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1

Growth of Zno Single Crystals.  

National Technical Information Service (NTIS)

Single crystals of ZnO have been grown by subliming both ZnS and ZnSe and reacting them with oxygen in an argon gas flow. Using ZnS as the starting material, both platelet- and prism-type ZnO crystals were grown. Prisms having a cross-sectional area in th...

Y. S. Park D. C. Reynolds

1966-01-01

2

Growth and characterization of large-diameter, lithium-free ZnO single crystals  

NASA Astrophysics Data System (ADS)

Large-diameter, lithium-free ZnO single-crystal substrates of high crystalline quality will enable development and commercialization of high-performance ZnO-based semiconductor devices, such as UV and visible light emitting diodes (LEDs), UV laser diodes and solar-blind UV detectors for variety of applications. We have recently developed a novel crystal growth technique for producing lithium-free ZnO single crystal boules of 1 inch in diameter. We also fabricated ZnO single crystal wafers in sizes up to 1 inch in diameter. Chemical purity, crystalline defects, and electrical resistivity of ZnO single crystals were analyzed. Results from crystal growth and material characterization are presented and discussed. Our research results suggest that the novel crystal growth technique is a viable production technique for producing ZnO single crystals and substrates for semiconductor device applications.

Wang, Shaoping; Kopec, Aneta; Timmerman, Andrew G.

2012-02-01

3

Surface chemistry and surface electronic properties of ZnO single crystals and nanorods  

SciTech Connect

The surface chemistry of ZnO single crystals of (0001) and (1010) orientations and ZnO nanorods was studied using x-ray and ultraviolet photoelectron spectroscopies. Air drying and UV-ozone preparations were studied in particular as chemical treatments that could be applied to poly(3-hexylthiophene) (P3HT)-ZnO solar cells to enhance performance. The UV-ozone treatment showed negligible effect by photoelectron spectroscopy on the ZnO single crystal surfaces, but brought about electronic shifts consistent with increased upward band bending by {approx}0.25 eV on the ZnO nanorod surface. Modest interface dipoles of {approx}0.15 and {approx}0.25 eV were measured between P3HT and the (1010) and (0001) single crystal orientations, respectively, with the dipole moment pointing from ZnO to the P3HT layer. The sol-gel films showed evidence of forming a small interface dipole in the opposite direction, which illustrates the difference in surface chemistry between the solution-grown ZnO and the ZnO single crystals.

Uhlrich, J. J.; Olson, D. C.; Hsu, J. W. P.; Kuech, T. F. [Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, Wisconsin 53706 (United States); Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, Wisconsin 53706 (United States)

2009-03-15

4

Growth of the 2-in-size bulk ZnO single crystals by the hydrothermal method  

Microsoft Academic Search

The hydrothermal method combined with a platinum inner container was applied to grow zinc oxide (ZnO) single crystals. High-purity and transparent single crystals with a large size of 505015mm3 were successfully grown. The higher crystallinity of the hydrothermally grown ZnO crystal compared with the commercial ZnO substrate grown by the chemical vapor transport method was confirmed by X-ray diffraction. The

Eriko Ohshima; Hiraku Ogino; Ikuo Niikura; Katsumi Maeda; Mitsuru Sato; Masumi Ito; Tsuguo Fukuda

2004-01-01

5

Photoelectrochemical Stability and Alteration Products of n-Type Single-Crystal ZnO Photoanodes  

SciTech Connect

The photoelectrochemical stability and surface-alteration characteristics of both doped and undoped n-type ZnO single-crystal photoanode electrodes have been investigated. The single-crystal ZnO photoanode properties were analyzed using current-voltage measurements plus spectral and time-dependent quantum-yield methods. These measurements revealed the presence of a distinct anodic peak and an accompanying cathodic surface degradation process at negative potentials. The features of this peak were found to depend on time as well as the NaOH concentration in the electrolyte, but they were independent of the presence of electrode illumination. Current measurements performed at the peak indicate that charging and discharging effects are apparently taking place at the semiconductor/electrolyte interface. This result is consistent with the significant reactive degradation that takes place on the ZnO single crystal photoanode surface and that ultimately leads to the reduction of the ZnO surface to Zn metal. The resulting Zn-metal reaction products create unusual, dendrite-like, surface alteration structural features that were analyzed using x-ray diffraction, energy-dispersive analysis, and scanning electron microscopy. The ZnO doping methods employed here are also shown to be an effective way of increasing the n-type character of the crystals. Higher doping levels result in smaller depletion widths and lower quantum yields, since the minority carrier diffusion lengths are very short in these materials.

Paulauskas, Irene E. [University of Tennessee, Knoxville (UTK); Jellison Jr, Gerald Earle [ORNL; Boatner, Lynn A [ORNL; Brown, G. M. [Oak Ridge National Laboratory (ORNL)

2011-01-01

6

Formation of a ZnO2 layer on the surface of single crystal ZnO substrates with oxygen atoms by hydrogen peroxide treatment  

NASA Astrophysics Data System (ADS)

Formation of a ZnO2 layer by H2O2 treatment for single crystal ZnO (0001) substrates was studied. X-ray diffraction (XRD) peaks of ZnO2 with a pyrite structure were observed in XRD 2?-? scan patterns of the O-face of single crystal ZnO (0001) substrates with H2O2 treatment, but these peaks were not observed in patterns of the Zn-face of ZnO (0001) substrates with H2O2 treatment. XRD ? scan patterns of the ZnO (0002) plane of the O-face of single crystal ZnO (0001) substrates were broadened at the tail of the pattern by H2O2 treatment, but such broadening was not observed in that plane of the Zn-face. Grain structure of ZnO2 layers was clearly observed in atomic force microscopy (AFM) images for the O-face of ZnO (0001) substrates with H2O2 treatment. Spectra of X-ray photoelectron spectroscopy (XPS) of the O-face of ZnO (0001) substrates with H2O2 treatment showed a definite peak shift of the O 1s peak. It is thought that a pyrite structure of ZnO2 is easily formed around an O atom of the O-face of ZnO (0001) substrates. Results of XRD measurements, the AFM image, and XPS measurement of the H2O2-treated single crystal ZnO (1010) substrate that has oxygen atoms on the surface appeared to be the same as those of the O-face of ZnO (0001) substrates.

Kashiwaba, Y.; Abe, T.; Nakagawa, A.; Niikura, I.; Kashiwaba, Y.; Daibo, M.; Fujiwara, T.; Osada, H.

2013-03-01

7

X-ray Characterisation of Zinc Oxide (ZnO) Single Crystal Substrates  

SciTech Connect

Single crystal substrates of low defect density are paramount for fully realizing the numerous applications of zinc oxide (ZnO) wide bandgap semiconductors. While ZnO substrates are commercially available from various vendors, very little information is available on the structural properties of these substrates. Therefore, an extensive evaluation of available substrates would serve as a basis for the development of ZnO based devices and technologies. In this study, bulk ZnO single crystal substrates grown by different growth techniques have been characterised using synchrotron white beam X-ray topography and high resolution X-ray diffraction. The substrates exhibit a wide range of dislocation densities from as high as 10{sup 6} cm{sup -2} down to less than 1000 cm{sup -2} depending on the growth technique employed. The authors evaluation reveals that ZnO crystals grown by the hydrothermal technique possess the best structural quality with dislocation densities of 800-1000 cm{sup -2} and rocking curves with a full width half maximum of less than 12 arc seconds.

Dhanaraj, G.; Raghothamachar, B; Dudley, M

2010-01-01

8

Optical nonlinearities of excitons in ZnO single crystal  

Microsoft Academic Search

Time-integrated and spectrally-resolved four-wave mixing (FWM) has been used to study dephasing dynamics of excitons in a free-standing bulk ZnO. Clear FWM signals due to A>Gamma5- and BGamma5-excitions have been observed. We discuss the dephasing dynamics based on the polariton dispersion and four-particle Coulomb correlations.

Kouji Hazu; Takayuki Sota; Katsuo Suzuki; Satoru Adachi; Shigefusa F. Chichibu

2003-01-01

9

Photoluminescence and positron annihilation spectroscopic investigation on a H(+) irradiated ZnO single crystal.  

PubMed

Low temperature photoluminescence and room temperature positron annihilation spectroscopy have been employed to investigate the defects incorporated by 6MeV H(+) ions in a hydrothermally grown ZnO single crystal. Prior to irradiation, the emission from donor bound excitons is at 3.378eV (10K). The irradiation creates an intense and narrow emission at 3.368eV (10K). The intensity of this peak is nearly four times that of the dominant near band edge peak of the pristine crystal. The characteristic features of the 3.368eV emission indicate its origin as a 'hydrogen at oxygen vacancy' type defect. The positron annihilation lifetime measurement reveals a single component lifetime spectrum for both the unirradiated (1641ps) and irradiated crystal (1751ps). It reflects the fact that the positron lifetime and intensity of the new irradiation driven defect species are a little higher compared to those in the unirradiated crystal. However, the estimated defect concentration, even considering the high dynamic defect annihilation rate in ZnO, comes out to be ?4נ10(17)cm(-3) (using SRIM software). This is a very high defect concentration compared to the defect sensitivity of positron annihilation spectroscopy. A probable reason is the partial filling of the incorporated vacancies (positron traps), which in ZnO are zinc vacancies. The positron lifetime of ?175ps (in irradiated ZnO) is consistent with recent theoretical calculations for partially hydrogen-filled zinc vacancies in ZnO. Passivation of oxygen vacancies by hydrogen is also reflected in the photoluminescence results. A possible reason for such vacancy filling (at both Zn and O sites) due to irradiation has also been discussed. PMID:22790024

Sarkar, A; Chakrabarti, Mahuya; Sanyal, D; Bhowmick, D; Dechoudhury, S; Chakrabarti, A; Rakshit, Tamita; Ray, S K

2012-07-12

10

The chemical vapour transport growth of ZnO single crystals  

Microsoft Academic Search

Recently, ZnO attracts a wide interest as a promising material for the application in optoelectronic devices working in the blue and ultraviolet region and (when doped with magnetic impurities) in spintronic devices. Unfortunately, the technology of good, large (e.g.: 2.55cm in diameter) single crystals is very difficult, even as compared with other IIVI compounds. We report on the successful growth

A. Mycielski; L. Kowalczyk; A. Szadkowski; B. Chwalisz; A. Wysmo?ek; J. M. Baranowski; M. Potemski; A. Witowski; R. Jakie?a; A. Barcz; B. Witkowska; W. Kaliszek; A. Suchocki; E. ?usakowska; E. Kami?ska

2004-01-01

11

Mesoporous single-crystal ZnO nanobelts: supported preparation and patterning.  

PubMed

We demonstrate that highly porous ZnO nanobelts can be prepared by thermally decomposing ZnS(en)(0.5) hybrid nanobelts (NBs) synthesized through a solvothermal route using Zn layers deposited on alumina substrates as both the Zn substrate and source. Hybrid decomposition by thermal annealing at 400 C gives porous ZnS NBs that are transformed by further annealing at 600 C into wurtzite single crystal ZnO nanobelts with an axial direction of [0001]. The evolution of the morphological and structural transformation ZnS(en)(0.5)? ZnS ? ZnO is investigated at the nanoscale by transmission and scanning electron microscopy analyses. Control of the ZnO NB distributions by patterning the Zn metallization on alumina is achieved as a consequence of the parent hybrid NB patterned growth. The presence of NBs on alumina in a ?100 ?m wide region between Zn stripes allows us to fabricate two contact devices where contact pads are electrically connected through a porous ZnO NB entanglement. Such devices are suitable for employment in photodetectors as well as in gas and humidity sensors. PMID:23254279

Nasi, Lucia; Calestani, Davide; Fabbri, Filippo; Ferro, Patrizia; Besagni, Tullo; Fedeli, Paolo; Licci, Francesca; Mosca, Roberto

2012-12-20

12

Structural and optical properties of annealed ZnO single crystals in a helium ambient  

NASA Astrophysics Data System (ADS)

We have used X-ray diffraction and photoluminescence measurements to investigate the effects of helium annealing of ZnO single crystals grown by using the hydrothermal method. The crystal structure of the grown ZnO single crystal was hexagonal with cell parameters a = 0.3249 and c = 0.5206 nm. The crystal structure did not change after helium annealing. The full width at half-maximum (FWHM) of the (002) diffraction peak following the helium annealing treatment decreases to 0.048 from 0.093 for the as-grown sample, indicating improved crystalline quality. The PL spectra of the crystals showed near-band-edge and visible (green and yellow) emission bands. The PL intensity of the near-band edge emissions of helium-annealed sample was increased while that of the yellow emission band was decreased. From the temperature dependence of the PL spectra, the peak positions of the free exciton (FE) and the donor-bound exciton (BE) shifted to lower energy whereas the visible emission bands show an anomalous temperature-dependent behavior.

Hwang, Younghun; Um, Youngho; Park, Hyun-Min

2012-11-01

13

Origins of low resistivity in Al ion-implanted ZnO bulk single crystals  

NASA Astrophysics Data System (ADS)

The origins of low resistivity in Al ion-implanted ZnO bulk single crystals are studied by combining Rutherford backscattering spectroscopy (RBS), nuclear reaction analysis (NRA), photoluminescence (PL), and Van der Pauw methods. The Al-ion implantation (peak concentration: 2.6 1020cm-3) into ZnO is performed using a multiple-step energy. The resistivity decreases from ~104 ? cm for un-implanted ZnO to 1.4 10-1 ? cm for as-implanted, and reaches 6.0 10-4 ? cm for samples annealed at 1000 C. RBS and NRA measurements for as-implanted ZnO suggest the existence of the lattice displacement of Zn (Zni) and O (Oi), respectively. After annealing at 1000 C, the Zni related defects remain and the Oi related defects disappear. The origin of the low resistivity in the as-implanted sample is attributed to the Zni (~30 meV [Look et al., Phys. Rev. Lett. 82, 2552 (1999)]). In contrast, the origin of the low resistivity in the sample annealed at 1000 C is assigned to both of the Zni related defects and the electrically activated Al donor. A new PL emission appears at around 3.32 eV after annealing at 1000 C, suggesting electrically activated Al donors.

Oga, T.; Izawa, Y.; Kuriyama, K.; Kushida, K.; Kinomura, A.

2011-06-01

14

Intrinsic magnetism of a series of Co substituted ZnO single crystals  

NASA Astrophysics Data System (ADS)

Magnetic properties of a series of well-substituted Zn1-xCoxO (x = 0.018,0.036 and 0.05) single crystals were studied. A typical paramagnetic anisotropy property, which strengthens when x decreases, was found. A magnetization step was observed at 2 K when the magnetic field is parallel to the c axis, indicating that paramagnetic anisotropy is the origin of the strong crystal field effect on Co2+ ions in ZnO lattices. The Co2+ single-ion anisotropy parameter 2D is obtained as 7.5 K. The effective moment of Co2+ takes the values 2.7 B, 1.82 B, 1.49 B when x = 0.018, 0.036 and 0.05, revealing that more antiferromagnetic coupling between Co2+ ions arises in the perfect crystal when x increases.

Lv, Peiwen; Huang, Feng; Chu, Wangsheng; Lin, Zhang; Chen, Dagui; Li, Wei; Chen, Dongliang; Wu, Ziyu

2008-01-01

15

Identification of Zn-vacancy-hydrogen complexes in ZnO single crystals: A challenge to positron annihilation spectroscopy  

Microsoft Academic Search

A systematic study of various, nominally undoped ZnO single crystals, either hydrothermally grown (HTG) or melt grown (MG), has been performed. The crystal quality has been assessed by x-ray diffraction, and a comprehensive estimation of the detailed impurity and hydrogen contents by inductively coupled plasma mass spectrometry and nuclear reaction analysis, respectively, has been made also. High precision positron lifetime

G. Brauer; W. Anwand; D. Grambole; J. Grenzer; W. Skorupa; J. Czek; J. Kuriplach; I. Prochzka; C. C. Ling; C. K. So; D. Schulz; D. Klimm

2009-01-01

16

Gallium doping dependence of single-crystal n-type Zno grown by metal organic chemical vapor deposition  

Microsoft Academic Search

High-quality single-crystal Ga-doped ZnO films have been epitaxially deposited on (0002) sapphire substrate by low-pressure metal organic chemical vapor deposition (MOCVD) technique. The dependence of structural, electrical and optical properties of films on Ga doping concentration was investigated. As grown at the Ga\\/Zn gas ratio of 3.2at%, the film shows a narrow linewidth of 0.26 for ZnO (0002) peak, high

J. D. Ye; S. L. Gu; S. M. Zhu; S. M. Liu; Y. D. Zheng; R. Zhang; Y. Shi; H. Q. Yu; Y. D. Ye

2005-01-01

17

Structure and stability of N-H complexes in single-crystal ZnO  

NASA Astrophysics Data System (ADS)

Zinc oxide (ZnO) is semiconductor with a wide band gap of 3.4 eV. It continues to gain more attention not only for its versatile use in industry but also its potential for further application in electronics, optics, spintronics, and transparent circuits. Many of these applications require p-type ZnO. Nitrogen substituting for oxygen is a possible acceptor for such applications. In this paper, we report a study of nitrogen-hydrogen (N-H) complexes grown into single-crystal ZnO, using seeded chemical vapor transport in an ammonia ambient. An infrared (IR) absorption peak arising from N-H complexes was observed at 3150.6 cm-1 at liquid-helium temperatures. The assignment of this peak was confirmed by nitrogen and hydrogen isotope substitution. Polarized IR spectroscopy shows that the N-H dipole is oriented at an angle ~114 to the c axis, in agreement with previous first-principles calculations. To probe the stability of the N-H complexes, samples were annealed in air, oxygen, and argon. Samples annealed in oxygen at 725 C showed a significant increase in resistivity, due to outdiffusion of hydrogen and compensation by nitrogen acceptors.

Jokela, S. J.; McCluskey, M. D.

2010-06-01

18

Application of ZnO single-crystal wire grown by the thermal evaporation method as a chemical gas sensor for hydrogen sulfide.  

PubMed

A zinc oxide single-crystal wire was synthesized for application as a gas-sensing material for hydrogen sulfide, and its gas-sensing properties were investigated in this study. The gas sensor consisted of a ZnO thin film as the buffer layer and a ZnO single-crystal wire. The ZnO thin film was deposited over a patterning silicon substrate with a gold electrode by the CFR method. The ZnO single-crystal wire was synthesized over the ZnO thin film using zinc and activated carbon as the precursor for the thermal evaporation method at 800 degrees C. The electrical properties of the gas sensors that were prepared for the growth of ZnO single-crystal wire varied with the amount of zinc contained in the precursor. The charged current on the gas sensors increased with the increasing amount of zinc in the precursor. It was concluded that the charged current on the gas sensors was related to ZnO single-crystal wire growth on the silicon substrate area between the two electrodes. The charged current on the gas sensor was enhanced when the ZnO single-crystal wire was exposed to a H2S stream. The experimental results obtained in this study confirmed that a ZnO single-crystal wire can be used as a gas sensor for H2S. PMID:21446509

Park, N K; Lee, S Y; Lee, T J

2011-01-01

19

Defects in 6 MeV H+ irradiated hydrothermal ZnO single crystal  

NASA Astrophysics Data System (ADS)

The effect of 6 MeV H+ irradiation on hydrothermally grown ZnO single crystal has been investigated using high resolution x-ray diffraction (HRXRD) and optical absorption (ultraviolet-visible) spectroscopy. The increase of the diffuse scattering in the reciprocal space maps measured using HRXRD indicates an increase of the point defect density upon irradiation. Within the penetration depth of x-rays of several micrometres, the defect density increased with increasing distance from the sample surface. On the other hand, the near band gap optical absorption became sharper for the irradiated crystal. This reflects enhanced band to band absorption and reduced sub-band gap absorption due to defects. Temperature dependent photoluminescence spectra of the pristine sample show negative thermal quenching (NTQ) of the luminescence which is due to the presence of two or more donor related defects. Upon irradiation, a single dominant donor bound transition can be found without any temperature induced NTQ. Enhancement of the band edge luminescence and reduction of the defect related luminescence is observed at 10 K. Such changes have been discussed in the light of the hydrogen present in the as-grown state of hydrothermal ZnO.

Sarkar, A.; Chakrabarti, Mahuya; Bhowmick, D.; Chakrabarti, A.; Ray, S. K.; Rafaja, D.; Sanyal, D.

2013-09-01

20

Origins of low resistivity in Al ion-implanted ZnO bulk single crystals  

SciTech Connect

The origins of low resistivity in Al ion-implanted ZnO bulk single crystals are studied by combining Rutherford backscattering spectroscopy (RBS), nuclear reaction analysis (NRA), photoluminescence (PL), and Van der Pauw methods. The Al-ion implantation (peak concentration: 2.6 x 10{sup 20}cm{sup -3}) into ZnO is performed using a multiple-step energy. The resistivity decreases from {approx}10{sup 4{Omega}} cm for un-implanted ZnO to 1.4 x 10{sup -1{Omega}} cm for as-implanted, and reaches 6.0 x 10{sup -4{Omega}} cm for samples annealed at 1000 deg. C. RBS and NRA measurements for as-implanted ZnO suggest the existence of the lattice displacement of Zn (Zn{sub i}) and O (O{sub i}), respectively. After annealing at 1000 deg. C, the Zn{sub i} related defects remain and the O{sub i} related defects disappear. The origin of the low resistivity in the as-implanted sample is attributed to the Zn{sub i} ({approx}30 meV [Look et al., Phys. Rev. Lett. 82, 2552 (1999)]). In contrast, the origin of the low resistivity in the sample annealed at 1000 deg. C is assigned to both of the Zn{sub i} related defects and the electrically activated Al donor. A new PL emission appears at around 3.32 eV after annealing at 1000 deg. C, suggesting electrically activated Al donors.

Oga, T.; Izawa, Y.; Kuriyama, K. [College of Engineering and Research Center of Ion Beam Technology, Hosei University, Koganei, Tokyo 184-8584 (Japan); Kushida, K. [Departments of Arts and Sciences, Osaka Kyoiku University, Kashiwara, Osaka 582-8582 (Japan); Kinomura, A. [National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568 (Japan)

2011-06-15

21

Identification of Zn-vacancy-hydrogen complexes in ZnO single crystals: A challenge to positron annihilation spectroscopy  

NASA Astrophysics Data System (ADS)

A systematic study of various, nominally undoped ZnO single crystals, either hydrothermally grown (HTG) or melt grown (MG), has been performed. The crystal quality has been assessed by x-ray diffraction, and a comprehensive estimation of the detailed impurity and hydrogen contents by inductively coupled plasma mass spectrometry and nuclear reaction analysis, respectively, has been made also. High precision positron lifetime experiments show that a single positron lifetime is observed in all crystals investigated, which clusters at 180-182 ps and 165-167 ps for HTG and MG crystals, respectively. Furthermore, hydrogen is detected in all crystals in a bound state with a high concentration (at least 0.3at.% ), whereas the concentrations of other impurities are very small. From ab initio calculations it is suggested that the existence of Zn-vacancy-hydrogen complexes is the most natural explanation for the given experimental facts at present. Furthermore, the distribution of H at a metal/ZnO interface of a MG crystal, and the H content of a HTG crystal upon annealing and time afterward has been monitored, as this is most probably related to the properties of electrical contacts made at ZnO and the instability in p -type conductivity observed at ZnO nanorods in literature. All experimental findings and presented theoretical considerations support the conclusion that various types of Zn-vacancy-hydrogen complexes exist in ZnO and need to be taken into account in future studies, especially for HTG materials.

Brauer, G.; Anwand, W.; Grambole, D.; Grenzer, J.; Skorupa, W.; ?ek, J.; Kuriplach, J.; Prochzka, I.; Ling, C. C.; So, C. K.; Schulz, D.; Klimm, D.

2009-03-01

22

Relaxor- and phase-transition-like behaviors in ZnO single crystals at high temperatures  

NASA Astrophysics Data System (ADS)

We herein reported the dielectric properties of ZnO single crystals, and three dielectric anomalies were found. The first anomaly shows a relaxor-like behavior. It is composed of two oxygen-vacancy-related relaxation processes: a dipolar relaxation related to the hopping motions of single-ionized oxygen vacancies and a Maxwell-Wagner relaxation as the defects were blocked by the interfaces of sample/electrode contacts. The second anomaly behaves as a phase-transition-like behavior. It is ascribed to the distribution state transition for oxygen vacancies from static disorder to dynamic disorder. The third anomaly exhibits a relaxor-like behavior. It is an artificial effect caused by negative capacitance.

Liu, L. N.; Wang, C. C.; Lei, C. M.; Li, T.; Wang, G. J.; Sun, X. H.; Wang, J.; Huang, S. G.; Li, Y. D.; Wang, H.

2013-03-01

23

The effect of flash lamp annealing on Fe implanted ZnO single crystals  

SciTech Connect

The effect of flash lamp annealing applied to ZnO single crystals implanted with 3.6 at. % Fe has been studied. For intermediate light power, the implantation-induced surface defects could be annealed without creation of secondary phases within the implanted region. At the same annealing temperatures, however, ion-beam-induced open volume defects start to increase in size. Recrystallization is initiated for the highest light power applied, i.e., the ion-beam-induced lattice disorder reflected by the minimum channeling yield of Rutherford backscattering spectroscopy decreases from 76% to 46% and the open volume defects are annealed. At the same time, the Fe{sup 3+} fraction increases at the cost of the Fe{sup 2+} states. Weak ferromagnetic properties that are mainly associated with nanoparticles are induced.

Potzger, K.; Anwand, W.; Reuther, H.; Zhou, Shengqiang; Talut, G.; Brauer, G.; Skorupa, W.; Fassbender, J. [Institute of Ion Beam Physics and Materials Research, Forschungszentrum Rossendorf, P.O. Box 510119, 01314 Dresden (Germany)

2007-02-01

24

Photonic crystal heterostructures fabricated by TiO2 and ZnO inverse opals using colloidal crystal template with single kind of microspheres  

NASA Astrophysics Data System (ADS)

The fabrication of photonic crystal heterostructures is important for the applications in the fields of integrated photonic crystal chips, multi-frequency optical Bragg filters or mirrors. However, multiple steps of self-assembly process of microspheres are always employed in the fabrication of photonic crystal heterostructures, which may produce lattice mismatches of colloidal crystals. Therefore, photonic crystal heterostructures fabricated by using colloidal crystal template with single kind of microspheres were investigated in this paper. A colloidal crystal template with uniform periodicity was firstly formed by monodispersed polystyrene microsphere. Then ZnO was electrodeposited into the interstices of the template. The thickness of ZnO was controlled to be less than the thickness of the template by varying the deposition time. After the TiO2 precursor was filled into the top voids in the template, the polystyrene colloidal crystal template was removed and photonic crystal heterostructures fabricated by ZnO and TiO2 were formed. Both the dielectric constant and the periodicity of the two parts of the heterostructures are different due to the shrinkage of the sol-gel process. The ZnO/TiO2 heterostructures have a broad photonic stop band which is the superposition of photonic stop bands of ZnO inverse opals and TiO2 inverse opals.

Zhang, Yongna; Fu, Ming; Wang, Jigang; He, Dawei; Wang, Yongsheng

2012-09-01

25

Double-sided ZnO nanorod arrays on single-crystal Ag holed microdisks with enhanced photocataltytic efficiency.  

PubMed

Novel hierarchical heterostructures of double-sided ZnO nanorod (NR) arrays grown on single-crystal Ag holed microdisks (HMDs) have been prepared through a two-step aqueous strategy including ZnO seed loading and the subsequent heteroepitaxial growth of ZnO NRs on Ag HMDs. By simply adjusting the synthetic parameters, ZnO NRs with variable NR diameters (20-200 nm), lengths (100-1.8 ?m) and unusual shapes (concave, tubular and sharp tips) on Ag HMDs have been realized, which endows the Ag/ZnO heterostructures with versatile morphologies. The novel Ag/ZnO heterostructures consisting of integrated 1D semiconductor/2D metal nanostructured blocks with high specific surface area (SSA) and opened spatial architectures may promise important applications related to photoelectric fields. As expected, in photocatalytic measurements, the typical Ag HMD/ZnO NR heterostructure exhibits superior catalytic activity over other catalysts of bare ZnO NRs, ZnO NR arrays or heterostructured Ag nanowires (NWs)/ZnO NRs. The synergistic effect of the unique Ag HMD/ZnO NR heterostructures contributing to the high catalytic performance has been discussed in detail. PMID:23575896

Zuo, Yuanhui; Qin, Yao; Jin, Chao; Li, Ying; Shi, Donglu; Wu, Qingsheng; Yang, Jinhu

2013-05-21

26

Deep level transient spectroscopic study of oxygen implanted melt grown ZnO single crystal  

NASA Astrophysics Data System (ADS)

Deep level traps in melt grown ZnO single crystal created by oxygen implantation and subsequent annealing in air were studied by deep level transient spectroscopy measurement between 80 and 300 K. The EC-0.29 eV trap (E3) was the dominant peak in the as-grown sample and no new defects were created in the as-O-implanted sample. The single peak feature of the deep level transient spectroscopy (DLTS) spectra did not change with the annealing temperature up to 750 C, but the activation energy decreased to 0.22 eV. This was explained in terms of a thermally induced defect having a peak close to but inseparable from the original 0.29 eV peak. A systematic study on a wide range of the rate window for the DLTS measurement successfully separated the Arrhenius plot data originated from different traps. It was inferred that the E3 concentration in the samples did not change after the O-implantation. The traps at EC-0.11, EC-0.16 and EC-0.58 eV were created after annealing. The EC-0.16 eV trap was assigned to an intrinsic defect. No DLTS signal was found after the sample was annealed to 1200 C.

Ye, Z. R.; Lu, X. H.; Ding, G. W.; Fung, S.; Ling, C. C.; Brauer, G.; Anwand, W.

2011-09-01

27

Deep level transient spectroscopic study of oxygen-implanted ZnO single crystal  

NASA Astrophysics Data System (ADS)

ZnO single crystal samples were implanted by oxygen with the energy of 150keV. After the pretreatment of hydrogen peroxide [1], Schottky contacts were fabricated with Au film deposited by thermal evaporation. Deep level defects were studied by deep level transient spectroscopy (DLTS). The activation energy of the 0.29eV deep trap was observed in the as-implanted sample and samples anneal at 350 ^oC , 650 ^oC and 750 ^oC. Three peaks were identified in the DLTS spectra of the 900 ^oC sample, with the activation energies of 0.11eV, 0.25eV and 0.37eV respectively. The thermal evolutions of the deep levels up to the temperature of 1200 ^oC were also investigated. [4pt] [1] Q. L. Gu, C. C. Ling, X. D. Chen, C. K. Cheng, A. M. C. Ng, C. D. Beling, S. Fung, A. B. Djurisi'c, L. W. Lu, G. Brauer and H. C. Ong, Appl. Phys. Lett. 90, 122101, (2007).

Ye, Ziran; Ding, Guangwei; Fan, Jincheng; Chung Ling, Chi

2011-03-01

28

Giant coercivity in ferromagnetic Co doped ZnO single crystal thin film  

NASA Astrophysics Data System (ADS)

The origin of ferromagnetism in ZnO doped with transition metal impurities has been discussed extensively and appeared to be a highly controversial and challenging topic in today's solid state physics. Magnetism observed in this system is generally weak and soft. We have grown Co:ZnO up to 30 at% Co in single crystal thin film form on c-plane sapphire. A composition dependent coercivity is observed in this system which reaches peak value at 25 at% Co, the values are 860 Oe and 1149 Oe with applied field along parallel and perpendicular to the film substrate interface respectively. This giant coercivity might pave the way to exploit this material as a magnetic semiconductor with novel logic functionalities. The findings are explained based on defect band itinerant ferromagnetism and its partial interaction with localized d electrons of Co through charge transfer. Besides large coercivity, an increase in the band gap with Co concentration has also been observed along with blue emission peak with long tail confirming the formation of extended point defect levels in the host lattice band gap.

Loukya, B.; Negi, D. S.; Dileep, K.; Kumar, N.; Ghatak, Jay; Datta, R.

2013-11-01

29

Influence of the aggregation of a carbazole thiophene cyanoacrylate sensitizer on sensitized photocurrents on ZnO single crystals.  

PubMed

Dye sensitization of zinc oxide single crystals by a carbazole thiophene cyanoacrylate (MK-2) sensitizer deposited from THF and mixtures of THF and water was investigated. AFM images show the formation of larger aggregates, with the maximum size of 20-30 nm from mixtures of THF and water, compared with 8-12 nm from pure THF. Sensitized photocurrent spectra were correlated with the morphological results from AFM imaging and indicate that aggregation in water results in less efficient sensitization of the ZnO substrate. The presence of the aggregation in solution due to water content was confirmed by absorbance and fluorescence spectroscopies. PMID:23808529

Nepomnyashchii, Alexander B; Parkinson, B A

2013-07-17

30

Photoluminescence properties of Nd: LiNbO 3 co-doped with ZnO fiber single crystals grown by micro-pulling-down method  

Microsoft Academic Search

The present interest in small compact diode pumped lasers for the blue-green spectral domain has supported research on new solid state laser systems based on non-linear crystals. Nd:LiNbO3 co-doped with ZnO single crystal fibers were grown by micro-pulling-down method which is an advanced method of fiber crystal growth. The grown crystals were free of cracks and homogeneous distributions of the

J. W Shur; T. I Shin; S. M Lee; S. W Baek; D. H Yoon

2003-01-01

31

Defects in virgin and N+ -implanted ZnO single crystals studied by positron annihilation, Hall effect, and deep-level transient spectroscopy  

Microsoft Academic Search

High-quality single crystals of ZnO in the as-grown and N+ ion-implanted states have been investigated using a combination of three experimental techniques---namely, positron lifetime\\/slow positron implantation spectroscopy accompanied by theoretical calculations of the positron lifetime for selected defects, temperature-dependent Hall (TDH) measurements, and deep level transient spectroscopy (DLTS). The positron lifetime in bulk ZnO is measured to be (1512)ps and

G. Brauer; W. Anwand; W. Skorupa; J. Kuriplach; O. Melikhova; C. Moisson; H. von Wenckstern; H. Schmidt; M. Lorenz; M. Grundmann

2006-01-01

32

Study of the local environment diversity between Co and Mn-doped ZnO single crystal film by multilayer growth technique  

Microsoft Academic Search

We investigated the room temperature ferromagnetism and their local coordination environment of Co and Mn doped in ZnO single crystal films. Both films show room temperature ferromagnetism and the saturated magnetization of the Mn-doped ZnO film is stronger than that of the Co-doped films. From the analysis on the local structures of Zn, Co, and Mn, we verify that the

J. C. A. Huang; H. S. Hsu; J. H. Sun; S. L. Chiu; C. H. Lee; Y. F. Liao; H. Chou

2008-01-01

33

Hydrogen released from bulk ZnO single crystals investigated by time-of-flight electron-stimulated desorption  

SciTech Connect

Electron beam (e-beam) irradiation effects on ZnO single crystals have been investigated by using time-of-flight electron-stimulated desorption (TOF-ESD). The samples were irradiated by using a continuous 0.5 or 1.5 keV e-beam, while the TOF-ESD spectra were taken by using a pulsed 0.5 keV e-beam. For both the O-terminated and Zn-terminated surfaces, the major desorption is H{sup +} desorption. The main trend of H{sup +} desorption intensity and evolution as a function of irradiation time is similar for both faces. The H{sup +} peak is much higher after 1.5 keV irradiation than after 0.5 keV irradiation. The intensity of the H{sup +} peak decreases exponentially as a function of irradiation time and partially recovers after the irradiation is stopped. These observations suggest that the main contribution of the H{sup +} desorption is hydrogen released from the dissociation of H-related defects and complexes in the bulk region of the ZnO by e-beam irradiation. This finding can be used to explain the reported ultraviolet degradation of ZnO single crystals under electron irradiation observed by cathodoluminescence. The surfaces play a lesser role for the H{sup +} desorption, as there are differences of the decreasing rate between the two faces and additionally the intensity of the H{sup +} peak for both the unclean O-face and Zn-facesis smaller than that for clean faces. While the H{sup +} desorption is mainly dominated by the bulk region, O{sup +} desorption is more influenced by the surfaces. There are two kinds of O{sup +} desorbed from ZnO having 13.0 {mu}s TOF and 14.2 {mu}s TOF. The O{sup +} desorption depends on the surface polarity, the surface conditions and the energy used for irradiation.

Dierre, Benjamin; Sekiguchi, Takashi [Advanced Electronic Materials Center, National Institute for Materials Science (NIMS), Tsukuba 305-0044 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-0003 (Japan); Yuan, Xiaoli [Advanced Electronic Materials Center, National Institute for Materials Science (NIMS), Tsukuba 305-0044 (Japan); Ueda, Kazuyuki [Nano High-Tech Research Center, Graduate School of Engineering, Toyota Technological Institute, Nagoya 468-8511 (Japan)

2010-11-15

34

Persistent photoconductivity and photo-responsible defect in 30 MeV-electron irradiated single crystal ZnO  

NASA Astrophysics Data System (ADS)

Persistent photoconductivity (PPC) in 30-MeV electron irradiated ZnO single crystals is studied by excitation using light emitting diodes (LEDs) with various wavelengths. The decay transient of the photoconductivity shows relaxation times in the range of a few ten days for the illumination at 90 K and a few hours at room temperature. An electron paramagnetic resonance (EPR) signal with g-value = 2.005 appears after illumination of blue LED, suggesting the transfer from the artificially introduced oxygen vacancy of 2+ charge state to the metastable + charge state. Once generated, the metastable state does not immediately decay into the 2+ charge state because of energetic barriers of ~190 meV, supporting the mechanism of PPC proposed by Van de Walle.

Kuriyama, K.; Matsumoto, K.; Kushida, K.; Xu, Q.

2010-01-01

35

REVIEW ARTICLE: Single crystal ZnO nanowires as optical and conductometric chemical sensor  

NASA Astrophysics Data System (ADS)

ZnO nanowires were deposited using the vapour phase technique. The nanowires cover the substrate and appear uniform in morphology with lengths of up to several micrometres and uniform lateral size of the order of tenths of a nanometre. The electrical and optical properties of ZnO nanowires have been characterized in the presence of nitrogen oxide. Electrical measurements highlight a remarkable response even at low operating temperatures, with detection limits lower than 200 ppb and an optimal operating temperature of 100C, while the ZnO nanowire photoluminescence is reversibly quenched by the introduction of a few ppm of NO2 even at room temperature.

Comini, E.; Baratto, C.; Faglia, G.; Ferroni, M.; Sberveglieri, G.

2007-12-01

36

ZnO dense nanowire array on a film structure in a single crystal domain texture for optical and photoelectrochemical applications.  

PubMed

A single crystal domain texture quality (a unique in-plane and out-of-plane crystalline orientation over a large area) ZnO nanostructure of a dense nanowire array on a thick film has been homogeneously synthesized on a-plane sapphire substrates over large areas through a one-step chemical vapor deposition (CVD) process. The growth mechanism is clarified: a single crystal [02(-)1] oriented ZnAl(2)O(4) buffer layer was formed at the ZnO film and the a-plane sapphire substrate interface via a diffusion reaction process during the CVD process, providing improved epitaxial conditions that enable the synthesis of the high crystalline quality ZnO nanowire array on a film structure. The high optoelectronic quality of the ZnO nanowire array on a film sample is evidenced by the free exitonic emissions in the low-temperature photoluminescence spectroscopy. A carrier density of ~10(17) cm(-3) with an n-type conductivity of the ZnO nanowire array on a film sample is obtained by electrochemical impedance analysis. Finally, the ZnO nanowire array on a film sample is demonstrated to be an ideal template for a further synthesis of a single crystal quality ZnO-ZnGa(2)O(4) core-shell nanowire array on a film structure. The fabricated ZnO-ZnGa(2)O(4) sample revealed an enhanced anticorrosive ability and photoelectrochemical performance when used as a photoanode in a photoelectrochemical water splitting application. PMID:23150203

Zhong, Miao; Sato, Yukio; Kurniawan, Mario; Apostoluk, Aleksandra; Masenelli, Bruno; Maeda, Etsuo; Ikuhara, Yuichi; Delaunay, Jean-Jacques

2012-11-13

37

Deep level transient spectroscopy studies of n-type ZnO single crystals grown by different techniques.  

PubMed

In the present study single-crystalline ZnO samples grown from the vapor phase, the melt, and a high-temperature aqueous solution (hydrothermal growth) are investigated before and after hydrogen plasma treatments, by means of deep level transient spectroscopy (DLTS) and high-resolution Laplace DLTS. Dominant DLTS peaks are found to appear in the range of 120-350 K for all materials. The DLTS spectra depend on the procedure of growth of the ZnO. The thermal stabilities of the defects in an oxygen atmosphere and in an oxygen-lean atmosphere are analyzed. The origin of the DLTS peaks is discussed. PMID:21813951

Scheffler, L; Kolkovsky, Vl; Lavrov, E V; Weber, J

2011-08-03

38

Radiation-induced formation of ZnO nanoparticles on the ZnSe single-crystal surface  

NASA Astrophysics Data System (ADS)

The possible formation of ZnO nanocrystals was studied as a result of radiolysis of a ZnSe crystal surface exposed to zinc vapor and irradiated with gamma rays and in producing ZnSe-ZnO heterostructures. Under 60Co gamma radiation in air, nanocrystals 27 nm in size are formed from nanoscopic ZnO nuclei. Under a mixed flux of gamma rays and thermal-neutron radiation, a twin structure is formed in the host ZnSe lattice and ZnO is removed. The oxide layer is also destroyed under proton irradiation in vacuum. It is found that the growth of ZnO nanocrystallites causes a manyfold increase in the luminescence intensity in the 600-nm band and in microhardness and also a decrease in the resistance and blocking and threshold voltages irrespective of polarity. Thus, gamma irradiation brings about the formation of light-emitting ZnSe-ZnO: Zn semiconductor structures with a p-n junction.

l'Murotova, D. B.; Ibragimova, . M.; Kalanov, M. U.; Tursunov, N. A.

2009-03-01

39

Evaluation of Carbon Interstitial in C-ion Implanted ZnO Bulk Single Crystals by a Nuclear Reaction Analysis Study: An Origin of Low Resistivity  

NASA Astrophysics Data System (ADS)

Nuclear reaction analysis (NRA) of carbon-implanted ZnO bulk single crystals (carbon concentration: 1.51020 cm-3), in conjunction with the channeling technique, using the 12C(d,p)13C and 16O(d,p)17O reactions shows the presence of the interstitial carbon (Ci) and the occupancy of substitute sites of oxygen atoms. These results suggest that the variation in resistivity from the order of 104 ?cm (for un-implanted samples) to that of 10 ?cm (for as-implanted ones) is attributed to the Ci and/or its complex defects, which would act as a shallow donor in ZnO.

Izawa, Y.; Matsumoto, K.; Oga, T.; Kuriyama, K.; Kushida, K.; Kinomura, A.

2011-12-01

40

Persistent Photoconductivity in electron-irradiated ZnO bulk single crystals: Evaluation of the metastable conductive state by the dual light illumination  

NASA Astrophysics Data System (ADS)

Persistent Photoconductivity (PPC) in 30 MeV electron-irradiated n-type ZnO single crystals is studied under the dual light illumination (DLI: the infrared light excitation after the blue illumination). Below 160 K, the remarkable reduction in PPC is observed by the subsequent infrared illumination, suggesting the release of electrons from the perturbed-host state (PHS) as a metastable conductive state to the nonconductive state (VO+ and/or VO0) via the higher unoccupied states inside the conduction band. Above 160 K, the slight increase in photocurrent is observed by the subsequent illumination, suggesting the photoexcitation of electrons not relevant to the PHS. These results depend on the electron concentration in the PHS. We examine Persistent Photoconductivity (PPC) in 30 MeV electron-irradiated ZnO. PPC studies are carried out under the dual light (blue and infrared) illumination. Below 160 K, the remarkable reduction in PPC is observed after infrared illumination. This attributes to the release of electrons from the metastable conductive state.

Oga, T.; Izawa, Y.; Kuriyama, K.; Kushida, K.; Xu, Q.

2011-11-01

41

Surface effect on the size- and orientation-dependent elastic properties of single-crystal ZnO nanostructures  

NASA Astrophysics Data System (ADS)

We studied the elastic properties of ZnO nanofilms (NFs) and nanowires (NWs) terminated by either (1010) or (1120) surfaces, based on the empirical Buckingham-type potential. It is found that the Young's moduli of ZnO NFs increase as the thicknesses decrease and that of (1010)-surface terminated NFs are systematically larger than that of (1120)-surface terminated ones. In these NFs, the surface atomic layers of both types of NFs are stiffened significantly with respect to the bulk ZnO, and the (1010)-surface layer is much stiffer than the (1120)-surface layer. In contrast, all the interior atomic layers are only slightly stiffer than the bulk ZnO, and are independent on the orientations. The ZnO NWs show similar size- and orientation-dependent mechanical behaviors which also originate from the significant stiffening of the surface atomic layers. Through this study, we predict that the mechanical properties of ZnO nanostructures can be manipulated through controlling the size and orientations of these materials.

Hu, Jun; Pan, B. C.

2009-02-01

42

Microsensor on single ZnO microwire  

Microsoft Academic Search

For development of individual ZnO microwire in hydrogen sensors an environmentally benign synthesis process and fabrication route are required. Here we report a synthesis route for ZnO microwires using vapour phase process. Furthermore, our synthesis technique permits microwires to be transferred to other substrates. This offers the possibility of using focused ion beam instrument for handling. We fabricated a single

G. Chai; E. Rusu; L. Chow; G. I. Stratan; H. Heinrich; A. Schulte; O. Lupan; V. Trofim; S. Railean

2009-01-01

43

Epitaxial Growth and Properties of Cobalt-doped ZnO on ?-Al?O? Single-Crystal Substrates  

SciTech Connect

Co-doped ZnO (CoxZn?-xO) is of potential interest for spintronics due to the prediction of room-temperature ferromagnetism. We have grown epitaxial CoxZn?-xO films on Al?O?(012) substrates by metalorganic chemical vapor deposition using a liquid precursor delivery system. High concentrations of Co (x < 0.35) can be uniformly incorporated into the film without phase segregation. Co is found to be in the ? oxidation state, independent of x. This material can be grown n type by the deliberate incorporation of oxygen vacancies, but not by inclusion of ~1 at. % Al. Semiconducting films remain ferromagnetic up to 350 K. In contrast films without oxygen vacancies are insulating and nonmagnetic, suggesting that exchange interaction is mediated by itinerant carriers. The saturation and remanent magnetization on a per Co basis was very small (< 0.1 ?B/Co), even in the best films. The dependence of saturation magnetization, as measured by optical magnetic circular dichroism, on magnetic field and temperature, agrees with the theoretical Brillouin function, demonstrating that the majority of the Co(II) ions behave as magnetically isolated S = 3/2 spins.

Tuan, Allan C.; Bryan, John D.; Pakhomov, Alexandre; Shutthanandan, V.; Thevuthasan, Suntharampillai; McCready, David E.; Gaspar, Dan J.; Engelhard, Mark H.; Rogers, J. W.; Krishnan, Kannan M.; Gamelin, Daniel R.; Chambers, Scott A.

2004-08-30

44

Properties of gallium- and aluminum-doped bulk ZnO obtained from single-crystals grown by liquid phase epitaxy  

Microsoft Academic Search

Bulk properties of gallium (Ga)- and aluminum (Al)-doped zinc oxide (ZnO) were studied using bulky single-crystalline thick films grown by liquid phase epitaxy (LPE). The highest possible dopant concentration was 11019cm3 for LPE growth at around 800C. The electron concentration was nearly same to the Ga and Al concentrations. The donor binding energy decreased to nearly zero with an increase

Jun Kobayashi; Naoki Ohashi; Hideyuki Sekiwa; Isao Sakaguchi; Miyuki Miyamoto; Yoshiki Wada; Yutaka Adachi; Kenji Matsumoto; Hajime Haneda

2009-01-01

45

Positive temperature coefficient of resistance of single ZnO nanorods  

NASA Astrophysics Data System (ADS)

ZnO nanorods were synthesized by a simple aqueous solution method. Crystal structures and morphology studies show that the ZnO nanorods are single crystalline with the growth direction aligned with the c axis of ZnO. An Au-ZnO nanorod-Au (metal-semiconductor-metal, MSM) device using the synthesized nanorod was fabricated. An electronic model with two back-to-back Schottky diodes in series with a nanorod was used to describe the electrical transport of the MSM device. A positive temperature coefficient of resistance is observed on a single ZnO nanorod from 383 to 473 K. A simple model has been proposed to explain such an abnormal behavior including the effect of the interface states and the adsorption-desorption of the water/oxygen molecules on the surface of the nanorod.

He, Guan-nan; Huang, Bo; Shen, Hui

2011-02-01

46

Positive temperature coefficient of resistance of single ZnO nanorods.  

PubMed

ZnO nanorods were synthesized by a simple aqueous solution method. Crystal structures and morphology studies show that the ZnO nanorods are single crystalline with the growth direction aligned with the c axis of ZnO. An Au-ZnO nanorod-Au (metal-semiconductor-metal, MSM) device using the synthesized nanorod was fabricated. An electronic model with two back-to-back Schottky diodes in series with a nanorod was used to describe the electrical transport of the MSM device. A positive temperature coefficient of resistance is observed on a single ZnO nanorod from 383 to 473 K. A simple model has been proposed to explain such an abnormal behavior including the effect of the interface states and the adsorption-desorption of the water/oxygen molecules on the surface of the nanorod. PMID:21212482

He, Guan-nan; Huang, Bo; Shen, Hui

2011-01-07

47

Photocatalytic degradation of methyl orange over single crystalline ZnO: orientation dependence of photoactivity and photostability of ZnO.  

PubMed

The photocatalytic destruction of methyl orange in aqueous solution has been studied over single crystal ZnO surfaces under UV irradiation. Differences in the apparent reaction rates between the polar surfaces (first order) and the nonpolar ZnO(10-10) surface (zero order) were observed. Reaction rates for different crystallographic orientations showed the highest activity for ZnO(10-10) followed by ZnO(0001)-Zn and the lowest activity for ZnO(000-1)-O surfaces. In addition, the etching of surfaces by photolysis has been studied. For this process, strongly face-dependent behavior was also observed. Possible reasons for the face dependencies are discussed. PMID:19437731

Kislov, Nikolai; Lahiri, Jayeeta; Verma, Himanshu; Goswami, D Yogi; Stefanakos, Elias; Batzill, Matthias

2009-03-01

48

Single crystal faceplate evaluation  

NASA Astrophysics Data System (ADS)

The Naval Training Systems Center developed single crystal faceplates which held promise for providing a significantly improved life span over conventional power phosphor cathode ray tubes (CRT) while maintaining acceptable resolution and light output characteristics. Single crystal faceplates being evaluated are composed of yttrium aluminum garnet (YAG) with an epitaxial cerium phosphor layer grown on the YAG substrate producing a cathodoluminescent material (CE:YAG). The single crystal nature of these faceplates should allow higher resolution (no phosphor grains) and higher thermal conductivity.

Tucker, A. R.; Kindl, H. J.

1993-10-01

49

Linear Compressibilities of Ii-Vi Compound Single Crystals.  

National Technical Information Service (NTIS)

The isothermal linear compressibilities of the II-VI compound single crystals, CdS, CdSe, CdTe, ZnO, ZnS, ZnSe, and ZnTe were measured by an optical interferometer. The change in length of the crystals was obtained relative to iron under hydrostatic press...

D. W. Langer R. A. Montalvo

1970-01-01

50

Crystal phase engineered quantum wells in ZnO nanowires  

NASA Astrophysics Data System (ADS)

We report the fabrication of quantum wells in ZnO nanowires (NWs) by a crystal phase engineering approach. Basal plane stacking faults (BSFs) in the wurtzite structure can be considered as a minimal segment of zinc blende. Due to the existing band offsets at the wurtzite (WZ)/zinc blende (ZB) material interface, incorporation of a high density of BSFs into ZnO NWs results in type II band alignment. Thus, the BSF structure acts as a quantum well for electrons and a potential barrier for holes in the valence band. We have studied the photoluminescence properties of ZnO NWs containing high concentrations of BSFs in comparison to high-quality ZnO NWs of pure wurtzite structure. It is revealed that BSFs form quantum wells in WZ ZnO nanowires, providing an additional luminescence peak at 3.329 eV at 4 K. The luminescence mechanism is explained as an indirect exciton transition due to the recombination of electrons in the QW conduction band with holes localized near the BSF. The binding energy of electrons is found to be around 100 meV, while the excitons are localized with the binding energy of holes of ?5 meV, due to the coupling of BSFs, which form QW-like structures.

Khranovskyy, V.; Glushenkov, Alexey M.; Chen, Y.; Khalid, A.; Zhang, H.; Hultman, L.; Monemar, B.; Yakimova, R.

2013-05-01

51

SINGLE CRYSTAL NEUTRON DIFFRACTION.  

SciTech Connect

Single-crystal neutron diffraction measures the elastic Bragg reflection intensities from crystals of a material, the structure of which is the subject of investigation. A single crystal is placed in a beam of neutrons produced at a nuclear reactor or at a proton accelerator-based spallation source. Single-crystal diffraction measurements are commonly made at thermal neutron beam energies, which correspond to neutron wavelengths in the neighborhood of 1 Angstrom. For high-resolution studies requiring shorter wavelengths (ca. 0.3-0.8 Angstroms), a pulsed spallation source or a high-temperature moderator (a ''hot source'') at a reactor may be used. When complex structures with large unit-cell repeats are under investigation, as is the case in structural biology, a cryogenic-temperature moderator (a ''cold source'') may be employed to obtain longer neutron wavelengths (ca. 4-10 Angstroms). A single-crystal neutron diffraction analysis will determine the crystal structure of the material, typically including its unit cell and space group, the positions of the atomic nuclei and their mean-square displacements, and relevant site occupancies. Because the neutron possesses a magnetic moment, the magnetic structure of the material can be determined as well, from the magnetic contribution to the Bragg intensities. This latter aspect falls beyond the scope of the present unit; for information on magnetic scattering of neutrons see Unit 14.3. Instruments for single-crystal diffraction (single-crystal diffractometers or SCDs) are generally available at the major neutron scattering center facilities. Beam time on many of these instruments is available through a proposal mechanism. A listing of neutron SCD instruments and their corresponding facility contacts is included in an appendix accompanying this unit.

KOETZLE,T.F.

2001-03-13

52

Single crystal diamond  

US Patent & Trademark Office Database

A single crystal diamond grown by vapor phase synthesis, wherein when one main surface is irradiated with a linearly polarized light considered to be the synthesis of two mutually perpendicular linearly polarized light beams, the phase difference between the two mutually perpendicular linearly polarized light beams exiting another main surface on the opposite side is, at a maximum, not more than 50 nm per 100 .mu.m of crystal thickness over the entire crystal. This single crystal diamond is of a large size and high quality unattainable up to now, and has characteristics that are extremely desirable in semiconductor device substrates and are applied to optical components of which low strain is required.

2009-11-10

53

Single crystals of chitosan.  

PubMed

Lamellar single crystals of chitosan were prepared at 125 degrees C by adding ammonia to a low DP fraction of chitosan dissolved in water. The crystals gave sharp electron diffraction diagrams which could be indexed in an orthorhombic P2(1)2(1)2(1) unit cell with a = 8.07 A, b = 8.44 A, c = 10.34 A. The unit cell contained two anti-parallel chitosan chains and no water molecules. It was found that cellulose microfibrils from Valonia ventricosa could act as nuclei for inducing the crystallization of chitosan on cellulose. This produced a shish-kebab morphology. PMID:2085494

Cartier, N; Domard, A; Chanzy, H

1990-10-01

54

Humidity sensitive properties of ZnO nanotetrapods investigated by a quartz crystal microbalance  

Microsoft Academic Search

ZnO nanotetrapods were prepared and studied for the humidity detection application. The humidity sensors developed were featured by combination of a quartz crystal as a transducer and ZnO nanotetrapods as a sensing element. The ZnO nanotetrapods were synthesized by evaporating highly pure zinc pellets (99.999%) at 900C in air and then distributed onto the electrode surfaces of the quartz crystal

Xiao-Hua Wang; Yan-Fang Ding; Jian Zhang; Zi-Qiang Zhu; Shu-Zhen You; Shao-Qiang Chen; Jianzhong Zhu

2006-01-01

55

Detection of humidity based on quartz crystal microbalance coated with ZnO nanostructure films  

Microsoft Academic Search

The possibilities and properties of ZnO nanorod and nanowire films-coated quartz crystal microbalance (QCM) as a humidity sensor have been investigated. The morphology and crystal structures of ZnO nanorods and nanowires were characterized with X-ray diffraction (XRD) and scanning electron microscopy (SEM). It can be found that the frequency shift of the ZnO nanostructures-coated QCM linearly decreases with increasing relative

Yongsheng Zhang; Ke Yu; Shixi Ouyang; Laiqiang Luo; Hongmei Hu; Qiuxiang Zhang; Ziqiang Zhu

2005-01-01

56

Selective area growth of ZnO crystals by electric current heating  

Microsoft Academic Search

A novel selective area growth method for ZnO crystals was developed by a combination of catalyst arrangement using nanoindentation and electric current heating. The crystal growth of ZnO nanowhiskers was initiated from the catalyst. The nanowhiskers varied in size from a diameter of 70 to 300 nm and a length of 1 to 20 ?m. Among the nanowhiskers obtained, a

Dai Nezaki; Masaaki Yasuda; Takanari Yasui; Masasuke Takata

2004-01-01

57

Single ZnO nanobelt based field effect transistors (FETs).  

PubMed

Electrical properties of single ZnO nanobelt have been examined by fabricating single nanobelt based field effect transistors (FETs). The ZnO nanobelts were grown via non-catalytic simple thermal evaporation process by using metallic zinc powder in the presence of oxygen. The detailed structural and optical characterizations confirmed that the grown nanobelts are well-crystalline with the wurtzite hexagonal phase and exhibiting good optical properties. The passivation effect on the electrical characteristics of the as-grown nanobelts was also evaluated by passivating the fabricated FETs with polymethyl methacrylate (PMMA). The passivated single ZnO nanobelt based FETs exhibited higher electrical performance as compared to non-passivated FETs due to reduction in the physically absorbed chemisorbed species such as O-, O2-, O2, or OH- etc. The field effect mobility (micro(eff)) of the fabricated nanobelt based non-passivated and passivated FETs was estimated to be approximately 21.3 and 59 cm2/V x s, respectively. Moreover the carrier concentration and peak transconductance of the fabricated non-passivated and passivated FET were calculated to be approximately 8.73 x 10(17) and approximately 1.86 x 10(18) cm(-3) and approximately 0.76 and 1.4 microS, respectively. This work offers substantial opportunities for further practical electronics and photonics nanodevice applications of ZnO based nanostructures. PMID:19908447

Park, Y K; Umar, Ahmad; Lee, E W; Hong, D M; Hahn, Yoon-Bong

2009-10-01

58

Paramagnetism and antiferromagnetic interactions in single-phase Fe-implanted ZnO  

NASA Astrophysics Data System (ADS)

As the intrinsic origin of the high-temperature ferromagnetism often observed in wide-gap dilute magnetic semiconductors becomes increasingly debated, there is a growing need for comprehensive studies on the single-phase region of the phase diagram of these materials. Here we report on the magnetic and structural properties of Fe-doped ZnO prepared by ion implantation of ZnO single crystals. A detailed structural characterization shows that the Fe impurities substitute for Zn in ZnO in a wurtzite Zn1-xFexO phase which is coherent with the ZnO host. In addition, the density of beam-induced defects is progressively decreased by thermal annealing up to 900? C, from highly disordered after implantation to highly crystalline upon subsequent annealing. Based on a detailed analysis of the magnetometry data, we demonstrate that isolated Fe impurities occupying Zn-substitutional sites behave as localized paramagnetic moments down to 2 K, irrespective of the Fe concentration and the density of beam-induced defects. With increasing local concentration of Zn-substitutional Fe, strong nearest-cation-neighbor antiferromagnetic interactions favor the antiparallel alignment of the Fe moments.

Pereira, L. M. C.; Wahl, U.; Correia, J. G.; Van Bael, M. J.; Temst, K.; Vantomme, A.; Arajo, J. P.

2013-10-01

59

Paramagnetism and antiferromagnetic interactions in single-phase Fe-implanted ZnO.  

PubMed

As the intrinsic origin of the high-temperature ferromagnetism often observed in wide-gap dilute magnetic semiconductors becomes increasingly debated, there is a growing need for comprehensive studies on the single-phase region of the phase diagram of these materials. Here we report on the magnetic and structural properties of Fe-doped ZnO prepared by ion implantation of ZnO single crystals. A detailed structural characterization shows that the Fe impurities substitute for Zn in ZnO in a wurtzite Zn1-xFexO phase which is coherent with the ZnO host. In addition, the density of beam-induced defects is progressively decreased by thermal annealing up to 900? C, from highly disordered after implantation to highly crystalline upon subsequent annealing. Based on a detailed analysis of the magnetometry data, we demonstrate that isolated Fe impurities occupying Zn-substitutional sites behave as localized paramagnetic moments down to 2K, irrespective of the Fe concentration and the density of beam-induced defects. With increasing local concentration of Zn-substitutional Fe, strong nearest-cation-neighbor antiferromagnetic interactions favor the antiparallel alignment of the Fe moments. PMID:24025311

Pereira, L M C; Wahl, U; Correia, J G; Van Bael, M J; Temst, K; Vantomme, A; Arajo, J P

2013-09-11

60

Hydrothermal growth and characterization of aluminum-doped ZnO bulk crystals  

NASA Astrophysics Data System (ADS)

Bulk ZnO crystals were grown by the hydrothermal technique with Al2O3 added to the solution in an attempt to obtain Al-doped ZnO crystals. Aluminum and indium co-doped ZnO were also grown by the same technique. Adding Al2O3 to the growth solution has a significant impact on the ZnO growth ? either preventing overgrowth and dissolving the seed growth or degrading the crystalline quality; nevertheless, the resulting crystals of both Al:ZnO and Al/In:ZnO are highly conductive, similar to In and Ga doped ZnO crystals, with a resistivity approaching 0.01 ? cm, as revealed by temperature-dependent Hall-effect measurements. Photoluminescence spectra at 18 K show Al0-bound-exciton peak energies of 3.3604 eV on the Zn face and 3.3609 eV on the O face for the Al-doped ZnO crystals. Similarly both an Al0- bound-exciton peak at 3.3604 eV and an In0-bound-exciton peak at 3.3575 eV were found on the Al/In-co-doped crystals. The electrical properties of all group III doped ZnO crystals grown hydrothermally are compared with each other and with Al:ZnO obtained by other growth methods.

Wang, Buguo; Mann, Matthew; Claflin, Bruce; Snure, Michael; Look, David C.

2013-03-01

61

Ferromagnetism in Mn-implanted ZnO:Sn single crystals  

Microsoft Academic Search

We have investigated the magnetic properties of Mn-implanted n-type ZnO single crystals that are codoped with Sn. Theory predicts that room-temperature carrier-mediated ferromagnetism should be possible in manganese-doped p-type ZnO, although Mn-doped n-type ZnO should not be ferromagnetic. While previous efforts report only low-temperature ferromagnetism in Mn-doped ZnO that is n type via shallow donors, we find evidence for ferromagnetism

D. P. Norton; S. J. Pearton; A. F. Hebard; N. Theodoropoulou; L. A. Boatner; R. G. Wilson

2003-01-01

62

Multimode Resistive Switching in Single ZnO Nanoisland System.  

PubMed

Resistive memory has attracted a great deal of attention as an alternative to contemporary flash memory. Here we demonstrate an interesting phenomenon that multimode resistive switching, i.e. threshold-like, self-rectifying and ordinary bipolar switching, can be observed in one self-assembled single-crystalline ZnO nanoisland with base diameter and height ranging around 30 and 40?nm on Si at different levels of current compliance. Current-voltage characteristics, conductive atomic force microscopy (C-AFM), and piezoresponse force microscopy results show that the threshold-like and self-rectifying types of switching are controlled by the movement of oxygen vacancies in ZnO nanoisland between the C-AFM tip and Si substrate while ordinary bipolar switching is controlled by formation and rupture of conducting nano-filaments. Threshold-like switching leads to a very small switching power density of 1 10(3)?W/cm(2). PMID:23934276

Qi, Jing; Olmedo, Mario; Zheng, Jian-Guo; Liu, Jianlin

2013-08-12

63

Detection of humidity based on quartz crystal microbalance coated with ZnO nanostructure films  

NASA Astrophysics Data System (ADS)

The possibilities and properties of ZnO nanorod and nanowire films-coated quartz crystal microbalance (QCM) as a humidity sensor have been investigated. The morphology and crystal structures of ZnO nanorods and nanowires were characterized with X-ray diffraction (XRD) and scanning electron microscopy (SEM). It can be found that the frequency shift of the ZnO nanostructures-coated QCM linearly decreases with increasing relative humidity over the range of 5 97% RH. The experimental results demonstrated that ZnO nanostructures-coated QCM are usable as a humidity sensor and as an analytical device. It appears that the ZnO nanomaterial films can be used as efficient humidity sensors.

Zhang, Yongsheng; Yu, Ke; Ouyang, Shixi; Luo, Laiqiang; Hu, Hongmei; Zhang, Qiuxiang; Zhu, Ziqiang

2005-11-01

64

Embedment of ZnO nanoparticles in the natural photonic crystals within peacock feathers  

NASA Astrophysics Data System (ADS)

Inspired by the embedment of emission species in synthetic photonic crystals to display novel optical properties, the natural photonic crystals within peacock feathers are chosen as the matrix to embed ZnO nanoparticles through an in situ approach. Peacock feathers function as the supporting substrate and provide reactive sites for the in situ synthesis of hexagonal ZnO nanoparticles. Herein, ZnO nanoparticles exhibit photoluminescence in the visible range and are supposed to be tailored by the peacock feather, having potential applications in optoelectronics and optical communications.

Han, Jie; Su, Huilan; Zhang, Chunfu; Dong, Qun; Zhang, Wang; Zhang, Di

2008-09-01

65

A simple method for systematically controlling ZnO crystal size and growth orientation  

SciTech Connect

We present a simple, easy and reproducible method to systematically control the dimension and shape evolution of zinc oxide (ZnO) as thin film on glass substrate by chemical bath deposition (CBD). The only varying factor to control crystal transformation is the molar ratio of Cd{sup 2+}/Zn{sup 2+}, R{sub m}, in the initial chemical solution. With the increase of R{sub m}, ZnO crystals transformed from long-and-slim hexagonal rods to fat-and-short hexagonal pyramids, and then to twinning hexagonal dots as observed by scanning electron microscopy (SEM). Film crystallinity was characterized by X-ray diffraction (XRD). Chemical component analysis by energy dispersive spectroscopy (EDS) showed that most cadmium was present in the residual solution instead of the developed film and the precipitate at the bottom of beaker. The mechanism of the cadmium effect, with different initial concentrations, on ZnO crystal transformation was tentatively addressed. We believe that cadmium influences the chelate ligands adsorption onto (0001-bar) plane of ZnO crystals, alters the crystal growth orientation, and thus directs the transformation of the size and shape of ZnO crystals.

Zhang Rong [Department of Paper and Chemical Engineering, Miami University, Oxford, OH 45056 (United States); Kerr, Lei L. [Department of Paper and Chemical Engineering, Miami University, Oxford, OH 45056 (United States)], E-mail: kerrll@muohio.edu

2007-03-15

66

Formation of quasi-single crystalline porous ZnO nanostructures with a single large cavity  

NASA Astrophysics Data System (ADS)

We report a method for synthesizing quasi-single crystalline porous ZnO nanostructures containing a single large cavity. The microwave-assisted route consists of a short (about 2 min) temperature ramping stage (from room temperature to 120 C) and a stage in which the temperature is maintained at 120 C for 2 h. The structures produced by this route were 200-480 nm in diameter. The morphological yields of this method were very high. The temperature- and time-dependent evolution of the synthesized powders and the effects of an additive, vitamin C, were studied. Spherical amorphous/polycrystalline structures (70-170 nm in diameter), which appeared transitorily, may play a key role in the formation of the single crystalline porous hollow ZnO nanostructures. Studies and characterization of the nanostructures suggested a possible mechanism for formation of the quasi-single crystalline porous ZnO nanostructures with an interior space.We report a method for synthesizing quasi-single crystalline porous ZnO nanostructures containing a single large cavity. The microwave-assisted route consists of a short (about 2 min) temperature ramping stage (from room temperature to 120 C) and a stage in which the temperature is maintained at 120 C for 2 h. The structures produced by this route were 200-480 nm in diameter. The morphological yields of this method were very high. The temperature- and time-dependent evolution of the synthesized powders and the effects of an additive, vitamin C, were studied. Spherical amorphous/polycrystalline structures (70-170 nm in diameter), which appeared transitorily, may play a key role in the formation of the single crystalline porous hollow ZnO nanostructures. Studies and characterization of the nanostructures suggested a possible mechanism for formation of the quasi-single crystalline porous ZnO nanostructures with an interior space. Electronic supplementary information (ESI) available: TEM images and the corresponding SAED image of a ZnO nanostructure synthesized from the reaction without l(+)-ascorbic acid at the 85 C time point (Fig. S1). See DOI: 10.1039/c1nr10609k

Cho, Seungho; Kim, Semi; Jung, Dae-Won; Lee, Kun-Hong

2011-09-01

67

Localized ultraviolet photoresponse in single bent ZnO micro/nanowires  

SciTech Connect

The localized ultraviolet photoresponse in single bent ZnO micro/nanowires bridging two Ohmic contacts has been investigated. The ZnO micro/nanowire has a higher photoresponse sensitivity of about 190% at the bent region (bending strain: about 4%) than that at the straight region (about 50%). The rise and decay time constants are almost the same in the straight and bent regions of the ZnO micro/nanowire. A possible mechanism has been proposed and discussed. The bent ZnO micro/nanowires could be potentially useful for fabricating the coupled piezoelectric and optoelectronic nanodevices.

Guo Wen; Yang Ya; Qi Junjie; Zhao Jing; Zhang Yue [State Key Laboratory for Advanced Metals and Materials, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China)

2010-09-27

68

Raman measurements on nanocolumnar ZnO crystals  

Microsoft Academic Search

Hexagonal zinc oxide nanocolumns have been grown on conducting F-doped SnO2 substrates by galvanostatic electrodeposition. Raman and photoluminescence spectra of the ZnO nanocolumns have been measured in several samples with different size distributions as a function of the annealing temperature. Photoluminescence properties of ZnO nanocolumns are strongly influenced by the crystalline quality of the samples. The dependence of the crystalline

B. Mar; J. Cembrero; F. J. Manjn; M. Mollar; R. Gmez

2005-01-01

69

Enhanced mass sensitivity of ZnO nanorod-grown quartz crystal microbalances  

Microsoft Academic Search

ZnO nanorods were directly grown on the surface of a quartz crystal in zinc nitrate hexahydrate solution. The nanorod dimensions were controlled by varying the growth time, from 0.6?m for a growth time of 1h to 2.0?m after 3h of growth. After sequentially coating the nanorod-grown quartz crystals with thin layers of titanium and gold by thermal evaporation, the crystals

Dongkyu Lee; Myungsun Yoo; Hyejung Seo; Youngjo Tak; Wan-Gee Kim; Kijung Yong; Shi-Woo Rhee; Sangmin Jeon

2009-01-01

70

A novel nano-architecture for ZnO thin films on ? 1 0 0 ? Si, GaAs and InP single crystal wafers by L-MBE as value in nano-robotic (machining) device fabrication efforts  

Microsoft Academic Search

In this present work, the effects of various substrate temperatures and various substrates on Zinc Oxide (ZnO) thin film growth and on surface morphological properties were studied. To the best of our knowledge this is the first time that laser molecular beam epitaxy (L-MBE), i.e., pulsed laser deposited (PLD) zinc oxide (ZnO) thin films on semiconductor wafers have been applied

K. Ramamoorthy; C. Sanjeeviraja; M. Jayachandran; K. Sankaranarayanan; V. Ganesan; Pankaj Misra; L. M. Kukreja

2005-01-01

71

Low-Temperature Photoluminescence of Nanostructured ZnO Crystal Synthesized by Pulsed-Laser Ablation  

NASA Astrophysics Data System (ADS)

The optical properties of ZnO nanorods and nanowires grown by our newly developed nanoparticle-assisted pulsed-laser deposition (NAPLD) technique were studied by photoluminescence (PL) spectroscopy. This NAPLD technique, which does not require a catalyst for crystal growth, is expected to synthesize high-quality nanostructured ZnO crystals. The green luminescence (GL) band and ultraviolet luminescence (UVL) observed at low temperature were investigated for these crystals. The UVL band consists of several sharp emission lines due to free excitons, donor-bound excitons, donor-acceptor pair (DAP) transitions, and their longitudinal-optical (LO) phonon replicas. The free-exciton binding energy was estimated to be 59 meV and the band gap of these ZnO crystals was determined to be 3.435 eV at 10 K. The temperature variation for the energy positions of free-exciton emission was fitted by the Manoogian-Woolley equation and the Debye temperature was estimated to be 505 K. The low-temperature PL investigation of our nanostructured ZnO crystals that were easily synthesized by our newly developed NAPLD technique demonstrated their excellent crystallinity.

Sakai, Kentaro; Noguchi, Kohei; Fukuyama, Atsuhiko; Ikari, Tetsuo; Okada, Tatsuo

2009-08-01

72

Effects of interfacial layer structures on crystal structural properties of ZnO films  

SciTech Connect

Single crystalline ZnO films were grown on Cr compound buffer layers on (0001) Al{sub 2}O{sub 3} substrates by plasma assisted molecular beam epitaxy. In terms of lattice misfit reduction between ZnO and substrate, the CrN and Cr{sub 2}O{sub 3}/CrN buffers are investigated. The structural and optical qualities of ZnO films suggest the feasibility of Cr compound buffers for high-quality ZnO films growth on (0001) Al{sub 2}O{sub 3} substrates. Moreover, the effects of interfacial structures on selective growth of different polar ZnO films are investigated. Zn-polar ZnO films are grown on the rocksalt CrN buffer and the formation of rhombohedral Cr{sub 2}O{sub 3} results in the growth of O-polar films. The possible mechanism of polarity conversion is proposed. By employing the simple patterning and regrowth procedures, a periodical polarity converted structure in lateral is fabricated. The periodical change of the polarity is clearly confirmed by the polarity sensitive piezo response microscope images and the opposite hysteretic characteristic of the piezo response curves, which are strict evidences for the validity of the polarity controlling method as well as the successful fabrication of the periodical polarity controlled ZnO structure.

Park, J. S.; Minegishi, T.; Lee, S. H.; Im, I. H.; Park, S. H.; Hanada, T.; Goto, T.; Cho, M. W.; Yao, T.; Hong, S. K.; Chang, J. H. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); School of Nanoscience and Technology, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Major of Nano Semiconductor, Korea Maritime University, Youngdo-ku, Pusan 606-791 (Korea, Republic of)

2008-01-15

73

Laser detection of electrical service safety in a single ZnO nanowire.  

PubMed

The electrically induced quenching of the photoluminescence (PL) intensity and fracture in a single ZnO nanowire were investigated. As the applied voltage increases, the quenching of PL intensity and the red-shift of ultraviolet (UV) emission peak were clearly observed, which are explained by the current-induced Joule heating in the ZnO nanowire. By using this mechanism, the UV laser was successfully used to monitor the safe current density and identify the current-induced fracture in a single ZnO nanowire. PMID:22524017

Yang, Ya; Guo, Wen; Qi, Junjie; Zhao, Jing; Zhang, Yue

2012-01-01

74

Zn(O, S) layers for chalcoyprite solar cells sputtered from a single target  

NASA Astrophysics Data System (ADS)

A simplified Cu(In, Ga)(S, Se)2/Zn(O, S)/ZnO:Al stack for chalcopyrite thin-film solar cells is proposed. In this stack the Zn(O, S) layer combines the roles of the traditional CdS buffer and undoped ZnO layers. It will be shown that Zn(O, S) films can be sputtered in argon atmosphere from a single mixed target without substrate heating. The photovoltaic performance of the simplified stack matches that of the conventional approach. Replacing the ZnO target with a ZnO/ZnS target may therefore be sufficient to omit the CdS buffer layer and avoid the associated complexity, safety and recycling issues, and to lower production cost.

Grimm, A.; Kieven, D.; Lauermann, I.; Lux-Steiner, M. Ch.; Hergert, F.; Schwieger, R.; Klenk, R.

2012-09-01

75

Humidity detection by nanostructured ZnO: A wireless quartz crystal microbalance investigation  

Microsoft Academic Search

In this paper, we present a wireless relative humidity sensor system prototype which based on quartz crystal microbalance (QCM) coated with nanostructured ZnO as sensing element. The wireless QCM sensor system is composed of two parts: the probe based on QCM sensor and the RF receiver. The probe has two functions: to sense and display the frequency signals and to

Xiaofeng Zhou; Jian Zhang; Tao Jiang; Xiaohua Wang; Ziqiang Zhu

2007-01-01

76

Fatigue in Single Crystal Nickel Superalloys.  

National Technical Information Service (NTIS)

This program investigates the behavior of single crystal airfoil materials. The fatigue initiation processes in single crystal materials are significantly more complicated and involved than fatigue initiation and subsequent behavior of a (single) macrocra...

1991-01-01

77

Fatigue in Single Crystal Nickel Superalloys.  

National Technical Information Service (NTIS)

This program investigates the behavior of single crystal airfoil materials. The fatigue initiation processes in single crystal (SC) materials are significantly more complicated and involved than fatigue initiation and subsequent behavior of a (single) mac...

1991-01-01

78

Nanoscale elastic modulus of single horizontal ZnO nanorod using nanoindentation experiment  

NASA Astrophysics Data System (ADS)

We measure the elastic modulus of a single horizontal ZnO nanorod [NR] grown by a low-temperature hydrothermal chemical process on silicon substrates by performing room-temperature, direct load-controlled nanoindentation measurements. The configuration of the experiment for the single ZnO NR was achieved using a focused ion beam/scanning electron microscope dual-beam instrument. The single ZnO NR was positioned horizontally over a hole on a silicon wafer using a nanomanipulator, and both ends were bonded with platinum, defining a three-point bending configuration. The elastic modulus of the ZnO NR, extracted from the unloading curve using the well-known Oliver-Pharr method, resulted in a value of approximately 800 GPa. Also, we discuss the NR creep mechanism observed under indentation. The mechanical behavior reported in this paper will be a useful reference for the design and applications of future nanodevices.

Soomro, Muhammad Yousuf; Hussain, Ijaz; Bano, Nargis; Broitman, Esteban; Nur, Omer; Willander, Magnus

2012-02-01

79

Nanoscale elastic modulus of single horizontal ZnO nanorod using nanoindentation experiment  

PubMed Central

We measure the elastic modulus of a single horizontal ZnO nanorod [NR] grown by a low-temperature hydrothermal chemical process on silicon substrates by performing room-temperature, direct load-controlled nanoindentation measurements. The configuration of the experiment for the single ZnO NR was achieved using a focused ion beam/scanning electron microscope dual-beam instrument. The single ZnO NR was positioned horizontally over a hole on a silicon wafer using a nanomanipulator, and both ends were bonded with platinum, defining a three-point bending configuration. The elastic modulus of the ZnO NR, extracted from the unloading curve using the well-known Oliver-Pharr method, resulted in a value of approximately 800 GPa. Also, we discuss the NR creep mechanism observed under indentation. The mechanical behavior reported in this paper will be a useful reference for the design and applications of future nanodevices.

2012-01-01

80

Optical injection probing of single ZnO tetrapod lasers  

SciTech Connect

The properties of zinc oxide (ZnO) nanotetrapod lasers are characterized by a novel ultrafast two-color pump/stimulated emission probe technique. Single legs of tetrapod species are isolated by a microscope objective, pumped by 267 nm pulses, and subjected to a time-delayed 400 nm optical injection pulse, which permits investigation of the ultrafast carrier dynamics in the nanosize materials. With the optical injection pulse included, a large increase in the stimulated emission at 400 nm occurs, which partially depletes the carriers at this wavelength and competes with the normal 390 nm lasing. At the 390 nm lasing wavelengths, the optical injection causes a decrease in the stimulated emission due to the energetic redistribution of the excited carrier depletion, which occurs considerably within the time scale of the subpicosecond duration of the injection pulse. The effects of the optical injection on the spectral gain are employed to probe the lasing dynamics, which shows that the full width at half maximum of the lasing time is 3 ps.

Szarko, Jodi M.; Song, Jae Kyu; Blackledge, Charles Wesley; Swart, Ingmar; Leone, Stephen R.; Li, Shihong; Zhao, Yiping

2004-11-23

81

Tunable magnetic and transport properties of single crystalline (Co, Ga)-codoped ZnO films  

SciTech Connect

A series of metallic (Co, Ga)-codoped ZnO single crystalline films have been grown by molecular beam epitaxy. All of the films exhibit metallic conducting behavior and high free carrier concentrations. Besides room temperature ferromagnetism, the anomalous Hall effect due to spin-orbit interaction was also found. Both the saturation magnetization and anomalous Hall effect can be tuned by the carrier concentration or conductivity, revealing that the ferromagnetism is carrier mediated in (Co, Ga)-codoped ZnO films. Our experimental observations are consistent with the recent theoretical description of carrier mediated magnetism in Co doped ZnO.

Lu Zhonglin [Department of Physics, National Cheng Kung University, Tainan 701, Taiwan (China); Department of Physics, Southeast University, Nanjing 211189 (China); Institute of Innovations and Advanced Studies (IIAS), National Cheng Kung University, Tainan 701, Taiwan (China); Hsu, H.-S. [Department of Applied Physics, National Ping Tung University of Education, Ping Tung 900, Taiwan (China); Tzeng Yonhua [Institute of Innovations and Advanced Studies (IIAS), National Cheng Kung University, Tainan 701, Taiwan (China); Department of Electrical Engineering, Institute of Microelectronics, National Cheng Kung University, Tainan 701, Taiwan (China); Zhang Fengming; Du Youwei [Department of Physics, Nanjing University, Nanjing 210093 (China); Huang, Jung-Chun-Andrew [Department of Physics, National Cheng Kung University, Tainan 701, Taiwan (China); Institute of Innovations and Advanced Studies (IIAS), National Cheng Kung University, Tainan 701, Taiwan (China)

2009-08-10

82

Antimicrobial mechanism based on H2O2 generation at oxygen vacancies in ZnO crystals.  

PubMed

The production of H2O2 has been taken for a crucial reason for antimicrobial activity of ZnO without light irradiation. However, how the H2O2 generates in ZnO suspension is not clear. In the present work, the comparatively detections on three kinds of ZnO, tetrapod-like ZnO whiskers (t-ZnO), nanosized ZnO particles (n-ZnO), and microsized ZnO particles (m-ZnO), showed that the antimicrobial activity of ZnO was correlated with its production of H2O2. Oxygen vacancy (V(O)) in the surface layer of ZnO crystals determined by XPS indicated that it was quite probably involved in the production of H2O2. To validate the role of V(O), the concentration of VO in t-ZnO was adjusted by heat-treatment under the atmospheres of H2, vacuum, and O2, respectively, and the H2O2 production and antimicrobial effect were detected. Consistently, the t-ZnO treated in H2, which possessed the most V(O) in its crystal, produced the most H2O2 and displayed the best antimicrobial activity. These results provide the basis for developing a more detailed mechanism for H2O2 generation catalyzed by ZnO and for taking greater advantage of this type of antimicrobial agent. PMID:23570415

Xu, Xiaoling; Chen, Dan; Yi, Zhigang; Jiang, Man; Wang, Li; Zhou, Zuowan; Fan, Ximei; Wang, Yong; Hui, David

2013-04-24

83

Fatigue in Single Crystal Nickel Superalloys.  

National Technical Information Service (NTIS)

This program investigates the seemingly unusual behavior of single crystal airfoil materials. The fatigue initiation processes in single crystal (SC) materials are significantly more complicated and involved than fatigue initiation and subsequent behavior...

C. Annis

1992-01-01

84

Fatigue in Single Crystal Nickel Superalloys.  

National Technical Information Service (NTIS)

This program investigates the seemingly unusual behavior of single crystal airfoil materials. The fatigue initiation processes in single crystal (SC) materials are significantly more complicated and involved than fatigue initiation and subsequent behavior...

D. P. DeLuca C. Annis

1991-01-01

85

Fatigue in Single Crystal Nickel Superalloys.  

National Technical Information Service (NTIS)

This program investigates the seemingly unusual behavior of single crystal airfoil materials. The fatigue initiation processes in single crystal (SC) materials are significantly more complicated and involved than fatigue initiation and subsequent behavior...

D. P. DeLuca C. Annis

1993-01-01

86

Fatigue in Single Crystal Nickel Superalloys.  

National Technical Information Service (NTIS)

This program investigates the seemingly unusual behavior of single crystal airfoil materials. The fatigue initiation processes in single crystal (SC) materials are significantly more complicated and involved than fatigue initiation and subsequently behavi...

D. P. DeLuca C. Ann

1992-01-01

87

Fatigue in Single Crystal Nickel Superalloys.  

National Technical Information Service (NTIS)

This program investigates the seemingly unusual behavior of single crystal airfoil materials. The fatigue initiation processes in single crystal (SC) materials are significantly more complicated and involved than fatigue initiation and subsequent behavior...

D. P. DeLuca C. Annis

1994-01-01

88

Octadecanethiol Island Formation on Single Crystal Zinc Oxide Surfaces  

NASA Astrophysics Data System (ADS)

Organic photovoltaic devices, containing ZnO nanorod electron acceptor arrays intercalated with organic polymers, could lead to low-cost solar cells. Surface modifications of ZnO with octadecanethiol (ODT) monolayers have been shown to improve charge transfer in such devices. The present work is an effort to understand these monolayers through studies of ODT on single crystals of ZnO with well-defined oxygen-terminated or zinc-terminated surfaces. Both bare and ODT- functionalized surfaces were characterized with atomic force microscopy, Fourier transform infrared spectroscopy, x-ray photoemission spectroscopy, and water contact angle measurements. ODT seemed to form islands of multilayers on zinc-terminated surfaces and islands of monolayers on oxygen- terminated surfaces. While ODT was expected to preferentially bond along defects and terraces on oxygen-terminated surfaces, this was not observed. ODT was also expected to more effectively bond to the zinc-terminated surface, which was observed. This work was supported by the National Science Foundation Division of Materials Research DMR-0606054, DMR-0907409, and the Renewable Energy Materials Research Science and Engineering Center at the Colorado School of Mines.

Yocom, Andrea; Collins, Reuben; Furtak, Thomas; Baker, Darick; Ohno, Timothy

2010-03-01

89

Octadecanethiol Island Formation on Single Crystal Zinc Oxide Surfaces  

NASA Astrophysics Data System (ADS)

Organic photovoltaic devices, comprised of zinc oxide (ZnO) nanorod electron acceptor arrays intercalated with organic polymers, could lead to low-cost renewable energy generation. Surface modifications of ZnO with octadecanethiol (ODT) monolayers can help to improve charge transfer in such devices. In the present work, single crystals of ZnO provided well-defined oxygen-terminated and zinc-terminated surfaces on which to learn fundamentally about the attachment and growth of ODT. Both bare zinc oxide and ODT-functionalized surfaces were characterized with atomic force microscopy, Fourier transform infrared spectroscopy, x-ray photoemission spectroscopy, and contact angle analysis. ODT seemed to form islands of multilayers on zinc-terminated surfaces, while it formed islands of monolayers on oxygen-terminated surfaces. While ODT was expected to preferentially bond along defects and terraces on oxygen-terminated surfaces, this was not observed. ODT was also expected to more effectively bond to the zinc-terminated surface, which was observed. Finally, surface preparation treatments designed to leave atomically-flat oxygen terminated surfaces were developed. This work was made possible by the National Science Foundation Division of Materials Research and the Renewable Energy Materials Research Science and Engineering Center at the Colorado School of Mines.

Yocom, Andrea

2009-10-01

90

Three-dimensional Bragg coherent diffraction imaging of an extended ZnO crystal1  

PubMed Central

A complex three-dimensional quantitative image of an extended zinc oxide (ZnO) crystal has been obtained using Bragg coherent diffraction imaging integrated with ptychography. By scanning a 2.5?m-long arm of a ZnO tetrapod across a 1.3?m X-ray beam with fine step sizes while measuring a three-dimensional diffraction pattern at each scan spot, the three-dimensional electron density and projected displacement field of the entire crystal were recovered. The simultaneously reconstructed complex wavefront of the illumination combined with its coherence properties determined by a partial coherence analysis implemented in the reconstruction process provide a comprehensive characterization of the incident X-ray beam.

Huang, Xiaojing; Harder, Ross; Leake, Steven; Clark, Jesse; Robinson, Ian

2012-01-01

91

Dependence of the gas sensing properties of ZnO nanowires on their microstructure  

NASA Astrophysics Data System (ADS)

Two different types of ZnO nanowires were synthesized by the thermal evaporation of different material powders: ZnS powders for ZnO nanowires A; and a mixture of ZnO and graphite powders for ZnO nanowires B. ZnO nanowires A were found to have a bamboo structure consisting of many hexagonal plates each of which is a single crystal, whereas ZnO nanowires B were single crystals with no grain boundary at all. ZnO nanowires B had a far higher degree of preferred orientation than ZnO nanowires A. The sensing properties of ZnO nanowires A were superior to those of ZnO nanowires B in terms of the sensing response and sensing speed. ZnO nanowires A showed an approximately 440 % response at 5 ppm NO2 at 300 C, whereas ZnO nanowires B showed an approximately 150 % response under the same condition. ZnO nanowires A showed considerably shorter response and recovery times than ZnO nanowires B under the same condition. The superior sensing properties of ZnO nanowires A compared to ZnO nanowires B can be explained mainly by carrier modulation of the depletion layer formed across the grain boundaries of nanowires A.

Park, Sunghoon; An, Soyeon; Jin, Changhyun; Lee, Chongmu

2012-07-01

92

Thermoelectric nanogenerators based on single Sb-doped ZnO micro/nanobelts.  

PubMed

We demonstrate a thermoelectric nanogenerator (NG) made from a single Sb-doped ZnO micro/nanobelt that generates an output power of about 1.94 nW under a temperature difference of 30 K between the two electrodes. A single Sb-doped ZnO microbelt was bonded at its ends on a glass substrate as a NG, which can give an output voltage of 10 mV and an output current of 194 nA. The single Sb-doped ZnO microbelt shows a Seebeck coefficient of about -350 ?V/K and a high power factor of about 3.2 10(-4) W/mK(2). The fabricated NG demonstrated its potential to work as a self-powered temperature sensor with a reset time of about 9 s. PMID:22742540

Yang, Ya; Pradel, Ken C; Jing, Qingshen; Wu, Jyh Ming; Zhang, Fang; Zhou, Yusheng; Zhang, Yue; Wang, Zhong Lin

2012-07-10

93

Hydrothermal synthesis and gas sensing properties of single-crystalline ultralong ZnO nanowires  

NASA Astrophysics Data System (ADS)

Ultralong ZnO nanowires were successfully synthesized by a simple hydrothermal reaction of Zn foil and aqueous Na2C2O4 solution at 140C. The as-synthesized ZnO nanowires are single crystalline with the wurtzite structure and grow in the [0001] direction. The role of Na2C2O4 in the formation of ultralong ZnO nanowires was investigated, and a possible mechanism was also proposed to account for the formation of the ultralong ZnO nanowires. The gas sensor fabricated on the basis of the ultralong ZnO nanowires showed excellent response characteristics towards NH3 and N(C2H5)3 vapors with low concentration, and its detection limits for NH3 and N(C2H5)3 are about 0.2 and 0.15 ppm at the working temperature of 180C, respectively. This result suggests potential applications of the ultralong ZnO nanowires in monitoring flammable, toxic and corrosive gases.

Li, Li; Yang, Heqing; Zhao, Hua; Yu, Jie; Ma, Junhu; An, Lijuan; Wang, Xuewen

2010-03-01

94

Photovoltaic device on a single ZnO nanowire p-n homojunction.  

PubMed

A photovoltaic device was successfully grown solely based on the single ZnO p-n homojunction nanowire. The ZnO nanowire p-n diode consists of an as-grown n-type segment and an in situ arsenic-doped p-type segment. This p-n homojunction acts as a good photovoltaic cell, producing a photocurrent almost 45 times larger than the dark current under reverse-biased conditions. Our results demonstrate that the present ZnO p-n homojunction nanowire can be used as a self-powered ultraviolet photodetector as well as a photovoltaic cell, which can also be used as an ultralow electrical power source for nanoscale electronic, optoelectronic and medical devices. PMID:22383446

Cho, Hak Dong; Zakirov, Anvar S; Yuldashev, Shavkat U; Ahn, Chi Won; Yeo, Yung Kee; Kang, Tae Won

2012-03-23

95

Ultraprecision diamond turning of aluminium single crystals  

Microsoft Academic Search

Ultraprecision diamond turning is an important technology to generate a high surface finish in precision components and optics. In this paper, the diamond turning of aluminium single crystal rods with crystallographic axes normal to , and is analysed. The effect of the crystallographic anisotropy on the machining of these single crystals is investigated in the light of the mechanics of

S. To; W. B. Lee; C. Y. Chan

1997-01-01

96

Protein Single Crystal Growth under Microgravity  

NASA Astrophysics Data System (ADS)

The preparation of suitably large protein single crystals is essentially the rate-determining step of protein x-ray structure determinations. Attempts to produce single crystals with two model compounds--? -galactosidase and lysozyme--under conditions of microgravity were successful. Crystals formed by salting out from solutions kept free of convection were 27 and 1000 times larger in volume, respectively, than those produced in the same apparatus but exposed to terrestrial gravitation.

Littke, Walter; John, Christina

1984-07-01

97

Morphologically Controlled Electrodeposition of ZnO and Cu2O by the Colloidal Crystal Template Method  

NASA Astrophysics Data System (ADS)

This paper presents a versatile method for fabricating 3D macroporous materials using colloidal crystals as the templates. ZnO and Cu2O were deposited by the electrochemical method via the colloidal crystal template. Not only were 3D inverse opal structures and 2D nanobowls fabricated, but nanoparticles with a controlled shape were also prepared. Morphological controls via colloidal crystal templating are discussed.

Fu, Ming; Zhao, Ailun; Zhou, Ji; He, Dawei; Wang, Yongsheng

98

Adhesion of single crystals on modified surfaces in crystallization fouling  

NASA Astrophysics Data System (ADS)

In crystallization fouling it has been observed that during a certain initial phase the fouling is formed by a non-uniform layer consisting of a population of single crystals. These single crystals are frequently formed by inverse soluble salts such as CaCO3. During heterogeneous nucleation and heterogeneous growth an interfacial area between the crystal and the heat transfer surface occurs. The development of this interfacial area is the reason for the adhesion of each single crystal and of all individual crystals, once a uniform layer has been built up. The emerging interfacial area is intrinsic to the heterogeneous nucleation of crystals and can be explained by the thermodynamic principle of the minimum of the Gibbs free energy. In this study CaCO3 crystals were grown heterogeneously on untreated and on modified surfaces inside a flow channel. An untreated stainless steel (AISI 304) surface was used as a reference. Following surface modifications were investigated: enameled and electropolished stainless steel as well as diamond-like-carbon based coatings on stainless steel substrate. The adhesion was measured through a novel measurement technique using a micromanipulator to shear off single crystals from the substrate which was fixed to a spring table inside a SEM.

Mayer, Moriz; Augustin, Wolfgang; Scholl, Stephan

2012-12-01

99

Characterizations of Ohmic and Schottky-behaving contacts of a single ZnO nanowire.  

PubMed

Current-voltage and Kelvin probe force microscopy (KPFM) measurements were performed on single ZnO nanowires. Measurements are shown to be strongly correlated with the contact behavior, either Ohmic or diode-like. The ZnO nanowires were obtained by metallo-organic chemical vapor deposition (MOCVD) and contacted using electronic-beam lithography. Depending on the contact geometry, good quality Ohmic contacts (linear I-V behavior) or non-linear (diode-like) contacts were obtained. Current-voltage and KPFM measurements on both types of contacted ZnO nanowires were performed in order to investigate their behavior. A clear correlation could be established between the I-V curve, the electrical potential profile along the device and the nanowire geometry. Some arguments supporting this behavior are given based on technological issues and on depletion region extension. This work will help to better understand the electrical behavior of Ohmic contacts on single ZnO nanowires, for future applications in nanoscale field-effect transistors and nano-photodetectors. PMID:24060613

Bercu, Bogdan; Geng, Wei; Simonetti, Olivier; Kostcheev, Sergei; Sartel, Corinne; Sallet, Vincent; Lrondel, Gilles; Molinari, Michal; Giraudet, Louis; Couteau, Christophe

2013-09-24

100

Characterizations of Ohmic and Schottky-behaving contacts of a single ZnO nanowire  

NASA Astrophysics Data System (ADS)

Current-voltage and Kelvin probe force microscopy (KPFM) measurements were performed on single ZnO nanowires. Measurements are shown to be strongly correlated with the contact behavior, either Ohmic or diode-like. The ZnO nanowires were obtained by metallo-organic chemical vapor deposition (MOCVD) and contacted using electronic-beam lithography. Depending on the contact geometry, good quality Ohmic contacts (linear I-V behavior) or non-linear (diode-like) contacts were obtained. Current-voltage and KPFM measurements on both types of contacted ZnO nanowires were performed in order to investigate their behavior. A clear correlation could be established between the I-V curve, the electrical potential profile along the device and the nanowire geometry. Some arguments supporting this behavior are given based on technological issues and on depletion region extension. This work will help to better understand the electrical behavior of Ohmic contacts on single ZnO nanowires, for future applications in nanoscale field-effect transistors and nano-photodetectors.

Bercu, Bogdan; Geng, Wei; Simonetti, Olivier; Kostcheev, Sergei; Sartel, Corinne; Sallet, Vincent; Lrondel, Gilles; Molinari, Michal; Giraudet, Louis; Couteau, Christophe

2013-10-01

101

ZnO nanowire lasers  

NASA Astrophysics Data System (ADS)

The pathway towards the realization of optical solid-state lasers was gradual and slow. After Einstein's paper on absorption and stimulated emission of light in 1917 it took until 1960 for the first solid state laser device to see the light. Not much later, the first semiconductor laser was demonstrated and lasing in the near UV spectral range from ZnO was reported as early as 1966. The research on the optical properties of ZnO showed a remarkable revival since 1995 with the demonstration of room temperature lasing, which was further enhanced by the first report of lasing by a single nanowire in 2001. Since then, the research focussed increasingly on one-dimensional nanowires of ZnO. We start this review with a brief description of the opto-electronic properties of ZnO that are related to the wurtzite crystal structure. How these properties are modified by the nanowire geometry is discussed in the subsequent sections, in which we present the confined photon and/or polariton modes and how these can be investigated experimentally. Next, we review experimental studies of laser emission from single ZnO nanowires under different experimental conditions. We emphasize the special features resulting from the sub-wavelength dimensions by presenting our results on single ZnO nanowires lying on a substrate. At present, the mechanism of lasing in ZnO (nanowires) is the subject of a strong debate that is considered at the end of this review.

Vanmaekelbergh, Danil; van Vugt, Lambert K.

2011-07-01

102

Photoemission from Germanium Single Crystals.  

National Technical Information Service (NTIS)

Studies of band structure of germanium by using photoemission have been reported recently by Donovan and Spicer and Donovan. Some new experimental results of electronic structures of simple crystal germanium are presented here. Principal results are as fo...

J. Matsuzaki

1970-01-01

103

Single Crystal Sapphire Optical Fiber Sensor Instrumentation  

SciTech Connect

The goal of this 30 month program is to develop reliable accurate temperature sensors based on single crystal sapphire materials that can withstand the temperatures and corrosive agents present within the gasifier environment. The research for this reporting period has been segregated into two parallel paths--corrosion resistance measurements for single crystal sapphire fibers and investigation of single crystal sapphire sensor configurations. The ultimate goal of this phase one segment is to design, develop and demonstrate on a laboratory scale a suitable temperature measurement device that can be field tested in phase two of the program.

Anbo Wang; Russell May; Gary R. Pickrell

2000-10-28

104

Effect of ZnO nanoparticles on the SmC*-SmA* phase transition temperature in electroclinic liquid crystals  

NASA Astrophysics Data System (ADS)

ZnO nanoparticles (NPs), synthesized in an alcoholic medium at room temperature, were added to electroclinic liquid crystal (ELC) materials. The addition of ZnO NPs in ELCs, caused a remarkable shift in SmC*-SmA* phase transition which was investigated from the dielectric and electro-optical measurements. The anchoring of ELC molecules around ZnO NPs creates orientational distortions near the surface, which may give additional ordering to the ELC molecular arrangement. After analyzing collective dielectric relaxation processes of ZnO NP doped ELCs, three distinct loss peaks were observed. The different behavior of ZnO NP doped ELC from pure ELC has been explained by determining the dielectric strength, the distribution parameter and the corresponding relaxation frequency, and so on, and then these results have been compared with the data calculated by using the theoretical model. The effect of ZnO NPs addition on physical parameters, such as spontaneous polarization (Ps) and rotational viscosity (?) has also been observed.

Malik, A.; Choudhary, A.; Silotia, P.; Biradar, A. M.

2011-09-01

105

Local lattice distortions in single Co-implanted ZnO nanowires  

NASA Astrophysics Data System (ADS)

This work reports on the local structure of as-implanted and thermally-treated single Co:ZnO nanowires studied using a hard X-ray nanoprobe. Although the Co ions are incorporated into the wurtzite ZnO lattice, X-ray absorption near edge structure data show high structural disorder in the as-implanted nanowires compared with the annealed ones. In particular, extended X-ray absorption fine structure from single wires reveals a lattice distortion around Zn sites of the as-implanted nanowires, which involves an expansion of the stable wurtzite lattice. The observed local lattice response confirms good recovery of the implantation-induced damage within the ZnO lattice through a thermal treatment.

Chu, M. H.; Martnez-Criado, G.; Segura-Ruiz, J.; Geburt, S.; Ronning, C.

2013-09-01

106

Hydrothermal growth and characterization of nitrogen-doped ZnO crystals  

NASA Astrophysics Data System (ADS)

Hydrothermal growth of nitrogen-doped ZnO crystals was performed in alkaline solutions with the addition of 1 N LiNO3 at T/T=365C/350C, and in a 20% NH4OH solution at 490 C/475 C, respectively. An average nitrogen concentration of approximately 1018 atom/cm3 was incorporated in the crystals. X-ray diffraction showed that the crystals grown from the 1 M LiNO3 solution are of high quality, exhibiting high resistivity. The spontaneously nucleated crystals were obtained from the NH4OH solution; a weak peak at 3.236 eV and a peak at 3.332 eV of photoluminescence were found at 18 K from these crystals after annealing at 600 C for 2 h. The emission peaks correspond to the nitrogen-associated donor acceptor pair (DAP) and electron-acceptor emissions in ZnO:N prepared by other techniques reported in the literature.

Wang, Buguo; Callahan, M. J.; Bouthillette, L. O.; Xu, Chunchuan; Suscavage, M. J.

2006-01-01

107

Coherent X-ray Diffraction Imaging for Strain Analysis on Single ZnO Nanorod  

NASA Astrophysics Data System (ADS)

Strain induced in nanostructure semiconductor materials can result in different electronic properties. Coherent x-ray diffraction (CXD) has emerged as a non-destructive tool for imaging of strain and defects. In this work CXD is applied on a single ZnO nanorod, diffraction patterns from Bragg reflection are used to reconstruct the strain distribution in the samples at a resolution of 40 nm.

Xiong, Gang; Leake, S.; Newton, M. C.; Huang, X.; Harder, R.; Robinson, Ian K.

2011-12-01

108

Selective growth of single-crystalline ZnO nanowires on doped silicon  

Microsoft Academic Search

We report the growth of single-crystalline ZnO nanowires on n- and p-type Si wafers by electrodeposition. On strongly doped n-type Si high-quality nanowires can be grown under similar conditions as used for metallic substrates. For low electron concentrations occurring in weakly n-type or in p-type wafers, nanowire growth is inhibited. This difference allows selective growth in strongly n-type areas. The

R. Knenkamp; R. C. Word; M. Dosmailov; J. Meiss; A. Nadarajah

2007-01-01

109

Synthesis and characterization of ZnO nanorods by a simple single-source hydrothermal method  

Microsoft Academic Search

By using Zn(acac)2H2O as a single-source precursor, ZnO nanorods have been synthesized via a simple hydrothermal method in the presence of surfactant. The nanorods with an average diameter of 100nm and a length up to 5?m were characterized by X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), and UVvis spectrum.

Li Tang; Xiao-Bo Bao; Hu Zhou; Ai-Hua Yuan

2008-01-01

110

Optical Absorption of TNT Single Crystals.  

National Technical Information Service (NTIS)

A method for growing large area, thin, single crystal platelets of TNT is reported. The optical absorption properties of these crystals were studied, and dichroic behavior was observed. The absorption edge is approximately 3.1 eV and is tentatively assign...

A. C. Forsyth D. S. Downs

1973-01-01

111

Single Crystal Diamond Nanomechanical Dome Resonator.  

National Technical Information Service (NTIS)

Superior mechanical and optical properties of single crystal (SC) diamond in combination with a chemically inert and bio-compatible surface enable the design and fabrication of novel nanoscale devices for sensing and signal processing applications. In thi...

B. B. Pate J. Yang J. E. Butler J. W. Baldwin M. K. Zalalutdinov

2008-01-01

112

Single Crystal NMR of High Temperature Superconductors  

Microsoft Academic Search

The author reports Cu NMR studies of the high temperature superconductor YBa_2Cu _3O_{7-delta } (T_{rm c} = 90K) using a 1 mg single crystal. Three types of measurements have been made for both the \\

Charles Holloway Pennington

1989-01-01

113

Computational Techniques in Single Crystal Mossbauer Spectroscopy.  

National Technical Information Service (NTIS)

The report summarizes some computational techniques which can be used to extract the effective field parameters from a given single crystal Mossbauer spectrum. The effective field parameters in this case are the effective electric field gradient and magne...

K. P. Singh G. R. Hoy

1969-01-01

114

NEXAFS and XMCD studies of single-phase Co doped ZnO thin films  

NASA Astrophysics Data System (ADS)

A study of the electronic structure and magnetic properties of Co doped ZnO thin films synthesized by ion implantation followed by swift heavy ion irradiation is presented using near-edge x-ray absorption fine structure (NEXAFS) and x-ray magnetic circular dichroism (XMCD) measurements. The spectral features of NEXAFS at the Co L3,2-edge show entirely different features than that of metallic Co clusters and other Co oxide phases. The atomic multiplet calculations are performed to determine the valence state, symmetry and the crystal field splitting, which show that in the present system Co is in the 2+ state and substituted at the Zn site in tetrahedral symmetry with 10Dq = -0.6 eV. The ferromagnetic character of these materials is confirmed through XMCD spectra. To rule out the possibilities of defect induced magnetism, the results are compared with Ar annealed and Ar-ion implanted pure ZnO thin films. The presented results confirm the substitution of Co at the Zn site in the ZnO matrix, which is responsible for room temperature ferromagnetism.

Singh, Abhinav Pratap; Kumar, Ravi; Thakur, P.; Brookes, N. B.; Chae, K. H.; Choi, W. K.

2009-05-01

115

Characterization of Single Grain Boundaries in a Bi-Doped ZnO Varistor Using a Focused Ion Beam System  

NASA Astrophysics Data System (ADS)

This report presents a new method for electrically characterizing single grain boundary junctions of ZnO varistors. For the first time to our knowledge, a focused ion beam system was used to deposit tungsten microelectrodes on two adjacent ZnO grains. Gallium ions irradiated onto the ZnO surface lowered the resistivity of the ZnO, and therefore highly nonlinear current-voltage (I-V) characteristics of single grain boundaries could be obtained after etching the gallium-irradiated ZnO surface with HClO4 solution. Breakdown voltages in the I-V characteristics were observed in the range from 2.6 V to 3.2 V within the same ZnO varistor. The grain boundary with the breakdown voltage of 3.2 V was structurally different from that of 2.6 V@. The boundary with the breakdown voltage of 3.2 V contained precipitates and a thin, amorphous Bi-segregated layer about 1 nm thick. On the other hand, the boundary with the voltage of 2.6 V contained no precipitate but rather, a thin, amorphous Bi-segregated layer about 0.5 nm thick. It was suggested that the electrical characteristics of grain boundary junctions within the ZnO varistors are strongly dependent upon the microstructure of the grain boundary.

Tanimura, Junji; Wada, Osamu; Kurokawa, Hiroshi; Furuse, Naomi; Kobayashi, Masahiro

2000-07-01

116

Effects of Hydrogen Dilution on ZnO Thin Films Fabricated via Nitrogen-Mediated Crystallization  

NASA Astrophysics Data System (ADS)

Hydrogenated ZnO thin films have been successfully deposited on glass substrates via a nitrogen mediated crystallization (NMC) method utilizing RF sputtering. Here we aim to study the crystallinity and electrical properties of hydrogenated NMC-ZnO films in correlation with substrate temperature and H2 flow rate. XRD measurements reveal that all the deposited films exhibit strongly preferred (001) orientation. The integral breadth of the (002) peak from the hydrogenated NMC-ZnO films is smaller than that of the conventional hydrogenated ZnO films fabricated without nitrogen. Furthermore, the crystallinity and surface morphology of the hydrogenated NMC-ZnO films are improved by increasing substrate temperature to 400 C, where the smallest integral breadth of (002) 2?--? scans of 0.83 has been obtained. By utilizing the hydrogenated NMC-ZnO films as buffer layers, the crystallinity of ZnO:Al (AZO) films is also improved. The resistivity of AZO films on NMC-ZnO buffer layers decreases with increasing H2 flow rate during the sputter deposition of buffer layers from 0 to 5 sccm. At a H2 flow rate of 5 sccm, 20-nm-thick AZO films with low resistivity of 1.5 10-3 ? cm have been obtained.

Suhariadi, Iping; Matsushima, Koichi; Kuwahara, Kazunori; Oshikawa, Koichi; Yamashita, Daisuke; Seo, Hyunwoong; Uchida, Giichiro; Kamataki, Kunihiro; Koga, Kazunori; Shiratani, Masaharu; Bornholdt, Sven; Kersten, Holger; Wulff, Harm; Itagaki, Naho

2013-01-01

117

Light-matter interaction and polarization of single ZnO nanowire lasers.  

PubMed

The optical properties of single zinc oxide (ZnO) nanolasers are investigated. ZnO nanowires with different diameters and lengths are prepared by chemical vapor transport. The diameter plays an important role in the stimulated emission process in nanowires. The spectral shift and spacing of Fabry-Prot-type modes imply a strong light-matter interaction in the lasing nanowires, which is explained by the exciton-polariton model. The polarization of the electric field in the lasing nanowires is perpendicular to the long axis of the nanowire and parallel to the substrate plane. The coexistence of the transverse modes is distinguished by decomposing the peak shape and the degree of polarization. In addition to the transverse mode of the lasing with the polarization parallel to the substrate plane, the lasing mode with the polarization perpendicular to the substrate plane is observed. PMID:22751811

Han, Noh Soo; Shim, Hyeong Seop; Lee, Seulki; Park, Seung Min; Choi, Myong Yong; Song, Jae Kyu

2012-07-02

118

Single ZnO nanowire-PZT optothermal field effect transistors.  

PubMed

A new type of pyroelectric field effect transistor based on a composite consisting of single zinc oxide nanowire and lead zirconate titanate (ZnO NW-PZT) has been developed. Under infrared (IR) laser illumination, the transconductance of the ZnO NW can be modulated by optothermal gating. The drain current can be increased or decreased by IR illumination depending on the polarization orientation of the Pb(Zr(0.3)Ti(0.7))O(3) (PZT) substrate. Furthermore, by combining the photocurrent behavior in the UV range and the optothermal gating effect in the IR range, the wide spectrum of response of current by light offers a variety of opportunities for nanoscale optoelectronic devices. PMID:22895012

Hsieh, Chun-Yi; Lu, Meng-Lin; Chen, Ju-Ying; Chen, Yung-Ting; Chen, Yang-Fang; Shih, Wan Y; Shih, Wei-Heng

2012-08-15

119

Cutting fluid study for single crystal silicon  

Microsoft Academic Search

An empirical study was conducted to evaluate cutting fluids for Single Point Diamond Turning (SPDT) of single crystal silicon. The pH of distilled waster was adjusted with various additives the examine the effect of pH on cutting operations. Fluids which seemed to promote ductile cutting appeared to increase tool wear as well, an undesirable tradeoff. High Ph sodium hydroxide solutions

Chargin

1998-01-01

120

Piezoelectric anisotropy of orthorhombic ferroelectric single crystals  

NASA Astrophysics Data System (ADS)

In the frame of thermodynamic approach, it is shown that all the admissible values of the d33, d32, and d31 piezoelectric moduli of any orthorhombic (mm2) single crystal in the 3-dimensional (d33, d32, d31) space lie within a restricted area having the form of ellipsoid. The main parameters of this ellipsoid (the aspect ratios and the angles characterizing its orientation) depend only on the elastic constants of the crystal. Using the developed approach, the areas of the allowable values of piezoelectric moduli have been determined for six crystals: single-domain KNbO3 and 0.27Pb(In0.5Nb0.5)O3-0.40Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 crystals possessing true orthorhombic symmetry and four polydomain macroscopically pseudoorthorhombic crystals--tetragonal BaTiO3 and PbTiO3 crystals with laminate 90 domain structure as well as rhombohedral 0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 and 0.93Pb(Zn1/3Nb2/3)O3-0.07PbTiO3 crystals, poled along the [011] direction of the prototype cubic cell. Four crystals from this set possess negative values of the longitudinal Poisson's ratio and are thus partially auxetics.

Aleshin, V. I.; Raevski, I. P.

2013-06-01

121

Single crystal fibers for high power lasers  

NASA Astrophysics Data System (ADS)

In this paper, we present our recent results in developing cladded-single crystal fibers for high power single frequency fiber lasers significantly exceeding the capabilities of existing silica fiber based lasers. This fiber laser would not only exploit the advantages of crystals, namely their high temperature stability, high thermal conductivity, superior environmental ruggedness, high propensity for rare earth ion doping and low nonlinearity, but will also provide the benefits from an optical fiber geometry to enable better thermal management thereby enabling the potential for high laser power output in short lengths. Single crystal fiber cores with diameters as small as 35?m have been drawn using high purity rare earth doped ceramic or single crystal feed rods by Laser Heated Pedestal Growth (LHPG) process. The mechanical, optical and morphological properties of these fibers have been characterized. The fibers are very flexible and show good overall uniformity. We also measured the optical loss as well as the non-radiative loss of the doped crystal fibers and the results show that the fibers have excellent optical and morphological quality. The gain coefficient of the crystal fiber matches the low quantum defect laser model and it is a good indication of the high quality of the fibers.

Kim, W.; Florea, C.; Baker, C.; Gibson, D.; Shaw, L. B.; Bowman, S.; O'Connor, S.; Villalobos, G.; Bayya, S.; Aggarwal, I. D.; Sanghera, J. S.

2012-11-01

122

Neutron detection with single crystal organic scintillators  

NASA Astrophysics Data System (ADS)

Detection of high-energy neutrons in the presence of gamma radiation background utilizes pulse-shape discrimination (PSD) phenomena in organics studied previously only with limited number of materials, mostly liquid scintillators and single crystal stilbene. The current paper presents the results obtained with broader varieties of luminescent organic single crystals. The studies involve experimental tools of crystal growth and material characterization in combination with the advanced computer modeling, with the final goal of better understanding the relevance between the nature of the organic materials and their PSD properties. Special consideration is given to the factors that may diminish or even completely obscure the PSD properties in scintillating crystals. Among such factors are molecular and crystallographic structures that determine exchange coupling and exciton mobility in organic materials and the impurity effect discussed on the examples of trans-stilbene, bibenzyl, 9,10- diphenylanthracene and diphenylacetylene.

Zaitseva, Natalia P.; Newby, Jason; Hamel, Sebastien; Carman, Leslie; Faust, Michelle; Lordi, Vincenzo; Cherepy, Nerine J.; Stoeffl, Wolfgang; Payne, Stephen A.

2009-08-01

123

Neutron detection with single crystal organic scintillators  

SciTech Connect

Detection of high-energy neutrons in the presence of gamma radiation background utilizes pulse-shape discrimination (PSD) phenomena in organics studied previously only with limited number of materials, mostly liquid scintillators and single crystal stilbene. The current paper presents the results obtained with broader varieties of luminescent organic single crystals. The studies involve experimental tools of crystal growth and material characterization in combination with the advanced computer modeling, with the final goal of better understanding the relevance between the nature of the organic materials and their PSD properties. Special consideration is given to the factors that may diminish or even completely obscure the PSD properties in scintillating crystals. Among such factors are molecular and crystallographic structures that determine exchange coupling and exciton mobility in organic materials and the impurity effect discussed on the examples of trans-stilbene, bibenzyl, 9,10-diphenylanthracene and diphenylacetylene.

Zaitseva, N; Newby, J; Hamel, S; Carman, L; Faust, M; Lordi, V; Cherepy, N; Stoeffl, W; Payne, S

2009-07-15

124

Single-Crystal-to-Single-Crystal Transformations in One Dimensional Ag-Eu Helical System  

SciTech Connect

Single-crystal-to-single-crystal transformation of 1-D 4d-4f coordination polymers have been investigated for the first time. It displays high selectivity for Mg2+ and can be used as magnesium ion-selective luminescent probe. More importantly, we observed the transformation of meso-helical chain to rac-helical chain as a function of temperature.

Cai, Yue-Peng; Zhout, Xiu-Xia; Zhout, Zheng-Yuan; Zhu, Shi-Zheng; Thallapally, Praveen K.; Liu, Jun

2009-07-06

125

Electroluminescence Studies in Pyrene Single Crystals  

Microsoft Academic Search

The observation of electroluminescence in pyrene single crystals is reported. Holes and electrons were introduced into the samples by contact injection using CuI and Na-Hg amalgam electrodes as hole and electron injectors, respectively. The radiation-recombination light intensity is found to be directly proportional to the current through the crystal. The yield for light emission is about 2 10 photons

J. Gonzalez Basurto; Z. Burshtein

1975-01-01

126

Single crystal NMR of high temperature superconductors  

Microsoft Academic Search

Cu NMR studies of the high temperature superconductor YBa2Cu3O(7-delta) (T sub c = 90 K) using a 1 mg single crystal is reported. Three types of measurements were made for both the plane and chain Cu crystallographic sites and with the static magnetic field placed successively along each of the three crystal axes a, b, and c: nuclear magnetic resonance

Charles Holloway Pennington

1989-01-01

127

Diluted magnetism in Mn-doped SrZnO2 single crystals  

NASA Astrophysics Data System (ADS)

We have investigated the magnetic properties of Mn- and Cu-substituted SrZnO2 single crystals (SrZn1-xMnxO2 and SrZn1-xCuxO2). We observed signatures of weak ferromagnetism as a sharp increase of magnetic susceptibility below 5 K even in the low-percentage (x = 0.01) of Mn-substituted single crystals. Magnetic susceptibility data measured parallel or perpendicular to the ab-plane yield anisotropic behavior with Curie-Weiss temperature of about -320 K and -410 K, respectively, suggesting the presence of strong antiferromagnetic couplings among Mn at high temperatures, similar to the Mn-doped ZnO and Fe-doped BaTiO3. In contrast, the SrZn0.99Cu0.01O2 crystal shows paramagnetic behavior down to 2 K.

Rahman, M. R.; Koteswararao, B.; Huang, S. H.; Hoon Kim, Kee; Chou, F. C.

2013-09-01

128

Inkjet printing of single-crystal films.  

PubMed

The use of single crystals has been fundamental to the development of semiconductor microelectronics and solid-state science. Whether based on inorganic or organic materials, the devices that show the highest performance rely on single-crystal interfaces, with their nearly perfect translational symmetry and exceptionally high chemical purity. Attention has recently been focused on developing simple ways of producing electronic devices by means of printing technologies. 'Printed electronics' is being explored for the manufacture of large-area and flexible electronic devices by the patterned application of functional inks containing soluble or dispersed semiconducting materials. However, because of the strong self-organizing tendency of the deposited materials, the production of semiconducting thin films of high crystallinity (indispensable for realizing high carrier mobility) may be incompatible with conventional printing processes. Here we develop a method that combines the technique of antisolvent crystallization with inkjet printing to produce organic semiconducting thin films of high crystallinity. Specifically, we show that mixing fine droplets of an antisolvent and a solution of an active semiconducting component within a confined area on an amorphous substrate can trigger the controlled formation of exceptionally uniform single-crystal or polycrystalline thin films that grow at the liquid-air interfaces. Using this approach, we have printed single crystals of the organic semiconductor 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C(8)-BTBT) (ref. 15), yielding thin-film transistors with average carrier mobilities as high as 16.4?cm(2)?V(-1)?s(-1). This printing technique constitutes a major step towards the use of high-performance single-crystal semiconductor devices for large-area and flexible electronics applications. PMID:21753752

Minemawari, Hiromi; Yamada, Toshikazu; Matsui, Hiroyuki; Tsutsumi, Jun'ya; Haas, Simon; Chiba, Ryosuke; Kumai, Reiji; Hasegawa, Tatsuo

2011-07-13

129

Lateral induced dipole moment and polarizability of excitons in a ZnO single quantum disk  

NASA Astrophysics Data System (ADS)

The lateral Stark shift of an exciton confined in a single ZnO quantum thin disk of radius R was calculated using a variational approach within the two bands effective mass approximation. It is shown that the exciton has a non negligible induced dipole moment when an external electric field is applied mainly for electron-hole separation below to the 3D excitonic Bohr radius. The behavior of the exciton lateral Stark shift proves the existence of an important correlation between the polarizability and the induced dipole moment.

Dujardin, F.; Feddi, E.; Oukerroum, A.; Bosch Bailach, J.; Martnez-Pastor, J.; Assaid, E.

2013-02-01

130

Single-crystalline ZnO nanowires grown on silicon wafers  

Microsoft Academic Search

We report electrodeposition of single-crystalline ZnO nanowires on Si wafers. Similar wires grown on conductive SnO2\\/glass substrates show excellent electro-luminescence with visible and ultra-violet spectral contributions. For high doping levels in the n-type Si substrates high-quality nanowires can be grown. For low electron concentrations occurring in weakly n-type wafers or in p-type wafers, nanowire growth is inhibited. For B-doped p-type

R. Konenkamp; R. Word; M. Dosmailov

2006-01-01

131

Temperature dependence of photoconductivity and persistent photoconductivity of single ZnO nanowires  

NASA Astrophysics Data System (ADS)

Photoelectrical properties of single ZnO nanowires have been investigated using photocurrent-voltage characteristics measurements varying with excitation photon energy and temperature. It is found that persistent photoconductivity (PPC) exists, and the PPC decreases with decreasing temperature. The temperature dependence of the PPC effect indicates that thermally activated return of electrons from shallow traps is responsible for the PPC phenomenon. The photosensitivity is found to be linear with the applied voltage, and it increases with decreasing temperature. A temperature dependence of photoconductivity gain was introduced to explain the experimental results.

Liao, Zhi-Min; Lu, Yi; Xu, Jun; Zhang, Jing-Min; Yu, Da-Peng

2009-05-01

132

Emission bands of nitrogen-implantation induced luminescent centers in ZnO crystals: Experiment and theory  

NASA Astrophysics Data System (ADS)

High quality ZnO crystals with the sharp band-edge excitonic emission and very weak green emission were implanted by nitrogen ions. An additional red emission band was observed in the as-implanted ZnO crystal and investigated as a function of temperature. By employing the underdamped multimode Brownian oscillator model for the general electron-phonon coupling system, both the original green and nitrogen-implantation induced red emission bands were theoretically reproduced at different temperatures. Excellent agreement between the theory and the experiment enables us determine the energetic positions of the pure electronic levels associated with the green and red emission bands, respectively. The determined energy level of the red emission band is in good agreement with the data obtained from the deep-level transient spectroscopy measurements.

Dai, X. M.; Xu, S. J.; Ling, C. C.; Brauer, G.; Anwand, W.; Skorupa, W.

2012-08-01

133

Nano-turning of single crystal silicon  

Microsoft Academic Search

High-quality silicon surfaces have been obtained by single-point diamond turning. After the analysis of the turning mechanism, the relationship between the surface integrity and the turning parameters was studied in detail. Results from the mechanism were compared with turning tests on silicon using a commercially available single-crystal diamond tool with a rake angle of 0. A novel technique was developed

F. Z Fang

1998-01-01

134

Three-dimensional single crystal silicon micromachining  

Microsoft Academic Search

A monolithic, multiple-level (ML), single-crystal-silicon (SCS) micromachining process called SCREAM3D has been developed. The high-aspect-ratio (HAR) levels are self-aligned and are fabricated from a single substrate by deep etching. Anisotropic reactive ion etching of silicon has been studied in detail and new recipes for the vertical etch and release of HAR ML structures have been developed. The SCREAM3D levels are

Wolfgang Maximilian Josef Hofmann

1999-01-01

135

Single Crystal Diffraction by Synchrotron Radiation.  

National Technical Information Service (NTIS)

The tunability and access to short wavelengths in combination with high intensity and the low divergence of the x-ray radiation produced by synchrotron storage rings opens up new and challenging fields for single crystal diffraction. These areas include m...

A. Kvick

1988-01-01

136

Development of single crystal filaments. Final report  

Microsoft Academic Search

The program just completed addresses a route to a more efficient longer-lasting electric light bulb filament. All current filaments for light bulbs are metallic in nature. They are subject to embrittlement with age (large grain growth) and relatively high vapor pressures which limits their operating temperature. There is evidence which suggests advantages to using high temperature refractory single crystal fibers

J. V. Milewski; R. A. Shoultz; M. M. Bourque-McConnell

1995-01-01

137

Single crystal tungsten kinetic energy penetrators  

SciTech Connect

We have explored the terminal ballistic performance of single crystal tungsten as a kinetic energy penetrator. Scientific speculation as to the anticipated penetration performance and nature of the interaction between such a kinetic energy penetrator and semi-infinite and spaced metallic targets has led us to perform laboratory scale experiments and metallographic examinations of post-impact penetrator materials. The single tungsten crystals were ground into kinetic energy penetrators with the {l_angle}111{r_angle} and {l_angle}100{r_angle} crystal direction being coincident with the axis of symmetry of the penetrators. The crystals were electro-polished to their final diameter. We, compared the terminal performance at current ordnance speeds of {l_angle}111{r_angle} single crystal tungsten to 90W-10 (NiFe) cemented tungsten and textured pure tungsten in laboratory scale ballistic experiments against a spaced steel (triple) target at sixty-five degrees obliquity. We also compared the terminal performance of {l_angle}100{r_angle} and {l_angle}111{r_angle} single crystal tungsten with 90W-10 and 98W02 (NiFe) cemented tungsten and textured pure tungsten in laboratory scale ballistic experiments against monolithic 4340 alloy steel (HRC = 36) at normal impact. We radiographed the penetrators during the interactions with the targets, we recovered portions of the penetrators after the ballistic experiments, and we conducted metallographic examinations of penetrator remnants. From the radiographic records and the metallographic examinations, we drew conclusions pertaining to insights into the terminal interactions of the penetrators with the targets and suggestions as to improved compositions of the cemented tungsten penetrators.

Cline, C.F.; Gogolewski, R.P.

1992-05-01

138

Single crystal tungsten kinetic energy penetrators  

SciTech Connect

We have explored the terminal ballistic performance of single crystal tungsten as a kinetic energy penetrator. Scientific speculation as to the anticipated penetration performance and nature of the interaction between such a kinetic energy penetrator and semi-infinite and spaced metallic targets has led us to perform laboratory scale experiments and metallographic examinations of post-impact penetrator materials. The single tungsten crystals were ground into kinetic energy penetrators with the [l angle]111[r angle] and [l angle]100[r angle] crystal direction being coincident with the axis of symmetry of the penetrators. The crystals were electro-polished to their final diameter. We, compared the terminal performance at current ordnance speeds of [l angle]111[r angle] single crystal tungsten to 90W-10 (NiFe) cemented tungsten and textured pure tungsten in laboratory scale ballistic experiments against a spaced steel (triple) target at sixty-five degrees obliquity. We also compared the terminal performance of [l angle]100[r angle] and [l angle]111[r angle] single crystal tungsten with 90W-10 and 98W02 (NiFe) cemented tungsten and textured pure tungsten in laboratory scale ballistic experiments against monolithic 4340 alloy steel (HRC = 36) at normal impact. We radiographed the penetrators during the interactions with the targets, we recovered portions of the penetrators after the ballistic experiments, and we conducted metallographic examinations of penetrator remnants. From the radiographic records and the metallographic examinations, we drew conclusions pertaining to insights into the terminal interactions of the penetrators with the targets and suggestions as to improved compositions of the cemented tungsten penetrators.

Cline, C.F.; Gogolewski, R.P.

1992-05-01

139

In-Situ Studies of Photoluminescence Quenching in Single Crystal Quantum Dot Sensitized Solar Cells  

NASA Astrophysics Data System (ADS)

Single crystal quantum dot sensitized solar cells (QDSSC) are a promising photovoltaic system in which collection of multiple charge carriers per photon has recently been reported.ootnotetextJustin B. Sambur, Thomas Novet, B.A. Parkinson, Science 330 (6000) 63-66 Utilizing time-correlated single photon counting we have studied both the fluorescence intensity and fluorescence decay time from CdSe quantum dots coupled to both single crystal TiO2 and ZnO substrates through short and long chain ligands. We find that for all configurations the fluorescence decay time is quenched compared to unbound quantum dots in solution, while the photovoltaic properties of the system strongly depend on the chain-length of the ligand. These results suggest there exist interactions between either the individual quantum dots or the quantum dots and substrate that may compete with the charge injection process in QDSSCs.

Shepherd, Douglas; Liang, Yong-Qi; Sambur, Justin; Parkinson, Bruce; Gelfand, Martin; van Orden, Alan

2011-03-01

140

Single-crystal disk drive miniactuators  

NASA Astrophysics Data System (ADS)

As hard disk drive areal densities increase at a compound annual growth rate (CAGR) of 60%, disk drives must position the head over increasingly small areas while moving more rapidly to reach the desired position. This results in an increase in vibration disturbance. To meet this demand, many hard disk drive manufactures have created prototype dual-stage actuators employing piezoelectric ceramics for the second stage. These are an attractive means of obtaining higher-bandwidth control due to the low inertia and size of the actuator element. As the technology improves, the next limiting factor will be the amount of displacement obtainable with traditional piezoceramic elements. Under the AXIS (Advanced Crystal Integrated System) Consortium program funded by DARPA, the application of PZN-PT single crystal piezoceramic as a second stage disk drive actuator was studied, based on the fact that the single crystal material provides larger stroke than its traditional PZT counterparts. The transverse (d31) strain of PZN-PT single crystal was measured to be about two times larger than that of PZT-5H ceramic. Both materials were integrated into a disk drive system and compared as second stage actuators. The methodologies used and the servo control techniques applied are also discussed in the paper.

Giovanardi, Marco; McKenney, Kevin; Rule, John A.; Yoshikawa, Shoko

2001-08-01

141

Study of defects in pentacene single crystals  

NASA Astrophysics Data System (ADS)

Our research focuses on the growth of the pentacene single crystals with a high degree of purity, and the investigation of their morphology and physical properties. We are able to reduce the number of traps by two orders of magnitude compared with conventional methods. This is reflected in the value of hole mobility of 35 cm2/Vs at room temperature increasing to 58 cm2/Vs at 225 K. These high mobilities result from a purification of the material, that consists of removal of 6,13-pentacenequinone, as the major impurity, using vacuum sublimation under a temperature gradient. We further study the influence of air exposure on the electronic properties of pentacene single crystals. Our observations show that gases can diffuse reversibly in/out the crystals, and influence the electronic properties. We discern two competing mechanisms that modulate the electronic transport. On the one hand stands the presence of water from ambient air that intercalates into the crystal lattice and forms trapping sites for injected charges. On the other hand, the presence of oxygen increases the hole conduction. The latter effect is enhanced by the presence of visible light.

Jurchescu, Oana D.

2005-03-01

142

Single ZnO nanotetrapod-based sensors for monitoring localized UV irradiation.  

PubMed

Single ZnO nanotetrapod-based sensors for monitoring localized UV irradiation were constructed with ohmic and Schottky contact characteristics. Localized UV irradiation at the third leg of the tetrapod was monitored by measuring the sensor's current response. Measurements of I-V performances and time-resolved current were conducted. The results demonstrate that localized UV irradiation can be detected in real time as electrical transport properties can be modulated by localized UV irradiation, and the higher the UV light power density gets, the larger the current response becomes, which is observed to be completely repeatable and reversible. Additionally, Schottky-contact type sensors clearly show a greater current response than ohmic-contact-type sensors, which further proved that Schottky-contact-type sensors are a better choice for detection in an irradiation environment. Two possible explanations are given for the phenomenon, including an electron transfer effect and a surface/interface effect on the band structure. The as-constructed sensors exhibit different sensitivities towards irradiation with various power densities, indicating that ZnO nanotetrapod-based sensors can be a promising candidate for detection in many areas including electron irradiation detection, ultraviolet irradiation monitoring, strain sensing, and complicated microenvironment observations such as biological cell inspection. PMID:23712693

Wang, Wenhua; Qi, Junjie; Wang, Qinyu; Huang, Yunhua; Liao, Qingliang; Zhang, Yue

2013-05-28

143

Single ZnO nanotetrapod-based sensors for monitoring localized UV irradiation  

NASA Astrophysics Data System (ADS)

Single ZnO nanotetrapod-based sensors for monitoring localized UV irradiation were constructed with ohmic and Schottky contact characteristics. Localized UV irradiation at the third leg of the tetrapod was monitored by measuring the sensor's current response. Measurements of I-V performances and time-resolved current were conducted. The results demonstrate that localized UV irradiation can be detected in real time as electrical transport properties can be modulated by localized UV irradiation, and the higher the UV light power density gets, the larger the current response becomes, which is observed to be completely repeatable and reversible. Additionally, Schottky-contact type sensors clearly show a greater current response than ohmic-contact-type sensors, which further proved that Schottky-contact-type sensors are a better choice for detection in an irradiation environment. Two possible explanations are given for the phenomenon, including an electron transfer effect and a surface/interface effect on the band structure. The as-constructed sensors exhibit different sensitivities towards irradiation with various power densities, indicating that ZnO nanotetrapod-based sensors can be a promising candidate for detection in many areas including electron irradiation detection, ultraviolet irradiation monitoring, strain sensing, and complicated microenvironment observations such as biological cell inspection.

Wang, Wenhua; Qi, Junjie; Wang, Qinyu; Huang, Yunhua; Liao, Qingliang; Zhang, Yue

2013-06-01

144

Porosity evolution in a creeping single crystal  

NASA Astrophysics Data System (ADS)

Experimental observations on tensile specimens in Srivastava et al (2012 in preparation) indicated that the growth of initially present processing induced voids in a nickel-based single crystal superalloy played a significant role in limiting creep life. Also, creep tests on single crystal superalloy specimens typically show greater creep strain rates and/or reduced creep life for thinner specimens than predicted by current theories. In order to quantify the role of void growth in single crystals in creep loading, we have carried out three-dimensional finite deformation finite element analyses of unit cells containing a single initially spherical void. The materials are characterized by a rate-dependent crystal plasticity constitutive relation accounting for primary and secondary creep. Two types of imposed loading are considered: an applied true stress (force/unit current area) that is time independent; and an applied nominal stress (force/unit initial area) that is time independent. Isothermal conditions are assumed. The evolution of porosity is calculated for various values of stress triaxiality and of the Lode parameter. The evolution of porosity with time is sensitive to whether constant true stress or constant nominal stress loading is applied. However, the evolution of porosity with the overall unit cell strain is insensitive to the mode of loading. At high values of stress triaxiality, the response is essentially independent of the value of the Lode parameter. At sufficiently low values of the stress triaxiality, the porosity evolution depends on the value of the Lode parameter and void collapse can occur. Also, rather large stress concentrations can develop which could play a role in the observed thickness dependence.

Srivastava, A.; Needleman, A.

2012-04-01

145

Single Crystal Metals Encapsulated in Carbon Nanoparticles  

Microsoft Academic Search

Single-domain microcrystals of LaC_2 encapsulated within nanoscale polyhedral carbon particles have been synthesized in a carbon arc. Typical particle sizes are on the order of 20 to 40 nanometers. The stoichiometry and phase of the La-containing crystals have been assigned from characteristic lattice spacings observed by high-resolution transmission electron microscopy and energy dispersive spectroscopy (EDS). EDS spectra show that La

Rodney S. Ruoff; Donald C. Lorents; Bryan Chan; Ripudaman Malhotra; Shekhar Subramoney

1993-01-01

146

The single crystal elastic moduli of neighborite  

Microsoft Academic Search

The adiabatic elastic moduli of a single crystal of Neighborite (NaMgF3perovskite) have been measured at ambient conditions using Brillouin spectroscopy. The adiabatic aggregate (Voight-Reuss-Hill) bulk modulus is K = 75.6 GPa, and shear modulus is = 46.7 GPa. The experimental results show the ratio of linear compressibilities b\\/a = 0.80 for neighborite. These ratios reflect the different amounts of

Yusheng Zhao; Donald J. Weidner

1993-01-01

147

Thermal properties of UO2 single crystal  

NASA Astrophysics Data System (ADS)

For decades UO2 has been the most widely studied actinide oxide because of its technological importance as fuel material for nuclear reactors. Therefore there is a large interest in understanding its thermal, transport and thermodynamic properties. We present recent experimental results for the thermal conductivity and thermal expansion of high quality UO2 single crystal, obtained for different crystallographic directions, and compare with results of molecular dynamics simulations. We will discuss the implications of this study.

Gofryk, K.; Du, S.; Andersson, A. D.; Stanek, C. R.; Schulze, R.; Safarik, D.; Mihaila, B.; Lashley, J. C.; Smith, J. L.

2013-03-01

148

Bridgman growth of paratellurite single crystals  

Microsoft Academic Search

The growth of paratellurite single crystals by the vertical-gradient freezing technique is reported for the first time. Boules of 120mm long and 25mm in diameter were obtained under a temperature gradient of 10Ccm?1 and translation rates lower than 0.6mmh?1. The spatial distribution of defects along the growth axis reveals a continuous evolution of the free convective fluid-flow regime as growth

P. Veber; J. Mangin; P. Strimer; P. Delarue; C. Josse; L. Saviot

2004-01-01

149

Single crystal diffraction by synchrotron radiation  

SciTech Connect

The tunability and access to short wavelengths in combination with high intensity and the low divergence of the x-ray radiation produced by synchrotron storage rings opens up new and challenging fields for single crystal diffraction. These areas include microcrystal diffraction, studies of time-dependent phenomena, element selective diffraction, studies of materials under extreme conditions, solution of the crystallographic phase problem either by the use of the wavelength dependency of the anomalous scattering or by direct experimental determination of the phases. Single crystal diffraction from proteins and macromolecules using photographic film as a detection medium has already reached considerable maturity, but high-precision data collections using diffractometers at storage rings are still not routine because of the severe requirements for beam stability over extended periods of time. Development work at institutions such as the National Synchrotron Light Source, The Photon Factory, SSRL, CHESS, Hasylab and Daresbury, however, suggest that synchrotron single-crystal diffraction will become an essential part of the research at the synchrotron storage rings in the near future. 9 refs., 2 figs.

Kvick, A.

1988-01-01

150

Properties of electrical contacts on bulk and epitaxial n-type ZnO  

Microsoft Academic Search

The electrical properties of several metal contacts to n-type ZnO (0001) were studied. The ZnO samples consisted of bulk single-crystal\\u000a material, epitaxial layers on sapphire grown by molecular beam epitaxy (MBE), and polycrystalline thin films on sapphire obtained\\u000a by pulsed laser deposition (PLD). Ohmic and rectifying contacts were observed dependent upon both the metal material and the\\u000a ZnO surface. Ohmic

T. E. Murphy; J. O. Blaszczak; K. Moazzami; W. E. Bowen; J. D. Phillips

2005-01-01

151

Fatigue In Single Crystal Nickel Superalloys Technical Progress Report.  

National Technical Information Service (NTIS)

This program investigates the seemingly unusual behavior of single crystal airfoil materials. The fatigue initiation processes in single crystal (SC) materials are significantly more complicated and involved than fatigue initiation and subsequent behavior...

C. Annis

1992-01-01

152

Single crystal x-ray diffraction: optical and micro hardness studies on chalcone derivative single crystal  

NASA Astrophysics Data System (ADS)

1-(4-methylphenyl)-3-(4- N, N dimethyl amino phenyl)-2-propen-1-one, a chalcone derivative nonlinear optical material has been synthesized by standard method. FT-IR and NMR spectral studies have been performed to confirm the molecular structure of the synthesized compound. The single crystals up to a dimension of 13 x 9 x 3 mm3 were grown by slow evaporation method. The grown crystals were transparent in the entire visible region and absorbs in the UV-region. The refractive index has been measured using a He-Ne laser. The grown crystals have been subjected to single crystal X-ray diffraction studies to determine the crystal structure and hence the cell parameters of the crystal. From this study it is found that this compound crystallizes in orthorhombic system with a space group P212121 and corresponding lattice parameters are, a = 7.3610(13) , b = 11.651(2) , c = 17.6490(17) . The Kurtz powder second harmonic generation test shows that the compound is a potential candidate for Photonic application. The micro hardness test on these crystals were carried out and the load dependence hardness was observed

Crasta, Vincent; Ravindrachary, V.; Bhajantri, R. F.; Naveen, S.; Shridar, M. A.; Shashidhara Prasad, J.

2005-08-01

153

Ion-Irradiation-Induced Ferromagnetism in Undoped ZnO Thin Films.  

National Technical Information Service (NTIS)

We have introduced defects in ZnO epitaxial thin films by swift heavy (expn 107)Ag(expn 9+) ion irradiation and investigated systematically their magnetic, electrical and optical properties. Oxygen annealed ZnO films are epitaxial single crystals that exh...

D. K. Avasthi J. Narayan J. T. Prater S. Mal S. Nori

2013-01-01

154

Fatigue behavior of a single crystal nickel-base superalloy  

Microsoft Academic Search

While the creep properties of single crystal nickel base superalloys are known to be superior to that of polycrystalline superalloys, the behavior of single crystals in low cycle fatigue (LCF) is less well understood. In this study the low cycle fatigue properties of an experimental single crystal nickel-based superalloy, Rene N4, were examined at 1400 F and 1800 F in

T. P. Gabb; J. Gayda; R. V. Miner

2008-01-01

155

Radical-Beam Gettering Epitaxy of ZnO Films under UV Irradiation  

Microsoft Academic Search

Single-crystal ZnO films are grown by radical-beam gettering epitaxy: annealing of single-crystal zinc chalcogenide (ZnS, ZnSe, or ZnTe) substrates in a flow of oxygen atoms (radicals) and gettering of zinc atoms from the substrate bulk. The effect of UV irradiation during film growth on the structure and quality of the resulting ZnO films and the effect of ion implantation into

A. N. Georgobiani; M. B. Kotlyarevsky; I. V. Rogozin; A. V. Marakhovskii

2005-01-01

156

Optical characterization of organic semiconducting single crystals  

NASA Astrophysics Data System (ADS)

Over the last decade interest in the possibility of "plastic electronics," semi-conducting organic materials that hold the potential for display devices with improved characteristics, has increased. To date, the majority of research has focused on material development and device design. However, if scientists are able to understand the connection between the structural and electronic properties of molecules, they can tailor new compounds with desired physical characteristics. Optical characterization is the first step to understanding the structural properties of materials. This work focuses on characterizing single crystals of two specific molecules: alpha-hexathiophene and 5,6,11,12-tetraphenyl tetracene (rubrene). While there is plenty of information currently available in the literature about alpha-hexathiophene, the resonant Raman experiments I describe in Chapter 3 have uncovered the lowest experimentally-recorded excited electronic levels. I have tentatively identified these states as either a triplet Frenkel exciton or a bound singlet Frenkel exciton. Chapter 4 details how I used Raman, infrared and photoluminescence spectroscopy, as well as computer simulations, to characterize rubrene. Studies of tetracene single crystals helped guide the understanding of the structural and electronic properties of rubrene. Although all molecular crystals have low intermolecular coupling, my analysis showed that rubrene has particularly low coupling, even for a molecular crystal. This result goes against commonly held belief that the best molecules for "plastic electronic" devices should have strong pi-electron overlap. The temperature dependent photoluminescence spectrum clearly reveals emission from free carriers as well as free charge transfer excitons, free Frenkel excitons and deep impurity and defect levels.

Weinberg-Wolf, Jennifer

157

Electrodeposition of single and duplex layers of ZnO with different morphologies and electrical properties  

Microsoft Academic Search

ZnO films have been prepared by electrodeposition from aqueous solutions. Dense, nanostructured and doped samples can be prepared by changing the composition of the electrolytic bath and fine-tuning the electrochemical parameters. Duplex layers can also be produced, with a nanostructured ZnO layer electrodeposited using as the substrate a previously prepared dense or In-doped ZnO layer. The films are deposited potentiostatically

M. Berruet; M. Vzquez

2010-01-01

158

Octahedral multiple-twin model of tetrapod ZnO crystals  

Microsoft Academic Search

The characteristic morphology of tetrapod-shaped ZnO particles grown by oxidizing zinc vapour in air has been thoroughly interpreted by a growth process from octahedral multiple-twin embryos. The origin of the tetrapod-shape arises from firstly the formation of octahedral multiple twins due to the small c\\/a ratio of wurtzite ZnO, secondly the presence of in version-type twin boundaries and thirdly a

S. Takeuchi; H. Iwanaga; M. Fujii

1994-01-01

159

Advanced piezoelectric single crystal based actuators  

Microsoft Academic Search

TRS is developing new actuators based on single crystal piezoelectric materials such as Pb(Zn1\\/3Nb2\\/3)1-xTixO3 (PZN-PT) and Pb(Mg1\\/3Nb2\\/3)x-1TixO3 (PMN-PT) which exhibit very high piezoelectric coefficients (d33 = 1800-2200 pC\\/N) and electromechanical coupling factors (k33 > 0.9), respectively, for a variety of applications, including active vibration damping, active flow control, high precision positioning, ultrasonic motors, deformable mirrors, and adaptive optics. The d32

Xiaoning Jiang; Paul W. Rehrig; Wesley S. Hackenberger; Edward Smith; Shuxiang Dong; Dwight Viehland; Jim Moore Jr.; Brian Patrick

2005-01-01

160

Fabrication of single-crystal diamond microcomponents  

SciTech Connect

We have combined a technique for the lift-off of thin diamond films from a bulk diamond with a technique for engraving diamond with a focused excimer laser to produce free-standing single-crystal diamond microstructures. One microcomponent that has been produced is a 12 tooth gear [similar to]400 [mu]m in diameter and [similar to]13 [mu]m thick. Other microstructures have also been demonstrated, showing the versatility of this method. This process should be applicable to producing diamond microcomponents down to spatial dimensions (width and thickness) of a few micrometers.

Hunn, J.D.; Withrow, S.P.; White, C.W.; Clausing, R.E.; Heatherly, L. (Oak Ridge National Laboratory, Bldg 5500 MS-6376, Oak Ridge, Tennessee 37831-6376 (United States)); Christensen, C.P. (Potomac Photonics, Lanham, Maryland 20705 (United States))

1994-12-12

161

Metallisation of single crystal diamond radiation detectors  

NASA Astrophysics Data System (ADS)

Properties such as a large band gap, high thermal conductivity and resistance to radiation damage make diamond an extremely attractive candidate for detectors in next generation particle physics experiments. This paper presents our technique for metallisation of a single crystal diamond grown by chemical vapour deposition (CVD) for use as a radiation detector, suitable for operation in places such as the Large Hadron Collider. The front and back side of the diamond are metalised with aluminium and gold on top of titanium respectively, after which the diamond is mounted and read out via a charge sensitive preamplifier. The device is found to collect charge at an efficiency of 97%.

Ong, Lucas; Ganesan, Kumaravelu; Alves, Andrew; Barberio, Elisabetta

2012-10-01

162

Characterisation of single-crystal mercuric iodide  

NASA Astrophysics Data System (ADS)

The mobility-lifetime product of electrons and holes in single-crystal mercuric iodide for detector applications was measured to be 410-5 and 310-5 cm2/V respectively. The charge carriers were optically induced by a near band gap excitation using a GaP (560nm) light emitting diode. Optical Deep Level Transient Spectrometry measurements of trapping states showed three dominant energy levels at 0.26, 0.8 and 1.4eV. There is little correlation between trapping levels reported in the literature.

Alexiev, D.; Dytlewski, N.; Reinhard, M. I.; Mo, L.

2004-01-01

163

Ultrahigh-quality silicon carbide single crystals  

NASA Astrophysics Data System (ADS)

Silicon carbide (SiC) has a range of useful physical, mechanical and electronic properties that make it a promising material for next-generation electronic devices. Careful consideration of the thermal conditions in which SiC {0001} is grown has resulted in improvements in crystal diameter and quality: the quantity of macroscopic defects such as hollow core dislocations (micropipes), inclusions, small-angle boundaries and long-range lattice warp has been reduced. But some macroscopic defects (about 1-10cm-2) and a large density of elementary dislocations (~ 104cm-2), such as edge, basal plane and screw dislocations, remain within the crystal, and have so far prevented the realization of high-efficiency, reliable electronic devices in SiC (refs 12-16). Here we report a method, inspired by the dislocation structure of SiC grown perpendicular to the c-axis (a-face growth), to reduce the number of dislocations in SiC single crystals by two to three orders of magnitude, rendering them virtually dislocation-free. These substrates will promote the development of high-power SiC devices and reduce energy losses of the resulting electrical systems.

Nakamura, Daisuke; Gunjishima, Itaru; Yamaguchi, Satoshi; Ito, Tadashi; Okamoto, Atsuto; Kondo, Hiroyuki; Onda, Shoichi; Takatori, Kazumasa

2004-08-01

164

Cutting fluid study for single crystal silicon  

SciTech Connect

An empirical study was conducted to evaluate cutting fluids for Single Point Diamond Turning (SPDT) of single crystal silicon. The pH of distilled waster was adjusted with various additives the examine the effect of pH on cutting operations. Fluids which seemed to promote ductile cutting appeared to increase tool wear as well, an undesirable tradeoff. High Ph sodium hydroxide solutions showed promise for further research, as they yielded the best combination of reduced tool wear and good surface finish in the ductile regime. Negative rake tools were verified to improve the surface finish, but the negative rake tools used in the experiments also showed much higher wear than conventional 0{degree} rake tools. Effects of crystallographic orientation on SPDT, such as star patterns of fracture damage forming near the center of the samples, were observed to decrease with lower feedrates. Silicon chips were observed and photographed, indicative of a ductile materials removal process.

Chargin, D.

1998-05-05

165

Zinc self-diffusion, electrical properties, and defect structure of undoped, single crystal zinc oxide  

SciTech Connect

Zinc self-diffusion was measured in single crystal zinc oxide using nonradioactive {sup 70}Zn as the tracer isotope and secondary ion mass spectrometry for data collection. Crystal mass was closely monitored to measure ZnO evaporation. Diffusion coefficients were isotropic with an activation energy of 372 kJ/mol. Zinc self-diffusion is most likely controlled by a vacancy mechanism. Electrical property measurements exhibit a plateau in conductivity at intermediate pO{sub 2} with an increase in reducing atmospheres. An analysis of the defect structure is presented that indicates that oxygen vacancies are probably the intrinsic ionic defects responsible for n-type conductivity in reducing atmospheres. (c) 2000 American Institute of Physics.

Tomlins, Gregory W. [Energy Technology Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208 (United States); Routbort, Jules L. [Energy Technology Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Mason, Thomas O. [Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208 (United States)

2000-01-01

166

Single crystal NMR of high temperature superconductors  

SciTech Connect

Cu NMR studies of the high temperature superconductor YBa2Cu3O(7-delta) (T sub c = 90 K) using a 1 mg single crystal is reported. Three types of measurements were made for both the plane and chain Cu crystallographic sites and with the static magnetic field placed successively along each of the three crystal axes a, b, and c: nuclear magnetic resonance (NMR) lineshapes, spin-lattice relaxation, and transverse relaxation. From these measurements four NMR tensors are deduced: the magnetic shift tensor, the electric field gradient tensor, the spin-lattice relaxation rate tensor, and the transverse relaxation rate tensor. As a preliminary matter, the symmetries of the magnetic shift and electric field gradient tensors were used to assign the two families of NMR lines to their respective crystallographic sites. From an analysis of the electric field gradient tensors it is shown that both the plane and chain Cu have valences Cu(2+), giving a single hold in the Cu atomic d-shell. The spin-lattice relaxation rate and magnetic shift of the plane and chain Cu were analyzed; included were both analyses in which only normal state data were considered, and in which superconducting state measurements of magnetic shifts were considered as well. These analyses show that the plane Cu atom behaves very nearly as a local moment. The chain Cu is probably also in the local moment limit; however, its NMR properties are largely determined by its interaction with oxygen holes in the chain.

Pennington, C.H.

1989-01-01

167

Preparation of ferrite single crystals by new floating zone technique  

Microsoft Academic Search

Single crystals of Ni ferrites and Ni-Zn ferrites having good uniformity were prepared by a new floating zone technique. In the preparation of the Ni-ferrite single crystal the initial molten zone was made from the material having a composition different from that of seed crystal. This made the composition of precipitate from molten zone the same as that of the

T. Akashi; K. Matumi; T. Okada; T. Mizutani

1969-01-01

168

Self-powered ultraviolet photodetector based on a single ZnO tetrapod/PEDOT:PSS heterostructure  

NASA Astrophysics Data System (ADS)

A new ultraviolet (UV) photodetector based on a single ZnO tetrapod and PEDOT:PSS heterostructure was constructed and investigated. At zero bias, the detector showed an on/off ratio of ?1100, a rise time of ?3.5 s and a decay time of ?4.5 s when the 325 nm UV (0.16 mW) illuminated the pn heterojunction. The self-powered properties were driven by the photovoltaic effect, with a short-circuit current of ?1.1 nA, an open-circuit voltage of ?0.2 V and a fill factor of ?25%. Furthermore, self-powered properties were also found when the UV irradiated the ZnO tetrapod only, and the short-circuit current and the open-circuit voltage decreased with the increasing distance between the illuminated spot at the ZnO tetrapod and the heterojunction. The mechanisms for the performances of the detector were examined and discussed. In consideration of the multiterminal feature of ZnO tetrapods, our work provides a possible new approach to developing independent and multifunctional nanodevices.

Yi, Fang; Liao, Qingliang; Huang, Yunhua; Gu, Yousong; Zhang, Yue

2013-10-01

169

Mode Gruneisen Parameters for Single Crystal Al2O3.  

National Technical Information Service (NTIS)

Single crystal Al2O3 (sapphire or corundum), crystallizes in the trigonal lattice, point group 3m. Its thermodynamic properties have been extensively investigated over the last years. As the pressure derivatives of its elastic moduli have recently become ...

D. Gerlich

1969-01-01

170

CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Centimetre-Long Single Crystalline ZnO Fibres Prepared by Vapour Transportation  

NASA Astrophysics Data System (ADS)

Centimetre-long ZnO fibres are synthesized by vapour transportation via thermal evaporation of ZnO powders. The growth process is carried out in a graphite crucible, in which ZnO powder is loaded as the source material, and a silicon wafer is positioned on the top of the crucible as the growth substrate. During the growth process, the source temperature is kept at 800 C, and the substrate temperature is kept at 600 C. Typical growth time to obtain centimetre-long ZnO fibres is 5-10 hours. Scanning electron microscopy (SEM), x-ray diffraction (XRD), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) measurement results show that ZnO fibres are single crystalline with high crystalline quality and very low defects concentration.

Ji, Zhen-Guo; Hao, Fang; Wang, Chao; Xi, Jun-Hua

2008-09-01

171

Experimental dynamic metamorphism of mineral single crystals  

USGS Publications Warehouse

This paper is a review of some of the rich and varied interactions between non-hydrostatic stress and phase transformations or mineral reactions, drawn mainly from results of experiments done on mineral single crystals in our laboratory or our co-authors. The state of stress and inelastic deformation can enter explicitly into the equilibrium phase relations and kinetics of mineral reactions. Alternatively, phase transformations can have prominent effects on theology and on the nature of inelastic deformation. Our examples represent five types of structural phase changes, each of which is distinguished by particular mechanical effects. In increasing structural complexity, these include: (1) displacive phase transformations involving no bond-breaking, which may produce anomalous brittle behavior. A primary example is the a-?? quartz transition which shows anomalously low fracture strength and tertiary creep behavior near the transition temperature; (2) martensitic-like transformations involving transformation strains dominated by shear deformation. Examples include the orthoenstatite ??? clinoenstatite and w u ??rtzite ??? sphalerite transformations; (3) coherent exsolution or precipitation of a mineral solute from a supersaturated solid-solution, with anisotropy of precipitation and creep rates produced under nonhydrostatic stress. Examples include exsolution of corundum from MgO ?? nAl2O3 spinels and Ca-clinopyroxene from orthopyroxene; (4) order-disorder transformations that are believed to cause anomalous plastic yield strengthening, such as MgO - nAl2O3 spinels; and (5) near-surface devolatilization of hydrous silicate single-crystals that produces a fundamental brittleness thought to be connected with dehydration at microcracks at temperatures well below nominal macroscopic dehydration temperatures. As none of these interactions between single-crystal phase transformations and non-hydrostatic stress is understood in detail, this paper serves as a challenge to field structural geologists to test whether interactions of these types occur in nature, and to theoreticians to reach a deeper understanding of the complex relations between phase transformations, the local state of stress and associated deformation and deformation rates. ?? 1993.

Kirby, S. H.; Stern, L. A.

1993-01-01

172

Optical properties of hydrothermal-method-grown ZnO crystal as EUV laser diagnostics material  

NASA Astrophysics Data System (ADS)

Photoluminescence properties of hydrothermal method-grown zinc oxide (ZnO) are evaluated in the extreme ultraviolet (EUV) region. The prominent fluorescence peak observed at 380 nm is characterized by a double exponential decay profile, where the 1.6 ns fast decay component is attributed to free excitons while the 15 ns slow decay component is assigned to trapped carriers. The response time of ZnO is improved to 70 ps by intentional iron (Fe) ion doping accomplished through the removal of the platinum lining in the growth chamber. This response time-improved ZnO will have promising applications in EUV lithography and X-ray free electron laser (XFEL) research.

Yamanoi, Kohei; Shimizu, Toshihiko; Furukawa, Yusuke; Cadatal-Raduban, Marilou; Nakazato, Tomoharu; Sakai, Kohei; Tsuboi, Mizuki; Nishi, Ryosuke; Sarukura, Nobuhiko; Tanaka, Momoko; Nishikino, Masaharu; Yamatani, Hiroshi; Nagashima, Keisuke; Kimura, Toyoaki; Fukuda, Tsuguo; Nagasono, Mitsuru; Togashi, Tadashi; Higashiya, Atsushi; Yabashi, Makina; Ishikawa, Tetsuya; Ohashi, Haruhiko; Kimura, Hiroaki

2013-01-01

173

Mechanical properties of single crystal YAg  

SciTech Connect

YAg, a rare earth-precious metal 'line compound', is one member of the family of B2 rare earth intermetallic compounds that exhibit high ductilities. Tensile tests of polycrystalline YAg specimens have produced elongations as high as 27% before failure. In the present work, single crystal specimens of YAg with the B2, CsCl-type crystal structure were tensile tested at room temperature. Specimens with a tensile axis orientation of [0 1 1-bar] displayed slip lines on the specimen faces corresponding to slip on the {l_brace}1 1 0{r_brace}<0 1 0> with a critical resolved shear stress of 13 MPa. A specimen with a tensile axis orientation of [1 0 0] showed no slip lines and began to crack at a stress of 300 MPa. The test specimens also displayed some slip lines whose position corresponded to slip on the {l_brace}1 0 0{r_brace}<0 1 0>; these slip lines were found near intersections of {l_brace}1 1 0{r_brace}<0 1 0> slip lines, which suggests that the {l_brace}1 0 0{r_brace}<0 1 0> may be a secondary slip system in YAg. Transmission electron microscope (TEM) examination of the crystals was performed after tensile testing and the dislocations observed were analyzed by g {center_dot} b=0 out of contrast analysis. This TEM analysis indicated that the predominant Burgers vector for the dislocations present was <1 1 1> with some <0 1 1> dislocations also being observed. This finding is inconsistent with the <0 1 0> slip direction determined by slip line analysis, and possible explanations for this surprising finding are presented.

Russell, A.M.; Zhang, Z.; Lograsso, T.A.; Lo, C.C.H.; Pecharsky, A.O.; Morris, J.R.; Ye, Y.; Gschneidner, K.A.; Slager, A.J

2004-08-02

174

Halide electroadsorption on single crystal surfaces  

SciTech Connect

The structure and phase behavior of halides have been investigated on single crystals of Ag and Au using synchrotron x-ray scattering techniques. The adlayer coverages are potential dependent. For all halides studied the authors found that with increasing potential, at a critical potential, a disordered adlayer transforms into an ordered structure. Often these ordered phases are incommensurate and exhibit potential-dependent lateral separations (electrocompression). The authors have analyzed the electrocompression in terms of a model which includes lateral interactions and partial charge. A continuous compression is not observed for Br on Ag(100). Rather, they find that the adsorption is site-specific (lattice gas) in both the ordered and disordered phases. The coverage increases with increasing potential and at a critical potential the disordered phase transforms to a well-ordered commensurate structure.

Ocko, B.M. [Brookhaven National Lab., Upton, NY (United States). Dept. of Physics; Wandlowski, T. [Univ. of Ulm (Germany). Dept. of Electrochemistry

1997-07-01

175

Stacking faults in fatigued titanium single crystals  

SciTech Connect

It is generally accepted that the mechanical behavior and interior dislocation substructure of metals and alloys are functions of the stacking fault energies (SFEs). The higher the SFE, the more difficult it is to split a dislocation into two partial dislocations separated by a stacking fault. Whereas materials with high SFE allow easy cross-slip of screw dislocations. Titanium is known to have a high SFE. Even though stacking faults in titanium have been observed experimentally, there is still doubt on them due to the high values of SFE. The purpose of the present study is to obtain further information on stacking faults in fatigued titanium single crystals and to discuss the relation between stacking fault and twinning.

Tan Xiaoli; Gu Haicheng [Xi`an Jiaotong Univ. (China). Research Inst. for Strength of Metals

1995-12-15

176

Magnetoplasticity and diffusion in silicon single crystals  

SciTech Connect

The effect of static magnetic fields on the dynamics of surface dislocation segments, as well as the diffusion mobility of a dopant in silicon single crystals, has been analyzed. It has been experimentally found that the preliminary treatment of p-type silicon plates (the dopant is boron with a concentration of 10{sup 16} cm{sup -3}) in the static magnetic field (B = 1 T, a treatment time of 30 min) leads to an increase in the mobility of surface dislocation segments. The characteristic times of observed changes (about 80 h) and the threshold dopant concentration (10{sub 15} cm{sup -3}) below which the magneto-optical effect in silicon is not fixed have been determined. It has been found that diffusion processes in dislocation-free silicon are magnetically sensitive: the phosphorus diffusion depth in p-type silicon that is preliminarily aged in the static magnetic field increases (by approximately 20%) compared to the reference samples.

Skvortsov, A. A., E-mail: SkvortsovAA2009@yandex.ru; Karizin, A. V. [Moscow State Technical University 'MAMI' (Russian Federation)

2012-01-15

177

On single doping and co-doping of spray pyrolysed ZnO films: Structural, electrical and optical characterisation  

Microsoft Academic Search

In this paper we present studies on ZnO thin films (prepared using Chemical Spray pyrolysis (CSP) technique) doped in two different ways; in one set, single doping using indium was done while in the second set, co-doping using indium and fluorine was adopted. In the former case, effect of in-situ as well as ex-situ doping using In was analyzed. Structural

T. V. Vimalkumar; N. Poornima; K. B. Jinesh; C. Sudha Kartha; K. P. Vijayakumar

2011-01-01

178

Synthesis of violet light emitting single crystalline ZnO nanorods by using CTAB-assisted hydrothermal method  

Microsoft Academic Search

ZnO nanorods were grown by cetyl trimethylammonium bromide assisted hydrothermal technique from a single molecular precursor.\\u000a The phase and structural analysis were carried out by X-ray diffraction technique and Raman spectroscopy, respectively. The\\u000a phase and structural analysis has suggested that as prepared nanorods have hexagonal wurzite structure. Morphology of the\\u000a nanorods was investigated by electron microscopy techniques which showed the

Prabhakar Rai; Suraj Kumar Tripathy; Nam-Hee Park; Kwang-Joong O; In-Hwan Lee; Yeon-Tae Yu

2009-01-01

179

Precisely-controlled fabrication of single ZnO nanoemitter arrays and their possible application in low energy parallel electron beam exposure  

NASA Astrophysics Data System (ADS)

Precisely-controlled fabrication of single ZnO nanoemitter arrays and their possible application in low energy parallel electron beam exposure are reported. A well defined polymethyl methacrylate (PMMA) nanohole template was employed for local solution-phase growth of single ZnO nanoemitter arrays. Chlorine plasma etching for surface smoothing and pulsed-laser illumination in nitrogen for nitrogen doping were performed, which can significantly enhance the electron emission and improve the emitter-to-emitter uniformity in performance. Mechanisms responsible for the field emission enhancing effect are proposed. Low voltage (368 V) e-beam exposure was performed by using a ZnO nanoemitter array and a periodical hole pattern (0.72-1.26 ?m in diameter) was produced on a thin (25 nm) PMMA. The work demonstrates the feasibility of utilizing single ZnO nano-field emitter arrays for low voltage parallel electron beam lithography.

He, H.; She, J. C.; Huang, Y. F.; Deng, S. Z.; Xu, N. S.

2012-03-01

180

Precisely-controlled fabrication of single ZnO nanoemitter arrays and their possible application in low energy parallel electron beam exposure.  

PubMed

Precisely-controlled fabrication of single ZnO nanoemitter arrays and their possible application in low energy parallel electron beam exposure are reported. A well defined polymethyl methacrylate (PMMA) nanohole template was employed for local solution-phase growth of single ZnO nanoemitter arrays. Chlorine plasma etching for surface smoothing and pulsed-laser illumination in nitrogen for nitrogen doping were performed, which can significantly enhance the electron emission and improve the emitter-to-emitter uniformity in performance. Mechanisms responsible for the field emission enhancing effect are proposed. Low voltage (368 V) e-beam exposure was performed by using a ZnO nanoemitter array and a periodical hole pattern (0.72-1.26 ?m in diameter) was produced on a thin (25 nm) PMMA. The work demonstrates the feasibility of utilizing single ZnO nano-field emitter arrays for low voltage parallel electron beam lithography. PMID:22333999

He, H; She, J C; Huang, Y F; Deng, S Z; Xu, N S

2012-02-14

181

Effects of Phonon Coupling and Free Carriers on Band-Edge Emission at Room Temperature in n-type ZnO Crystals.  

National Technical Information Service (NTIS)

Room-temperature photoluminescence has been studied in II-type bulk ZnO crystals representing three different growth methods and having free- carrier concentrations (n) ranging from 10(exp 13) to 10(exp 18) /cu cm. The near-band-edge emission has both fre...

B. Wang C. Xu J. S. Neal M. J. Callahan N. C. Giles

2008-01-01

182

Simulation of rolling behaviour of cubic oriented al single crystal with crystal plasticity FEM  

Microsoft Academic Search

The crystal plasticity finite element method (CPFEM), which incorporates the crystal plasticity constitutive law into the finite element method, has been used to investigate the rolling processes of the cubic oriented Al single crystal. The developed model has been validated by comparison with the experimental observations. The simulation results have shown that after rolling the crystal predominantly rotates around the

L. Y. Si; C. Lu; N. N. Huynh; A. K. Tieu; X. H. Liu

2008-01-01

183

Ultratough CVD single crystal diamond and three dimensional growth thereof  

DOEpatents

The invention relates to a single-crystal diamond grown by microwave plasma chemical vapor deposition that has a toughness of at least about 30 MPa m.sup.1/2. The invention also relates to a method of producing a single-crystal diamond with a toughness of at least about 30 MPa m.sup.1/2. The invention further relates to a process for producing a single crystal CVD diamond in three dimensions on a single crystal diamond substrate.

Hemley, Russell J. (Washington, DC); Mao, Ho-kwang (Washington, DC); Yan, Chih-shiue (Washington, DC)

2009-09-29

184

Synthesis of Nanograined ZnO Nanowires and Their Enhanced Gas Sensing Properties.  

PubMed

Polycrystalline ZnO nanowires with grain sizes ranging from 20 to 100 nm were synthesized using a newly designed two-step process: (first step) synthesis of ZnSe nanowires by vapor transportation of a mixture of ZnSe powders; and (second step) thermal oxidation of the ZnSe nanowires at 650 C. Compared to the single-crystal ZnO nanowire gas sensors and other nanomaterial gas sensors reported previously, the multiple networked nanowire gas sensors fabricated from the nanograined ZnO nanowires showed substantially enhanced electrical responses to NO(2) gas at 300 C. The NO(2) gas sensing properties of the nanograined ZnO nanowires increased dramatically with increasing NO(2) concentration. The multiple-networked nanograined ZnO nanowire sensor showed a response value of 237,263% at 10 ppm NO(2) and 300 C, whereas the single-crystal ZnO nanowire sensors showed a response of only 6.5% under the same conditions. The recovery time of the nanograined ZnO nanowire sensor was much shorter than that of the normal ZnO nanowire sensor over the NO(2) concentration range of 1-10 ppm, even though the response time of the former was somewhat longer than that of the latter. The origin of the enhanced NO(2) gas sensing properties of the nanograined ZnO nanowire sensor is discussed. PMID:22746969

Park, Sunghoon; An, Soyeon; Ko, Hyunsung; Jin, Changhyun; Lee, Chongmu

2012-07-12

185

Strain effects in a single ZnO microwire with wavy configurations.  

PubMed

We investigate strain-induced optical modulation in a ZnO microwire with wavy geometries induced by mechanical strains. Curved sections of the wavy ZnO microwire show red-/blue-shifts of near-band-edge emission and broadening of full width at half maximum in cathodoluminescence spectra along the length of the wavy ZnO microwire, compared with straight sections. The observed variations indicate that local strains in the wavy ZnO microwire lead to strain-dependent local changes of its energy band structure. The local bending curvature calculations using a geometric model also provide correlation between the shift of the near-band-edge emission peaks and the bending strain. PMID:24140605

Park, Jong Bae; Hong, Woong-Ki; Bae, Tae Sung; Sohn, Jung Inn; Cha, Seungnam; Kim, Jong Min; Yoon, Jongwon; Lee, Takhee

2013-10-18

186

Strain effects in a single ZnO microwire with wavy configurations  

NASA Astrophysics Data System (ADS)

We investigate strain-induced optical modulation in a ZnO microwire with wavy geometries induced by mechanical strains. Curved sections of the wavy ZnO microwire show red-/blue-shifts of near-band-edge emission and broadening of full width at half maximum in cathodoluminescence spectra along the length of the wavy ZnO microwire, compared with straight sections. The observed variations indicate that local strains in the wavy ZnO microwire lead to strain-dependent local changes of its energy band structure. The local bending curvature calculations using a geometric model also provide correlation between the shift of the near-band-edge emission peaks and the bending strain.

Park, Jong Bae; Hong, Woong-Ki; Bae, Tae Sung; Inn Sohn, Jung; Cha, SeungNam; Kim, Jong Min; Yoon, Jongwon; Lee, Takhee

2013-11-01

187

Site-selective spectroscopy of Cr3+ in congruent co-doped LiNbO3:Cr3+:ZnO crystals  

Microsoft Academic Search

This work reports the energy levels of chromium ions for different sites in congruent LiNbO3 crystals doped with ZnO. Optical absorption and luminescence (fluorescence and excitation) experimental techniques were used. For crystals with Zn2+ concentration less than 4.7%, optical signals correspond to Cr3+ ions substituting for Li+ ions; for higher Zn2+ concentration, signals show two components coming from different sites

G. A. Torchia; J. O. Tocho; F. Jaque

2000-01-01

188

Investigation on Growth and Surface Analysis of DAST Single Crystals  

SciTech Connect

We have explored the growth of bulk size N, N-dimethylamino-N'-methylstilbazolium p-toluenesulphonate (DAST) using slope nucleation method. The grown crystal was characterized by single crystal X-ray diffraction (XRD), and CHN analyses. The surface morphology of the crystal was analyzed using Scanning electron microscopy (SEM).

Thomas, Tina; Vijay, R. Jerald; Gunaseelan, R.; Sagayaraj, P. [Department of Physics, Loyola College, Chennai - 600 034 (India)

2011-07-15

189

Synthesis of flower-like ZnO nanostructures by an organic-free hydrothermal process  

NASA Astrophysics Data System (ADS)

Flower-like ZnO nanostructures, which consisted of sword-like ZnO nanorods, have been prepared by an organic-free hydrothermal process. The XRD pattern indicated that the flower-like ZnO nanostructures were hexagonal. The SAED and HRTEM experiments implied that the sword-like ZnO nanorods were single crystal in nature and preferentially grew up along the [001] direction. The effects of temperature, pH value and mineralizer on the morphology have been also investigated. It is considered that pH value is the main factor to influence the morphology because of its effect on the initial nuclei and growth environment of ZnO. Finally, the mechanism for organic-free hydrothermal synthesis of the flower-like ZnO nanostructure is discussed.

Zhang, Hui; Yang, Deren; Ma, Xiangyang; Ji, Yujie; Xu, Jin; Que, Duanlin

2004-05-01

190

Fabrication of polypyrrole nano-arrays in lysozyme single crystals  

NASA Astrophysics Data System (ADS)

A template-directed method for the synthesis and organization of partially oxidized polypyrrole (PPy) nanoscale arrays within the solvent channels of glutaraldehyde-cross-linked lysozyme single crystals is presented. Macroscopic single crystals of the periodically arranged protein-polymer superstructure are electrically conductive, insoluble in water and organic solvents, and display increased levels of mechanical plasticity compared with native cross-linked lysozyme crystals.A template-directed method for the synthesis and organization of partially oxidized polypyrrole (PPy) nanoscale arrays within the solvent channels of glutaraldehyde-cross-linked lysozyme single crystals is presented. Macroscopic single crystals of the periodically arranged protein-polymer superstructure are electrically conductive, insoluble in water and organic solvents, and display increased levels of mechanical plasticity compared with native cross-linked lysozyme crystals. Electronic supplementary information (ESI) available: Optical microscopy, SEM, TEM images, FTIR spectra and tables, conductivity plot. Experimental methods. See DOI: 10.1039/c2nr32413j

England, Matt W.; Lambert, Elizabeth M.; Li, Mei; Turyanska, Lyudmila; Patil, Avinash J.; Mann, Stephen

2012-10-01

191

Microscale Laser Peen Forming of Single Crystal  

SciTech Connect

As the result of quickly increased requirement in many industrial products resulting from microtechnology, laser thermal microforming and microsurface treatment [microscale laser shock peening (?LSP)] have been well studied. By combining the beneficial effects of these two processes with a controlled bending deformation, microscale laser peen forming (?LPF) attracts more attention recently since it not only improves the fatigue life of the material but also shapes microscale metallic parts at the same time. In the present study, ?LSP of single crystal aluminum was presented to study anisotropic material response. Local plastic deformation was characterized by lattice rotation measured through electron backscatter diffraction. Residual stress distributions of both sides of a peened sample, characterized by x-ray microdiffraction, were compared with the results obtained from finite element method simulation. ?LPF anisotropic behavior was investigated in three effective slip systems via both the anisotropic slip line theory and numerical method. Also, the work hardening effect resulted from self-hardening, and latent hardening was analyzed through comparing the results with and without considering hardening.

Wang,Y.; Fan, Y.; Kysar, J.; Vukelic, S.; Yao, Y.

2008-01-01

192

Bonding techniques for single crystal TFT AMLCDs  

NASA Astrophysics Data System (ADS)

Transmissive single crystal AMLCD light valves have recently drawn much attention for application in flat panel displays. The active matrix circuits are fabricated on SIMOX wafers and then transferred to glass. Circuit transfer consists in bonding a CMOS processed SIMOX wafer to a Pyrex glass substrate, thinning the SIMOX wafer and opening the contact pads. The pixel electrodes are made in polysilicon to allow standard CMOS processing. This paper discusses the transparency of the poly electrode and evaluates the potential of anodic bonding and adhesive bonding for circuit transfer. A major challenge for anodic bonding is the protection of the device dielectrics against the high voltages applied during bonding. A test chip was designed to investigate different ways of circumventing breakdown of the dielectrics. A method for adhesive bonding is discussed that assures good uniformity of the thickness of the epoxy layer and avoids the inclusion of air bubbles. It is demonstrated that the epoxies are resistant to the chemicals used for thinning the silicon substrate.

van der Groen, Sonja; Rosmeulen, Maarten; Jansen, Philippe; Deferm, Ludo; Baert, Kris

1996-09-01

193

High pressure synthesis of single crystals of ?-boron  

Microsoft Academic Search

A method of synthesis of single crystals of alfa-boron (?-B) is presented. ?-Boron has been crystallized from a boronplatinum melt at high pressures (611GPa) and high temperatures (12001600C). The method is based on the high-pressure large volume (multi-anvil) press technique. An average size of the as-grown isometric crystals is 6080?m in maximum dimension. A refinement of an accurate crystal structure

Gleb Parakhonskiy; Natalia Dubrovinskaia; Leonid Dubrovinsky; Swastik Mondal; Sander van Smaalen

2011-01-01

194

Anisotropy of Laser-Induced Bulk Damage of Single Crystals  

Microsoft Academic Search

The regularities of laser-induced damage of anisotropic materials, such as LiNbO3 and KDP dielectric single crystals, are experimentally studied. It is revealed that the shape of laser-induced damage in the dielectric crystals depends on the elastic symmetry of crystal and the propagation direction of the laser beam. When the beam propagates along the optic axis of crystals, the figures of

O. Krupych; Ya. Dyachok; I. Smaga; R. Vlokh

2007-01-01

195

Single crystal silicon rotary microactuator for hard disk drive  

Microsoft Academic Search

A single crystal silicon rotary microactuator for hard disk drives (HDD) is described in this paper. The microactuator is mounted between the slider and suspension and drives the slider on which a magnetic head element is attached. The microactuator has electrically isolated microstructures with an aspect ratio 20:1 directly processed from a single crystal silicon substrate. It consists of a

J. Q. Mou; Y. Lu; J. P. Yang; Q. H. Li

2003-01-01

196

Chemical Solution Routes to Single-Crystal Thin Films  

Microsoft Academic Search

Epitaxial thin films of inorganic single crystals can be grown on single-crystal substrates with a variety of different solution chemistries. This review emphasizes chemical solution deposition, in which a solution is used to deposit a layer of precursor molecules that decompose to low-density, polycrystalline films during heating. Ways to control film cracking during deposition and heat treatment and why many

F. F. Lange

1996-01-01

197

Investigation of Advanced Processed Single-Crystal Turbine Blade Alloys.  

National Technical Information Service (NTIS)

This investigation studied the influence of thermal processing and microstructure on the mechanical properties of the single-crystal, nickel-based superalloys PWA 1482 and PWA 1484. The objective of the program was to develop an improved single-crystal tu...

B. J. Peters C. M. Biondo D. P. Deluca

1995-01-01

198

Fatigue behavior of a single crystal nickel-base superalloy  

Microsoft Academic Search

Many investigations indicate that high cycle fatigue cracks, in general, initiate at pores, inclusions, and grain boundaries in materials. The fatigue strength limit of a single crystal superalloy increases markedly compared to that of a conventional cast alloy, because the number of pores and inclusions in a single crystal superalloy are less than those of both conventionally cast and directionally

J. H. Zhang; Y. B. Xu; Z. G. Wang; Z. Q. Hu

1995-01-01

199

Semiconductor single crystal external ring resonator cavity laser and gyroscope  

SciTech Connect

A ring laser is described comprising: a semiconductor single crystal external ring resonator cavity having a plurality of reflecting surfaces defined by the planes of the crystal and establishing a closed optical path; and a discrete laser medium disposed in said semiconductor single crystal external ring resonator cavity for generating coherent light in said cavity, wherein said resonator cavity is decoupled from the laser medium.

Spitzer, M.P.

1993-08-31

200

Fatigue behavior of a single crystal nickel-base superalloy  

SciTech Connect

Many investigations indicate that high cycle fatigue cracks, in general, initiate at pores, inclusions, and grain boundaries in materials. The fatigue strength limit of a single crystal superalloy increases markedly compared to that of a conventional cast alloy, because the number of pores and inclusions in a single crystal superalloy are less than those of both conventionally cast and directionally solidified superalloys. Also, grain boundaries are eliminated in the single crystal superalloy. The fatigue fracture of a single crystal superalloy usually appears to be brittle. Therefore, it is necessary to study the micro-fracture mechanism. This paper presents an investigation of the fracture characteristics and micro-mechanism of fracture in a single crystal superalloy during high cycle fatigue.

Zhang, J.H.; Xu, Y.B.; Wang, Z.G.; Hu, Z.Q. [Academy of Sciences, Shenyang (China). State Key Lab. for Fatigue and Fracture of Materials

1995-06-15

201

Influence of electron irradiation on hydrothermally grown zinc oxide single crystals  

NASA Astrophysics Data System (ADS)

The resistivity of hydrothermally grown ZnO single crystals increased from ~103 ? cm to ~106 ? cm after 1.8 MeV electron irradiation with a fluence of ~1016 cm-2, and to ~109 ? cm as the fluence increased to ~1018 cm-2. Defects in samples were studied by thermally stimulated current (TSC) spectroscopy and positron lifetime spectroscopy (PLS). After the electron irradiation with a fluence of 1018 cm-2, the normalized TSC signal increased by a factor of ~100. A Zn vacancy was also introduced by the electron irradiation, though with a concentration lower than expected. After annealing in air at 400 C, the resistivity and the deep traps concentrations recovered to the levels of the as-grown sample, and the Zn vacancy was removed.

Lu, L. W.; So, C. K.; Zhu, C. Y.; Gu, Q. L.; Li, C. J.; Fung, S.; Brauer, G.; Anwand, W.; Skorupa, W.; Ling, C. C.

2008-09-01

202

Reshock and release response of aluminum single crystal  

SciTech Connect

Reshock and release experiments were performed on single crystal aluminum along three orientations and on polycrystalline 1050 aluminum with 50 {mu}m grain size at shock stresses of 13 and 21 GPa to investigate the mechanisms for previously observed quasielastic recompression behavior. Particle velocity profiles obtained during reshocking both single crystals and polycrystalline aluminum from initial shock stresses of 13-21 GPa show similar quasielastic recompression behavior. Quasielastic release response is also observed in all single crystals, but the magnitude of the effect is crystal orientation dependent, with [111] and [110] exhibiting more ideal elastic-plastic release for unloading from the shocked state than for the [100] orientation and polycrystalline aluminum. The quasielastic response of 1050 aluminum is intermediate to that of the [100] and [111] orientations. Comparison of the wave profiles obtained for both unloading and reloading of single crystals and polycrystalline 1050 aluminum from shocked states suggests that the observed quasielastic response of polycrystalline aluminum results from the averaging response of single crystals for shock propagation along different orientations, and that the response of 1050 aluminum with large grain boundaries is not significantly different from the results obtained on single crystal aluminum. The yield strength of the single crystals and 1050 aluminum is found to increase with shock stress, which is consistent with previous results [H. Huang and I. R. Asay, J. Appl. Phys. 98, 033524 (2005)].

Huang, H.; Asay, J. R. [Institute for Shock Physics and Department of Physics, Washington State University, Pullman, Washington 99164-2816 (United States)

2007-03-15

203

Fabrication and characterization of an individual ZnO microwire-based UV photodetector  

Microsoft Academic Search

In this paper, a single ZnO microwire-based photodetector for the monitoring of ultraviolet (UV) radiation is described. Single crystal ZnO microwires were synthesized using a chemical vapor deposition (CVD) on the Si or Al2O3 substrate. The UV photodetector was fabricated by using in-situ lift-out method in a focused ion beam system to manipulate individual zinc oxide microwire. The photodetector prototype

G. Y. Chai; L. Chow; O. Lupan; E. Rusu; G. I. Stratan; H. Heinrich; V. V. Ursaki; I. M. Tiginyanu

2011-01-01

204

Single crystal to single crystal transformation and hydrogen-atom transfer upon oxidation of a cerium coordination compound.  

PubMed

Trivalent and tetravalent cerium compounds of the octamethyltetraazaannulene (H2omtaa) ligand have been synthesized. Electrochemical analysis shows a strong thermodynamic preference for the formal cerium(IV) oxidation state. Oxidation of the cerium(III) congener Ce(Homtaa)(omtaa) occurs by hydrogen-atom transfer that includes a single crystal to single crystal transformation upon exposure to an ambient atmosphere. PMID:23534677

Williams, Ursula J; Mahoney, Brian D; Lewis, Andrew J; DeGregorio, Patrick T; Carroll, Patrick J; Schelter, Eric J

2013-03-27

205

Single ZnO Microrod Ultraviolet Photodetector with High Photocurrent Gain.  

PubMed

An Ag/ZnO microrod/Ag ultraviolet photodetector is fabricated, the ZnO microrod shows a hexagonal whispering gallery cavity structure. Upon a 325 nm ultraviolet illumination, the device shows a high sensitivity of 4 10(4) A/W and a high photocurrent gain of 1.5 10(5) at 5 V bias. Under different illumination power P, the photocurrent Ilight obeys a power law relation Ilight ? P(0.69). The high performance is probably attributed to a Schottky barrier at Ag/ZnO interface and optical whispering gallery mode effect in the ZnO microrod. PMID:24063658

Dai, Jun; Xu, Chunxiang; Xu, Xiaoyong; Guo, Jiyuan; Li, Jitao; Zhu, Gangyi; Lin, Yi

2013-09-26

206

Method for harvesting single crystals from a peritectic melt  

DOEpatents

A method of preparing single crystals is disclosed. The method of preparation involves preparing precursor materials of a particular composition, heating the precursor material to achieve a peritectic mixture of peritectic liquid and crystals, cooling the peritectic mixture to quench directly the mixture on a porous, wettable inert substrate to wick off the peritectic liquid, leaving single crystals on the porous substrate. Alternatively, the peritectic mixture can be cooled to a solid mass and reheated on a porous, inert substrate to melt the matrix of peritectic fluid while leaving the crystals unmelted, allowing the wicking away of the peritectic liquid. 2 figs.

Todt, V.R.; Sengupta, S.; Shi, D.

1996-08-27

207

Method for harvesting rare earth barium copper oxide single crystals  

DOEpatents

A method of preparing high temperature superconductor single crystals. The method of preparation involves preparing precursor materials of a particular composition, heating the precursor material to achieve a peritectic mixture of peritectic liquid and crystals of the high temperature superconductor, cooling the peritectic mixture to quench directly the mixture on a porous, wettable inert substrate to wick off the peritectic liquid, leaving single crystals of the high temperature superconductor on the porous substrate. Alternatively, the peritectic mixture can be cooled to a solid mass and reheated on a porous, inert substrate to melt the matrix of peritectic fluid while leaving the crystals melted, allowing the wicking away of the peritectic liquid.

Todt, Volker R. (Lemont, IL); Sengupta, Suvankar (Columbus, OH); Shi, Donglu (Cincinnati, OH)

1996-01-01

208

Method for harvesting single crystals from a peritectic melt  

DOEpatents

A method of preparing single crystals. The method of preparation involves preparing precursor materials of a particular composition, heating the precursor material to achieve a peritectic mixture of peritectic liquid and crystals, cooling the peritectic mixture to quench directly the mixture on a porous, wettable inert substrate to wick off the peritectic liquid, leaving single crystals on the porous substrate. Alternatively, the peritectic mixture can be cooled to a solid mass and reheated on a porous, inert substrate to melt the matrix of peritectic fluid while leaving the crystals unmelted, allowing the wicking away of the peritectic liquid.

Todt, Volker R. (Lemont, IL); Sengupta, Suvankar (Columbus, OH); Shi, Donglu (Cincinnati, OH)

1996-01-01

209

Magnetic resonance experiments on the green emission in undoped ZnO crystals  

NASA Astrophysics Data System (ADS)

Optically detected magnetic resonance shows that a broad, green emission band in ZnO at 2.45eV originates from a spintriplet-recombination characterised by g||c=1.984 and g?c=2.025 (parallel and perpendicular to the crystallographic c-axis, respectively) and a zero-field splitting of /D=26010-4cm-1. These parameters and the polarisation properties of the emission are very similar to the anion vacancies in CaO but not compatible with the Zeeman results on ZnO:Cu.

Leiter, F.; Zhou, H.; Henecker, F.; Hofstaetter, A.; Hofmann, D. M.; Meyer, B. K.

2001-12-01

210

Controllable synthesis and characterization of hollow-opened ZnO/Zn and solid Zn/ZnO single crystal microspheres  

NASA Astrophysics Data System (ADS)

We report the growth and structural properties of hollow-opened ZnO/Zn and solid Zn/ZnO single crystal microspheres on a silicon (111) substrate. The microspheres were synthesized from ZnO mixed with Zn by chemical vapour deposition. The ZnO/Zn microspheres exhibit a hollow interior and a spherical shell with a partly opened mouth along the c-axis of the hexagonal wurtzite ZnO structure oriented vertically to the substrate. The Zn/ZnO microspheres are solid. The microsphere growth process includes the deposition of Zn and ZnO particles followed by the evaporation of Zn from the breaking shell of the ZnO microparticles. The break in the shell is caused by the evaporation of Zn. The morphologies, chemical composition and crystal structure of the microspheres were characterized using x-ray diffraction, energy dispersive x-ray spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy and high-resolution transmission electron microscopy. The room-temperature photoluminescence spectra were investigated using a 325 nm He Cd laser as the excitation source.

Mahir Sulieman, Kamal; Huang, Xintang; Liu, Jinping; Tang, Ming

2006-10-01

211

The Growth of Large Single Crystals.  

ERIC Educational Resources Information Center

Presented is an experiment which demonstrates principles of experimental design, solubility, and crystal growth and structure. Materials, procedures and results are discussed. Suggestions for adapting this activity to the high school laboratory are provided. (CW)

Baer, Carl D.

1990-01-01

212

Epitaxial electrodeposition of freestanding large area single crystal substrates  

SciTech Connect

The authors report on a method for producing freestanding single crystal metal films over large areas using electrodeposition and selective etching. The method can be turned into an inexpensive continuous process for making long ribbons or a large area of single crystal films. Results from a 5x5 mm{sup 2} Ni single crystal film using electron backscattering pattern pole figures and x-ray diffraction demonstrate that the quality of material produced is equivalent to the initial substrate without annealing or polishing.

Shin, Jae Wook; Standley, Adam; Chason, Eric [Brown University, Box D, Providence, Rhode Island 02912 (United States)

2007-06-25

213

Spherical Nb single crystals containerlessly grown by electrostatic levitation  

NASA Astrophysics Data System (ADS)

Spherical Nb (Tm=2750 K) single crystals were grown via containerless electrostatic levitation (ESL). Samples became spherical at melting in levitation and undercooled typically 300-450 K prior to nucleation. As-processed samples were still spherical without any macroscopic shape change by solidification showing a uniform dendritic surface morphology. Crystallographic {111} planes exposed in equilateral triangular shapes on the surface by preferential macroetching and spotty back-reflection Laue patterns confirm the single crystal nature of the ESL-processed Nb samples. No hysteresis in magnetization between zero field and field cooling also implies a clean defect-free condition of the spherical Nb single crystals.

Sung, Y. S.; Takeya, H.; Hirata, K.; Togano, K.

2003-05-01

214

New rubidium zinc hydrogen phosphate, Rb2Zn2(HPO4)3: synthesis, crystal structure, and 31P single-crystal NMR.  

PubMed

A new rubidium zinc hydrogen phosphate, Rb2Zn2(HPO4)3, is prepared by an unusual method utilizing long nucleation times. This material is crystallized from a gel with an initial composition of 1.0 ZnO/0.94 P2O5/0.96 Rb2O/0.04 Li2O/41 H2O, while the phosphate concentration equals 1.6 M and pH = 3.5. The gel is placed in a sealed Pyrex flask at 52 degrees C, and after 4.5 months crystallization of Rb2Zn2(HPO4)3 is noticed. This new crystalline compound has a three-dimensional framework structure built from spiral chains of alternating PO4 and ZnO4 tetrahedra connected pairwise and assembled by other PO4 tetrahedra, rubidium ions, and hydrogen bonds. The two rubidium ions, Rb(1) and Rb(2), have an exceptionally low number of oxygen contacts in the first coordination sphere, five and seven, respectively. Crystal data: monoclinic, P2(1)/c (no. 14), a = 12.5880(4), b = 12.7170(8), c = 7.5827(8) A, beta = 96.100(1) degrees, Z = 4. A single-crystal 31P NMR investigation of Rb2Zn2(HPO4)3 was performed employing a two-axis goniometer probe and reveals the presence of three chemically and six magnetically nonequivalent phosphorus sites, in accordance with the crystal structure. 31P chemical shielding anisotropies and isotropic chemical shifts (-3.3(3), -2.6(3), and 2.0(3) ppm) have been determined for the three phosphorus sites. PMID:12526508

Jensen, T R; Hazell, R G; Vosegaard, T; Jakobsen, H J

2000-05-15

215

Single crystal Processing and magnetic properties of gadolinium nickel  

SciTech Connect

GdNi is a rare earth intermetallic material that exhibits very interesting magnetic properties. Spontaneous magnetostriction occurs in GdNi at T{sub C}, on the order of 8000ppm strain along the c-axis and only until very recently the mechanism causing this giant magnetostriction was not understood. In order to learn more about the electronic and magnetic structure of GdNi, single crystals are required for anisotropic magnetic property measurements. Single crystal processing is quite challenging for GdNi though since the rare-earth transition-metal composition yields a very reactive intermetallic compound. Many crystal growth methods are pursued in this study including crucible free methods, precipitation growths, and specially developed Bridgman crucibles. A plasma-sprayed Gd{sub 2}O{sub 3} W-backed Bridgman crucible was found to be the best means of GdNi single crystal processing. With a source of high-quality single crystals, many magnetization measurements were collected to reveal the magnetic structure of GdNi. Heat capacity and the magnetocaloric effect are also measured on a single crystal sample. The result is a thorough report on high quality single crystal processing and the magnetic properties of GdNi.

Shreve, Andrew John [Ames Laboratory

2012-11-02

216

Pulse shape discrimination with new single crystal organic scintillators  

NASA Astrophysics Data System (ADS)

Pulse shape discrimination in organic single crystal and liquid scintillators provides a means of identifying fission energy neutrons with high specificity. We present the results of a broad survey of over one hundred single crystal organic scintillators produced from low-temperature solution growth technique. Each crystal was evaluated for light yield and pulse shape discrimination performance. The pulse shape dependence on excitations via a Compton electron from a gamma and a recoil proton from a fast neutron was measured using full waveform digitization. Several groups of compounds were compared in relation to molecular and crystallographic structures, crystal perfection, and the effect of impurities. New prospective materials offering neutron/gamma discrimination comparable or superior to stilbene will be presented. We also report on the growth of large single crystal lithium salicylate and other promising Li compounds which have sensitivity to lower energy neutrons via neutron capture on ^6Li and are separable from other excitations via pulse shape discrimination.

Newby, Jason; Zaitseva, Natalia; Payne, Stephen; Cherepy, Nerine; Carman, Leslie; Hull, Giulia

2009-10-01

217

Growing intermetallic single crystals using in situ decanting  

SciTech Connect

High temperature metallic solution growth is one of the most successful and versatile methods for single crystal growth, and is particularly suited for exploratory synthesis. The method commonly utilizes a centrifuge at room temperature and is very successful for the synthesis of single crystal phases that can be decanted from the liquid below the melting point of the silica ampoule. In this paper, we demonstrate the extension of this method that enables single crystal growth and flux decanting inside the furnace at temperatures above 1200C. This not only extends the number of available metallic solvents that can be used in exploratory crystal growth but also can be particularly well suited for crystals that have a rather narrow exposed solidification surface in the equilibrium alloy phase diagram.

Petrovic, Cedomir; Canfield, Paul; Mellen, Jonathan

2012-05-16

218

A new route to grow single-crystal group III-V compound semiconductor nanostructures on non-single-crystal substrates  

Microsoft Academic Search

A new route to grow single-crystal semiconductor nanostructures is reviewed. Unlike conventional epitaxial growth of single-crystal semiconductor films, the proposed route for growing semiconductor nanostructures does not require a single-crystal semiconductor substrate. In the proposed route, instead of using single-crystal semiconductor substrates that are characterized by their long-range atomic order, a non-single-crystal template layer that possesses short-range atomic order prepared

Nobuhiko P. Kobayashi

2007-01-01

219

EPR and Optical Absorption Studies of ?-irradiated Pyrene Single Crystals  

Microsoft Academic Search

Pyrene single crystals irradiated with ? rays at room temperature have been investigated by electron paramagnetic resonance and optical absorption experiments. EPR spectra exhibit a triplet characteristic and each line of the triplet shows characteristic features with rotations of the crystals in a magnetic field. From analyses of these spectra the presence of two kinds of hydrogen added pyrene radicals,

Tetsuya Kawakubo

1978-01-01

220

Dislocation Line Direction Determination in Pyrene Single Crystals  

Microsoft Academic Search

A new technique for the unambiguous determination of dislocation line directions in macroscopic single crystals is presented. The technique is based on analysis of the projected directions of the images of the dislocations on synchrotron white beam topographs. Calculation is carried out in a pseudo-cubic axis system which is related to the crystal axis system by a transformation matrix. Final

Ding Yuan; Michael Dudley

1992-01-01

221

Epitaxial Liftoff for Fully Single-Crystal Ferroelectric Thin Films.  

National Technical Information Service (NTIS)

During the period covered by this report we initiated the application of crystal ion slicing to single crystal potassium tantalate and strontium titanate. Transport of ions in matter (TRIM) simulations and ion implantation at 3.8MeV and various dosages we...

R. M. Osgood M. Levy

1999-01-01

222

Hertzian Fracture in Single Crystals with the Diamond Structure  

Microsoft Academic Search

Extension of an earlier theory of Hertzian fracture in brittle isotropic materials is here made to include the case of brittle single crystals, with particular reference to crystals having the diamond structure. A detailed description is first given of the inhomogeneous stress field in a flat, elastic specimen loaded normally with a hard sphere. The geometry of cracks growing in

B. R. Lawn

1968-01-01

223

Single crystal orientation effects in shock initiation of PETN explosive  

SciTech Connect

Over the past nine years in Los Alamos we have studied shock initiation of detonation in single crystals of PETN explosive. We have demonstrated the effects of point defects and crystal orientation on shock sensitivity. Here we report recent work on orientation effects and anomalous detonation in <110> orientation at 4 GPa. 5 refs.

Dick, J.J.

1988-01-01

224

Study of Single Crystals of Metal Solid Solutions.  

National Technical Information Service (NTIS)

The parameters and requirements for growing single crystals of relatively high melting point metals in a zero gravity environment are studied. The crystal growth of metals such as silver, copper, gold, and alloys with a melting point between 900-1100 C is...

J. A. Reising J. P. Doty

1973-01-01

225

Desorption of Oxygen from Virgin CDS Single Crystals.  

National Technical Information Service (NTIS)

Typical desorption data of amu 16 from virgin CdS single crystals is presented for two classes of crystals as determined by their electrical properties. Thermal desorption energies are found in the energy range of 0.87 eV to > with temperatures of maximum...

K. W. Boer R. Schubert C. Wright

1968-01-01

226

Angular Variation of Coercivity in Orthoferrite Single Crystals.  

National Technical Information Service (NTIS)

The coercive force Hc as a function of the angle between the easy axis of magnetization and the external field was studied in orthoferrite single crystals using the vibrating sample technique. (Author)

S. Reich S. Shtrikman D. Treves

1964-01-01

227

Anthracene Fluorescence at Low Temperatures. II. Doped Single Crystals.  

National Technical Information Service (NTIS)

By the addition of dopants to single crystal anthracene it is shown that many of the fluorescence bands additional to exciton emission are due to traces of 2-methylanthracene. Other impurity bands, apparently arising from locally disorientated host molecu...

L. E. Lyons L. J. Warren

1972-01-01

228

Constitutive Modeling of Superalloy Single Crystals with Verification Testing.  

National Technical Information Service (NTIS)

The goal is the development of constitutive equations to describe the elevated temperature stress-strain behavior of single crystal turbine blade alloys. The program includes both the development of a suitable model and verification of the model through e...

E. Jordan K. P. Walker

1985-01-01

229

Planning Study for Preparation of Single Crystal Experiments.  

National Technical Information Service (NTIS)

In order to conceive suitable space experiments with single crystals their properties desired for technical applications must first be considered. By comparing the production possibilities, including their limitations in space and on earth, it is possible...

H. Weiss

1976-01-01

230

Toward, single molecule detection with photonic crystal microcavity biosensors  

Microsoft Academic Search

Time resolved biomolecular binding events were measured using photonic crystal microcavity resonators integrated with microfluidics. The optical field is confined to a volume of 33 times 10-18 liters, which enables monitoring of single binding events

L. W. Mirkarimi; S. Zlatanovic; S. Sigalas; M. A. Bynum; K. Robotti; E. Chow; A. Grot

2006-01-01

231

Aluminium segregation of TiAl during single crystal growth  

SciTech Connect

{gamma}-TiAl single crystals have been successfully prepared by an induction-heated cold crucible Czochralski technique which offers more flexibility than vertical float zoning. Compositional analysis of the Czochralski grown single crystals indicates a homogeneous composition after initial transition; and the average composition is close to the peritectic composition. However, {gamma}-TiAl single crystals prepared by vertical float zoning show a small aluminium segregation profile along the growth direction; and the average composition of the as-grown crystals is close to that of the starting alloy. Compositional analysis further demonstrated the banded structure with alternative single {gamma}-phase and {alpha}{sub 2} + {gamma} lamellar regions in the vertical float zoned Ti-54 at.% Al.

Bi, Y.J.; Abell, J.S. [Univ. of Birmingham (United Kingdom). School of Metallurgy and Materials

1997-09-15

232

Investigations into the impact of various substrates and ZnO ultra thin seed layers prepared by atomic layer deposition on growth of ZnO nanowire array.  

PubMed

The impact of various substrates and zinc oxide (ZnO) ultra thin seed layers prepared by atomic layer deposition on the geometric morphology of subsequent ZnO nanowire arrays (NWs) fabricated by the hydrothermal method was investigated. The investigated substrates included B-doped ZnO films, indium tin oxide films, single crystal silicon (111), and glass sheets. Scanning electron microscopy and X-ray diffraction measurements revealed that the geometry and aligment of the NWs were controlled by surface topography of the substrates and thickness of the ZnO seed layers, respectively. According to atomic force microscopy data, we suggest that the substrate, fluctuate amplitude and fluctuate frequency of roughness on ZnO seed layers have a great impact on the alignment of the resulting NWs, whereas the influence of the seed layers' texture was negligible. PMID:22759838

Ding, Jn; Liu, Yb; Tan, Cb; Yuan, Ny

2012-07-03

233

Single-crystal piezoceramic actuation for dynamic stall suppression  

Microsoft Academic Search

PZN-8%PT?111? a new single-crystal piezoceramic is explored for its potential to torsionally actuate the existing structure utilizing the induced shear mechanism of piezoceramics. A model of the elastic rotor blade and piezoceramic actuator is developed using the Hamiltons principle and the resulting equations are solved using the finite element method. Numerical results show that the single crystal material is able

D. Thakkar; R. Ganguli

2006-01-01

234

Electron Spin Resonance in an Irradiated Single Crystal of Dimethylglyoxime  

Microsoft Academic Search

The paramagnetic resonance of gamma-irradiated single crystals of dimethylglyoxime has been measured at 23 kMc\\/sec and 9 kMc\\/sec for various orientations of the crystal in the magnetic field. The resonance pattern was found to have a triplet structure caused by coupling to a single N14 nucleus. Both the nuclear coupling and the spectroscopic splitting factor were found to be anisotropic

Ichiro Miyagawa; Walter Gordy

1959-01-01

235

WELDING AND WELD REPAIR OF SINGLE CRYSTAL GAS TURBINE ALLOYS  

Microsoft Academic Search

The cost-effective commercial use of single crystal nickel-based superalloys for land-based turbine engine components such as blades and vanes requires that they can be repair welded to improve as-cast yields or to refurbish worn or failed components after intermediate service intervals. This program addresses this vital need by determining the welding behavior and weldability of single crystal nickel-based superalloys in

J. M. Vitek; S. A. David; S. S. Babu

236

How a silver dendritic mesocrystal converts to a single crystal  

Microsoft Academic Search

In this paper, we demonstrate how a silver dendrite transforms from mesocrystal into single crystal and the stability for a dendritic silver mesocrystal within a Sn\\/AgNO3 galvanic replacement reaction. Our findings provide the direct evidence and visible picture of the transformation from mesocrystal to single crystalline structure and further confirm the particle-mediated crystallization mechanism. At the initial stage of the

Jixiang Fang; Bingjun Ding; Xiaoping Song; Yong Han

2008-01-01

237

Gradient-dependent deformation of two-phase single crystals  

Microsoft Academic Search

In this work, a gradient- and rate-dependent crystallographic formulation is proposed to investigate the macroscopic behaviour of two-phase single crystals. The slip-system-based constitutive formulation relies on strain-gradient concepts to account for the additional strengthening mechanism associated with the deformation gradients within a single crystal with a high volume fraction of dispersed inclusions. The resulting total slip resistance in each active

E. P. Busso; F. T. Meissonnier; N. P. O'Dowd

2000-01-01

238

Synthesis and Single-Crystal Growth of Ca  

SciTech Connect

For the study of the quasi-two-dimensional Mott transition system Ca{sub 2-x}Sr{sub x}RuO{sub 4}, we have succeeded in synthesizing polycrystalline samples and also growing single crystals by a floating-zone method. Details of the preparations for the entire solution range are described. The structural, transport, and magnetic properties of both polycrystalline and single-crystal samples are fully in agreement.

Nakatsuji, Satoru; Maeno, Yoshiteru

2001-01-01

239

Bithermal fatigue of a nickel-base superalloy single crystal  

Microsoft Academic Search

The thermomechanical fatigue behavior of a nickel-base superalloy single crystal was investigated using a bithermal test technique. The bithermal fatigue test was used as a simple alternative to the more complex thermomechanical fatigue test. Both in-phase and out-of-phase bithermal tests were performed on (100)-oriented coated and bare Rene N4 single crystals. In out-of-plane bithermal tests, the tensile and compressive halves

Verrilli

1988-01-01

240

Evaluation of zinc self-diffusion at the interface between homoepitaxial ZnO thin films and (0001) ZnO substrates  

NASA Astrophysics Data System (ADS)

Isotopic ZnO thin films were deposited on the c-plane of ZnO single crystals by pulsed laser deposition. The isotopic abundance of Zn in the films was determined with a secondary ion mass spectrometry before and after the films was diffusion annealed. The diffusion profiles across the film/substrate interface behaved smooth features. The zinc diffusion coefficient (DZn) was obtained by analyzing the slope of the profile in the annealed sample. The temperature dependence of DZn was determined to be DZn(cm2/s)=8.0104exp(-417[kJ/mol])/RT, where R and T are gas constant and temperature. The zinc ion diffusion coefficients were of the same order as that in a ZnO single crystal. A comparison of the experimental and theoretical values indicated that the zinc ions diffused in the thin film and the single crystal through a vacancy mechanism.

Watanabe, Ken; Matsumoto, Kenji; Adachi, Yutaka; Ohgaki, Takeshi; Nakagawa, Tsubasa; Ohashi, Naoki; Haneda, Hajime; Sakaguchi, Isao

2012-10-01

241

Single Crystal Growth of Photorefractive Sillenites.  

National Technical Information Service (NTIS)

The compounds, crystallized in the cubic form similar to sillenite structure, occur in a number of isomorphs. The well-known representatives of this family are bismuth germanium (BGO) and bismuth silicon oxides (BSo), both of which can be grown from their...

V. V. Volkov Y. F. Kargin V. M. Skorikov

1992-01-01

242

Single-helix crystal in atactic polypropylene  

NASA Astrophysics Data System (ADS)

The conformational arrangement of a locally stereoregular sequence of atactic polypropylene (aPP) was investigated via X-ray diffraction, thermal analysis, and infrared spectroscopy. Since the aPP used was an isotactic-rich sample, the X-ray diffraction pattern showed the typical profile of an ?-iPP (isotactic polypropylene) crystal, indicating that the crystal is constructed from locally stereoregular sequences. Even for a sample with low stereoregularity (meso pentad = 16%), small peaks due to ?-iPP crystals were observed. The melting temperature of aPP was reduced compared with an ?-iPP crystal. This corresponds to a shortening of the lamellar thickness. Helical units from chloroform insoluble and soluble fractions having meso pentads of 0.64 and 0.16, respectively, were composed of 3.5 and 1.2 repeating units, respectively. Such short conformational order was also confirmed by infrared spectroscopy. In general, a conformationally sensitive band is observed over a critical regular sequence (n). For the chloroform soluble fraction, a 977 cm-1 band for n = 5 was observed, but the typical 998 and 841 cm-1 bands for n = 11-12 and 13-15, respectively, were not observed. This signals that the regular conformation consists of 1-2 repeating units. It is concluded that a short conformational order (about 1-2 helical units) can construct the crystalline unit for aPP.

Nakaoki, Takahiko; Fukui, Daisuke

2013-11-01

243

Single Crystal Growth by Laser CVD.  

National Technical Information Service (NTIS)

CO2 gas lasers prove to be a superb heat source for use in various applications. Using the lasers, thin monocrystals with a diameter of less than 1 mm were grown. The processes are discussed for creation of the crystals, including a report on related work...

S. Hayashi

1988-01-01

244

Effect of Stress on CDS Single Crystals.  

National Technical Information Service (NTIS)

The electrical and luminescence properties of CdS crystals, which show the phenomenon of storage, were studied as a function of hydrostatic pressure and uniazial stress. In the excited state, uniaxial stress applied parallel to the c axis resulted in an i...

B. A. Kulp K. A. Gale

1966-01-01

245

Single crystals of single-walled carbon nanotubes formed by self-assembly.  

PubMed

We report the self-assembly of single crystals of single-walled carbon nanotubes (SWCNTs) using thermolysis of nano-patterned precursors. The synthesis of these perfectly ordered, single crystals of SWCNTs results in extended structures with dimension on the micrometer scale. Each crystal is composed of an ordered array of tubes with identical diameters and chirality, although these properties vary between crystals. The results show that SWCNTs can be produced as a perfect bulk material on the micrometer scale and point toward the synthesis of bulk macroscopic crystalline material. PMID:11292859

Schlittler, R R; Seo, J W; Gimzewski, J K; Durkan, C; Saifullah, M S; Welland, M E

2001-04-05

246

Fe implanted ferromagnetic ZnO  

Microsoft Academic Search

Room-temperature ferromagnetism has been induced within ZnO single crystals by implant-doping with Fe ions.The four samples implanted initially have been analyzed using SQUID (superconducting quantum interference device) magne-tometry. It was found that only two of them, i.e. the HFHT and the LFLT samples exhibit a pronounced hysteresis loop upon magnetization reversal at 5 K and 300 K. As was found

K. Potzger; S. Zhou; H. Reuther; A. Mucklich; F. Eichhorn; N. Schell; W. Skorupa; M. Helm; J. Fassbender; T. Herrmannsdorfer; T. Papageorgiou

2006-01-01

247

SCREAM I: A single mask, single-crystal silicon, reactive ion etching process for microelectromechanical structures  

Microsoft Academic Search

A single-crystal slhcon, high aspect ratlo, low-temperature process sequence for the fabrlcatlon of suspended rmcroelectromechamcal structures (MEMS) usmg a smgle hthography step and reactwe Ion etching (RIE) IS presented The process IS called SCRJZAM I (single-crystal reactwe etchmg and metalhzatmn) SCREAM I IS a bulk mlcromachmmg process that uses RIE of a s~hcon substrate to fabricate suspended movable smgle-crystal s&on

Kevin A. Shaw; Z. Lisa Zhang; Noel C. MacDonald

1994-01-01

248

Growth of Strontium Titanate Single Crystals from Molten Salts  

Microsoft Academic Search

Single crystals of strontium titanate (SrTiO3) were grown by flux method. The best results were obtained with KF-LiF and KF-K2MoO4 flux systems. Reasonably large single crystals were yielded from the solvent of KF-LiF systems and fine small crystals which were colorless, transparent and flawless were obtained from KF-K2MoO4 systems. The experiments were carried out by slow cooling method, temperature of

Tokuko Sugai; Shuzo Hasegawa; Gisaku Ohara

1968-01-01

249

Hydrothermal growth of carbonate-containing hydroxyapatite single crystals  

Microsoft Academic Search

Single crystals of carbonate-containing hydroxyapatite have been grown hydrothermally by gradually heating with a temperature gradient applied to the vessel, using CaHPO4, H2O and carbon dioxide as dry ice. The optimum conditions to obtain large single crystals are: CaHPO4, 10 g\\/l; final temperature gradient, 33.5C\\/cm; heating rate, 0.005C\\/min; and carbon dioxide, 55 g\\/l. The largest crystal obtained was 12 mm

Atsuo Ito; Satoshi Nakamura; Hideki Aoki; Masaru Akao; Kay Teraoka; Sadao Tsutsumi; Kazuo Onuma; Tetsuya Tateishi

1996-01-01

250

Excitonic fine structure and recombination dynamics in single-crystalline ZnO  

Microsoft Academic Search

The optical properties of a high quality bulk ZnO , thermally post treated in a forming gas environment are investigated by temperature dependent continuous wave and time-resolved photoluminescence (PL) measurements. Several bound and free exciton transitions along with their first excited states have been observed at low temperatures, with the main neutral-donor-bound exciton peak at 3.3605eV having a linewidth of

A. Teke; . zgr; S. Dogan; X. Gu; H. Morko; B. Nemeth; J. Nause; H. O. Everitt

2004-01-01

251

Solution Growth of Rubrene Single Crystals Using Various Organic Solvents  

NASA Astrophysics Data System (ADS)

To fabricate organic field-effect transistors (OFETs) with high carrier mobility, we attempted to grow 5,6,11,12-tetraphenylnaphthacene (rubrene) single crystals from solution and to improve their quality. Investigations into solvents in which rubrene was highly soluble proved that its solubility depended on the presence or absence of aromatic rings and chloro groups rather than on the polarity of the solvents. Rubrene crystals were grown from aromatic solvents, specifically from toluene, p-xylene, and aniline solvents, as well as from 1,2-dichloroethane (DCE) solvent. As a result, rubrene single crystals larger than 1 mm were obtained. Powder X-ray diffraction (XRD) analysis showed that the crystals obtained from the p-xylene and toluene solvents were rubrene, and 1H-nuclear magnetic resonance (1H-NMR) measurement proved that the crystals had not incorporated the solvent at the detection level. In addition, atomic force microscopy (AFM) confirmed that the rubrene crystals grown from the p-xylene and aniline solvents had flat faces and that the crystal from the p-xylene solvent had monomolecular steps on parts of the surfaces. Rubrene single crystal OFETs with graphite electrodes and parylene as an insulator showed carrier mobilities of 0.75 cm2 V-1 s-1.

Matsukawa, Takeshi; Takahashi, Yoshinori; Tokiyama, Tsukasa; Sasai, Kenichi; Murai, Yusuke; Hirota, Nobuhiro; Tominari, Yukihiro; Mino, Norihisa; Yoshimura, Masashi; Abe, Masayuki; Takeya, Junichi; Kitaoka, Yasuo; Mori, Yusuke; Morita, Seizo; Sasaki, Takatomo

2008-12-01

252

Polychromatic Microbeam Diffraction Characterization of Individual ZnO Nanostructures  

SciTech Connect

We have used the focused, polychromatic beam available at sector 34 of the APS to characterize the local lattice structure and perfection of several different forms of ZnO meso- and nano-structures. Using Kirkpatrick-Baez mirrors for white-beam focusing, we have developed scanning x-ray techniques capable of mapping the spatially-resolved lattice structure, strain and composition. Off-axis undulator radiation is routinely focused to ~0.5 mm and beams as small as 90 nm have been demonstrated. Laue diffraction patterns are collected using a CCD area detector, and computer analysis provides spatial maps of the crystal phase, grain orientations (texture), and the local strain tensor. We have demonstrated the ability to map the structure of individual meso- and nano-structures using ZnO fabricated in several different shapes: rods, belts and tapered styluses. TEM samples serve as ideal x-ray microdiffraction samples due to the low background signal. Even when mounted on a relatively-thick crystal substrate, full diffraction patterns can be measured from ZnO rods as narrow as 200 nm diameter. We find that all of the ZnO structures have a facetted, hexagonal crystal structure, with the c-axis often along the rod axis. Larger diameter rods are essentially perfect single crystals, wheras thinner rods show a high degree of flexibility and hence large local mosaic spread along the rod axis. For stylus samples, the tapered region where the diameter decreases remains a single crystal.

Budai, John D [ORNL; Yang, Wenge [Carnegie Institution of Washington; Liu, W. [Argonne National Laboratory (ANL); Tischler, Jonathan Zachary [ORNL; Pan, Zhengwei [ORNL; Heo, YW [University of Florida, Gainesville; Norton, David P. [University of Florida; Larson, Ben C [ORNL; Ice, Gene E [ORNL

2006-01-01

253

Elastic Moduli, Pressure Derivatives, and Temperature Derivatives of Single-Crystal Olivine and Single-Crystal Forsterite  

Microsoft Academic Search

Ultrasonic wave velocities in single-crystal forsteritc (F) and single-crystal olivine (0) have been measured as a function of pressure and of temperature near ambient conditions. Shear and longitudinal velocities were measured in eighteen independent modes, so that each of the nine elastic constants could be calculated by at least two independent equations. The adiabatic stiffness constants c{j (in Mb), their

Mineo Kumazawa; Orson L. Anderson

1969-01-01

254

Shock Driven Twinning in Tantalum Single Crystals  

SciTech Connect

Recovery based observations of high pressure material behavior generated under high explosively driven flyer based loading conditions are reported. Two shock pressures, 25, and 55 GPa and four orientations {l_brace}(100), (110), (111), (123){r_brace} were considered. Recovered material was characterized using electron backscatter diffraction along with a limited amount of transmission electron microscopy to assess the occurrence of twinning under each test condition. Material recovered from 25 GPa had a very small fraction of twinning for the (100), (110), and (111) oriented crystals while a more noticeable fraction of the (123) oriented crystal was twinned. Material recovered from 55 GPa showed little twinning for (100) orientation slightly more for the (111) orientation and a large area fraction for the (123) orientation. The EBSD and TEM observations of the underlying deformation substructure are rationalized by comparing with previous static and dynamic results.

McNaney, J M; HSUING, L M; Barton, N R; Kumar, M

2009-07-20

255

Raman spectra of deuteriated taurine single crystals  

NASA Astrophysics Data System (ADS)

The polarized Raman spectra of partially deuteriated taurine [(ND 3+) 0.65(NH 3+) 0.35(CH 2) 2SO 3-] crystals from x( zz) x and x( zy) x scattering geometries of the A g and B g irreducible representations of the factor group C 2h are reported. The temperature-dependent Raman spectra of partially deuteriated taurine do not reveal any evidence of the structural phase transition undergone by normal taurine at about 250 K, but an anomaly observed in the 180 cm -1 band at 120 K implies a different dynamic for this band (which is involved in a pressure-induced phase transition) in the deuteriated crystal.

Souza, J. M. de; Lima, R. J. C.; Freire, P. T. C.; Sasaki, J. M.; Melo, F. E. A.; Filho, J. Mendes; Jones, Derry W.

2005-05-01

256

Photorefractive Properties of Stoichiometric Lithium Niobate Single Crystals  

SciTech Connect

The specific features of photorefractive light scattering in nominally pure stoichiometric (Li/Nb = 1) sin- gle crystals grown from a melt with 58.6 mol % Li{sub 2}O (LiNbO{sub 3}st) and in the stoichiometric single crystals grown from a melt of congruent composition in the presence of K{sub 2}O flux (LiNbO{sub 3}stK{sub 2}O) have been investi- gated. At an excitation power of 30 mW, LiNbO{sub 3}stK{sub 2}O single crystals are found to exhibit a stronger photo- refractive effect than LiNbO{sub 3}st single crystals.

Sidorov, N. V. [Russian Academy of Sciences, Institute of Chemistry and Technology of Rare Earth Elements and Mineral Raw Materials, Kola Scientific Center (Russian Federation); Antonycheva, E. A.; Syui, A. V. [Far Eastern State Transport University (Russian Federation); Palatnikov, M. N., E-mail: palat_mn@chemy.kolasc.net.ru [Russian Academy of Sciences, Institute of Chemistry and Technology of Rare Earth Elements and Mineral Raw Materials, Kola Scientific Center (Russian Federation)

2010-11-15

257

Growth and characterization of pure and doped btzs single crystals  

NASA Astrophysics Data System (ADS)

The growth and characterization of pure and doped BTZS single crystals are discussed. In the present study powder X-Ray diffraction data of the grown crystal were recorded using BRUKER D8 Advance powder crystal X-ray diffractometer with 2.2 KW Cu anode ceramic X-ray tube. The various functional groups present in the grown crystals were identified and confirmed by recording the FTIR spectrum using BRUKER IFS-66V spectrophotometer by KBr Pellet Technique in the region 4000 ?? 400 cm The UV - Vis - NIR optical spectra of the crystals were recorded using the VARIAN CARY 5E model spectrophotometer. The degree of dopant inclusion was estimated by using Atomic Absorption Spectroscopy. The SHG efficiencies of the crystals were studied using Nd:YAG Q - switched laser.

Gunasekaran, Sethu; Venkatesan, Padmapriya

2012-05-01

258

Studies of single crystal organic scintillators for neutron detection  

NASA Astrophysics Data System (ADS)

Organic crystal scintillators have long been used for fission energy neutron detection and identification. The gamma/neutron separation techniques, known collectively as pulse shape discrimination (PSD), are based on the relative increase in delayed florescence for neutron excitations in comparison to that of gammas. We have conducted a broad survey of the PSD properties for over one hundred single crystal scintillators produced from solution growth techniques, including Li compounds which have sensitivity to lower energy neutrons via neutron capture on ^6Li. Crystal growth methods utilizing temperature reduction of super-saturated solutions have allowed us to produce large volume (> 100 cm^3) faceted organic crystal scintillators with neutron/gamma PSD comparable or superior to trans-stilbene for a subset of these materials. These results show good progress in overcoming the scalability issues of crystal scintillators for neutron detection. We present a survey of our recent results including mixed crystals of varying stilbene fraction.

Glenn, Andrew; Zaitseva, Natalia; Carman, Leslie; Payne, Stephen; Faust, Michelle; Cherepy, Nerine; Hamel, Sebastien; Newby, Jason

2010-11-01

259

Preparation of bead metal single crystals by electron beam heating  

SciTech Connect

For the fabrication of small metal bead crystals a gas flame is used to melt a wire forming a liquid droplet which solidifies upon cooling into a single crystal metal bead. Due to oxidation under ambient conditions bead crystals can be formed only from noble metals using this method. Here we describe a method how to fabricate bead crystals from a wide variety of metals and metal alloys (Cu, Mo, Ru, Rh, Pd, Ag, Ta, W, Re, Ir, Pt, Au, PtPd, Pd{sub 80}Pt{sub 20}, PtRh, AuAg, and PtIr) by electron beam heating under vacuum conditions. Narrow x-ray diffraction peaks confirm a high crystal quality of the bead crystals.

Voigtlaender, Bert; Linke, Udo; Stollwerk, H.; Brona, J. [Institut fuer Schichten und Grenzflaechen ISG 3 and cni-Center of Nanoelectronic Systems for Information Technology, Forschungszentrum Juelich, 52425 Juelich (Germany); Institut fuer Schichten und Grenzflaechen ISG 3 and cni-Center of Nanoelectronic Systems for Information Technology, Forschungszentrum Juelich, 52425 Juelich, Germany and Institute of Experimental Physics, University of Wroclaw, pl. Maxa Borna 9, PL 50-204 Wroclaw (Poland)

2005-11-15

260

Crystal growth and characterization of L-histidine hydrochloride monohydrate semiorganic nonlinear optical single crystals  

NASA Astrophysics Data System (ADS)

Nearly perfect single crystals of L-histidine hydrochloride monohydrate have been grown from the solution prepared from the mixture of L-histidine and hydrochloric acid using slow evaporation solution growth technique. Single crystal X-ray diffraction analysis, High resolution X-ray diffraction analysis, fourier transform infrared and FT-Raman analyzes were employed for structural characterization. Linear and nonlinear optical properties have been studied by UV-Vis transmission spectrum and Kurtz Perry technique respectively. The refractive index, redox behavior and hardness of the grown crystal have been found by suitable methods. Thermogravimetric, differential thermal analysis were employed to characterize the as-grown crystals. The second harmonic generation conversion efficiency of the grown crystal and other properties show the suitability of the grown crystal for frequency conversion applications.

Anandan, P.; Jayavel, R.; Saravanan, T.; Parthipan, G.; Vedhi, C.; Mohan Kumar, R.

2012-05-01

261

Effect of crystallization conditions on the shape of polymer single crystals: Experimental and theoretical approaches  

NASA Astrophysics Data System (ADS)

A modified system of Mansfield equations with different step propagation rates to the right and left was applied to describe the shape of solution-grown single crystals of long-chain alkanes with asymmetrically curved faces ?ub;110?ub;. Solution of this system of equations and simulation of the shape of single crystals of polyethylene, ?-polyvinylidene fluoride, and polyethylene oxide shows good agreement with the experimental data. Comparison of the simulated shapes and experimental micrographs makes it possible to determine the ratio of the intensity of secondary nucleation to the average propagation rate of the layer as well as the ratio of the rates of lateral steps to the right and left and to calculate the absolute values of the main crystallization parameters when the growth rates of single crystals in certain directions are known. It is shown that the asymmetry of the step propagation rate to the right and left is significant only for crystallization at very small supercoolings.

Shcherbina, M. A.; Chvalun, S. N.; Ungar, G.

2007-07-01

262

Solution-processed, Self-organized Organic Single Crystal Arrays with Controlled Crystal Orientation.  

PubMed

A facile solution process for the fabrication of organic single crystal semiconductor devices which meets the demand for low-cost and large-area fabrication of high performance electronic devices is demonstrated. In this paper, we develop a bottom-up method which enables direct formation of organic semiconductor single crystals at selected locations with desired orientations. Here oriented growth of one-dimensional organic crystals is achieved by using self-assembly of organic molecules as the driving force to align these crystals in patterned regions. Based upon the self-organized organic single crystals, we fabricate organic field effect transistor arrays which exhibit an average field-effect mobility of 1.1?cm(2)V(-1)s(-1). This method can be carried out under ambient atmosphere at room temperature, thus particularly promising for production of future plastic electronics. PMID:22563523

Kumatani, Akichika; Liu, Chuan; Li, Yun; Darmawan, Peter; Takimiya, Kazuo; Minari, Takeo; Tsukagoshi, Kazuhito

2012-05-03

263

Facile synthesis and ultrahigh ethanol response of hierarchically porous ZnO nanosheets  

Microsoft Academic Search

Zinc oxide (ZnO) nanosheets were successfully synthesized through a facile, economic, and low-temperature hydrothermal process, followed by annealing of the zinc carbonate hydroxide hydrate precursors. The nanosheets are single crystals with hexagonal wurtzite and mesoporous structures. Gas sensors based on these ZnO nanosheets exhibited ultrahigh response, fast responserecovery, and good selectivity and stability to 0.011000ppm (parts per million) ethanol at

Lexi Zhang; Jianghong Zhao; Haiqiang Lu; Li Li; Jianfeng Zheng; Hui Li; Zhenping Zhu

264

Flow modulation epitaxy of ZnO films on sapphire substrates  

Microsoft Academic Search

High-quality c-axis-oriented single crystal ZnO films have been grown successfully on sapphire substrates by the flow modulation epitaxy (FME) method using a commercial organometallic vapor phase epitaxy (OMVPE) reactor. Diethylzinc (DEZn) and nitrous oxide (N2O) were used as reactant gases. The growth of ZnO films has been conducted as a function of growth conditions, including temperature, growth rate and susceptor

He Huang; W. Y. Jiang; S. P. Watkins

2008-01-01

265

Optical Spectroscopy of Single Pentacene Molecules in a Naphthalene Crystal  

Microsoft Academic Search

Dilute mixed molecular crystals of pentacene in naphthalene were prepared by cosublimation of the two compounds. Single pentacene molecules could be detected in the thin platelets by fluorescence excitation spectroscopy. By analyzing the exponential decay of the fluorescence intensity autocorrelation function for a single molecule in the microsecond time regime we could determine the population (k23) and depopulation (k31) rate

Susanne Kummer; Christoph Bruchle; Thomas Basch

1996-01-01

266

Broadband single-polarization guidance in hybrid photonic crystal fibers.  

PubMed

We present hybrid photonic crystal fibers that provide broadband single-polarization guidance based on two different propagation mechanisms, namely, total internal reflection and the photonic bandgap effect. Experimental results demonstrate polarization dependent loss as high as 26.7 dB and the bandwidth of single-polarization behavior over 225 nm. PMID:21263477

Cerqueira S, Arismar; Lona, D G; de Oliveira, I; Hernandez-Figueroa, H E; Fragnito, H L

2011-01-15

267

Organic single crystal transistor characteristics of single-crystal phase pentacene grown by ionic liquid-assisted vacuum deposition  

NASA Astrophysics Data System (ADS)

Organic transistor characteristics of single-crystal phase pentacene were investigated. Ionic liquids (ILs) were used as not only a gate dielectric material in the transistors but also a crystallization solvent in vacuum deposition of pentacene. The crystal sizes reached 200 ?m and their surface exhibits a molecularly step-and-terrace structure. There was no sign of IL molecules inside the crystal, and the impurity level of 6,13-pentacenequinone was also reduced. The average value of the field-effect mobility was not so inferior to those for the conventional pentacene single crystals, and the highest value exceeded 5 cm2/Vs, with the on/off current ratio of 104.

Takeyama, Yoko; Ono, Shimpei; Matsumoto, Yuji

2012-08-01

268

Acousto-optic phase modulation properties of coaxially-deposited ZnO transducers on single-mode fibers  

NASA Astrophysics Data System (ADS)

The acoustooptic (AO) phase modulation properties of coaxially deposited zinc oxide (ZnO) transducers on single mode optical fibers have been experimentally and theoretically investigated at several laboratories over the past 15 years. Maximum phase shifts are observed at distinct frequencies, corresponding to bulk acoustic waves in the fiber, over the transducer operating range of 200 MHz to 1.0 GHz. Phase shift values have been measured with both cw and pulsed signal inputs to the transducers from milliwatts to above 1 Watt. Transducer lengths have been varied from 30 mm to 2 mm to determine the effects of AO phase shift on the length of the interaction. Modulation efficiencies in the range of 0.2 to 0.3 radians per square root of input power (in mW) per centimeter, for 2 to 6 mm interaction lengths, have been observed at frequencies in the 200 to 400 MHz region corresponding to acoustic wavelengths on the order of the core dimensions of the optical fiber. The characteristics and capabilities of AO modulation in optical fibers with deposited coaxial ZnO transducers is discussed using examples from experimental work.

Hickernell, Fred S.

1999-10-01

269

Swimming photochromic azobenzene single crystals in triacrylate solution.  

PubMed

Self-motion of a growing single crystal of azobenzene chromophore in triacrylate solution (TA) is investigated in relation to the solid-liquid phase diagram bound by the solidus and liquidus lines. Upon thermal quenching from the isotropic melt to the crystal + liquid gap, various single crystals develop in a manner dependent on concentration and supercooling depth. During the crystal growth, TA solvent is rejected from the growing faceted fronts, enriching with TA in close proximity to the crystal-solution interface. The concentration gradient that formed as the result of TA expulsion induces convective flows in the solution and generates spatial variability of surface tension usually responsible for Marangoni effect. Either or both of these phenomena may have contributed to the observed self-motion including swimming, sinking, and floating of the azobenzene rhomboidal crystal in TA solution. A stationary rhomboidal crystal is also shown to swim upon irradiation with the UV light because of a mechanical torque generated by the trans-cis isomerization. Judging from the sinking or floating behavior of the azobenzene crystal, it may be inferred that the nucleation occurs at the solution-air interface. PMID:20491490

Milam, Kenneth; O'Malley, Garrett; Kim, Namil; Golovaty, Dmitry; Kyu, Thein

2010-06-17

270

Optical and structural properties of chalcone NLO single crystals  

NASA Astrophysics Data System (ADS)

Organic compound (E)-1-(4-methoxyphenyl)-3-(2,3,5-trichlorophenyl)prop-2-en-1-one [MPTCPP] with molecular formula C16H11Cl3O2 was synthesized using Claisen-Schmidt condensation reaction method. 1H NMR spectra was recorded to identify the various functional groups present in the compound and confirm the chemical structure. The single crystals were grown using slow evaporation solution growth technique. The UV-Visible spectrum study reveals that the crystal is transparent in the entire visible region and the absorption is observed at 364 nm. The Kurtz powder second harmonic generation (SHG) test shows that the MPTCPP is NLO active and its SHG efficiency is three times that of urea. Single crystal XRD study shows that the compound crystallizes in the monoclinic system with a space group Cc. The corresponding lattice parameters of the crystal are a = 28.215(5) , b = 3.9740(4) , c = 16.178(3) and V = 1503.0(4) 3. The micro hardness test was carried out and the work hardening coefficient value (n) of the crystal was found to be 1.48. This indicates that the crystal is hard and is suitable for device application. The thermal study reveals that the thermal stability of the crystal is good.

Rajesh Kumar, P. C.; Ravindrachary, V.; Janardhana, K.; Manjunath, H. R.; Karegouda, Prakash; Crasta, Vincent; Sridhar, M. A.

2011-11-01

271

''6-Degrees of Freedom'' Single Crystal Plasticity Experiments  

SciTech Connect

A deformation experiment has been developed specifically for the purpose of validation of dislocation dynamics simulations of plastic flow up to strains on the order of 1% [1]. The experiment has been designed so that a compressive uniaxial stress field is essentially super imposed on the test sample, and the crystal is free to deform with 3 orthogonal translation directions, and 3 rotation/tilt axes of freedom and has been given the name ''6-degrees of freedom'' (6DOF) experiment. The rotation, tilt and translation of the crystal are monitored by 5 laser displacement gages and 3 extensometers. Experiments are being performed on high purity Mo single crystals orientated for ''single slip''. All of the experiments are performed in pairs, with one test sample having highly polished surfaces for optical light and AFM slip-trace analyses, and the other having 4 strain gage rosettes mounted on the sides for measurement of the bi-axial surface strains during testing. All of the experimental data is used together to determine the slip activity of the orientated single crystal during deformation. Experimental results on high-purity Mo single crystals are presented. The results of these experiments show that slip behavior is in substantial deviation from the expected ''Schmid'' behavior. These experimental results bring into question some of the fundamental assumptions used in both the construction of crystal plasticity constitutive relationships and rules for dislocation mobility use in 3-D dislocation dynamics simulations.

Lassila, D H; Florando, J N; LeBlanc, M M; Arsenlis, T; Rhee, M

2003-05-21

272

Preparation of high purity ZnO nanobelts by thermal evaporation of ZnS.  

PubMed

High purity one-dimensional ZnO nanobelts were synthesized by thermally evaporating commercial ZnS powders in a hydrogen-oxygen mixture gas at 1050 degrees C. It was found that these ZnO nanobelts had a single crystal hexagonal wurtzite structure growing along the [0001] direction. They had a rectangle-shaped cross-section with typical widths of 20 to 100 nanometers and lengths of up to hundreds of micrometers with lattice constants of a = 0.325 nm and c = 0.520 nm. The self-catalytic hydrogen-oxygen assisted growth of ZnO nanobelt is discussed. The photoluminescence (PL) characterization of the ZnO nanobelts shows strong near-band UV emission (about 383 nm) and one broad peak at 501 nm, which indicates that the ZnO nanobelts have good potential application in optoelectronic devices. PMID:16573124

Chen, Zhi-Gang; Li, Feng; Liu, Gang; Tang, Yongbin; Cong, Hongtao; Lu, Gao Qing; Cheng, Hui-Ming

2006-03-01

273

Production of Unidirectionally Solidified Columnar Crystal and Single Crystal Superalloy Castings.  

National Technical Information Service (NTIS)

The material selection and casting as well as the properties and heat treatment practices of directionally solidified and single crystal superalloys have been reviewed. The presentation mainly concentrates on the turbine blade castings produced from the n...

J. E. Eklund

1992-01-01

274

Synthesis and Structure Characterization of Forsterite Single Crystal  

NASA Astrophysics Data System (ADS)

Forsterite (Mg2SiO4), the low-pressure polymorph of magnesium orthosilicate, is of great importance in the upper mantle due to its aboundance. Up to now, only powder samples of forsterite can be synthesized due to the difficulty of its crystal growth. Therefore, the exact crystal structure of forsterite is still an open question. The crystal structure of forsterite was firstly studied in 1926 by Brown and Bragg. Numerous experimental investigations have been performed in order to get the structure of the olivine group minerals at ambient conditions and a variety of temperature and pressures by using the advent of the computer, the single crystal diffractometer and the diamond cell. However, there are still considerable uncertaintes regarding the accuracy of its unit-cell parameter values. In this study, we synthesized for the first time high quality single crystals of forsterite using the Quickpress piston-cylinder apparatus. The single crystal of forsterite was synthesized by direct reaction of stoichiometric amounts of MgO and amorphous SiO2 (Alfa Aesar, 99.999%) in the presence of ~10-11 wt% distilled water at 2.0GPa, 1723 K for 12h. A colorless single crystal of Mg2SiO4 with size dimensions 0.160.110.04 mm was selected for single crystal X-ray diffraction analysis. The intensity data were collected with a Rigaku R-AXIS RAPID IP diffractometer by oscillation scans using graphite- monochromated Mo-K?0?6?0?6?7677?0?6?0?6?7699 radiation (?=0.71073 ). Cell refinement and data reduction were accomplished with RAPID AUTO program. The crystal structure was solved by direct methods with the SHELXL crystallographic software package. Single crystal X-ray diffraction analysis shows a crystal structure of orthorhombic space group Pnma (No. 62) with a = 10.2073(11) , b = 5.9863(5) , c = 4.7611(4) and Z = 4. Our new data provides new constraints for theoretical investigations of the physical and chemistry properties and behaviors of forsterite under various pressures.

Wang, C.; Jin, S.; Wang, X.; Liu, X.; Fleet, M. E.; Jin, Z.

2006-12-01

275

Enhancing the Mechanical Properties of Single-Crystal CVD Diamond  

SciTech Connect

Approaches for enhancing the strength and toughness of single-crystal diamond produced by chemical vapor deposition (CVD) at high growth rates are described. CVD processes used to grow single-crystal diamond in high density plasmas were modified to incorporate boron and nitrogen. Semi-quantitative studies of mechanical properties were carried out using Vickers indentation techniques. The introduction of boron in single-crystal CVD diamond can significantly enhance the fracture toughness of this material without sacrificing its high hardness ({approx}78 GPa). Growth conditions were varied to investigate its effect on boron incorporation and optical properties by means of photoluminescence, infrared, and ultraviolet-visible absorption spectroscopy. Boron can be readily incorporated into single-crystal diamond by the methods used, but with nitrogen addition, the incorporation of boron was hindered. The spectroscopic measurements indicate that nitrogen and boron coexist in the diamond structure, which helps explain the origin of the enhanced fracture toughness of this material. Further, low pressure/high temperature annealing can enhance the intrinsic hardness of single-crystal CVD diamond by a factor of two without appreciable loss in fracture toughness. This doping and post-growth treatment of diamond may lead to new technological applications that require enhanced mechanical properties of diamond.

Liang, Q.; Yan, C; Meng, Y; Lai, J; Krasnicki, S; Mao, H; Hemley, R

2009-01-01

276

Method for harvesting rare earth barium copper oxide single crystals  

DOEpatents

A method of preparing high temperature superconductor single crystals is disclosed. The method of preparation involves preparing precursor materials of a particular composition, heating the precursor material to achieve a peritectic mixture of peritectic liquid and crystals of the high temperature superconductor, cooling the peritectic mixture to quench directly the mixture on a porous, wettable inert substrate to wick off the peritectic liquid, leaving single crystals of the high temperature superconductor on the porous substrate. Alternatively, the peritectic mixture can be cooled to a solid mass and reheated on a porous, inert substrate to melt the matrix of peritectic fluid while leaving the crystals melted, allowing the wicking away of the peritectic liquid. 2 figs.

Todt, V.R.; Sengupta, S.; Shi, D.

1996-04-02

277

Molecular dynamics simulation of shock melting of aluminum single crystal  

NASA Astrophysics Data System (ADS)

Molecular dynamics method in conjunction with multi-scale shock technique is employed to study the melting characteristics of aluminum single crystal under dynamic conditions. The simulated results show that a linear relationship exists between the shock wave velocity and particle velocity, in good agreement with the experimental data. Comparing the Lindemann melting curve with the two Hugoniot curves for the solid and liquid phases, the Hugoniot melting is found to begin at 93.6 GPa and end at 140 GPa, which is consistent with the theoretical calculations. The impact of crystal defects on the melting characteristics of aluminum single crystal is also studied, and the results indicate that the pressure and temperature increase slightly for the system experiencing the same dynamic loading due to the crystal defects.

Ju, Yuanyuan; Zhang, Qingming; Gong, Zizheng; Ji, Guangfu; Zhou, Lin

2013-09-01

278

Structure and ferromagnetic properties of Co-doped ZnO powders  

Microsoft Academic Search

Single-phase Zn1?xCoxO (x=0.02, 0.04) powders were synthesized by a simple co-precipitation technique. X-ray diffraction analysis reveals that the Co-doped ZnO crystallizes in a wurtzite structure. The lattice constants of Co-doped ZnO powders decrease slightly when Co is doped into ZnO. Optical absorption spectra show a decrease in the bandgap with increasing Co content and also give an evidence of the

Xingyan Xu; Chuanbao Cao

2009-01-01

279

Isotropic behavior of an anisotropic material: single crystal silicon  

NASA Astrophysics Data System (ADS)

Zero defect single crystal silicon (Single-Crystal Si), with its diamond cubic crystal structure, is completely isotropic in most properties important for advanced aerospace systems. This paper will identify behavior of the three most dominant planes of the Single-Crystal Si cube (110), (100) and (111). For example, thermal and optical properties are completely isotropic for any given plane. The elastic and mechanical properties however are direction dependent. But we show through finite element analysis that in spite of this, near-isotropic behavior can be achieved with component designs that utilize the optimum elastic modulus in directions with the highest loads. Using glass frit bonding to assemble these planes is the only bonding agent that doesn't degrade the performance of Single-Crystal Si. The most significant anisotropic property of Single-Crystal Si is the Young's modulus of elasticity. Literature values vary substantially around a value of 145 GPa. The truth is that while the maximum modulus is 185 GPa, the most useful <110< crystallographic direction has a high 169 GPa, still higher than that of many materials such as aluminum and invar. And since Poisson's ratio in this direction is an extremely low 0.064, distortion in the plane normal to the load is insignificant. While the minimum modulus is 130 GPa, a calculated average value is close to the optimum at approximately 160 GPa. The minimum modulus is therefore almost irrelevant. The (111) plane, referred to as the natural cleave plane survives impact that would overload the (110) and/or (100) plane due to its superior density. While mechanical properties vary from plane to plane each plane is uniform and response is predictable. Understanding the Single-Crystal Si diamond cube provides a design and manufacture path for building lightweight Single-Crystal Si systems with near-isotropic response to loads. It is clear then that near-isotropic elastic behavior is achievable in Single-Crystal Si components and will provide subsecond thermal equilibrium and sub-micron creep.

McCarter, Douglas R.; Paquin, Roger A.

2013-09-01

280

Doubling microsecond single pulses in a KTP crystal  

SciTech Connect

The 90{sup 0} phase-matching SHG is performed for microsecond single pulses from a Nd{sup 3+}:YAP laser in a KTP crystal with the 29% conversion efficiency. The 90{sup 0} phase-matching temperature is 54{sup 0}C. The crystal surface damage threshold measured without and with an antireflection coating was 107{+-}11 and 40{+-}4 J cm{sup -2}, respectively. (nonlinear optical phenomena)

Abrosimov, S A; Kochiev, D G [A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Grechin, Sergei G [Scientific-Research Institute of Radioelectronics and Laser Technology at the N.E. Bauman Moscow State Technical University, Moscow (Russian Federation); Maklakova, N Yu; Semenenko, V N [Institute of Mineralogy and Petrography, Siberian Branch of the Russian Academy of Sciences, Novosibirsk (Russian Federation)

2001-07-31

281

Acquisition of Single Crystal Growth and Characterization Equipment  

Microsoft Academic Search

Final Report for DOE Grant No. DE-FG02-04ER46178 'Acquisition of Single Crystal Growth and Characterization Equipment'. There is growing concern in the condensed matter community that the need for quality crystal growth and materials preparation laboratories is not being met in the United States. It has been suggested that there are too many researchers performing measurements on too few materials. As

M. Brian Maple; Diego A. Zocco

2008-01-01

282

Infrared Optical Properties of Single Crystals of Tellurium  

Microsoft Academic Search

The fundamental optical absorption and photoconductivity of single crystals of tellurium has been investigated. Tellurium crystals exhibit dichroism in the infrared, i.e., the absorption constant depends on the polarization of the incident radiation. At 300K for radiation polarized perpendicular to the C axis the absorption edge, located by means of an arbitrary criterion, is at 3.82 microns (0.324 ev); for

Joseph J. Loferski

1954-01-01

283

Thermal properties of single-walled carbon nanotube crystal  

Microsoft Academic Search

In this work, the thermal properties of a single-walled carbon nanotube (SWCNT) crystal are studied. The thermal conductivity of the SWCNT crystal is found to have a linear dependence on temperature in the temperature range from 1.9 K to 100.0 K. In addition, a peak (658 W\\/mK) is found at a temperature of about 100.0 K. The thermal conductivity decreases

Li-Jun Hu; Ji Liu; Zheng Liu; Cai-Yu Qiu; Hai-Qing Zhou; Lian-Feng Sun

2011-01-01

284

Single crystal neutron diffraction study of sodium cyanide  

Microsoft Academic Search

The neutron diffraction pattern of a single crystal of cubic NaCN has been measured at 295K. These data and earlier results for KCN at 180 and 295K have been analyzed in terms of a model which expands the angular distribution of CN? orientations in symmetry-adapted spherical harmonics. From this analysis, the distributions of CN? in these crystals have been derived,

J. M. Rowe; D. G. Hinks; D. L. Price; S. Susman; J. J. Rush

1973-01-01

285

Thermal shock cracking of lithium niobate single crystal  

Microsoft Academic Search

The quantitative estimation of failure stress of a lithium niobate (LN) single crystal due to thermal shock was investigated.\\u000a Cylindrical test specimens were used in the thermal shock tests. The thermal stress of an LN test specimen under conditions\\u000a of thermal shock cracking was calculated from a computer program which takes account of the crystal anisotropy, using the\\u000a surface temperature

N. MIYAZAKI; A. HATTORI; H UCHIDA

1997-01-01

286

Single-point diamond turning of DAST crystals  

Microsoft Academic Search

Organic nonlinear optical crystal 4-dimethylamino-N-metyl-4-stilbazolium tosylate (DAST) can be used for new optical devices such as high frequency electro-optical sampling wavelength conversion, submillimeter wave generation, and terahertz-wave generation. The crystal is soft, brittle and hygroscopic so that it is very difficult to get optical surfaces by using conventional optical polishing process. This paper deals with single-point diamond turning for getting

Yoshiharu Namba; Masahiro Tsukahara; Atsuya Fushiki; Koji Suizu; Hiromasa Ito

2004-01-01

287

Defects in 700 keV oxygen ion irradiated ZnO  

NASA Astrophysics Data System (ADS)

It is well known that energetic oxygen ions induce heavy crystalline disorder in ZnO, however, systematic study on this regard is very much limited. Here, we present photoluminescence (PL), optical absorption and sheet resistance measurements on poly and single crystalline ZnO samples irradiated with 700 keV O ions. Results have been compared with the effects of 1.2 MeV Ar irradiation on similar ZnO target. Colour change of the samples with increasing O irradiation fluence has also been noted. Non-monotonic variation of room temperature sheet resistance with the increase of fluence has been observed for polycrystalline ZnO. Such an outcome has been understood as point defects transforming to bigger size clusters. Near band edge (NBE) PL emission is largely reduced due to O ion irradiation. However, at 10 K NBE emission can be observed for irradiated polycrystalline samples. Irradiated ZnO single crystal does not show any band to band transition even at 10 K. It is evident that dynamic recovery of defects is more effective in polycrystalline samples. Ultravioletvisible absorption spectrum of the irradiated ZnO crystal show pronounced sub-band gap absorption. Oxygen irradiation generated new absorption band in ZnO is at 3.05 eV. In the light of earlier reports, this particular band can be ascribed to absorption by neutral oxygen vacancy defects.

Pal, S.; Sarkar, A.; Chattopadhyay, S.; Chakrabarti, Mahuya; Sanyal, D.; Kumar, P.; Kanjilal, D.; Rakshit, T.; Ray, S. K.; Jana, D.

2013-09-01

288

High Resolution Technique and Instrument for Measuring Lattice Parameters in Single Crystals.  

National Technical Information Service (NTIS)

A method of measuring the lattice parameter in an unknown single crystal by comparing its diffraction angle to a standard single crystal, on a double-crystal diffractometer is disclosed. The method comprises several steps including mounting the unknown an...

M. Fatemi

1990-01-01

289

Crystal growth and characterization of a semiorganic nonlinear optical single crystal of gamma glycine  

NASA Astrophysics Data System (ADS)

Gamma glycine has been successfully synthesized by taking glycine and potassium chloride and single crystals have been grown by solvent evaporation method for the first time. The grown single crystals have been analyzed with XRD, Fourier transform infrared (FTIR), and thermo gravimetric and differential thermal analyses (TG/DTA) measurements. Its mechanical behavior has been assessed by Vickers microhardness measurements. Its nonlinear optical property has been tested by Kurtz powder technique. Its optical behavior was examined by UV vis., and found that the crystal is transparent in the region between 240 and 1200 nm. Hence, it may be very much useful for the second harmonic generation (SHG) applications.

Prakash, J. Thomas Joseph; Kumararaman, S.

2008-11-01

290

Nucleation kinetics, growth and studies of ?-alanine single crystals  

NASA Astrophysics Data System (ADS)

Solubility and metastable zone width for the re-crystallized salt of ?-alanine was determined. Induction period measurement for the selected supersaturation ratios at room temperature (31 C) was carried out for supersaturated aqueous solutions of ?-alanine and it is noticed that induction period decreases with increase of supersaturation ratio. The nucleation parameters such as Gibbs free energy change, radius and number of molecules of the critical nucleus, interfacial tension and the nucleation rate have been evaluated by classical nucleation theory. Single crystals of ?-alanine were grown using the optimized nucleation parameters by solution method and grown crystals have been subjected to various studies like XRD studies, FTIR, optical, thermal and SHG studies.

Shanthi, D.; Selvarajan, P.; HemaDurga, K. K.; Lincy Mary Ponmani, S.

2013-06-01

291

Epitaxial Growth of WOx Nanorod on Single Crystal Tungsten Substrate  

NASA Astrophysics Data System (ADS)

Nanorods of substoichiometric tungsten oxide (WOx) were grown on single crystal tungsten substrate. The grown nanorods were investigated with scanning electron micrope and atomic force microscope. WOx nanorods were grown on W(001) in accordance with epitaxial relationship between WO3 crystals and W(001) surface. The results indicate that the WO3 crystals formed at the initial stage act as the nuclei of WOx nanorods. Nanorod growth of certain epitaxial directions can be selectively enhanced by choosing growth methods or choosing suitable crystallographic orientation of substrate surface.

Shingaya, Yoshitaka; Nakayama, Tomonobu

292

Lithium niobate single-crystal and photo-functional device  

SciTech Connect

Provided are lithium niobate single-crystal that requires a low voltage of not larger than 10 kV/nm for its ferroelectric polarization inversion and of which the polarization can be periodically inverted with accuracy even at such a low voltage, and a photo-functional device comprising the crystal. The crystal has a molar fraction of Li.sub.2 O/(Nb.sub.2 O.sub.5 +Li.sub.2 O) of falling between 0.49 and 0.52. The photo-functional device can convert a laser ray being incident thereon.

Gopalan, Venkatraman (State College, PA); Mitchell, Terrence E. (Los Alamos, NM); Kitamura, Kenji (Tsukuba, JP); Furukawa, Yasunori (Tsukuba, JP)

2001-01-01

293

Polymer single crystal meets nanoparticle, toward ordered hybrid materials  

NASA Astrophysics Data System (ADS)

Judiciously selected polymer single crystal (PSC) systems can interplay with 1-D and 0-D nanoparticles, forming ordered hybrid structures. In this presentation, I will first focus on patterning PSCs on individual carbon nanotubes (CNT). Using both controlled solution crystallization, thin film crystallization and physical vapor deposition methods, CNTs were periodically decorated with PSCs, resulting in nano hybrid shish-kebab (NHSK) structures. Because the polymer kebabs can be easily removed, these unique NHSKs can serve as templates to fabricate a variety of CNTs-containing hybrid materials with controlled pattering on the CNT surface. Sub-20 nanometer alternating patterning was achieved by using crystalline block copolymers. The mechanism was attributed to the crystallization induced block copolymer phase separation. This pattern was successfully used to template nanoparticles (NP) pattering on CNTs. In the second part of the talk, I will discuss fabricating Janus NPs and patterning these NPs using PSCs. Single crystals of thiol-terminated polyethylene oxide (PEO) were incubated in a gold sol. Au-S bonds were formed between the AuNPs and the PEO single crystal surfaces. The inter-particle spacing was controlled by PEO molecular weights, the incubation time, and the annealing temperatures after incubation. The planar geometry of the PSCs led to Janus NP formation. A series of NP dimers, trimers and tetramers were synthesized. NP nanowires were also fabricated. We anticipate that this observation could lead to controlled synthesis of artificial molecules and NP chains for a variety of optical, electronic, and biomedical applications.

Li, Christopher

2009-03-01

294

Growth and characterization of single crystal of pentachloropyridine  

NASA Astrophysics Data System (ADS)

Bulk single crystals of pentachloropyridine (PCP) were grown by the Bridgman Stockbarger method. The single crystalline nature of the grown crystals was confirmed using powder X-ray diffraction (XRD) techniques. These were transparent in the 315 2000 nm range. The second harmonic generation (SHG) efficiency of polycrystalline materials using Kurtz powder technique was found to be twice that of the well-known organic nonlinear optical (NLO) material, urea. The mixing behavior of PCP with succinonitrile (SCN) and its effect on SHG and micro-hardness of PCP, along with the physicochemical properties of different compositions of PCP and SCN system were studied in detail. Bulk single crystals of the PCP solid solution containing 0.02 mole fraction of SCN have also been grown using the Bridgman Stockbarger technique.

Rai, R. N.; Varma, K. B. R.

2005-11-01

295

Synthesis and properties of erbium oxide single crystals  

SciTech Connect

Erbium oxide (Er{sub 2}O{sub 3}, erbia) is a highly stable cubic rare earth oxide with a high melting point of 2,430 C. Because of this, it may have potential applications where high temperature stability and corrosion resistance are required. However, relatively little is known about the properties of this oxide ceramic. The authors have employed a xenon optical floating zone unit with a temperature capability of 3,000 C to grow high quality single crystals of erbia. The conditions for single crystal growth of erbia have been established. The mechanical properties of erbia single crystals have been initially examined using microhardness indentation as a function of temperature.

Petrovic, J.J.; Romero, R.S.; Mendoza, D.; Kukla, A.M.; Hoover, R.C.; McClellan, K.J.

1999-04-01

296

All-glass endless single-mode photonic crystal fibers.  

PubMed

Endless single-mode fibers, which remain single mode over their entire range of guidance, are, to the best of our knowledge, the first reported unique application of photonic crystal fibers. These endless single-mode fibers are made by omitting a single air hole in a periodic array of small air holes in a background silica glass. The feasibility of all-glass endless single-mode photonic crystal fibers where the air holes are replaced by a glass with vanishingly small refractive index contrast relative to silica is first studied theoretically and then demonstrated experimentally. This new all-glass design enables not only ease and consistency of fabrication but also the convenience to be handled and spliced like conventional fibers. PMID:18978880

Dong, Liang; McKay, Hugh A; Fu, Libin

2008-11-01

297

Sliding and rolling frictional behavior of a single ZnO nanowire during manipulation with an AFM  

NASA Astrophysics Data System (ADS)

The frictional behavior during manipulation of a single ZnO nanowire with a mass of about 18.7 ng placed horizontally on a Si wafer was examined using atomic force microscopy (AFM). The frictional force measured was in the range of 36.4 nN to 69.3 nN, which corresponded to extremely high friction coefficients of 242 and 462, respectively. However, when the adhesion force of the nanowire was considered, the friction coefficients were similar to the values typically encountered in macro-scale systems. During manipulation of the nanowire, both rolling and sliding motions were observed depending on the nanowire-Si frictional interaction. Unlike macro-scale systems, the difference between the frictional forces of rolling/sliding and pure sliding motions of the nanowire was not drastic.

Kim, Hyun-Joon; Kang, Kyeong Hee; Kim, Dae-Eun

2013-06-01

298

Structural, spectral and mechanical studies of bimetallic crystal: cadmium manganese thiocyanate single crystals  

NASA Astrophysics Data System (ADS)

A nonlinear optical bimetallic thiocyanate complex crystal, cadmium manganese thiocyanate (CMTC) has been successfully synthesized. The growth of single crystals of cadmium manganese thiocyanate has been accomplished from aqueous solution using slow evaporation method. The presence of manganese and cadmium in the synthesized material was confirmed through energy dispersive spectrum (EDS) analysis. Structural analysis was carried out using powder X-ray diffractometer (PXRD) and crystalline perfection of the grown crystals was ascertained by high-resolution X-ray diffraction (HRXRD) analysis. Fourier transform infrared (FTIR) spectrum was taken to confirm the functional groups. The transmittance spectrum of the crystal in the UV-visible region has been recorded and the cutoff wavelength has been determined. The dielectric measurements for the crystals were performed for various frequencies and temperatures. The mechanical properties were evaluated by Vickers microhardness testing, which reveals hardness and stiffness constant of the crystals.

Manikandan, M.; Vijaya Prasath, G.; Bhagavannarayan, G.; Vijayan, N.; Mahalingam, T.; Ravi, G.

2012-09-01

299

Synthesis of Large Single Crystals of LaMnPO  

NASA Astrophysics Data System (ADS)

The compound LaMnPO is isostructural with LaFeAsO, a recently discovered high-temperature superconductor, but optical spectroscopy and transport measurements of this compound have been heretofore limited by small crystal size. Accordingly, crystal syntheses from Sn, Pb and molten salt fluxes (including NaCl/KCl, LiCl/NaCl, KCl, CaCl2, BaCl2/CaCl2 and KCl/CaCl2) were investigated. Fluorine doping was explored; concentrations less than 30 at.% (nominal) had no effect on crystal size; concentrations greater than 40 at.% (nominal) did not yield crystals. Once growth parameters were optimized, the crystals grew in a flat rectangular shape with black luster; their composition was verified with powder and single crystal x-ray diffraction. Successful growths yielded crystals with dimensions up to 3.2 mm by 1 mm by 10 ?m, a significant improvement upon previously reported growths in the literature. These large crystals enabled our group to perform a wide range of experiments that were previously restricted to polycrystalline materials. It may be feasible to extend these methods to the synthesis of similar compounds.

Smith, Greg; Simonson, Jack; Marques, Carlos; Leyva, Victor; Aronson, Meigan

2011-03-01

300

Electron transport in rubrene single-crystal transistors  

NASA Astrophysics Data System (ADS)

We report a study of impurity effects on the electron transport of rubrene single crystals. A significant improvement of electron carrier mobility up to 0.81 cm2/V s is achieved by performing multiple purifications of single crystals and device aging inside an N2-filled glove box. The hole/electron mobility ratio obtained is in good agreement with the reported theoretical calculation, suggesting that the intrinsic electron transport of organic semiconductors is also exploitable in a manner similar to that of hole transport.

Bisri, Satria Zulkarnaen; Takenobu, Taishi; Takahashi, Tetsuo; Iwasa, Yoshihiro

2010-05-01

301

Advanced piezoelectric single crystal based transducers for naval sonar applications  

Microsoft Academic Search

TRS is developing new transducers based on single crystal piezoelectric materials such as Pb(Mg1\\/3Nb2\\/3)x-1TixO3 (PMN-PT). Single crystal piezoelectrics such as PMN-PT exhibit very high piezoelectric coefficients (d33 ~ 1800 to >2000 pC\\/N) and electromechanical coupling factors (k33 > 0.9), respectively, which may be exploited for improving the performance of broad bandwidth and high frequency sonar. Apart from basic performance, much

Kevin A. Snook; Paul W. Rehrig; Wesley S. Hackenberger; Xiaoning Jiang; Richard J. Meyer Jr.; Douglas Markley

2005-01-01

302

Energy considerations in crack deflection phenomenon in single crystal silicon  

Microsoft Academic Search

Crack deflection in single-crystal brittle occurs when a crack, propagating on one cleavage plane, chooses, from energy\\u000a considerations, to continue propagating on another cleavage plane. This phenomenon was identified during dynamic crack propagation\\u000a experiments of thin, rectangular [001] single-crystal (SC) silicon specimens subjected to three-point bending (3PB). Specimens\\u000a with long pre-cracks (hence propagating at a low energy and velocity) cleave

Dov Sherman

2006-01-01

303

Apparatus And Method For Producing Single Crystal Metallic Objects  

DOEpatents

A mold is provided for enabling casting of single crystal metallic articles including a part-defining cavity, a sorter passage positioned vertically beneath and in fluid communication with the part-defining cavity, and a seed cavity positioned vertically beneath and in fluid communication with the sorter passage. The sorter passage includes a shape suitable for encouraging a single crystal structure in solidifying molten metal. Additionally, a portion of the mold between the sorter passage and the part-defining cavity includes a notch for facilitating breakage of a cast article proximate the notch during thermal stress build-up, so as to prevent mold breakage or the inclusion of part defects.

Huang, Shyh-Chin (Latham, NY); Gigliotti, Jr., Michael Francis X. (Scotia, NY); Rutkowski, Stephen Francis (Duanesburg, NY); Petterson, Roger John (Fultonville, NY); Svec, Paul Steven (Scotia, NY)

2006-03-14

304

Lead pyrovanadate single crystal as a new SRS material  

SciTech Connect

Lead pyrovanadate Pb{sub 2}V{sub 2}O{sub 7} single crystals of optical quality suitable for laser experiments are obtained. Vibrational modes are identified based on the analysis of the polarised Raman spectra of the single crystals. The main parameters (width at half maximum, peak and integral intensities) of the spectral lines most promising for SRS conversion in this material are estimated. These parameters are compared with the corresponding parameters of the most frequently used lines of known Raman materials: yttrium and gadolinium vanadates, potassium and lead tungstates, and lead molybdate. (active media)

Basiev, Tasoltan T; Voronko, Yu K; Maslov, Vladislav A; Sobol, A A; Shukshin, V E [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2011-02-28

305

Annealing Effect on Photovoltages of Quartz Single Crystals  

NASA Astrophysics Data System (ADS)

We investigate the photovoltaic effects of quartz single crystals annealed at high temperatures in ambient atmosphere. The open-circuit photovoltages and surface morphologies strongly depend on the heating treatments. When the annealing temperature increases from room temperature to 900C, the rms roughness of quartz single crystal wafers increases from 0.207 to 1.011 nm. In addition, the photovoltages decrease from 1.994?V at room temperature to 1.551 ?V after treated at 500C, and then increase up to 9.8 ?V after annealed at 900C. The inner mechanism of the present photovoltaic response and surface morphologies is discussed.

Tian, Lu; Zhao, Song-Qing; Zhao, Kun

2010-12-01

306

How a silver dendritic mesocrystal converts to a single crystal  

NASA Astrophysics Data System (ADS)

In this paper, we demonstrate how a silver dendrite transforms from mesocrystal into single crystal and the stability for a dendritic silver mesocrystal within a Sn/AgNO3 galvanic replacement reaction. Our findings provide the direct evidence and visible picture of the transformation from mesocrystal to single crystalline structure and further confirm the particle-mediated crystallization mechanism. At the initial stage of the transformation, there is a crystallographic fusion process, dominated by oriented attachment mechanism. Ostwald ripening also plays an important role in forming smooth surface and regular shape of the final nanocrystal.

Fang, Jixiang; Ding, Bingjun; Song, Xiaoping; Han, Yong

2008-04-01

307

How a silver dendritic mesocrystal converts to a single crystal  

SciTech Connect

In this paper, we demonstrate how a silver dendrite transforms from mesocrystal into single crystal and the stability for a dendritic silver mesocrystal within a Sn/AgNO3 galvanic replacement reaction. Our findings provide the direct evidence and visible picture of the transformation from mesocrystal to single crystalline structure and further confirm the particle-mediated crystallization mechanism. At the initial stage of the transformation, there is a crystallographic fusion process, dominated by oriented attachment mechanism. Ostwald ripening also plays an important role in forming smooth surface and regular shape of the final nanocrystal.

Fang, J.; Ding, B.; Song, X.; Han, Y.

2008-05-02

308

Two-photon-induced singlet fission in rubrene single crystal  

NASA Astrophysics Data System (ADS)

The two-photon-induced singlet fission was observed in rubrene single crystal and studied by use of femtosecond pump-probe spectroscopy. The location of two-photon excited states was obtained from the nondegenerate two-photon absorption (TPA) spectrum. Time evolution of the two-photon-induced transient absorption spectra reveals the direct singlet fission from the two-photon excited states. The TPA absorption coefficient of rubrene single crystal is 52 cm/GW at 740 nm, as obtained from Z-scan measurements. Quantum chemical calculations based on time-dependent density functional theory support our experimental data.

Ma, Lin; Galstyan, Gegham; Zhang, Keke; Kloc, Christian; Sun, Handong; Soci, Cesare; Michel-Beyerle, Maria E.; Gurzadyan, Gagik G.

2013-05-01

309

Nanomechanical resonant structures in single-crystal diamond  

NASA Astrophysics Data System (ADS)

With its host of outstanding material properties, single-crystal diamond is an attractive material for nanomechanical systems. Here, the mechanical resonance characteristics of freestanding, single-crystal diamond nanobeams fabricated by an angled-etching methodology are reported. Resonance frequencies displayed evidence of significant compressive stress in doubly clamped diamond nanobeams, while cantilever resonance modes followed the expected inverse-length-squared trend. Q-factors on the order of 104 were recorded in high vacuum. Results presented here represent initial groundwork for future diamond-based nanomechanical systems which may be applied in both classical and quantum applications.

Burek, Michael J.; Ramos, Daniel; Patel, Parth; Frank, Ian W.; Lon?ar, Marko

2013-09-01

310

Preparation of single-crystal copper ferrite nanorods and nanodisks  

SciTech Connect

This article, for the first time, reports the preparation of single-crystal copper ferrite nanorods and nanodisks. Using amorphous copper ferrite nanoparticles synthesized by reverse micelle as reaction precursor, single-crystal copper ferrite nanorods were synthesized via hydrothermal method in the presence of surfactant polyethylene glycol (PEG), however, copper ferrite nanodisks were prepared through the same procedures except the surfactant PEG. The resulting nanomaterials have been characterized by powder X-ray diffraction (XRD), selected electron area diffraction (SEAD), and transmission electron microscopy (TEM). The bulk composition of the samples was determined by means of X-ray photoelectron spectroscopy (XPS)

Du Jimin [Center for Molecular Sciences, CAS Key Laboratory of Colloid, Interfacial and Chemical Thermodynamics, Institute of Chemistry, Chinese Academy of Sciences, No. 2 Beiyijie, Zhongguancun, Beijing 100080 (China); Liu Zhimin [Center for Molecular Sciences, CAS Key Laboratory of Colloid, Interfacial and Chemical Thermodynamics, Institute of Chemistry, Chinese Academy of Sciences, No. 2 Beiyijie, Zhongguancun, Beijing 100080 (China)]. E-mail: liuzm@iccas.ac.cn; Wu Weize [Center for Molecular Sciences, CAS Key Laboratory of Colloid, Interfacial and Chemical Thermodynamics, Institute of Chemistry, Chinese Academy of Sciences, No. 2 Beiyijie, Zhongguancun, Beijing 100080 (China); Li Zhonghao [Center for Molecular Sciences, CAS Key Laboratory of Colloid, Interfacial and Chemical Thermodynamics, Institute of Chemistry, Chinese Academy of Sciences, No. 2 Beiyijie, Zhongguancun, Beijing 100080 (China); Han Buxing [Center for Molecular Sciences, CAS Key Laboratory of Colloid, Interfacial and Chemical Thermodynamics, Institute of Chemistry, Chinese Academy of Sciences, No. 2 Beiyijie, Zhongguancun, Beijing 100080 (China)]. E-mail: hanbx@iccas.ac.cn; Huang Ying [Center for Molecular Sciences, CAS Key Laboratory of Colloid, Interfacial and Chemical Thermodynamics, Institute of Chemistry, Chinese Academy of Sciences, No. 2 Beiyijie, Zhongguancun, Beijing 100080 (China)

2005-06-15

311

Single crystal piezoelectric composite transducers for ultrasound NDE applications  

NASA Astrophysics Data System (ADS)

Single crystal piezoelectric composite transducers including 75 MHz PC-MUT (piezoelectric composite micromachined ultrasound transducers), diced 10 MHz and 15 MHz 1-3 composite transducers were successfully demonstrated with broad bandwidth and high sensitivity. In this paper, the design, fabrication and characterization of composite transducers are reported. C-scan experiments for SiC ceramic samples were performed using these composite transducers as well as some commercial NDE transducers. The results suggest that significant improvements in resolution and penetration depth can be achieved in C-scan NDE imaging using single crystal composite broadband transducers.

Jiang, Xiaoning; Snook, Kevin; Walker, Thomas; Portune, Andrew; Haber, Richard; Geng, Xuecang; Welter, John; Hackenberger, Wesley S.

2008-04-01

312

Structural and optical properties of a new chalcone single crystal  

NASA Astrophysics Data System (ADS)

A new nonlinear optical material 1-(4-methylthiophenyl)-3-(4-methoxyphenyl)prop-2-en-1-one with molecular formula C17H16O2S was synthesized by using the ClaisenSchmidt condensation reaction method. The Various functional groups present in the compound were identified using recorded FT-IR spectrum. The crystal growth parameters have been studied using solubility test and acetone is found to be a very good solvent for the crystal growth at an ambient temperature. The transparent high quality single crystals up to a size of 2622 mm3 were grown using the slow evaporation solution growth technique. UVvisible study was carried out and the spectrum reveals that the crystal is transparent in the entire visible region and absorptive in the UV region. The refractive index is determined using Brewster's angle method. The optical energy band gap of the material is measured using Tauc's plot and the direct method. The single crystal XRD of MMPP crystal shows the following cell parameters: a=5.9626(2) , b=15.3022(6) , c=16.0385(7) , ?=?=?=90, volume=1463.37(10) 3 with a space group of Pna21. The compound MMPP exhibits optical nonlinearity (NLO) and its second order NLO efficiency is 3.15 times to that of urea. The effect of functional groups OCH3 and SCH3 on the non-linearity as well as the structural property of the compound has been discussed. The crystal is thermally stable. High NLO efficiency, good thermal stability, good transparency and ability to grow as a high quality single crystal make this material very attractive for opto-electronic applications.

Rajesh Kumar, P. C.; Ravindrachary, V.; Janardhana, K.; Poojary, Boja

2012-09-01

313

Super-uniform ZnO nanohelices synthesized via thermal evaporation  

NASA Astrophysics Data System (ADS)

Super-uniform single crystal ZnO nanohelices synthesized by Sb induced thermal evaporation is reported. The ZnO nanohelices as a whole have an axial direction of <0001>, perfect hexagonal cross section and length of tens of micrometres. There are six blocks in each period of the helices, and they grow along six equivalent directions <0111>. The typical pitch distance, mean diameter and thickness of the nanowire is about 600, 400 and 100 nm. Calculation according to a simple model shows that the helical structure is energetically favourable. It could be used as photonic crystals or construct blocks in nanoscale optoelectronic and electromechanical systems. In addition to ZnO nanohelices, zigzag ZnO nanostructures were also obtained.

Gao, Hong; Zhang, Xitian; Zhou, Mingyu; Zhang, E.; Zhang, Zhiguo

2006-12-01

314

Microstructure and crystal defects in epitaxial ZnO film grown on Ga modified (0001) sapphire surface  

SciTech Connect

Surface modification of sapphire (0001) by Ga can eliminate multiple rotation domains in ZnO films. The existence of Ga at ZnO/sapphire interface was confirmed by x-ray energy dispersive spectroscopy in a transmission electron microscope. Atomic detail of mismatch dislocations at interface was imaged by high resolution transmission electron microscopy. Inside the ZnO film, there is a high density of stacking fault. Both pure gliding of ZnO (0001) plane and condensation of vacancies or interstatials are possible mechanisms to generate the stacking fault.

Sun, H.P.; Pan, X.Q.; Du, X.L.; Mei, Z.X.; Zeng, Z.Q.; Xue, Q.K. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); State Key Laboratory for Surface Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100081 (China)

2004-11-08

315

Intracellular ZnO Nanorods Conjugated with Protoporphyrin for Local Mediated Photochemistry and Efficient Treatment of Single Cancer Cell  

NASA Astrophysics Data System (ADS)

ZnO nanorods (NRs) with high surface area to volume ratio and biocompatibility is used as an efficient photosensitizer carrier system and at the same time providing intrinsic white light needed to achieve cancer cell necrosis. In this letter, ZnO nanorods used for the treatment of breast cancer cell (T47D) are presented. To adjust the sample for intracellular experiments, we have grown the ZnO nanorods on the tip of borosilicate glass capillaries (0.5 ?m diameter) by aqueous chemical growth technique. The grown ZnO nanorods were conjugated using protoporphyrin dimethyl ester (PPDME), which absorbs the light emitted by the ZnO nanorods. Mechanism of cytotoxicity appears to involve the generation of singlet oxygen inside the cell. The novel findings of cell-localized toxicity indicate a potential application of PPDME-conjugated ZnO NRs in the necrosis of breast cancer cell within few minutes.

Kishwar, S.; Asif, M. H.; Nur, O.; Willander, M.; Larsson, Per-Olof

2010-10-01

316

Room temperature single-photon Source:Single-dye molecule fluorescence in Liquid Crystal host  

Microsoft Academic Search

We report on new approaches toward an implementation of an efficient, room temperature, deterministically polarized, single-photon source (SPS) on demand-a key hardware element for quantum information and quantum communication. Operation of a room temperature SPS is demonstrated via photon antibunching in the fluorescence from single terrylene-dye molecules embedded in a cholesteric liquid crystal host. Using oxygen-depleted liquid crystal hosts, dye-bleaching

Svetlana G. Lukishova; Ansgar W. Schmid; Andrew J. McNamara; Robert W. Boyd; Carlos R. Stroud

2003-01-01

317

Growth and some properties of large praseodymium pentaphosphate single crystals  

SciTech Connect

By means of a high-temperature solution-seeded method, praseodymium pentaphosphate (PrPP) single crystals have been grown directly by using Pr{sub 6}O{sub 11} and H{sub 3}PO{sub 4} as raw materials. The dimension of a PrPP single crystal even reaches as large as 72 {times} 22 {times} 13 mm. Its morphology, XRD, and specific heat data are all determined. In addition, the Raman spectra of PrPP, LaP{sub 5}O{sub 14} (LaPP), and Pr{sub x}La{sub 1-x}P{sub 5}O{sub 14} (PrLaPP) crystal series are also reported in this paper. The phonon soft modes of PrPP crystal corresponding to A{sub g}-B{sub 2g} and B{sub g}-B{sub 3g} have been observed in two geometrical arrangements, Z(YZ)X and Z(XZ)Y, respectively. It is shown that the frequencies, intensities, and peak shapes change evidently with temperature. On the basis of the changes of the soft modes with the temperature, the temperature at which the C{sub 2h}-D{sub 2h} ferroelastic phase transition of PrPP crystal takes place can be deduced. Accordingly, the ferroelastic phase-transition temperature of PrPP crystal is obtained, i.e., 137 {plus minus} 1{degree}C.

Li, Lixia; Wang, Jiyang; Yang, Zhaohe; Jiang, Huizhu; Liu, Yaogang (Shandong Univ., Jinan (China))

1989-09-07

318

Single-point diamond turning of DAST crystals  

NASA Astrophysics Data System (ADS)

Organic nonlinear optical crystal 4-dimethylamino-N-metyl-4-stilbazolium tosylate (DAST) can be used for new optical devices such as high frequency electro-optical sampling wavelength conversion, submillimeter wave generation, and terahertz-wave generation. The crystal is soft, brittle and hygroscopic so that it is very difficult to get optical surfaces by using conventional optical polishing process. This paper deals with single-point diamond turning for getting optical surfaces on DAST crystals. Three typical planes on DAST crystals were finished by single-point diamond turning. The quality of single-point diamond turned surface depends upon the crystallographic plane, cutting direction, cutting speed, depth of cut, feed rate, rake angle, nose radius of diamond tool, tool clearance angle, tool wear, lubricant and its supplying method. The turned surface was measured with a Nomarski interference microscope, atomic force microscope, and a three-dimensional optical profiler. By optimizing the machining conditions, 0.33 nm rms surface roughness and 8.7 nm p-v flatness in 1 mm square were obtained on a b-plane of DAST crystal.

Namba, Yoshiharu; Tsukahara, Masahiro; Fushiki, Atsuya; Suizu, Koji; Ito, Hiromasa

2004-01-01

319

Localization of Deformation in Copper Single Crystals During Explosive Collapse  

Microsoft Academic Search

It is established that high-rate axisymmetric loading of single crystals by the method of explosive collapse of a hollow thick-walled cylinder causes deformation that involves all active close-packed slip systems. The spatial distribution of macroscopic sites of strain localization is determined by the crystallography of the active systems in single-crystalline samples. The established correlation between the observed shear bands in

2003-01-01

320

Single Polarizer Liquid Crystal Display Mode with Fast Response  

Microsoft Academic Search

We propose a single polarizer liquid crystal display (LCD) with a fast response that was designed using a polarization-dependent microlens array fabricated by the planarization of a curved lens surface with a liquid crystalline polymer. The single polarizer LCD is operated by the polarization-dependent focusing properties of a microlens consisting of a circular stop-mask and complementary open mask. Fast response

Young Wook Kim; Jiwon Jeong; Se Hyun Lee; Jae-Hoon Kim; Chang-Jae Yu

2011-01-01

321

Ion-beam-produced structural defects in ZnO  

Microsoft Academic Search

We study the evolution of lattice defects in single-crystal ZnO bombarded with 60-keV 28Si and 300-keV 197Au ions at 77 and 300 K. To characterize ion-beam-produced structural defects, we use a combination of Rutherford backscattering\\/channeling (RBS\\/C) spectrometry, cross-sectional transmission electron microscopy (XTEM), x-ray photoelectron spectroscopy, and atomic force microscopy. Results show that ZnO exhibits strong dynamic annealing, and even high-dose

S. O. Kucheyev; J. S. Williams; C. Jagadish; J. Zou; Cheryl Evans; A. J. Nelson; A. V. Hamza

2003-01-01

322

Growth and spectroscopic characteristics of Yb:LPS single crystal  

NASA Astrophysics Data System (ADS)

For the first time, a high optical quality Yb3+-doped lutetium pyrosilicate laser crystal Lu2Si2O7 (LPS) was grown by the Czochralski (Cz) method. The segregation coefficient of ytterbium ion in Yb:LPS crystal detected by the inductively coupled plasma atomic emission spectrometer (ICP-AES) method is equal to 0.847. X-ray powder diffraction result confirms the C2/m phase monoclinic space group of the grown crystal and the peaks corresponding to different phases were indexed. The absorption and fluorescence spectra, as well as fluorescence decay lifetime of Yb3+ ion in LPS have been investigated. The absorption and fluorescence cross-sections of the transitions 2F7/2?2F5/2 of Yb3+ ion in LPS crystal have been determined. The advantages of the Yb:LPS crystal including high crystal quality, quasi-four-level laser operating scheme, high absorption cross-sections (1.3310-20 cm2) and particularly broad emission bandwidth (62 nm) indicated that the Yb:LPS crystal seemed to be a promising candidate used as compact, efficient thin chip lasers when LD is pumped at 940 and 980 nm due to its low-symmetry monoclinic structure and single crystallographic site.

Zheng, Lihe; Zhao, Guangjun; Yan, Chengfeng; Yao, Gang; Xu, Xiaodong; Su, Liangbi; Xu, Jun

2007-06-01

323

Growth of hafnium dioxide-based single crystals  

SciTech Connect

This paper considers the induction melting of hafnium dioxide with rare earth oxide mixtures, and studies defects in resulting hafnium dioxide single crystals stabilized by the oxides of scandium, yttrium, neodymium, gadolinium, terbium, erbium, and ytterbium at concentrations between 1 and 33 mole %. Crystallization of solid solutions occurs in the systems HfO/sub 2/Ln/sub 2/O/sub 3/. For the HfO/sub 2/-Er/sub 2/O/sub 3/ system, single crystals grow at 11-33 mole %, for HfO/sub 2/-Tb/sub 2/O/sub 3/ at 10-20 mole % and for HfO/sub 3/Sc/sub 2/O/sub 3/ (Nd/sub 2/O/sub 3/) at 10 mole % rare-earth oxide.

Voronov, V.V.; Lavrishchev, S.V.; Markov, N.I.; Miftyakhetdinova, N.R.; Osiko, V.V.; Tatarintsev, V.M.; Zufarov, M.A.

1986-03-01

324

Technical report of ISSP. Ser. A, no. 2677: Octa-twin model of tetrapod ZnO crystals  

Microsoft Academic Search

The characteristic morphology of tetrapod-shaped ZnO particles grown by oxidizing zinc vapor in air has been thoroughly interpreted by the growth process from octahedral multiple-twin embryos. The origin of the tetrapod-shape consists in: (1) formation of the octahedral multiple-twin due to small c\\/a ratio of the wurtzite ZnO; (2) inversion-type twin boundaries; and (3) a large growth anisotropy with respect

Shin Takeuchi; Hiroshi Iwanaga; Mitsuhiro Fujii

1993-01-01

325

Low temperature magnetic transitions of single crystal HoBi  

NASA Astrophysics Data System (ADS)

We present resistivity, specific heat and magnetization measurements in high quality single crystals of HoBi, with a residual resistivity ratio of 126. We find, from the temperature and field dependence of the magnetization, an antiferromagnetic transition at 5.7 K, which evolves, under magnetic fields, into a series of up to five metamagnetic phases.

Fente, A.; Suderow, H.; Vieira, S.; Nemes, N. M.; Garca-Hernndez, M.; Bud'ko, S. L.; Canfield, P. C.

2013-10-01

326

Studies of the Vaporization Mechanism of Gallium Arsenide Single Crystals  

Microsoft Academic Search

The kinetics of vaporization of gallium arsenide single crystals into vacuum have been investigated using microbalance and mass spectrometric techniques in the temperature range 700900 C. Although gallium arsenide vaporized incongruently to yield liquid gallium and arsenic vapor molecules, initial steady state evaporation rates can be obtained in the temperature range of study. The total evaporation rates and the activation

C. Y. Lou; G. A. Somorjai

1971-01-01

327

Single crystal silicon as a low-temperature structural material  

Microsoft Academic Search

In neutron scattering applications, it is frequently desirable to construct a sample container from a material that is strong but has very little neutron absorption of scattering. Single crystal silicon is very good by these criteria but it is difficult to work with because of its brittleness. A technique for gluing silicon was developed that yields high strength joints at

P. R. Roach

1984-01-01

328

Ductile-regime turning mechanism of single-crystal silicon  

Microsoft Academic Search

Diamond turning of single-crystal silicon was carried out along all the crystallographic directions on the (001) and (111) planes at depths of cut of 100 nm and 1 ?m, and then the mechanism involved in ductile-regime turning was studied. Pitting damage occurred along certain specific crystallographic orientations. The crystallographic orientation dependence of the surface features also changed with the depth

Takayuki Shibata; Shigeru Fujii; Eiji Makino; Masayuki Ikeda

1996-01-01

329

Mixed valence of Sm on metal single-crystal surfaces  

SciTech Connect

Results of a photoemission study of Sm on a Cu(100) single crystal surface are reported. From the binding energy of the Sm 4f levels it is concluded that the mixed valence of Sm on Cu(100) is of a heterogeneous nature. It is suggested that this conclusion also applies to Al(111) and Al(100).

Andersen, J.N.; Chorkendorff, I.; Onsgaard, J.; Ghijsen, J.; Johnson, R.L.; Grey, F.

1988-03-15

330

Piezoelectric and Elastic Properties of Lithium Niobate Single Crystals  

Microsoft Academic Search

Piezoelectric and elastic constants of lithium niobate single crystal were measured in the temperature range between 20C and 200C. These constants were obtained by measuring the resonant and antiresonant frequencies of the length-extensional mode of bars with various orientations. The measured constants are all of the piezoelectric strain constants and the dielectric constants and a part of the elastic compliances,

Tomoaki Yamada; Nobukazu Niizeki; Hiroo Toyoda

1967-01-01

331

Phase Transition of Excited States of a Pyrene Single Crystal  

Microsoft Academic Search

Luminescence decay time and quantum yield of a pyrene single crystal are observed by a pulse method between 40-300 k. The temperature dependence on the intrinsic life time of emissions shows a peculiar character. The abrupt change of the analyzed intrinsic life time corresponds to the critical temperature of the phase transition. The mechanism of the phase transition is attributed

Masao Tomura; Tadaoki Mitani; Masaaki Tomura

1992-01-01

332

Growth of large single crystals of MgO.  

National Technical Information Service (NTIS)

The progressive identification of new high-technology applications and requirements for MgO single crystals in the commercial realm, as well as in DOE and other government-agency project areas, has resulted in an increased demand and international market ...

L. A. Boatner M. Urbanik

1997-01-01

333

Dielectric parameters of KDP single crystals added with urea  

Microsoft Academic Search

Potassium dihydrogen orthophosphate (KDP) having superior nonlinear optical properties has been exploited for variety of applications. We have grown KDP single crystals added with urea by the slow evaporation method from aqueous solutions. Dielectric measurements were carried out along both the unique axis and perpendicular directions at various temperatures ranging from 313 to 423K by the conventional parallel plate capacitor

S. Goma; C. M. Padma; C. K. Mahadevan

2006-01-01

334

MAGNETIZATION AND ELECTRICAL RESISTIVITY OF GADOLINIUM SINGLE CRYSTALS  

Microsoft Academic Search

The magnetic moment of single-crystal Gd was measured in fields from 0 ; to 18 kOe along the (0001), (1010), and (1120) directions at temperatures from ; 1.4 to 900 deg K. Small anisotropy was observed below the Curie temperature and ; the easy direction of magnetization was found to be a function of temperature. ; The absolute saturation magnetic

H. E. Nigh; S. Legvold; F. H. Spedding

1963-01-01

335

Alloy Design for Nickel-Base Super Alloy Single Crystals.  

National Technical Information Service (NTIS)

The purpose of this study is to develop high creep strength Nickel-base superalloys suitable for single crystal. A computer-aided alloy design system previously developed in NRIM is applied for this purpose. Ten alloys designed contained 5 - 10 Cr, 8 - 19...

T. Yamagata

1984-01-01

336

Anisotropy of Nickel-Base Superalloy Single Crystals.  

National Technical Information Service (NTIS)

The influence of orientation on the tensile and stress rupture behavior of 52 Mar-M247 single crystals was studied. Tensile tests were performed at temperatures between 23 and 1093 C; stress rupture behavior was examined between 760 and 1038 C. The mechan...

R. A. Mackay R. L. Dreshfield R. D. Maier

1980-01-01

337

Chromatography in a single metal-organic framework (MOF) crystal.  

PubMed

Millimeter-sized single MOF-5 crystals are used as "chromatographic columns" to effectively separate mixtures of organic dyes. Remarkably, owing to the nanoscopic pore dimensions and the molecular-level interactions between the migrating molecules and the MOF scaffold, the separations occur over a distance of only a few hundred micrometers which is unambiguously confirmed by fluorescence confocal microscopy. PMID:21038922

Han, Shuangbing; Wei, Yanhu; Valente, Cory; Lagzi, Istvn; Gassensmith, Jeremiah J; Coskun, Ali; Stoddart, J Fraser; Grzybowski, Bartosz A

2010-11-01

338

High definition TV projection via single crystal faceplate technology  

NASA Astrophysics Data System (ADS)

Single crystal phosphor faceplates are epitaxial phosphors grown on crystalline substrates with the advantages of high light output, resolution, and extended operational life. Single crystal phosphor faceplate industrial technology in the United States is capable of providing a faceplate appropriate to the projection industry of up to four (4) inches in diameter. Projection systems incorporating cathode ray tubes utilizing single crystal phosphor faceplates will produce 1500 lumens of white light with 1000 lines of resolution, non-interlaced. This 1500 lumen projection system will meet all of the currently specified luminance and resolution requirements of Visual Display systems for flight simulators. Significant logistic advantages accrue from the introduction of single crystal phosphor faceplate CRT's. Specifically, the full performance life of a CRT is expected to increase by a factor of five (5); ie, from 2000 to 10,000 hours of operation. There will be attendant reductions in maintenance time, spare CRT requirements, system down time, etc. The increased brightness of the projection system will allow use of lower gain, lower cost simulator screen material. Further, picture performance characteristics will be more balanced across the full simulator.

Kindl, H. J.; St. John, Thomas

1993-03-01

339

Grinding of Single-Crystal Silicon Using a Microvibration Device  

Microsoft Academic Search

This paper presents experimental results of grinding of single-crystal silicon using a microvibration device and a diamond grindingwheel. Samples were cut from (100) silicon. The grinding direction was parallel to the [110] direction of (100) silicon. These samples were ground under the same grinding conditions but with different vibration directions, frequencies, and\\/or amplitudes. The surface roughness and the surface texture

Z. W. Zhong; Z. Y. Rui

2005-01-01

340

Ultrabroadband single crystal composite transducers for underwater ultrasound  

Microsoft Academic Search

Through the use of complex piezoelectric structures, it is possible to obtain resonant harmonics not observed in the usual odd- harmonic response of a conventional structure. When combined with inherently broadband components, such as composites made with PMN- PT single crystal material, this permits the realisation of ultrabroadband devices. In the work reported here, results from modelling indicate that a

S. Cochran; M. Parker; P. Marin-Franch

2005-01-01

341

Transient Oxidation of Single Crystal NiAl+Zr.  

National Technical Information Service (NTIS)

The 800 C oxidation of oriented single crystals of Zr doped beta-NiAl was studied using transmission electron microscopy. The oxide phases and metal-oxide orientation relationships were determined to characterize the transient stages of oxidation prior to...

J. K. Doychak

1983-01-01

342

Dissipation in an ultrathin superconducting single-crystal Pb nanobridge  

Microsoft Academic Search

The transport property of a superconducting Pb nanobridge, which is carved by focus ion beam technique from an atomically flat single-crystal Pb thin film grown on Si(111) substrate, is investigated. Below the superconducting transition temperature TC, the nanobridge exhibits a series of sharp voltage steps as a function of current. The multiple voltage steps are interpreted as a consequence of

Jian Wang; Xu-Cun Ma; Yun Qi; Shuai-Hua Ji; Ying-Shuang Fu; Li Lu; Ai-Zi Jin; Chang-Zhi Gu; X. C. Xie; Ming-Liang Tian; Jin-Feng Jia; Qi-Kun Xue

2009-01-01

343

Magnetic Properties of Lattice Imperfections in Alkali Halide Single Crystals  

Microsoft Academic Search

Using a torque magnetometer, experimental results are reported on some new magnetic properties in high-purity, optical-quality single crystals of lithium fluoride, potassium chloride, and sodium chloride. Since the torque observations are not produced by the gross diamagnetism of these salts, the magnetic centers may be along dislocations because the magnetic susceptibility is observed to possess uniaxial anisotropy. Soft x irradiation

T. W. Adair; E. J. Sharp; C. F. Squire

1966-01-01

344

Deformation behaviour of aluminium single crystals in ultraprecision diamond turning  

Microsoft Academic Search

The physical properties of the machined layer of single crystal aluminium after diamond turning were assessed by X-ray diffraction (XRD) to demonstrate the nature and extent of the plastic deformation process that had occurred in the workpiece. In the range of depth of cut investigated, the microstrain was found to vary with the crystallography of the machined surface, whereas the

S. To; W. B. Lee

2001-01-01

345

Growth of large single crystals of MgO  

SciTech Connect

The progressive identification of new high-technology applications and requirements for MgO single crystals in the commercial realm, as well as in DOE and other government-agency project areas, has resulted in an increased demand and international market for this material. Specifically, the demand for MgO crystals in large sizes and quantities is presently increasing due to existing and developing applications that include: (a) MgO substrates for the formation of electro-optic thin films and devices, (b) epitaxial substrates for high-temperature thin-film superconducting devices MgO optical components - including high-temperature windows, lenses, and prisms, and (d) specialty MgO crucibles and evaporation sources for thin-film production. In the course of CRADA ORNL92-0091, carried out with Commercial Crystal Laboratories of Naples, Florida as the commercial participant, we have made major progress in increasing the size of single crystals of MgO produced by means of the submerged-arc-fusion technique-thereby increasing the commercial utility of this material. Prior to the accomplishments realized in the course of this CRADA, the only commercially available single crystals of MgO were produced in Japan, Israel, and Russia. The results achieved in the course of CRADA ORNL92-0091 have now led to the establishment of a domestic commercial source of MgO single-crystal substrates and components, and the U.S. is no longer totally dependent on foreign sources of this increasingly important material.

Boatner, L.A. [Oak Ridge National Lab., TN (United States); Urbanik, M. [Commercial Crystal Laboratories, Inc., Naples, FL (United States)

1997-06-12

346

Electronic states of pyrene single crystal and of its single molecule inserted in a molecular vessel of cyclodextrin  

NASA Astrophysics Data System (ADS)

Highly purified single crystals of pyrene were made by a gas phase crystal growth method from 180 times of zone-refined pyrene. The absorption spectra of the single crystal have been transformed from the reflection spectra between 2.5 and 6.5eV at 2, 77K and room temperature. The dry powder of ?-cyclodextrin including pyrene single molecule were prepared in vacuum to investigate the electronic states of the isolated molecule. The absorption spectra of the single molecule show similar spectra to those of the single crystal. The pyrene molecule keeps its electronic character even in the single crystal.

Takahashi, Nobuaki; Gombojav, Bold; Yoshinari, Takehisa; Nagasaka, Shin-Ichiro; Takahashi, Yoshio; Yamamoto, Aishi; Goto, Takenari; Kasuya, Atsuo

2004-10-01

347

Integration of ZnO microcrystals with tailored dimensions forming light emitting diodes and UV photovoltaic cells.  

PubMed

This article reports a new integration approach to produce arrays of ZnO microcrystals for optoelectronic and photovoltaic applications. Demonstrated applications are n-ZnO/p-GaN heterojunction LEDs and photovoltaic cells. The integration process uses an oxygen plasma treatment in combination with a photoresist pattern on magnesium doped GaN substrates to define a narrow sub-100 nm width nucleation region. Nucleation is followed by lateral epitaxial overgrowth producing single crystal disks of ZnO with desired size over 2 in. wafers. The process provides control over the dimensions (<1% STD) and the location (0.7% STD pitch variation) of the ZnO crystals. The quality of the patterned ZnO is high; the commonly observed defect related emission in the electroluminescence spectra is completely suppressed, and a single near-band-edge UV peak is observed. PMID:18407698

Cole, Jesse J; Wang, Xinyu; Knuesel, Robert J; Jacobs, Heiko O

2008-04-12

348

Single crystal-like Si patterns for photonic crystal color filters.  

PubMed

A novel fabrication method for a two-dimensional photonic crystal color filter based on guided mode resonance is proposed. An amorphous silicon layer deposited through the low-temperature plasma enhanced chemical vapor deposition (PECVD) process is patterned into two-dimensional structures using low-cost nanoimprint lithography. It is then effectively crystallized using multi-shot excimer laser annealing at low energy. We have demonstrated analytically and experimentally that single crystal-like silicon patterns on a glass substrate can offer high-efficiency photonic crystal color filters for reflective display applications. The highly crystallized silicon patterning scheme presented here may be very attractive for a variety of devices requiring high carrier mobility and high optical efficiency. PMID:21343641

Cho, Eun-Hyoung; Kim, Hae-Sung; Sohn, Jin-Seung; Moon, Chang-Youl; Park, No-Cheol; Park, Young-Pil

2011-02-22

349

Solid mechanics and material strength studies on the melt growth of bulk single crystals  

Microsoft Academic Search

Microdefects such as dislocations and macrocracking should be controlled during the crystal growth process to obtain high-quality bulk single crystals. Solid mechanics and material strength studies on the single crystals are of importance to solve the problems related to the generation and multiplication of dislocations and the cracking of single crystals. The present paper reviews such research activities that comprise

Noriyuki Miyazaki

2007-01-01

350

Method for Growing Large CdS and ZnS Single Crystals  

Microsoft Academic Search

A new technique for growing single crystals of CdS and ZnS has been devised in which single crystals up to 115 g in weight are obtained. The conversion of sphalerite into wurtzite and vice versa is described. The growth mechanism of the single ZnS crystals is described and compared with that for CdS crystals previously reported.

L. C. Greene; D. C. Reynolds; S. J. Czyzak; W. M. Baker

1958-01-01

351

GROWTH OF SINGLE CRYSTALS OF INCONGRUENTLY MELTING YTTRIUM IRON GARNET BY FLAME FUSION PROCESS  

Microsoft Academic Search

Single crystals of yttrium iron garnet (YFeO) were ; grown using the flame fusion process, even though the compcund is reported to ; melt incongruently. The growth of these single crystals involves a mechanism ; different from that which has been proposed for the growth of single crystals of ; incongruently melting mullite. Crystal boules were grown at varying linear

R. G. Rudness; R. W. Kebler

1960-01-01

352

Control of the doping concentration, morphology and optoelectronic properties of vertically aligned chlorine-doped ZnO nanowires  

Microsoft Academic Search

Vertically aligned single-crystal and chlorine-doped ZnO nanowires (NWs) were grown by a low-cost, high-yield and seed-free electrochemical route. The effects of the applied potential and the concentration of ammonium chloride (NH4Cl) on the morphology, structural and optoelectronic properties of the ZnO:Cl NWs were comprehensively investigated. The amount of Cl ions introduced in the ZnO structure increased almost linearly with both

Jiandong Fan; Alexey Shavel; Reza Zamani; Cristian Fbrega; Jean Rousset; Servane Haller; Frank Gell; Alex Carrete; Teresa Andreu; Jordi Arbiol; Joan Ramn Morante; Andreu Cabot

2011-01-01

353

MOVPE growth of transition-metal-doped GaN and ZnO for spintronic applications  

Microsoft Academic Search

This paper presents a comparative study on the effect of transition metal and rare-earth doping on GaN and ZnO by metal organic vapor phase epitaxy (MOVPE). Bulk ZnO single crystals were also analyzed in this study. Structural and optical characterization of these materials did not show the presence of any secondary phases or significant degradation of optical property. Magnetization measurements

S. Gupta; W. E. Fenwick; A. Melton; T. Zaidi; H. Yu; V. Rengarajan; J. Nause; A. Ougazzaden; I. T. Ferguson

2008-01-01

354

Dielectric constant measurements on lead azide single crystals  

NASA Astrophysics Data System (ADS)

The dielectric constants of lead azide in single crystal form were measured in the three crystallographic directions and found to be unusually large and highly anisotropic. The dielectric constants are fairly independent of temperature over the range of 100 K to 370 K and of frequency over the range of 100 to 1000 Hz. The dielectric constants of the azides of T1, Na, and K were also measured and compared to published values. Calculations taking into account the crystal structure of lead azide indicate that the observed anistropy arises from polarization of the azide molecules.

Garrett, W. L.; Kemmey, P. J.

1980-09-01

355

Submicrometer Single Crystal Diffractometry for Highly Accurate Structure Determination  

NASA Astrophysics Data System (ADS)

Submicrometer single crystal diffractometry for highly accurate structure determination was developed using the extremely stable and highly brilliant synchrotron radiation from SPring-8. This was achieved using a microbeam focusing system and the submicrometer precision low-eccentric goniometer system. We demonstrated the structure analyses with 222 ?m3 cytidine, 600600300 nm3 BaTiO3, and 111 ?m3 silicon. The observed structure factors of the silicon crystal were in agreement with the structure factors determined by the Pendellsung method and do not require absorption and extinction corrections.

Yasuda, Nobuhiro; Fukuyama, Yoshimitsu; Toriumi, Koshiro; Kimura, Shigeru; Takata, Masaki

2010-06-01

356

Flux Pinning and Scaling Behavior in La-214 Single Crystal.  

NASA Astrophysics Data System (ADS)

``Fishtails" in magnetic hysteresis loops (M vs. H) were observed in single crystals of La-214. The field at the peak position (H_peak(T)) can be described by a power-law relation. The reduce peak field vs. reduced temperature can be scaled into a single curve for all of La-214, Y-123, and Y-124 single crystals, indicating a similar pinning mechanism. The irreversibility line (H_irr(T)) in La-214 single crystal was measured by both M vs. H and M. vs. T methods. The power-law relation of H_irr(T) has the same functional form as H_peak(T) indicating the ratio of H_irr(T)/H_peak(T) is independent of temperature. * Ames Laboratory is operated for the U.S. Department of Energy by Iowa State University under Contract No. W-7405-ENG-82. The work at University of Chicago is partially supported by the NSF through the Science and Technology Center for Superconductivity under contract No. DMR 91-20000. The work at Argonne is supported by the U. S. DOE, Basic Energy Sciences-Materials Sciences, under Contract No. W-31-109-ENG-38.

Xu, Ming; Finnemore, D. K.; Zhang, K.; Mogilevsky, R.; Hinks, D. J.; Crabtree, G. W.

1996-03-01

357

Solvothermal crystal growth of functional materials  

Microsoft Academic Search

Hydrothermal crystal growth was associated with the development of ? -quartz single crystals for devices based on piezoelectric materials. This technology was then used to elaborate single crystals of different functional materials such as quartz-like oxides (AlPO4, GaPO4, GaAsO4, etc.), calcite CaCO3, etc. During the last few years two materials, GaN (using non-aqueous solvent) and ZnO, have been particularly investigated

Alain Largeteau; Stephane Darracq; Graziella Goglio; Gerard Demazeau

2008-01-01

358

Nucleation kinetics, growth and studies of ?-alanine single crystals.  

PubMed

Solubility and metastable zone width for the re-crystallized salt of ?-alanine was determined. Induction period measurement for the selected supersaturation ratios at room temperature (31 C) was carried out for supersaturated aqueous solutions of ?-alanine and it is noticed that induction period decreases with increase of supersaturation ratio. The nucleation parameters such as Gibbs free energy change, radius and number of molecules of the critical nucleus, interfacial tension and the nucleation rate have been evaluated by classical nucleation theory. Single crystals of ?-alanine were grown using the optimized nucleation parameters by solution method and grown crystals have been subjected to various studies like XRD studies, FTIR, optical, thermal and SHG studies. PMID:23548638

Shanthi, D; Selvarajan, P; HemaDurga, K K; Lincy Mary Ponmani, S

2013-03-04

359

AlSb single-crystal grown by HPBM  

NASA Astrophysics Data System (ADS)

Theoretical prognosis for AlSb places this widegap compound among the best materials for room temperature detectors and spectrometers. However, results experimentally obtained with AlSb are somewhat discouraging showing the necessity for improving the compound quality. The main difficulties connected with single-crystal growth are high reactivity of the melt with crucible material and a high volatility of Sb. In order to counteract the latter obstacle, an attempt was undertaken to synthesize and grow AlSb crystals by HPBM under the inert gas pressure of 40atm. Different crucible materials: aluminum oxide, vitreous carbon, quartz, graphite, beryllium oxide, and zirconium oxide were tested and their comparative analysis was made. The obtained crystals were investigated and some electrophysical properties measured.

Kutny, V. E.; Rybka, A. V.; Abyzov, A. S.; Davydov, L. N.; Komar, V. K.; Rowland, M. S.; Smith, C. F.

2001-02-01

360

Growth and spectral properties of Yb:FAP single crystal  

NASA Astrophysics Data System (ADS)

In this paper, single crystal of ytterbium (Yb) doped Ca5(PO4)3F (FAP) has been grown along the c-axis by using the Czochralski method. The segregation coefficients of Yb3+ in the Yb:FAP crystal has been determined by ICP-AES method. The absorption spectrum, fluorescence spectrum and fluorescence lifetime of the Yb:FAP crystal has been also measured at room temperature. In the absorption spectra, there are two absorption bands at 904 and 982 nm, respectively, which are suitable for InGaAs diode laser pumping. The absorption cross-section (?abs) is 5.117 10-20 cm2 with an FWHM of 4 nm at 982 nm. The emission cross-section (?em) is 3.678 10-20 cm2 at 1042 nm. Favorable values of the absorption cross-section at about 982 nm are promising candidates for laser diode (LD) pumping.

Song, Pingxin; Zhao, Zhiwei; Xu, Xiaodong; Deng, Peizhen; Xu, Jun

2007-01-01

361

Dislocations and Grain Boundaries in Semiconducting Rubrene Single-Crystals  

SciTech Connect

Assessing the fundamental limits of the charge carrier mobilities in organic semiconductors is important for the development of organic electronics. Although devices such as organic field effect transistors (OFETs), organic thin film transistors (OTFTs) and organic light emitting diodes (OLEDs) are already used in commercial applications, a complete understanding of the ultimate limitations of performance and stability in these devices is still lacking at this time. Crucial to the determination of electronic properties in organic semiconductors is the ability to grow ultra-pure, fully ordered molecular crystals for measurements of intrinsic charge transport. Likewise, sensitive tools are needed to evaluate crystalline quality. We present a high-resolution X-ray diffraction and X-ray topography analysis of single-crystals of rubrene that are of the quality being reported to show mobilities as high as amorphous silicon. We show that dislocations and grain boundaries, which may limit charge transfer, are prominent in these crystals.

Chapman,B.; Checco, A.; Pindak, R.; Siegrist, T.; Kloc, C.

2006-01-01

362

Crystal growth and luminescence properties of Cr-doped YAlO3 single crystals  

NASA Astrophysics Data System (ADS)

We have investigated optical and scintillation properties of Cr-doped YAlO3 (Cr:YAP) single crystals with different Cr concentrations. Cr:YAP crystals were grown by the micro-pulling-down (?-PD) method. The grown crystals had a single-phase confirmed by the powder XRD analysis. For all the Cr-doped samples, a peak positioned near 700 nm wavelength dominates the spectra. It can be ascribed to the Cr3+2E?4A2 emission. In X-ray induced radioluminescence spectra, 2E?4A2 emissions were observed. The light output of Cr 0.5%:YAP under X-ray excitation was more than twice as high as the standard CdWO4.

Sugiyama, Makoto; Yanagida, Takayuki; Totsuka, Daisuke; Yokota, Yuui; Futami, Yoshisuke; Fujimoto, Yutaka; Yoshikawa, Akira

2013-01-01

363

Growth and optical property of methyl para hydroxybenzoate sodium dihydrate single crystals  

NASA Astrophysics Data System (ADS)

Methyl parahydroxybenzoate sodium dihydrate (MHBN), a novel semiorganic single crystal has been grown by slow evaporation solution technique (SEST). Single crystal of MHBN with the size of 30 30 10 mm3 has been grown using methanol as a solvent. The crystal structure of MHBN has been confirmed by single crystal X-ray diffraction. The grown crystals were subjected to powder X-ray diffraction studies. The optical transparency was studied using UV-VIS spectrophotometer and it was found that the crystal is having good optical transparency. The mechanical strength of the grown crystal is measured using Vickers microhardness tester. Thermal properties of the MHBN crystals were studied.

Karunagaran, N.; Ramasamy, P.

2013-06-01

364

Mutiple Czochralski growth of silicon crystals from a single crucible  

NASA Astrophysics Data System (ADS)

An apparatus for the Czochralski growth of silicon crystals is presented which is capable of producing multiple ingots from a single crucible. The growth chamber features a refillable crucible with a water-cooled, vacuum-tight isolation valve located between the pull chamber and the growth furnace tank which allows the melt crucible to always be at vacuum or low argon pressure when retrieving crystal or introducing recharge polysilicon feed stock. The grower can thus be recharged to obtain 100 kg of silicon crystal ingots from one crucible, and may accommodate crucibles up to 35 cm in diameter. Evaluation of the impurity contents and I-V characteristics of solar cells fabricated from seven ingots grown from two crucibles reveals a small but consistent decrease in cell efficiency from 10.4% to 9.6% from the first to the fourth ingot made in a single run, which is explained by impurity build-up in the residual melt. The crystal grower thus may offer economic benefits through the extension of crucible lifetime and the reduction of furnace downtime.

Lane, R. L.; Kachare, A. H.

1980-10-01

365

Determining thermodynamic properties of molecular interactions from single crystal studies.  

PubMed

The concept of single crystals of macromolecules as thermodynamic systems is not a common one. However, it should be possible to derive thermodynamic properties from single crystal structures, if the process of crystallization follows thermodynamic rules. We review here an example of how the stabilizing potentials of molecular interactions can be measured from studying the properties of DNA crystals. In this example, we describe an assay based on the four-stranded DNA junction to determine the stabilizing potentials of halogen bonds, a class of electrostatic interactions, analogous to hydrogen bonds, that are becoming increasing recognized as important for conferring specificity in protein-ligand complexes. The system demonstrates how crystallographic studies, when coupled with calorimetric methods, allow the geometries at the atomic level to be directly correlated with the stabilizing energies of molecular interactions. The approach can be generally applied to study the effects of DNA sequence and modifications of the thermodynamic stability of the Holliday junction and, by inference, on recombination and recombination dependent processes. PMID:23933330

Vander Zanden, Crystal M; Carter, Megan; Ho, Pui Shing

2013-08-06

366

The influence of crystal orientations on fatigue life of single crystal cooled turbine blade  

Microsoft Academic Search

A method based on the orthotropic elastic finite element analysis (FEA) has been presented to analyze the fatigue life of cooled turbine blades made of nickel-based single crystal superalloy (SC). Special attention was put on the influence of the crystallographic orientations on the strength and fatigue life of SC cooled turbine blades. It is shown that, due to the influence

N. X. Hou; W. X. Gou; Z. X. Wen; Z. F. Yue

2008-01-01

367

Comprehensive Investigation of Single Crystal Diamond Deep-Ultraviolet Detectors  

NASA Astrophysics Data System (ADS)

The wide bandgap of diamond, along with its extreme semiconductor properties, offers the promising route for deep-ultraviolet (DUV) detection, especially under solar-blind condition and harsh environments. The ideal photodetector should generally satisfy the 5S requirements such as high sensitivity, high signal-to-noise ratio, high spectral selectivity, high speed, and high stability. In this paper, we comprehensively investigate the DUV detectors fabricated from various kinds of single crystal diamonds such as boron-doped diamond homoepitaxial layer, intrinsic diamond homoepitaxial layers with different thicknesses, and single crystal diamond substrates. The post process such as hydrogen plasma treatment on the performance of the DUV detectors is also examined. The strategies to develop high-performance diamond DUV detectors are provided.

Liao, Meiyong; Sang, Liwen; Teraji, Tokuyuku; Imura, Masataka; Alvarez, Jose; Koide, Yasuo

2012-09-01

368

Properties of salt-grown uranium single crystals.  

SciTech Connect

Recently single crystals of {alpha}-uranium were grown from a liquid salt bath. The electrical, magnetic and thermal properties of these crystals have been surveyed. The ratio of the room temperature resistivity of these crystals to the saturation value at low temperature is three times larger than any previously reported demonstrating that the crystals are of higher purity and quality than those in past work. The resistive signatures of the CDW transitions at 43, 37 and 22 K are obvious to the naked eye. The transition at 22 K exhibits temperature hysteresis that increases with magnetic field. In addition the superconducting transition temperature from resistivity is 820 mK and the critical field is 80 mT. Contrary to earlier work where the Debye temperature ranged from 186 to 218 K, the Debye temperature extracted from the heat capacity is 254 K in good agreement with the predicted value of 250 K. Magnetoresistance, Hall effect and magnetic susceptibility measurements are underway. In time, measurements made on these crystals may help us to understand the origin of superconductivity and its relation to the CDW transitions in pure uranium.

Cooley, J. C. (Jason C.); Hanrahan, R. J. (Robert J.); Hults, W. L. (William L.); Lashley, J. C. (Jason C.); Manley, M. E. (Michael E.); Mielke, C. H. (Charles H.); Smith, J. L. (James L.); Thoma, D. J. (Dan J.); Clark, R. G. (Robert G.); Hamilton, A. R.; O'Brien, J. L. (Jeremy L.); Gay, E. C. (Eddie C.); Lumpkin, N. E.; McPheeters, C. C. (Charles C.); Willit, J.; Schmiedeshoff, G. M. (George M.); Touton, S. (Sharon); Woodfield, B. F. (Brian F.); Lang, B. E. (Brian E.); Boerio-Goates, Juliana

2001-01-01

369

Simulation of Sublimation Growth of SiC Single Crystals  

NASA Astrophysics Data System (ADS)

Modelling of sublimation growth of SiC is discussed with the goal to describe the mathematical models necessary to optimize the process and design of the growth system. An analysis of the mechanisms of growth of bulk silicon carbide crystals is performed. Growth conditions which provide stable growth of single SiC crystals without formation of secondary phases are considered. The phase diagram of the formation of extra phases during the sublimation growth of SiC is presented. Modelling of the growth of bulk SiC crystals is considered. Results of modelling the temperature distribution inside the inductively heated system for the growth of bulk SiC crystals are shown. A mechanism of material transport inside the closed Ta container in the absence of an inert gas atmosphere is proposed which is different from that of diffusive or free-molecular transport. First results of the model analysis of chemical processes inside the volume of SiC powder during the sublimation growth are demonstrated. It is shown that the sublimation and re-crystallization of the SiC source is sensitive to the temperature distribution in the source.

Karpov, S. Yu.; Makarov, Yu. N.; Ramm, M. S.

1997-07-01

370

Single crystals of V amylose complexed with glycerol.  

PubMed

Lamellar single crystals of amylose V glycerol were grown at 100 degrees C by evaporating water from solutions of amylose in aqueous glycerol. The crystals which were square, with lateral dimensions of several micrometers, gave sharp electron diffraction patterns presenting an orthorhombic symmetry with a probable space group P2(1)2(1)2(1) and unit cell parameters: a = 1.93 +/- 0.01 nm, b = 1.86 +/- 0.01 nm and c (fiber axis) = 0.83 +/- 0.03 nm. The amylose Vglycerol crystal structure which is isomorphous to that of VDMSO consists of an antiparallel pair of left-handed six-fold amylose helices centered on the two-fold screw axes of the cell and probably separated by glycerol molecules. This packing mode is confirmed by de-solvation experiments where the Vglycerol amylose crystals, annealed in ethanol, could be converted into VH amylose without losing their external appearance. The Vglycerol amylose crystals could be seeded by cellulose microfibrils to yield a shish-kebab structure where the amylose crystalline lamellae grew perpendicular to the microfibril directions. PMID:8852760

Hulleman, S H; Helbert, W; Chanzy, H

1996-02-01

371

Crystal growth of high-quality ZrB 2 single crystals using the floating-zone method  

Microsoft Academic Search

High-quality ZrB2 single crystals with diameters of 13mm and lengths of 45mm were grown from boron-rich molten zones (boron 80mol%), using the RF heated floating-zone method. The (0001) single crystals were also grown using seed crystals. Control of temperature gradients on the growing interfaces was performed by arranging ceramic cylinders around the growing crystals and the feed rods. This made

Kenji Hori; Shinji Inoue; Mineo Isogami

2008-01-01

372

Application of GRID to foreign atom localization in single crystals  

SciTech Connect

The application of GRID (Gamma Ray Induced Doppler broadening) spectroscopy to the localization of foreign atoms in single crystals is demonstrated on erbium in YAP. By the investigation of the Doppler broadened secondary {gamma} line for two crystalline directions, the Er was determined to be localized on the Y site. Conditions for the nuclear parameters of the impurity atoms used for the application of GRID spectroscopy are discussed.

Karmann, A.; Wesch, W.; Weber, B.; Boerner, H.G.; Jentschel, M.

2000-02-01

373

Electron spectroscopy of single crystal and polycrystalline cerium oxide surfaces  

Microsoft Academic Search

Valence band photoemission (XPS), valence band electron energy loss spectroscopy (EELS), Ce3d and 4d XPS, O1s XPS and O1s X-ray absorption (XAS) have been investigated for oxidized and sputtered single crystal CeO2 films and for oxidized Ce foil. Features were identified that distinguish between the Ce4+ or Ce3+ oxidation states. Ce4+ was identified by the highest binding energy peaks in

D. R Mullins; S. H Overbury; D. R Huntley

1998-01-01

374

Controlled synthesis of gold nanospheres and single crystals in hydrogel  

Microsoft Academic Search

Narrow-dispersed gold nanospheres, regular single-crystal nanoplates and nanobulks were prepared, respectively, by reducing\\u000a HAuCl4 within a hydrogel system under UV irradiation. The formation of gold products with different geometric shape and size was\\u000a found to depend on both the microenvironment of the gel matrix and the initial concentration of HAuCl4. The resultant gold particles were investigated by UVvis spectroscopy, X-ray

Jian Zhang; Baohui Zhao; Linghui Meng; Hongying Wu; Xudong Wang; Chenxi Li

2007-01-01

375

Mechanisms for tertiary creep of single crystal superalloy  

Microsoft Academic Search

During the thermal-mechanical loading of high temperature single crystal turbine components, all three creepstages: primary,\\u000a secondary and tertiary, manifest themselves and, hence, none of them can be neglected. The development of a creep law that\\u000a includes all three stages is especially important in the case of non-homogeneous thermal loading of the component where significant\\u000a stress redistribution and relaxation will result.

Alexander Staroselsky; Brice Cassenti

2008-01-01

376

Fabrication of single crystal PZT thin films on glass substrates  

Microsoft Academic Search

We have successfully transferred heteroepitaxial Pb(Zr,Ti)O3 (PZT) thin films from MgO substrates on to glass substrates. The transferred PZT thin films exhibit single crystal structure with ferroelectric properties similar to the as-grown epitaxial films. The transferring process comprises coating of Cr-metallized surface of epitaxial PZT thin films, pressing and cementing the Cr-metallized surface on to the glass substrates by silicone

Kenichiro Terada; Takaaki Suzuki; Isaku Kanno; Hidetoshi Kotera

2007-01-01

377

High temperature deformation properties of nial single crystals  

Microsoft Academic Search

The high-temperature deformation properties of stoichiometric NiAl single crystals have been studied in the temperature range\\u000a from 850 C and 1200 C. We have established a basic data set for and have explored the high-temperature deformation characteristics\\u000a of this intermetallic compound. The results provide a basis for determining the controlling mechanisms of high-temperature\\u000a deformation. Constant stress tension creep and constant

K. R. Forbes; U. Glatzel; R. Darolia; W. D. Nix

1996-01-01

378

High temperature deformation properties of nial single crystals  

Microsoft Academic Search

The high-temperature deformation properties of stoichiometric NiAl single crystals have been studied in the temperature range from 850 C and 1200 C. We have established a basic data set for and have explored the high-temperature deformation characteristics of this intermetallic compound. The results provide a basis for determining the controlling mechanisms of high-temperature deformation. Constant stress tension creep and constant

K. R. Forbes; U. Glatzel; R. Darolia; W. D. Nix

1996-01-01

379

Acoustic characteristics of FeSe single crystals  

NASA Astrophysics Data System (ADS)

The results of the comprehensive ultrasonic research of high-quality single crystals of FeSe are presented. Absolute values of sound velocities and their temperature dependences were measured; elastic constants and Debye temperature were calculated. The elastic C11-C12 and C11 constants undergo significant softening under the structural tetra-ortho transformation. The significant influence of the superconducting transition on the velocity and attenuation of sound was revealed and the value of the superconducting energy gap was estimated.

Zvyagina, G. A.; Gaydamak, T. N.; Zhekov, K. R.; Bilich, I. V.; Fil, V. D.; Chareev, D. A.; Vasiliev, A. N.

2013-03-01

380

Faraday rotation in single-crystal ytterbium gallium garnet  

Microsoft Academic Search

Faraday rotation (FR) measurements performed on single-crystal ytterbium gallium garnet (YbGG) at 0.6328- and 1.15-?m wavelengths are presented in a magnetic field up to 20 kOe applied along the three main crystallographic directions and in the 6300 K temperature range. At 0.6328 ?m, the FR is proportional to the magnetic field and a strong anisotropy of the Verdet constant (V)

M. Guillot; H. Le Gall; J. Ostorero; M. Artinian; A. Marchand

1987-01-01

381

Converting Ceria Polyhedral Nanoparticles into Single-Crystal Nanospheres  

Microsoft Academic Search

Ceria nanoparticles are one of the key abrasive materials for chemical-mechanical planarization of advanced integrated circuits. However, ceria nanoparticles synthesized by existing techniques are irregularly faceted, and they scratch the silicon wafers and increase defect concentrations. We developed an approach for large-scale synthesis of single-crystal ceria nanospheres that can reduce the polishing defects by 80% and increase the silica removal

Xiangdong Feng; Dean C. Sayle; Zhong Lin Wang; M. Sharon Paras; Brian Santora; Anthony C. Sutorik; Thi X. T. Sayle; Yi Yang; Yong Ding; Xudong Wang; Yie-Shein Her

2006-01-01

382

Nonpercolative metal-insulator transition in VO2 single crystals  

Microsoft Academic Search

Detailed temperature-dependent transport, optical microscopy, and synchrotron-based polychromatic x-ray microdiffraction measurements have been carried out in the vicinity of the metal-insulator transition (MIT) temperature of VO2 single crystals. The formation and propagation of a real-space phase boundary along the rutile c axis is monitored during the transition. Pure metallic rutile R, as well as insulating monoclinic M1 phases, is observed

Bongjin Simon Mun; Kai Chen; Joonseok Yoon; Catherine Dejoie; Nobumichi Tamura; Martin Kunz; Zhi Liu; Michael E. Grass; Sung-Kwan Mo; Changwoo Park; Y. Yvette Lee; Honglyoul Ju

2011-01-01

383

Single Crystal Diamond Beam Position Monitors with Radiofrequency Electronic Readout  

Microsoft Academic Search

Over the energy range 5~30 keV a suitably contacted, thin (~100 mum) diamond plate can be operated in situ as a continuous monitor of X-ray beam intensity and position as the diamond absorbs only a small percentage of the incident beam. Single crystal diamond is a completely homogeneous material showing fast (ns), spatially uniform signal response and negligible (

B. Solar; H. Graafsma; J. Morse; M. Salom; G. Potdevin; U. Trunk

2010-01-01

384

Elastic and Piezoelectric Coefficients of Single-Crystal Barium Titanate  

Microsoft Academic Search

Mechanical resonance and antiresonance frequencies were measured on barium titanate single-crystal elements maintained under electric dc bias from -50C to +150C. A complete set of elastic, piezoelectric, and dielectric constants of the tetragonal modification at 25C is obtained. The elastic compliances show substantial deviation from cubic symmetry. Measurements in the orthorhombic state show longitudinal compliance four times higher than in

Don Berlincourt; Hans Jaffe

1958-01-01

385

Ductile Mode Cuttingof Single-crystal Silicon by Ultrasonic Vibration  

Microsoft Academic Search

Brittle materials have a critical depth of cut between ductile mode and brittle mode In order to increase the critical depth\\u000a of cut, ductile mode cutting of single crystal silicon was realized using ultrasonic vibration. It was clarified that during\\u000a conventional cutting without ultrasonic vibration, the critical depth of cut was dc = 0.15?m. however, during ultrasonic vibration cutting, the

Shigeomi Koshimizu; Jiro Otsuka

386

Synthesis of mesoporous zeolite single crystals with cheap porogens  

Microsoft Academic Search

Mesoporous zeolite (silicalite-1, ZSM-5, TS-1) single crystals have been successfully synthesized by adding soluble starch or sodium carboxymethyl cellulose (CMC) to a conventional zeolite synthesis system. The obtained samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen sorption analysis, 27Al magic angle spinning nuclear magnetic resonance (27Al MAS

Haixiang Tao; Changlin Li; Jiawen Ren; Yanqin Wang; Guanzhong Lu

2011-01-01

387

The fatigue of pseudoelastic single crystals of ?-CuAINi  

Microsoft Academic Search

The fatigue life of single crystal ?-CuAINi has been studied on pseudoelastic cyclic loading. In general the fatigue life\\u000a was quite poor with most specimens having less than 3000 cycles to failure. The fatigue life decreased significantly with\\u000a increasing stress level. However, the fatigue failure was due primarily to stress-induced martensite formation, since if the\\u000a stress level on cycling was

L. C. Brown

1979-01-01

388

Anisotropic Linear Compressibilities of MnP Single Crystal  

Microsoft Academic Search

An attempt to measure the linear compressibilities of an MnP single crystal has been made under hydrostatic pressures by means of the paper strain gauge technique, in the range from -70 to 32C including the Curie temperature. Anomalous linear compressibilities are found near the Curie temperature, which are a lambda-type peak along c axis and the lambda-type dips along a

Nobuo Iwata; Tetsuhiko Okamoto

1975-01-01

389

Defects in GaN single crystals and homoepitaxial structures  

Microsoft Academic Search

In this communication crystallographic and chemical inhomogeneities occurring in GaN single crystals, homo-epitaxial layers and quasi-bulk thick epitaxial layers are described. Practical classification of defects as (i) growth-related and (ii) processing-induced is given. On the basis of numerous studies using different examination techniques (DIC and DF optical microscopy, SEM) and methods of revealing (defect-selective etching, PEC etching, X-ray diffraction and

J. L. Weyher; G. Kamler; G. Nowak; J. Borysiuk; B. Lucznik; M. Krysko; I. Grzegory; S. Porowski

2005-01-01

390

The Herbertsmithite Hamiltonian: ?SR measurements on single crystals  

NASA Astrophysics Data System (ADS)

We present transverse field muon spin rotation/relaxation measurements on single crystals of the spin-1/2 kagome antiferromagnet Herbertsmithite. We find that the spins are more easily polarized when the field is perpendicular to the kagome plane. We demonstrate that the difference in magnetization between the different directions cannot be accounted for by Dzyaloshinskii-Moriya-type interactions alone and that anisotropic axial interaction is present.

Ofer, Oren; Keren, Amit; Brewer, Jess H.; Han, Tianheng H.; Lee, Young S.

2011-04-01

391

Nonlinear limits for single-crystal silicon microresonators  

Microsoft Academic Search

Nonlinear effects in single-crystal silicon microresonators are analyzed with the focus on mechanical nonlinearities. The bulk acoustic wave (BAW) resonators are shown to have orders-of-magnitude higher energy storage capability than flexural beam resonators. The bifurcation point for the silicon BAW resonators is measured and the maximum vibration amplitude is shown to approach the intrinsic material limit. The importance of nonlinearities

Ville Kaajakari; Tomi Mattila; Aarne Oja; Heikki Sepp

2004-01-01

392

Peculiarities of vibrating Bi 2212 single crystal near Hc1  

Microsoft Academic Search

Vibrating reed experiment with a Bi-based superconducting single crystal were performed for perpendicular orientation of its ab-plane with respect to the applied magnetic field Ba. The temperature behaviour of frequency shift Delta? and damping D(T) of such mechanical oscillator were measured in the applied magnetic field Ba region 400-600 Oe which is close to the first critical value of the

A. V. Drobinin; K. E. Kamentsev; Yu. M. Tsipenyuk

1994-01-01

393

Depressed scattering across grain boundaries in single crystal graphene  

NASA Astrophysics Data System (ADS)

We investigated the electrical and quantum properties of single-crystal graphene (SCG) synthesized by chemical vapor deposition (CVD). Quantum Hall effect and Shubnikov de Hass oscillation, a distinguishing feature of a 2-dimensional electronic material system, were observed during the low temperature transport measurements. Decreased scattering from grain boundaries in SCG was proven through extracting information from weak localization theory. Our results facilitate understanding the electrical properties of SCG grown by CVD and its applications in high speed transistor and quantum devices.

Chen, Jiao; Jin, Zhi; Ma, Peng; Wang, Hong; Wang, Haomin; Shi, Jingyuan; Peng, Songang; Liu, Xinyu; Ye, Tianchun

2012-10-01

394

The dissolution forms of YIG single crystal spheres  

NASA Astrophysics Data System (ADS)

Single crystal spheres of yttrium iron garnet have been dissolved in solvents of H3PO4 and HBr at 140 and 126C, respectively. The final dissolution form was a tetrahexahedron in H3PO4 and an octahedron in HBr. In the latter case the faces were built up of terraces. The observed dissolution forms could be explained using the theory of Lacmann, Franke and Heimann.

Beregi, E.; Sterk, E.; Tanos, F.; Hartmann, E.; Lbr, J.

1983-12-01

395

The Temperature of a Single Crystal Diamond Tool in Turning  

Microsoft Academic Search

The temperature on the rake face of a single crystal diamond tool in precision turning is investigated experimentally and theoretically. The infrared rays radiated from the contact area between the chip and rake face, and transmitted through the diamond tool, are accepted by a chalcogenide fiber and led to a two-color detector which consists of InSb and HgCdTe detectors. The

Takashi Ueda; Masahiko Sato; Kazuo Nakayama

1998-01-01

396

Development of low density single crystal superalloy CMSX-6  

Microsoft Academic Search

Limitations in turbine disc strength capability can, in certain design cases, mandate the use of low density single crystal superalloy turbine blade components. The development of CMSX-6 nickel-base superalloy (density 0.288 lbs\\/cu. in. (7.98 gms.\\/cc)) to meet these design requirements is presented and discussed. Extensive solution treatment studies are shown and enable the high γ\\/γ eutectic content of the as-cast

K. Harris; G. L. Erickson; J. Wortmann; D. Froschhammer

2008-01-01

397

Fatigue strength of a single crystal in the gigacycle regime  

Microsoft Academic Search

The objective of this work is to investigate the fatigue behavior of a single crystal nickel-based superalloy in the gigacycle regime. Testing from 106 to 109 cycles at 593C was performed using an ultrasonic fatigue system operating at 20kHz. Multiple tests were performed at stresses near the fatigue limit to determine the variability in fatigue life in this regime. Endurance

Ryan J. Morrissey; Patrick J. Golden

2007-01-01

398

Superconducting microstrip resonator with yttrium iron garnet single crystals  

Microsoft Academic Search

A magnetically tunable microstrip superconducting resonator using an yttrium-iron-garnet (YIG) single crystal was demonstrated experimentally. Tunability of 200 MHz at a center frequency of 5.3 GHz was observed, and a quality factor of 965 with minimum insertion loss of 19.5 dB was measured for a half-wavelength microstrip line consisting of a YIG-YBCO-MgO composite structure. The dispersion relation of the resonator

Takeshi Fukusako; Makoto Tsutsumi

1997-01-01

399

FERROMAGNETIC RESONANCE LINE WIDTH IN YTTRIUM IRON GARNET SINGLE CRYSTALS  

Microsoft Academic Search

A study of ferromagnetic resonance line width in polished, single-; crystal spheres of yttriunn iron garnet is described. Wave-guide cavity ; perturbation techniques are used with samples 0.013 in. to 0.020 in. in diameter. ; An extremely narrow line width of 520 millioersteds (the full width) is observed ; at 9300 Mc\\/sec along the hard axis STA100!. It is believed

R. C. LeCraw; E. G. Spencer; C. S. Porter

1958-01-01

400

Method for thermal processing alumina-enriched spinel single crystals  

DOEpatents

A process for age-hardening alumina-rich magnesium aluminum spinel to obtain the desired combination of characteristics of hardness, clarity, flexural strength and toughness comprises selection of the time-temperature pair for isothermal heating followed by quenching. The time-temperature pair is selected from the region wherein the precipitate groups have the characteristics sought. The single crystal spinel is isothermally heated and will, if heated long enough pass from its single phase through two pre-precipitates and two metastable precipitates to a stable secondary phase precipitate within the spinel matrix. Quenching is done slowly at first to avoid thermal shock, then rapidly. 12 figs.

Jantzen, C.M.

1995-05-09

401

A simple route to vertical array of quasi-1D ZnO nanofilms on FTO surfaces: 1D-crystal growth of nanoseeds under ammonia-assisted hydrolysis process  

PubMed Central

A simple method for the synthesis of ZnO nanofilms composed of vertical array of quasi-1D ZnO nanostructures (quasi-NRs) on the surface was demonstrated via a 1D crystal growth of the attached nanoseeds under a rapid hydrolysis process of zinc salts in the presence of ammonia at room temperature. In a typical procedure, by simply controlling the concentration of zinc acetate and ammonia in the reaction, a high density of vertically oriented nanorod-like morphology could be successfully obtained in a relatively short growth period (approximately 4 to 5 min) and at a room-temperature process. The average diameter and the length of the nanostructures are approximately 30 and 110 nm, respectively. The as-prepared quasi-NRs products were pure ZnO phase in nature without the presence of any zinc complexes as confirmed by the XRD characterisation. Room-temperature optical absorption spectroscopy exhibits the presence of two separate excitonic characters inferring that the as-prepared ZnO quasi-NRs are high-crystallinity properties in nature. The mechanism of growth for the ZnO quasi-NRs will be proposed. Due to their simplicity, the method should become a potential alternative for a rapid and cost-effective preparation of high-quality ZnO quasi-NRs nanofilms for use in photovoltaic or photocatalytics applications. PACS: 81.07.Bc; 81.16.-c; 81.07.Gf.

2011-01-01

402

SINGLE-CRYSTAL SAPPHIRE OPTICAL FIBER SENSOR INSTRUMENTATION  

SciTech Connect

In this research program, several optical instruments for high temperature measurement based on single crystal sapphire material are introduced and tested for real-time, reliable, long-term monitoring of temperatures for coal gasifier. These are sapphire fiber extrinsic Fabry-Perot interferometric (EFPI) sensor; intensity-measurement based polarimetric sapphire sensor and broadband polarimetric differential interferometric (BPDI) sapphire sensor. Based on current evaluation and analysis of the experimental results, the broadband polarimetric differential interferometric (BPDI) sensor system was chosen for further prototype instrumentation development. This approach is based on the self-calibrating measurement of optical path differences (OPD) in a single-crystal sapphire disk, which is a function of both the temperature dependent birefringence and the temperature dependent dimensional changes. The BPDI sensor system extracts absolute temperature information by absolute measurement of phase delays. By encoding temperature information in optical spectrum instead of optical intensity, this sensor guarantees its relative immunity to optical source power fluctuations and fiber losses, thus providing a high degree of long-term measurement stability which is highly desired in industrial applications. The entire prototype for BPDI system including the single crystal sapphire probe, zirconia prism, alumina extension tube, optical components and signal processing hardware and software have shown excellent performance in the laboratory experiments shown in this report.

A. Wang; G. Pickrell; R. May

2002-09-10

403

Single crystal plasticity by modeling dislocation density rate behavior  

SciTech Connect

The goal of this work is to formulate a constitutive model for the deformation of metals over a wide range of strain rates. Damage and failure of materials frequently occurs at a variety of deformation rates within the same sample. The present state of the art in single crystal constitutive models relies on thermally-activated models which are believed to become less reliable for problems exceeding strain rates of 10{sup 4} s{sup -1}. This talk presents work in which we extend the applicability of the single crystal model to the strain rate region where dislocation drag is believed to dominate. The elastic model includes effects from volumetric change and pressure sensitive moduli. The plastic model transitions from the low-rate thermally-activated regime to the high-rate drag dominated regime. The direct use of dislocation density as a state parameter gives a measurable physical mechanism to strain hardening. Dislocation densities are separated according to type and given a systematic set of interactions rates adaptable by type. The form of the constitutive model is motivated by previously published dislocation dynamics work which articulated important behaviors unique to high-rate response in fcc systems. The proposed material model incorporates thermal coupling. The hardening model tracks the varying dislocation population with respect to each slip plane and computes the slip resistance based on those values. Comparisons can be made between the responses of single crystals and polycrystals at a variety of strain rates. The material model is fit to copper.

Hansen, Benjamin L [Los Alamos National Laboratory; Bronkhorst, Curt [Los Alamos National Laboratory; Beyerlein, Irene [Los Alamos National Laboratory; Cerreta, E. K. [Los Alamos National Laboratory; Dennis - Keller, D. [Los Alamos National Laboratory

2010-12-23

404

Chiral multichromic single crystals for optical devices (LDRD 99406).  

SciTech Connect

This report summarizes our findings during the study of a novel system that yields multi-colored materials as products. This system is quite unusual as it leads to multi-chromic behavior in single crystals, where one would expect that only a single color would exist. We have speculated that these novel solids might play a role in materials applications such as non-linear optics, liquid crystal displays, piezoelectric devices, and other similar applications. The system examined consisted of a main-group alkyl compound (a p block element such as gallium or aluminum) complexed with various organic di-imines. The di-imines had substituents of two types--either alkyl or aromatic groups attached to the nitrogen atoms. We observed that single crystals, characterized by X-ray crystallography, were obtained in most cases. Our research during January-July, 2006, was geared towards understanding the factors leading to the multi-chromic nature of the complexes. The main possibilities put forth initially considered (a) the chiral nature of the main group metal, (b) possible reduction of the metal to a lower-valent, radical state, (c) the nature of the ligand(s) attached to the main group metal, and (d) possible degradation products of the ligand leading to highly-colored products. The work carried out indicates that the most likely explanation considered involves degradation of the aromatic ligands (a combination of (c) and (d)), as the experiments performed can clearly rule out (a) and (b).

Kemp, Richard Alan; Felix, Ana M. (University of New Mexico, Albuquerque, NM)

2006-12-01

405

Performance of Large grain and Single Crystal Niobium Cavities  

SciTech Connect

We have fabricated and tested several single and one multi-cell cavity made from large grain niobium of four different ingots. Two cavities at a frequency of ~ 2.2 GHz were made from single crystal sheets. Large grain material was used for four single cell cavities of the HG and OC shapes, a 7-cell cavity of the HG shape all resonating at 1500 MHz and an ILC_LL single cell cavity at 1300 MHz. We began to explore also different chemical polishing baths such as a 1:1:1 and a 1:1:2 buffered solution and explored the change of cavity performance as a function of material removal. The results from these preliminary investigations are reported in this contribution.

Kneisel, Peter; Ciovati, Gianluigi; Sekutowicz, Jacek

2006-07-01

406

Effect of organic dopants on ZTS single crystals  

NASA Astrophysics Data System (ADS)

The influence of organic dopants on tristhioureazinc(II)sulphate (ZTS) single crystals from aqueous solutions at 30 C is investigated. The dopants used in the present investigation are disodium salt of ethylenediamminetetraacetic acid (EDTA), benzene and 1,10-phenanthroline (Phen) which are having different structures. Though, all the dopants show better results, prominent influence is observed in case of EDTA dopant with low concentration of 510-3 M L-1 and hence the results pertaining to EDTA dopant are described in detail in the present article. At low concentrations of dopant, an increase in the metastable zone width, leading to an increase in the crystal growth rate is observed. At higher dopant concentration, growth rate decreases. The crystalline perfection of the grown crystals has been evaluated by high-resolution X-ray diffractometry (HRXRD). The diffraction curve (DC) of a typical EDTA-doped as-grown ZTS crystal was observed to contain one additional peak very close to the main peak suggesting the possibility of an epitaxial layer on the surface of the crystal. After removing this layer by lapping followed by chemical etching, the DC was found to contain only a single and very sharp peak showing that the main crystal is having a much better crystalline perfection than that observed for the specimen grown with out using any dopant in the solution. This indicates that the complexation of trace metal ion impurities (present in the solution) with the dopants is responsible for the formation of the layer on the surface of the crystal and prevents the entry of impurities in the growing crystal. The complexation also promotes the growth process leading to a rapid growth with high crystalline quality. Not much variation is observed in FT-IR and XRD of pure and doped ZTS. However, second harmonic generation (SHG) efficiency measurements carried out with different dopants reveal that nonlinear optical (NLO) property is enhanced by EDTA and benzene dopants. However, Phen depresses the NLO efficiency of ZTS.

Meenakshisundaram, Subbiah; Parthiban, S.; Sarathi, N.; Kalavathy, R.; Bhagavannarayana, G.

2006-08-01

407

Growth of Sapphire Single Crystals Transparent Armor by a Modified Verneuil Technique.  

National Technical Information Service (NTIS)

The objective of the process development program was to determine whether it was feasible to produce slab shaped sapphire single crystals by a modified Verneuil technique for transparent armor applications. Seeded single crystals of sapphire were grown wi...

J. S. Haggerty M. Rossetti

1970-01-01

408

Anisotropic Piezocomposite Actuator Incorporating Machined PMN-PT Single Crystal Fibers.  

National Technical Information Service (NTIS)

The design, fabrication, and testing of a flexible, planar, anisotropic piezoelectric composite actuator utilizing machined PMN-32%PT single crystal fibers is presented. The device consists of a layer of rectangular single crystal piezoelectric fibers in ...

W. K. Wilkie D. J. Inman J. M. Lloyd J. W. High

2004-01-01

409

Atomic force microscopy of insulin single crystals: direct visualization of molecules and crystal growth.  

PubMed Central

Atomic force microscopy performed on single crystals of three different polymorphs of bovine insulin revealed molecularly smooth (001) layers separated by steps whose heights reflect the dimensions of a single insulin hexamer. Whereas contact mode imaging caused etching that prevented molecular-scale resolution, tapping mode imaging in solution provided molecular-scale contrast that enabled determination of lattice parameters and polymorph identification while simultaneously enabling real-time examination of growth modes and assessment of crystal quality. Crystallization proceeds layer by layer, a process in which the protein molecules assemble homoepitaxially with nearly perfect orientational and translational commensurism. Tapping mode imaging also revealed insulin aggregates attached to the (001) faces, their incorporation into growing terraces, and their role in defect formation. These observations demonstrate that tapping mode imaging is ideal for real-time in situ investigation of the crystallization of soft protein crystals of relatively small proteins such as insulin, which cannot withstand the lateral shear forces exerted by the scanning probe in conventional imaging modes. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4

Yip, C M; Ward, M D

1996-01-01

410

Computational Modeling of Photonic Crystal Microcavity Single-Photon Emitters  

NASA Astrophysics Data System (ADS)

Conventional cryptography is based on algorithms that are mathematically complex and difficult to solve, such as factoring large numbers. The advent of a quantum computer would render these schemes useless. As scientists work to develop a quantum computer, cryptographers are developing new schemes for unconditionally secure cryptography. Quantum key distribution has emerged as one of the potential replacements of classical cryptography. It relics on the fact that measurement of a quantum bit changes the state of the bit and undetected eavesdropping is impossible. Single polarized photons can be used as the quantum bits, such that a quantum system would in some ways mirror the classical communication scheme. The quantum key distribution system would include components that create, transmit and detect single polarized photons. The focus of this work is on the development of an efficient single-photon source. This source is comprised of a single quantum dot inside of a photonic crystal microcavity. To better understand the physics behind the device, a computational model is developed. The model uses Finite-Difference Time-Domain methods to analyze the electromagnetic field distribution in photonic crystal microcavities. It uses an 8-band k p perturbation theory to compute the energy band structure of the epitaxially grown quantum dots. We discuss a method that combines the results of these two calculations for determining the spontaneous emission lifetime of a quantum dot in bulk material or in a microcavity. The computational models developed in this thesis are used to identify and characterize microcavities for potential use in a single-photon source. The computational tools developed are also used to investigate novel photonic crystal microcavities that incorporate 1D distributed Bragg reflectors for vertical confinement. It is found that the spontaneous emission enhancement in the quasi-3D cavities can be significantly greater than in traditional suspended slab cavities.

Saulnier, Nicole A.

411

Advanced piezoelectric single crystal based transducers for naval sonar applications  

NASA Astrophysics Data System (ADS)

Transducers incorporating single crystal piezoelectric Pb(Mg1/3Nb2/3)x-1TixO3 (PMN-PT) exhibit significant advantages over ceramic piezoelectrics such as PZT, including both high electromechanical coupling (k33 > 90%) and piezoelectric coefficients (d33 > 2000 pC/N). Conventional <001> orientation gives inherently larger bandwidth and output power than PZT ceramics, however, the anisotropy of the crystal also allows for tailoring of the performance by orienting the crystal along different crystallographic axes. This attribute combined with composition refinements can be used to improve thermal or mechanical stability, which is important in high power, high duty cycle sonar applications. By utilizing the "31" resonance mode, the high power performance of PMN-PT can be improved over traditional "33" mode single crystal transducers, due to an improved aspect ratio. Utilizing novel geometries, effective piezoelectric constants of -600 pC/N to -1200 pC/N have been measured. The phase transition point induced by temperature, pre-stress or field is close to that in the "33" mode, and since the prestress is applied perpendicular to the poling direction in "31" mode elements, they exhibit lower loss and can therefore be driven harder. The high power characteristics of tonpilz transducers can also be affected by the composition of the PMN-PT crystal. TRS modified the composition of PMN-PT to improve the thermal stability of the material, while keeping the loss as low as possible. Three dimensional modeling shows that the useable bandwidth of these novel compositions nearly equals that of conventional PMN-PT. A decrease in the source level of up to 6 dB was calculated, which can be compensated for by the higher drive voltages possible.

Snook, Kevin A.; Rehrig, Paul W.; Hackenberger, Wesley S.; Jiang, Xiaoning; Meyer, Richard J., Jr.; Markley, Douglas

2006-04-01

412

Technical Report of ISSP. Ser. A, No. 2677: Octa-Twin Model of Tetrapod ZnO Crystals.  

National Technical Information Service (NTIS)

The characteristic morphology of tetrapod-shaped ZnO particles grown by oxidizing zinc vapor in air has been thoroughly interpreted by the growth process from octahedral multiple-twin embryos. The origin of the tetrapod-shape consists in: (1) formation of...

S. Takeuchi H. Iwanaga M. Fujii

1993-01-01

413

Dye-Sensitization Studies of ZnO Using Total Internal-Reflection Techniques.  

National Technical Information Service (NTIS)

It is shown how a total internal reflection technique using pulsed light can be employed in the study of the photooxidation of an oxadicarbocyanine dye at ZnO single crystal electrodes. The quantum efficiency for photocurrent production by this dye is mea...

M. T. Spitler

1981-01-01

414

Magnetic Resonance Studies of Oxygen and Zinc-Vacancy Native Defects in Bulk ZnO Crystals  

NASA Astrophysics Data System (ADS)

ZnO is currently attracting increasing attention as a key material for a wide variety of electronic and optoelectronic applications. Optical, electrical, and magnetic properties of ZnO are believed to be strongly influenced by native defects. However, unambiguous experimental evidence confirming the formation of these defects in as-grown ZnO as well as evaluations of defect densities is currently sparse. In this talk we shall review our recent results from comprehensive defect characterization of as-grown bulk ZnO. By using electron paramagnetic resonance (EPR) and optically detected magnetic resonance (ODMR) spectroscopies, we show that both oxygen and zinc vacancies are formed in ZnO grown from melt without subjecting to irradiation. Defect concentrations are also determined. Based on spectral dependences of its EPR and ODMR signals, the VZn^- defect is concluded to act as a deep acceptor responsible for the red emission peaking at around 1.6 eV, but does not participate in the green emission as commonly believed. The energy level position of the VZn corresponding to the (2-/-) transition is determined to be at Ev+1.0 eV. The center is also shown to exhibit a strong JT distortion with a JT energy of 0.8 eV. On the other hand, oxygen vacancies are probably less important in carrier recombination since they were only detected in EPR but not in ODMR. Annealing properties of both defects were also studied and higher thermal stability of the Zn vacancy was concluded. It was also suggested that annealing of the VZn centers is facilitated by thermally-activated diffusion of impurity atoms to the VZn sites. The obtained results are of importance for a better understanding of the defects in ZnO. They also provide useful information on control of electrical properties and defect-reaction induced degradation during device processing and operation, in the material that is commonly used as a substrate for epitaxial growth of layered device structures based on ZnO.

Buyanova, Irina

2010-03-01

415

Single-Crystal Studies of Beta - Ag2HgI4.  

National Technical Information Service (NTIS)

The structure and transformation behavior of beta-Ag2HgI4 have been investigated by X-ray diffraction methods using single crystals. It has been verified that a single crystal of the beta-form, stable at room temperature, transforms to a single crystal of...

K. W. Browall J. S. Kasper H. Wiedemeier

1973-01-01

416

Controlling structural quality of ZnO thin film on c-plane sapphire during pulsed laser deposition  

NASA Astrophysics Data System (ADS)

The pulsed laser deposition (PLD) of ZnO thin film on c-plane sapphire has been studied as a function of various growth parameters such as nucleation layer temperature, annealing duration, laser pulse frequency, number of steps of ZnO deposition, final growth temperature and pressure. Among various growth parameters, laser pulse frequency was found to have significant influence to form single crystal ZnO film on c-plane sapphire through elimination of misaligned crystal domains completely. Allowing relaxation to the seeding layer by slowing down laser pulse frequency to 1 Hz established the complete epitaxial relationship between ZnO and sapphire over large plan view area, which is confirmed by plan view single crystal diffraction pattern, whereas ZnO grown at 5 Hz laser pulse frequency showed significant rotation between crystallites as evident from ring diffraction pattern from plan view TEM image. Using higher pressure (10-2 Torr) forms ZnO nanobullet during second stage of growth. AFM surface roughness improved to 2.4 nm for the sample grown with relaxed nucleation layer. Hall mobility also increased to 58 cm2 V-1 s-1 for this sample.

Loukya, B.; Sowjanya, P.; Dileep, K.; Shipra, R.; Kanuri, S.; Panchakarla, L. S.; Datta, R.

2011-08-01

417

Physics of Heavily Implanted Single Crystal Complex Oxides  

NASA Astrophysics Data System (ADS)

Ion implantation is known to result in a significant amount of damage in solid single crystals. In this work a battery of material probes is used to study the effect of a very high-dose He implantation in ferroelectric lithium niobate (LiNbO3) and the implantation-induced formation of defects. In addition, the evolution of these defects with post-implantation annealing is examined. After irradiation, a high concentration of defects is found to collect and create a network of thick prismatic planar defects having typical dimensions of 1.5 microm and 200 nm parallel and perpendicular to the Z axis, respectively. Optical microscopy shows that there is strong temperature dependence for forming the network; the density of these defects reaches a maximum value for an annealing temperature of 250 C. However, annealing to temperatures above 380 C fully eliminates the defects. High-resolution TEM studies indicate that the defects are likely localized twinning and dislocation pileups due to plastic deformation of the lattice to relieve He-implantation-induced stress. During this deformation He accumulates at the twin boundaries. A second type of implantation induced defects is studied using room temperature, high- resolution electron microscopy; this study shows that implanted He in LiNbO3 nucleates and accumulates as bubbles. These He inclusions are at 20 GPa pressure and most probably in the solid phase. In addition, the energetically favored shape of the inclusions in their as-implanted form is spherical and not oblate; this spherical shape is due to the fact their diameter is below a critical radius for balancing the surface and elastics energies as predicted by elastic theory. When annealed, the characteristic length scale of the He inclusions increases, forming faceted bubbles. Annealing also causes the He inclusions to migrate and accumulate into strings due to the preferred {1014}-pyramidal-twinning planes. The ion implantation-induced defects are found to be useful for several microfabrication techniques, in particular we describe the use of these defects for ion slicing of single crystal thin films from bulk crystals and ferroelectric domain patterning by low voltage pulses applied to a scanning force microscope tip. The origin of the rate of anomalously high spatially selective etching of a buried heavily implanted region in complex oxides is found to be closely related to the implantation-induced defects. He+-ion implantation in single-crystal LiNbO3 samples followed by low-temperature anneal and wet etched results in an etch-rate enhancement of 104. This high rate selective etch is crucial for the Crystal Ion Slicing process, a novel technique to fabricate single crystal thin films by slicing them off a bulk crystal. Experiments, using time-resolved optical microscopy and proximal-probe microscopy, show that this enhancement arises from the more rapid etch-solution transport in the thick prismatic planar defect network formed in the implanted region after annealing. Ferroelectric domain patterns are generated in He-implanted single-crystal bulk wafers of LiNbO3 by means of low-voltage pulses applied to a scanning force microscope tip and investigated using piezoresponse force microscopy and selective etching. It is shown that high fluence implantation results in isolation of the near surface region, creating a free-standing-film-like behavior for the layer above the heavily implanted region. At low fluence the implantation damage allows low voltage poling, apparently by vacancy-induced dipole formation. In addition, electrostatic repulsion of the poling-induced buried charges from adjacent domains limits the domain size and depth; this effect results in a uniform domain structures and potentially enables large area nanodomains patterns to be written.

Ofan, Avishai

418

Spontaneous phase transformation and exfoliation of rectangular single-crystal zinc hydroxy dodecylsulfate nanomembranes.  

PubMed

Free-standing two-dimensional (2D) nanostructures, exemplified by graphene and semiconductor nanomembranes, exhibit exotic electrical and mechanical properties and have great potential in electronic applications where devices need to be flexible or conformal to nonplanar surfaces. Based on our previous development of a substrate-free synthesis of large-area, free-standing zinc hydroxy dodecylsulfate (ZHDS) hexagonal nanomembranes, herein, we report a spontaneous phase transformation of ZHDS nanomembranes under extended reaction time. The hexagonal ZHDS sheets transformed into rectangular single crystal nanomembranes with sizes of hundreds of micrometers. They contain long-range-ordered zinc vacancies that can be fitted into an orthorhombic superlattice. A surplus of dodecylsulfate ions and a deficit of Zn(2+) diffusion near the water surface are believed to be the factors that drive the phase transformation. The phase transformation starts with the formation of zinc vacancies at the topmost layer of the hexagonal hillock, and propagates along the spiral growth path of the initial hexagonal sheets, which bears a great resemblance to the classic "periodic slip process". Mechanical property characterization of ZHDS nanomembranes by nanoindentation shows they behave much like structural polymers mechanically due to the incorporation of surfactant molecules. We also developed a one-step exfoliation and dehydration method that converts ZHDS nanomembranes to ZnO nanosheets using n-butylamine. This work provides a further understanding of the growth and stability of ZnO-based nanomembranes, as well as advisory insight for the further development on solution-based synthesis of free-standing, single-crystalline 2D nanostructures. PMID:23730895

Wang, Fei; Jakes, Joseph E; Geng, Dalong; Wang, Xudong

2013-06-06

419

ESR Study on Irradiated Ascorbic Acid Single Crystal  

NASA Astrophysics Data System (ADS)

Food irradiation is a ``cold'' process for preserving food and has been established as a safe and effective method of food processing and preservation after more than five decades of research and development. The small temperature increase, absence of residue and effectiveness of treatment of pre-packed food are the main advantages. In food industry, ascorbic acid and its derivatives are frequently used as antioxidant agents. However, irradiation is expected to produces changes in the molecules of food components and of course in the molecules of the agents added as preservation agents such as ascorbic acid. These changes in the molecular structures could cause decreases in the antioxidant actions of these agents. Therefore, the radiation resistance of these agents must be known to determine the amount of radiation dose to be delivered. Electron spin resonance (ESR) is one of the leading methods for identification of intermediates produced after irradiation. ESR spectrum of irradiated solid powder of ascorbic acid is fairly complex and determinations of involved radical species are difficult. In the present work, single crystals of ascorbic acid irradiated by gamma radiation are used to determine molecular structures of radiation induced radicalic species and four radicalic species related in pair with P21 crystal symmetry are found to be responsible from experimental ESR spectrum of gamma irradiated single crystal of ascorbic acid.

Tuner, H.; Korkmaz, M.

2007-04-01

420

Strength anomaly in B2 FeAl single crystals  

SciTech Connect

Strength and deformation microstructure of B2 Fe-39 and 48%Al single crystals (composition given in atomic percent), which were fully annealed to remove frozen-in vacancies, have been investigated at temperatures between room temperature and 1073K. The hardness of as-homogenized Fe-48Al is higher than that of as-homogenized Fe-39Al while after additional annealing at 698K the hardness of Fe-48Al becomes lower than that of Fe-39Al. Fe-39Al single crystals slowly cooled after homogenizing at a high temperature were deformed in compression as a function of temperature and crystal orientation. A peak of yield strength appears around 0.5T{sub m} (T{sub m} = melting temperature). The orientation dependence of the critical resolved shear stress does not obey Schmid`s law even at room temperature and is quite different from that of b.c.c. metals and B2 intermetallics at low temperatures. At the peak temperature slip transition from <111>-type to <001>-type is found to occur macroscopically and microscopically, while it is observed in TEM that some of the [111] dislocations decompose into [101] and [010] on the (1096I) plane below the peak temperature. The physical sources for the positive temperature dependence of yield stress of B2 FeAl are discussed based on the obtained results.

Yoshimi, K.; Hanada, S.; Yoo, M.H. [Oak Ridge National Lab., TN (United States); Matsumoto, N. [Tohoku Univ. (Japan). Graduate School

1994-12-31

421

ESR Study on Irradiated Ascorbic Acid Single Crystal  

SciTech Connect

Food irradiation is a 'cold' process for preserving food and has been established as a safe and effective method of food processing and preservation after more than five decades of research and development. The small temperature increase, absence of residue and effectiveness of treatment of pre-packed food are the main advantages. In food industry, ascorbic acid and its derivatives are frequently used as antioxidant agents. However, irradiation is expected to produces changes in the molecules of food components and of course in the molecules of the agents added as preservation agents such as ascorbic acid. These changes in the molecular structures could cause decreases in the antioxidant actions of these agents. Therefore, the radiation resistance of these agents must be known to determine the amount of radiation dose to be delivered. Electron spin resonance (ESR) is one of the leading methods for identification of intermediates produced after irradiation. ESR spectrum of irradiated solid powder of ascorbic acid is fairly complex and determinations of involved radical species are difficult. In the present work, single crystals of ascorbic acid irradiated by gamma radiation are used to determine molecular structures of radiation induced radicalic species and four radicalic species related in pair with P21 crystal symmetry are found to be responsible from experimental ESR spectrum of gamma irradiated single crystal of ascorbic acid.

Tuner, H.; Korkmaz, M. [Hacettepe University, Department of Physics Engineering, Ankara, 06800 (Turkey)

2007-04-23

422

Static and transient capacitance spectroscopy on ZnO  

NASA Astrophysics Data System (ADS)

We have investigated deep defects in ZnO single-crystals and thin films using deep level transient spectroscopy. In both we found the defects labeled E3 and E4 in literature. The spectra of the single-crystal depended on the prehistory of the sample. A peak with a thermal activation energy of about 53 meV appeared if the sample was kept in the dark and at a helium ambient of 10 mbar several days before the measurement. If the spectra are recorded above 400 K the defect level E3 and a much deeper defect disappeared while a new broad signal was observed.

Wenckstern, H. V.; Weinhold, S.; Biehne, G.; Pickenhain, R.; Kaidashev, E. M.; Lorenz, M.; Grundmann, M.

2005-06-01

423

Recent advances in ZnO materials and devices  

Microsoft Academic Search

Wurtzitic ZnO is a wide-bandgap (3.437 eV at 2 K) semiconductor which has many applications, such as piezoelectric transducers, varistors, phosphors, and transparent conducting films. Most of these applications require only polycrystalline material; however, recent successes in producing large-area single crystals have opened up the possibility of producing blue and UV light emitters, and high-temperature, high-power transistors. The main advantages

D. C. Look

2001-01-01

424

Search for Superconductivity in Single Crystals of Topological Insulators  

NASA Astrophysics Data System (ADS)

Observation of superconductivity in Cu-intercalated Bi2Se3, and in Bi2Te3 under pressure, open up the possibility of occurrence of superconductivity in other similarly modified structures. Here, we present detailed studies from a comprehensive search for superconductivity in selenides and tellurides of Bismuth and Antimony. High-quality single crystals were intercalated with a number of different elements using both in situ and ex situ techniques, then scanned for a resistive or magnetic transition to superconductivity. With an intent to understand the nature of intercalation in these compounds, we discuss results from our search for superconductivity, together with crystal structure analysis and detailed optical and x-ray photoelectron spectroscopy studies of the cleaved surface.

Guptasarma, Prasenjit; Sen, Somaditya; Dudek, John; Severson, Mary; Bissen, Mark

2012-02-01

425

Elasticity of single-crystal methane hydrate at high pressure  

NASA Astrophysics Data System (ADS)

By using in situ high-pressure Brillouin spectroscopy in a diamond-anvil cell, we have determined the pressure dependence of acoustic velocities, adiabatic elastic moduli, bulk modulus, elastic anisotropy, and Cauchy violation of single-crystal methane hydrate (MH) at pressures up to 0.6 GPa and 296 K. Acoustic velocities show nearly isotropic behaviors with respect to the crystal orientation, and the slight TA-mode softening with pressure implies that the structure of MH is becoming less stable against the shear component under high pressures. Elastic moduli and bulk modulus indicate that MH is slightly more compressible than ice Ih. These results would help to investigate their mechanical and thermodynamical stabilities, and provide important constraints on the icy moons of the outer solar system.

Shimizu, Hiroyasu; Kumazaki, Tatsuya; Kume, Tetsuji; Sasaki, Shigeo

2002-06-01

426

Magnetotransport in Tb2Fe17 single crystals  

NASA Astrophysics Data System (ADS)

We have performed measurements of the Hall effect, electrical resistivity, and magnetization on Tb2Fe17 single crystals in the 5 to 300 K temperature range, and in magnetic fields of up to 5 T. We find that the anomalous Hall effect of this ferromagnet depends strongly on the magnetization direction relative to the crystal axes. The AHE resistivity, measured with an applied magnetic field H perpendicular to the c-axis, is very large and varies linearly with the longitudinal resistivity ?, whereas the AHE resistivity for H along the hard magnetization direction is much smaller and increases as ?2. For the latter configuration, the electrical resistivity shows a sharp decrease at a field-induced first-order magnetization process (FOMP) which is observed in H ~ 2.7 T up to a temperature of 250 K.

Stankiewicz, Jolanta; Skokov, Konstantin P.

2011-07-01

427

Indentation Size Effect and Microhardness Study of ?-Sn Single Crystals  

NASA Astrophysics Data System (ADS)

The load dependence of apparent microhardness of ?-Sn single crystals having different growth directions is investigated. The measurements are performed on (110) planes of these crystals in the load range from 10 to 50 mN. It is found that the degree of the microhardness anisotropy decreases for higher indentation test loads. The examined materials exhibit the behaviour of indentation size effect (ISE), i.e., the apparent hardness increases with decreasing indentation load. Neither Meyer's law nor the proportional specimen resistance (PSR) model can fully explain the nonlinear variation of microhardness with load. Instead, preference is given to modified the PSR model based on the consideration of the effect of machining-induced residually stressed surface on the hardness measurement.

Sahin, O.; Uzun, O.; Kolemen, U.; Duzgun, B.; Ucar, N.

2005-12-01

428

NMR on Single Crystals of Potassium Cyanogen Bromide  

NASA Astrophysics Data System (ADS)

Single crystals of K(CN)_{ rm x}/(Br)_{rm 1-x} enriched in ^{15 }N have been studied by ^{15 }N NMR. Because of the anisotropic chemical shift, the NMR frequency spectrum of the orientational glass state reflects the distribution of cyanide orientations. By studying the spectrum at many orientations of each crystal, the orientational probability distribution function P( Omega) has been determined for x = 0.50 and for x = 0.20. The probability function is largest along the (100) directions, intermediate in the (110) directions, and nearly 0 along the (111) directions. The NMR determined P(Omega) is presented graphically and in terms of the Kubic Harmonic functions. The NMR results are in sharp contrast to molecular dynamics calculations but agree with neutron scattering data for x = 0.53.

Walton, Jeffrey Howard

429

The influence of Al 2O 3, MgO and ZnO on the crystallization characteristics and properties of lithium calcium silicate glasses and glass-ceramics  

Microsoft Academic Search

The crystallization characteristics of glasses based on the Li2OCaOSiO2 eutectic (9544C) system containing Al2O3, MgO and ZnO has been investigated by differential thermal analysis (DTA), X-ray diffraction analysis (XRD), and scanning electron microscopy (SEM). The partial replacement of Li2O by Al2O3 and CaO by MgO or ZnO in the studied glass-ceramics led to the development of different crystalline phase assemblages,

S. M. Salman; H. Darwish; E. A. Mahdy

2008-01-01

430

Electronic states of pyrene single crystal and of its single molecule inserted in a molecular vessel of cyclodextrin  

Microsoft Academic Search

Highly purified single crystals of pyrene were made by a gas phase crystal growth method from 180 times of zone-refined pyrene. The absorption spectra of the single crystal have been transformed from the reflection spectra between 2.5 and 6.5eV at 2, 77K and room temperature. The dry powder of ?-cyclodextrin including pyrene single molecule were prepared in vacuum to investigate

Nobuaki Takahashi; Bold Gombojav; Takehisa Yoshinari; Shin-Ichiro Nagasaka; Yoshio Takahashi; Aishi Yamamoto; Takenari Goto; Atsuo Kasuya

2004-01-01

431

The effect of crystal geometry on the formation and crack development in molybdenum single crystals  

NASA Astrophysics Data System (ADS)

The systematic study of the defect structure evolution in single crystal specimens deformed in situ in the high voltage transmission electron microscope (HVTEM) was started around 1977 in the Baikov Metallurgy Institute of the USSR Academy of Sciences. All the experience gathered for the past 30 years has set up the basis for the determination of the way that metals adapt to the different physical factors inside the HVTEM column. In the present work the detailed phenomenology of the generation and propagation process of cracks in single crystals of Mo with different crystallographic orientations as well as the kinetics of opening of primary and secondary cracks and the tip evolution for cracks with different dislocation generation sources is presented.

Tamayo-Meza, Pedro A.; Yermishkin, Viacheslav; Schabes-Retchkiman, Pablo

2010-04-01

432

Advanced piezoelectric single crystal based transducers for naval sonar applications  

NASA Astrophysics Data System (ADS)

TRS is developing new transducers based on single crystal piezoelectric materials such as Pb(Mg1/3Nb2/3)x-1TixO3 (PMN-PT). Single crystal piezoelectrics such as PMN-PT exhibit very high piezoelectric coefficients (d33 ~ 1800 to >2000 pC/N) and electromechanical coupling factors (k33 > 0.9), respectively, which may be exploited for improving the performance of broad bandwidth and high frequency sonar. Apart from basic performance, much research has been done on reducing the size and increasing the output power of tonpilz transducers for sonar applications. Results are presented from two different studies. "33" mode single crystal tonpilz transducers have reduced stack lengths due to their low elastic stiffness relative to PZTs, however, this produces non-ideal aspect ratios due to large lateral dimensions. Alternative "31" resonance mode tonpilz elements are proposed to improve performance over these "33" designs. d32 values as high as 1600 pC/N have been observed, and since prestress is applied perpendicular to the poling direction, "31" mode Tonpilz elements exhibit lower loss and higher reliability than "33" mode designs. Planar high power tonpilz arrays are the optimum way to obtain the required acoustic pressure and bandwidth for small footprint, high power sensors. An important issue for these sensors is temperature and prestress stability, since fluctuations in tonpilz properties affects power delivery and sensing electronic design. TRS used the approach of modifying the composition of PMN-PT to improve the temperature dependence of properties of the material. Results show up to a 50% decrease in temperature change while losing minimal source level.

Snook, Kevin A.; Rehrig, Paul W.; Hackenberger, Wesley S.; Jiang, Xiaoning; Meyer, Richard J., Jr.; Markley, Douglas

2005-05-01

433

Gold coated ZnO nanorod biosensor for glucose detection  

NASA Astrophysics Data System (ADS)

Gold coated ZnO nanorod based biosensor has been fabricated for its glucose detecting abilities and compared with that of ZnO nanorod based biosensor. SEM images of electrochemically grown ZnO nanorods show hexagonally grown ZnO nanorods on an ITO substrate. Electrochemical analysis show that gold coated ZnO based biosensors have higher sensitivity, lower limit of detection and a wider linear range for glucose detection. The results demonstrate that gold coated ZnO nanorod based biosensors are a promising material for biosensor applications over single component ZnO nanorod based biosensor.

Bhattacharya, Anuradha; Jain, Chhavi; Rao, V. Padmanapan; Banerjee, S.

2012-06-01

434

Carrier doping and interlayer coupling in HTSC single crystals  

SciTech Connect

Experimental results of the effect of carrier doping on the irreversibility lines in (La,Sr){sub 2}CuO{sub 4{minus}{delta}} and Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8 + {delta}} single crystals are summarized. As a function of Sr or oxygen contents, systematic and dramatic widening of the irreversible regions in the B {minus} T phase diagram was observed in both systems. The present study suggests the critical importance of carrier concentration which directly affects the interlayer coupling strength and dimensionality of the flux line lattice in all the layered HTSC compounds as a universal feature.

Kishio, K.; Shimoyama, J.; Kimura, T.; Kotaka, Y.; Kitazawa, K. [Univ. of Tokyo (Japan). Dept. of Applied Chemistry; Yamafuji, K. [Kyushu Univ., Fukuoka (Japan). Dept. of Electronics; Li, Q.; Suenaga, M. [Brookhaven National Lab., Upton, NY (United States). Div. of Materials Science

1994-09-01

435

Mechanical properties of ZnSe : Cr2+ single crystals  

NASA Astrophysics Data System (ADS)

The microhardness of single-crystal samples of ZnSe: Cr2+ with a chromium concentration in the range from 3.3 1017 to 4.0 1019 cm-3 has been studied. The microhardness as a function of the load on the indenter on the faces (111), (1bar 10), and (001) of the ZnSe: Cr2+ and ZnSe samples has been measured. It has been established that doping of zinc selenide with chromium leads to a decrease in the anisotropy of the mechanical properties and stabilization of the cubic sphalerite structure.

Fedorenko, O. A.; Zagoruiko, Yu. A.; Kovalenko, N. O.

2012-11-01

436

Electric detection of ferromagnetic resonance in single crystal iron film  

NASA Astrophysics Data System (ADS)

We report electric detection of ferromagnetic resonance (FMR) in epitaxially grown single crystal iron film through microwave photovoltage generation technique. The experimental results agree well with the established theory about FMR in iron films, showing excellent extendability of such a technique onto different ferromagnets as an effective way to study magnetocrystalline anisotropy and spin excitations. Furthermore, the information about the phase of magnetization precession is implicated in the lineshape of photovoltage, which makes it possible to probe in details into magnetic phase dynamics that is of significance for devising spintronic devices.

Hui, Xiong; Wirthmann, A.; Gui, Y. S.; Tian, Y.; Jin, X. F.; Chen, Z. H.; Shen, S. C.; Hu, C.-M.

2008-12-01

437

Single molecule studies on dynamics in liquid crystals.  

PubMed

Single molecule (SM) methods are able to resolve structure related dynamics of guest molecules in liquid crystals (LC). Highly diluted small dye molecules on the one hand explore structure formation and LC dynamics, on the other hand they report about a distortion caused by the guest molecules. The anisotropic structure of LC materials is used to retrieve specific conformation related properties of larger guest molecules like conjugated polymers. This in particular sheds light on organization mechanisms within biological cells, where large molecules are found in nematic LC surroundings. This review gives a short overview related to the application of highly sensitive SM detection schemes in LC. PMID:24077123

Tuber, Daniela; von Borczyskowski, Christian

2013-09-26

438

Transient current electric field profiling of single crystal CVD diamond  

NASA Astrophysics Data System (ADS)

The transient current technique (TCT) has been adapted for profiling of the electric field distribution in intrinsic single crystal CVD diamond. It was found that successive hole transits do not appreciably affect the electric field distribution within the sample. Transits of holes can therefore be used to probe the electric field distribution and also the distribution of trapped charge. Electron transits, on the other hand, cause an accumulation of negative charge in the sample. Illumination with blue or green light was shown to lead to accumulation of positive charge. Low concentrations of trapped charge can be detected in diamond using TCT, corresponding to an ionized impurity concentration below N = 1010 cm-3.

Isberg, J.; Gabrysch, M.; Tajani, A.; Twitchen, D. J.

2006-08-01

439

Physical properties of SrSn4 single crystals  

SciTech Connect

We present detailed thermodynamic and transport measurements on single crystals of the recently discovered binary intermetallic superconductor, SrSn{sub 4}. We find this material to be a slightly anisotropic three-dimensional, strongly coupled, possibly multiband, superconductor. Hydrostatic pressure causes a decrease in the superconducting transition temperature at the rate of {approx} -0.068 K kbar{sup -1}. Band structure calculations are consistent with experimental data on the Sommerfeld coefficient and upper superconducting critical field anisotropy, and suggest a complex, multi-sheet Fermi surface formed by four bands.

Lin, Xiao [Iowa State University; Budko, Sergey L [Ames Laboratory and Iowa State University; Samolyuk, German D [ORNL; Torikachvili, Milton S [San Diego State University; Canfield, Paul [Ames Laboratory and Iowa State University

2011-01-01

440

Frost Heave Dynamics at a Single Crystal Interface  

NASA Astrophysics Data System (ADS)

We study flow in a surface-melted layer of a single crystal of ice at a plane solid interface. The flow, which is induced by a temperature gradient in the melted layer, causes the ice to grow normal to the interface. The process is the basis for frost heave in frozen soils. Flow is observed in a limited range of temperatures near the melting point, implying that surface melting is absent below this range. The data are analyzed in terms of a model which allows estimates of the fluid layer thickness. The results are not consistent with interfacial melting due to purely van der Waals forces.

Wilen, L. A.; Dash, J. G.

1995-06-01

441

Nonlinear microwave switching response of BSCCO single crystals  

SciTech Connect

Measurements of the surface impedance in Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} single crystal with microwave currents flowing along the {cflx c} axis show clear evidence of a step-like nonlinearity. The surface resistance switches between apparently quantized levels for microwave field strength changes < 1 mG. This nonlinear response can arise from the presence of intrinsic Josephson junctions along the {cflx c} axis of these samples driven by the microwave current.

Jacobs, T.; Sridhar, S. [Northeastern Univ., Boston, MA (United States). Dept. of Physics; Willemsen, B.A. [Northeastern Univ., Boston, MA (United States). Dept. of Physics]|[Rome Lab., Hanscom AFB, MA (United States); Li, Qiang [Brookhaven National Lab., Upton, NY (United States); Gu, G.D.; Koshizuka, N. [Superconductivity Research Lab., Tokyo (Japan)

1996-06-01

442

Irreversible magnetovolume effect in Nd7Rh3 single crystal  

NASA Astrophysics Data System (ADS)

Magnetovolume effect in Nd7Rh3 single crystal has been studied by measuring the magnetostriction as a function of external magnetic field at 4.2 K. An irreversible magnetovolume effect having a negative remanent volume magnetostriction was observed when the external magnetic field was applied along the b-axis. The irreversible magnetostrictive effect takes place in the longitudinal magnetostriction along the b-axis. The remanent magnetostriction along the b-axis relaxes after removing external magnetic field for several hours and equilibrium state is stabilized.

Tsutaoka, Takanori; Shimomura, Koji; Tanaka, Akira

2011-12-01

443

Raman Investigations of Rare Earth Arsenate Single Crystals  

SciTech Connect

Polarized Raman Spectroscopy was used to investigate the room-temperature phonon characteristics of a series of rare-earth arsenate (REAsO4, RE = Sm, Eu, Gd, Tb, Dy, Ho, Tm, Yb, and Lu) single crystals. The Raman data were interpreted in a systematic manner based on the known tetragonal zircon structure of these compounds, and assignments and correlations were made for the observed bands. We found that the wavenumber of the internal modes of the AsO4 tetrahedron increased with increasing atomic number, and for three out of four lattice wavenumbers observed, this tendency was not nearly so marked as in the case of the internal mode wavenumber.

Barros, G [Universidade Federal do Ceara, Ceara, Brazil; Santos, C. C. [Universidade Federal do Ceara, Ceara, Brazil; Ayala, A. P. [Universidade Federal do Ceara, Ceara, Brazil; Guedes, I. [Universidade Federal do Ceara, Ceara, Brazil; Boatner, Lynn A [ORNL; Loong, C. K. [Sun Yat-Sen University, Guangzhou, China

2010-01-01

444

Electrical Resistivities of Nonstoichiometric Cerium Hydride Single Crystals  

Microsoft Academic Search

Electrical resistivities as a function of temperature (?130 to 25C) were determined on single crystals of cerium hydride ranging in composition from CeH1.94&sngbnd;CeH2.85. Measurements were performed in an inert-atmosphere dry box using the four-point probe technique. Cerium hydride exhibited metallic behavior in the range CeH1.9&sngbnd;CeH2.7. However, at a composition of about CeH2.85, a positive temperature coefficient of conductivity indicative of

G. G. Libowitz; J. G. Pack

1969-01-01

445

Single crystal EPR of Mn12-acetate clusters  

NASA Astrophysics Data System (ADS)

We have used electron paramagnetic resonance (EPR) to study the energy level diagram of the Mn12-cluster compound, in the frequency range from 35 to 115 GHz. Our high sensitivity allows the observation of multiple resonances, and their temperature dependence, on high-quality single crystals. The results are in qualitative agreement with the picture of a strong axial anisotropy. Measurements with the field applied parallel and perpendicular to the easy axis reveal significant zero-field splittings and level crossings, as predicted theoretically.

Hill, S.; Perenboom, J. A. A. J.; Stalcup, T.; Dalal, N. S.; Hathaway, T.; Brooks, J. S.

1998-05-01

446

Photoluminescence properties of MgxZn1-xSe single crystals  

NASA Astrophysics Data System (ADS)

MgxZn1-xSe single crystals were grown by the closed tube sublimation method. The MgxZn1-xSe single crystals crystallized into zincblende and wurtzite structures in the composition ranges of x=0.0-0.1 and x=0.2-0.6, respectively. Blue and violet emissions with LO phonon replica and self-activated emissions in the MgxZn1-xSe single crystals were observed at 10 K.

Park, Sang-An; Song, Ho-Jun; Kim, Wha-Tek; Kim, Hyung-Gon; Jin, Moon-Seog; Kim, Chang-Dae; Yoon, Chang-Sun

1998-03-01

447

The Thermoanalysis of Metal Single Crystals and a New Thermoelectric Effect of Bismuth Crystals Grown in Magnetic Fields  

Microsoft Academic Search

Part I. The Thermoanalysis of Bi Single Crystals Production of crystals.-Crystals of Bi of any desired orientation were grown by the method of Goetz, one half of each normally, the other half within a transversal magnetic field. The orientations, predetermined by a seed crystal, were not affected by this process. Two methods of growth-the continuous and the discontinuous-were used. The

Alexander Goetz; Maurice F. Hasler

1930-01-01

448

Crystal growth, EPR and site-selective laser spectroscopy of Gd 3+-activated LiCaALF 6 single crystals  

Microsoft Academic Search

Ce3+-activated LiCaAlF6 (LiCAF) and LiSrAlF6 (LiSAF) single crystals are the most prospective active media for directly pumped UV solid-state tunable lasers. Due to the geterovalent activation nature of these crystals, crystal spectroscopic properties as well as their laser efficiency strongly depend on the actual crystal growth conditions. In order to establish the growth-related peculiarities of activator center formation in LiCAF,

R. Yu. Abdulsabirov; M. A. Dubinskii; S. L. Korableva; A. K. Naumov; V. V. Semashko; V. G. Stepanov; M. S. Zhuchkov

2001-01-01

449

Epitaxial properties of ZnO thin films on SrTiO3 substrates grown by laser molecular beam epitaxy  

Microsoft Academic Search

Epitaxial ZnO thin films with different orientations have been grown by laser molecular beam epitaxy on (001)-, (011)-, and (111)-orientated SrTiO3 single-crystal substrates. The growth behavior was in situ monitored by reflection high-energy electron diffraction, and the epitaxial orientation relations were reconfirmed by ex situ x-ray diffraction measurements. In the case of ZnO on SrTiO3(001), four orthogonal domains coexisted in

X. H. Wei; Y. R. Li; J. Zhu; W. Huang; Y. Zhang; W. B. Luo; H. Ji

2007-01-01

450

Effects of Phonon Coupling and Free Carriers on Band-edge Emission at Room Temperature in n-type ZnO Crystals  

SciTech Connect

Room-temperature photoluminescence has been studied in n-type bulk ZnO crystals representing three different growth methods and having free-carrier concentrations (n) ranging from 10{sup 13} to 10{sup 18} cm{sup -3}. The near-band-edge emission has both free-exciton and free-exciton-phonon contributions, with the strength of the phonon coupling dependent on sample defect concentrations. Band-gap shrinkage effects are used to explain a decrease in emission energy for the higher n values. Band filling and band nonparabolicity are predicted to be important for n>10{sup 19} cm{sup -3}. At 300 K, in the absence of free carriers, the free-exciton energy is 3.312{+-}0.004 eV.

Giles, N. C. [West Virginia University; Xu, Chunchuan [West Virginia University; Callahan, M. J. [Air Force Research Laboratory; Wang, Buguo [Air Force Research Laboratory; Neal, John S [ORNL; Boatner, Lynn A [ORNL

2006-01-01

451

Broadband ZnO Single-Nanowire Light-Emitting Diode  

Microsoft Academic Search

We present a novel technique for reliable electrical injection into single semiconductor nanowires for light-emitting diodes and lasers. The method makes use of a high-resolution negative electron-beam resist and direct electron-beam patterning for the precise fabrication of a metallic top contact along the length of the nanowire, while a planar substrate is used as a bottom contact. It can be

Jiming Bao; Mariano A. Zimmler; Federico Capasso; Xiaowei Wang; Z. F. Ren

2006-01-01

452

Experimental deformation of olivine single crystals at lithospheric temperatures  

NASA Astrophysics Data System (ADS)

Rheological properties of mantle minerals and rocks at temperatures (T) appropriate to much of Earth's lithosphere have remained poorly constrained, even though past experimental studies on olivine single crystals and polycrystalline aggregates have quantified the high-temperature creep mechanisms (T > 1200C). Consequently, we have performed deformation experiments on crystals of San Carlos olivine at lower temperatures, from 900 to 1200C, in triaxial compression along the [101]c direction. The experiments were carried out at a confining pressure of 300 MPa in a high-resolution gas-medium mechanical testing apparatus at differential stresses of 100 to 500 MPa. Several samples were deformed at constant displacement rate and others at constant load, in order to provide insight into possible effects of work-hardening. Under the deformation conditions investigated, little evidence of work-hardening was observed. The data follow a power-law dependence on stress, as in previous high-temperature deformation studies. The samples were, however, considerably weaker than predicted by the experimentally determined high-temperature constitutive equation for olivine crystals of this orientation from the study of Bai et al. (1991). The mechanical behavior correlates instead with the weaker of the two mechanisms (flow laws) that contribute to the high-temperature constitutive equation. Thus, our experiments demonstrate that published high-temperature constitutive equations overestimate the strength of lithospheric mantle and that the transition to low-temperature creep occurs at lower temperatures than previously inferred.

Demouchy, Sylvie; Schneider, Stephen E.; Mackwell, Stephen J.; Zimmerman, Mark E.; Kohlstedt, David L.

2009-02-01

453

Plastic anisotropy in MoSi{sub 2} single crystals  

SciTech Connect

Single crystals Of MoSi{sub 2} are an order of magnitude stronger when compressed along [001] than along any other orientation. This is because the easy slip systems, <101><100> and <110><111>, have a zero Schmid factor acting on them so that harder slip systems are forced into operation. We find that [001] crystals compressed at 1OOO{degree}C yield by slip on <103><331>. TEM shows that the 1/2<331> dislocations tend to decompose into 1/2<111> and <110> dislocations. This decomposition process apparently inhibits the mobility of 1/2<331> dislocations at higher temperatures and another system, <101><1ll>, becomes operative at 1300{degree}C and above. [021] crystals have been tested for comparison and are found to yield at much lower stresses on the easy systems. In the design of advanced high temperature structural materials based on MOSi{sub 2}, the large plastic anisotropy should be used to advantage.

Mitchell, T.E.; Maloy, S.A.

1993-05-01

454

Synthesis of mesoporous zeolite single crystals with cheap porogens  

NASA Astrophysics Data System (ADS)

Mesoporous zeolite (silicalite-1, ZSM-5, TS-1) single crystals have been successfully synthesized by adding soluble starch or sodium carboxymethyl cellulose (CMC) to a conventional zeolite synthesis system. The obtained samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen sorption analysis, 27Al magic angle spinning nuclear magnetic resonance (27Al MAS NMR), temperature-programmed desorption of ammonia (NH3-TPD) and ultraviolet-visible spectroscopy (UV-vis). The SEM images clearly show that all zeolite crystals possess the similar morphology with particle size of about 300 nm, the TEM images reveal that irregular intracrystal pores are randomly distributed in the whole crystal. 27Al MAS NMR spectra indicate that nearly all of the Al atoms are in tetrahedral co-ordination in ZSM-5, UV-vis spectra confirm that nearly all of titanium atoms are incorporated into the framework of TS-1. The catalytic activity of meso-ZSM-5 in acetalization of cyclohexanone and meso-TS-1 in hydroxylation of phenol was also studied. The synthesis method reported in this paper is cost-effective and environmental friendly, can be easily expended to prepare other hierarchical structured zeolites.

Tao, Haixiang; Li, Changlin; Ren, Jiawen; Wang, Yanqin; Lu, Guanzhong

2011-07-01

455

Single crystal integration of an optical interference filter and photodiode  

SciTech Connect

An all-semiconductor, single-crystal, integrated optical detector has been produced for the visible, in which a photodiode and an optical interference filter (high reflector) were integrated in a single growth run by metal-organic chemical vapor deposition. In this structure, the high reflector is both optically and electrically active, being composed of alternating, doped, quarter-wave layers of GaP and GaAs/sub 0.2/P/sub 0.8/. The diode is a p-n junction superlattice composed of much thinner layers of GaP and GaAs/sub 0.35/P/sub 0.65/. The photodiode responds to light from 460 to 600 nm, while the high reflector rejects a narrow 10 nm band centered near 500 nm. The rejection factor is approx.7 db for these prototype devices. The quantum efficiency, linearity, temperature and bias dependence of the spectral response are reported.

Gourley, P.L.; Biefeld, R.M.; Zipperian, T.E.

1986-01-01

456

Thermally reversible single-crystal to single-crystal transformation of mononuclear to dinuclear Zn(ii) complexes by [2+2] cycloaddition reaction.  

PubMed

Two Zn(ii) complexes of trans-4-styrylpyridine ligands undergo [2+2] cycloaddition reaction forming Zn(ii) complex dimers in a single-crystal to single-crystal (SCSC) manner which were thermally reversible. The dimers are presumed to be the stable intermediates in the formation of 1D coordination polymers upon prolonged exposure to UV light. PMID:24022693

Medishetty, Raghavender; Yap, Terence Teck Sheng; Koh, Lip Lin; Vittal, Jagadese J

2013-09-24

457

Solid-state single-crystal-to-single-crystal transformation from a 2D layer to a 3D framework mediated by lattice iodine release.  

PubMed

We describe an exceedingly rare example of solid-state single-crystal-to-single-crystal transformation from a 2D layer to a known 3D framework via lattice iodine release, which involves the formation of a new Cu-O ligand bond and a change in the metal coordination geometry. PMID:22785388

He, Yuan-Chun; Yang, Jin; Yang, Guo-Cheng; Kan, Wei-Qiu; Ma, Jian-Fang

2012-07-02

458

Al/ZnO/a-SiGe:H: A system protected by the ZnO buffer from metal-induced crystallization  

SciTech Connect

Metal-Induced-Crystallization (MIC) by the contact of amorphous semiconductors with metals is one of the degradation factors in solar cells. This study has been made on the barrier properties of a ZnO layer between undoped a-SiGe:H and Al metallization films in the structure (001)Si/SiO{sub 2}/a-SiGe:H/ZnO/Al. Plasma assisted CVD deposition was used to produce a-Si{sub 1{minus}x}Ge{sub x}:H (x = 0 to 1) undoped films over thermally oxidized Si-wafers. There were covered with 500 {angstrom} and 1,000 {angstrom} thick transparent conductive layers of ZnO:Al and then 1,000 {angstrom} thick films of Al. A set of Al-implanted A-Si, a-Ge, and a-Si{sub 0.5}Ge{sub 0.5} films on Si/SiO{sub 2} substrates was also prepared to study MIC in an amorphous system with dispersed Al. The structures were annealed in vacuum in the temperature range of 200 C to 400 C for 1h. X-ray diffraction studies demonstrated the a-SiGe:H stability against crystallization under ZnO protection up to 400 C. Secondary Ion Mass Spectroscopy didn't reveal any noticeable redistribution of Al inside Al-implanted a-Si:H and a-Si{sub 0.5}Ge{sub 0.5}:H samples after annealing at 400 C for 1h, but strong Al diffusion was seen in the a-Ge:H layer. Nevertheless, no MIC was observed in any of the Al-implanted a-materials.

Edelman, F.; Brener, R.; Cytermann, C.; Weil, R.; Beneking, C.; Beyer, W.; Skorupa, W.; Yankov, R.; Werner, P.

1997-07-01

459

Synthesis, growth and characterization of 4-methyl anilinium phenolsulfonate single crystal  

NASA Astrophysics Data System (ADS)

4-Methyl anilinium phenolsulfonate single crystal has been synthesized and grown by the slow evaporation solution technique at room temperature using methanol as a solvent. The crystal structure of the grown crystal was determined by the single crystal X-ray diffraction method. The various functional groups present in the crystal, and the different types of protons and carbons have been identified by the FT-IR and NMR spectral analyses respectively. Optical properties were determined by UVvisNIR spectroscopic and photoluminescence studies. The thermal and mechanical stabilities of 4-methyl anilinium phenolsulfonate single crystal have been investigated by TGA/DTA and Vickers microhardness measurements respectively.

Jovita, Josephine Viagulamary; Boopathi, Kittusamy; Ramasamy, Perumal; Ramanand, Aroor; Sagayaraj, Pappu

2013-10-01

460

Growth and properties of Lithium Salicylate single crystals  

SciTech Connect

An attractive feature of {sup 6}Li containing fluorescence materials that determines their potential application in radiation detection is the capture reaction with slow ({approx}< 100 keV) neutrons: {sup 6}Li + n = {sup 4}He + {sup 3}H + 4.8MeV. The use of {sup 6}Li-salicylate (LiSal, LiC{sub 6}H{sub 5}O{sub 3}) for thermal neutron detection was previously studied in liquid and polycrystalline scintillators. The studies showed that both liquid and polycrystalline LiSal scintillators could be utilized in pulse shape discrimination (PSD) techniques that enable separation of neutrons from the background gamma radiation. However, it was found that the efficiency of neutron detection using LiSal in liquid solutions was severely limited by its low solubility in commonly used organic solvents like, for example, toluene or xylene. Better results were obtained with neutron detectors containing the compound in its crystalline form, such as pressed pellets, or microscopic-scale (7-14 micron) crystals dispersed in various media. The expectation drown from these studies was that further improvement of pulse height, PSD, and efficiency characteristics could be reached with larger and more transparent LiSal crystals, growth of which has not been reported so far. In this paper, we present the first results on growth and characterization of relatively large, a cm-scale size, single crystals of LiSal with good optical quality. The crystals were grown both from aqueous and anhydrous (methanol) media, mainly for neutron detection studies. However, the results on growth and structural characterization may be interesting for other fields where LiSal, together with other alkali metal salicylates, is used for biological, medical, and chemical (as catalyst) applications.

Zaitseva, N; Newby, J; Hull, G; Saw, C; Carman, L; Cherepy, N; Payne, S

2009-02-13

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