01

    We determined the intracellular compartmentalization of the trace metals Ag, As, Cd, Ni, Pb, and Tl in the livers of yellow eels collected from the Saint Lawrence River system in Canada (Anguilla rostrata) and in the area of the Gironde estuary in France (Anguilla anguilla). Differential centrifugation, NaOH digestion and thermal shock were used to separate eel livers into putative "sensitive" fractions (heat-denatured proteins, mitochondria and microsomes+lysosomes) and detoxified metal fractions (heat-stable peptides/proteins and granules). The cytosolic heat-stable fraction (HSP) was consistently involved in the detoxification of all trace metals. In addition, granule-like structures played a complementary role in the detoxification of Ni, Pb, and Tl in both eel species. However, these detoxification mechanisms were not completely effective because increasing trace metal concentrations in whole livers were accompanied by significant increases in the concentrations of most trace metals in "sensitive" subcellular fractions, that is, mitochondria, heat-denatured cytosolic proteins and microsomes+lysosomes. Among these "sensitive" fractions, mitochondria were the major binding sites for As, Cd, Pb, and Tl. This accumulation of non-essential metals in "sensitive" fractions likely represents a health risk for eels inhabiting the Saint Lawrence and Gironde environments.

  1. An overwhelmingly selective colorimetric sensor for Ag(+) using a simple modified polyacrylonitrile fiber.

    PubMed

    Xing, Xiaoli; Yang, Huixiao; Tao, Minli; Zhang, Wenqin

    2015-10-30

    A carboxymethyl-dithiocarbamate immobilized polyacrylonitrile fiber colorimetric sensor has been synthesized. This fiber sensor exhibits excellent selectivity and sensitivity for Ag(+) in aqueous solution with a remarkable color change from light pink to red-brown over a wide pH range of 2-12. The sensor responds selectively to Ag(+) in the presence of other ions, including Mg(2+), Al(3+), Ca(2+), Cr(3+), Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+) and Pb(2+). The colorimetric sensor has an extremely fast response time (10s) and a low visual limit of detection (5.53×10(-12) mol/L). The fiber sensor also undergoes an obvious color change in the presence of Ag(+) solutions containing EDTA, NaCl or NaBr. Density functional theory optimization reveals that the sensor and Ag(+) interact via a seven-membered ring complexation mechanism.

  2. An overwhelmingly selective colorimetric sensor for Ag(+) using a simple modified polyacrylonitrile fiber.

    PubMed

    Xing, Xiaoli; Yang, Huixiao; Tao, Minli; Zhang, Wenqin

    2015-10-30

    A carboxymethyl-dithiocarbamate immobilized polyacrylonitrile fiber colorimetric sensor has been synthesized. This fiber sensor exhibits excellent selectivity and sensitivity for Ag(+) in aqueous solution with a remarkable color change from light pink to red-brown over a wide pH range of 2-12. The sensor responds selectively to Ag(+) in the presence of other ions, including Mg(2+), Al(3+), Ca(2+), Cr(3+), Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+) and Pb(2+). The colorimetric sensor has an extremely fast response time (10s) and a low visual limit of detection (5.53×10(-12) mol/L). The fiber sensor also undergoes an obvious color change in the presence of Ag(+) solutions containing EDTA, NaCl or NaBr. Density functional theory optimization reveals that the sensor and Ag(+) interact via a seven-membered ring complexation mechanism. PMID:25967097

  3. Atomic-level observation of Ag-ion hopping motion in AgI

    NASA Astrophysics Data System (ADS)

    Sato, W.; Komatsuda, S.; Mizuuchi, R.; Irioka, N.; Kawata, S.; Ohkubo, Y.

    2015-04-01

    Applicability of the 111mCd(→111Cd) and 111In(→111Cd) probes to the study of dynamics in polycrystalline silver iodide (AgI) was examined by means of the time-differential perturbed angular correlation technique. It was found that the 111mCd(→111Cd) probe occupies a unique site in γ-AgI and exhibits nuclear relaxation caused by dynamic perturbation arising from Ag + hopping motion in α-AgI; while the residential sites of 111In(→111Cd) vary, suggesting that 111In ions can not settle themselves in a fixed site in the AgI crystal structure. We here demonstrate that 111mCd(→111Cd) can be a potential nucleus to probe the Ag +-ion dynamic motion in α-AgI.

  4. Facile synthesis of ternary Ag/AgBr-Ag2CO3 hybrids with enhanced photocatalytic removal of elemental mercury driven by visible light.

    PubMed

    Zhang, Anchao; Zhang, Lixiang; Lu, Hao; Chen, Guoyan; Liu, Zhichao; Xiang, Jun; Sun, Lushi

    2016-08-15

    A novel technique for photocatalytic removal of elemental mercury (Hg(0)) using visible-light-driven Ag/AgBr-Ag2CO3 hybrids was proposed. The ternary Ag/AgBr-Ag2CO3 hybrids were synthesized by a simple modified co-precipitation method and characterized by N2 adsorption-desorption, scanning electron microscope (SEM), X-ray diffraction (XRD), UV-vis diffused reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) techniques. The effects of AgBr content, fluorescent lamp (FSL) irradiation, solution temperature, SO2 and NO on Hg(0) removal were investigated in detail. Furthermore, a possible reaction mechanism for higher Hg(0) removal was proposed, and the simultaneous removal of Hg(0), SO2 and NO was studied. The results showed that a high efficiency of Hg(0) removal was obtained by using Ag/AgBr-Ag2CO3 hybrids under fluorescent lamp irradiation. The AgBr content, FSL irradiation, solution temperature, and SO2 all exhibited significant effects on Hg(0) removal, while NO had slight effect on Hg(0) removal. The addition of Ca(OH)2 demonstrated a little impact on Hg(0) removal and could significantly improve the SO2-resistance performance of Ag/AgBr(0.7)-Ag2CO3 hybrid. The characterization results exhibited that hydroxyl radical (OH), superoxide radical (O2(-)), hole (h(+)), and Br(0), were reactive species responsible for removing Hg(0), and the h(+) played a key role in Hg(0) removal. PMID:27135702

  5. Non-bonding interactions and non-covalent delocalization effects play a critical role in the relative stability of group 12 complexes arising from interaction of diethanoldithiocarbamate with the cations of transition metals Zn(II), Cd(II), and Hg(II): a theoretical study.

    PubMed

    Bahrami, Homayoon; Farhadi, Saeed; Siadatnasab, Firouzeh

    2016-07-01

    The chelating properties of diethanoldithiocarbamate (DEDC) and π-electron flow from the nitrogen atom to the sulfur atom via a plane-delocalized π-orbital system (quasi ring) was studied using a density functional theory method. The molecular structure of DEDC and its complexes with Zn(II), Cd(II), and Hg(II) were also considered. First, the geometries of this ligand and DEDC-Zn(II), DEDC-Cd(II), and DEDC-Hg(II) were optimized, and the formation energies of these complexes were then calculated based on the electronic energy, or sum of electronic energies, with the zero point energy of each species. Formation energies indicated the DEDC-Zn(II) complex as the most stable complex, and DEDC-Cd(II) as the least stable. Structural data showed that the N1-C2 π-bond was localized in the complexes rather than the ligand, and a delocalized π-bond over S7-C2-S8 was also present. The stability of DEDC-Zn(II), DEDC-Cd(II), and DEDC-Hg(II) complexes increased in the presence of the non-specific effects of the solvent (PCM model), and their relative stability did not change. There was π-electron flow or resonance along N1-C2-S7 and along S7-C2-S8 in the ligand. The π-electron flow or resonance along N1-C2-S7 was abolished when the metal interacted with sulfur atoms. Energy belonging to van der Waals interactions and non-covalent delocalization effects between the metal and sulfur atoms of the ligand was calculated for each complex. The results of nucleus-independent chemical shift (NICS) indicated a decreasing trend as Zn(II) < Cd(II) < Hg(II) for the aromaticity of the quasi-rings. Finally, by ignoring van der Waals interactions and non-covalent delocalization effects between the metal and sulfur atoms of the ligand, the relative stability of the complexes was changed as follows:[Formula: see text] Graphical Abstract Huge electronic cloud localized on Hg(II) in the Hg(II)-DEDC complex. PMID:27299888

  6. Non-bonding interactions and non-covalent delocalization effects play a critical role in the relative stability of group 12 complexes arising from interaction of diethanoldithiocarbamate with the cations of transition metals Zn(II), Cd(II), and Hg(II): a theoretical study.

    PubMed

    Bahrami, Homayoon; Farhadi, Saeed; Siadatnasab, Firouzeh

    2016-07-01

    The chelating properties of diethanoldithiocarbamate (DEDC) and π-electron flow from the nitrogen atom to the sulfur atom via a plane-delocalized π-orbital system (quasi ring) was studied using a density functional theory method. The molecular structure of DEDC and its complexes with Zn(II), Cd(II), and Hg(II) were also considered. First, the geometries of this ligand and DEDC-Zn(II), DEDC-Cd(II), and DEDC-Hg(II) were optimized, and the formation energies of these complexes were then calculated based on the electronic energy, or sum of electronic energies, with the zero point energy of each species. Formation energies indicated the DEDC-Zn(II) complex as the most stable complex, and DEDC-Cd(II) as the least stable. Structural data showed that the N1-C2 π-bond was localized in the complexes rather than the ligand, and a delocalized π-bond over S7-C2-S8 was also present. The stability of DEDC-Zn(II), DEDC-Cd(II), and DEDC-Hg(II) complexes increased in the presence of the non-specific effects of the solvent (PCM model), and their relative stability did not change. There was π-electron flow or resonance along N1-C2-S7 and along S7-C2-S8 in the ligand. The π-electron flow or resonance along N1-C2-S7 was abolished when the metal interacted with sulfur atoms. Energy belonging to van der Waals interactions and non-covalent delocalization effects between the metal and sulfur atoms of the ligand was calculated for each complex. The results of nucleus-independent chemical shift (NICS) indicated a decreasing trend as Zn(II) < Cd(II) < Hg(II) for the aromaticity of the quasi-rings. Finally, by ignoring van der Waals interactions and non-covalent delocalization effects between the metal and sulfur atoms of the ligand, the relative stability of the complexes was changed as follows:[Formula: see text] Graphical Abstract Huge electronic cloud localized on Hg(II) in the Hg(II)-DEDC complex.

  7. Metal ion displacements in noncentrosymmetric chalcogenides La3Ga1.67S7, La3Ag0.6GaCh7 (Ch=S, Se), and La3MGaSe7 (M=Zn, Cd)

    NASA Astrophysics Data System (ADS)

    Iyer, Abishek K.; Yin, Wenlong; Rudyk, Brent W.; Lin, Xinsong; Nilges, Tom; Mar, Arthur

    2016-11-01

    The quaternary Ga-containing chalcogenides La3Ag0.6GaS7, La3Ag0.6GaSe7, La3ZnGaSe7, and La3CdGaSe7, as well as the related ternary chalcogenide La3Ga1.67S7, were prepared by reactions of the elements at 950 °C. They adopt noncentrosymmetric hexagonal structures (space group P63, Z=2) with cell parameters (a=10.2 Å, c=6.1 Å for the sulfides; a=10.6 Å, c=6.4 Å for the selenides) that are largely controlled by the geometrical requirements of one-dimensional stacks of Ga-centered tetrahedra separated by the La atoms. Among these compounds, which share the common formulation La3M1-xGaCh7 (M=Ga, Ag, Zn, Cd; Ch=S, Se), the M atoms occupy sites within a stacking of trigonal antiprisms formed by Ch atoms. The location of the M site varies between extremes with trigonal antiprismatic (CN6) and trigonal planar (CN3) geometry. Partial occupation of these sites and intermediate ones accounts for the considerable versatility of these structures and the occurrence of large metal displacement parameters. The site occupations can be understood in a simple way as being driven by the need to satisfy appropriate bond valence sums for both the M and Ch atoms. Band structure calculations rationalize the substoichiometry observed in the Ag-containing compounds (La3Ag0.6GaS7, La3Ag0.6GaSe7) as a response to overbonding. X-ray photoelectron spectroscopy supports the presence of monovalent Ag atoms in these compounds, which are not charge-balanced.

  8. Silica-coated magnetic nanoparticles modified with γ-mercaptopropyltrimethoxysilane for fast and selective solid phase extraction of trace amounts of Cd, Cu, Hg, and Pb in environmental and biological samples prior to their determination by inductively coupled plasma mass spectrometry

    NASA Astrophysics Data System (ADS)

    Huang, Chaozhang; Hu, Bin

    2008-03-01

    We report here the synthesis of a new sorbent comprising silica-coated magnetic nanoparticles (SCMNPs) modified with γ-mercaptopropyltrimethoxysilane (γ-MPTMS) for solid phase extraction of trace amounts of Cd, Cu, Hg, and Pb from biological and environmental samples. The prepared nanoparticles were characterized by infrared spectroscopy, transmission electron microscopy, and static adsorption-desorption experiments. These magnetic nanoparticles carrying the target metals could be easily separated from the aqueous solution simply by applying an external magnetic field; no filtration or centrifugation was necessary. Using this novel magnetic material, we have developed an efficient and cost-effective two-step method for detecting trace amounts of Cd, Cu, Hg, and Pb in environmental and biological samples. The first step of the method is a separation/preconcentration step, in which metals are adsorbed onto γ-MPTMS-SCMNPs. In the second step, inductively coupled plasma mass spectrometry is used to study the adsorbed metals. The effects of pH, sample volume, eluent, and interfering ions have been investigated. Under the optimized conditions, the limits of detection for Cd, Cu, Hg, and Pb were as low as 24, 92, 107, and 56 pg L - 1 , respectively. Relative standard deviations (RSDs, C = 2 ng L - 1 , n = 7) were 6.7%, 9.6%, 8.3%, and 3.7%, respectively.The proposed method has been validated using three certified reference materials, and it has been applied successfully in the determination of trace metals in biological and environmental samples.

  9. Rhodamine B immobilized on hollow Au-HMS material for naked-eye detection of Hg2+ in aqueous media.

    PubMed

    Zhang, Na; Li, Gang; Cheng, Zhuhong; Zuo, Xiujin

    2012-08-30

    A simple, effective method has been demonstrated to immobilize Rhodamine B (RhB) probes on mesoporous silica (Au-HMS). The prepared chemosensor (Au-HMS-Probe) was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), UV-vis spectrum and Fourier transform infrared spectroscopy (FT-IR). Further application of Au-HMS-Probe in sensing Hg(2+) was confirmed by fluorescence titration experiment. Au-HMS-Probe afforded "turn-on" fluorescence enhancement and displayed high brightness in water, and it also showed excellent selectivity for Hg(2+) over alkali (Na(+), K(+)), alkaline earth (Mg(2+), Ca(2+)) and other heavy metal ions (Ag(+), Cd(2+), Co(2+), Pb(2+), Ni(2+), Cu(2+), Fe(2+)). Importantly, Au-HMS-Probe could be regenerated by treatment with tetrapropylammonium hydroxide solution.

  10. Coumarin-based fluorescence hybrid silica material used for selective detection and absorption of Hg2+ in aqueous media

    NASA Astrophysics Data System (ADS)

    Meng, Qingtao; Jia, Hongmin; Wang, Cuiping; Zhao, Hongbin; Lu, Gonghao; Hu, Zhizhi; Zhang, Zhiqiang; Duan, Chunying

    2014-11-01

    An inorganic-organic hybrid fluorescence material (C-SBA-15) was prepared by covalent immobilization of a coumarin derivative within the channels of SBA-15. The characterization results of XRD, TEM micrographs, FT-IR and UV-vis demonstrate that coumarin is successfully grafted onto the inner surface of SBA-15 and its organized structure is preserved. C-SBA-15 can detect Hg2+ with high selectivity to Pb2+, Zn2+, Cu2+, Mn2+, Cd2+, Co2+, Ag+, Fe3+, Ni2+, K+, Na+, Ca2+, Mg2+ and Li+ in water. Furthermore, the fluorogenical response is reversible by treating with EDTA and do not vary over a broad pH range (5.0-10.5). C-SBA-15 features more outstanding absorbing capacity for Hg2+ among other HTM ions in water.

  11. Modification-free and N-acetyl-L-cysteine-induced colorimetric response of AuNPs: A mechanistic study and sensitive Hg(2+) detection.

    PubMed

    Tang, Jie; Wu, Peng; Hou, Xiandeng; Xu, Kailai

    2016-10-01

    A facile yet sensitive and selective method was proposed for Hg(2+) detection based on N-acetyl-L-cysteine(NAC)-induced colorimetric response of AuNPs. The proposed method can be easily performed by introducing the premixing of NAC and Hg(2+) into as-prepared citrate-capped AuNPs solution. A combination of experimental and theoretical studies was applied to illustrate the mechanism of this AuNPs colorimetric system. The strong interaction of NAC and AuNPs through Au-S bond could lead to the aggregation of AuNPs, but the formation of NAC-Hg-NAC complex decreased the affinity between NAC and AuNPs and resulted in an anti-aggregation effect. Therefore, the color of the AuNPs solution would progress from purple to red with the increase of Hg(2+) concentration. The proposed method had a high sensitivity with a limit of detection of 9.9nM. Coexistent metal ions, including Cd(2+), Mn(2+), Al(3+), Ag(+), K(+), Mg(2+), Ca(2+), Cr(3+), Cu(2+), Fe(3+), Pb(2+), Ni(2+) and Zn(2+), did not interfere with the detection of Hg(2+). This method can be used to monitor Hg(2+) in tap water. PMID:27474283

  12. Direct detection of Pb in urine and Cd, Pb, Cu, and Ag in natural waters using electrochemical sensors immobilized with DMSA functionalized magnetic nanoparticles

    SciTech Connect

    Yantasee, Wassana; Hongsirikarn, Kitiya; Warner, Cynthia L.; Choi, Daiwon; Sangvanich, Thanapon; Toloczko, Mychailo B.; Warner, Marvin G.; Fryxell, Glen E.; Addleman, Raymond S.; Timchalk, Chuck

    2008-03-01

    Urine is universally recognized as one of the best non-invasive matrices for biomonitoring exposure to a broad range of xenobiotics including toxic metals. For direct, simple, and field-deployable monitoring of urinary Pb, electrochemical sensors employing superparamagnetic iron oxide (Fe3O4) nanoparticles with a surface functionalization of dimercaptosuccinic acid (DMSA) has been developed. The metal detection involves rapid collection of dispersed metal-bound nanoparticles from a sample solution at a magnetic or electromagnetic electrode, followed by the stripping voltammetry of the metal in acidic medium. The sensors were evaluated as a function of solution pH, the binding affinity of Pb to DMSA-Fe3O4, the ratio of nanoparticles per sample volume, preconcentration time, and Pb concentrations. The effect of binding competitions between the DMSA-Fe3O4 and urine constituents for Pb on the sensor responses was studied. After 90s of preconcentration in samples containing 25 vol.% of rat urine and 0.1 g/L of DMSA-Fe3O4, the sensor could detect background level of Pb (< 1 ppb) and yielded linear responses from 0 to 50 ppb of Pb, excellent reproducibility (%R.S.D of 5.3 for seven measurements of 30 ppb Pb), and Pb concentrations comparable to those measured by ICP-MS. The sensor could also simultaneously detect background levels (< 1 ppb) of Cd, Pb, Cu, and Ag in river and seawater.

  13. Effects of increased pCO2 and temperature on trace element (Ag, Cd and Zn) bioaccumulation in the eggs of the common cuttlefish, Sepia officinalis

    NASA Astrophysics Data System (ADS)

    Lacoue-Labarthe, T.; Martin, S.; Oberhänsli, F.; Teyssié, J.-L.; Markich, S.; Jeffree, R.; Bustamante, P.

    2009-05-01

    Cephalopods play a key role in many marine trophic networks and constitute alternative fisheries resources, especially given the ongoing decline in finfish stocks. Along the European coast, the eggs of the cuttlefish Sepia officinalis are characterized by an increasing permeability of the eggshell during development, which leads to selective accumulation of essential and non-essential elements in the embryo. Temperature and pH are two critical factors that affect the metabolism of marine organisms in the coastal shallow waters. In this study, we are testing the effects of pH and temperature through a crossed (3×2) laboratory experiment. Seawater pH showed a strong effect on the egg weight and non-significant impact on the hatchlings weight at the end of development implying egg swelling process and embryo growth disturbances. The lower pH of incubation seawater of eggs, the more the hatchlings accumulated 110m Ag in their tissues. The 109Cd CF decreased with increasing pH and 65Zn CF reached the maximal values pH 7.85, independent of temperature. Our results suggest that pH and temperature affected both the permeability properties of the eggshell and the embryo metabolism. To the best of our knowledge, this is one of the first studies on the ocean acidification and ocean warming consequences on the metal uptake in marine organisms, stimulating further interest to evaluate the likely ecotoxicological impact of the global change on the early-life stage of the cuttlefish.

  14. Structural, spectral, thermal and biological studies on (Z)-N-benzoyl-N‧-(2-oxo-2-(phenylamino)acetyl)carbamohydrazonothioic acid (H2PABT) and its Cd(II), Hg(II), Zn(II) and U(VI)O22+ complexes

    NASA Astrophysics Data System (ADS)

    Yousef, T. A.; Ahmed, Sara F.; El-Gammal, O. A.; Abu El-Reash, G. M.

    2015-07-01

    A new metal complexes formed by the reaction of (Z)-N-benzoyl-N‧-(2-oxo-2-(phenylamino)acetyl)carbamohydrazonothioic acid (H2PABT) and Cd(II), Hg(II), Zn(II) and U(VI)O22+ ions. The isolated complexes were prepared and characterized by conventional techniques. The IR data revealed that the ligand behaves as mononegative tridentate in Zn(II) and U(VI)O22+ complexes also, binegative tetradentate on Cd(II) and Hg(II) complexes. On the basis of magnetic and electronic spectral data an octahedral geometry for the U(VI)O22+ complex, a tetrahedral structure for the Cd(II), Zn(II) and Hg(II) complexes have been proposed. The IR spectrum of ligand which determined experimentally is compared with those obtained theoretically from DFT calculations. Also, the bond lengths, bond angles, HOMO, LUMO and dipole moments have been calculated. The calculated HOMO-LUMO energy gap reveals that charge transfer occurs within the ligand molecules. The calculated values of binding energies indicates the stability of complexes is higher that of ligand. Also, the kinetic and thermodynamic parameters for the different thermal degradation steps of the complexes were determined by Coats-Redfern and Horowitz-Metzger methods. Moreover, the ligand and its complexes were screened against Bacillus subtilis as Gram positive bacteria and Escherichia coli Gram negative bacteria using the inhibitory zone diameter. Also the antitumor activities of the ligand and its complexes have been evaluated against liver (HePG2) and breast (MCF-7) cancer cells. Out of all the synthesized compounds, [Hg2(PABT)Cl2(H2O)2] and [(UO2)(HPABT)(OAc)(H2O)] complexes showed high antibacterial activity with 55.5% while H2PABT showed the best cytotoxic effect on liver and breast cancer cells with IC50 2.10 and 5.91 of cytotoxicity respectively.

  15. The -5 A/G single-nucleotide polymorphism in the core promoter region of MT2A and its effect on allele-specific gene expression and Cd, Zn and Cu levels in laryngeal cancer.

    PubMed

    Starska, Katarzyna; Krześlak, Anna; Forma, Ewa; Olszewski, Jurek; Morawiec-Sztandera, Alina; Aleksandrowicz, Paweł; Lewy-Trenda, Iwona; Bryś, Magdalena

    2014-10-15

    Metallothioneins (MTs) are low molecular weight, cysteine-rich heavy metal-binding proteins which participate in the mechanisms of Zn homeostasis, and protect against toxic metals. MTs contain metal-thiolate cluster groups and suppress metal toxicity by binding to them. The aim of this study was to determine the -5 A/G (rs28366003) single-nucleotide polymorphism (SNP) in the core promoter region of the MT2A gene and to investigate its effect on allele-specific gene expression and Cd, Zn and Cu content in squamous cell laryngeal cancer (SCC) and non-cancerous laryngeal mucosa (NCM) as a control. The MT2A promoter region -5 A/G SNP was determined by restriction fragment length polymorphism using 323 SCC and 116 NCM. MT2A gene analysis was performed by quantitative real-time PCR. The frequency of A allele carriage was 94.2% and 91.8% in SCC and NCM, respectively, while G allele carriage was detected in 5.8% and 8.2% of SCC and NCM samples, respectively. As a result, a significant association was identified between the -5 A/G SNP in the MT2A gene with mRNA expression in both groups. Metal levels were analyzed by flame atomic absorption spectrometry. The significant differences were identified between A/A and both the A/G and G/G genotypes, with regard to the concentration of the contaminating metal. The Spearman rank correlation results showed that the MT2A expression and Cd, Zn, Cu levels were negatively correlated. Results obtained in this study suggest that -5 A/G SNP in MT2A gene may have an effect on allele-specific gene expression and accumulation of metal levels in laryngeal cancer.

  16. Effects of increased pCO2 and temperature on trace element (Ag, Cd and Zn) bioaccumulation in the eggs of the common cuttlefish, Sepia officinalis

    NASA Astrophysics Data System (ADS)

    Lacoue-Labarthe, T.; Martin, S.; Oberhänsli, F.; Teyssié, J.-L.; Markich, S.; Ross, J.; Bustamante, P.

    2009-11-01

    Cephalopods play a key role in many marine trophic networks and constitute alternative fisheries resources, especially given the ongoing decline in finfish stocks. Along the European coast, the eggs of the cuttlefish Sepia officinalis are characterized by an increasing permeability of the eggshell during development, which leads to selective accumulation of essential and non-essential elements in the embryo. Temperature and pH are two critical factors that affect the metabolism of marine organisms in the coastal shallow waters. In this study, we investigated the effects of pH and temperature through a crossed (3×2; pH 8.1 (pCO2, 400 ppm), 7.85 (900 ppm) and 7.6 (1400 ppm) at 16 and 19°C, respectively) laboratory experiment. Seawater pH showed a strong effect on the egg weight and non-significant impact on the weight of hatchlings at the end of development implying an egg swelling process and embryo growth disturbances. The lower the seawater pH, the more 110 mAg was accumulated in the tissues of hatchlings. The 109Cd concentration factor (CF) decreased with decreasing pH and 65Zn CF reached maximal values pH 7.85, independently of temperature. Our results suggest that pH and temperature affected both the permeability properties of the eggshell and embryonic metabolism. To the best of our knowledge, this is one of the first studies on the consequences of ocean acidification and ocean warming on metal uptake in marine organisms, and our results indicate the need to further evaluate the likely ecotoxicological impact of the global change on the early-life stages of the cuttlefish.

  17. The − 5 A/G single-nucleotide polymorphism in the core promoter region of MT2A and its effect on allele-specific gene expression and Cd, Zn and Cu levels in laryngeal cancer

    SciTech Connect

    Starska, Katarzyna; Krześlak, Anna; Forma, Ewa; Morawiec-Sztandera, Alina; Aleksandrowicz, Paweł; Lewy-Trenda, Iwona; and others

    2014-10-15

    Metallothioneins (MTs) are low molecular weight, cysteine-rich heavy metal-binding proteins which participate in the mechanisms of Zn homeostasis, and protect against toxic metals. MTs contain metal-thiolate cluster groups and suppress metal toxicity by binding to them. The aim of this study was to determine the − 5 A/G (rs28366003) single-nucleotide polymorphism (SNP) in the core promoter region of the MT2A gene and to investigate its effect on allele-specific gene expression and Cd, Zn and Cu content in squamous cell laryngeal cancer (SCC) and non-cancerous laryngeal mucosa (NCM) as a control. The MT2A promoter region − 5 A/G SNP was determined by restriction fragment length polymorphism using 323 SCC and 116 NCM. MT2A gene analysis was performed by quantitative real-time PCR. The frequency of A allele carriage was 94.2% and 91.8% in SCC and NCM, respectively, while G allele carriage was detected in 5.8% and 8.2% of SCC and NCM samples, respectively. As a result, a significant association was identified between the − 5 A/G SNP in the MT2A gene with mRNA expression in both groups. Metal levels were analyzed by flame atomic absorption spectrometry. The significant differences were identified between A/A and both the A/G and G/G genotypes, with regard to the concentration of the contaminating metal. The Spearman rank correlation results showed that the MT2A expression and Cd, Zn, Cu levels were negatively correlated. Results obtained in this study suggest that − 5 A/G SNP in MT2A gene may have an effect on allele-specific gene expression and accumulation of metal levels in laryngeal cancer. - Highlights: • MT2A gene expression and metal content in laryngeal cancer tissues • Association between SNP (rs28366003) and expression of MT2A • Significant associations between the SNP and Cd, Zn and Cu levels • Negative correlation between MT2A gene expression and Cd, Zn and Cu levels.

  18. Hg-1212 and Hg-1223 single crystals: Synthesis and characterisation

    NASA Astrophysics Data System (ADS)

    Gatt, R.; Olsson, E.; Morawski, A.; Lada, T.; Paszewin, A.; Bryntse, I.; Grishin, A. M.; Eeltsev, Yu.; Berastegui, P.; Johansson, L.-G.

    1997-02-01

    Single crystals of HgBa 2CaCu 2O 6+δ (Hg-1212) and HgBa 2Ca 2Cu 3O 8+δ (Hg-1223) were grown from the melt at an argon pressure of 10 kbar. Electron microscopy, as well as single crystal X-ray diffraction studies show that the crystals are well ordered. The EDS analysis indicates the presence of a minor amount of other cations replacing Hg, Ba and Ca in the structure. Refined fractional coordinates and thermal parameters are given for a crystal of Hg-1223 type. Magnetic and resistive measurements show a Tc of 133 K for the Hg-1223 phase.

  19. Nondestructive Investigation of Heterojunction Interfacial Properties Using Two-Wavelength Raman Spectroscopy on Thin-Film CdS/CdTe Solar Cells.

    PubMed

    Zeng, Guanggen; Harrison, Paul; Kidman, Ali; Al-Mebir, Alaa; Feng, Lianghuan; Wu, Judy

    2016-09-01

    Raman spectra specific to CdS and CdTe were obtained on the CdS/CdTe heterojunction interface by employing two excitation wavelengths of λ1 = 488 nm and λ2 = 633 nm, respectively, from the glass side of Glass/FTO/CdS/CdTe/HgTe:Cu:graphite/Ag solar cells fabricated using pulsed-laser deposition (PLD). This two-wavelength Raman spectroscopy approach, with one wavelength selected below the absorption edge of the window layer (λ2 in this case), allows nondestructive characterization of the CdS/CdTe heterojunction and therefore correlation of the interfacial properties with the solar cell performance. In this study, the evolution of the interfacial strain relaxation during cell fabrication process was found to be affected not only by the inter-diffusion of S and Te corresponding to the formation of CdSxTe1-x ternary alloy with a various x from ∼0.01 to ∼0.067, but also by the variation in misfit dislocations (MDs) at CdS/CdTe interface from Raman TO/LO ratio ∼2.85 for as-deposited sample to TO/LO ∼4.44 for the cells post treatment. This is consistent with the change of the Urbach energy from 0.03 eV to 0.09 eV, indicative of the deterioration of crystalline quality of CdTe at interface although improved CdTe crystalline quality was observed away from the interface after the CdCl2 annealing. This difference crucially impacted on the rectification characteristics of the CdS/CdTe heterojunction and therefore the solar cell performance.

  20. M{sub 1-x}[W{sub 2}O{sub 2}X{sub 6}] with M=K{sup +}, Tl{sup +}, Ag{sup +}, Hg{sup 2+}, Pb{sup 2+}; X=Cl, Br-A class of mixed valence tungsten (IV,V) compounds with layered structures, W-W bonds and high conductivity

    SciTech Connect

    Beck, Johannes . E-mail: j.beck@uni-bonn.de; Kusterer, Christian; Hoffmann, Rolf-Dieter; Poettgen, Rainer

    2006-08-15

    The crystal structure of WOCl{sub 3}, determined on the basis of powder diffraction data (tetragonal, P4{sub 2}/mnm, a=10.6856(6), c=3.8537(2)), is isotypic to WOI{sub 3} and contains one-dimensional strands of edge-sharing double-octahedral W{sub 2}O{sub 4/2}Cl{sub 6} groups connected via common corners in trans position. A W-W bond of 2.99A is present within the planar W{sub 2}Cl{sub 6} groups. A series of non-stochiometric, mixed valence W(IV,V) compounds M{sub 1-x}[W{sub 2}O{sub 2}Cl{sub 6}] can be obtained from WOCl{sub 3} by reaction with metal halides (TlCl, KCl, PbCl{sub 2}) or by reaction of elemental Hg with WOCl{sub 4}. All were characterized by single crystal structure determinations and EDX measurements (Tl{sub 0.981(2)}[W{sub 2}O{sub 2}Cl{sub 6}]: monoclinic, C2/m, a=12.7050(4), b=3.7797(1), c=10.5651(3)A, {beta}=107.656(1){sup o}; K{sub 0.84(2)}[W{sub 2}O{sub 2}Cl{sub 6}]: monoclinic, C2/m, a=12.812(3), b=3.7779(6), c=10.196(3)A, {beta}=107.422(8){sup o}; Pb{sub 0.549(3)}[W{sub 2}O{sub 2}Cl{sub 6}]: orthorhombic, Immm,a=3.7659(1), b=9.8975(4), c=12.1332(6)A; Hg{sub 0.554(6)}[W{sub 2}O{sub 2}Cl{sub 6}]: monoclinic, C2/m, a=12.8361(8), b=3.7622(3), c=10.2581(9)A, {beta}=113.645(3){sup o}). Two representatives of this family of compounds have already been reported: Na[W{sub 2}O{sub 2}Br{sub 6}] [Y.-Q. Zhang, K. Peters, H.G. von Schnering, Z. Anorg. Allg. Chem. 624 (1998) 1415-1418] and Ag{sub 0.74}[W{sub 2}O{sub 2}Br{sub 6}] [S. Imhaine, C. Perrin, M. Sergent, Mat. Res. Bull. 33 (1998) 927-933]. The Ag containing compound can be obtained from elemental Ag and WOBr{sub 3}. The crystal structure, originally reported in the triclinic system, was redetermined and shown to be monoclinic with space group C2/m (a=13.7338(10), b=3.7769(3), c=10.7954(9)A, {beta}=112.401(3){sup o}). The crystal structures of these compounds are in close relationship to the structure of WOCl{sub 3} and all contain W{sub 2}O{sub 4/2}X{sub 6} (X=Cl, Br) double strands with the mono

  1. Methylmercury (MeHg)

    Integrated Risk Information System (IRIS)

    Methylmercury ( MeHg ) ; CASRN 22967 - 92 - 6 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarci

  2. Temperature- and frequency-dependent dielectric properties of organic–inorganic hybrid compound: (C{sub 6}H{sub 9}N{sub 2}){sub 2}(Hg{sub 0.75}Cd{sub 0.25})Cl{sub 4}

    SciTech Connect

    Elwej, R. Hamdi, M.; Hannachi, N.; Hlel, F.

    2015-02-15

    Highlights: • We have synthesized a new hybrid compound of composition (C6H9N2)2(Hg0.75Cd0.25)Cl4. • The Ac conductivity of the title material was studied as a function of frequency and temperature. • The dielectric data have been analyzed in modulus formalism using KWW. - Abstract: The bis-2-amino-4-picolinium tetrachloromercurate-cadmate compound (C{sub 6}H{sub 9}N{sub 2}){sub 2}(Hg{sub 0.75}Cd{sub 0.25})Cl{sub 4} was prepared by hydrothermal method and characterized by X-ray diffraction (XRD) technique. The electrical properties of the compound were studied using impedance spectroscopy in the frequency and temperature range of 200 Hz–5 MHz and 308–403 K, respectively. The equivalent circuit is modeled by a combination of a parallel Rp//CPE circuit to explain the impedance results. The dielectric data were analyzed using complex electrical modulus M* at various temperatures. The activation energy responsible for the relaxation calculated from the modulus spectra is found to be almost the same as the value obtained from the temperature variation of dc conductivity. The electrical modulus and its scaling behavior are also investigated.

  3. Hg(+) Frequency Standards

    NASA Technical Reports Server (NTRS)

    Prestage, John D.; Tjoelker, Robert L.; Maleki, Lute

    2000-01-01

    In this paper we review the development of Hg(+) microwave frequency standards for use in high reliability and continuous operation applications. In recent work we have demonstrated short-term frequency stability of 3 x 10(exp -14)/nu(sub tau) when a cryogenic oscillator of stability 2-3 x 10(exp 15) was used a the local oscillator. The trapped ion frequency standard employs a Hg-202 discharge lamp to optically pump the trapped Hg(+)-199 clock ions and a helium buffer gas to cool the ions to near room temperature. We describe a small Hg(+) ion trap based frequency standard with an extended linear ion trap (LITE) architecture which separates the optical state selection region from the clock resonance region. This separation allows the use of novel trap configurations in the resonance region since no optical pumping is carried out there. A method for measuring the size of an ion cloud inside a linear trap with a 12-rod trap is currently being investigated. At approx. 10(exp -12), the 2nd order Doppler shift for trapped mercury ion frequency standards is one of the largest frequency offsets and its measurement to the 1% level would represent an advance in insuring the very long-term stability of these standards to the 10(exp -14) or better level. Finally, we describe atomic clock comparison experiments that can probe for a time variation of the fine structure constant, alpha = e(exp 2)/2(pi)hc, at the level of 10(exp -20)/year as predicted in some Grand Unified String Theories.

  4. Complexation of Cd2+, Ni2+, and Ag+ metal ions with 4,13-didecyl-l,7,10,16-tetraoxa-4,13-diazacyclooctadecane in acetonitrile-ethylacetate binary mixtures

    NASA Astrophysics Data System (ADS)

    Izadyar, M.; Rounaghi, G. H.; Tarahomi, S.; Mohajeri, M.

    2013-12-01

    Conductometric titrations have been performed in acetonitrile-ethylacetate (AN-EtOAc) binary solutions at 288, 298, 308, and 318 K to obtain the stoichiometry, the complex stability constants and the standard thermodynamic parameters for the complexation of Cd2+, Ni2+, and Ag+ cations with 4,13-didecyl-1,7,10,16-tetraoxa-4,13-diazacyclooctadecane (cryptand 22DD). The stability constants of the resulting 1: 1 complexes formed between the metal cations and the ligand were determined by computer fitting of the conductance-mole ratio data. There is a non-linear relationship between the log K f values of complexes and the mole fraction of ethylacetate in the mixed solvent system. In addition, the conductometric data show that the stoichiometry of the complexes formed between the Cd2+, Ni2+, and Ag+ cations with the ligand changes with the nature of the solvent. The standard enthalpy and entropy values for the 1: 1 [ML] complexation reactions were evaluated from the temperature dependence of the formation constants. Thermodynamically, the complexation processes of the metal cations with the C22DD, is mainly entropy governed and the values of thermodynamic parameters are influenced by the nature and composition of the binary mixed solvent solutions.

  5. A first-principles study on the negative thermal expansion material: Mn3(A0.5B0.5)N (A=Cu, Zn, Ag, or Cd; B=Si, Ge, or Sn)

    NASA Astrophysics Data System (ADS)

    Qu, Bingyan; He, Haiyan; Pan, Bicai

    2016-07-01

    In this paper, using the first-principles calculations, we systemically study the magnetic and the negative thermal expansion (NTE) properties of Mn3(A0.5B0.5)N (A = Cu, Zn, Ag, or Cd; B = Si, Ge, or Sn). From the calculated results, except Mn3(Cu0.5Si0.5)N, all the doped compounds considered would exhibit the NTE. For the dopants at B sites, the working temperature of the NTE shifts to higher temperature range from Si to Sn, and among the compounds with these dopants, Mn3(A0.5Ge0.5)N has the largest amplitude of the NTE coefficient. As to the dopants at A sites, compared to Mn3(Cu0.5B0.5)N, Mn3(A0.5B0.5)N (A = Ag or Cd) exhibit the NTE with higher temperature ranges and lower coefficient of the thermal expansion. In a word, these compounds would have different working temperatures and coefficients of the NTE, which is important for the applications in different conditions.

  6. Admittance Investigation of MIS Structures with HgTe-Based Single Quantum Wells

    NASA Astrophysics Data System (ADS)

    Izhnin, Ihor I.; Nesmelov, Sergey N.; Dzyadukh, Stanislav M.; Voitsekhovskii, Alexander V.; Gorn, Dmitry I.; Dvoretsky, Sergey A.; Mikhailov, Nikolaj N.

    2016-02-01

    This work presents results of the investigation of admittance of metal-insulator-semiconductor structure based on Hg1 - x Cd x Te grown by molecular beam epitaxy. The structure contains a single quantum well Hg0.35Cd0.65Te/HgTe/Hg0.35Cd0.65Te with thickness of 5.6 nm in the sub-surface layer of the semiconductor. Both the conductance-voltage and capacitance-voltage characteristics show strong oscillations when the metal-insulator-semiconductor (MIS) structure with a single quantum well based on HgTe is biased into the strong inversion mode. Also, oscillations on the voltage dependencies of differential resistance of the space charge region were observed. These oscillations were related to the recharging of quantum levels in HgTe.

  7. Methylation of Hg downstream from the Bonanza Hg mine, Oregon

    USGS Publications Warehouse

    Gray, John E.; Hines, Mark E.; Krabbenhoft, David P.; Thoms, Bryn

    2012-01-01

    Speciation of Hg and conversion to methyl-Hg were evaluated in stream sediment, stream water, and aquatic snails collected downstream from the Bonanza Hg mine, Oregon. Total production from the Bonanza mine was >1360t of Hg, during mining from the late 1800s to 1960, ranking it as an intermediate sized Hg mine on an international scale. The primary objective of this study was to evaluate the distribution, transport, and methylation of Hg downstream from a Hg mine in a coastal temperate climatic zone. Data shown here for methyl-Hg, a neurotoxin hazardous to humans, are the first reported for sediment and water from this area. Stream sediment collected from Foster Creek flowing downstream from the Bonanza mine contained elevated Hg concentrations that ranged from 590 to 71,000ng/g, all of which (except the most distal sample) exceeded the probable effect concentration (PEC) of 1060ng/g, the Hg concentration above which harmful effects are likely to be observed in sediment-dwelling organisms. Concentrations of methyl-Hg in stream sediment collected from Foster Creek varied from 11 to 62ng/g and were highly elevated compared to regional baseline concentrations (0.11-0.82ng/g) established in this study. Methyl-Hg concentrations in stream sediment collected in this study showed a significant correlation with total organic C (TOC, R2=0.62), generally indicating increased methyl-Hg formation with increasing TOC in sediment. Isotopic-tracer methods indicated that several samples of Foster Creek sediment exhibited high rates of Hg-methylation. Concentrations of Hg in water collected downstream from the mine varied from 17 to 270ng/L and were also elevated compared to baselines, but all were below the 770ng/L Hg standard recommended by the USEPA to protect against chronic effects to aquatic wildlife. Concentrations of methyl-Hg in the water collected from Foster Creek ranged from 0.17 to 1.8ng/L, which were elevated compared to regional baseline sites upstream and downstream

  8. From Ag{sub 2}Sb{sub 2}O{sub 6} to Cd{sub 2}Sb{sub 2}O{sub 7}: Investigations on an anion-deficient to ideal pyrochlore solid solution

    SciTech Connect

    Laurita, Geneva; Vielma, Jason; Winter, Florian; Berthelot, Romain; Largeteau, Alain; Pöttgen, Rainer; Schneider, G.; Subramanian, M.A.

    2014-02-15

    A complete solid solution between the anion-deficient pyrochlore Ag{sub 2}Sb{sub 2}O{sub 6} and the ideal pyrochlore Cd{sub 2}Sb{sub 2}O{sub 7} has been synthesized through the standard solid state ceramic method. Each composition has been characterized by various different techniques, including powder X-ray diffraction, optical spectroscopy, electron paramagnetic resonance and {sup 121}Sb Mössbauer spectroscopy. Computational methods based on density functional theory complement this investigation. Photocatalytic activity has been studied, and transport properties have been measured on pellets densified by spark plasma sintering. The analysis of the data collected from these various techniques enables a comprehensive characterization of the complete solid solution and revealed an anomalous behavior in the Cd-rich end of the solid solution, which has been proposed to arise from a possible radical O{sup −} species in small concentrations. - Graphical abstract: A complete solid solution between the anion-deficient pyrochlore Ag{sub 2}Sb{sub 2}O{sub 6} and the ideal pyrochlore Cd{sub 2}Sb{sub 2}O{sub 7} has been synthesized and investigated through various techniques including X-ray diffraction, electron paramagnetic spectroscopy, and {sup 121}Sb-Mössbauer spectroscopy. Optical and electrical measurements have been performed, and computational methods have been applied to determine the density of states. Photocatalytic activity was monitored by the degradation of Methylene Blue, and upon cadmium substitution, the degradation amount decreased, which is attributed primarily to the changing optical and electrical properties of the solid solution. Display Omitted - Highlights: • A complete solid solution between Ag{sub 2}Sb{sub 2}O{sub 6} and Cd{sub 2}Sb{sub 2}O{sub 7} has been synthesized. • XRD reveals a relatively constant lattice parameter as the series progresses. • Optical and electrical properties have been measured for the solid solution.

  9. Reduction of Hg(II) to Hg(0) by magnetite.

    PubMed

    Wiatrowski, Heather A; Das, Soumya; Kukkadapu, Ravi; Ilton, Eugene S; Barkay, Tamar; Yee, Nathan

    2009-07-15

    Mercury (Hg) is a highly toxic element, and its contamination of groundwater presents a significant threat to terrestrial ecosystems. Understanding the geochemical processes that mediate mercury transformations in the subsurface is necessary to predict its fate and transport. In this study, we investigated the redox transformation of mercuric Hg (Hg[II]) in the presence of the Fe(II)/Fe(III) mixed valence iron oxide mineral magnetite. Kinetic and spectroscopic experiments were performed to elucidate reaction rates and mechanisms. The experimental data demonstrated that reaction of Hg(II) with magnetite resulted in the loss of Hg(II) and the formation of volatile elemental Hg (Hg[0]). Kinetic experiments showed that Hg(II) reduction occurred within minutes, with reaction rates increasing with increasing magnetite surface area (0.5 to 2 m2/L) and solution pH (4.8 to 6.7), and decreasing with increasing chloride concentration (10(-6) to 10(-2) mol/L). Mössbauer spectroscopic analysis of reacted magnetite samples revealed a decrease in Fe(II) content, corresponding to the oxidation of Fe(II) to Fe(III) in the magnetite structure. X-ray photoelectron spectroscopy detected the presence of Hg(II) on magnetite surfaces, implying that adsorption is involved in the electron transfer process. These results suggest that Hg(II) reaction with solid-phase Fe(II) is a kinetically favorable pathway for Hg(II) reduction in magnetite-hearing environmental systems.

  10. One-pot synthesis of two-sized clusters for ratiometric sensing of Hg2+.

    PubMed

    Chen, Tzu-Heng; Lu, Chi-Yu; Tseng, Wei-Lung

    2013-12-15

    This paper presents a discussion of a one-pot approach for preparing lyszoyme type VI (Lys VI) stabilized clusters, including small (Au7Ag and Au8) and large (Au24Ag) clusters, for ratiometric fluorescence sensing of Hg(2+). Our previous study (Chen and Tseng, Small 8 (2012) 1912) showed the formation of intermediate Au8 clusters in the conversion of Au(+)-Lys VI protein complexes to Au25 clusters. The presence of Ag(+) in the precursor solution slowed this conversion, thereby forming two-sized clusters. With an increase in Ag(+) content, a systematic blue shift in the first exciton absorption and fluorescence peaks indicated the formation of Au-Ag bimetallic clusters. The prepared Ag(+)/Au(3+) molar ratio of 2:8 resulted in the formation of two-sized clusters, with dual emission bands centered at 471 and 613 nm. After these clusters are separated by a membrane filter, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was used to determine the composition of Au24Ag clusters. By monitoring the intensity ratio of the two emission wavelengths, the solution consisting of Hg(2+)-insensitive small clusters (Au7Ag and Au8) and Hg(2+)-sensitive Au24Ag clusters exhibited a ratiometric fluorescence response toward Hg(2+), and provided a built-in correction for photobleaching; the limit of detection at a signal-to-noise ratio of three for Hg(2+) was estimated to be 1 nM. This probe was successfully applied to ratiometric fluorescence sensing of Hg(2+) in tap water. PMID:24209338

  11. Hg-Mask Coronagraph

    NASA Astrophysics Data System (ADS)

    Bourget, P.; Veiga, C. H.; Vieira Martins, R.; Assus, P.; Colas, F.

    In order to optimize the occulting process of a Lyot coronagraph and to provide a high dynamic range imaging, a new kind of occulting disk has been developed at the National Observatory of Rio de Janeiro. A mercury (Hg) drop glued onto an optical window by molecular cohesion and compressed by a pellicle film is used as the occulting disk. The minimum of the superficial tension potential function provides an optical precision (lambda/100) of the toric free surface of the mercury. This process provides a size control for the adaptation to the seeing conditions and to the apparent diameter of a resolved object, and in the case of adaptive optics, to the Airy diameter fraction needed. The occultation is a three dimensional process near the focal plane on the toric free surface that provides an apodization of the occultation. The Hg-Mask coronagraph has been projected for astrometric observations of faint satellites near to Jovian planets and works since 2000 at the 1.6 m telescope of the Pico dos Dias Observatory (OPD - Brazil).

  12. Efficient CO2 frequency doubling with Hg1-xCdxGa2S4

    NASA Astrophysics Data System (ADS)

    Ren, Deming; Huang, Jinzhe; Hu, Xiaoyong; Qu, Yanchen; Andreev, Yuri M.; Geiko, Pavel P.; Badikov, Valerii V.

    2004-02-01

    As it is known well, using of frequency doubling in differential absorption CO2 laser lidars increases the number of atmospheric gases under the control. Additional improvement in potential and gas analyses accuracy, technical and exploitation parameters has to be waited for with design of frequency doublers with more efficient nonlinear crystals. In this work for the first time detailed investigation results are represented on physial properties of new mixed nonlinear crystals grown in accordance with diagram HgGa2S4:CdGa2S4-->Hg1-xCdxGa2S4, phase-matching and potential efficiencies of second harmonic generation, so as on results of experimental investigation of TEA and mini TEA CO2 laser frequency doubling with it use. In spite of two time lower nonlinear susceptibility coefficients of both parent crystals in comparison with most efficient middle IR crystals high efficiency of frequency doubling is fixed in mixed crystals at room temperature. It is tree time in comparison with frequency doubling with, for example, popular ZnGeP2 and 5.5 time with AgGaSe2. These advantages are reached because realization of optimal non-critical phase-matching by choose of mixing ratio x=0.5, so as 2.3 time higher damage threshold, lower phonon absorption at CO2 laser wavelengths and lower meanings of refractive indexes at fundamental and second harmonic wavelengths. Exploitation parameters of mixed Hg1-xCdxGa2S4 crystal doublers are not worse than parameters of doublers with well-known crystals.

  13. Coordination of Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II), Pd(II) and Pt(II) with 2,5-hexanedione bis(thiosemicarbazone), HBTS: Crystal structure of cis-[Pd(HBTS)]Cl2 and 1-(2,5-dimethyl-1H-pyrrol-yl)-thiourea

    NASA Astrophysics Data System (ADS)

    Jeragh, Bakir; El-Asmy, Ahmed A.

    2014-09-01

    Metal complexes of Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, Pd2+ or Pt2+ with 2,5-hexanedione bis(thiosemicarbazone), HBTS; have been prepared and spectroscopically investigated. The empirical formulae of the complexes were suggested based on the elemental analysis. Single crystal of Pd(II) has been solved to be cis-form of square-planar geometry by the X-ray crystallography. 1H and 13C NMR spectra have been recorded for HBTS, Zn(II), Cd(II), Hg(II), Pd(II) and Pt(II) complexes, in DMSO-d6, showing the mode of chelation. The ligand acts as a neutral or a binegative tetradentate (N2S2) or neutral bidentate on the basis of FT-IR. The magnetic moments and electronic spectra provide information about the geometry of the complexes which supported by calculating the ligand field parameters for the Co(II) and Fe(III) complexes. The Ni(II) complex has subnormal magnetic moment (0.71 BM) indicative of a mixed stereochemistry of square-planar and tetrahedral structure. [Cu(HBTS-2H)] measured 0.93 BM indicating high interaction between the copper centers. The ligand may be ordered at the top of the spectrochemical series which giving high ligand field splitting energy (10Dq = 17,900 cm-1 for Co2+ complex). The mass spectra of some complexes proved their stable chemical formulae while the TGA depicts the degradation steps and the final residue. In evaporating the mother liquor during the preparation of HBTS, new compound is obtained naming 1-(2,5-dimethyl-1H-pyrrol-yl)thiourea and its crystal was solved.

  14. Coordination of Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II), Pd(II) and Pt(II) with 2,5-hexanedione bis(thiosemicarbazone), HBTS: crystal structure of cis-[Pd(HBTS)]Cl2 and 1-(2,5-dimethyl-1H-pyrrol-yl)-thiourea.

    PubMed

    Jeragh, Bakir; El-Asmy, Ahmed A

    2014-09-15

    Metal complexes of Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, Pd2+ or Pt2+ with 2,5-hexanedione bis(thiosemicarbazone), HBTS; have been prepared and spectroscopically investigated. The empirical formulae of the complexes were suggested based on the elemental analysis. Single crystal of Pd(II) has been solved to be cis-form of square-planar geometry by the X-ray crystallography. 1H and 13C NMR spectra have been recorded for HBTS, Zn(II), Cd(II), Hg(II), Pd(II) and Pt(II) complexes, in DMSO-d6, showing the mode of chelation. The ligand acts as a neutral or a binegative tetradentate (N2S2) or neutral bidentate on the basis of FT-IR. The magnetic moments and electronic spectra provide information about the geometry of the complexes which supported by calculating the ligand field parameters for the Co(II) and Fe(III) complexes. The Ni(II) complex has subnormal magnetic moment (0.71 BM) indicative of a mixed stereochemistry of square-planar and tetrahedral structure. [Cu(HBTS-2H)] measured 0.93 BM indicating high interaction between the copper centers. The ligand may be ordered at the top of the spectrochemical series which giving high ligand field splitting energy (10 Dq=17,900 cm(-1) for Co2+ complex). The mass spectra of some complexes proved their stable chemical formulae while the TGA depicts the degradation steps and the final residue. In evaporating the mother liquor during the preparation of HBTS, new compound is obtained naming 1-(2,5-dimethyl-1H-pyrrol-yl)thiourea and its crystal was solved.

  15. Collective and noncollective states in {sup 116}Cd studied via the {beta} decays of {sup 116}Ag{sup m1,m2,gs}

    SciTech Connect

    Batchelder, J. C.; Carter, H. K.; Spejewski, E. H.; Garrett, P. E.; Green, K. L.; Rykaczewski, K. P.; Bilheux, J.-C.; Stracener, D. W.; Bingham, C. R.; Fong, D.; Hamilton, J. H.; Hwang, J. K.; Ramayya, A. V.; Grzywacz, R.; Larochelle, Y.; Tantawy, M. N.; Hartley, D. J.; Krolas, W.

    2009-11-15

    We have reinvestigated the {beta} decay of the three isomers of {sup 116}Ag at the Holifield Radioactive Ion Beam Facility (HRIBF). Through the use of half-life information, we have been able to construct individual decay schemes for each isomer and correct what was a puzzling inconsistency with the published data, namely the {beta} feeding of 2{sup +} states by a 5{sup +} isomer. Our results indicate that the feeding of these levels arises from a 3{sup +} isomer in {sup 116}Ag. A total of 271{gamma}-ray transitions (159 new) were assigned to 148 levels (94 new) from the {beta} decay of {sup 116}Ag{sup m1,m2,gs}. Significant deviations are observed from IBM-2 calculations for the decay of the 0{sup +} and 2{sup +} members of the previously assigned three-phonon quintuplet. Candidate states for the quadrupole-octupole quintuplet states and {pi}g{sub 9/2}-{pi}p{sub 1/2}, {pi}g{sub 9/2}-{pi}p{sub 3/2}, {nu}h{sub 11/2}-{nu}s{sub 1/2}, {nu}h{sub 11/2}-{nu}d{sub 3/2}, and {nu}h{sub 11/2}-{nu}d{sub 5/2} broken-pair states are assigned.

  16. Electro-physical characteristics of MIS structures with HgTe- based single quantum wells

    NASA Astrophysics Data System (ADS)

    Dzyadukh, S.; Nesmelov, S.; Voitsekhovskii, A.; Gorn, D.

    2015-12-01

    The paper presents brief research results of the admittance of metal-insulator- semiconductor (MIS) structures based on Hg1-xCdxTe grown by molecular-beam epitaxy (MBE) method including single HgCdTe/HgTe/HgCdTe quantum wells (QW) in the surface layer. The thickness of a quantum well was 5.6 nm, and the composition of barrier layers with the thickness of 35 nm was close to 0.65. Measurements were conducted in the range of temperatures from 8 to 200 K. It is shown that for structure with quantum well based on HgTe capacitance and conductance oscillations in the strong inversion are observed. Also it is assumed these oscillations are related with the recharging of quantum levels in HgTe.

  17. Photochemical formation of CH 3HgH in Hg/CH 4/Ar matrices studied by FTIR spectroscopy

    NASA Astrophysics Data System (ADS)

    Legay-Sommaire, N.; Legay, F.

    1994-01-01

    Mixed matrices of methane or deuterated methane and argon doped with mercury have been irradiated with a KrF laser at 249 nm. Methylmercury hydride is formed by reaction of Hg excited to the 3P 1 state with CH 4 or CD 4. The reaction products were identified by Fourier transform infrared spectrometry.

  18. A rapid, partial leach and organic separation for the sensitive determination of Ag, Bi, Cd, Cu, Mo, Pb, Sb, and Zn in surface geologic materials by flame atomic absorption

    USGS Publications Warehouse

    Viets, J.G.; Clark, J.R.; Campbell, W.L.

    1984-01-01

    A solution of dilute hydrochloric acid, ascorbic acid, and potassium iodide has been found to dissolve weakly bound metals in soils, stream sediments, and oxidized rocks. Silver, Bi, Cd, Cu, Mo, Pb, Sb, and Zn are selectively extracted from this solution by a mixture of Aliquat 336 (tricaprylyl methyl ammonium chloride) and MIBK (methyl isobutyl ketone). Because potentially interfering major and minor elements do not extract, the organic separation allows interference-free determinations of Ag and Cd to the 0.05 ppm level, Mo, Cu, and Zn to 0.5 ppm, and Bi, Pb, and Sb to 1 ppm in the sample using flame atomic absorption spectroscopy. The analytical absorbance values of the organic solution used in the proposed method are generally enhanced more than threefold as compared to aqueous solutions, due to more efficient atomization and burning characteristics. The leaching and extraction procedures are extremely rapid; as many as 100 samples may be analyzed per day, yielding 800 determinations, and the technique is adaptable to field use. The proposed method was compared to total digestion methods for geochemical reference samples as well as soils and stream sediments from mineralized and unmineralized areas. The partial leach showed better anomaly contrasts than did total digestions. Because the proposed method is very rapid and is sensitive to pathfinder elements for several types of ore deposits, it should be useful for reconnaissance surveys for concealed deposits. ?? 1984.

  19. Electrochemical DNA probe for Hg(2+) detection based on a triple-helix DNA and Multistage Signal Amplification Strategy.

    PubMed

    Wang, Huan; Zhang, Yihe; Ma, Hongmin; Ren, Xiang; Wang, Yaoguang; Zhang, Yong; Wei, Qin

    2016-12-15

    In this work, an ultrasensitive electrochemical sensor was developed for detection of Hg(2+). Gold nanoparticles decorated bovine serum albumin reduction of graphene oxide (AuNP-BSA-rGO) were used as subsurface material for the immobilization of triple-helix DNA. The triple-helix DNA containing a thiol labelled single-stranded DNA (sDNA) and a thymine-rich DNA (T-rich DNA), which could be unwinded in the present of Hg(2+) to form more stable thymine-Hg(2+)-thymine (T-Hg(2+)-T) complex. T-Hg(2+)-T complex was then removed and the sDNA was left on the electrode. At this time, gold nanoparticle carrying thiol labelled cytosine-rich complementary DNA (cDNA-AuNP) could bind with the free sDNA. Meanwhile, the other free cDNA on AuNP could bind with each other in the present of Ag(+) to form the stable cytosine-Ag(+)-cytosine (C-Ag(+)-C) complex and circle amplification. Plenty of C-Ag(+)-C could form silver nanoclusters by electrochemical reduction and the striping signal of Ag could be measured for purpose of the final electrochemical detection of Hg(2+). This sensor could detect Hg(2+) over a wide concentration range from 0.1 to 130nM with a detection limit of 0.03nM.

  20. Chromo/Fluorogenic Detection of Co(2+), Hg(2+) and Cu(2+) by the Simple Schiff Base Sensor.

    PubMed

    Saleem, Muhammad; Khang, Chung Ho; Kim, Moon-Hwan; Lee, Ki Hwan

    2016-01-01

    Herein, we reported the ditriazole Schiff base derivative 1 and evaluated its photophysical properties on induction of varieties of metal ions including Na(+), Ag(+), Ni(2+), Mn(2+), Pd(2+), Co(2+), Hg(2+), Cu(2+), Pb(2+), Cd(2+), Zn(2+), Sn(2+), Fe(2+), Fe(3+), Cr(3+) and Al(3+), in order to figure out its potential as ion sensor. The ligand 1 exhibited the strong colorimetric change in the reaction solution as well as absorption spectral shifting with the concomitant appearance of well-defined isosbestic points only upon Co(2+), Hg(2+) and Cu(2+) addition corroborates its applicability as multichannel ion detector. The different extent of spectral shifting as well as unique chromogenic change in the probe solution upon Co(2+), Hg(2+) and Cu(2+) introduction can be used as the discrimination tool for these metal ions. The ligand-metal binding stoichiometry was assessed by their optical response which was further supported by the FT-IR, NMR and mass spectrometric analysis. The association constant and the detection limits of the ligand toward Co(2+), Hg(2+) and Cu(2+) ions were calculated to be 1.52 × 10(-8), 3.26 × 10(-9), 1.16 × 10(-8) and 3.87 × 10(-10), 5.47 × 10(-11), 8.91 × 10(-11) M, respectively, employing the Benesi-Hilderbrand equation and 3 σ slope(-1) methods. Furthermore, the successive addition of Co(2+), Hg(2+) and Cu(2+) induce the constant decline in the fluorescence emission signal intensity of the probe. The quenching efficiency of the probe upon metallic induction was fitted to the Stern-Volmer equation which yielded the upward curvature in case of all the three metals ions (Co(2+), Hg(2+) and Cu(2+)) when (Io/I-1) was plotted against the quencher concentration indicating the occurrence of both the dynamic and static quenching process in the system with the average Stern-Volmer quenching constant values of 9.25 × 10(-7), 1.14 × 10(-7), 1.829 × 10(-7), respectively.