Characterization of Gallium Indium Phosphide and Progress of Aluminum Gallium Indium Phosphide System Quantum-Well Laser Diode.

PubMed

Hamada, Hiroki

2017-07-28

Highly ordered gallium indium phosphide layers with the low bandgap have been successfully grown on the (100) GaAs substrates, the misorientation toward [01-1] direction, using the low-pressure metal organic chemical vapor deposition method. It is found that the optical properties of the layers are same as those of the disordered ones, essentially different from the ordered ones having two orientations towards [1-11] and [11-1] directions grown on (100) gallium arsenide substrates, which were previously reported. The bandgap at 300 K is 1.791 eV. The value is the smallest ever reported, to our knowledge. The high performance transverse stabilized AlGaInP laser diodes with strain compensated quantum well structure, which is developed in 1992, have been successfully obtained by controlling the misorientation angle and directions of GaAs substrates. The structure is applied to quantum dots laser diodes. This paper also describes the development history of the quantum well and the quantum dots laser diodes, and their future prospects.

Characterization of Gallium Indium Phosphide and Progress of Aluminum Gallium Indium Phosphide System Quantum-Well Laser Diode

PubMed Central

Hamada, Hiroki

2017-01-01

Highly ordered gallium indium phosphide layers with the low bandgap have been successfully grown on the (100) GaAs substrates, the misorientation toward [01−1] direction, using the low-pressure metal organic chemical vapor deposition method. It is found that the optical properties of the layers are same as those of the disordered ones, essentially different from the ordered ones having two orientations towards [1−11] and [11−1] directions grown on (100) gallium arsenide substrates, which were previously reported. The bandgap at 300 K is 1.791 eV. The value is the smallest ever reported, to our knowledge. The high performance transverse stabilized AlGaInP laser diodes with strain compensated quantum well structure, which is developed in 1992, have been successfully obtained by controlling the misorientation angle and directions of GaAs substrates. The structure is applied to quantum dots laser diodes. This paper also describes the development history of the quantum well and the quantum dots laser diodes, and their future prospects. PMID:28773227

Efficient water reduction with gallium phosphide nanowires

PubMed Central

Standing, Anthony; Assali, Simone; Gao, Lu; Verheijen, Marcel A.; van Dam, Dick; Cui, Yingchao; Notten, Peter H. L.; Haverkort, Jos E. M.; Bakkers, Erik P. A. M.

2015-01-01

Photoelectrochemical hydrogen production from solar energy and water offers a clean and sustainable fuel option for the future. Planar III/V material systems have shown the highest efficiencies, but are expensive. By moving to the nanowire regime the demand on material quantity is reduced, and new materials can be uncovered, such as wurtzite gallium phosphide, featuring a direct bandgap. This is one of the few materials combining large solar light absorption and (close to) ideal band-edge positions for full water splitting. Here we report the photoelectrochemical reduction of water, on a p-type wurtzite gallium phosphide nanowire photocathode. By modifying geometry to reduce electrical resistance and enhance optical absorption, and modifying the surface with a multistep platinum deposition, high current densities and open circuit potentials were achieved. Our results demonstrate the capabilities of this material, even when used in such low quantities, as in nanowires. PMID:26183949

Comparative radiation resistance, temperature dependence and performance of diffused junction indium phosphide solar cells

NASA Technical Reports Server (NTRS)

Weinberg, I.; Swartz, C. K.; Hart, R. E., Jr.; Ghandhi, S. K.; Borrego, J. M.

1987-01-01

Indium phosphide solar cells whose p-n junctions were processed by the open tube capped diffusion and by the closed tube uncapped diffusion of sulfur into Czochralski-grown p-type substrates are compared. Differences found in radiation resistance were attributed to the effects of increased base dopant concentration. Both sets of cells showed superior radiation resistance to that of gallium arsenide cells, in agreement with previous results. No correlation was, however, found between the open-circuit voltage and the temperature dependence of the maximum power.

Visible light electroluminescent diodes of indium-gallium phosphide

NASA Technical Reports Server (NTRS)

Clough, R.; Richman, D.; Tietjen, J.

1970-01-01

Vapor deposition and acceptor impurity diffusion techniques are used to prepare indium-gallium phosphide junctions. Certain problems in preparation are overcome by altering gas flow conditions and by increasing the concentration of phosphine in the gas. A general formula is given for the alloy's composition.

Development of gallium aluminum phosphide electroluminescent diodes

NASA Technical Reports Server (NTRS)

Chicotka, R. J.; Lorenz, M. R.; Nethercot, A. H.; Pettit, G. D.

1972-01-01

Work done on the development of gallium aluminum phosphide alloys for electroluminescent light sources is described. The preparation of this wide band gap semiconductor alloy, its physical properties (particularly the band structure, the electrical characteristics, and the light emitting properties) and work done on the fabrication of diode structures from these alloys are broadly covered.

Development of high temperature gallium phosphide rectifiers

NASA Technical Reports Server (NTRS)

Craford, M. G.; Keune, D. L.

1972-01-01

Large area high performance, GaP rectifiers were fabricated by means of Zn diffusion into vapor phase epitaxial GaP. Devices with an active area of 0.01 sq cm typically exhibit forward voltages of 3 volts for a bias current of 1 ampere and have reverse breakdown voltages of 300 volts for temperatures from 27 C to 400 C. Typical device reverse saturation current at a reverse bias of 150 volts is less than 10 to the minus 9th power amp at 27 C and less than 0.000050 amp at 400 C.

Molecular fingerprint-region spectroscopy from 5 to 12  μm using an orientation-patterned gallium phosphide optical parametric oscillator.

PubMed

Maidment, Luke; Schunemann, Peter G; Reid, Derryck T

2016-09-15

We report a femtosecond optical parametric oscillator (OPO) based on the new semiconductor gain material orientation-patterned gallium phosphide (OP-GaP), which enables the production of high-repetition-rate femtosecond pulses spanning 5-12 μm with average powers in the few to tens of milliwatts range. This is the first example of a broadband OPO operating across the molecular fingerprint region, and we demonstrate its potential by conducting broadband Fourier-transform spectroscopy using water vapor and a polystyrene reference standard.

Native gallium adatoms discovered on atomically-smooth gallium nitride surfaces at low temperature.

PubMed

Alam, Khan; Foley, Andrew; Smith, Arthur R

2015-03-11

In advanced compound semiconductor devices, such as in quantum dot and quantum well systems, detailed atomic configurations at the growth surfaces are vital in determining the structural and electronic properties. Therefore, it is important to investigate the surface reconstructions in order to make further technological advancements. Usually, conventional semiconductor surfaces (e.g., arsenides, phosphides, and antimonides) are highly reactive due to the existence of a high density of group V (anion) surface dangling bonds. However, in the case of nitrides, group III rich growth conditions in molecular beam epitaxy are usually preferred leading to group III (Ga)-rich surfaces. Here, we use low-temperature scanning tunneling microscopy to reveal a uniform distribution of native gallium adatoms with a density of 0.3%-0.5% of a monolayer on the clean, as-grown surface of nitrogen polar GaN(0001̅) having the centered 6 × 12 reconstruction. Unseen at room temperature, these Ga adatoms are strongly bound to the surface but move with an extremely low surface diffusion barrier and a high density saturation coverage in thermodynamic equilibrium with Ga droplets. Furthermore, the Ga adatoms reveal an intrinsic surface chirality and an asymmetric site occupation. These observations can have important impacts in the understanding of gallium nitride surfaces.

Doping of epitaxial III-V semiconductors for optoelectronic and magnetoelectronic applications

NASA Astrophysics Data System (ADS)

Overberg, Mark Eddy

Doped III-V semiconducting materials were studied in this dissertation for use in optoelectronic and magnetoelectronic applications. The specific areas of use are emitters for fiber optic communication and room temperature ferromagnetic layers for spintronic devices. The general requirement for both application areas is the ability to heavily dope (or alloy) the III-Vs with the intended active element, while still maintaining good crystallinity and semiconducting properties. Four dopant/semiconductor systems were investigated: erbium in gallium nitride (GaN:Er), europium in gallium nitride (GaN:Eu), manganese in gallium nitride (GaMnN), and manganese in gallium phosphide (GaMnP). These materials were fabricated using variants of the molecular beam epitaxy (MBE) technique, where beams of the constituent elements are produced in a high vacuum environment. The technique allows for a wide variety of parameters to be adjusted during the material preparation. The materials were deposited on sapphire, gallium nitride, and gallium phosphide surfaces; with particular emphasis on the correlation between growth conditions and the final chemical, structural, morphological, electronic, optical, and magnetic properties. The materials were characterized using a variety of techniques. Results with the GaN:Er material indicated that several percent of Er could be successfully incorporated into the material, and that the optical emission could be increased by incorporating C impurities into the film. These impurities were found to increase the overall emission and decrease the quenching of the emission with temperature. Optical emission results for GaN:Eu indicated that this material produced a visible red emission that was brighter under optical excitation than the AlGaAs used in commercial red emitting devices. The dilute magnetic semiconductors n-GaMnN and p-GaMnP were produced for the first time by the MBE technique. The SQUID magnetometry and magnetotransport results for n-GaMnN indicated the presence of ferromagnetic ordering with a Curie temperature between 20 K and 25 K. Magnetic measurements of the p-GaMnP indicated the presence of ferromagnetic ordering to 250 K, far above the theoretically predicted value of 100 K. Similar results were also produced by the direct implantation of Mn into GaP.

Gallium phosphide high temperature diodes

NASA Technical Reports Server (NTRS)

Chaffin, R. J.; Dawson, L. R.

1981-01-01

High temperature (300 C) diodes for geothermal and other energy applications were developed. A comparison of reverse leakage currents of Si, GaAs, and GaP was made. Diodes made from GaP should be usable to 500 C. A Liquid Phase Epitaxy (LPE) process for producing high quality, grown junction GaP diodes is described. This process uses low vapor pressure Mg as a dopant which allows multiple boat growth in the same LPE run. These LPE wafers were cut into die and metallized to make the diodes. These diodes produce leakage currents below ten to the -9th power A/sq cm at 400 C while exhibiting good high temperature rectification characteristics. High temperature life test data is presented which shows exceptional stability of the V-I characteristics.

The relation of the yield stress of high-pressure anvils to the pressure attained at yielding and the ultimate attainable pressure

NASA Technical Reports Server (NTRS)

Panda, P. C.; Ruoff, A. L.

1979-01-01

A sensitive microprofilometer was used to determine the onset of yielding in the anvils of a supported opposed anvil device for the case of 3% cobalt-cemented tungsten carbide as the anvil material. In addition, it is shown how the commencement of yielding in boron carbide pistons, the yield strength being known, can be used to obtain the transition pressure to a conducting phase in gallium phosphide. The transition pressures of bismuth and gallium phosphide are obtained and it is found that these transitions are extremely close to the maximum attainable pressure in, respectively, a maraging steel and a 3% cobalt-cemented tungsten carbide.

Forward-biased current annealing of radiation degraded indium phosphide and gallium arsenide solar cells

NASA Technical Reports Server (NTRS)

Michael, Sherif; Cypranowski, Corinne; Anspaugh, Bruce

1990-01-01

The preliminary results of a novel approach to low-temperature annealing of previously irradiated indium phosphide and gallium arsenide solar cells are reported. The technique is based on forward-biased current annealing. The two types of III-V solar cells were irradiated with 1-MeV electrons to a fluence level of (1-10) x 10 to the 14th electrons/sq cm. Several annealing attempts were made, varying all conditions. Optimum annealing was achieved when cells were injected with minority currents at a constant 90 C. The current density for each type of cell was also determined. Significant recovery of degraded parameters was achieved in both cases. However, the InP cell recovery notably exceeded the recovery in GaAs cells. The recovery is thought to be caused by current-stimulated reordering of the radiator-induced displacement damage. Both types of cell were then subjected to several cycles of irradiation and annealing. The results were also very promising. The significant recovery of degraded cell parameters at low temperature might play a major role in considerably extending the end of life of future spacecraft.

Highly selective dry etching of GaP in the presence of AlxGa1–xP with a SiCl4/SF6 plasma

NASA Astrophysics Data System (ADS)

Hönl, Simon; Hahn, Herwig; Baumgartner, Yannick; Czornomaz, Lukas; Seidler, Paul

2018-05-01

We present an inductively coupled-plasma reactive-ion etching process that simultaneously provides both a high etch rate and unprecedented selectivity for gallium phosphide (GaP) in the presence of aluminum gallium phosphide (AlxGa1–xP). Utilizing mixtures of silicon tetrachloride (SiCl4) and sulfur hexafluoride (SF6), selectivities exceeding 2700:1 are achieved at GaP etch rates above 3000 nm min‑1. A design of experiments has been employed to investigate the influence of the inductively coupled-plasma power, the chamber pressure, the DC bias and the ratio of SiCl4 to SF6. The process enables the use of thin AlxGa1–xP stop layers even at aluminum contents of a few percent.

Second harmonic generation in gallium phosphide photonic crystal nanocavities with ultralow continuous wave pump power.

PubMed

Rivoire, Kelley; Lin, Ziliang; Hatami, Fariba; Masselink, W Ted; Vucković, Jelena

2009-12-07

We demonstrate second harmonic generation in photonic crystal nanocavities fabricated in the semiconductor gallium phosphide. We observe second harmonic radiation at 750 nm with input powers of only nanowatts coupled to the cavity and conversion effciency P(out)/P(2)(in,coupled)=430%/W. The large electronic band gap of GaP minimizes absorption loss, allowing effcient conversion. Our results are promising for integrated, low-power light sources and on-chip reduction of input power in other nonlinear processes.

A Mechanistic Study of CO 2 Reduction at the Interface of a Gallium Phosphide (GaP) Surface using Core-level Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Flynn, Kristen

2015-08-18

Carbon dioxide (CO 2) emission into the atmosphere has increased tremendously through burning of fossil fuels, forestry, etc.. The increased concentration has made CO 2 reductions very attractive though the reaction is considered uphill. Utilizing the sun as a potential energy source, CO 2 has the possibility to undergo six electron and four proton transfers to produce methanol, a useable resource. This reaction has been shown to occur selectively in an aqueous pyridinium solution with a gallium phosphide (GaP) electrode. Though this reaction has a high faradaic efficiency, it was unclear as to what role the GaP surface played duringmore » the reaction. In this work, we aim to address the fundamental role of GaP during the catalytic conversion, by investigating the interaction between a clean GaP surface with the reactants, products, and intermediates of this reaction using X-ray photoelectron spectroscopy. We have determined a procedure to prepare atomically clean GaP and our initial CO 2 adsorption studies have shown that there is evidence of chemisorption and reaction to form carbonate on the clean surface at LN2 temperatures (80K), in contrast to previous theoretical calculations. These findings will enable future studies on CO 2 catalysis.« less

A Mechanistic Study of CO 2 Reduction at the Interface of a Gallium Phosphide (GaP) Surface using Core-level Spectroscopy - Oral Presentation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Flynn, Kristen

2015-08-19

Carbon dioxide (CO 2) emission into the atmosphere has increased tremendously through burning of fossil fuels, forestry, etc.. The increased concentration has made CO 2 reductions very attractive though the reaction is considered uphill. Utilizing the sun as a potential energy source, CO 2 has the possibility to undergo six electron and four proton transfers to produce methanol, a useable resource. This reaction has been shown to occur selectively in an aqueous pyridinium solution with a gallium phosphide (GaP) electrode. Though this reaction has a high faradaic efficiency, it was unclear as to what role the GaP surface played duringmore » the reaction. In this work, we aim to address the fundamental role of GaP during the catalytic conversion, by investigating the interaction between a clean GaP surface with the reactants, products, and intermediates of this reaction using X-ray photoelectron spectroscopy. We have determined a procedure to prepare atomically clean GaP and our initial CO 2 adsorption studies have shown that there is evidence of chemisorption and reaction to form carbonate on the clean surface at LN2 temperatures (80K), in contrast to previous theoretical calculations. These findings will enable future studies on CO 2 catalysis.« less

Isoelectronic Traps in Gallium Phosphide

NASA Astrophysics Data System (ADS)

Christian, Theresa; Alberi, Kirstin; Beaton, Daniel; Fluegel, Brian; Mascarenhas, Angelo

2015-03-01

Isoelectronic substitutional dopants can result in strongly localized exciton traps within a host bandstructure such as gallium arsenide (GaAs) or gallium phosphide (GaP). These traps have received great attention for their role in the anomalous bandgap bowing of nitrogen or bismuth-doped GaAs, creating the dramatic bandgap tunability of these unusual dilute alloys. In the wider, indirect-bandgap host material GaP, these same isoelectronic dopants create bound states within the gap that can have very high radiative efficiency and a wealth of discrete spectral transitions illuminating the symmetry of the localized excitonic trap state. We will present a comparative study of nitrogen and bismuth isoelectronic traps in GaP. Research was supported by the U. S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division under contract DE-AC36-08GO28308 and by the Department of Energy Office of Science Graduate Fellowship Program (DOE SCGF), made possible in part by the American Recovery and Reinvestment Act of 2009, administered by ORISE-ORAU under contract no. DE-AC05-06OR23100.

Electronic properties of hexagonal gallium phosphide: A DFT investigation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Vipin; Shah, Esha V.; Roy, Debesh R., E-mail: drr@ashd.svnit.ac.in

2016-05-23

A detail density functional investigation is performed to develop hexagonal 2D gallium phosphide material. The geometry, band structure and density of states (total and projected) of 2D hexagonal GaP are reported in detail. It is heartening to note that the developed material is identified as an indirect band gap semiconductor. The indirect gap for this material is predicted as 1.97 eV at K-Γ, and a direct gap of 2.28 eV at K point is achieved, which is very close to the reported direct band gap for zinc blende and buckled structures of GaP.

Low resistance contacts for shallow junction semiconductors

NASA Technical Reports Server (NTRS)

Fatemi, Navid S. (Inventor); Weizer, Victor G. (Inventor)

1994-01-01

A method of enhancing the specific contact resistivity in InP semiconductor devices and improved devices produced thereby are disclosed. Low resistivity values are obtained by using gold ohmic contacts that contain small amounts of gallium or indium and by depositing a thin gold phosphide interlayer between the surface of the InP device and the ohmic contact. When both the thin interlayer and the gold-gallium or gold-indium contact metallizations are used, ultra low specific contact resistivities are achieved. Thermal stability with good contact resistivity is achieved by depositing a layer of refractory metal over the gold phosphide interlayer.

Lattice Matched Iii-V IV Semiconductor Heterostructures: Metalorganic Chemical Vapor Deposition and Remote Plasma Enhanced Chemical Vapor Deposition.

NASA Astrophysics Data System (ADS)

Choi, Sungwoo

1992-01-01

This thesis describes the growth and characterization of wide gap III-V compound semiconductors such as aluminum gallium arsenide (Al_{rm x} Ga_{rm 1-x}As), gallium nitride (GaN), and gallium phosphide (GaP), deposited by the metalorganic chemical vapor deposition (MOCVD) and remote plasma enhanced chemical vapor deposition (Remote PECVD). In the first part of the thesis, the optimization of GaAs and Al_{rm x}Ga _{rm 1-x}As hetero -epitaxial layers on Ge substrates is described in the context of the application in the construction of cascade solar cells. The emphasis on this study is on the trade-offs in the choice of the temperature related to increasing interdiffusion/autodoping and increasing perfection of the epilayer with increasing temperature. The structural, chemical, optical, and electrical properties of the heterostructures are characterized by x-ray rocking curve measurement, scanning electron microscopy (SEM), electron beam induced current (EBIC), cross-sectional transmission electron microscopy (X-TEM), Raman spectroscopy, secondary ion mass spectrometry (SIMS), and steady-state and time-resolved photoluminescence (PL). Based on the results of this work the optimum growth temperature is 720^circC. The second part of the thesis describes the growth of GaN and GaP layers on silicon and sapphire substrates and the homoepitaxy of GaP by remote PECVD. I have designed and built an ultra high vacuum (UHV) deposition system which includes: the gas supply system, the pumping system, the deposition chamber, the load-lock chamber, and the waste disposal system. The work on the deposition of GaN on Si and sapphire focuses onto the understanding of the growth kinetics. In addition, Auger electron spectroscopy (AES) for surface analysis, x-ray diffraction methods and microscopic analyses using SEM and TEM for structural characterization, infrared (IR) and ultraviolet (UV) absorption measurements for optical characterization, and electrical characterization results on the GaN films are presented. In the deposition GaP thin films by remote PECVD, trimethylgallium and in-situ generated phosphine precursors are employed as source gases which permits homo- and heteroepitaxial growth as substrate temperature of 590-620^ circC. Also, the growth kinetics of gallium phosphide is discussed. As in the case of GaN, the surface, structural, chemical, optical, and electrical properties are characterized and the results are discussed.

Molybdenum Disulfide as a Protection Layer and Catalyst for Gallium Indium Phosphide Solar Water Splitting Photocathodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Britto, Reuben J.; Benck, Jesse D.; Young, James L.

2016-06-02

Gallium indium phosphide (GaInP2) is a semiconductor with promising optical and electronic properties for solar water splitting, but its surface stability is problematic as it undergoes significant chemical and electrochemical corrosion in aqueous electrolytes. Molybdenum disulfide (MoS2) nanomaterials are promising to both protect GaInP2 and to improve catalysis since MoS2 is resistant to corrosion and also possesses high activity for the hydrogen evolution reaction (HER). In this work, we demonstrate that GaInP2 photocathodes coated with thin MoS2 surface protecting layers exhibit excellent activity and stability for solar hydrogen production, with no loss in performance (photocurrent onset potential, fill factor, andmore » light limited current density) after 60 hours of operation. This represents a five-hundred fold increase in stability compared to bare p-GaInP2 samples tested in identical conditions.« less

Advanced high temperature thermoelectrics for space power

NASA Technical Reports Server (NTRS)

Lockwood, A.; Ewell, R.; Wood, C.

1981-01-01

Preliminary results from a spacecraft system study show that an optimum hot junction temperature is in the range of 1500 K for advanced nuclear reactor technology combined with thermoelectric conversion. Advanced silicon germanium thermoelectric conversion is feasible if hot junction temperatures can be raised roughly 100 C or if gallium phosphide can be used to improve the figure of merit, but the performance is marginal. Two new classes of refractory materials, rare earth sulfides and boron-carbon alloys, are being investigated to improve the specific weight of the generator system. Preliminary data on the sulfides have shown very high figures of merit over short temperature ranges. Both n- and p-type doping have been obtained. Pure boron-carbide may extrapolate to high figure of merit at temperatures well above 1500 K but not lower temperature; n-type conduction has been reported by others, but not yet observed in the JPL program. Inadvertant impurity doping may explain the divergence of results reported.

Optical Computing, 1991, Technical Digest Series, Vol. 6

DTIC Science & Technology

1992-05-22

lasers). Compound semiconductors may satisfy these requirements. For example, optical signal amplification by two-beam coupling and amplified phase... compound semiconductors can provide this type of implementationi. This paper presents results from a detailed investigation on potentials of the...conductivity to achieve high multichannel cell performance. We describe several high performance Gallium Phosphide multichannel Bragg cells which employ these

A combined kick-out and dissociative diffusion mechanism of grown-in Be in InGaAs and InGaAsP. A new finite difference-Bairstow method for solution of the diffusion equations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koumetz, Serge D., E-mail: Serge.Koumetz@univ-rouen.fr; Martin, Patrick; Murray, Hugues

Experimental results on the diffusion of grown-in beryllium (Be) in indium gallium arsenide (In{sub 0.53}Ga{sub 0.47}As) and indium gallium arsenide phosphide (In{sub 0.73}Ga{sub 0.27}As{sub 0.58}P{sub 0.42}) gas source molecular beam epitaxy alloys lattice-matched to indium phosphide (InP) can be successfully explained in terms of a combined kick-out and dissociative diffusion mechanism, involving neutral Be interstitials (Be{sub i}{sup 0}), singly positively charged gallium (Ga), indium (In) self-interstitials (I{sub III}{sup +}) and singly positively charged Ga, In vacancies (V{sub III}{sup +}). A new numerical method of solution to the system of diffusion equations, based on the finite difference approximations and Bairstow's method,more » is proposed.« less

Wavelength-scale Microlasers based on VCSEL-Photonic Crystal Architecture

DTIC Science & Technology

2015-01-20

molecular beam epitaxy , MBE). We will also assume the triangular lattice of air...Abbreviations, and Acronyms InP: indium phosphide InGaAsP: indium gallium arsenide phosphide MBE: molecular beam epiitaxy VCSEL : vertical cavity...substrates and were grown by MBE. Electron beam lithography and reactive ion etching was used to deep‐etch the holes of the PhC‐ VCSELS ,

Ellipsometric analysis and optical absorption characterization of gallium phosphide nanoparticulate thin film

NASA Astrophysics Data System (ADS)

Zhang, Qi-Xian; Wei, Wen-Sheng; Ruan, Fang-Ping

2011-04-01

Gallium phosphide (GaP) nanoparticulate thin films were easily fabricated by colloidal suspension deposition via GaP nanoparticles dispersed in N,N-dimethylformamide. The microstructure of the film was performed by x-ray diffraction, high resolution transmission electron microscopy and field emission scanning electron microscopy. The film was further investigated by spectroscopic ellipsometry. After the model GaP+void|SiO2 was built and an effective medium approximation was adopted, the values of the refractive index n and the extinction coefficient k were calculated for the energy range of 0.75 eV-4.0 eV using the dispersion formula in DeltaPsi2 software. The absorption coefficient of the film was calculated from its k and its energy gaps were further estimated according to the Tauc equation, which were further verified by its fluorescence spectrum measurement. The structure and optical absorption properties of the nanoparticulate films are promising for their potential applications in hybrid solar cells.

Growth of indium gallium arsenide thin film on silicon substrate by MOCVD technique

NASA Astrophysics Data System (ADS)

Chowdhury, Sisir; Das, Anish; Banerji, Pallab

2018-05-01

Indium gallium arsenide (InGaAs) thin film with indium phosphide (InP) buffer has been grown on p-type silicon (100) by Metal Organic Chemical Vapor Deposition (MOCVD) technique. To get a lattice matched substrate an Indium Phosphide buffer thin film is deposited onto Si substrate prior to InGaAs growth. The grown films have been investigated by UV-Vis-NIR reflectance spectroscopy. The band gap energy of the grown InGaAs thin films determined to be 0.82 eV from reflectance spectrum and the films are found to have same thickness for growth between 600 °C and 650 °C. Crystalline quality of the grown films has been studied by grazing incidence X-ray diffractometry (GIXRD).

Hydrazine-Assisted Formation of Indium Phosphide (InP)-Based Nanowires and Core-Shell Composites

PubMed Central

Patzke, Greta R.; Kontic, Roman; Shiolashvili, Zeinab; Makhatadze, Nino; Jishiashvili, David

2012-01-01

Indium phosphide nanowires (InP NWs) are accessible at 440 °C from a novel vapor phase deposition approach from crystalline InP sources in hydrazine atmospheres containing 3 mol % H2O. Uniform zinc blende (ZB) InP NWs with diameters around 20 nm and lengths up to several tens of micrometers are preferably deposited on Si substrates. InP particle sizes further increase with the deposition temperature. The straightforward protocol was extended on the one-step formation of new core-shell InP–Ga NWs from mixed InP/Ga source materials. Composite nanocables with diameters below 20 nm and shells of amorphous gallium oxide are obtained at low deposition temperatures around 350 °C. Furthermore, InP/Zn sources afford InP NWs with amorphous Zn/P/O-coatings at slightly higher temperatures (400 °C) from analogous setups. At 450 °C, the smooth outer layer of InP-Zn NWs is transformed into bead-shaped coatings. The novel combinations of the key semiconductor InP with isotropic insulator shell materials open up interesting application perspectives in nanoelectronics. PMID:28809296

Hydrazine-Assisted Formation of Indium Phosphide (InP)-Based Nanowires and Core-Shell Composites.

PubMed

Patzke, Greta R; Kontic, Roman; Shiolashvili, Zeinab; Makhatadze, Nino; Jishiashvili, David

2012-12-27

Indium phosphide nanowires (InP NWs) are accessible at 440 °C from a novel vapor phase deposition approach from crystalline InP sources in hydrazine atmospheres containing 3 mol % H₂O. Uniform zinc blende (ZB) InP NWs with diameters around 20 nm and lengths up to several tens of micrometers are preferably deposited on Si substrates. InP particle sizes further increase with the deposition temperature. The straightforward protocol was extended on the one-step formation of new core-shell InP-Ga NWs from mixed InP/Ga source materials. Composite nanocables with diameters below 20 nm and shells of amorphous gallium oxide are obtained at low deposition temperatures around 350 °C. Furthermore, InP/Zn sources afford InP NWs with amorphous Zn/P/O-coatings at slightly higher temperatures (400 °C) from analogous setups. At 450 °C, the smooth outer layer of InP-Zn NWs is transformed into bead-shaped coatings. The novel combinations of the key semiconductor InP with isotropic insulator shell materials open up interesting application perspectives in nanoelectronics.

GaAsP on GaP top solar cells

NASA Technical Reports Server (NTRS)

Mcneely, J. B.; Negley, G. H.; Barnett, A. M.

1985-01-01

GaAsP on GaP top solar cells as an attachment to silicon bottom solar cells are being developed. The GaAsP on GaP system offers several advantages for this top solar cell. The most important is that the gallium phosphide substrate provides a rugged, transparent mechanical substrate which does not have to be removed or thinned during processing. Additional advantages are that: (1) gallium phosphide is more oxidation resistant than the III-V aluminum compounds, (2) a range of energy band gaps higher than 1.75 eV is readily available for system efficiency optimization, (3) reliable ohmic contact technology is available from the light-emitting diode industry, and (4) the system readily lends itself to graded band gap structures for additional increases in efficiency.

Radiation-acoustic treatment of gallium phosphide light diodes

NASA Astrophysics Data System (ADS)

Tartachnik, Volodimir P.; Gontaruk, Olexsandr M.; Vernydub, Roman M.; Kryvutenko, Anatoly M.; Olikh, Yaroslav M.; Opilat, Vitalij Y.; Petrenko, Igor V.; Pinkovska, Myroslava B.

1999-11-01

The ultrasound influence on the defects of technological and radiation origin of GaP light diodes has been investigated. GaP light diodes were treated by ultrasound wave in different operating modes. Electroluminescence spectra were measured at room and low temperatures, integrated luminosity of devices was checked by solar cell. In order to find out the radiation field influence on non-equilibrium defects of acoustic origin samples were irradiated at room temperature by gamma rays of Co60. It has been discovered that in GaP light diodes treated by ultrasound unstable at room temperature dislocation networks occur at the volume of crystal. Ultrasound dose increase causes the creation of complex defects with high relaxation time and appearing of a part of more mobile defect,s which relax quicker. The nature of effects discovered has been discussed. The method of the emissive capacity restoring of samples degraded after irradiation have been proposed.

Direct Band Gap Wurtzite Gallium Phosphide Nanowires

PubMed Central

2013-01-01

The main challenge for light-emitting diodes is to increase the efficiency in the green part of the spectrum. Gallium phosphide (GaP) with the normal cubic crystal structure has an indirect band gap, which severely limits the green emission efficiency. Band structure calculations have predicted a direct band gap for wurtzite GaP. Here, we report the fabrication of GaP nanowires with pure hexagonal crystal structure and demonstrate the direct nature of the band gap. We observe strong photoluminescence at a wavelength of 594 nm with short lifetime, typical for a direct band gap. Furthermore, by incorporation of aluminum or arsenic in the GaP nanowires, the emitted wavelength is tuned across an important range of the visible light spectrum (555–690 nm). This approach of crystal structure engineering enables new pathways to tailor materials properties enhancing the functionality. PMID:23464761

ANALYSIS OF THE WATER-SPLITTING CAPABILITIES OF GALLIUM INDIUM PHOSPHIDE NITRIDE (GaInPN)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Head, J.; Turner, J.

2007-01-01

With increasing demand for oil, the fossil fuels used to power society’s vehicles and homes are becoming harder to obtain, creating pollution problems and posing hazard’s to people’s health. Hydrogen, a clean and effi cient energy carrier, is one alternative to fossil fuels. Certain semiconductors are able to harness the energy of solar photons and direct it into water electrolysis in a process known as photoelectrochemical water-splitting. P-type gallium indium phosphide (p-GaInP2) in tandem with GaAs is a semiconductor system that exhibits water-splitting capabilities with a solar-tohydrogen effi ciency of 12.4%. Although this material is effi cient at producing hydrogenmore » through photoelectrolysis it has been shown to be unstable in solution. By introducing nitrogen into this material, there is great potential for enhanced stability. In this study, gallium indium phosphide nitride Ga1-yInyP1-xNx samples were grown using metal-organic chemical vapor deposition in an atmospheric-pressure vertical reactor. Photocurrent spectroscopy determined these materials to have a direct band gap around 2.0eV. Mott-Schottky analysis indicated p-type behavior with variation in fl atband potentials with varied frequencies and pH’s of solutions. Photocurrent onset and illuminated open circuit potential measurements correlated to fl atband potentials determined from previous studies. Durability analysis suggested improved stability over the GaInP2 system.« less

Measuring the Dispersion in Laser Cavity Mirrors using White-Light Interferometry

DTIC Science & Technology

2008-03-01

mirrors. Two AlGaInP (aluminum gallium indium phosphide ) diode lasers are aligned such that one is polarized vertically while one is polarized...linear crystals, where the index of refraction depends on beam intensity. Short pulses with high peak intensities are well 14 suited to induce the...MEASURING THE DISPERSION OF LASER CAVITY MIRRORS USING WHITE-LIGHT INTERFEROMETRY THESIS Allison S

Boron Arsenide and Boron Phosphide for High Temperature and Luminescent Devices. [semiconductor devices - crystal growth/crystal structure

NASA Technical Reports Server (NTRS)

Chu, T. L.

1975-01-01

The crystal growth of boron arsenide and boron phosphide in the form of bulk crystals and epitaxial layers on suitable substrates is discussed. The physical, chemical, and electrical properties of the crystals and epitaxial layers are examined. Bulk crystals of boron arsenide were prepared by the chemical transport technique, and their carrier concentration and Hall mobility were measured. The growth of boron arsenide crystals from high temperature solutions was attempted without success. Bulk crystals of boron phosphide were also prepared by chemical transport and solution growth techniques. Techniques required for the fabrication of boron phosphide devices such as junction shaping, diffusion, and contact formation were investigated. Alloying techniques were developed for the formation of low-resistance ohmic contacts to boron phosphide. Four types of boron phosphide devices were fabricated: (1) metal-insulator-boron phosphide structures, (2) Schottky barriers; (3) boron phosphide-silicon carbide heterojunctions; and (4) p-n homojunctions. Easily visible red electroluminescence was observed from both epitaxial and solution grown p-n junctions.

High-efficiency solar cell and method for fabrication

DOEpatents

Hou, Hong Q.; Reinhardt, Kitt C.

1999-01-01

A high-efficiency 3- or 4-junction solar cell is disclosed with a theoretical AM0 energy conversion efficiency of about 40%. The solar cell includes p-n junctions formed from indium gallium arsenide nitride (InGaAsN), gallium arsenide (GaAs) and indium gallium aluminum phosphide (InGaAlP) separated by n-p tunnel junctions. An optional germanium (Ge) p-n junction can be formed in the substrate upon which the other p-n junctions are grown. The bandgap energies for each p-n junction are tailored to provide substantially equal short-circuit currents for each p-n junction, thereby eliminating current bottlenecks and improving the overall energy conversion efficiency of the solar cell. Additionally, the use of an InGaAsN p-n junction overcomes super-bandgap energy losses that are present in conventional multi-junction solar cells. A method is also disclosed for fabricating the high-efficiency 3- or 4-junction solar cell by metal-organic chemical vapor deposition (MOCVD).

High-efficiency solar cell and method for fabrication

DOEpatents

Hou, H.Q.; Reinhardt, K.C.

1999-08-31

A high-efficiency 3- or 4-junction solar cell is disclosed with a theoretical AM0 energy conversion efficiency of about 40%. The solar cell includes p-n junctions formed from indium gallium arsenide nitride (InGaAsN), gallium arsenide (GaAs) and indium gallium aluminum phosphide (InGaAlP) separated by n-p tunnel junctions. An optional germanium (Ge) p-n junction can be formed in the substrate upon which the other p-n junctions are grown. The bandgap energies for each p-n junction are tailored to provide substantially equal short-circuit currents for each p-n junction, thereby eliminating current bottlenecks and improving the overall energy conversion efficiency of the solar cell. Additionally, the use of an InGaAsN p-n junction overcomes super-bandgap energy losses that are present in conventional multi-junction solar cells. A method is also disclosed for fabricating the high-efficiency 3- or 4-junction solar cell by metal-organic chemical vapor deposition (MOCVD). 4 figs.

One-Step Facile Synthesis of Cobalt Phosphides for Hydrogen Evolution Reaction Catalysts in Acidic and Alkaline Medium.

PubMed

Sumboja, Afriyanti; An, Tao; Goh, Hai Yang; Lübke, Mechthild; Howard, Dougal Peter; Xu, Yijie; Handoko, Albertus Denny; Zong, Yun; Liu, Zhaolin

2018-05-09

Catalysts for hydrogen evolution reaction are in demand to realize the efficient conversion of hydrogen via water electrolysis. In this work, cobalt phosphides were prepared using a one-step, scalable, and direct gas-solid phosphidation of commercially available cobalt salts. It was found that the effectiveness of the phosphidation reaction was closely related to the state of cobalt precursors at the reaction temperature. For instance, a high yield of cobalt phosphides obtained from the phosphidation of cobalt(II) acetate was related to the good stability of cobalt salt at the phosphidation temperature. On the other hand, easily oxidizable salts (e.g., cobalt(II) acetylacetonate) tended to produce a low amount of cobalt phosphides and a large content of metallic cobalt. The as-synthesized cobalt phosphides were in nanostructures with large catalytic surface areas. The catalyst prepared from phosphidation of cobalt(II) acetate exhibited an improved catalytic activity as compared to its counterpart derived from phosphidation of cobalt(II) acetylacetonate, showing an overpotential of 160 and 175 mV in acidic and alkaline electrolytes, respectively. Both catalysts also displayed an enhanced long-term stability, especially in the alkaline electrolyte. This study illustrates the direct phosphidation behavior of cobalt salts, which serve as a good vantage point in realizing the large-scale synthesis of transition-metal phosphides for high-performance electrocatalysts.

Solar cells with gallium phosphide/silicon heterojunction

NASA Astrophysics Data System (ADS)

Darnon, Maxime; Varache, Renaud; Descazeaux, Médéric; Quinci, Thomas; Martin, Mickaël; Baron, Thierry; Muñoz, Delfina

2015-09-01

One of the limitations of current amorphous silicon/crystalline silicon heterojunction solar cells is electrical and optical losses in the front transparent conductive oxide and amorphous silicon layers that limit the short circuit current. We propose to grow a thin (5 to 20 nm) crystalline Gallium Phosphide (GaP) by epitaxy on silicon to form a more transparent and more conducting emitter in place of the front amorphous silicon layers. We show that a transparent conducting oxide (TCO) is still necessary to laterally collect the current with thin GaP emitter. Larger contact resistance of GaP/TCO increases the series resistance compared to amorphous silicon. With the current process, losses in the IR region associated with silicon degradation during the surface preparation preceding GaP deposition counterbalance the gain from the UV region. A first cell efficiency of 9% has been obtained on ˜5×5 cm2 polished samples.

Fabrication and properties of gallium phosphide variable colour displays

NASA Technical Reports Server (NTRS)

Effer, D.; Macdonald, R. A.; Macgregor, G. M.; Webb, W. A.; Kennedy, D. I.

1973-01-01

The unique properties of single-junction gallium phosphide devices incorporating both red and green radiative recombination centers were investigated in application to the fabrication of monolithic 5 x 7 displays capable of displaying symbolic and alphanumeric information in a multicolor format. A number of potentially suitable material preparation techniques were evaluated in terms of both material properties and device performance. Optimum results were obtained for double liquid-phase-epitaxial process in which an open-tube dipping technique was used for n-layer growth and a sealed tipping procedure for subsequent p-layer growth. It was demonstrated that to prepare devices exhibiting a satisfactory range of dominant wavelengths which can be perceived as distinct emission colors extending from the red through green region of the visible spectrum involves a compromise between the material properties necessary for efficient red emission and those considered optimum for efficient green emission.

Process Development of Gallium Nitride Phosphide Core-Shell Nanowire Array Solar Cell

NASA Astrophysics Data System (ADS)

Chuang, Chen

Dilute Nitride GaNP is a promising materials for opto-electronic applications due to its band gap tunability. The efficiency of GaNxP1-x /GaNyP1-y core-shell nanowire solar cell (NWSC) is expected to reach as high as 44% by 1% N and 9% N in the core and shell, respectively. By developing such high efficiency NWSCs on silicon substrate, a further reduction of the cost of solar photovoltaic can be further reduced to 61$/MWh, which is competitive to levelized cost of electricity (LCOE) of fossil fuels. Therefore, a suitable NWSC structure and fabrication process need to be developed to achieve this promising NWSC. This thesis is devoted to the study on the development of fabrication process of GaNxP 1-x/GaNyP1-y core-shell Nanowire solar cell. The thesis is divided into two major parts. In the first parts, previously grown GaP/GaNyP1-y core-shell nanowire samples are used to develop the fabrication process of Gallium Nitride Phosphide nanowire solar cell. The design for nanowire arrays, passivation layer, polymeric filler spacer, transparent col- lecting layer and metal contact are discussed and fabricated. The property of these NWSCs are also characterized to point out the future development of Gal- lium Nitride Phosphide NWSC. In the second part, a nano-hole template made by nanosphere lithography is studied for selective area growth of nanowires to improve the structure of core-shell NWSC. The fabrication process of nano-hole templates and the results are presented. To have a consistent features of nano-hole tem- plate, the Taguchi Method is used to optimize the fabrication process of nano-hole templates.

Performance characterization of mid-infrared difference frequency generation in orientation-patterned gallium phosphide

NASA Astrophysics Data System (ADS)

Wei, Junxiong; Chaitanya Kumar, S.; Ye, Hanyu; Schunemann, Peter G.; Ebrahim-Zadeh, M.

2018-02-01

Orientation-patterned gallium phosphide (OP-GaP) is a recently developed nonlinear material with wide transparency across 0.8-12 μm and high nonlinearity (d14 70 pm/V), which is a promising candidate material for mid-infrared generation. Here we report the full performance characterization of a tunable single-pass nanosecond difference frequency generation (DFG) source based on OP-GaP by mixing the output of a Q-switched Nd:YAG laser at 1.064 μm with the signal from a pulsed MgO:PPLN OPO pumped by the same laser. Using the longest OP-GaP crystal (40 mm) deployed to date, the DFG source provides up to 14 mW of average output power at 2719 nm at 80 kHz repetition rate, with >6 mW across 2492-2782 nm, in TEM00 spatial profile. By performing relevant measurements, detrimental issues such as residual absorption and thermal effects have been studied and confirmed. The temperature and spectral acceptance bandwidths for DFG in the 40-mm-log OP-GaP are measured to be 18 °C and 17 nm, respectively, at 1766 nm. The DFG beam exhibits passive power stability better than 1.7% rms over 1.4 hours at 2774 nm, compared to 1.6% and 0.1% rms for the signal and pump, respectively. The polarization dependence of the input beams on the DFG power has also been systematically investigated, for the first time to our knowledge. Further, we have measured the damage threshold of the OP-GaP crystal to be 0.8 J/cm2 at 1064 nm.

A study to investigate the chemical stability of gallium phosphate oxide/gallium arsenide phosphide

NASA Technical Reports Server (NTRS)

Kuhlman, G. J.

1979-01-01

The elemental composition with depth into the oxide films was examined using secondary ion mass spectrometry. Results indicate that the layers are arsenic-deficient through the bulk of the oxide and arsenic-rich near both the oxide surface and the oxide-semiconductor interface region. Phosphorus is incorporated into the oxide in an approximately uniform manner. The MIS capacitor structures exhibited deep-depletion characteristics and hysteresis indicative of electron trapping at the oxide-semiconductor interface. Post-oxidation annealing of the films in argon or nitrogen generally results in slightly increased dielectric leakage currents and decreased C-V hysteresis effects, and is associated with arsenic loss at the oxide surface. The results of bias-temperature stress experiments indicate that the major instability effects are due to changes in the electron trapping behavior. No changes were observed in the elemental profiles following electrical stressing, indicating that the grown films are chemically stable under device operating conditions.

Low-Resistivity Zinc Selenide for Heterojunctions

NASA Technical Reports Server (NTRS)

Stirn, R. J.

1986-01-01

Magnetron reactive sputtering enables doping of this semiconductor. Proposed method of reactive sputtering combined with doping shows potential for yielding low-resistivity zinc selenide films. Zinc selenide attractive material for forming heterojunctions with other semiconductor compounds as zinc phosphide, cadmium telluride, and gallium arsenide. Semiconductor junctions promising for future optoelectronic devices, including solar cells and electroluminescent displays. Resistivities of zinc selenide layers deposited by evaporation or chemical vapor deposition too high to form practical heterojunctions.

Gallium Phosphide Integrated with Silicon Heterojunction Solar Cells

NASA Astrophysics Data System (ADS)

Zhang, Chaomin

It has been a long-standing goal to epitaxially integrate III-V alloys with Si substrates which can enable low-cost microelectronic and optoelectronic systems. Among the III-V alloys, gallium phosphide (GaP) is a strong candidate, especially for solar cells applications. Gallium phosphide with small lattice mismatch ( 0.4%) to Si enables coherent/pseudomorphic epitaxial growth with little crystalline defect creation. The band offset between Si and GaP suggests that GaP can function as an electron-selective contact, and it has been theoretically shown that GaP/Si integrated solar cells have the potential to overcome the limitations of common a-Si based heterojunction (SHJ) solar cells. Despite the promising potential of GaP/Si heterojunction solar cells, there are two main obstacles to realize high performance photovoltaic devices from this structure. First, the growth of the polar material (GaP) on the non-polar material (Si) is a challenge in how to suppress the formation of structural defects, such as anti-phase domains (APD). Further, it is widely observed that the minority-carrier lifetime of the Si substrates is significantly decreased during epitaxially growth of GaP on Si. In this dissertation, two different GaP growth methods were compared and analyzed, including migration-enhanced epitaxy (MEE) and traditional molecular beam epitaxy (MBE). High quality GaP can be realized on precisely oriented (001) Si substrates by MBE growth, and the investigation of structural defect creation in the GaP/Si epitaxial structures was conducted using high resolution X-ray diffraction (HRXRD) and high resolution transmission electron microscopy (HRTEM). The mechanisms responsible for lifetime degradation were further investigated, and it was found that external fast diffusors are the origin for the degradation. Two practical approaches including the use of both a SiNx diffusion barrier layer and P-diffused layers, to suppress the Si minority-carrier lifetime degradation during GaP epitaxial growth on Si by MBE were proposed. To achieve high performance of GaP/Si solar cells, different GaP/Si structures were designed, fabricated and compared, including GaP as a hetero-emitter, GaP as a heterojunction on the rear side, inserting passivation membrane layers at the GaP/Si interface, and GaP/wet-oxide functioning as a passivation contact. A designed of a-Si free carrier-selective contact MoOx/Si/GaP solar cells demonstrated 14.1% power conversion efficiency.

Method for the preparation of inorganic single crystal and polycrystalline electronic materials

NASA Technical Reports Server (NTRS)

Groves, W. O. (Inventor)

1969-01-01

Large area, semiconductor crystals selected from group 3-5 compounds and alloys are provided for semiconductor device fabrication by the use of a selective etching operation which completely removes the substrate on which the desired crystal was deposited. The substrate, selected from the same group as the single crystal, has a higher solution rate than the epitaxial single crystal which is essentially unaffected by the etching solution. The preparation of gallium phosphide single crystals using a gallium arsenide substrate and a concentrated nitric acid etching solution is described.

Modeling Laser Effects on Multi-Junction Solar Cells Using Silvaco ATLAS Software for Spacecraft Power Beaming Applications

DTIC Science & Technology

2010-06-01

could not. Figure 11 shows the Indium Gallium Phosphide (InGaP)- Gallium Arsenide (GaAs)- Germanium (Ge) solar cell utilization of the solar spectrum...2 opcv nL  (4.4) p = 1, 2, 3, … nr = index of refraction of the cavity co = speed of light in a vacuum (m/s) L = cavity length (meters...illumination – ηsolar  Efficiency under solar illumination – n Number of electrons – nr Index of refraction –  Photon frequency Hz ΔFSR

High efficiency GaP power conversion for Betavoltaic applications

NASA Astrophysics Data System (ADS)

Sims, Paul E.; Dinetta, Louis C.; Barnett, Allen M.

1994-09-01

AstroPower is developing a gallium phosphide (GaP) based energy converter optimized for radio luminescent light-based power supplies. A 'two-step' or 'indirect' process is used where a phosphor is excited by radioactive decay products to produce light that is then converted to electricity by a photovoltaic energy converter. This indirect conversion of beta-radiation to electrical energy can be realized by applying recent developments in tritium based radio luminescent (RL) light sources in combination with the high conversion efficiencies that can be achieved under low illumination with low leakage, gallium phosphide based devices. This tritium to light approach is inherently safer than battery designs that incorporate high activity radionuclides because the beta particles emitted by tritium are of low average energy and are easily stopped by a thin layer of glass. GaP layers were grown by liquid phase epitaxy and p/n junction devices were fabricated and characterized for low light intensity power conversion. AstroPower has demonstrated the feasibility of the GaP based energy converter with the following key results: 23.54 percent conversion efficiency under 968 muW/sq cm 440 nm blue light, 14.59 percent conversion efficiency for 2.85 muW/sq cm 440 nm blue light, and fabrication of working 5 V array. We have also determined that at least 20 muW/sq cm optical power is available for betavoltaic power systems. Successful developments of this device is an enabling technology for low volume, safe, high voltage, milliwatt power supplies with service lifetimes in excess of 12 years.

High efficiency GaP power conversion for Betavoltaic applications

NASA Technical Reports Server (NTRS)

Sims, Paul E.; Dinetta, Louis C.; Barnett, Allen M.

1994-01-01

AstroPower is developing a gallium phosphide (GaP) based energy converter optimized for radio luminescent light-based power supplies. A 'two-step' or 'indirect' process is used where a phosphor is excited by radioactive decay products to produce light that is then converted to electricity by a photovoltaic energy converter. This indirect conversion of beta-radiation to electrical energy can be realized by applying recent developments in tritium based radio luminescent (RL) light sources in combination with the high conversion efficiencies that can be achieved under low illumination with low leakage, gallium phosphide based devices. This tritium to light approach is inherently safer than battery designs that incorporate high activity radionuclides because the beta particles emitted by tritium are of low average energy and are easily stopped by a thin layer of glass. GaP layers were grown by liquid phase epitaxy and p/n junction devices were fabricated and characterized for low light intensity power conversion. AstroPower has demonstrated the feasibility of the GaP based energy converter with the following key results: 23.54 percent conversion efficiency under 968 muW/sq cm 440 nm blue light, 14.59 percent conversion efficiency for 2.85 muW/sq cm 440 nm blue light, and fabrication of working 5 V array. We have also determined that at least 20 muW/sq cm optical power is available for betavoltaic power systems. Successful developments of this device is an enabling technology for low volume, safe, high voltage, milliwatt power supplies with service lifetimes in excess of 12 years.

Diffusion length variation in 0.5- and 3-MeV-proton-irradiated, heteroepitaxial indium phosphide solar cells

NASA Technical Reports Server (NTRS)

Jain, Raj K.; Weinberg, Irving; Flood, Dennis J.

1993-01-01

Indium phosphide (InP) solar cells are more radiation resistant than gallium arsenide (GaAs) and silicon (Si) solar cells, and their growth by heteroepitaxy offers additional advantages leading to the development of light weight, mechanically strong, and cost-effective cells. Changes in heteroepitaxial InP cell efficiency under 0.5- and 3-MeV proton irradiations have been explained by the variation in the minority-carrier diffusion length. The base diffusion length versus proton fluence was calculated by simulating the cell performance. The diffusion length damage coefficient, K(sub L), was also plotted as a function of proton fluence.

High-performance indium gallium phosphide/gallium arsenide heterojunction bipolar transistors

NASA Astrophysics Data System (ADS)

Ahmari, David Abbas

Heterojunction bipolar transistors (HBTs) have demonstrated the high-frequency characteristics as well as the high linearity, gain, and power efficiency necessary to make them attractive for a variety of applications. Specific applications for which HBTs are well suited include amplifiers, analog-to-digital converters, current sources, and optoelectronic integrated circuits. Currently, most commercially available HBT-based integrated circuits employ the AlGaAs/GaAs material system in applications such as a 4-GHz gain block used in wireless phones. As modern systems require higher-performance and lower-cost devices, HBTs utilizing the newer, InGaP/GaAs and InP/InGaAs material systems will begin to dominate the HBT market. To enable the widespread use of InGaP/GaAs HBTs, much research on the fabrication, performance, and characterization of these devices is required. This dissertation will discuss the design and implementation of high-performance InGaP/GaAs HBTs as well as study HBT device physics and characterization.

First principle study of electronic nanoscale structure of In x Ga1- x P with variable size, shape and alloying percentage

NASA Astrophysics Data System (ADS)

Hussein, M. T.; Kasim, T.; Abdulsattar, M. A.

2013-11-01

In present work, we investigate electronic properties of alloying percentage of In x Ga1- x P compound with different sizes of superlattice large unit cell (LUC) method with 8, 16, 54, and 64 nanocrystals core atoms. The size and type of alloying compound are varied so that it can be tuned to a required application. To determine properties of indium gallium phosphide nanocrystals density functional theory at the generalized-gradient approximation level coupled with LUC method is used to simulate electronic structure of zinc blende indium gallium phosphide nanocrystals that have dimensions around 2-2.8 nm. The calculated properties include lattice constant, energy gap, valence band width, cohesive energy, density of states (DOS) etc. Results show that laws that are applied at microscale alloying percentage are no more applicable at the present nanoscale. Results also show that size, shape and quantum effects are strong. Many properties fluctuate at nanoscale while others converge to definite values. DOS summarizes many of the above quantities.

High-Efficiency Thin-Film Silicon-on-GaP Solar Cell for Improved Radiation Resistance.

DTIC Science & Technology

1987-09-01

UNCLASSIFIED MyUM 21 LIX E / 82H M D 132 11111_Lt5l1. t FILE UPI" AD-A190 268 AFWAL-TR-87-2070 HIGH-EFFICIENCY THIN- FILM SILICON-ON-GaP SOLAR CELL...EFFICIENCY THIN- FILM SILICON-ON-GaP SOLAR CELL FOR IMPROVED RADIATION RESISTANCE 12. PERSONAL AUTHOR(S) JEROME S. CULIK 13a. TYPE OF REPORT 13b. TIME...C tinue on reverse if necessary and identify by block number) 10 01 SILICONs THIN* FILM , . HETEROEPITAXIAL, RADIATION, 10 01 i GALLIUM PHOSPHIDE 19

A Facile Molecular Precursor Route to Metal Phosphide Nanoparticles and Their Evaluation as Hydrodeoxygenation Catalysts

DOE PAGES

Habas, Susan E.; Baddour, Frederick G.; Ruddy, Daniel A.; ...

2015-11-05

Metal phosphides have been identified as a promising class of materials for the catalytic upgrading of bio-oils, which are renewable and potentially inexpensive sources for liquid fuels. Herein, we report the facile synthesis of a series of solid, phase-pure metal phosphide nanoparticles (NPs) (Ni 2P, Rh 2P, and Pd 3P) utilizing commercially available, air-stable metal–phosphine complexes in a one-pot reaction. This single-source molecular precursor route provides an alternative method to access metal phosphide NPs with controlled phases and without the formation of metal NP intermediates that can lead to hollow particles. The formation of the Ni 2P NPs was shownmore » to proceed through an amorphous Ni–P intermediate, leading to the desired NP morphology and metal-rich phase. This low-temperature, rapid route to well-defined metal NPs is expected to have broad applicability to a variety of readily available or easily synthesized metal–phosphine complexes with high decomposition temperatures. Hydrodeoxygenation of acetic acid, an abundant bio-oil component, was performed to investigate H 2 activation and deoxygenation pathways under conditions that are relevant to ex situ catalytic fast pyrolysis (high temperatures, low pressures, and near-stoichiometric H 2 concentrations). The catalytic performance of the silica-supported metal phosphide NPs was compared to the analogous incipient wetness (IW) metal and metal phosphide catalysts over the range 200–500 °C. Decarbonylation was the primary pathway for H 2 incorporation in the presence of all of the catalysts except NP-Pd 3P, which exhibited minimal productive activity, and IW-Ni, which evolved H 2. The highly controlled NP-Ni2P and NP-Rh2P catalysts, which were stable under these conditions, behaved comparably to the IW-metal phosphides, with a slight shift to higher product onset temperatures, likely due to the presence of surface ligands. Most importantly, the NP-Ni 2P catalyst exhibited H 2 activation and incorporation, in contrast to IW-Ni, indicating that the behavior of the metal phosphide is significantly different from that of the parent metal, and more closely resembles that of noble metal catalysts.« less

Measurement of the Two-photon Absorption Coefficient of Gallium Phosphide (GaP) Using a Dispersion-minimized Sub-10 Femtosecond Z-scan Measurement System

DTIC Science & Technology

2012-09-01

bandwidth of the pulse. Using the standard laboratory and analysis methods of Sheik- Bahae et al., we obtain a two-photon absorption coefficient, β, of...organic thin-film materials deposited on various substrates. 15 6. References 1. Sheik- Bahae , M.; Said, A. A.; Van Stryland, E. W. High...sensitivity, Single-beam n2 Measurements. Optics Letters 1989, 14 (17). 2. Sheik- Bahae , M.; Said, A. A.; Van Stryland, E. W.; Wei, T-H; Hagan, D. J

Photovoltaic options for solar electric propulsion

NASA Technical Reports Server (NTRS)

Stella, Paul M.; Flood, Dennis J.

1990-01-01

This paper discusses both state-of-the-art and advanced development cell and array technology. Present technology includes rigid, roll-out, and foldout flexible substrate designs, with silicon and GaAs solar cells. The use of concentrator array systems is discussed based on both DOD efforts and NASA work. The benefits of advanced lightweight array technology, for both near term and far term utilization, and of advanced high efficiency thin radiation resistant cells is examined. This includes gallium arsenide/germanium, indium phosphide, and thin film devices such as copper indium disclenide.

Static photoelasticity of gallium phosphide crystals

NASA Astrophysics Data System (ADS)

Mytsyk, B. G.; Andrushchak, A. S.; Kost', Ya. P.

2012-01-01

The piezo-optic effect (POE) in cubic GaP crystals (symmetry class bar 43 m) is studied in detail by interferometry. The relations for determining the absolute piezo-optic coefficients (POCs) π im or their combinations on a sample of X/45° cut at all allowable geometries of the experiment are recorded. The determination of a specific coefficient π im at different experimental geometries on samples of right cuts and a X/45° cut made it possible to find the π im values with a high accuracy and reliability.

Electron-Hole Condensation in Semiconductors: Electrons and holes condense into freely moving liquid metallic droplets, a plasma phase with novel properties.

PubMed

Jeffries, C D

1975-09-19

In Ge and Si, and also in Ge-Si alloys (74), there is extensive evidence for the stable binding of electrons and holes into a cold plasma of constant density, which undergoes a phase separation. Liquid metallic drops 1 to 300 microm in size are formed, with lifetimes ranging from 0.1 to 600 microsec. For Ge a surprising amount is known: the phase diagram, the surface energy, the work function, the decay kinetics. Much less is known for Si. There is good agreement between theoretical and experimental values of the liquid density, the critical density, the critical temperature, and the binding energy. The stability of the liquid phase is strikingly dependent on band structure. The multivalley structure and mass anisotropy of Si, Ge, and Ge-Si, together with their indirect band gap, are no doubt responsible for the observed stability in these crystals. In the similar semiconductor gallium phosphide, drops have not yet been observed, most likely because the high impurity content traps the excitons. In gallium arsenide the existence of drops is controversial (75). Undoubtedly drops will be found to exist in other semiconductors, perhaps at even higher temperatures. This is an exciting field for the experimentalist; new phenomena are being rapidly discovered, usually before they are predicted. For the theorist, the electron-hole drop is of high intrinsic interest. It represents the first example of a quantum liquid of constant density in a periodic crystal lattice. A number of challenging experimental and theoretical problems remain.

Indium Phosphide Window Layers for Indium Gallium Arsenide Solar Cells

NASA Technical Reports Server (NTRS)

Jain, Raj K.

2005-01-01

Window layers help in reducing the surface recombination at the emitter surface of the solar cells resulting in significant improvement in energy conversion efficiency. Indium gallium arsenide (In(x)Ga(1-x)As) and related materials based solar cells are quite promising for photovoltaic and thermophotovoltaic applications. The flexibility of the change in the bandgap energy and the growth of InGaAs on different substrates make this material very attractive for multi-bandgap energy, multi-junction solar cell approaches. The high efficiency and better radiation performance of the solar cell structures based on InGaAs make them suitable for space power applications. This work investigates the suitability of indium phosphide (InP) window layers for lattice-matched In(0.53)Ga(0.47)As (bandgap energy 0.74 eV) solar cells. We present the first data on the effects of the p-type InP window layer on p-on-n lattice-matched InGaAs solar cells. The modeled quantum efficiency results show a significant improvement in the blue region with the InP window. The bare InGaAs solar cell performance suffers due to high surface recombination velocity (10(exp 7) cm/s). The large band discontinuity at the InP/InGaAs heterojunction offers a great potential barrier to minority carriers. The calculated results demonstrate that the InP window layer effectively passivates the solar cell front surface, hence resulting in reduced surface recombination and therefore, significantly improving the performance of the InGaAs solar cell.

Thermal Properties and Phonon Spectral Characterization of Synthetic Boron Phosphide for High Thermal Conductivity Applications.

PubMed

Kang, Joon Sang; Wu, Huan; Hu, Yongjie

2017-12-13

Heat dissipation is an increasingly critical technological challenge in modern electronics and photonics as devices continue to shrink to the nanoscale. To address this challenge, high thermal conductivity materials that can efficiently dissipate heat from hot spots and improve device performance are urgently needed. Boron phosphide is a unique high thermal conductivity and refractory material with exceptional chemical inertness, hardness, and high thermal stability, which holds high promises for many practical applications. So far, however, challenges with boron phosphide synthesis and characterization have hampered the understanding of its fundamental properties and potential applications. Here, we describe a systematic thermal transport study based on a synergistic synthesis-experimental-modeling approach: we have chemically synthesized high-quality boron phosphide single crystals and measured their thermal conductivity as a record-high 460 W/mK at room temperature. Through nanoscale ballistic transport, we have, for the first time, mapped the phonon spectra of boron phosphide and experimentally measured its phonon mean free-path spectra with consideration of both natural and isotope-pure abundances. We have also measured the temperature- and size-dependent thermal conductivity and performed corresponding calculations by solving the three-dimensional and spectral-dependent phonon Boltzmann transport equation using the variance-reduced Monte Carlo method. The experimental results are in good agreement with that predicted by multiscale simulations and density functional theory, which together quantify the heat conduction through the phonon mode dependent scattering process. Our finding underscores the promise of boron phosphide as a high thermal conductivity material for a wide range of applications, including thermal management and energy regulation, and provides a detailed, microscopic-level understanding of the phonon spectra and thermal transport mechanisms of boron phosphide. The present study paves the way toward the establishment of a new framework, based on the phonon spectra-material structure relationship, for the rational design of high thermal conductivity materials and nano- to multiscale devices.

Solar cells based on InP/GaP/Si structure

NASA Astrophysics Data System (ADS)

Kvitsiani, O.; Laperashvil, D.; Laperashvili, T.; Mikelashvili, V.

2016-10-01

Solar cells (SCs) based on III-V semiconductors are reviewed. Presented work emphases on the Solar Cells containing Quantum Dots (QDs) for next-generation photovoltaics. In this work the method of fabrication of InP QDs on III-V semiconductors is investigated. The original method of electrochemical deposition of metals: indium (In), gallium (Ga) and of alloys (InGa) on the surface of gallium phosphide (GaP), and mechanism of formation of InP QDs on GaP surface is presented. The possibilities of application of InP/GaP/Si structure as SC are discussed, and the challenges arising is also considered.

Sarah Kurtz | NREL

Science.gov Websites

next stage of growth for the PV industry. Participated in the demonstration of the GaInP/GaAs solar photovoltaics (PV), concentrator PV, and PV reliability. Kurtz and NREL colleague Jerry Olson championed the early use of multi-junction solar cells by showing that a top cell of gallium indium phosphide (GaInP

Semiconductor devices for optical communications in 1 micron band of wavelength. [gallium indium arsenide phosphide lasers and diodes

NASA Technical Reports Server (NTRS)

Suematsu, Y.; Iga, K.

1980-01-01

Crystal growth and the characteristics of semiconductor lasers and diodes for the long wavelength band used in optical communications are examined. It is concluded that to utilize the advantages of this band, it is necessary to have a large scale multiple wavelength communication, along with optical cumulative circuits and optical exchangers.

Electronic Structures of Free-Standing Nanowires made from Indirect Bandgap Semiconductor Gallium Phosphide

PubMed Central

Liao, Gaohua; Luo, Ning; Chen, Ke-Qiu; Xu, H. Q.

2016-01-01

We present a theoretical study of the electronic structures of freestanding nanowires made from gallium phosphide (GaP)—a III-V semiconductor with an indirect bulk bandgap. We consider [001]-oriented GaP nanowires with square and rectangular cross sections, and [111]-oriented GaP nanowires with hexagonal cross sections. Based on tight binding models, both the band structures and wave functions of the nanowires are calculated. For the [001]-oriented GaP nanowires, the bands show anti-crossing structures, while the bands of the [111]-oriented nanowires display crossing structures. Two minima are observed in the conduction bands, while the maximum of the valence bands is always at the Γ-point. Using double group theory, we analyze the symmetry properties of the lowest conduction band states and highest valence band states of GaP nanowires with different sizes and directions. The band state wave functions of the lowest conduction bands and the highest valence bands of the nanowires are evaluated by spatial probability distributions. For practical use, we fit the confinement energies of the electrons and holes in the nanowires to obtain an empirical formula. PMID:27307081

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jena, Puru; Kandalam, Anil K.; Christian, Theresa M.

Gallium phosphide bismide (GaP1-xBix) epilayers with bismuth fractions from 0.9% to 3.2%, as calculated from lattice parameter measurements, were studied with Rutherford backscattering spectrometry (RBS) to directly measure bismuth incorporation. The total bismuth fractions found by RBS were higher than expected from the lattice parameter calculations. Furthermore, in one analyzed sample grown by molecular beam epitaxy at 300 degrees C, 55% of incorporated bismuth was found to occupy interstitial sites. We discuss implications of this high interstitial incorporation fraction and its possible relationship to x-ray diffraction and photoluminescence measurements of GaP0.99Bi0.01.

Quantum Enhanced Imaging by Entangled States

DTIC Science & Technology

2009-07-01

classes of entangled states. In tripartite systems two classes of genuine tripartite entanglement have been discovered, namely, the Greenberger -Horne...D. M. Greenberger , M. Horne and A. Zeilinger, in Bell’s Theorem, Quantum Theory, and Concepts of the Universe, ed. M. Kafatos (Kluwer, Dordrecht 1989...Gallium Indium Arsenide Phosphide (a III-V compound semiconductor) GHZ: Greenberger -Horne-Zeilinger (a class of entangled states) GLAD: General

Large disparity between gallium and antimony self-diffusion in gallium antimonide.

PubMed

Bracht, H; Nicols, S P; Walukiewicz, W; Silveira, J P; Briones, F; Haller, E E

2000-11-02

The most fundamental mass transport process in solids is self-diffusion. The motion of host-lattice ('self-') atoms in solids is mediated by point defects such as vacancies or interstitial atoms, whose formation and migration enthalpies determine the kinetics of this thermally activated process. Self-diffusion studies also contribute to the understanding of the diffusion of impurities, and a quantitative understanding of self- and foreign-atom diffusion in semiconductors is central to the development of advanced electronic devices. In the past few years, self-diffusion studies have been performed successfully with isotopically controlled semiconductor heterostructures of germanium, silicon, gallium arsenide and gallium phosphide. Self-diffusion studies with isotopically controlled GaAs and GaP have been restricted to Ga self-diffusion, as only Ga has two stable isotopes, 69Ga and 71Ga. Here we report self-diffusion studies with an isotopically controlled multilayer structure of crystalline GaSb. Two stable isotopes exist for both Ga and Sb, allowing the simultaneous study of diffusion on both sublattices. Our experiments show that near the melting temperature, Ga diffuses more rapidly than Sb by over three orders of magnitude. This surprisingly large difference in atomic mobility requires a physical explanation going beyond standard diffusion models. Combining our data for Ga and Sb diffusion with related results for foreign-atom diffusion in GaSb (refs 8, 9), we conclude that the unusually slow Sb diffusion in GaSb is a consequence of reactions between defects on the Ga and Sb sublattices, which suppress the defects that are required for Sb diffusion.

Crystal growth of device quality GaAs in space

NASA Technical Reports Server (NTRS)

Gatos, H. C.; Lagowski, J.

1980-01-01

The apparatus and techniques used in effort to determine the relationships between crystal growth and electronic properties are described with emphasis on electroepitaxy and melt-grown gallium aresenide crystal. Applications of deep level transient spectroscopy, derivative photocapitance spectroscopy, and SEM-cathodoluminescene in characterizing wide bandgap semiconductors; determining photoionization in MOS, Schottky barriers, and p-n junctions; and for identifying inhomogeneities are examined, as well as the compensation of indium phosphide.

Development of advanced thermoelectric materials

NASA Technical Reports Server (NTRS)

1984-01-01

The development of an advanced thermoelectric material for radioisotope thermoelectric generator (RTG) applications is reported. A number of materials were explored. The bulk of the effort, however, was devoted to improving silicon germanium alloys by the addition of gallium phosphide, the synthesis and evaluation of lanthanum chrome sulfide and the formulation of various mixtures of lanthanum sulfide and chrome sulfide. It is found that each of these materials exhibits promise as a thermoelectric material.

Bibliography of Soviet Laser Developments. Number 71, May - June 1984.

DTIC Science & Technology

1985-08-01

d * Coumarin *o..*....... .. o... -- e. Phthalimide ...... o..... o. .. ... --- f . Cyanine .. ... .o o . .. .. .. see. --- go Xanthene...Barinova, E.Yu. (MGU). Determining the concentration of nitrogen in gallium phosphide from its photoluminescence spectrum. VMUFA, no. 3, 1984, 59-62. 23...characteristics for lasing in solutions of rhodamine 6G in a small-base resonator. OPSPA, v.56, no.5, 1984, 884-888. 5 a’ F, c. Polymethine d. Coumarin e

Direct Band Gap Gallium Antimony Phosphide (GaSbxP1−x) Alloys

PubMed Central

Russell, H. B.; Andriotis, A. N.; Menon, M.; Jasinski, J. B.; Martinez-Garcia, A.; Sunkara, M. K.

2016-01-01

Here, we report direct band gap transition for Gallium Phosphide (GaP) when alloyed with just 1–2 at% antimony (Sb) utilizing both density functional theory based computations and experiments. First principles density functional theory calculations of GaSbxP1−x alloys in a 216 atom supercell configuration indicate that an indirect to direct band gap transition occurs at x = 0.0092 or higher Sb incorporation into GaSbxP1−x. Furthermore, these calculations indicate band edge straddling of the hydrogen evolution and oxygen evolution reactions for compositions ranging from x = 0.0092 Sb up to at least x = 0.065 Sb making it a candidate for use in a Schottky type photoelectrochemical water splitting device. GaSbxP1−x nanowires were synthesized by reactive transport utilizing a microwave plasma discharge with average compositions ranging from x = 0.06 to x = 0.12 Sb and direct band gaps between 2.21 eV and 1.33 eV. Photoelectrochemical experiments show that the material is photoactive with p-type conductivity. This study brings attention to a relatively uninvestigated, tunable band gap semiconductor system with tremendous potential in many fields. PMID:26860470

Investigation of 2D photonic crystal structure based channel drop filter using quad shaped photonic crystal ring resonator for CWDM system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chhipa, Mayur Kumar, E-mail: mayurchhipa1@gmail.com; Dusad, Lalit Kumar; Rajasthan Technical University, Kota, Rajasthan

In this paper, the design & performance of two dimensional (2-D) photonic crystal structure based channel drop filter is investigated using quad shaped photonic crystal ring resonator. In this paper, Photonic Crystal (PhC) based on square lattice periodic arrays of Gallium Indium Phosphide (GaInP) rods in air structure have been investigated using Finite Difference Time Domain (FDTD) method and photonic band gap is being calculated using Plane Wave Expansion (PWE) method. The PhC designs have been optimized for telecommunication wavelength λ= 1571 nm by varying the rods lattice constant. The number of rods in Z and X directions is 21 andmore » 20, with lattice constant 0.540 nm it illustrates that the arrangement of Gallium Indium Phosphide (GaInP) rods in the structure which gives the overall size of the device around 11.4 µm × 10.8 µm. The designed filter gives good dropping efficiency using 3.298, refractive index. The designed structure is useful for CWDM systems. This device may serve as a key component in photonic integrated circuits. The device is ultra compact with the overall size around 123 µm{sup 2}.« less

Synthesis and catalytic activity of the metastable phase of gold phosphide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fernando, Deshani; Nigro, Toni A. E.; Dyer, I. D.

Recently, transition metal phosphides have found new applications as catalysts for the hydrogen evolution reaction that has generated an impetus to synthesize these materials at the nanoscale. In this work, Au2P3 was synthesized utilizing the high temperature decomposition of tri-n-octylphosphine as a source of elemental phosphorous. Gold nanorods were used as morphological templates with the aim of controlling the shape and size of the resulting gold phosphide particles. We demonstrate that the surface capping ligand of the gold nanoparticle precursors can influence the purity and extent to which the gold phosphide phase will form. Gold nanorods functionalized with 1-dodecanethiol undergomore » digestive ripening to produce discrete spherical particles that exhibit reduced reactivity towards phosphorous, resulting in low yields of the gold phosphide. In contrast, gold phosphide was obtained as a phase pure product when cetyltrimethylammonium bromide functionalized gold nanorods are used instead. The Au2P3 nanoparticles exhibited higher activity than polycrystalline gold towards the hydrogen evolution reaction.« less

Metrological-grade tunable coherent source in the mid-infrared for molecular precision spectroscopy

NASA Astrophysics Data System (ADS)

Insero, G.; Clivati, C.; D'Ambrosio, D.; Cancio Pastor, P.; Verde, M.; Schunemann, P. G.; Zondy, J.-J.; Inguscio, M.; Calonico, D.; Levi, F.; De Natale, P.; Santambrogio, G.; Borri, S.

2018-02-01

We report on a metrological-grade mid-IR source with a 10-14 short-term instability for high-precision spectroscopy. Our source is based on the combination of a quantum cascade laser and a coherent radiation obtained by difference-frequency generation in an orientation-patterned gallium phosphide (OP-GaP) crystal. The pump and signal lasers are locked to an optical frequency comb referenced to the primary frequency standard via an optical fiber link. We demonstrate the robustness of the apparatus by measuring a vibrational transition around 6 μm on a metastable state of CO molecuels with 11 digits of precision.

Controlled Electrochemical Deformation of Liquid-Phase Gallium.

PubMed

Chrimes, Adam F; Berean, Kyle J; Mitchell, Arnan; Rosengarten, Gary; Kalantar-zadeh, Kourosh

2016-02-17

Pure gallium is a soft metal with a low temperature melting point of 29.8 °C. This low melting temperature can potentially be employed for creating optical components with changeable configurations on demand by manipulating gallium in its liquid state. Gallium is a smooth and highly reflective metal that can be readily maneuvered using electric fields. These features allow gallium to be used as a reconfigurable optical reflector. This work demonstrates the use of gallium for creating reconfigurable optical reflectors manipulated through the use of electric fields when gallium is in a liquid state. The use of gallium allows the formed structures to be frozen and preserved as long as the temperature of the metal remains below its melting temperature. The lens can be readily reshaped by raising the temperature above the melting point and reapplying an electric field to produce a different curvature of the gallium reflector.

Mineral resource of the month: gallium

USGS Publications Warehouse

Jaskula, Brian W.

2009-01-01

The metal element gallium occurs in very small concentrations in rocks and ores of other metals — native gallium is not known. As society gets more and more high-tech, gallium becomes more useful. Gallium is one of only five metals that are liquid at or close to room temperature. It has one of the longest liquid ranges of any metal (29.8 degrees Celsius to 2204 degrees Celsius) and has a low vapor pressure even at high temperatures. Ultra-pure gallium has a brilliant silvery appearance, and the solid metal exhibits conchoidal fracture similar to glass.

Microwave Semiconductor Research-Materials, Devices and Circuits.

DTIC Science & Technology

1987-10-01

Quantum Well and Graded Refractive Index Separate Confinement Heterostructure Quantum Well Lasers Grown Via Molecular Beam Epitaxy" JSEP PUBLICATIONS...J.M. Ballantyne and A.J. Sievers, J. Appl. Phys., 58, 3145 (1985). 6. "Epitaxial Growth and Characterization of Indian Phosphide and Gallium Indian...Approach to Dispersion Analysis in Graded Index Optical Fiber", by H.J. Carlin and Henry Zmuda. DEGREES 1. Henry Zmuda, Ph.D., July 1984 "A New Approach

A study of the applicability of gallium arsenide and silicon carbide as aerospace sensor materials

NASA Technical Reports Server (NTRS)

Hurley, John S.

1990-01-01

Most of the piezoresistive sensors, to date, are made of silicon and germanium. Unfortunately, such materials are severly restricted in high temperature environments. By comparing the effects of temperature on the impurity concentrations and piezoresistive coefficients of silicon, gallium arsenide, and silicon carbide, it is being determined if gallium arsenide and silicon carbide are better suited materials for piezoresistive sensors in high temperature environments. The results show that the melting point for gallium arsenide prevents it from solely being used in high temperature situations, however, when used in the alloy Al(x)Ga(1-x)As, not only the advantage of the wider energy band gas is obtained, but also the higher desire melting temperature. Silicon carbide, with its wide energy band gap and higher melting temperature suggests promise as a high temperature piezoresistive sensor.

Translocation of 40 nm diameter nanowires through the intestinal epithelium of Daphnia magna

PubMed Central

Mattsson, Karin; Adolfsson, Karl; Ekvall, Mikael T.; Borgström, Magnus T.; Linse, Sara; Hansson, Lars-Anders; Cedervall, Tommy; Prinz, Christelle N.

2016-01-01

Abstract Nanowires (NWs) have unique electrical and optical properties of value for many applications including lighting, sensing, and energy harnessing. Consumer products containing NWs increase the risk of NWs being released in the environment, especially into aquatic ecosystems through sewage systems. Daphnia magna is a common, cosmopolitan freshwater organism sensitive to toxicity tests and represents a likely entry point for nanoparticles into food webs of aquatic ecosystems. Here we have evaluated the effect of NW diameter on the gut penetrance of NWs in Daphnia magna. The animals were exposed to NWs of two diameters (40 and 80 nm) and similar length (3.6 and 3.8 μm, respectively) suspended in water. In order to locate the NWs in Daphnia, the NWs were designed to comprise one inherently fluorescent segment of gallium indium phosphide (GaInP) flanked by a gallium phosphide (GaP) segment. Daphnia mortality was assessed directly after 24 h of exposure and 7 days after exposure. Translocation of NWs across the intestinal epithelium was investigated using confocal fluorescence microscopy directly after 24 h of exposure and was observed in 89% of Daphnia exposed to 40 nm NWs and in 11% of Daphnia exposed to 80 nm NWs. A high degree of fragmentation was observed for NWs of both diameters after ingestion by the Daphnia, although 40 nm NWs were fragmented to a greater extent, which could possibly facilitate translocation across the intestinal epithelium. Our results show that the feeding behavior of animals may enhance the ability of NWs to penetrate biological barriers and that penetrance is governed by the NW diameter. PMID:27181920

A new approach to synthesize supported ruthenium phosphides for hydrodesulfurization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Qingfang; Key Laboratory of Advanced Energy Materials Chemistry; Wang, Zhiqiang

2016-02-15

Highlights: • We bring out a new method to synthesize noble metal phosphides at low temperature. • Both RuP and Ru{sub 2}P were synthesized using triphenylphosphine as phosphorus sources. • Ru{sub 2}P was the better active phase for HDS than RuP and metal Ru. • RuP/SiO{sub 2} prepared by new method had better HDS activity to that by TPR method. - Abstract: Supported noble metal ruthenium phosphides were synthesized by one-step H{sub 2}-thermal treatment method using triphenylphosphine (TPP) as phosphorus sources at low temperatures. Two phosphides RuP and Ru{sub 2}P can be prepared by this method via varying the molarmore » ratio of metal salt and TPP. The as-prepared phosphides were characterized by X-ray powder diffraction (XRD), low-temperature N{sub 2} adsorption, CO chemisorption and transmission electronic microscopy (TEM). The supported ruthenium phosphides prepared by new method and conventional method together with contradistinctive metallic ruthenium were evaluated in hydrodesulfurization (HDS) of dibenzothiophene (DBT). The catalytic results showed that metal-rich Ru{sub 2}P was the better active phase for HDS than RuP and metal Ru. Besides this, ruthenium phosphide catalyst prepared by new method exhibited superior HDS activity to that prepared by conventional method.« less

Synthesis and catalytic activity of the metastable phase of gold phosphide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fernando, Deshani; Nigro, Toni A.E.; Dyer, I.D.

Recently, transition metal phosphides have found new applications as catalysts for the hydrogen evolution reaction that has generated an impetus to synthesize these materials at the nanoscale. In this work, Au{sub 2}P{sub 3} was synthesized utilizing the high temperature decomposition of tri-n-octylphosphine as a source of elemental phosphorous. Gold nanorods were used as morphological templates with the aim of controlling the shape and size of the resulting gold phosphide particles. We demonstrate that the surface capping ligand of the gold nanoparticle precursors can influence the purity and extent to which the gold phosphide phase will form. Gold nanorods functionalized withmore » 1-dodecanethiol undergo digestive ripening to produce discrete spherical particles that exhibit reduced reactivity towards phosphorous, resulting in low yields of the gold phosphide. In contrast, gold phosphide was obtained as a phase pure product when cetyltrimethylammonium bromide functionalized gold nanorods are used instead. The Au{sub 2}P{sub 3} nanoparticles exhibited higher activity than polycrystalline gold towards the hydrogen evolution reaction. - Graphical abstract: Au{sub 2}P{sub 3} was synthesized utilizing the high temperature decomposition of tri-n-octylphosphine as a source of elemental phosphorous and gold nanoparticles as reactants. We demonstrate that the surface capping ligand of the gold nanoparticle precursors influence the purity and extent to which the Au{sub 2}P{sub 3} phase will form. Gold nanorods functionalized with 1-dodecanethiol undergo digestive ripening to produce discrete spherical particles that exhibit reduced reactivity towards phosphorous, resulting in low yields of the gold phosphide. In contrast, gold phosphide was obtained as a phase pure product when cetyltrimethylammonium bromide functionalized gold nanoparticles are used instead. The Au{sub 2}P{sub 3} nanoparticles exhibited higher activity than polycrystalline gold towards the hydrogen evolution reaction. - Highlights: • The surface chemistry of gold affects the synthetic yields of Au{sub 2}P{sub 3}. • Imaging of Au{sub 2}P{sub 3} with transmission electron microscopy results in decomposition. • Au{sub 2}P{sub 3} nanoparticles exhibit activity towards the hydrogen evolution reaction.« less

Synthesis and Hydrodeoxygenation Properties of Ruthenium Phosphide Catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bowker, Richard H.; Smith, Mica C.; Pease, Melissa

2011-07-01

Ru2P/SiO2 and RuP/SiO2 catalysts were prepared by the temperature-programmed reduction (TPR) of uncalcined precursors containing hypophosphite ion (H2PO2-) as the phosphorus source. The Ru2P/SiO2 and RuP/SiO2 catalysts had small average particle sizes (~4 nm) and high CO chemisorption capacities (90-110 umol/g). The Ru phosphide catalysts exhibited similar or higher furan (C4H4O) hydrodeoxygenation (HDO) activities than did a Ru/SiO2 catalyst, and the phosphide catalysts favored C4 hydrocarbon products while the Ru metal catalyst produced primarily C3 hydrocarbons.

Photoluminescence of Gallium Phosphide-Based Nanostructures with Germanium Quantum Dots, Grown by Liquid-Phase Epitaxy

NASA Astrophysics Data System (ADS)

Maronchuk, I. I.; Sanikovich, D. D.; Velchenko, A. A.

2017-11-01

We have used liquid-phase epitaxy with pulsed substrate cooling using two structural designs to grow samples of nanoheteroepitaxial structures with Ge quantum dots in a GaP matrix on Si substrates. We have measured the photoluminescence spectra of the samples at temperatures of 77 K and 300 K with excitation by laser emission at λ = 4880 Å and 5145 Å. We draw conclusions concerning the factors influencing the spectrum and intensity of emission for nanostructures with quantum dots. It was found that in order to reduce nonradiative recombination in multilayer p-n structures, we need to create quantum dot arrays inside p and n regions rather than in the central portion of the depletion layer of the p-n junction. We show that the theoretical energies for Ge quantum dots of the calculated sizes are comparable with the energies of their photoluminescence maxima.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lavina, Barbara; Kim, Eunja; Cynn, Hyunchae

Using combined experimental and computational approaches, we show that at 43 GPa and 1300 K gallium phosphide adopts the super-Cmcm structure, here indicated with its Pearson notation oS24. First-principles enthalpy calculations demonstrate that this structure is more thermodynamically stable above ~20 GPa than previously proposed polymorphs. Here, in contrast to other polymorphs, the oS24 phase shows a strong bonding differentiation and distorted fivefold coordination geometries of both P atoms. The shortest bond of the phase is a single covalent P–P bond measuring 2.171(11) Å at synthesis pressure. Phosphorus dimerization in GaP sheds light on the nature of the super-Cmcm phasemore » and provides critical new insights into the high-pressure polymorphism of octet semiconductors. Bond directionality and anisotropy explain the relatively low symmetry of this high-pressure phase.« less

The gallium melting-point standard: its role in our temperature measurement system.

PubMed

Mangum, B W

1977-01-01

The latest internationally-adopted temperature scale, the International Practical Temperature Scale of 1968 (amended edition of 1975), is discussed in some detail and a brief description is given of its evolution. The melting point of high-purity gallium (stated to be at least 99.99999% pure) as a secondary temperature reference point is evaluated. I believe that this melting-point temperature of gallium should be adopted by the various medical professional societies and voluntary standards groups as the reaction temperature for enzyme reference methods in clinical enzymology. Gallium melting-point cells are available at the National Bureau of Standards as Standard Reference Material No. 1968.

Induced changes in refractive index, optical band gap, and absorption edge of polycarbonate-SiO2 thin films by Vis-IR lasers

NASA Astrophysics Data System (ADS)

Ehsani, Hassan; Akhoondi, Somaieh

2016-09-01

In this experimental work, we have studied induced changes in refractive index, extinction coefficient, and optical band-gap of Bisphenol-A-polycarbonate (BPA-PC) coated with a uniform and thin, anti-scratch SiO2 film irradiated by visible to near-infrared lasers at 532 nm (green),650 nm(red), and 980 nm (IR)wavelength lasers with different energy densities. Our lasers sources are indium-gallium-aluminum-phosphide, second harmonic of neodymium-YAG-solid state lasers and gallium-aluminum-arsenide-semiconductor laser. The energy densities of our sources have been changed by changing the spot size of incident laser. samples transmission spectra were monitored by carry500 spectrophotometer and induced changes in optical properties are evaluated by using, extrapolation of the transmission spectrum through Swanepoel method and computer application

An Indium Gallium Arsenide Visible/SWIR Focal Plane Array for Low Light Level Imaging

NASA Technical Reports Server (NTRS)

Cohen, Marshall J.; Ettenberg, Martin H.; Lange, Michael J.; Olsen, Gregory H.

1999-01-01

PIN photodiodes fabricated from indium gallium arsenide lattice-matched to indium phosphide substrates (In(.53)Ga(.47)As/InP) exhibit low reverse saturation current densities (JD < 10(exp -8) A/sq cm), and high shunt resistance-area products (RoA > 10(exp 6) omega-sq cm) at T=290K. Backside-illuminated, hybrid-integrated InGaAs FPAs are sensitive from 0.9 micrometers to 1.7 micrometers. 290K detectivities, D(*), greater than 10(exp 14) cm-(square root of Hz/W) are demonstrated. This represents the highest room temperature detectivity of any infrared material. The long wavelength cutoff (1.7 micrometers) makes In(.53)Ga(.47)As an idea match to the available airglow that has major peaks at 1.3 micrometers and 1.6 micrometers. The short wavelength 'cut-on' at 0.9 micrometers is due to absorption in the InP substrate. We will report on new InGaAs FPA epitaxial structures and processing techniques. These have resulted in improved performance in the form of a 10 x increase in detectivity and visible response via removal of the InP substrate. The resulting device features visible and SWIR response with greater than 15% quantum efficiency at 0.5 micrometers while maintaining the long wavelength cutoff. Imaging has been demonstrated under overcast starlight/urban glow conditions with cooling provided by a single stage thermoelectric cooler. Details on the material structure and device fabrication, quantitative characterization of spectral response and detectivity, as well as examples of night vision imagery are presented.

Optical and Electrical Characterization of Melt-Grown Bulk Indium Gallium Arsenide and Indium Arsenic Phosphide Alloys

DTIC Science & Technology

2011-03-01

order to find Eg/dT, we like to start with taking second derivatives of the absorption coefficient 53 g E EE t EEe E C dE d t g , 22 2...lower band, Nh) is closely related to the Fermi-Dirac distribution, Tk EE Ef B Fexp1 1 )( . (2.1) Here f(E) is the probability of occupying...47 ., , /)( gg g EEE EEEEA EECe tg (4.3) Here the C and A parameters are constants for a given material, for instance, A is

Probing near-normally propagating bulk acoustic waves using pseudo-reflection geometry Brillouin spectroscopy

NASA Astrophysics Data System (ADS)

Parsons, L. C.; Andrews, G. T.

2012-09-01

Pseudo-reflection geometry Brillouin spectroscopy can be used to probe acoustic wave dispersion approximately along the surface normal of a material system while avoiding the difficulties associated with specularly reflected light encountered in an ideal reflection configuration. As an example of its application, we show analytically that it can be used to determine both the refractive index and bulk acoustic mode velocities of optically-isotropic non-metallic materials and confirm the utility of the approach via a series of experiments on fused quartz, gallium phosphide, water, and porous silicon films.

Electrochemical Characterization of InP and GaAs Based Structures for Space Solar Cell Applications.

NASA Technical Reports Server (NTRS)

Faur, Maria; Faur, Mircea; Jenkins, Philip P.; Goradia, Manju; Wilt, David M.

1994-01-01

In this paper the emphasis is on accurate majority carrier concentration EC-V profiling of structures based on Indium Phosphide and Gallium Arsenide, using a newly developed electrolyte based on Hydrogen Flouride, Acetic Acid, Phosphoric Acid, 1-phenyl-2-propanamine and Ammonia Diflouride. Some preliminary data on the use of this electrolyte for determining the energy distribution of surface and deep states of these structures, applicable to fabrication process optimization and radiation induced defects studies of solar cells, are also provided.

Water-Vapor-Mediated Close-Spaced Vapor Transport Growth of Epitaxial Gallium Indium Phosphide Films on Gallium Arsenide Substrates

DOE PAGES

Greenaway, Ann L.; Bachman, Benjamin F.; Boucher, Jason W.; ...

2018-01-12

Ga 1–xIn xP is a technologically important III–V ternary semiconductor widely utilized in commercial and record-efficiency solar cells. We report the growth of Ga 1–xIn xP by water-vapor-mediated close-spaced vapor transport. Because growth of III–V semiconductors in this system is controlled by diffusion of metal oxide species, we find that congruent transport from the mixed powder source requires complete annealing to form a single alloy phase. Growth from a fully alloyed source at water vapor concentrations of ~7000 ppm in H 2 at 850 °C affords smooth films with electron mobility of 1070 cm 2 V –1 s –1 andmore » peak internal quantum efficiency of ~90% for carrier collection in a nonaqueous photoelectrochemical test cell.« less

Water-Vapor-Mediated Close-Spaced Vapor Transport Growth of Epitaxial Gallium Indium Phosphide Films on Gallium Arsenide Substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Greenaway, Ann L.; Bachman, Benjamin F.; Boucher, Jason W.

Ga 1–xIn xP is a technologically important III–V ternary semiconductor widely utilized in commercial and record-efficiency solar cells. We report the growth of Ga 1–xIn xP by water-vapor-mediated close-spaced vapor transport. Because growth of III–V semiconductors in this system is controlled by diffusion of metal oxide species, we find that congruent transport from the mixed powder source requires complete annealing to form a single alloy phase. Growth from a fully alloyed source at water vapor concentrations of ~7000 ppm in H 2 at 850 °C affords smooth films with electron mobility of 1070 cm 2 V –1 s –1 andmore » peak internal quantum efficiency of ~90% for carrier collection in a nonaqueous photoelectrochemical test cell.« less

The Influence of High-Energy Electrons Irradiation on Surface of n-GaP and on Au/n-GaP/Al Schottky Barrier Diode

NASA Astrophysics Data System (ADS)

Demir, K. Çinar; Kurudirek, S. V.; Oz, S.; Biber, M.; Aydoğan, Ş.; Şahin, Y.; Coşkun, C.

We fabricated 25 Au/n-GaP/Al Schottky devices and investigated the influence of high electron irradiation, which has 12MeV on the devices, at room temperature. The X-ray diffraction patterns, scanning electron microscopic images and Raman spectra of a gallium phosphide (GaP) semiconductor before and after electron irradiation have been analyzed. Furthermore, some electrical measurements of the devices were carried out through the current-voltage (I-V) and capacitance-voltage (C-V) measurements. From the I-V characteristics, experimental ideality factor n and barrier height Φ values of these Schottky diodes have been determined before and after irradiation, respectively. The results have also been analyzed statically, and a gauss distribution has been obtained. The built-in potential Vbi, barrier height Φ, Fermi level EF and donor concentration Nd values have been determined from the reverse bias C-V and C-2-V curves of Au/n-GaP/Al Schottky barrier diodes at 100kHz before and after 12MeV electron irradiation. Furthermore, we obtained the series resistance values of Au/n-GaP/Al Schottky barrier diodes with the help of different methods. Experimental results confirmed that the electrical characterization of the device changed with the electron irradiation.

Photovoltaic options for solar electric propulsion

NASA Technical Reports Server (NTRS)

Stella, Paul M.; Flood, Dennis J.

1990-01-01

During the past decade, a number of advances have occurred in solar cell and array technology. These advances have lead to performance improvement for both conventional space arrays and for advanced technology arrays. Performance enhancements have occurred in power density, specific power, and environmental capability. Both state-of-the-art and advanced development cells and array technology are discussed. Present technology will include rigid, rollout, and foldout flexible substrate designs, with silicon and GaAs solar cells. The use of concentrator array systems is also discussed based on both DOD and NASA efforts. The benefits of advanced lightweight array technology, for both near term and far term utilization, and of advanced high efficiency, thin, radiation resistant cells is examined. This includes gallium arsenide on germaniun substrates, indium phosphide, and thin film devices such as copper indium diselenide.

Synthesis and thermoelectric properties of CoP(sub 3)

NASA Technical Reports Server (NTRS)

Shields, V. B.; Caillet, T.

2002-01-01

In an effort to expand the range of operation for highly efficient, segmented thermoelectric unicouples currently being developed at JPL, skutterudite phosphides are being investigated as potential high temperature segments to supplement antimonide segments that limit the use of these unicouples at a hot-side temperature of about 873-973 K.

Elastic, magnetic and electronic properties of iridium phosphide Ir 2P

DOE PAGES

Wang, Pei; Wang, Yonggang; Wang, Liping; ...

2016-02-24

Cubic (space group: Fm3¯m) iridium phosphide, Ir 2P, has been synthesized at high pressure and high temperature. Angle-dispersive synchrotron X-ray diffraction measurements on Ir 2P powder using a diamond-anvil cell at room temperature and high pressures (up to 40.6 GPa) yielded a bulk modulus of B 0 = 306(6) GPa and its pressure derivative B 0'= 6.4(5). Such a high bulk modulus attributed to the short and strongly covalent Ir-P bonds as revealed by first – principles calculations and three-dimensionally distributed [IrP 4] tetrahedron network. Indentation testing on a well–sintered polycrystalline sample yielded the hardness of 11.8(4) GPa. Relatively lowmore » shear modulus of ~64 GPa from theoretical calculations suggests a complicated overall bonding in Ir 2P with metallic, ionic, and covalent characteristics. Additionally, a spin glass behavior is indicated by magnetic susceptibility measurements.« less

Gallium--A smart metal

USGS Publications Warehouse

Foley, Nora; Jaskula, Brian W.

2013-01-01

Gallium is a soft, silvery metallic element with an atomic number of 31 and the chemical symbol Ga. The French chemist Paul-Emile Lecoq de Boisbaudran discovered gallium in sphalerite (a zinc-sulfide mineral) in 1875 using spectroscopy. He named the element "gallia" after his native land of France (formerly Gaul; in Latin, Gallia). The existence of gallium had been predicted in 1871 by Dmitri Mendeleev, the Russian chemist who published the first periodic table of the elements. Mendeleev noted a gap in his table and named the missing element "eka-aluminum" because he determined that its location was one place away from aluminum in the table. Mendeleev thought that the missing element (gallium) would be very much like aluminum in its chemical properties, and he was right. Solid gallium has a low melting temperature (~29 degrees Celsius, or °C) and an unusually high boiling point (~2,204 °C). Because of these properties, the earliest uses of gallium were in high-temperature thermometers and in designing metal alloys that melt easily. The development of a gallium-based direct band-gap semiconductor in the 1960s led to what is now one of the most well-known applications for gallium-based products--the manufacture of smartphones and data-centric networks.

Hybrid photonic crystal cavity and waveguide for coupling to diamond NV-centers.

PubMed

Barclay, Paul E; Fu, Kai-Mei; Santori, Charles; Beausoleil, Raymond G

2009-06-08

A design for an ultra-high Q photonic crystal nanocavity engineered to interact with nitrogen-vacancy (NV) centers located near the surface of a single crystal diamond sample is presented. The structure is based upon a nanowire photonic crystal geometry, and consists of a patterned high refractive index thin film, such as gallium phosphide (GaP), supported by a diamond substrate. The nanocavity supports a mode with quality factor Q > 1.5 x 10(6) and mode volume V < 0.52(lambda/nGaP)(3), and promises to allow Purcell enhanced collection of spontaneous emission from an NV located more than 50 nm below the diamond surface. The nanowire photonic crystal waveguide can be used to efficiently couple light into and out of the cavity, or as an efficient broadband collector of NV phonon sideband emission. The proposed structures can be fabricated using existing materials and processing techniques.

High-temperature optically activated GaAs power switching for aircraft digital electronic control

NASA Technical Reports Server (NTRS)

Berak, J. M.; Grantham, D. H.; Swindal, J. L.; Black, J. F.; Allen, L. B.

1983-01-01

Gallium arsenide high-temperature devices were fabricated and assembled into an optically activated pulse-width-modulated power control for a torque motor typical of the kinds used in jet engine actuators. A bipolar heterojunction phototransistor with gallium aluminum arsenide emitter/window, a gallium arsenide junction field-effect power transistor and a gallium arsenide transient protection diode were designed and fabricated. A high-temperature fiber optic/phototransistor coupling scheme was implemented. The devices assembled into the demonstrator were successfully tested at 250 C, proving the feasibility of actuator-located switching of control power using optical signals transmitted by fibers. Assessments of the efficiency and technical merits were made for extension of this high-temperature technology to local conversion of optical power to electrical power and its control at levels useful for driving actuators. Optical power sources included in the comparisons were an infrared light-emitting diode, an injection laser diode, tungsten-halogen lamps and arc lamps. Optical-to-electrical power conversion was limited to photovoltaics located at the actuator. Impedance matching of the photovoltaic array to the load was considered over the full temperature range, -55 C to 260 C. Loss of photovoltaic efficiency at higher temperatures was taken into account. Serious losses in efficiency are: (1) in the optical source and the cooling which they may require in the assumed 125 C ambient, (2) in the decreased conversion efficiency of the gallium arsenide photovoltaic at 260 C, and (3) in impedance matching. Practical systems require improvements in these areas.

Thermal Cycling and High Temperature Reverse Bias Testing of Control and Irradiated Gallium Nitride Power Transistors

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Boomer, Kristen T.; Scheick, Leif; Lauenstein, Jean-Marie; Casey, Megan; Hammoud, Ahmad

2014-01-01

The power systems for use in NASA space missions must work reliably under harsh conditions including radiation, thermal cycling, and exposure to extreme temperatures. Gallium nitride semiconductors show great promise, but information pertaining to their performance is scarce. Gallium nitride N-channel enhancement-mode field effect transistors made by EPC Corporation in a 2nd generation of manufacturing were exposed to radiation followed by long-term thermal cycling and testing under high temperature reverse bias conditions in order to address their reliability for use in space missions. Result of the experimental work are presented and discussed.

Gallium alloy films investigated for use as boundary lubricants

NASA Technical Reports Server (NTRS)

1966-01-01

Gallium alloyed with other low melting point metals has excellent lubricant properties of fluidity and low vapor pressure for high temperature or vacuum environments. The addition of other soft metals reduces the corrosivity and formation of undesirable alloys normally found with gallium.

Diffusion length variation and proton damage coefficients for InP/In(x)Ga(1-x)As/GaAs solar cells

NASA Technical Reports Server (NTRS)

Jain, R. K.; Weinberg, I.; Flood, D. J.

1993-01-01

Indium phosphide solar cells are more radiation resistant than gallium arsenide and silicon solar cells, and their growth by heteroepitaxy offers additional advantages leading to the development of lighter, mechanically strong and cost-effective cells. Changes in heteroepitaxial InP cell efficiency under 0.5 and 3 MeV proton irradiations are explained by the variation in the minority-carrier diffusion length. The base diffusion length versus proton fluence is calculated by simulating the cell performance. The diffusion length damage coefficient K(L) is plotted as a function of proton fluence.

Evidence for the bias-driven migration of oxygen vacancies in amorphous non-stoichiometric gallium oxide

NASA Astrophysics Data System (ADS)

Guo, D. Y.; Qian, Y. P.; Su, Y. L.; Shi, H. Z.; Li, P. G.; Wu, J. T.; Wang, S. L.; Cui, C.; Tang, W. H.

2017-06-01

The conductivity of gallium oxide thin films is strongly dependent on the growth temperature when they deposited by pulsed laser deposition under vacuum environment, exhibiting an insulative-to-metallic transition with the decrease of the temperature. The high conductive gallium oxide films deposited at low temperature are amorphous, non-stoichiometric, and rich in oxygen vacancy. Large changes in electrical resistance are observed in these non-stoichiometric thin films. The wide variety of hysteretic shapes in the I-V curves depend on the voltage-sweep rate, evidencing that the time-dependent redistribution of oxygen vacancy driven by bias is the controlling parameter for the resistance of gallium oxide.

Recovery of Gallium from Secondary V-Recycling Slag by Alkali Fusion

NASA Astrophysics Data System (ADS)

Gao, Lei; Shi, Zhe; Zhang, Gui-fang

Secondary V-recycling slag, an industrial waste containing high gallium is being dumped continuously, which causes the loss of gallium. Thus, the alkali fusion process was employed to recover gallium from this slag. The effects factors on extraction of gallium such as roasting temperature, roasting time, alkali fusion agent concentration and CaO concentration were investigated in the paper. The experimental results indicated that excessive roasting temperature and roasting time is unfavorable to the recovery rate of gallium. The appropriate roasting temperature and duration are 1000°C and 2 hours, respectively; The appropriate proportioning of Na2CO3: NaOH is 2:1 when the concentration of alkali fusion agent weighs 0.4 times the mass of the slag; In order to remove SiO2 from the leaching liquor, CaO should be used as an additive in the roasting process. The appropriate concentration of CaO should weigh 0.2 times the mass of the slag. Employing these optimal alkali fusion conditions in the roasting process, gallium recovery is above 90%.

Low temperature recombination and trapping analysis in high purity gallium arsenide by microwave photodielectric techniques

NASA Technical Reports Server (NTRS)

Khambaty, M. B.; Hartwig, W. H.

1972-01-01

Some physical theories pertinent to the measurement properties of gallium arsenide are presented and experimental data are analyzed. A model for explaining recombination and trapping high purity gallium arsenide, valid below 77 K is assembled from points made at various places and an appraisal is given of photodielectric techniques for material property studies.

Strain-Compensated InGaAsP Superlattices for Defect Reduction of InP Grown on Exact-Oriented (001) Patterned Si Substrates by Metal Organic Chemical Vapor Deposition.

PubMed

Megalini, Ludovico; Šuran Brunelli, Simone Tommaso; Charles, William O; Taylor, Aidan; Isaac, Brandon; Bowers, John E; Klamkin, Jonathan

2018-02-26

We report on the use of InGaAsP strain-compensated superlattices (SC-SLs) as a technique to reduce the defect density of Indium Phosphide (InP) grown on silicon (InP-on-Si) by Metal Organic Chemical Vapor Deposition (MOCVD). Initially, a 2 μm thick gallium arsenide (GaAs) layer was grown with very high uniformity on exact oriented (001) 300 mm Si wafers; which had been patterned in 90 nm V-grooved trenches separated by silicon dioxide (SiO₂) stripes and oriented along the [110] direction. Undercut at the Si/SiO₂ interface was used to reduce the propagation of defects into the III-V layers. Following wafer dicing; 2.6 μm of indium phosphide (InP) was grown on such GaAs-on-Si templates. InGaAsP SC-SLs and thermal annealing were used to achieve a high-quality and smooth InP pseudo-substrate with a reduced defect density. Both the GaAs-on-Si and the subsequently grown InP layers were characterized using a variety of techniques including X-ray diffraction (XRD); atomic force microscopy (AFM); transmission electron microscopy (TEM); and electron channeling contrast imaging (ECCI); which indicate high-quality of the epitaxial films. The threading dislocation density and RMS surface roughness of the final InP layer were 5 × 10⁸/cm² and 1.2 nm; respectively and 7.8 × 10⁷/cm² and 10.8 nm for the GaAs-on-Si layer.

Strain-Compensated InGaAsP Superlattices for Defect Reduction of InP Grown on Exact-Oriented (001) Patterned Si Substrates by Metal Organic Chemical Vapor Deposition

PubMed Central

Megalini, Ludovico; Šuran Brunelli, Simone Tommaso; Charles, William O.; Taylor, Aidan; Isaac, Brandon; Klamkin, Jonathan

2018-01-01

We report on the use of InGaAsP strain-compensated superlattices (SC-SLs) as a technique to reduce the defect density of Indium Phosphide (InP) grown on silicon (InP-on-Si) by Metal Organic Chemical Vapor Deposition (MOCVD). Initially, a 2 μm thick gallium arsenide (GaAs) layer was grown with very high uniformity on exact oriented (001) 300 mm Si wafers; which had been patterned in 90 nm V-grooved trenches separated by silicon dioxide (SiO2) stripes and oriented along the [110] direction. Undercut at the Si/SiO2 interface was used to reduce the propagation of defects into the III–V layers. Following wafer dicing; 2.6 μm of indium phosphide (InP) was grown on such GaAs-on-Si templates. InGaAsP SC-SLs and thermal annealing were used to achieve a high-quality and smooth InP pseudo-substrate with a reduced defect density. Both the GaAs-on-Si and the subsequently grown InP layers were characterized using a variety of techniques including X-ray diffraction (XRD); atomic force microscopy (AFM); transmission electron microscopy (TEM); and electron channeling contrast imaging (ECCI); which indicate high-quality of the epitaxial films. The threading dislocation density and RMS surface roughness of the final InP layer were 5 × 108/cm2 and 1.2 nm; respectively and 7.8 × 107/cm2 and 10.8 nm for the GaAs-on-Si layer. PMID:29495381

Can Ni phosphides become viable hydroprocessing catalysts?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soled, S.; Miseo, S.; Baumgartner, J.

2015-05-15

We prepared higher surface area nickel phosphides than are normally found by reducing nickel phosphate. To do this, we hydrothermally synthesized Ni hydroxy phosphite precursors with low levels of molybdenum substitution. The molybdenum substitution increases the surface area of these precursors. During pretreatment in a sulfiding atmosphere (such as H2S/H2) dispersed islands of MoS2 segregate from the precursor and provide a pathway for H2 dissociation that allows reduction of the phosphite precursor to nickel phosphide at substantially lower temperatures than in the absence of MoS2. The results reported here show that to create nickel phosphides with comparable activity to conventionalmore » supported sulfide catalysts, one would have to synthesize the phosphide with surface areas exceeding 400 m2/g (i.e. with nanoparticles less than 30 Å in lateral dimension).« less

Automated realization of the gallium melting and triple points

NASA Astrophysics Data System (ADS)

Yan, X.; Duan, Y.; Zhang, J. T.; Wang, W.

2013-09-01

In order to improve the automation and convenience of the process involved in realizing the gallium fixed points, an automated apparatus, based on thermoelectric and heat pipe technologies, was designed and developed. This paper describes the apparatus design and procedures for freezing gallium mantles and realizing gallium melting and triple points. Also, investigations on the melting behavior of a gallium melting point cell and of gallium triple point cells were carried out while controlling the temperature outside the gallium point cells at 30 °C, 30.5 °C, 31 °C, and 31.5 °C. The obtained melting plateau curves show dentate temperature oscillations on the melting plateaus for the gallium point cells when thermal couplings occurred between the outer and inner liquid-solid interfaces. The maximum amplitude of the temperature fluctuations was about 1.5 mK. Therefore, the temperature oscillations can be used to indicate the ending of the equilibrium phase transitions. The duration and amplitude of such temperature oscillations depend on the temperature difference between the setting temperature and the gallium point temperature; the smaller the temperature difference, the longer the duration of both the melting plateaus and the temperature fluctuations.

Superconductivity theory applied to the periodic table of the elements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elifritz, T.L.

1994-12-31

The modern theory of superconductivity, based upon the BCS to Bose-Einstein transition, is applied to the periodic table of the elements, in order to isolate the essential features of high temperature superconductivity and to predict its occurrence within the periodic table. It is predicted that Sodium-Ammonia, Sodium Zinc Phosphide and Bismuth (I) Iodide are promising materials for experimental explorations of high temperature superconductivity.

[Synthesis and spectral characteristic of Ga-Fe3O4 at room temperature].

PubMed

Wang, Jing; Deng, Tong; Yang, Cai-Qin; Lin, Yu-Long; Wang, Wei; Wu, Hai-Yan

2008-03-01

Gallium bearing ferrites with different gallium content were synthesized by oxidation of ferrous and gallium ions under alkaline condition and room temperature. The samples were subjected to IR, XRD, Mossbauer spectral analysis and magnetization characterization. The results indicated that the green-rust intermediate phase would be produced during the procedure of Ga-Fe3O4 formation, and the green-rust intermediate phase was converted to ferrites with spinel structure during the drying under hot-N2 atmosphere. With the introduction of gallium into the spinel structure, the interplanar crystal spacing of the spinel structure decreased, as indicated from XRD spectra, and the lattice vibration of M(T)-O-M(o) moved to the high-frequency resulting from IR spectra. A small amount gallium introduction entered the tetrahedral sites preferentially rather than the octahedral sites, and increasing gallium introduction would enhance the occupation of octahedral sites. Furthermore, a small content of gallium in the initial solution could prevent the formation of non-magnetic Fe2O3.

Microscopic Nanomechanical Dissipation in Gallium Arsenide Resonators.

PubMed

Hamoumi, M; Allain, P E; Hease, W; Gil-Santos, E; Morgenroth, L; Gérard, B; Lemaître, A; Leo, G; Favero, I

2018-06-01

We report on a systematic study of nanomechanical dissipation in high-frequency (≈300  MHz) gallium arsenide optomechanical disk resonators, in conditions where clamping and fluidic losses are negligible. Phonon-phonon interactions are shown to contribute with a loss background fading away at cryogenic temperatures (3 K). Atomic layer deposition of alumina at the surface modifies the quality factor of resonators, pointing towards the importance of surface dissipation. The temperature evolution is accurately fitted by two-level systems models, showing that nanomechanical dissipation in gallium arsenide resonators directly connects to their microscopic properties. Two-level systems, notably at surfaces, appear to rule the damping and fluctuations of such high-quality crystalline nanomechanical devices, at all temperatures from 3 to 300 K.

Microscopic Nanomechanical Dissipation in Gallium Arsenide Resonators

NASA Astrophysics Data System (ADS)

Hamoumi, M.; Allain, P. E.; Hease, W.; Gil-Santos, E.; Morgenroth, L.; Gérard, B.; Lemaître, A.; Leo, G.; Favero, I.

2018-06-01

We report on a systematic study of nanomechanical dissipation in high-frequency (≈300 MHz ) gallium arsenide optomechanical disk resonators, in conditions where clamping and fluidic losses are negligible. Phonon-phonon interactions are shown to contribute with a loss background fading away at cryogenic temperatures (3 K). Atomic layer deposition of alumina at the surface modifies the quality factor of resonators, pointing towards the importance of surface dissipation. The temperature evolution is accurately fitted by two-level systems models, showing that nanomechanical dissipation in gallium arsenide resonators directly connects to their microscopic properties. Two-level systems, notably at surfaces, appear to rule the damping and fluctuations of such high-quality crystalline nanomechanical devices, at all temperatures from 3 to 300 K.

Hydrodeoxygenation of phenolic compounds to cycloalkanes over supported nickel phosphides

DOE PAGES

Yu, Zhiquan; Wang, Anjie; Liu, Shan; ...

2018-05-07

SiO 2, HZSM-5 and Al 2O 3 were used to support nickel phosphides to prepare hydrodeoxygenation (HDO) catalysts. The nickel loading was kept at 20 wt% while the Ni/P molar ratio was varied among 3, 2, and 1 in the preparation by incipient wetness impregnation. XRD characterization revealed that Ni 3P, Ni 12P 5, and Ni 2P as the major crystal phases were obtained at Ni/P ratio of 3, 2, and 1, respectively, on SiO 2 and HZSM-5. When Al 2O 3 was used as the support, nickel metal rather than nickel phosphides was generated. Among SiO 2-supported nickel phosphides,more » Ni 3P exhibited highest hydrogenation activity and catalytic performance in phenol HDO. Ni 3P/HZSM-5 showed the high catalytic performance in HDO of phenol as well as catechol and o-cresol, with Ni 3P as the hydrogenation site and the acid sites in HZSM-5 zeolite as the dehydration site. In conclusion, the strong acidity in HZSM-5 also facilitated the isomerization of cycloalkanes at elevated temperatures.« less

InP (Indium Phosphide): Into the future

NASA Technical Reports Server (NTRS)

Brandhorst, Henry W., Jr.

1989-01-01

Major industry is beginning to be devoted to indium phosphide and its potential applications. Key to these applications are high speed and radiation tolerance; however the high cost of indium phosphide may be an inhibitor to progress. The broad applicability of indium phosphide to many devices will be discussed with an emphasis on photovoltaics. Major attention is devoted to radiation tolerance and means of reducing cost of devices. Some of the approaches applicable to solar cells may also be relevant to other devices. The intent is to display the impact of visionary leadership in the field and enable the directions and broad applicability of indium phosphide.

Flat-panel video resolution LED display system

NASA Astrophysics Data System (ADS)

Wareberg, P. G.; Kennedy, D. I.

The system consists of a 128 x 128 element X-Y addressable LED array fabricated from green-emitting gallium phosphide. The LED array is interfaced with a 128 x 128 matrix TV camera. Associated electronics provides for seven levels of grey scale above zero with a grey scale ratio of square root of 2. Picture elements are on 0.008 inch centers resulting in a resolution of 125 lines-per-inch and a display area of approximately 1 sq. in. The LED array concept lends itself to modular construction, permitting assembly of a flat panel screen of any desired size from 1 x 1 inch building blocks without loss of resolution. A wide range of prospective aerospace applications exist extending from helmet-mounted systems involving small dedicated arrays to multimode cockpit displays constructed as modular screens. High-resolution LED arrays are already used as CRT replacements in military film-marking reconnaissance applications.

Low Pressure Synthesis of Indium Phosphide,

DTIC Science & Technology

1982-04-01

UNCLASSIFIED F/G 713 M EEEEEEEEEII MEEMMMME W , 2~ h IW 𔃼 * ).I 2 MICROCOP RESOWI1OW TWS CHAT . . WROmNA RUIEJ MT STHDMS-W3-ALORMO TNDM- m &6.4. MM RO - TMS...pNode . M-V Semiconductor compound ’S.T o a.ek* !cm .. EImd’b lc a ..... . P Pocry sline large g rain .bgot of indiumn phosphide have been synthe- simed...indium temperature of 1003"C. 2. BACKGROUND .r. Indium phosphide is a compound composed of elements from the third and fifth columns of the periodic

Shock wave experiments on gallium

NASA Astrophysics Data System (ADS)

Jensen, Brian; Branch, Brittany; Cherne, Frank

2017-06-01

Gallium exhibits a complex phase diagram with multiple solid phases, an anomalous melt boundary, and a low-temperature melt transition making it a suitable material for shock wave studies focused on multiphase properties including kinetics and strength. Apart from high-pressure shock wave data that exists for the liquid phase, there is a clear lack of data in the low-pressure regime where much of the complexity in the phase diagram exists. In this work, a series of shock wave experiments were performed to begin examining the low-pressure region of the phase diagram. Additional data on a gallium alloy, which remains liquid at room temperature, will be presented and compared to data available for pure gallium (LA-UR-17-21449).

Tritium-field betacells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walko, R.J.; Lincoln, R.C.; Baca, W.E.

1991-01-01

Betavoltaic power sources operate by converting the nuclear decay energy of beta-emitting radioisotopes into electricity. Since they are not chemically driven, they could operate at temperatures which would either be to hot or too cold for typical chemical batteries. Further, for long lived isotopes, they offer the possibility of multi-decade active lifetimes. Two approaches are being investigated: direct and indirect conversion. Direct conversion cells consist of semiconductor diodes similar to photovoltaic cells. Beta particle directly bombard these cells, generating electron-hole pairs in the semiconductor which are converted to useful power. Many using low power flux beta emitters, wide bandgap semiconductorsmore » are required to achieve useful conversion efficiencies. The combination of tritium, as the beta emitter, and gallium phosphide (GaP), as the semiconductor converter, was evaluated. Indirect conversion betacells first convert the beta energy to light with a phosphor, and then to electricity with photovoltaic cells. An indirect conversion power source using a tritium radioluminescent (RL) light is being investigated. Our analysis indicates that this approach has the potential for significant volume and cost savings over the direct conversion method. 7 refs., 11 figs.« less

Tritium-field betacells

NASA Astrophysics Data System (ADS)

Walko, R. J.; Lincoln, R. C.; Baca, W. E.; Goods, S. H.; Negley, G. H.

Betavoltaic power sources operate by converting the nuclear decay energy of beta-emitting radioisotopes into electricity. Since they are not chemically driven, they could operate at temperatures which would either be too hot or too cold for typical chemical batteries. Further, for long lived isotopes, they offer the possibility of multi-decade active lifetimes. Two approaches are being investigated: direct and indirect conversion. Direct conversion cells consist of semiconductor diodes similar to photovoltaic cells. Beta particle directly bombard these cells, generating electron-hole pairs in the semiconductor which are converted to useful power. When using low power flux beta emitters, wide bandgap semiconductors are required to achieve useful conversion efficiencies. The combination of tritium, as the beta emitter, and gallium phosphide (GaP), as the semiconductor converter, was evaluated. Indirect conversion betacells first convert the beta energy to light with a phosphor, and then to electricity with photovoltaic cells. An indirect conversion power source using a tritium radioluminescent (RL) light is being investigated. Our analysis indicates that this approach has the potential for significant volume and cost savings over the direct conversion method.

Superconductivity theory applied to the periodic table of the elements

NASA Technical Reports Server (NTRS)

Elifritz, Thomas Lee

1995-01-01

The modern theory of superconductivity, based upon the BCS to Bose-Einstein transition is applied to the periodic table of the elements, in order to isolate the essential features of of high temperature superconductivity and to predict its occurrence with the periodic table. It is predicted that Sodium-Ammonia, Sodium Zinc Phosphide and Bismuth (I) Iodide are promising materials for experimental explorations of high temperature superconductivity.

Diffusion lengths in irradiated N/P InP-on-Si solar cells

NASA Technical Reports Server (NTRS)

Wojtczuk, Steven; Colerico, Claudia; Summers, Geoffrey P.; Walters, Robert J.; Burke, Edward A.

1995-01-01

Indium phosphide (InP) solar cells are being made on silicon (Si) wafers (InP/Si) to take advantage of both the radiation-hardness properties of the InP solar cell and the light weight and low cost of Si wafers compared to InP or germanium (Ge) wafers. The InP/Si cell application is for long duration and/or high radiation orbit space missions. InP/Si cells have higher absolute efficiency after a high radiation dose than gallium arsenide (GaAs) or silicon (Si) solar cells. In this work, base electron diffusion lengths in the N/P cell are extracted from measured AM0 short-circuit photocurrent at various irradiation levels out to an equivalent 1 MeV fluence of 1017 1 MeV electrons/sq cm for a 1 sq cm 12% BOL InP/Si cell. These values are then checked for consistency by comparing measured Voc data with a theoretical Voc model that includes a dark current term that depends on the extracted diffusion lengths.

Synchrotron x-ray high energy PDF and tomography studies for gallium melts under high-pressure conditions

NASA Astrophysics Data System (ADS)

Liu, H.; Liu, L. L.; Li, R.; Li, L.

2015-12-01

Liquid gallium exhibits unusual and unique physical properties. A rich polymorphism and metastable modifications of solid Ga have been discovered and a number of studies of liquid gallium under high pressure conditions were reported. However, some fundamental properties, such as the equation of state (EoS) of Ga melt under extreme conditions remain unclear. To compare to the previous reports, we performed the pair distribution function (PDF) study using diamond anvil cell, in which synchrotron high-energy x-ray total scattering data, combined with reverse Monte Carlo simulation, was used to study the microstructure and EoS of liquid gallium under high pressure at room temperature conditions. The EoS of Ga melt, which was measured from synchrotron x-ray tomography method at room temperature, was used to avoid the potential relatively big errors for the density estimation from the reverse Monte Carlo simulation with the mathematical fit to the measured structure factor data. The volume change of liquid gallium have been studied as a function of pressure and temperature up to 5 GPa at 370 K using synchrotron x-ray microtomography combined with energy dispersive x-ray diffraction (EDXRD) techniques using Drickamer press. The directly measured P-V-T curves were obtained from 3D tomography reconstruction data. The existence of possible liquid-liquid phase transition regions is proposed based on the abnormal compressibility and local structure change in Ga melts.

Preliminary Spectroscopic Measurements for a Gallium Electromagnetic (GEM) Thruster

NASA Technical Reports Server (NTRS)

Thomas, Robert E.; Burton, Rodney L.; Glumac, Nick G.; Polzin, Kurt A.

2007-01-01

As a propellant option for electromagnetic thrusters, liquid ,gallium appears to have several advantages relative to other propellants. The merits of using gallium in an electromagnetic thruster (EMT) are discussed and estimates of discharge current levels and mass flow rates yielding efficient operation are given. The gallium atomic weight of 70 predicts high efficiency in the 1500-2000 s specific impulse range, making it ideal for higher-thrust, near-Earth missions. A spatially and temporally broad spectroscopic survey in the 220-520 nm range is used to determine which species are present in the plasma and estimate electron temperature. The spectra show that neutral, singly, and doubly ionized gallium species are present in a 20 J, 1.8 kA (peak) are discharge. With graphite present on the insulator to facilitate breakdown, singly and doubly ionized carbon atoms are also present, and emission is observed from molecular carbon (CZ) radicals. A determination of the electron temperature was attempted using relative emission line data, and while the spatially and temporally averaged, spectra don't fit well to single temperatures, the data and presence of doubly ionized gallium are consistent with distributions in the 1-3 eV range.

Cobalt phosphide based nanostructures as bifunctional electrocatalysts for low temperature alkaline water splitting

DOE PAGES

Lambert, Timothy N.; Vigil, Julian A.; Christensen, Ben

2016-08-22

Cobalt phosphide based thin films and nanoparticles were prepared by the thermal phosphidation of spinel Co 3O 4 precursor films and nanoparticles, respectively. CoP films were prepared with overall retention of the Co 3O 4 nanoplatelet morphology while the spherical/cubic Co 3O 4 and Ni 0.15Co 2.85O 4 nanoparticles were converted to nanorods or nanoparticles, respectively. The inclusion of nickel in the nanoparticles resulted in a 2.5 fold higher surface area leading to higher gravimetric performance. In each case high surface area structures were obtained with CoP as the primary phase. All materials were found to act as effective bifunctionalmore » electrocatalysts for both the HER and the OER and compared well to commercial precious metal benchmark materials in alkaline electrolyte. As a result, a symmetrical water electrolysis cell prepared from the CoP-based film operated at a low overpotential of 0.41-0.51 V.« less

Radiation and temperature effects in gallium arsenide, indium phosphide and silicon solar cells

NASA Technical Reports Server (NTRS)

Weinberg, I.; Swartz, C. K.; Hart, R. E., Jr.; Statler, R. L.

1987-01-01

The effects of radiation on performance are determined for both n(+)p and p(+)n GaAs and InP cells and for silicon n(+)p cells. It is found that the radiation resistance of InP is greater than that of both GaAs and Si under 1 MeV electron irradiation. For silicon, the observed decreased radiation resistance with decreased resistivity is attributed to the presence of a radiation induced boron-oxygen defect. Comparison of radiation damage in both p(+)n and n(+)p GaAs cells yields a decreased radiation resistance for the n(+)p cell attributable to increased series resistance, decreased shunt resistance, and relatively greater losses in the cell's p-region. For InP, the n(+)p configuration is found to have greater radiation resistance than the p(+)n cell. The increased loss in this latter cell is attributed to losses in the cell's emitter region. Temperature dependency results are interpreted using a theoretical relation for dVoc/cT which predicts that increased Voc should results in decreased numerical values for dPm/dT. The predicted correlation is observed for GaAs but not for InP a result which is attributed to variations in cell processing.

Radiation and temperature effects in gallium arsenide, indium phosphide, and silicon solar cells

NASA Technical Reports Server (NTRS)

Weinberg, I.; Swartz, C. K.; Hart, R. E., Jr.; Statler, R. L.

1987-01-01

The effects of radiation on performance are determined for both n+p and p+n GaAs and InP cells and for silicon n+p cells. It is found that the radiation resistance of InP is greater than that of both GaAs and Si under 1-MeV electron irradiation. For silicon, the observed decreased radiation resistance with decreased resistivity is attributed to the presence of a radiation-induced boron-oxygen defect. Comparison of radiation damage in both p+n and n+p GaAs cells yields a decreased radiation resistance for the n+p cell attributable to increased series resistance, decreased shunt resistance, and relatively greater losses in the cell's p-region. For InP, the n+p configuration is found to have greater radiation resistance than the p+n cell. The increased loss in this latter cell is attributed to losses in the cell's emitter region. Temperature dependency results are interpreted using a theoretical relation for dVoc/dT, which predicts that increased Voc should result in decreased numerical values for dPm/dT. The predicted correlation is observed for GaAs but not for InP, a result which is attributed to variations in cell processing.

The effect of process conditions on the performance of epitaxial InP solar cells

NASA Technical Reports Server (NTRS)

Borrego, J. M.; Ghandi, S. K.

1991-01-01

Indium phosphide solar cells have a higher resistance to electron irradiation than Si or GaAs cells of comparable junction depth. As a result, there is much interest in the use of this material for space applications. Cells of this material were made in bulk InP by a number of techniques, including ion implantation, direct diffusion in sealed ampoules, and by open tube diffusion. However, it is generally considered that the epitaxial approach will be superior to all of these techniques. The epitaxy of InP is considerably more difficult than that of gallium arsenide, for a number of reasons. Perhaps the most important is the fact that the native oxides of Indium are extremely difficult to remove, as compared to that of Gallium. In addition, thermal treatments for the desorption of these oxides often result in the formation of phosphorus vacancies and free indium on the surface. Thus, inadequate sample preparation before epitaxy, poor reactor cleaning procedures, or poor transition procedures between the growth of successive layers, all give rise to trap phenomena and to high interface recombination velocities. Moreover, the lifetime of the grown material is dominated by the occurrence of native defects, so that it is a strong function of growth parameters. These problems are of special interest to the fabrication of solar cells, where long life-time, combined with the absence of traps, is highly desirable. A study of this problem is described using a non-invasive diagnostic technique which was developed.

Carbon nanothermometer containing gallium.

PubMed

Gao, Yihua; Bando, Yoshio

2002-02-07

Many applications have been found for carbon nanotubes, and we can now add a role as a 'nanothermometer' to this list. We describe how the height of a continuous, unidimensional column of liquid gallium inside a carbon nanotube (up to about 10 micrometres long and about 75 nanometres in diameter) varies linearly and reproducibly in the temperature range 50-500 degrees C, with an expansion coefficient that is the same as for gallium in the macroscopic state. We chose gallium as our thermal indicator because it has one of the greatest liquid ranges of any metal (29.78-2,403 degrees C) and a low vapour pressure even at high temperatures. This nanothermometer should be suitable for use in a wide variety of microenvironments.

Small-scale fracture toughness of ceramic thin films: the effects of specimen geometry, ion beam notching and high temperature on chromium nitride toughness evaluation

NASA Astrophysics Data System (ADS)

Best, James P.; Zechner, Johannes; Wheeler, Jeffrey M.; Schoeppner, Rachel; Morstein, Marcus; Michler, Johann

2016-12-01

For the implementation of thin ceramic hard coatings into intensive application environments, the fracture toughness is a particularly important material design parameter. Characterisation of the fracture toughness of small-scale specimens has been a topic of great debate, due to size effects, plasticity, residual stress effects and the influence of ion penetration from the sample fabrication process. In this work, several different small-scale fracture toughness geometries (single-beam cantilever, double-beam cantilever and micro-pillar splitting) were compared, fabricated from a thin physical vapour-deposited ceramic film using a focused ion beam source, and then the effect of the gallium-milled notch on mode I toughness quantification investigated. It was found that notching using a focused gallium source influences small-scale toughness measurements and can lead to an overestimation of the fracture toughness values for chromium nitride (CrN) thin films. The effects of gallium ion irradiation were further studied by performing the first small-scale high-temperature toughness measurements within the scanning electron microscope, with the consequence that annealing at high temperatures allows for diffusion of the gallium to grain boundaries promoting embrittlement in small-scale CrN samples. This work highlights the sensitivity of some materials to gallium ion penetration effects, and the profound effect that it can have on fracture toughness evaluation.

Capacitive Behavior of Single Gallium Oxide Nanobelt

PubMed Central

Cai, Haitao; Liu, Hang; Zhu, Huichao; Shao, Pai; Hou, Changmin

2015-01-01

In this research, monocrystalline gallium oxide (Ga2O3) nanobelts were synthesized through oxidation of metal gallium at high temperature. An electronic device, based on an individual Ga2O3 nanobelt on Pt interdigital electrodes (IDEs), was fabricated to investigate the electrical characteristics of the Ga2O3 nanobelt in a dry atmosphere at room temperature. The current-voltage (I-V) and I/V-t characteristics show the capacitive behavior of the Ga2O3 nanobelt, indicating the existence of capacitive elements in the Pt/Ga2O3/Pt structure. PMID:28793506

Correction: Ambient temperature deposition of gallium nitride/gallium oxynitride from a deep eutectic electrolyte, under potential control.

PubMed

Sarkar, Sujoy; Sampath, S

2016-05-28

Correction for 'Ambient temperature deposition of gallium nitride/gallium oxynitride from a deep eutectic electrolyte, under potential control' by Sujoy Sarkar et al., Chem. Commun., 2016, 52, 6407-6410.

Clarifying coverages on the basis of tapes SnO2, SiO2, Si3N4 for photodiodes of ultraviolet and visible range

NASA Astrophysics Data System (ADS)

Dobrovolsciy, Yu. George; Perevertaylo, Vladimir L.; Shabashcevich, Boris G.; Pidkamin, Leonid J.

2009-10-01

It is shown, what coverage of dioxide of tin is instrumental in the rise of sensitiveness of photodiodes sensible in the ultraviolet region of spectrum on the basis of selenid zinc and phosphide of gallium to 0,12 A/W and 0,2 A/W accordingly in the maximum of spectral description of sensitiveness. All so it is shown, that tape of nitrid silicon - dioxide of silicon a bit better clarifies silicon photodiode, especially on a wave-length 700 nm. Gluing composition, in general, worsens admission of tapes, and in a greater degree the admission of tape of nitrid silicon - dioxide of silicon.

Nanowire-Based Electrode for Acute In Vivo Neural Recordings in the Brain

PubMed Central

Suyatin, Dmitry B.; Wallman, Lars; Thelin, Jonas; Prinz, Christelle N.; Jörntell, Henrik; Samuelson, Lars; Montelius, Lars; Schouenborg, Jens

2013-01-01

We present an electrode, based on structurally controlled nanowires, as a first step towards developing a useful nanostructured device for neurophysiological measurements in vivo. The sensing part of the electrode is made of a metal film deposited on top of an array of epitaxially grown gallium phosphide nanowires. We achieved the first functional testing of the nanowire-based electrode by performing acute in vivo recordings in the rat cerebral cortex and withstanding multiple brain implantations. Due to the controllable geometry of the nanowires, this type of electrode can be used as a model system for further analysis of the functional properties of nanostructured neuronal interfaces in vivo. PMID:23431387

Optical and interfacial electronic properties of diamond-like carbon films

NASA Technical Reports Server (NTRS)

Woollam, J. A.; Natarajan, V.; Lamb, J.; Khan, A. A.; Bu-Abbud, G.; Banks, B.; Pouch, J.; Gulino, D. A.; Domitz, S.; Liu, D. C.

1984-01-01

Hard, semitransparent carbon films were prepared on oriented polished crystal wafers of silicon, indium phosphide and gallium arsenide, as well as on KBr and quartz. Properties of the films were determined using IR and visible absorption spectrocopy, ellipsometry, conductance-capacitance spectroscopy and alpha particle-proton recoil spectroscopy. Preparation techniques include RF plasma decomposition of methane (and other hydrocarbons), ion beam sputtering, and dual-ion-beam sputter deposition. Optical energy band gaps as large as 2.7 eV and extinction coefficients lower than 0.1 at long wavelengths are found. Electronic state densities at the interface with silicon as low as 10 to the 10th states/eV sq cm per were found.

Metal-Silicate Partitioning of Various Siderophile Elements at High Pressure and High Temperatures: a Diamond Anvil Cell Study

NASA Astrophysics Data System (ADS)

Badro, J.; Blanchard, I.; Siebert, J.

2015-12-01

Core formation is the major chemical fractionation that occurred on Earth. This event is widely believed to have happened at pressures of at least 40 GPa and temperatures exceeding 3000 K. It has left a significant imprint on the chemistry of the mantle by removing most of the siderophile (iron-loving) elements from it. Abundances of most siderophile elements in the bulk silicate Earth are significantly different than those predicted from experiments at low P-T. Among them, vanadium, chromium, cobalt and gallium are four siderophile elements which abundances in the mantle have been marked by core formation processes. Thus, understand their respective abundance in the mantle can help bringing constraints on the conditions of Earth's differentiation. We performed high-pressure high-temperature experiments using laser heating diamond anvil cell to investigate the metal-silicate partitioning of those four elements. Homogeneous glasses doped in vanadium, chromium, cobalt and gallium were synthesized using a levitation furnace and load inside the diamond anvil cell along with metallic powder. Samples were recovered using a Focused Ion Beam and chemically analyzed using an electron microprobe. We investigate the effect of pressure, temperature and metal composition on the metal-silicate partitioning of V, Cr, Co and Ga. Three previous studies focused on V, Cr and Co partitioning at those conditions of pressure and temperature, but none explore gallium partitioning at the relevant extreme conditions of core formation. We will present the first measurements of gallium metal-silicate partitioning performed at the appropriate conditions of pressure and temperature of Earth's differentiation.

Optimal design study of high efficiency indium phosphide space solar cells

NASA Technical Reports Server (NTRS)

Jain, Raj K.; Flood, Dennis J.

1990-01-01

Recently indium phosphide solar cells have achieved beginning of life AMO efficiencies in excess of 19 pct. at 25 C. The high efficiency prospects along with superb radiation tolerance make indium phosphide a leading material for space power requirements. To achieve cost effectiveness, practical cell efficiencies have to be raised to near theoretical limits and thin film indium phosphide cells need to be developed. The optimal design study is described of high efficiency indium phosphide solar cells for space power applications using the PC-1D computer program. It is shown that cells with efficiencies over 22 pct. AMO at 25 C could be fabricated by achieving proper material and process parameters. It is observed that further improvements in cell material and process parameters could lead to experimental cell efficiencies near theoretical limits. The effect of various emitter and base parameters on cell performance was studied.

The effect of different solar simulators on the measurement of short-circuit current temperature coefficients

NASA Technical Reports Server (NTRS)

Curtis, H. B.; Hart, R. E., Jr.

1982-01-01

Gallium arsenide solar cells are considered for several high temperature missions in space. Both near-Sun and concentrator missions could involve cell temperatures on the order of 200 C. Performance measurements of cells at elevated temperatures are usually made using simulated sunlight and a matched reference cell. Due to the change in bandgap with increasing temperature at portions of the spectrum where considerable simulated irradiance is present, there are significant differences in measured short circuit current at elevated temperatures among different simulators. To illustrate this, both experimental and theoretical data are presented for gallium arsenide cells.

New intermetallic MIrP (M=Ti, Zr, Nb, Mo) and MgRuP compounds related with MoM'P (M'=Ni and Ru) superconductor

NASA Astrophysics Data System (ADS)

Kito, Hijiri; Iyo, Akira; Wada, Toshimi

2011-01-01

Using a cubic-anvil high-pressure apparatus, ternary iridium phosphides MIrP (M=Ti, Zr, Nb, Mo) and MgRuP have been prepared by reaction of stoichiometric amounts of each metal and phosphide powders at around 2 Gpa and above 1523 K for the first time. The structure of these compounds prepared at high-pressure has been characterized by X-ray powder diffraction. Diffraction lines of these compounds are assigned by the index of the Co2Si-type structure. The electrical resistivity and the d.c magnetic susceptibility of MIrP (M=Ti, Zr, Nb, Mo) have measured at low temperatures. Unfortunately, no superconducting transition for MIrP (M=Ti, Zr, Nb, Mo) and MgRuP are observed down to 2 K.

Gallium-mediated growth of multiwall carbon nanotubes

NASA Astrophysics Data System (ADS)

Pan, Zheng Wei; Dai, Sheng; Beach, David B.; Evans, Neal D.; Lowndes, Douglas H.

2003-03-01

Liquid gallium was used as a viable and effective solvent and template for high-yield growth of multiwall carbon nanotubes. The gallium-mediated nanotubes thus obtained differ morphologically from nanotubes obtained by using transition metals as catalysts. The nanotubes have a pin-like morphology, generally composed of an oval-shaped tip filled with liquid gallium and a tapered hollow body. The inner diameter of the tube is so large that the inner/outer diameter ratio is usually larger than 0.9. The tubes are naturally opened at both ends. These gallium-filled nanotubes may be used as a nanothermometer in the temperature range of 30 to 550 °C. This study opens an interesting route for carbon nanotube synthesis.

The gallium melting-point standard: a determination of the liquid-solid equilibrium temperature of pure gallium on the International Practical Temperature Scale of 1968.

PubMed

Thornton, D D

1977-01-01

The sharpness and reproducibility of the gallium melting point were studied and the melting temperature of gallium in terms of IPTS-68 was determined. Small melting-point cells designed for use with thermistors are described. Nine gallium cells including three levels of purity were used in 68 separate determinations fo the melting point. The melting point of 99.99999% pure gallium in terms of IPTS-68 is found to be 29.771(4) +/- 0.001(4) degree C; the melting range is less than 0.0005 degree C and is reproducible to +/- 0.0004 degree C.

Preparation and characterization of a supported system of Ni2P/Ni12P5 nanoparticles and their use as the active phase in chemoselective hydrogenation of acetophenone

NASA Astrophysics Data System (ADS)

Costa, Dolly C.; Soldati, Analía L.; Pecchi, Gina; Bengoa, José Fernando; Marchetti, Sergio Gustavo; Vetere, Virginia

2018-05-01

Ni2P/Ni12P5 nanoparticles were obtained by thermal decomposition of nickel organometallic salt at low temperature. The use of different characterization techniques allowed us to determine that this process produced a mixture of two nickel phosphide phases: Ni2P and Ni12P5. These nickel phosphides nanoparticles, supported on mesoporous silica, showed activity and high selectivity for producing the hydrogenation of the acetophenone carbonyl group to obtain 1-phenylethanol. This is a first report that demonstrates the ability of supported Ni2P/Ni12P5 nanoparticles to produce the chemoselective hydrogenation of acetophenone. We attribute these special catalytic properties to the particular geometry of the Ni–P sites on the surface of the nanoparticles. This is an interesting result because the nickel phosphides have a wide composition range (from Ni3P to NiP3), with different crystallographic structures, therefore we think that different phases could be active and selective to hydrogenate many important molecules with more than one functional group.

MOF-Derived Ultrathin Cobalt Phosphide Nanosheets as Efficient Bifunctional Hydrogen Evolution Reaction and Oxygen Evolution Reaction Electrocatalysts

PubMed Central

Li, Hong; Ke, Fei; Zhu, Junfa

2018-01-01

The development of a highly efficient and stable bifunctional electrocatalyst for water splitting is still a challenging issue in obtaining clean and sustainable chemical fuels. Herein, a novel bifunctional catalyst consisting of 2D transition-metal phosphide nanosheets with abundant reactive sites templated by Co-centered metal−organic framework nanosheets, denoted as CoP-NS/C, has been developed through a facile one-step low-temperature phosphidation process. The as-prepared CoP-NS/C has large specific surface area and ultrathin nanosheets morphology providing rich catalytic active sites. It shows excellent electrocatalytic performances for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in acidic and alkaline media, with the Tafel slopes of 59 and 64 mV/dec and a current density of 10 mA/cm2 at the overpotentials of 140 and 292 mV, respectively, which are remarkably superior to those of CoP/C, CoP particles, and comparable to those of commercial noble-metal catalysts. In addition, the CoP-NS/C also shows good durability after a long-term test. PMID:29414838

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Zhiquan; Wang, Anjie; Liu, Shan

SiO 2, HZSM-5 and Al 2O 3 were used to support nickel phosphides to prepare hydrodeoxygenation (HDO) catalysts. The nickel loading was kept at 20 wt% while the Ni/P molar ratio was varied among 3, 2, and 1 in the preparation by incipient wetness impregnation. XRD characterization revealed that Ni 3P, Ni 12P 5, and Ni 2P as the major crystal phases were obtained at Ni/P ratio of 3, 2, and 1, respectively, on SiO 2 and HZSM-5. When Al 2O 3 was used as the support, nickel metal rather than nickel phosphides was generated. Among SiO 2-supported nickel phosphides,more » Ni 3P exhibited highest hydrogenation activity and catalytic performance in phenol HDO. Ni 3P/HZSM-5 showed the high catalytic performance in HDO of phenol as well as catechol and o-cresol, with Ni 3P as the hydrogenation site and the acid sites in HZSM-5 zeolite as the dehydration site. In conclusion, the strong acidity in HZSM-5 also facilitated the isomerization of cycloalkanes at elevated temperatures.« less

Optical properties and Faraday effect of ceramic terbium gallium garnet for a room temperature Faraday rotator.

PubMed

Yoshida, Hidetsugu; Tsubakimoto, Koji; Fujimoto, Yasushi; Mikami, Katsuhiro; Fujita, Hisanori; Miyanaga, Noriaki; Nozawa, Hoshiteru; Yagi, Hideki; Yanagitani, Takagimi; Nagata, Yutaka; Kinoshita, Hiroo

2011-08-01

The optical properties, Faraday effect and Verdet constant of ceramic terbium gallium garnet (TGG) have been measured at 1064 nm, and were found to be similar to those of single crystal TGG at room temperature. Observed optical characteristics, laser induced bulk-damage threshold and optical scattering properties of ceramic TGG were compared with those of single crystal TGG. Ceramic TGG is a promising Faraday material for high-average-power YAG lasers, Yb fiber lasers and high-peak power glass lasers for inertial fusion energy drivers.

Aluminum Phosphide Poisoning-Related Deaths in Tehran, Iran, 2006 to 2013

PubMed Central

Etemadi-Aleagha, Afshar; Akhgari, Maryam; Iravani, Fariba Sardari

2015-01-01

Abstract Metal phosphides such as aluminum phosphide are potent insecticides. This highly toxic substance is used for rice and other grains protection in Iran. Due to its high toxicity potential and easy availability, it is widely used as a suicide poison. This substance has no effective antidote and the incidence of deaths due to its poisoning is increasing day by day in Iran. The present study was conducted to show the increasing incidence of fatal aluminum phosphide poisoning and its toxicological and forensic aspects in an 8-year study, 2006 to 2013. Autopsy sheets were reviewed and cases with the history of aluminum phosphide poisoning were selected. Toxicological analysis results, demographic and necroscopic examination findings were studied. A total of 51.8% of studied cases were female. Most of the cases were between 10 and 40 years old. The manner of death was self-poisoning in 85% of cases. Morphine, ethanol, and amitriptyline were the most common additional drugs detected in toxicological analysis. The incidence of fatal aluminum phosphide poisoning cases referred for phosphine analysis was 5.22 and 37.02 per million of population of Tehran in 2006 and 2013, respectively. The results of this study showed that in spite of ban and restrictions, there was a dramatic increase in the incidence of fatal aluminum phosphide poisoning in Tehran from 2006 to 2013. Safety alert should be highlighted in training program for all population groups about the toxic effects of aluminum phosphide tablets. PMID:26402837

Large spin accumulation and crystallographic dependence of spin transport in single crystal gallium nitride nanowires

PubMed Central

Park, Tae-Eon; Park, Youn Ho; Lee, Jong-Min; Kim, Sung Wook; Park, Hee Gyum; Min, Byoung-Chul; Kim, Hyung-jun; Koo, Hyun Cheol; Choi, Heon-Jin; Han, Suk Hee; Johnson, Mark; Chang, Joonyeon

2017-01-01

Semiconductor spintronics is an alternative to conventional electronics that offers devices with high performance, low power and multiple functionality. Although a large number of devices with mesoscopic dimensions have been successfully demonstrated at low temperatures for decades, room-temperature operation still needs to go further. Here we study spin injection in single-crystal gallium nitride nanowires and report robust spin accumulation at room temperature with enhanced spin injection polarization of 9%. A large Overhauser coupling between the electron spin accumulation and the lattice nuclei is observed. Finally, our single-crystal gallium nitride samples have a trigonal cross-section defined by the (001), () and () planes. Using the Hanle effect, we show that the spin accumulation is significantly different for injection across the (001) and () (or ()) planes. This provides a technique for increasing room temperature spin injection in mesoscopic systems. PMID:28569767

Annular solid-immersion lenslet array super-resolution optical microscopy

NASA Astrophysics Data System (ADS)

Liau, Z. L.

2012-10-01

We describe a novel solid-immersion lenslet array, micro-fabricated in a chip form in the high-index (3.45) gallium phosphide. The innovatively designed lenslet features an annular aperture with appropriately patterned light absorbers and antireflection coatings. The array chip is easy to handle and enables the direct deposition of the specimen of interest onto its back-plane for tight adhesion and good optical coupling. The ensuing diffraction from the near field can yield supercritical rays inside the high-index lenslet and can, therefore, overcome the refraction and critical-angle limitations. This model showed agreement with the experimental observation of the solid-immersion fluorescence microscopy imaging, in which the refracted rays were completely blocked by the annular aperture. A large longitudinal (depth) magnification effect was also predicted and showed agreement with experiment. The annular lenslet's additional advantages of improved resolution and contrast were also discussed. Resolution of nested-L patterns with grating pitch as small as 100 nm was experimentally demonstrated. The demonstrated annular solid-immersion lenslet array concept is promising for a wider use in super-resolution optical microscopy.

InGaP Heterojunction Barrier Solar Cells

NASA Technical Reports Server (NTRS)

Welser, Roger E.

2010-01-01

A new solar-cell structure utilizes a single, ultra-wide well of either gallium arsenide (GaAs) or indium-gallium-phosphide (InGaP) in the depletion region of a wide bandgap matrix, instead of the usual multiple quantum well layers. These InGaP barrier layers are effective at reducing diode dark current, and photogenerated carrier escape is maximized by the proper design of the electric field and barrier profile. With the new material, open-circuit voltage enhancements of 40 and 100 mV (versus PIN control systems) are possible without any degradation in short-circuit current. Basic tenets of quantum-well and quantum- dot solar cells are utilized, but instead of using multiple thin layers, a single wide well works better. InGaP is used as a barrier material, which increases open current, while simultaneously lowering dark current, reducing both hole diffusion from the base, and space charge recombination within the depletion region. Both the built-in field and the barrier profile are tailored to enhance thermionic emissions, which maximizes the photocurrent at forward bias, with a demonstrated voltage increase. An InGaP heterojunction barrier solar cell consists of a single, ultra-wide GaAs, aluminum-gallium-arsenide (AlGaAs), or lower-energy-gap InGaP absorber well placed within the depletion region of an otherwise wide bandgap PIN diode. Photogenerated electron collection is unencumbered in this structure. InGaAs wells can be added to the thick GaAs absorber layer to capture lower-energy photons.

Scalable Indium Phosphide Thin-Film Nanophotonics Platform for Photovoltaic and Photoelectrochemical Devices.

PubMed

Lin, Qingfeng; Sarkar, Debarghya; Lin, Yuanjing; Yeung, Matthew; Blankemeier, Louis; Hazra, Jubin; Wang, Wei; Niu, Shanyuan; Ravichandran, Jayakanth; Fan, Zhiyong; Kapadia, Rehan

2017-05-23

Recent developments in nanophotonics have provided a clear roadmap for improving the efficiency of photonic devices through control over absorption and emission of devices. These advances could prove transformative for a wide variety of devices, such as photovoltaics, photoelectrochemical devices, photodetectors, and light-emitting diodes. However, it is often challenging to physically create the nanophotonic designs required to engineer the optical properties of devices. Here, we present a platform based on crystalline indium phosphide that enables thin-film nanophotonic structures with physical morphologies that are impossible to achieve through conventional state-of-the-art material growth techniques. Here, nanostructured InP thin films have been demonstrated on non-epitaxial alumina inverted nanocone (i-cone) substrates via a low-cost and scalable thin-film vapor-liquid-solid growth technique. In this process, indium films are first evaporated onto the i-cone structures in the desired morphology, followed by a high-temperature step that causes a phase transformation of the indium into indium phosphide, preserving the original morphology of the deposited indium. Through this approach, a wide variety of nanostructured film morphologies are accessible using only control over evaporation process variables. Critically, the as-grown nanotextured InP thin films demonstrate excellent optoelectronic properties, suggesting this platform is promising for future high-performance nanophotonic devices.

A melting-point-of gallium apparatus for thermometer calibration.

PubMed

Sostman, H E; Manley, K A

1978-08-01

We have investigated the equilibrium melting point of gallium as a temperature fixed-point at which to calibrate small thermistor thermometers, such as those used to measure temperature in enzyme reaction analysis and other temperature-dependent biological assays. We have determined that the melting temperature of "6N" (99.999% pure) gallium is 29.770 +/- 0.002 degrees C, and that the constant-temperature plateau can be prolonged for several hours. We have designed a simple automated apparatus that exploits this phenomenon and that permits routine calibration verification of thermistor temperature probes throughout the laboratory day. We describe the physics of the gallium melt, and the design and use of the apparatus.

On the photon annealing of silicon-implanted gallium-nitride layers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seleznev, B. I., E-mail: Boris.Seleznev@novsu.ru; Moskalev, G. Ya.; Fedorov, D. G.

2016-06-15

The conditions for the formation of ion-doped layers in gallium nitride upon the incorporation of silicon ions followed by photon annealing in the presence of silicon dioxide and nitride coatings are analyzed. The conditions of the formation of ion-doped layers with a high degree of impurity activation are established. The temperature dependences of the surface concentration and mobility of charge carriers in ion-doped GaN layers annealed at different temperatures are studied.

Indium phosphide space solar cell research: Where we are and where we are going

NASA Technical Reports Server (NTRS)

Jain, R. K.; Flood, D. J.; Weinberg, Irving

1995-01-01

Indium phosphide is considered to be a strong contender for many photovoltaic space applications because of its radiation resistance and its potential for high efficiency. An overview of recent progress is presented, and possible future research directions for indium phosphide space solar cells are discussed. The topics considered include radiation damage studies and space flight experiments.

Use of continuous renal replacement therapy in acute aluminum phosphide poisoning: a novel therapy.

PubMed

Nasa, Prashant; Gupta, Ankur; Mangal, Kishore; Nagrani, S K; Raina, Sanjay; Yadav, Rohit

2013-09-01

Aluminum phosphide is most common cause of poisoning in northern India. There is no specific antidote available and management of such cases is mainly supportive with high mortality. We present two cases of severe acute aluminium phosphide poisoning where continuous renal replacement therapy (CRRT) was started early along with other resuscitative measures and both the patients survived.

Synthesis and x-ray characterization of cobalt phosphide (Co₂P) nanorods for the oxygen reduction reaction

DOE PAGES

Doan-Nguyen, Vicky V.T.; Su, Dong; Zhang, Sen; ...

2015-07-14

Low temperature fuel cells are clean, effective alternative fuel conversion technology. Oxygen reduction reaction (ORR) at the fuel cell cathode has required Pt as the electrocatalyst for high activity and selectivity of the four-electron reaction pathway. Targeting a less expensive, earth abundant alternative, we have developed the synthesis of cobalt phosphide (Co₂P) nanorods for ORR. Characterization techniques that include total X-ray scattering and extended X-ray absorption fine structure revealed a deviation of the nanorods from bulk crystal structure with a contraction along the b orthorhombic lattice parameter. The carbon supported nanorods have comparable activity but are remarkably more stable thanmore » conventional Pt catalysts for the oxygen reduction reaction in alkaline environments.« less

On two alternative mechanisms of ethane activation over ZSM-5 zeolite modified by Zn2+ and Ga1+ cations.

PubMed

Kazansky, V B; Subbotina, I R; Rane, N; van Santen, R A; Hensen, E J M

2005-08-21

The activation of ethane over zinc- and gallium-modified HZSM-5 dehydrogenation catalysts was studied by diffuse reflectance infrared spectroscopy. Hydrocarbon activation on HZSM-5 modified by bivalent Zn and univalent Ga cations proceeds via two distinctly different mechanisms. The stronger molecular adsorption of ethane by the acid-base pairs formed by distantly separated cationic Zn2+ and basic oxygen sites results already at room temperature in strong polarizability of adsorbed ethane and subsequent heterolytic dissociative adsorption at moderate temperatures. In contrast, molecular adsorption of ethane on Ga+ cations is weak. At high temperatures dissociative hydrocarbon adsorption takes place, resulting in the formation of ethyl and hydride fragments coordinating to the cationic gallium species. Whereas in the zinc case a Brønsted acid proton is formed upon ethane dissociation, decomposition of the ethyl fragment on gallium results in gallium dihydride species and does not lead to Brønsted acid protons. This difference in alkane activation has direct consequences for hydrocarbon conversions involving dehydrogenation.

First-principles melting of gallium clusters down to nine atoms: structural and electronic contributions to melting.

PubMed

Steenbergen, Krista G; Gaston, Nicola

2013-10-07

First-principles Born-Oppenheimer molecular dynamics simulations of small gallium clusters, including parallel tempering, probe the distinction between cluster and molecule in the size range of 7-12 atoms. In contrast to the larger sizes, dynamic measures of structural change at finite temperature demonstrate that Ga7 and Ga8 do not melt, suggesting a size limit to melting in gallium exists at 9 atoms. Analysis of electronic structure further supports this size limit, additionally demonstrating that a covalent nature cannot be identified for clusters larger than the gallium dimer. Ga9, Ga10 and Ga11 melt at greater-than-bulk temperatures, with no evident covalent character. As Ga12 represents the first small gallium cluster to melt at a lower-than-bulk temperature, we examine the structural properties of each cluster at finite temperature in order to probe both the origins of greater-than-bulk melting, as well as the significant differences in melting temperatures induced by a single atom addition. Size-sensitive melting temperatures can be explained by both energetic and entropic differences between the solid and liquid phases for each cluster. We show that the lower-than-bulk melting temperature of the 12-atom cluster can be attributed to persistent pair bonding, reminiscent of the pairing observed in α-gallium. This result supports the attribution of greater-than-bulk melting in gallium clusters to the anomalously low melting temperature of the bulk, due to its dimeric structure.

Investigation of the thermophysical properties of high-melting materials with the aid of a complex of instruments

NASA Technical Reports Server (NTRS)

Bolgar, A. S.; Gordiyenko, S. P.; Guseva, Y. A.; Turchanin, A. G.; Fenochka, B. V.; Fesenko, V. V.

1984-01-01

The evaporation rate, vapor pressure, heats of evaporation reaction (sublimation, dissociation), enthalpy, electrical resistance, heat capacity, emissivity, and heat conductivity of various carbides, borides, sulfides, nitrides, selenides, and phosphides were investigated. A set of high temperature high vacuum devices, calorimeters (designed for operation at 400 to 1300 K and from 1200 K), and mass spectrometers, most of which were specially developed for these studies, is described.

Ga[OSi(O(t)Bu)3]3·THF, a thermolytic molecular precursor for high surface area gallium-containing silica materials of controlled dispersion and stoichiometry.

PubMed

Dombrowski, James P; Johnson, Gregory R; Bell, Alexis T; Tilley, T Don

2016-07-05

The molecular precursor tris[(tri-tert-butoxy)siloxy]gallium, as the tetrahydrofuran adduct Ga[OSi(O(t)Bu)3]3·THF (), was synthesized via the salt metathesis reaction of gallium trichloride with NaOSi(O(t)Bu)3. This complex serves as a model for isolated gallium in a silica framework. Complex decomposes thermally in hydrocarbon solvent, eliminating isobutylene, water, and tert-butanol to generate high surface area gallium-containing silica at low temperatures. When thermal decomposition was performed in the presence of P-123 Pluronic as a templating agent the generated material displayed uniform vermicular pores. Textural mesoporosity was evident in untemplated material. Co-thermolysis of with HOSi(O(t)Bu)3 in the presence of P-123 Pluronic led to materials with Ga : Si ratios ranging from 1 : 3 to 1 : 50, denoted UCB1-GaSi3, UCB1-GaSi10, UCB1-GaSi20 and UCB1-GaSi50. After calcination at 500 °C these materials exhibited decreasing surface areas and broadening pore distributions with increasing silicon content, indicating a loss of template effects. The position and dispersion of the gallium in UCB1-GaSi materials was investigated using (71)Ga MAS-NMR, powder XRD, and STEM/EDS elemental mapping. The results indicate a high degree of gallium dispersion in all samples, with gallium oxide clusters or oligomers present at higher gallium content.

Optical properties of nanowire metamaterials with gain

NASA Astrophysics Data System (ADS)

Lima, Joaquim; Adam, Jost; Rego, Davi; Esquerre, Vitaly; Bordo, Vladimir

2016-11-01

The transmittance, reflectance and absorption of a nanowire metamaterial with optical gain are numerically simulated and investigated. It is assumed that the metamaterial is represented by aligned silver nanowires embedded into a semiconductor matrix, made of either silicon or gallium phosphide. The gain in the matrix is modeled by adding a negative imaginary part to the dielectric function of the semiconductor. It is found that the optical coefficients of the metamaterial depend on the gain magnitude in a non-trivial way: they can both increase and decrease with gain depending on the lattice constant of the metamaterial. This peculiar behavior is explained by the field redistribution between the lossy metal nanowires and the amplifying matrix material. These findings are significant for a proper design of nanowire metamaterials with low optical losses for diverse applications.

Optimization Of Shear Modes To Produce Enhanced Bandwidth In Ghz GaP Bragg Cells

NASA Astrophysics Data System (ADS)

Soos, J., I.; Rosemeier, R. G.; Rosenbaum, J.

1988-02-01

Applications of Gallium Phosphide (GaP) acousto-optic devices, at wavelengths from 570nm - 1.06um seem to be ideal for fiber optic modulators, scanners, deflectors, frequency shifters, Q-switches and mode lockers. One of the major applications are for RF spectrometers in early warning radar receivers and auto-correlators. Longitudinal GaP acousto-optic Bragg cells which have respectively operational frequencies in the range of 200 MHz - 3 GHz and diffraction efficiencies in the range of 120%/RF watt to 1%/RF watt have recently been fabricated. Comparatively, shear GaP devices which have operational frequencies in the range of 200 MHz to 2 GHz and diffraction efficiencies from 80%/RF watt to 7%/RF watt have also been constructed.

Size-selective breaking of the core-shell structure of gallium nanoparticles.

PubMed

Catalán Gómez, Sergio; Redondo-Cubero, Andres; Palomares Simon, Francisco Javier; Vazquez Burgos, Luis; Nogales, Emilio; Nucciarelli, Flavio; Mendez, Bianchi; Gordillo, Nuria; Pau, Jose Luis

2018-06-11

Core-shell gallium nanoparticles (Ga NPs) have recently been proposed as an ultraviolet plasmonic material for different applications but only at room temperature. Here, the thermal stability as a function of the size of the NPs is reported over a wide range of temperatures. We analyse the chemical and structural properties of the oxide shell by x-ray photoelectron spectroscopy and atomic force microscopy. We demonstrate the inverse dependence of the shell breaking temperature with the size of the NPs. Spectroscopic ellipsometry is used for tracking the rupture and its mechanism is systematically investigated by scanning electron microscopy, grazing incidence x-ray diffraction and cathodoluminescence. Taking advantage of the thermal stability of the NPs, we perform complete oxidations that lead to homogenous gallium oxide NPs. Thus, this study set the physical limits of Ga NPs to last at high temperatures, and opens up the possibility to achieve totally oxidized NPs while keeping their sphericity. © 2018 IOP Publishing Ltd.

Ambient temperature deposition of gallium nitride/gallium oxynitride from a deep eutectic electrolyte, under potential control.

PubMed

Sarkar, Sujoy; Sampath, S

2016-05-11

A ternary, ionically conducting, deep eutectic solvent based on acetamide, urea and gallium nitrate is reported for the electrodeposition of gallium nitride/gallium indium nitride under ambient conditions; blue and white light emitting photoluminescent deposits are obtained under potential control.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mendoza-Garcia, Adriana; Zhu, Huiyuan; Yu, Yongsheng

Presented here is a facile approach to bimetallic phosphides, Co-Fe-P, via high-temperature (300°C) reaction between Co-Fe-O nanoparticles and trioctylphosphine. The growth of Co-Fe-P from the Co-Fe-O is anisotropic. As a result, Co-Fe-P nanorods (from the polyhedral Co-Fe-O nanoparticles) and sea-urchin-like Co-Fe-P (from the cubic Co-Fe-O nanoparticles) are synthesized with both nanorod and the sea-urchin-arm dimensions controlled by Co/Fe ratios. The Co-Fe-P structure, especially the sea-urchin-like (Co 0.54Fe 0.46) 2P, shows enhanced catalysis for oxygen evolution reaction in KOH with its catalytic efficiency surpassing Ir catalyst. Our synthesis is simple and may be readily extended to the preparation of other multimetallicmore » phosphides for important catalysis and energy storage applications.« less

High-temperature performance of gallium-nitride-based pin alpha-particle detectors grown on sapphire substrates

NASA Astrophysics Data System (ADS)

Zhu, Zhifu; Zhang, Heqiu; Liang, Hongwei; Tang, Bin; Peng, Xincun; Liu, Jianxun; Yang, Chao; Xia, Xiaochuan; Tao, Pengcheng; Shen, Rensheng; Zou, Jijun; Du, Guotong

2018-06-01

The temperature-dependent radiation-detection performance of an alpha-particle detector that was based on a gallium-nitride (GaN)-based pin structure was studied from 290 K to 450 K. Current-voltage-temperature measurements (I-V-T) of the reverse bias show the exponential dependence of leakage currents on the voltage and temperature. The current transport mechanism of the GaN-based pin diode from the reverse bias I-V fitting was analyzed. The temperature-dependent pulse-height spectra of the detectors were studied using an 241 Am alpha-particle source at a reverse bias of 10 V, and the peak positions shifted from 534 keV at 290 K to 490 keV at 450 K. The variation of full width at half maximum (FWHM) from 282 keV at 290 K to 292 keV at 450 K is almost negligible. The GaN-based pin detectors are highly promising for high-temperature environments up to 450 K.

Crystal growth of compound semiconductors in a low-gravity environment (InGaAs crystals) (M-22)

NASA Technical Reports Server (NTRS)

Tatsumi, Masami

1993-01-01

Compound semiconductor crystals, such as gallium arsenide and indium phosphide crystals, have many interesting properties that silicon crystals lack, and they are expected to be used as materials for optic and/or electro-optic integrated devices. Generally speaking, alloy semiconductors, which consist of more than three elements, demonstrate new functions. For example, values of important parameters, such as lattice constant and emission wavelength, can be chosen independently. However, as it is easy for macroscopic and/or microscopic fluctuations of composition to occur in alloy semiconductor crystals, it is difficult to obtain crystals having homogeneous properties. Macroscopic change of composition in a crystal is caused by the segregation phenomenon. This phenomenon is due to a continuous change in the concentration of constituent elements at the solid-liquid interfacing during solidification. On Earth, attempts were made to obtain a crystal with homogeneous composition by maintaining a constant melt composition near the solid-liquid interface, through suppression of the convection flow of the melt by applying a magnetic field. However, the attempt was not completely successful. Convective flow does not occur in microgravity because the gravity in space is from four to six orders of magnitude less than that on Earth. In such a case, mass transfer in the melt is dominated by the diffusion phenomenon. So, if crystal growth is carried out at a rate that is higher than the rate of mass transfer due to this phenomenon, it is expected that crystals having a homogeneous composition will be obtained. In addition, it is also possible that microscopic composition fluctuations (striation) may disappear because microscopic fluctuations diminish in the absence of convection. We are going to grow a bulk-indium gallium arsenide (InGaAs) crystal using the gradient heating furnace (GHF) in the first material processing test (FMPT). The structure of the sample is shown where InGaAs polycrystals in a crucible are doubly sealed in two quartz tubes for safety. The GHF consists of two zones, namely, high temperature and low temperature zones, which results in a large temperature gradient at the interface. Crystal growth is performed by moving the furnace (i.e. the temperature profile) from the left to right at a definite rate. Thus, we will grow crystals both on Earth and in space under the same conditions. As previously described, it is possible to obtain good quality crystals which are homogeneous in composition both macroscopically and microscopically due to the lack of convection in space. We are planning to study the effects of convection on crystal growth from a melt by comparing and characterizing the properties of crystals grown on Earth with those grown in space.

Two-Dimensional Phosphorene-Derived Protective Layers on a Lithium Metal Anode for Lithium-Oxygen Batteries.

PubMed

Kim, Youngjin; Koo, Dongho; Ha, Seongmin; Jung, Sung Chul; Yim, Taeeun; Kim, Hanseul; Oh, Seung Kyo; Kim, Dong-Min; Choi, Aram; Kang, Yongku; Ryu, Kyoung Han; Jang, Minchul; Han, Young-Kyu; Oh, Seung M; Lee, Kyu Tae

2018-05-04

Lithium-oxygen (Li-O 2 ) batteries are desirable for electric vehicles because of their high energy density. Li dendrite growth and severe electrolyte decomposition on Li metal are, however, challenging issues for the practical application of these batteries. In this connection, an electrochemically active two-dimensional phosphorene-derived lithium phosphide is introduced as a Li metal protective layer, where the nanosized protective layer on Li metal suppresses electrolyte decomposition and Li dendrite growth. This suppression is attributed to thermodynamic properties of the electrochemically active lithium phosphide protective layer. The electrolyte decomposition is suppressed on the protective layer because the redox potential of lithium phosphide layer is higher than that of electrolyte decomposition. Li plating is thermodynamically unfavorable on lithium phosphide layers, which hinders Li dendrite growth during cycling. As a result, the nanosized lithium phosphide protective layer improves the cycle performance of Li symmetric cells and Li-O 2 batteries with various electrolytes including lithium bis(trifluoromethanesulfonyl)imide in N,N-dimethylacetamide. A variety of ex situ analyses and theoretical calculations support these behaviors of the phosphorene-derived lithium phosphide protective layer.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blanchard, I.; Badro, J.; Siebert, J.

We present gallium concentration (normalized to CI chondrites) in the mantle is at the same level as that of lithophile elements with similar volatility, implying that there must be little to no gallium in Earth's core. Metal-silicate partitioning experiments, however, have shown that gallium is a moderately siderophile element and should be therefore depleted in the mantle by core formation. Moreover, gallium concentrations in the mantle (4 ppm) are too high to be only brought by the late veneer; and neither pressure, nor temperature, nor silicate composition has a large enough effect on gallium partitioning to make it lithophile. Wemore » therefore systematically investigated the effect of core composition (light element content) on the partitioning of gallium by carrying out metal–silicate partitioning experiments in a piston–cylinder press at 2 GPa between 1673 K and 2073 K. Four light elements (Si, O, S, C) were considered, and their effect was found to be sufficiently strong to make gallium lithophile. The partitioning of gallium was then modeled and parameterized as a function of pressure, temperature, redox and core composition. A continuous core formation model was used to track the evolution of gallium partitioning during core formation, for various magma ocean depths, geotherms, core light element contents, and magma ocean composition (redox) during accretion. The only model for which the final gallium concentration in the silicate Earth matched the observed value is the one involving a light-element rich core equilibrating in a FeO-rich deep magma ocean (>1300 km) with a final pressure of at least 50 GPa. More specifically, the incorporation of S and C in the core provided successful models only for concentrations that lie far beyond their allowable cosmochemical or geophysical limits, whereas realistic O and Si amounts (less than 5 wt.%) in the core provided successful models for magma oceans deeper that 1300 km. In conclusion, these results offer a strong argument for an O- and Si-rich core, formed in a deep terrestrial magma ocean, along with oxidizing conditions.« less

Metal phosphide catalysts and methods for making the same and uses thereof

DOEpatents

Habas, Susan Ellen; Wang, Jun; Ruddy, Daniel A.; Baddour, Frederick Raymond Gabriel; Schaidle, Joshua

2017-05-02

The present disclosure relates to a method that includes heating a mixture that includes a metal phenylphosphine-containing precursor that includes at least one of Mo(PPh.sub.3).sub.2(CO).sub.4, Pd(PPh.sub.3).sub.4, Ru(PPh.sub.3).sub.3Cl.sub.2, Ru(PPh.sub.3).sub.2(CO).sub.2Cl.sub.2, Co(PPh.sub.3)(CO).sub.2(NO), and/or Rh(PPh.sub.3).sub.2(CO)Cl, a surfactant, and a solvent. The heating is to a target temperature to form a heated mixture containing a metal phosphide nanoparticle that includes at least one of MoP, Ru.sub.2P, Co.sub.2P, Rh.sub.2P, and/or Pd.sub.3P, and the metal phosphide nanoparticle is not hollow.

Indium phosphide nanowires and their applications in optoelectronic devices.

PubMed

Zafar, Fateen; Iqbal, Azhar

2016-03-01

Group IIIA phosphide nanocrystalline semiconductors are of great interest among the important inorganic materials because of their large direct band gaps and fundamental physical properties. Their physical properties are exploited for various potential applications in high-speed digital circuits, microwave and optoelectronic devices. Compared to II-VI and I-VII semiconductors, the IIIA phosphides have a high degree of covalent bonding, a less ionic character and larger exciton diameters. In the present review, the work done on synthesis of III-V indium phosphide (InP) nanowires (NWs) using vapour- and solution-phase approaches has been discussed. Doping and core-shell structure formation of InP NWs and their sensitization using higher band gap semiconductor quantum dots is also reported. In the later section of this review, InP NW-polymer hybrid material is highlighted in view of its application as photodiodes. Lastly, a summary and several different perspectives on the use of InP NWs are discussed.

Strongly luminescent InP/ZnS core-shell nanoparticles.

PubMed

Haubold, S; Haase, M; Kornowski, A; Weller, H

2001-05-18

The wide-bandgap semiconducting material, zinc sulfide, has been coated on indium phosphide nanoclusters to a 1-2-Å thickness. The resulting InP-ZnS core-shell particle (as shown in the TEM image; scale 1 cm=5 nm) exhibits bright luminescence at room temperature with quantum efficiencies as high as 23 %. © 2001 WILEY-VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany.

Migration mechanisms and diffusion barriers of vacancies in Ga2O3

NASA Astrophysics Data System (ADS)

Kyrtsos, Alexandros; Matsubara, Masahiko; Bellotti, Enrico

2017-06-01

We employ the nudged elastic band and the dimer methods within the standard density functional theory (DFT) formalism to study the migration of the oxygen and gallium vacancies in the monoclinic structure of β -Ga2O3 . We identify all the first nearest neighbor paths and calculate the migration barriers for the diffusion of the oxygen and gallium vacancies. We also identify the metastable sites of the gallium vacancies which are critical for the diffusion of the gallium atoms. The migration barriers for the diffusion of the gallium vacancies are lower than the migration barriers for oxygen vacancies by 1 eV on average, suggesting that the gallium vacancies are mobile at lower temperatures. Using the calculated migration barriers we estimate the annealing temperature of these defects within the harmonic transition state theory formalism, finding excellent agreement with the observed experimental annealing temperatures. Finally, we suggest the existence of percolation paths which enable the migration of the species without utilizing all the migration paths of the crystal.

Proof-of-Concept Experiments on a Gallium-Based Ignitron for Pulsed Power Applications

NASA Technical Reports Server (NTRS)

Ali, H. K.; Hanson, V. S.; Polzin, K. A.; Pearson, J. B.

2015-01-01

Ignitrons are electrical switching devices that operate at switching times that are on the order of microseconds, can conduct high currents of thousands of amps, and are capable of holding off tens of thousands of volts between pulses. They consist of a liquid metal pool within an evacuated tube that serves both the cathode and the source of atoms and electrons for an arc discharge. Facing the liquid metal pool is an anode suspended above the cathode, with a smaller ignitor electrode tip located just above the surface of the cathode. The ignitron can be charged to significant voltages, with a potential difference of thousands of volts between anode and cathode. When an ignition pulse is delivered from the ignitor electrode to the cathode, a small amount of the liquid metal is vaporized and subsequently ionized, with the high voltage between the anode and cathode causing the gas to bridge the gap between the two electrodes. The electrons and ions move rapidly towards the anode and cathode, respectively, with the ions liberating still more atoms from the liquid metal cathode surface as a high-current plasma arc discharge is rapidly established. This arc continues in a self-sustaining fashion until the potential difference between the anode and cathode drops below some critical value. Ignitrons have been used in a variety of pulsed power applications, including the railroad industry, industrial chemical processing, and high-power arc welding. In addition, they might prove useful in terrestrial power grid applications, serving as high-current fault switches, quickly shunting dangerous high-current or high-voltage spikes safely to ground. The motivation for this work stemmed from the fact that high-power, high-reliability, pulsed power devices like the ignitron have been used for ground testing in-space pulsed electric thruster technologies, and the continued use of ignitrons could prove advantageous to the future development and testing of such thrusters. Previous ignitron designs have used mercury as the liquid metal cathode, owing to its presence as a liquid at room temperatures and a vapor pressure of 10 Pa (75 mtorr) at room temperature. While these are favorable properties, there are obvious environmental and personal safety concerns with the storage, handling, and use of mercury and its compounds. The purpose of the present work was to fabricate and test an ignitron that used as its cathode an alternate liquid metal that was safe to handle and store. To that end, an ignitron test article that used liquid gallium as the cathode material was developed and tested. Gallium is a metal that has a melting temperature of 29.76 C, which is slightly above room temperature, and a boiling point of over 2,300 C at atmospheric pressure. This property makes gallium the element with the largest relative difference between melting and boiling points. Gallium has a limited role in biology, and when ingested, it will be subsequently processed by the body and expelled rather than accumulating to toxic levels. The next section of this Technical Memorandum (TM) provides background information on the development of mercury-based ignitrons, which serves as the starting point for the development of the gallium-based variant. Afterwards, the experimental hardware and setup used in proof-of-concept testing of a basic gallium ignitron are presented. Experimental data, consisting of discharge voltage and current waveforms as well as high-speed imaging of the gallium arc discharge in the gallium ignitron test article, are presented to demonstrate the efficacy of the concept. Discussion of the data and suggestions on improvements for future iterations of the design are presented in the final two sections of this TM.

Effect of low NH3 flux towards high quality semi-polar (11-22) GaN on m-plane sapphire via MOCVD

NASA Astrophysics Data System (ADS)

Omar, Al-Zuhairi; Shuhaimi Bin Abu Bakar, Ahmad; Makinudin, Abdullah Haaziq Ahmad; Khudus, Muhammad Imran Mustafa Abdul; Azman, Adreen; Kamarundzaman, Anas; Supangat, Azzuliani

2018-05-01

The effect of ammonia flux towards the quality of the semi-polar (11-22) gallium nitride thin film on m-plane (10-10) sapphire is presented. Semi-polar (11-22) gallium nitride epi-layers were obtained using a two-step growth method, consisting of high temperature aluminum nitride followed by gallium nitride via metal organic chemical vapor deposition. The surface morphology analysis via field emission scanning electron microscopy and atomic force microscopy of the semi-polar (11-22) gallium nitride has shown that low ammonia flux promotes two-dimensional growth with low surface roughness of 4.08 nm. A dominant diffraction peak of (11-22) gallium nitride was also observed via X-ray diffraction upon utilizing low ammonia flux. The on- and off-axis X-ray rocking curve measurements illustrate the enhancement of the crystal quality, which might result from the reduction of the basal stacking faults and perfect dislocation. The full width half maximum values were reduced by at least 15% for both on- and off-axis measurements.

Low-Temperature Photochemically Activated Amorphous Indium-Gallium-Zinc Oxide for Highly Stable Room-Temperature Gas Sensors.

PubMed

Jaisutti, Rawat; Kim, Jaeyoung; Park, Sung Kyu; Kim, Yong-Hoon

2016-08-10

We report on highly stable amorphous indium-gallium-zinc oxide (IGZO) gas sensors for ultraviolet (UV)-activated room-temperature detection of volatile organic compounds (VOCs). The IGZO sensors fabricated by a low-temperature photochemical activation process and exhibiting two orders higher photocurrent compared to conventional zinc oxide sensors, allowed high gas sensitivity against various VOCs even at room temperature. From a systematic analysis, it was found that by increasing the UV intensity, the gas sensitivity, response time, and recovery behavior of an IGZO sensor were strongly enhanced. In particular, under an UV intensity of 30 mW cm(-2), the IGZO sensor exhibited gas sensitivity, response time and recovery time of 37%, 37 and 53 s, respectively, against 750 ppm concentration of acetone gas. Moreover, the IGZO gas sensor had an excellent long-term stability showing around 6% variation in gas sensitivity over 70 days. These results strongly support a conclusion that a low-temperature solution-processed amorphous IGZO film can serve as a good candidate for room-temperature VOCs sensors for emerging wearable electronics.

Precision blackbody sources for radiometric standards.

PubMed

Sapritsky, V I; Khlevnoy, B B; Khromchenko, V B; Lisiansky, B E; Mekhontsev, S N; Melenevsky, U A; Morozova, S P; Prokhorov, A V; Samoilov, L N; Shapoval, V I; Sudarev, K A; Zelener, M F

1997-08-01

The precision blackbody sources developed at the All-Russian Institute for Optical and Physical Measurements (Moscow, Russia) and their characteristics are analyzed. The precision high-temperature graphite blackbody BB22p, large-area high-temperature pyrolytic graphite blackbody BB3200pg, middle-temperature graphite blackbody BB2000, low-temperature blackbody BB300, and gallium fixed-point blackbody BB29gl and their characteristics are described.

Lattice Matched Carbide–Phosphide Composites with Superior Electrocatalytic Activity and Stability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Regmi, Yagya N.; Roy, Asa; King, Laurie A.

Composites of electrocatalytically active transition-metal compounds present an intriguing opportunity toward enhanced activity and stability. Here, to identify potentially scalable pairs of a catalytically active family of compounds, we demonstrate that phosphides of iron, nickel, and cobalt can be deposited on molybdenum carbide to generate nanocrystalline heterostructures. Composites synthesized via solvothermal decomposition of metal acetylacetonate salts in the presence of highly dispersed carbide nanoparticles show hydrogen evolution activities comparable to those of state-of-the-art non-noble metal catalysts. Investigation of the spent catalyst using high resolution microscopy and elemental analysis reveals that formation of carbide–phosphide composite prevents catalyst dissolution in acid electrolyte.more » Lattice mismatch between the two constituent electrocatalysts can be used to rationally improve electrochemical stability. Among the composites of iron, nickel, and cobalt phosphide, iron phosphide displays the lowest degree of lattice mismatch with molybdenum carbide and shows optimal electrochemical stability. Turnover rates of the composites are higher than that of the carbide substrate and compare favorably to other electrocatalysts based on earth-abundant elements. Lastly, our findings will inspire further investigation into composite nanocrystalline electrocatalysts that use molybdenum carbide as a stable catalyst support.« less

Lattice Matched Carbide–Phosphide Composites with Superior Electrocatalytic Activity and Stability

DOE PAGES

Regmi, Yagya N.; Roy, Asa; King, Laurie A.; ...

2017-10-19

Composites of electrocatalytically active transition-metal compounds present an intriguing opportunity toward enhanced activity and stability. Here, to identify potentially scalable pairs of a catalytically active family of compounds, we demonstrate that phosphides of iron, nickel, and cobalt can be deposited on molybdenum carbide to generate nanocrystalline heterostructures. Composites synthesized via solvothermal decomposition of metal acetylacetonate salts in the presence of highly dispersed carbide nanoparticles show hydrogen evolution activities comparable to those of state-of-the-art non-noble metal catalysts. Investigation of the spent catalyst using high resolution microscopy and elemental analysis reveals that formation of carbide–phosphide composite prevents catalyst dissolution in acid electrolyte.more » Lattice mismatch between the two constituent electrocatalysts can be used to rationally improve electrochemical stability. Among the composites of iron, nickel, and cobalt phosphide, iron phosphide displays the lowest degree of lattice mismatch with molybdenum carbide and shows optimal electrochemical stability. Turnover rates of the composites are higher than that of the carbide substrate and compare favorably to other electrocatalysts based on earth-abundant elements. Lastly, our findings will inspire further investigation into composite nanocrystalline electrocatalysts that use molybdenum carbide as a stable catalyst support.« less

Remote plasma enhanced chemical vapor deposition of GaP with in situ generation of phosphine precursors

NASA Technical Reports Server (NTRS)

Choi, S. W.; Lucovsky, G.; Bachmann, Klaus J.

1993-01-01

Thin homoepitaxial films of gallium phosphide (GaP) were grown by remote plasma enhanced chemical vapor deposition utilizing in situ generated phosphine precursors. The GaP forming reaction is kinetically controlled with an activation energy of 0.65 eV. The increase of the growth rate with increasing radio frequency (rf) power between 20 and 100 W is due to the combined effects of increasingly complete excitation and the spatial extension of the glow discharge toward the substrate, however, the saturation of the growth rate at even higher rf power indicates the saturation of the generation rate of phosphine precursors at this condition. Slight interdiffusion of P into Si and Si into GaP is indicated from GaP/Si heterostructures grown under similar conditions as the GaP homojunctions.

Remote plasma enhanced chemical vapor deposition of GaP with in situ generation of phosphine precursors

NASA Technical Reports Server (NTRS)

Choi, S. W.; Lucovsky, G.; Bachmann, K. J.

1992-01-01

Thin homoepitaxial films of gallium phosphide (GaP) have been grown by remote plasma enhanced chemical vapor deposition utilizing in situ-generated phosphine precursors. The GaP forming reaction is kinetically controlled with an activation energy of 0.65 eV. The increase of the growth rate with increasing radio frequency (RF) power between 20 and 100 W is due to the combined effects of increasingly complete excitation and the spatial extension of the glow discharge toward the substrate; however, the saturation of the growth rate at even higher RF power indicates the saturation of the generation rate of phosphine precursors at this condition. Slight interdiffusion of P into Si and Si into GaP is indicated from GaP/Si heterostructures grown under similar conditions as the GaP homojunctions.

The Adjunctive Soft-Tissue Diode Laser in Orthodontics.

PubMed

Borzabadi-Farahani, Ali

2017-04-01

Lasers are a relatively new addition to the orthodontist's armamentarium. This article reviews the fundamental basic science of available soft-tissue lasers, with an emphasis on diode lasers, and discusses various adjunct applications of the diode laser for soft-tissue orthodontic procedures. Diode lasers function by cutting with an initiated hot tip and produce minimal to no interaction with healthy dental hard tissue, making them suitable for soft-tissue procedures. The contact cutting mode provides enhanced bloodless site visibility and facility to perform delicate soft tissue procedures, which is important in areas with difficult access. Such adjunctive uses include laser gingivectomy to improve oral hygiene or bracket positioning, esthetic laser gingival recontouring, and laser exposure of superficially impacted teeth. Selected cases treated with a 940-nm indium-gallium-arsenide-phosphide (InGaAsP) diode laser will be presented.

Fiber Bragg grating sensor interrogators on chip: challenges and opportunities

NASA Astrophysics Data System (ADS)

Marin, Yisbel; Nannipieri, Tiziano; Oton, Claudio J.; Di Pasquale, Fabrizio

2017-04-01

In this paper we present an overview of the current efforts towards integration of Fiber Bragg Grating (FBG) sensor interrogators. Different photonic integration platforms will be discussed, including monolithic planar lightwave circuit technology, silicon on insulator (SOI), indium phosphide (InP) and gallium arsenide (GaAs) material platforms. Also various possible techniques for wavelength metering and methods for FBG multiplexing will be discussed and compared in terms of resolution, dynamic performance, multiplexing capabilities and reliability. The use of linear filters, array waveguide gratings (AWG) as multiple linear filters and AWG based centroid signal processing techniques will be addressed as well as interrogation techniques based on tunable micro-ring resonators and Mach-Zehnder interferometers (MZI) for phase sensitive detection. The paper will also discuss the challenges and perspectives of photonic integration to address the increasing requirements of several industrial applications.

Ultra-low threshold gallium nitride photonic crystal nanobeam laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Niu, Nan, E-mail: nanniu@fas.harvard.edu; Woolf, Alexander; Wang, Danqing

2015-06-08

We report exceptionally low thresholds (9.1 μJ/cm{sup 2}) for room temperature lasing at ∼450 nm in optically pumped Gallium Nitride (GaN) nanobeam cavity structures. The nanobeam cavity geometry provides high theoretical Q (>100 000) with small modal volume, leading to a high spontaneous emission factor, β = 0.94. The active layer materials are Indium Gallium Nitride (InGaN) fragmented quantum wells (fQWs), a critical factor in achieving the low thresholds, which are an order-of-magnitude lower than obtainable with continuous QW active layers. We suggest that the extra confinement of photo-generated carriers for fQWs (compared to QWs) is responsible for the excellent performance.

The surface tension of liquid gallium

NASA Technical Reports Server (NTRS)

Hardy, S. C.

1985-01-01

The surface tension of liquid gallium has been measured using the sessile drop technique in an Auger spectrometer. The experimental method is described. The surface tension in mJ/sq m is found to decrease linearly with increasing temperature and may be represented as 708-0.66(T-29.8), where T is the temperature in centigrade. This result is of interest because gallium has been suggested as a model fluid for Marangoni flow experiments. In addition, the surface tension is of technological significance in the processing of compound semiconductors involving gallium.

Composition of the core from gallium metal–silicate partitioning experiments

DOE PAGES

Blanchard, I.; Badro, J.; Siebert, J.; ...

2015-07-24

We present gallium concentration (normalized to CI chondrites) in the mantle is at the same level as that of lithophile elements with similar volatility, implying that there must be little to no gallium in Earth's core. Metal-silicate partitioning experiments, however, have shown that gallium is a moderately siderophile element and should be therefore depleted in the mantle by core formation. Moreover, gallium concentrations in the mantle (4 ppm) are too high to be only brought by the late veneer; and neither pressure, nor temperature, nor silicate composition has a large enough effect on gallium partitioning to make it lithophile. Wemore » therefore systematically investigated the effect of core composition (light element content) on the partitioning of gallium by carrying out metal–silicate partitioning experiments in a piston–cylinder press at 2 GPa between 1673 K and 2073 K. Four light elements (Si, O, S, C) were considered, and their effect was found to be sufficiently strong to make gallium lithophile. The partitioning of gallium was then modeled and parameterized as a function of pressure, temperature, redox and core composition. A continuous core formation model was used to track the evolution of gallium partitioning during core formation, for various magma ocean depths, geotherms, core light element contents, and magma ocean composition (redox) during accretion. The only model for which the final gallium concentration in the silicate Earth matched the observed value is the one involving a light-element rich core equilibrating in a FeO-rich deep magma ocean (>1300 km) with a final pressure of at least 50 GPa. More specifically, the incorporation of S and C in the core provided successful models only for concentrations that lie far beyond their allowable cosmochemical or geophysical limits, whereas realistic O and Si amounts (less than 5 wt.%) in the core provided successful models for magma oceans deeper that 1300 km. In conclusion, these results offer a strong argument for an O- and Si-rich core, formed in a deep terrestrial magma ocean, along with oxidizing conditions.« less

Effects of radiation and temperature on gallium nitride (GaN) metal-semiconductor-metal ultraviolet photodetectors

NASA Astrophysics Data System (ADS)

Chiamori, Heather C.; Angadi, Chetan; Suria, Ateeq; Shankar, Ashwin; Hou, Minmin; Bhattacharya, Sharmila; Senesky, Debbie G.

2014-06-01

The development of radiation-hardened, temperature-tolerant materials, sensors and electronics will enable lightweight space sub-systems (reduced packaging requirements) with increased operation lifetimes in extreme harsh environments such as those encountered during space exploration. Gallium nitride (GaN) is a ceramic, semiconductor material stable within high-radiation, high-temperature and chemically corrosive environments due to its wide bandgap (3.4 eV). These material properties can be leveraged for ultraviolet (UV) wavelength photodetection. In this paper, current results of GaN metal-semiconductor-metal (MSM) UV photodetectors behavior after irradiation up to 50 krad and temperatures of 15°C to 150°C is presented. These initial results indicate that GaN-based sensors can provide robust operation within extreme harsh environments. Future directions for GaN-based photodetector technology for down-hole, automotive and space exploration applications are also discussed.

Catalytic decomposition of toxic chemicals over iron group metals supported on carbon nanotubes.

PubMed

Li, Lili; Chen, Can; Chen, Long; Zhu, Zixue; Hu, Jianli

2014-03-18

This study explores catalytic decomposition of phosphine (PH3) using iron group metals (Co, Ni) and metal oxides (Fe2O3, Co(3)O4, NiO) supported on carbon nanotubes (CNTs). The catalysts are synthesized by means of a deposition-precipitation method. The morphology, structure, and composition of the catalysts are characterized using a number of analytical instrumentations, including high-resolution transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, BET surface area measurement, and inductively coupled plasma. The activity of the catalysts in the PH3 decomposition reaction is measured and correlated with their surface and structural properties. The characterization results show that phosphidation occurs on the catalyst surface, and the resulting metal phosphides act as an active phase in the PH3 decomposition reaction. Cobalt phosphide, CoP, is formed on Co/CNTs and Co(3)O4/CNTs, whereas iron phosphide, FeP, is formed on Fe2O3/CNTs. In contrast, phosphorus-rich phosphide NiP2 is formed on Ni/CNTs and NiO/CNTs. The initial activities of the catalysts are shown in the following sequence: Ni/CNTs > Co/CNTs > Co(3)O4/CNTs >NiO/CNTs > Fe2O3/CNTs, whereas activities of metal phosphides are shown in the following order: CoP > NiP2 > FeP. The catalytic activity of metal phosphides is attributed to their electronic properties. Cobalt phosphide formed on Co/CNTs and Co(3)O4/CNTs exhibits not only the highest activity, but also long-term stability in the PH3 decomposition reaction.

Complete p-type activation in vertical-gradient freeze GaAs co-implanted with gallium and carbon

NASA Astrophysics Data System (ADS)

Horng, S. T.; Goorsky, M. S.

1996-03-01

High-resolution triple-axis x-ray diffractometry and Hall-effect measurements were used to characterize damage evolution and electrical activation in gallium arsenide co-implanted with gallium and carbon ions. Complete p-type activation of GaAs co-implanted with 5×1014 Ga cm-2 and 5×1014 C cm-2 was achieved after rapid thermal annealing at 1100 °C for 10 s. X-ray diffuse scattering was found to increase after rapid thermal annealing at 600-900 °C due to the aggregation of implantation-induced point defects. In this annealing range, there was ˜10%-72% activation. After annealing at higher annealing temperatures, the diffuse scattered intensity decreased drastically; samples that had been annealed at 1000 °C (80% activated) and 1100 °C (˜100% activated) exhibited reciprocal space maps that were indicative of high crystallinity. The hole mobility was about 60 cm2/V s for all samples annealed at 800 °C and above, indicating that the crystal perfection influences dopant activation more strongly than it influences mobility. Since the high-temperature annealing simultaneously increases dopant activation and reduces x-ray diffuse scattering, we conclude that point defect complexes which form at lower annealing temperatures are responsible for both the diffuse scatter and the reduced activation.

Diode laser-based thermometry using two-line atomic fluorescence of indium and gallium

NASA Astrophysics Data System (ADS)

Borggren, Jesper; Weng, Wubin; Hosseinnia, Ali; Bengtsson, Per-Erik; Aldén, Marcus; Li, Zhongshan

2017-12-01

A robust and relatively compact calibration-free thermometric technique using diode lasers two-line atomic fluorescence (TLAF) for reactive flows at atmospheric pressures is investigated. TLAF temperature measurements were conducted using indium and, for the first time, gallium atoms as temperature markers. The temperature was measured in a multi-jet burner running methane/air flames providing variable temperatures ranging from 1600 to 2000 K. Indium and gallium were found to provide a similar accuracy of 2.7% and precision of 1% over the measured temperature range. The reliability of the TLAF thermometry was further tested by performing simultaneous rotational CARS measurements in the same experiments.

Nonlinear behaviour of reflectivity of gallium - Silica interface & its applications

NASA Astrophysics Data System (ADS)

Naruka, Preeti; Bissa, Shivangi

2018-05-01

In this paper Optical properties and nonlinear behaviour of Gallium-Silica Interface is studied. Change in reflectivity of gallium film is explained as a function of thickness of metallic layer and intensity of incident light by using non-thermal mechanism. Here variation of dielectric constant of gallium with temperature is also explained on considering Binary nanoshell model of gallium nanoparticles of spherical shape. In the present paper application of structural phase transformation of gallium is explained as a Grating assisted coupler.

Sensitizing effects of gallium citrate on hyperthermic cell killing in vitro.

PubMed

Miyazaki, N; Nakano, H; Kawakami, N; Kugotani, M; Nishihara, K; Aoki, Y; Shinohara, K

2000-01-01

The lethal effects of gallium citrate in combination with heat were studied using four cell lines, L5178Y, FM3A, P388 and HeLa. Cells were incubated with different concentrations (0.2 2 mM) of gallium citrate at 37 degrees C for 24 h and heated at a range of temperatures from 40-44 degrees C for various time periods up to 6 h in the absence of gallium citrate. Survival and cell viability were determined by clonogenic assay and the dye-exclusion test, respectively. All of the cell lines tested were insensitive to heat below 41 degrees C, but were very sensitive to heat above 43 degrees C. Gallium citrate was cytotoxic to these cell lines at different levels: P388 and HeLa were far more sensitive than L5178Y and FM3A. The killing effects of heat at 41 degrees C were greatly enhanced by gallium citrate in L5178Y and P388 cells. The Arrhenius analysis for the lethal effect of heat, determined by clonogenic assay, in L5178Y cells showed that the transition temperature was remarkably decreased for the gallium-treated cells from approximately 43 degrees C to 41 degrees C. The mechanism for this decrease in the transition temperature may be attributable to the additional effects of gallium citrate on energy metabolism. Preincubation with 0.05 mM gallium citrate at 37 degrees C for 7 days also enhanced heat sensitization at 41 degrees C in L5178Y. This preincubation condition may correspond to the condition for the continuous infusion of gallium that is clinically used for cancer treatment. In contrast, treatment with gallium did not greatly enhance the sensitivity of FM3A or HeLa cells to heat at 41 degrees C, but the effects of gallium were significant.

Indium phosphide nanowires and their applications in optoelectronic devices

PubMed Central

Zafar, Fateen

2016-01-01

Group IIIA phosphide nanocrystalline semiconductors are of great interest among the important inorganic materials because of their large direct band gaps and fundamental physical properties. Their physical properties are exploited for various potential applications in high-speed digital circuits, microwave and optoelectronic devices. Compared to II–VI and I–VII semiconductors, the IIIA phosphides have a high degree of covalent bonding, a less ionic character and larger exciton diameters. In the present review, the work done on synthesis of III–V indium phosphide (InP) nanowires (NWs) using vapour- and solution-phase approaches has been discussed. Doping and core–shell structure formation of InP NWs and their sensitization using higher band gap semiconductor quantum dots is also reported. In the later section of this review, InP NW-polymer hybrid material is highlighted in view of its application as photodiodes. Lastly, a summary and several different perspectives on the use of InP NWs are discussed. PMID:27118920

Preventing Supercooling Of Gallium

NASA Technical Reports Server (NTRS)

Massucco, Arthur A.; Wenghoefer, Hans M.; Wilkins, Ronnie

1994-01-01

Principle of heterogeneous nucleation exploited to prevent gallium from supercooling, enabling its use as heat-storage material that crystallizes reproducibly at its freezing or melting temperature of 29 to 30 degrees C. In original intended application, gallium used as heat-storage material in gloves of space suits. Terrestrial application lies in preparation of freezing-temperature reference samples for laboratories. Principle of heterogeneous nucleation also exploited similarly in heat pipes filled with sodium.

Electro-optical characterization of GaAs solar cells

NASA Technical Reports Server (NTRS)

Olsen, Larry C.; Dunham, Glen; Addis, F. W.; Huber, Dan; Daling, Dave

1987-01-01

The electro-optical characterization of gallium arsenide p/n solar cells is discussed. The objective is to identify and understand basic mechanisms which limit the performance of high efficiency gallium arsenide solar cells. The approach involves conducting photoresponse and temperature dependent current-voltage measurements, and interpretation of the data in terms of theory to determine key device parameters. Depth concentration profiles are also utilized in formulating a model to explain device performance.

Gallium arsenide quantum well-based far infrared array radiometric imager

NASA Technical Reports Server (NTRS)

Forrest, Kathrine A.; Jhabvala, Murzy D.

1991-01-01

We have built an array-based camera (FIRARI) for thermal imaging (lambda = 8 to 12 microns). FIRARI uses a square format 128 by 128 element array of aluminum gallium arsenide quantum well detectors that are indium bump bonded to a high capacity silicon multiplexer. The quantum well detectors offer good responsivity along with high response and noise uniformity, resulting in excellent thermal images without compensation for variation in pixel response. A noise equivalent temperature difference of 0.02 K at a scene temperature of 290 K was achieved with the array operating at 60 K. FIRARI demonstrated that AlGaAS quantum well detector technology can provide large format arrays with performance superior to mercury cadmium telluride at far less cost.

Interaction potential for indium phosphide: a molecular dynamics and first-principles study of the elastic constants, generalized stacking fault and surface energies.

PubMed

Branicio, Paulo Sergio; Rino, José Pedro; Gan, Chee Kwan; Tsuzuki, Hélio

2009-03-04

Indium phosphide is investigated using molecular dynamics (MD) simulations and density-functional theory calculations. MD simulations use a proposed effective interaction potential for InP fitted to a selected experimental dataset of properties. The potential consists of two- and three-body terms that represent atomic-size effects, charge-charge, charge-dipole and dipole-dipole interactions as well as covalent bond bending and stretching. Predictions are made for the elastic constants as a function of density and temperature, the generalized stacking fault energy and the low-index surface energies.

Barringerite Fe2P from Pyrometamorphic Rocks of the Hatrurim Formation, Israel

NASA Astrophysics Data System (ADS)

Britvin, S. N.; Murashko, M. N.; Vapnik, E.; Polekhovsky, Yu. S.; Krivovichev, S. V.

2017-12-01

The article provides a detailed mineralogical and crystallochemical description (including refinement of the crystal structure) of the first finding of the phosphide class mineral barringerite, Fe2P, from terrestrial pyrometamorphic rocks of the Hatrurim Formation in Israel. The mineral occurs in the association of the so-called paralavas—initially silicate—carbonate sedimentary rocks that remelted during pyrometamorphic processes at a temperature above 1000°C and at a low pressure. Questions on the genesis and crystal chemistry of barringerite are discussed in connection with another polymorphic iron phosphide, allabogdanite (Fe,Ni)2P.

Pulsed Plasma Preparation for LWIR Materials

DTIC Science & Technology

1990-06-18

Reported Data: AlP is normally considered chemically unstable with respect to hydrolysis and formation of PH3 as a result of the exceptional stability of...A1203 (and consequently it is often used as a fumigant ). Its stability is thought to increase with purity. The thermal conductivity of crystalline...AlP is high (-1.3 Wcm’Kŕ at room temperature). Experimental Data: Initial films of aluminium phosphide, deposited from trimethylaluminium (TMA) and PH3

Ab-initio study of structural, electronic, and transport properties of zigzag GaP nanotubes.

PubMed

Srivastava, Anurag; Jain, Sumit Kumar; Khare, Purnima Swarup

2014-03-01

Stability and electronic properties of zigzag (3 ≤ n ≤ 16) gallium phosphide nanotubes (GaP NTs) have been analyzed by employing a systematic ab-intio approach based on density functional theory using generalized gradient approximation with revised Perdew Burke Ernzerhoff type parameterization. Diameter dependence of bond length, buckling, binding energy, and band gap has been investigated and the analysis shows that the bond length and buckling decreases with increasing diameter of the tube, highest binding energy of (16, 0) confirms this as the most stable amongst all the NTs taken into consideration. The present GaP NTs shows direct band gap and it increases with diameter of the tubes. Using a two probe model for (4, 0) NT the I-V relationship shows an exponential increase in current on applying bias voltage beyond 1.73 volt.

Multi-photon absorption limits to heralded single photon sources

PubMed Central

Husko, Chad A.; Clark, Alex S.; Collins, Matthew J.; De Rossi, Alfredo; Combrié, Sylvain; Lehoucq, Gaëlle; Rey, Isabella H.; Krauss, Thomas F.; Xiong, Chunle; Eggleton, Benjamin J.

2013-01-01

Single photons are of paramount importance to future quantum technologies, including quantum communication and computation. Nonlinear photonic devices using parametric processes offer a straightforward route to generating photons, however additional nonlinear processes may come into play and interfere with these sources. Here we analyse spontaneous four-wave mixing (SFWM) sources in the presence of multi-photon processes. We conduct experiments in silicon and gallium indium phosphide photonic crystal waveguides which display inherently different nonlinear absorption processes, namely two-photon (TPA) and three-photon absorption (ThPA), respectively. We develop a novel model capturing these diverse effects which is in excellent quantitative agreement with measurements of brightness, coincidence-to-accidental ratio (CAR) and second-order correlation function g(2)(0), showing that TPA imposes an intrinsic limit on heralded single photon sources. We build on these observations to devise a new metric, the quantum utility (QMU), enabling further optimisation of single photon sources. PMID:24186400

Gallium nitride optoelectronic devices

NASA Technical Reports Server (NTRS)

Chu, T. L.; Chu, S. S.

1972-01-01

The growth of bulk gallium nitride crystals was achieved by the ammonolysis of gallium monochloride. Gallium nitride single crystals up to 2.5 x 0.5 cm in size were produced. The crystals are suitable as substrates for the epitaxial growth of gallium nitride. The epitaxial growth of gallium nitride on sapphire substrates with main faces of (0001) and (1T02) orientations was achieved by the ammonolysis of gallium monochloride in a gas flow system. The grown layers had electron concentrations in the range of 1 to 3 x 10 to the 19th power/cu cm and Hall mobilities in the range of 50 to 100 sq cm/v/sec at room temperature.

Transition Metal Phosphide Nanoparticles Supported on SBA-15 as Highly Selective Hydrodeoxygenation Catalysts for the Production of Advanced Biofuels.

PubMed

Yang, Yongxing; Ochoa-Hernández, Cristina; de la Peña O'Shea, Víctor A; Pizarro, Patricia; Coronado, Juan M; Serrano, David P

2015-09-01

A series of catalysts constituted by nanoparticles of transition metal (M = Fe, Co, Ni and Mo) phosphides (TMP) dispersed on SBA-15 were synthesized by reduction of the corresponding metal phosphate precursors previously impregnated on the mesostructured support. All the samples contained a metal-loading of 20 wt% and with an initial M/P mole ratio of 1, and they were characterized by X-ray diffraction (XRD), N2 sorption, H2-TPR and transmission electron microscopy (TEM). Metal phosphide nanocatalysts were tested in a high pressure continuous flow reactor for the hydrodeoxygenation (HDO) of a methyl ester blend containing methyl oleate (C17H33-COO-CH3) as main component (70%). This mixture constitutes a convenient surrogate of triglycerides present in vegetable oils, and following catalytic hydrotreating yields mainly n-alkanes. The results of the catalytic assays indicate that Ni2P/SBA-15 catalyst presents the highest ester conversion, whereas the transformation rate is about 20% lower for MoP/SBA-15. In contrast, catalysts based on Fe and Co phosphides show a rather limited activity. Hydrocarbon distribution in the liquid product suggests that both hydrodeoxygenation and decarboxylation/decarbonylation reactions occur simultaneously over the different catalysts, although MoP/SBA-15 possess a selectivity towards hydrodeoxygenation exceeding 90%. Accordingly, the catalyst based on MoP affords the highest yield of n-octadecane, which is the preferred product in terms of carbon atom economy. Subsequently, in order to conjugate the advantages of both Ni and Mo phosphides, a series of catalysts containing variable proportions of both metals were prepared. The obtained results reveal that the mixed phosphides catalysts present a catalytic behavior intermediate between those of the monometallic phosphides. Accordingly, only marginal enhancement of the yield of n-octadecane is obtained for the catalysts with a Mo/Ni ratio of 3. Nevertheless, owing to this high selectivity for hydrodeoxygenation MoP/SBA-15 appears as a very promising catalyst for the production of advanced biofuels.

Hot and solid gallium clusters: too small to melt.

PubMed

Breaux, Gary A; Benirschke, Robert C; Sugai, Toshiki; Kinnear, Brian S; Jarrold, Martin F

2003-11-21

A novel multicollision induced dissociation scheme is employed to determine the energy content for mass-selected gallium cluster ions as a function of their temperature. Measurements were performed for Ga(+)(n) (n=17 39, and 40) over a 90-720 K temperature range. For Ga+39 and Ga+40 a broad maximum in the heat capacity-a signature of a melting transition for a small cluster-occurs at around 550 K. Thus small gallium clusters melt at substantially above the 302.9 K melting point of bulk gallium, in conflict with expectations that they will remain liquid to below 150 K. No melting transition is observed for Ga+17.

Congruent melting of gallium nitride at 6 GPa and its application to single-crystal growth.

PubMed

Utsumi, Wataru; Saitoh, Hiroyuki; Kaneko, Hiroshi; Watanuki, Tetsu; Aoki, Katsutoshi; Shimomura, Osamu

2003-11-01

The synthesis of large single crystals of GaN (gallium nitride) is a matter of great importance in optoelectronic devices for blue-light-emitting diodes and lasers. Although high-quality bulk single crystals of GaN suitable for substrates are desired, the standard method of cooling its stoichiometric melt has been unsuccessful for GaN because it decomposes into Ga and N(2) at high temperatures before its melting point. Here we report that applying high pressure completely prevents the decomposition and allows the stoichiometric melting of GaN. At pressures above 6.0 GPa, congruent melting of GaN occurred at about 2,220 degrees C, and decreasing the temperature allowed the GaN melt to crystallize to the original structure, which was confirmed by in situ X-ray diffraction. Single crystals of GaN were formed by cooling the melt slowly under high pressures and were recovered at ambient conditions.

The gallium melting-point standard: its application and evaluation for temperature measurements in the clinical laboratory.

PubMed

Bowers, G N; Inman, S R

1977-01-01

We are impressed with the ease and certainty of calibration electronic thermometers with thermistor probes to +/- 0.01 degree C at the gallium melting point, 29.771(4) degrees C. The IFCC reference method for measuring aspartate aminotransferase activity in serum was run at the reaction temperature of 29.771(4) degrees C. By constantly referencing to gallium as an integral part of the assay procedure, we determined the absolute reaction temperature to IPTS-68 (International Practical Temperature Scale of 1968) to +/- 0.02 degrees C. This unique temperature calibration standard near the center of the range of temperatures commonly used in the clinical laboratory is a valuable addition and can be expected to improve the accuracy of measurements, especially in clinical enzymology.

Off-axis holographic lens spectrum-splitting photovoltaic system for direct and diffuse solar energy conversion.

PubMed

Vorndran, Shelby D; Chrysler, Benjamin; Wheelwright, Brian; Angel, Roger; Holman, Zachary; Kostuk, Raymond

2016-09-20

This paper describes a high-efficiency, spectrum-splitting photovoltaic module that uses an off-axis volume holographic lens to focus and disperse incident solar illumination to a rectangular shaped high-bandgap indium gallium phosphide cell surrounded by strips of silicon cells. The holographic lens design allows efficient collection of both direct and diffuse illumination to maximize energy yield. We modeled the volume diffraction characteristics using rigorous coupled-wave analysis, and simulated system performance using nonsequential ray tracing and PV cell data from the literature. Under AM 1.5 illumination conditions the simulated module obtained a 30.6% conversion efficiency. This efficiency is a 19.7% relative improvement compared to the more efficient cell in the system (silicon). The module was also simulated under a typical meteorological year of direct and diffuse irradiance in Tucson, Arizona, and Seattle, Washington. Compared to a flat panel silicon module, the holographic spectrum splitting module obtained a relative improvement in energy yield of 17.1% in Tucson and 14.0% in Seattle. An experimental proof-of-concept volume holographic lens was also fabricated in dichromated gelatin to verify the main characteristics of the system. The lens obtained an average first-order diffraction efficiency of 85.4% across the aperture at 532 nm.

P-n junctions formed in gallium antimonide

NASA Technical Reports Server (NTRS)

Clough, R.; Richman, D.; Tietjen, J.

1970-01-01

Vapor phase deposition process forms a heavily doped n-region on a melt-grown p-type gallium antimonide substrate. HCl transports gallium to the reaction zone, where it combines with antimony hydride and the dopant carrier, hydrogen telluride. Temperatures as low as 400 degrees C are required.

Simple, mild, one-step labelling of proteins with gallium-68 using a tris(hydroxypyridinone) bifunctional chelator: a 68Ga-THP-scFv targeting the prostate-specific membrane antigen.

PubMed

Nawaz, Saima; Mullen, Gregory E D; Sunassee, Kavitha; Bordoloi, Jayanta; Blower, Philip J; Ballinger, James R

2017-10-25

Labelling proteins with gallium-68 using bifunctional chelators is often problematic because of unsuitably harsh labelling conditions such as low pH or high temperature and may entail post-labelling purification. To determine whether tris(hydroxypyridinone) (THP) bifunctional chelators offer a potential solution to this problem, we have evaluated the labelling and biodistribution of a THP conjugate with a new single-chain antibody against the prostate-specific membrane antigen (PSMA), an attractive target for staging prostate cancer (PCa). A single-chain variable fragment (scFv) of J591, a monoclonal antibody that recognises an external epitope of PSMA, was prepared in order to achieve biokinetics matched to the half-life of gallium-68. The scFv, J591c-scFv, was engineered with a C-terminal cysteine. J591c-scFv was produced in HEK293T cells and purified by size-exclusion chromatography. A maleimide THP derivative (THP-mal) was coupled site-specifically to the C-terminal cysteine residue. The THP-mal-J591c-scFv conjugate was labelled with ammonium acetate-buffered gallium-68 from a 68 Ge/ 68 Ga generator at room temperature and neutral pH. The labelled conjugate was evaluated in the PCa cell line DU145 and its PSMA-overexpressing variant in vitro and xenografted in SCID mice. J591c-scFv was produced in yields of 4-6 mg/l culture supernatant and efficiently coupled with the THP-mal bifunctional chelator. Labelling yields > 95% were achieved at room temperature following incubation of 5 μg conjugate with gallium-68 for 5 min without post-labelling purification. 68 Ga-THP-mal-J591c-scFv was stable in serum and showed selective binding to the DU145-PSMA cell line, allowing an IC50 value of 31.5 nM to be determined for unmodified J591c-scFv. Serial PET/CT imaging showed rapid, specific tumour uptake and clearance via renal elimination. Accumulation in DU145-PSMA xenografts at 90 min post-injection was 5.4 ± 0.5%ID/g compared with 0.5 ± 0.2%ID/g in DU145 tumours (n = 4). The bifunctional chelator THP-mal enabled simple, rapid, quantitative, one-step room temperature radiolabelling of a protein with gallium-68 at neutral pH without a need for post-labelling purification. The resultant gallium-68 complex shows high affinity for PSMA and favourable in vivo targeting properties in a xenograft model of PCa.

A Two-Dimensional Manganese Gallium Nitride Surface Structure Showing Ferromagnetism at Room Temperature.

PubMed

Ma, Yingqiao; Chinchore, Abhijit V; Smith, Arthur R; Barral, María Andrea; Ferrari, Valeria

2018-01-10

Practical applications of semiconductor spintronic devices necessitate ferromagnetic behavior at or above room temperature. In this paper, we demonstrate a two-dimensional manganese gallium nitride surface structure (MnGaN-2D) which is atomically thin and shows ferromagnetic domain structure at room temperature as measured by spin-resolved scanning tunneling microscopy and spectroscopy. Application of small magnetic fields proves that the observed magnetic domains follow a hysteretic behavior. Two initially oppositely oriented MnGaN-2D domains are rotated into alignment with only 120 mT and remain mostly in alignment at remanence. The measurements are further supported by first-principles theoretical calculations which reveal highly spin-polarized and spin-split surface states with spin polarization of up to 95% for manganese local density of states.

Giant topological nontrivial band gaps in chloridized gallium bismuthide.

PubMed

Li, Linyang; Zhang, Xiaoming; Chen, Xin; Zhao, Mingwen

2015-02-11

Quantum spin Hall (QSH) effect is promising for achieving dissipationless transport devices but presently is achieved only at extremely low temperature. Searching for the large-gap QSH insulators with strong spin-orbit coupling (SOC) is the key to increase the operating temperature. We demonstrate theoretically that this can be solved in the chloridized gallium bismuthide (GaBiCl2) monolayer, which has nontrivial gaps of 0.95 eV at the Γ point, and 0.65 eV for bulk, as well as gapless edge states in the nanoribbon structures. The nontrivial gaps due to the band inversion and SOC are robust against external strain. The realization of the GaBiCl2 monolayer will be beneficial for achieving QSH effect and related applications at high temperatures.

Contributions from gallium vacancies and carbon-related defects to the ``yellow luminescence'' in GaN

NASA Astrophysics Data System (ADS)

Armitage, R.; Hong, William; Yang, Qing; Feick, H.; Gebauer, J.; Weber, E. R.; Hautakangas, S.; Saarinen, K.

2003-05-01

Carbon-doped GaN layers grown by molecular-beam epitaxy are studied with photoluminescence and positron annihilation spectroscopy. Semi-insulating layers doped with >1018 cm-3 carbon show a strong luminescence band centered at ˜2.2 eV (yellow luminescence). The absolute intensity of the 2.2 eV band is compared with the gallium vacancy concentration determined by positron annihilation spectroscopy. The results indicate that a high concentration of gallium vacancies is not necessary for yellow luminescence and that there is in fact a causal relationship between carbon and the 2.2 eV band. Markedly different deep-level ionization energies are found for the high-temperature quenching of the 2.2 eV photoluminescence in carbon-doped and reference samples. We propose that while the model of Neugebauer and Van de Walle [Appl. Phys. Lett. 69, 503 (1996)] applies for GaN of low carbon concentration, a different yellow luminescence mechanism is involved when the interstitial carbon concentration is comparable to or exceeds the gallium vacancy concentration.

T-shaped emitter metal heterojunction bipolar transistors for submillimeter wave applications

NASA Technical Reports Server (NTRS)

Fung, Andy; Samoska, Lorene; Velebir, Jim; Siege, Peter; Rodwell, Mark; Paidi, Vamsi; Griffth, Zach; Urteaga, Miguel; Malik, Roger

2004-01-01

We report on the development of submillimeter wave transistors at JPL. The goal of the effort is to produce advance-reliable high frequency and high power amplifiers, voltage controlled oscillators, active multipliers, and high-speed mixed-signal circuits for space borne applications. The technology in development to achieve this is based on the Indium Phosphide (InP) Heterojunction Bipolar Transistor (HBT). The HBT is well suited for high speed, high power and uniform (across wafer) performance, due to the ability to tailor the material structure that electrons traverse through by well-controlled epitaxial growth methods. InP with its compatible lattice matched alloys such as indium gallium arsenide (InGaAs) and indium aluminium arsenide (InAlAs) provides for high electron velocities and high voltage breakdown capabilities. The epitaxial methods for this material system are fairly mature, however the implementation of high performance and reliable transistors are still under development by many laboratories. Our most recently fabricated, second generation mesa HBTs at JPL have extrapolated current gain cutoff frequency (FJ of 142GHz and power gain cutoff frequency (Fm,) of approximately 160GHz. This represents a 13% and 33% improvement of Ft and F, respectively, compared to the first generation mesa HBTs [l]. Analysis based on the University of California, Santa Barbara (UCSB) device model, RF device characteristics can be significantly improved by reducing base contact resistance and base metal contact width. We will describe our effort towards increasing transistor performance and yield.

Accurate calibration for the quantification of the Al content in AlGaN epitaxial layers by energy-dispersive X-ray spectroscopy in a Transmission Electron Microscope

NASA Astrophysics Data System (ADS)

Amari, H.; Lari, L.; Zhang, H. Y.; Geelhaar, L.; Chèze, C.; Kappers, M. J.; McAleese, C.; Humphreys, C. J.; Walther, T.

2011-11-01

Since the band structure of group III- nitrides presents a direct electronic transition with a band-gap energy covering the range from 3.4 eV for (GaN) to 6.2 eV (for AlN) at room temperature as well as a high thermal conductivity, aluminium gallium nitride (AlGaN) is a strong candidate for high-power and high-temperature electronic devices and short-wavelength (visible and ultraviolet) optoelectronic devices. We report here a study by energy-filtered transmission electron microscopy (EFTEM) and energy-dispersive X-ray spectroscopy (EDXS) of the micro structure and elemental distribution in different aluminium gallium nitride epitaxial layers grown by different research groups. A calibration procedure is out-lined that yields the Al content from EDXS to within ~1 at % precision.

Ultrasonic cavitation of molten gallium: formation of micro- and nano-spheres.

PubMed

Kumar, Vijay Bhooshan; Gedanken, Aharon; Kimmel, Giora; Porat, Ze'ev

2014-05-01

Pure gallium has a low melting point (29.8°C) and can be melted in warm water or organic liquids, thus forming two immiscible liquid phases. Irradiation of this system with ultrasonic energy causes cavitation and dispersion of the molten gallium as microscopic spheres. The resultant spheres were found to have radii range of 0.2-5 μm and they do not coalesce upon cessation of irradiation, although the ambient temperature is well above the m.p. of gallium. It was found that the spheres formed in water are covered with crystallites of GaO(OH), whereas those formed in organic liquids (hexane and n-dodecane) are smooth, lacking such crystallites. However, Raman spectroscopy revealed that the spheres formed in organic liquids are coated with a carbon film. The latter may be the factor preventing their coalescence at temperatures above the m.p. of gallium. Copyright © 2013 Elsevier B.V. All rights reserved.

Characterization of solar cells for space applications. Volume 13: Electrical characteristics of Hughes LPE gallium arsenide solar cells as a function of intensity and temperature

NASA Technical Reports Server (NTRS)

Anspaugh, B. E.; Beckert, D. M.; Downing, R. G.; Miyahira, T. F.; Weiss, R. S.

1980-01-01

Electrical characteristics of Hughes Liquid phase epitaxy, P/N gallium aluminum arsenide solar cells are presented in graphical and tabular format as a function of solar illumination intensity and temperature.

Optoelectronic and low temperature thermoelectric studies on nanostructured thin films of silver gallium selenide

NASA Astrophysics Data System (ADS)

Jacob, Rajani; Philip, Rachel Reena; Nazer, Sheeba; Abraham, Anitha; Nair, Sinitha B.; Pradeep, B.; Urmila, K. S.; Okram, G. S.

2014-01-01

Polycrystalline thin films of silver gallium selenide were deposited on ultrasonically cleaned soda lime glass substrates by multi-source vacuum co-evaporation technique. The structural analysis done by X-ray diffraction ascertained the formation of nano structured tetragonal chalcopyrite thin films. The compound formation was confirmed by X-ray photo-electron spectroscopy. Atomic force microscopic technique has been used for surface morphological analysis. Direct allowed band gap ˜1.78eV with high absorption coefficient ˜106/m was estimated from absorbance spectra. Low temperature thermoelectric effects has been investigated in the temperature range 80-330K which manifested an unusual increase in Seebeck coefficient with negligible phonon drag toward the very low and room temperature regime. The electrical resistivity of these n-type films was assessed to be ˜2.6Ωm and the films showed good photo response.

Thermodynamic properties of uranium in liquid gallium, indium and their alloys

NASA Astrophysics Data System (ADS)

Volkovich, V. A.; Maltsev, D. S.; Yamshchikov, L. F.; Osipenko, A. G.

2015-09-01

Activity, activity coefficients and solubility of uranium was determined in gallium, indium and gallium-indium alloys containing 21.8 (eutectic), 40 and 70 wt.% In. Activity was measured at 573-1073 K employing the electromotive force method, and solubility between room temperature (or the alloy melting point) and 1073 K employing direct physical measurements. Activity coefficients were obtained from the difference of experimentally determined temperature dependencies of uranium activity and solubility. Intermetallic compounds formed in the respective alloys were characterized using X-ray diffraction. Partial and excess thermodynamic functions of uranium in the studied alloys were calculated. Liquidus lines in U-Ga and U-In phase diagrams from the side rich in gallium or indium are proposed.

Method for production of free-standing polycrystalline boron phosphide film

DOEpatents

Baughman, Richard J.; Ginley, David S.

1985-01-01

A process for producing a free-standing polycrystalline boron phosphide film comprises growing a film of boron phosphide in a vertical growth apparatus on a metal substrate. The metal substrate has a coefficient of thermal expansion sufficiently different from that of boron phosphide that the film separates cleanly from the substrate upon cooling thereof, and the substrate is preferably titanium. The invention also comprises a free-standing polycrystalline boron phosphide film for use in electronic device fabrication.

Ab-initio calculations of electronic, transport, and structural properties of boron phosphide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ejembi, J. I.; Nwigboji, I. H.; Franklin, L.

2014-09-14

We present results from ab-initio, self-consistent density functional theory calculations of electronic and related properties of zinc blende boron phosphide (zb-BP). We employed a local density approximation potential and implemented the linear combination of atomic orbitals formalism. This technique follows the Bagayoko, Zhao, and Williams method, as enhanced by the work of Ekuma and Franklin. The results include electronic energy bands, densities of states, and effective masses. The calculated band gap of 2.02 eV, for the room temperature lattice constant of a=4.5383 Å, is in excellent agreement with the experimental value of 2.02±0.05 eV. Our result for the bulk modulus,more » 155.7 GPa, agrees with experiment (152–155 GPa). Our predictions for the equilibrium lattice constant and the corresponding band gap, for very low temperatures, are 4.5269 Å and 2.01 eV, respectively.« less

Improved heat dissipation in gallium nitride light-emitting diodes with embedded graphene oxide pattern.

PubMed

Han, Nam; Cuong, Tran Viet; Han, Min; Ryu, Beo Deul; Chandramohan, S; Park, Jong Bae; Kang, Ji Hye; Park, Young-Jae; Ko, Kang Bok; Kim, Hee Yun; Kim, Hyun Kyu; Ryu, Jae Hyoung; Katharria, Y S; Choi, Chel-Jong; Hong, Chang-Hee

2013-01-01

The future of solid-state lighting relies on how the performance parameters will be improved further for developing high-brightness light-emitting diodes. Eventually, heat removal is becoming a crucial issue because the requirement of high brightness necessitates high-operating current densities that would trigger more joule heating. Here we demonstrate that the embedded graphene oxide in a gallium nitride light-emitting diode alleviates the self-heating issues by virtue of its heat-spreading ability and reducing the thermal boundary resistance. The fabrication process involves the generation of scalable graphene oxide microscale patterns on a sapphire substrate, followed by its thermal reduction and epitaxial lateral overgrowth of gallium nitride in a metal-organic chemical vapour deposition system under one-step process. The device with embedded graphene oxide outperforms its conventional counterpart by emitting bright light with relatively low-junction temperature and thermal resistance. This facile strategy may enable integration of large-scale graphene into practical devices for effective heat removal.

40 CFR 180.284 - Zinc phosphide; tolerances for residues.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 24 2011-07-01 2011-07-01 false Zinc phosphide; tolerances for... § 180.284 Zinc phosphide; tolerances for residues. (a) General. Tolerances are established for residues of the phosphine resulting from the use of the rodenticide zinc phosphide in or on the raw...

Photovoltaic cells employing zinc phosphide

DOEpatents

Barnett, Allen M.; Catalano, Anthony W.; Dalal, Vikram L.; Masi, James V.; Meakin, John D.; Hall, Robert B.

1984-01-01

A photovoltaic cell having a zinc phosphide absorber. The zinc phosphide can be a single or multiple crystal slice or a thin polycrystalline film. The cell can be a Schottky barrier, heterojunction or homojunction device. Methods for synthesizing and crystallizing zinc phosphide are disclosed as well as a method for forming thin films.

Free-standing polycrystalline boron phosphide film and method for production thereof

DOEpatents

Baughman, R.J.; Ginley, D.S.

1982-09-09

A process for producing a free-standing polycrystalline boron phosphide film comprises growing a film of boron phosphide in a vertical growth apparatus on a metal substrate. The metal substrate has a coefficient of thermal expansion sufficiently different from that of boron phosphide that the film separates cleanly from the substrate upon cooling thereof, and the substrate is preferably titanium. The invention also comprises a free-standing polycrystalline boron phosphide film for use in electronic device fabrication.

Orientation of Zn3P2 films via phosphidation of Zn precursors

NASA Astrophysics Data System (ADS)

Katsube, Ryoji; Nose, Yoshitaro

2017-02-01

Orientation of solar absorber is an important factor to achieve high efficiency of thin film solar cells. In the case of Zn3P2 which is a promising absorber of low-cost and high-efficiency solar cells, (110)/(001) orientation was only reported in previous studies. We have successfully prepared (101)-oriented Zn3P2 films by phosphidation of (0001)-oriented Zn films at 350 °C. The phosphidation mechanism of Zn is discussed through STEM observations on the partially-reacted sample and the consideration of the relationship between the crystal structures of Zn and Zn3P2 . We revealed that (0001)-oriented Zn led to nucleation of (101)-oriented Zn3P2 due to the similarity in atomic arrangement between Zn and Zn3P2 . The electrical resistivity of the (101)-oriented Zn3P2 film was lower than those of (110)/(001)-oriented films, which is an advantage of the phosphidation technique to the growth processes in previous works. The results in this study demonstrated that well-conductive Zn3P2 films could be obtained by controlling orientations of crystal grains, and provide a guiding principle for microstructure control in absorber materials.

High Stability Performance of Quinary Indium Gallium Zinc Aluminum Oxide Films and Thin-Film Transistors Deposited Using Vapor Cooling Condensation Method

NASA Astrophysics Data System (ADS)

Lin, Yung-Hao; Lee, Ching-Ting

2017-08-01

High-quality indium gallium zinc aluminum oxide (IGZAO) thin films with various Al contents have been deposited using the vapor cooling condensation method. The electron mobility of the IGZAO films was improved by 89.4% on adding Al cation to IGZO film. The change in the electron concentration and mobility of the IGZAO films was 7.3% and 7.0%, respectively, when the temperature was changed from 300 K to 225 K. These experimental results confirm the high performance and stability of the IGZAO films. The performance stability mechanisms of IGZAO thin-film transistors (TFTs) were investigated in comparison with IGZO TFTs.

Gallium assisted plasma enhanced chemical vapor deposition of silicon nanowires.

PubMed

Zardo, I; Yu, L; Conesa-Boj, S; Estradé, S; Alet, Pierre Jean; Rössler, J; Frimmer, M; Roca I Cabarrocas, P; Peiró, F; Arbiol, J; Morante, J R; Fontcuberta I Morral, A

2009-04-15

Silicon nanowires have been grown with gallium as catalyst by plasma enhanced chemical vapor deposition. The morphology and crystalline structure has been studied by electron microscopy and Raman spectroscopy as a function of growth temperature and catalyst thickness. We observe that the crystalline quality of the wires increases with the temperature at which they have been synthesized. The crystalline growth direction has been found to vary between <111> and <112>, depending on both the growth temperature and catalyst thickness. Gallium has been found at the end of the nanowires, as expected from the vapor-liquid-solid growth mechanism. These results represent good progress towards finding alternative catalysts to gold for the synthesis of nanowires.

3-D printing of liquid metals for stretchable and flexible conductors

NASA Astrophysics Data System (ADS)

Trlica, Chris; Parekh, Dishit Paresh; Panich, Lazar; Ladd, Collin; Dickey, Michael D.

2014-06-01

3-D printing is an emerging technology that has been used primarily on small scales for rapid prototyping, but which could also herald a wider movement towards decentralized, highly customizable manufacturing. Polymers are the most common materials to be 3-D printed today, but there is great demand for a way to easily print metals. Existing techniques for 3-D printing metals tend to be expensive and energy-intensive, and usually require high temperatures or pressures, making them incompatible with polymers, organics, soft materials, and biological materials. Here, we describe room temperature liquid metals as complements to polymers for 3-D printing applications. These metals enable the fabrication of soft, flexible, and stretchable devices. We survey potential room temperature liquid metal candidates and describe the benefits of gallium and its alloys for these purposes. We demonstrate the direct printing of a liquid gallium alloy in both 2-D and 3-D and highlight the structures and shapes that can be fabricated using these processes.

Effect of dislocations on the open-circuit voltage, short-circuit current and efficiency of heteroepitaxial indium phosphide solar cells

NASA Technical Reports Server (NTRS)

Jain, Raj K.; Flood, Dennis J.

1990-01-01

Excellent radiation resistance of indium phosphide solar cells makes them a promising candidate for space power applications, but the present high cost of starting substrates may inhibit their large scale use. Thin film indium phosphide cells grown on Si or GaAs substrates have exhibited low efficiencies, because of the generation and propagation of large number of dislocations. Dislocation densities were calculated and its influence on the open circuit voltage, short circuit current, and efficiency of heteroepitaxial indium phosphide cells was studied using the PC-1D. Dislocations act as predominant recombination centers and are required to be controlled by proper transition layers and improved growth techniques. It is shown that heteroepitaxial grown cells could achieve efficiencies in excess of 18 percent AMO by controlling the number of dislocations. The effect of emitter thickness and surface recombination velocity on the cell performance parameters vs. dislocation density is also studied.

Effects of Polyethylene Glycol and Citric Acid on Preparation and Hydrodechlorination Activity of Molybdenum Phosphide

NASA Astrophysics Data System (ADS)

Liu, Xiaomeng; Lu, Shaoxiang; Xu, Hanghui; Ren, Lili

2018-07-01

Molybdenum phosphide (MoP), modified by polyethylene glycol (PEG) and citric acid (CA), exhibited 2 to 3 times superior activity than the MoP modified by CA alone. And the optimal activity temperature was reduced from 500 to 450oC. The catalyst was fully characterized by a variety of techniques including X-ray diffraction (XRD), N2 adsorption-desorption isotherm, scanning electron microscopy (SEM), transmission electron microscopy (TEM). The results showed that the addition of PEG and CA increased the surface area of MoP and decreased the particle size of MoP. Furthermore, the reaction mechanism also has been discussed by combining the activity data and characterization results.

Self-catalyzed GaAs nanowires on silicon by hydride vapor phase epitaxy.

PubMed

Dong, Zhenning; André, Yamina; Dubrovskii, Vladimir G; Bougerol, Catherine; Leroux, Christine; Ramdani, Mohammed R; Monier, Guillaume; Trassoudaine, Agnès; Castelluci, Dominique; Gil, Evelyne

2017-03-24

Gold-free GaAs nanowires on silicon substrates can pave the way for monolithic integration of photonic nanodevices with silicon electronic platforms. It is extensively documented that the self-catalyzed approach works well in molecular beam epitaxy but is much more difficult to implement in vapor phase epitaxies. Here, we report the first gallium-catalyzed hydride vapor phase epitaxy growth of long (more than 10 μm) GaAs nanowires on Si(111) substrates with a high integrated growth rate up to 60 μm h -1 and pure zincblende crystal structure. The growth is achieved by combining a low temperature of 600 °C with high gaseous GaCl/As flow ratios to enable dechlorination and formation of gallium droplets. GaAs nanowires exhibit an interesting bottle-like shape with strongly tapered bases, followed by straight tops with radii as small as 5 nm. We present a model that explains the peculiar growth mechanism in which the gallium droplets nucleate and rapidly swell on the silicon surface but then are gradually consumed to reach a stationary size. Our results unravel the necessary conditions for obtaining gallium-catalyzed GaAs nanowires by vapor phase epitaxy techniques.

[Determination of trace gallium by graphite furnace atomic absorption spectrometry in urine].

PubMed

Zhou, L Z; Fu, S; Gao, S Q; He, G W

2016-06-20

To establish a method for determination trace gallium in urine by graphite furnace atomic absorption spectrometry (GFAAS). The ammonium dihydrogen phosphate was matrix modifier. The temperature effect about pyrolysis (Tpyr) and atomization temperature were optimized for determination of trace gallium. The method of technical standard about within-run, between-run and recoveries of standard were optimized. The method showed a linear relationship within the range of 0.20~80.00 μg/L (r=0.998). The within-run and between-run relative standard deviations (RSD) of repetitive measurement at 5.0, 10.0, 20.0 μg/L concentration levels were 2.1%~5.5% and 2.3%~3.0%. The detection limit was 0.06 μg/L. The recoveries of gallium were 98.2%~101.1%. This method is simple, low detection limit, accurate, reliable and reproducible. It has been applied for determination of trace gallium in urine samples those who need occupation health examination or poisoning diagnosis.

Group III-nitride thin films grown using MBE and bismuth

DOEpatents

Kisielowski, Christian K.; Rubin, Michael

2002-01-01

The present invention comprises growing gallium nitride films in the presence of bismuth using MBE at temperatures of about 1000 K or less. The present invention further comprises the gallium nitride films fabricated using the inventive fabrication method. The inventive films may be doped with magnesium or other dopants. The gallium nitride films were grown on sapphire substrates using a hollow anode Constricted Glow Discharge nitrogen plasma source. When bismuth was used as a surfactant, two-dimensional gallium nitride crystal sizes ranging between 10 .mu.m and 20 .mu.m were observed. This is 20 to 40 times larger than crystal sizes observed when GaN films were grown under similar circumstances but without bismuth. It is thought that the observed increase in crystal size is due bismuth inducing an increased surface diffusion coefficient for gallium. The calculated value of 4.7.times.10.sup.-7 cm.sup.2 /sec. reveals a virtual substrate temperature of 1258 K which is 260 degrees higher than the actual one.

Group III-nitride thin films grown using MBE and bismuth

DOEpatents

Kisielowski, Christian K.; Rubin, Michael

2000-01-01

The present invention comprises growing gallium nitride films in the presence of bismuth using MBE at temperatures of about 1000 K or less. The present invention further comprises the gallium nitride films fabricated using the inventive fabrication method. The inventive films may be doped with magnesium or other dopants. The gallium nitride films were grown on sapphire substrates using a hollow anode Constricted Glow Discharge nitrogen plasma source. When bismuth was used as a surfactant, two-dimensional gallium nitride crystal sizes ranging between 10 .mu.m and 20 .mu.m were observed. This is 20 to 40 times larger than crystal sizes observed when GaN films were grown under similar circumstances but without bismuth. It is thought that the observed increase in crystal size is due bismuth inducing an increased surface diffusion coefficient for gallium. The calculated value of 4.7.times.10.sup.-7 cm.sup.2 /sec. reveals a virtual substrate temperature of 1258 K which is 260 degrees higher than the actual one.

Influence of neodymium concentration on excitation and emission properties of Nd doped gallium oxide nanocrystalline films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Podhorodecki, A.; Banski, M.; Misiewicz, J.

Gallium oxide and more particularly {beta}-Ga{sub 2}O{sub 3} matrix is an excellent material for new generation of devices electrically or optically driven as it is known as the widest band gap transparent conductive oxide. In this paper, the optical properties of neodymium doped gallium oxide films grown by magnetron sputtering have been analyzed. The influence of the Nd ions concentration on the excitation/emission mechanisms of Nd ions and the role of gallium oxide matrix have been investigated. The grain size reduction into gallium oxide films have been observed when concentration of Nd increases. It has been found for all samplesmore » that the charge transfer is the main excitation mechanism for Nd ions where defect states play an important role as intermediate states. As a consequence Nd emission efficiency increases with temperature giving rise to most intensive emission at 1087 nm at room temperature.« less

Liquid gallium and the eutectic gallium indium (EGaIn) alloy: Dielectric functions from 1.24 to 3.1 eV by electrochemical reduction of surface oxides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morales, Daniel; Yu, Zhiyuan; Dickey, Michael D., E-mail: mddickey@ncsu.edu, E-mail: aspnes@ncsu.edu

Liquid metals based on gallium are promising materials for soft, stretchable, and shape reconfigurable electromagnetic devices. The behavior of these metals relates directly to the thicknesses of their surface oxide layers, which can be determined nondestructively by ellipsometry if their dielectric functions ε are known. This paper reports on the dielectric functions of liquid gallium and the eutectic gallium indium (EGaIn) alloy from 1.24 to 3.1 eV at room temperature, measured by spectroscopic ellipsometry. Overlayer-induced artifacts, a continuing problem in optical measurements of these highly reactive metals, are eliminated by applying an electrochemically reductive potential to the surface of the metalmore » immersed in an electrolyte. This technique enables measurements at ambient conditions while avoiding the complications associated with removing overlayers in a vacuum environment. The dielectric responses of both metals are closely represented by the Drude model. The EGaIn data suggest that in the absence of an oxide the surface is In-enriched, consistent with the previous vacuum-based studies. Possible reasons for discrepancies with previous measurements are discussed.« less

Gallium hydride complexes stabilised by multidentate alkoxide ligands: precursors to thin films of Ga2O3 at low temperatures.

PubMed

Pugh, David; Bloor, Leanne G; Parkin, Ivan P; Carmalt, Claire J

2012-05-07

The donor-functionalised alkoxides {Me(3-x)N(CH(2)CH(2)O)(x)} (L(x); x = 1, 2) have been used to form gallium hydride complexes [{GaH(2)(L(1))}(2)] and [{GaH(L(2))}(2)] that are stable and isolable at room temperature. Along with a heteroleptic gallium tris(alkoxide) complex [Ga(L(1))(3)] and the dimeric complex [{GaMe(L(2))}(2)], these compounds have been used as single-source precursors for the deposition of Ga(2)O(3) by aerosol-assisted chemical vapour deposition (AACVD) with toluene as solvent. The resulting films were mostly transparent, indicating low levels of carbon contamination, and they were also mainly amorphous. However, [Ga(L(1))(3)] did contain visibly crystalline material deposited at a substrate temperature of 450 °C, by far the lowest ever observed for the CVD of gallium oxide. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fabrication of magnetic nano liquid metal fluid through loading of Ni nanoparticles into gallium or its alloy

NASA Astrophysics Data System (ADS)

Xiong, Mingfeng; Gao, Yunxia; Liu, Jing

2014-03-01

In this study, Ni nanoparticles were loaded into the partially oxidized gallium and its alloys to fabricate desired magnetic nanofluid. It was disclosed that the Ni nanoparticles sharply increased the freezing temperature and latent heat of the obtained magnetic nano liquid metal fluid, while the melting process was less affected. For the gallium sample added with 10 vol% coated Ni particles, a hysteresis loop was observed and the magnetization intensity decreased with the increase of the temperature. The slope for the magnetization-temperature curve within 10-30 K was about 20 times of that from 40 K to 400 K. Further, the dynamic impact experiments of striking magnetic liquid metal droplets on the magnet revealed that the regurgitating of the leading edge of the liquid disk and the subsequent wave that often occurred in the gallium-indium droplets would disappear for the magnetic fluids case due to attraction force of the magnet.

Low Temperature Flux Growth of 2H-SiC and Beta-Gallium Oxide

NASA Technical Reports Server (NTRS)

Singh, N. B.; Choa, Fow-Sen; Su, Ching-Hua; Arnold, Bradley; Kelly, Lisa

2016-01-01

We present brief overview of our study on the low temperature flux growth of two very important novel wide bandgap materials 2H-SiC and Beta-gallium oxide (Beta-Ga2O3). We have synthesized and grown 5 millimeter to 1 centimeter size single crystals of Beta-gallium oxide (Beta-Ga2O3). We used a flux and semi wet method to grow transparent good quality crystals. In the semi-wet method Ga2O3 was synthesized with starting gallium nitrate solution and urea as a nucleation agent. In the flux method we used tin and other metallic flux. This crystal was placed in an alumina crucible and temperature was raised above 1050 degrees Centigrade. After a time period of thirty hours, we observed prismatic and needle shaped crystals of gallium oxide. Scanning electron microscopic studies showed step growth morphology. Crystal was polished to measure the properties. Bandgap was measured 4.7electronvolts using the optical absorption curve. Another wide bandgap hexagonal 2H-SiC was grown by using Si-Al eutectic flux in the graphite crucible. We used slight AlN also as the impurity in the flux. The temperature was raised up to 1050 degrees Centigrade and slowly cooled to 850 degrees Centigrade. Preliminary characterization results of this material are also reported.

Nanobonding: A key technology for emerging applications in health and environmental sciences

NASA Astrophysics Data System (ADS)

Howlader, Matiar M. R.; Deen, M. Jamal; Suga, Tadatomo

2015-03-01

In this paper, surface-activation-based nanobonding technology and its applications are described. This bonding technology allows for the integration of electronic, photonic, fluidic and mechanical components into small form-factor systems for emerging sensing and imaging applications in health and environmental sciences. Here, we describe four different nanobonding techniques that have been used for the integration of various substrates — silicon, gallium arsenide, glass, and gold. We use these substrates to create electronic (silicon), photonic (silicon and gallium arsenide), microelectromechanical (glass and silicon), and fluidic (silicon and glass) components for biosensing and bioimaging systems being developed. Our nanobonding technologies provide void-free, strong, and nanometer scale bonding at room temperature or at low temperatures (<200 °C), and do not require chemicals, adhesives, or high external pressure. The interfaces of the nanobonded materials in ultra-high vacuum and in air correspond to covalent bonds, and hydrogen or hydroxyl bonds, respectively.

Influence of Post-Heat Treatment of ZnO:Al Transparent Electrode for Copper Indium Gallium Selenide Thin Film Solar Cell.

PubMed

Eom, Taewoo; Park, Jeong Eun; Park, Sang Yong; Park, Jeong Hoon; Bweupe, Jackson; Lim, Donggun

2018-09-01

Copper indium gallium selenide (CIGS) thin film solar cells have been regarded as a candidate for energy conversion devices owing to their high absorption coefficient, high temperature stability, and low cost. ZnO:Al thin film is commonly used in CIGS solar cells as a window layer. In this study, ZnO:Al films were deposited on glass under various post-heat temperature using RF sputtering to observe the characteristics of ZnO:Al films such as Hall mobility, carrier concentration, and resistivity; subsequently, the ZnO:Al films were applied to a CIGS solar cell as a window. CIGS solar cells fabricated with various ZnO:Al films were analyzed in order to investigate their influence. The test results showed that the improvement of ZnO:Al characteristics affects Jsc and Voc in the solar cell through reduced recombination and increase of optical property.

Phosphorization boosts the capacitance of mixed metal nanosheet arrays for high performance supercapacitor electrodes.

PubMed

Lan, Yingying; Zhao, Hongyang; Zong, Yan; Li, Xinghua; Sun, Yong; Feng, Juan; Wang, Yan; Zheng, Xinliang; Du, Yaping

2018-05-01

Binary transition metal phosphides hold immense potential as innovative electrode materials for constructing high-performance energy storage devices. Herein, porous binary nickel-cobalt phosphide (NiCoP) nanosheet arrays anchored on nickel foam (NF) were rationally designed as self-supported binder-free electrodes with high supercapacitance performance. Taking the combined advantages of compositional features and array architectures, the nickel foam supported NiCoP nanosheet array (NiCoP@NF) electrode possesses superior electrochemical performance in comparison with Ni-Co LDH@NF and NiCoO2@NF electrodes. The NiCoP@NF electrode shows an ultrahigh specific capacitance of 2143 F g-1 at 1 A g-1 and retained 1615 F g-1 even at 20 A g-1, showing excellent rate performance. Furthermore, a binder-free all-solid-state asymmetric supercapacitor device is designed, which exhibits a high energy density of 27 W h kg-1 at a power density of 647 W kg-1. The hierarchical binary nickel-cobalt phosphide nanosheet arrays hold great promise as advanced electrode materials for supercapacitors with high electrochemical performance.

Mechanical mixtures of metal oxides and phosphorus pentoxide as novel precursors for the synthesis of transition-metal phosphides.

PubMed

Guo, Lijuan; Zhao, Yu; Yao, Zhiwei

2016-01-21

This study presents a new type of precursor, mechanical mixtures of metal oxides (MOs) and phosphorus pentoxide (P2O5) are used to synthesize Ni2P, Co2P and MoP phosphides by the H2 reduction method. In addition, this is first report of common solid-state P2O5 being used as a P source for the synthesis of metal phosphides. The traditional precursors are usually prepared via a complicated preparation procedure involving dissolution, drying and calcination steps. However, these novel MOs/P2O5 precursors can be obtained only by simple mechanical mixing of the starting materials. Furthermore, unlike the direct transformation from amorphous phases to phosphides, various specific intermediates were involved in the transformation from MOs/P2O5 to phosphides. It is worthy to note that the dispersions of Ni2P, Co2P and MoP obtained from MOs/P2O5 precursors were superior to those of the corresponding phosphides prepared from the abovementioned traditional precursors. It is suggested that the morphology of the as-prepared metal phosphides might be inherited from the corresponding MOs. Based on the results of XRD, XPS, SEM and TEM, the formation pathway of phosphides can be defined as MOs/P2O5 precursors → complex intermediates (metals, metal phosphates and metal oxide-phosphates) → metal phosphides.

New Intermetallic Ternary Phosphide Chalcogenide AP2-xXx (A = Zr, Hf; X = S, Se) Superconductors with PbFCl-Type Crystal Structure

NASA Astrophysics Data System (ADS)

Kitô, Hijiri; Yanagi, Yousuke; Ishida, Shigeyuki; Oka, Kunihiko; Gotoh, Yoshito; Fujihisa, Hiroshi; Yoshida, Yoshiyuki; Iyo, Akira; Eisaki, Hiroshi

2014-07-01

We have synthesized a series of intermetallic ternary phosphide chalcogenide superconductors, AP2-xXx (A = Zr, Hf; X = S, Se), using the high-pressure synthesis technique. These materials have a PbFCl-type crystal structure (space group P4/nmm) when x is greater than 0.3. The superconducting transition temperature Tc changes systematically with x, yielding dome-like phase diagrams. The maximum Tc is achieved at approximately x = 0.7, at which point the Tc is 6.3 K for ZrP2-xSex (x = 0.75), 5.5 K for HfP2-xSex (x = 0.7), 5.0 K for ZrP2-xSx (x = 0.675), and 4.6 K for Hfp2-xSx (x = 0.5). They are typical type-II superconductors and the upper and lower critical fields are estimated to be 2.92 T at 0 K and 0.021 T at 2 K for ZrP2-xSex (x = 0.75), respectively.

Structure property relationships in gallium oxide thin films grown by pulsed laser deposition [Structure property relationships in Ga 2O 3 thin films grown by pulsed laser deposition

DOE PAGES

Garten, Lauren M.; Zakutayev, Andriy; Perkins, John D.; ...

2016-11-21

Beta-gallium oxide (β-Ga 2O 3) is of increasing interest to the optoelectronic community for transparent conductor and power electronic applications. Considerable variability exists in the literature on the growth and doping of Ga 2O 3 films, especially as a function of growth approach, temperature, and oxygen partial pressure. Here pulsed laser deposition (PLD) was used to grow high-quality β-Ga 2O 3 films on (0001) sapphire and (–201) Ga 2O 3 single crystals and to explore the growth, stability, and dopability of these films as function of temperature and oxygen partial pressure. As a result, there is a strong temperature dependencemore » to the phase formation, morphology, and electronic properties of β-Ga 2O 3 from 350 to 550 °C.« less

Thin-film copper indium gallium selenide solar cell based on low-temperature all-printing process.

PubMed

Singh, Manjeet; Jiu, Jinting; Sugahara, Tohru; Suganuma, Katsuaki

2014-09-24

In the solar cell field, development of simple, low-cost, and low-temperature fabrication processes has become an important trend for energy-saving and environmental issues. Copper indium gallium selenide (CIGS) solar cells have attracted much attention due to the high absorption coefficient, tunable band gap energy, and high efficiency. However, vacuum and high-temperature processing in fabrication of solar cells have limited the applications. There is a strong need to develop simple and scalable methods. In this work, a CIGS solar cell based on all printing steps and low-temperature annealing is developed. CIGS absorber thin film is deposited by using dodecylamine-stabilized CIGS nanoparticle ink followed by printing buffer layer. Silver nanowire (AgNW) ink and sol-gel-derived ZnO precursor solution are used to prepare a highly conductive window layer ZnO/[AgNW/ZnO] electrode with a printing method that achieves 16 Ω/sq sheet resistance and 94% transparency. A CIGS solar cell based on all printing processes exhibits efficiency of 1.6% with open circuit voltage of 0.48 V, short circuit current density of 9.7 mA/cm(2), and fill factor of 0.34 for 200 nm thick CIGS film, fabricated under ambient conditions and annealed at 250 °C.

TiO2-Based Indium Phosphide Metal-Oxide-Semiconductor Capacitor with High Capacitance Density.

PubMed

Cheng, Chun-Hu; Hsu, Hsiao-Hsuan; Chou, Kun-i

2015-04-01

We report a low-temperature InP p-MOS with a high capacitance density of 2.7 µF/cm2, low leakage current of 0.77 A/cm2 at 1 V and tight current distribution. The high-density and low-leakage InP MOS was achieved by using high-κ TiLaO dielectric and ultra-thin SiO2 buffer layer with a thickness of less than 0.5 nm. The obtained EOT can be aggressively scaled down to < 1 nm through the use of stacked TiLaO/SiO2 dielectric, which has the potential for the future application of high mobility III-V CMOS devices.

Comparison of GaP nanowires grown from Au and Sn vapor-liquid-solid catalysts as photoelectrode materials

NASA Astrophysics Data System (ADS)

Lee, Sudarat; Wen, Wen; Cheek, Quintin; Maldonado, Stephen

2018-01-01

Gallium phosphide (GaP) nanowire film electrodes have been prepared via solid sublimation of GaP powder using both gold (Au) and tin (Sn) nanoparticles as the vapor-liquid-solid (VLS) catalysts on Si(1 1 1) and GaP(1 1 1)B substrates. The resultant GaP nanowires are compared and contrasted in terms of structures and photoactivity in photoelectrochemical half cells. Raman spectra implicated a difference in the surface condition of the two types of nanowires. Complete wet etching removal of metallic VLS catalysts from the as-prepared GaP nanowires was possible with Sn catalysts but not with Au catalysts. The photoresponses of both Sn- and Au-seeded GaP nanowire films were collected and examined under 100 mW cm-2 white light illumination. Au-seeded nanowire films exhibited strong n-type characteristics when measured in nonaqueous electrolyte with ferrocene/ferricenium as the redox species while Sn-seeded nanowires showed behavior consistent with degenerate n-type doping.

Heat resistive dielectric multi-layer micro-mirror array in epitaxial lateral overgrowth gallium nitride.

PubMed

Huang, Chen-Yang; Ku, Hao-Min; Liao, Wei-Tsai; Chao, Chu-Li; Tsay, Jenq-Dar; Chao, Shiuh

2009-03-30

Ta2O5 / SiO2 dielectric multi-layer micro-mirror array (MMA) with 3mm mirror size and 6mm array period was fabricated on c-plane sapphire substrate. The MMA was subjected to 1200 degrees C high temperature annealing and remained intact with high reflectance in contrast to the continuous multi-layer for which the layers have undergone severe damage by 1200 degrees C annealing. Epitaxial lateral overgrowth (ELO) of gallium nitride (GaN) was applied to the MMA that was deposited on both sapphire and sapphire with 2:56 mm GaN template. The MMA was fully embedded in the ELO GaN and remained intact. The result implies that our MMA is compatible to the high temperature growth environment of GaN and the MMA could be incorporated into the structure of the micro-LED array as a one to one micro backlight reflector, or as the patterned structure on the large area LED for controlling the output light.

Synthesis of gallium nitride nanostructures by nitridation of electrochemically deposited gallium oxide on silicon substrate.

PubMed

Ghazali, Norizzawati Mohd; Yasui, Kanji; Hashim, Abdul Manaf

2014-01-01

Gallium nitride (GaN) nanostructures were successfully synthesized by the nitridation of the electrochemically deposited gallium oxide (Ga2O3) through the utilization of a so-called ammoniating process. Ga2O3 nanostructures were firstly deposited on Si substrate by a simple two-terminal electrochemical technique at a constant current density of 0.15 A/cm(2) using a mixture of Ga2O3, HCl, NH4OH and H2O for 2 h. Then, the deposited Ga2O3 sample was ammoniated in a horizontal quartz tube single zone furnace at various ammoniating times and temperatures. The complete nitridation of Ga2O3 nanostructures at temperatures of 850°C and below was not observed even the ammoniating time was kept up to 45 min. After the ammoniating process at temperature of 900°C for 15 min, several prominent diffraction peaks correspond to hexagonal GaN (h-GaN) planes were detected, while no diffraction peak of Ga2O3 structure was detected, suggesting a complete transformation of Ga2O3 to GaN. Thus, temperature seems to be a key parameter in a nitridation process where the deoxidization rate of Ga2O3 to generate gaseous Ga2O increase with temperature. The growth mechanism for the transformation of Ga2O3 to GaN was proposed and discussed. It was found that a complete transformation can not be realized without a complete deoxidization of Ga2O3. A significant change of morphological structures takes place after a complete transformation of Ga2O3 to GaN where the original nanorod structures of Ga2O3 diminish, and a new nanowire-like GaN structures appear. These results show that the presented method seems to be promising in producing high-quality h-GaN nanostructures on Si.

Synthesis of gallium nitride nanostructures by nitridation of electrochemically deposited gallium oxide on silicon substrate

PubMed Central

2014-01-01

Gallium nitride (GaN) nanostructures were successfully synthesized by the nitridation of the electrochemically deposited gallium oxide (Ga2O3) through the utilization of a so-called ammoniating process. Ga2O3 nanostructures were firstly deposited on Si substrate by a simple two-terminal electrochemical technique at a constant current density of 0.15 A/cm2 using a mixture of Ga2O3, HCl, NH4OH and H2O for 2 h. Then, the deposited Ga2O3 sample was ammoniated in a horizontal quartz tube single zone furnace at various ammoniating times and temperatures. The complete nitridation of Ga2O3 nanostructures at temperatures of 850°C and below was not observed even the ammoniating time was kept up to 45 min. After the ammoniating process at temperature of 900°C for 15 min, several prominent diffraction peaks correspond to hexagonal GaN (h-GaN) planes were detected, while no diffraction peak of Ga2O3 structure was detected, suggesting a complete transformation of Ga2O3 to GaN. Thus, temperature seems to be a key parameter in a nitridation process where the deoxidization rate of Ga2O3 to generate gaseous Ga2O increase with temperature. The growth mechanism for the transformation of Ga2O3 to GaN was proposed and discussed. It was found that a complete transformation can not be realized without a complete deoxidization of Ga2O3. A significant change of morphological structures takes place after a complete transformation of Ga2O3 to GaN where the original nanorod structures of Ga2O3 diminish, and a new nanowire-like GaN structures appear. These results show that the presented method seems to be promising in producing high-quality h-GaN nanostructures on Si. PMID:25593562

Modeling of high efficiency solar cells under laser pulse for power beaming applications

NASA Technical Reports Server (NTRS)

Jain, Raj K.; Landis, Geoffrey A.

1994-01-01

Solar cells have been used to convert sunlight to electrical energy for many years and also offer great potential for non-solar energy conversion applications. Their greatly improved performance under monochromatic light compared to sunlight, makes them suitable as photovoltaic (PV) receivers in laser power beaming applications. Laser beamed power to a PV array receiver could provide power to satellites, an orbital transfer vehicle, or a lunar base. Gallium arsenide (GaAs) and indium phosphide (InP) solar cells have calculated efficiencies of more than 50 percent under continuous illumination at the optimum wavelength. Currently high power free-electron lasers are being developed which operate in pulsed conditions. Understanding cell behavior under a laser pulse is important in the selection of the solar cell material and the laser. An experiment by NAsA lewis and JPL at the AVLIS laser facility in Livermore, CA presented experimental data on cell performance under pulsed laser illumination. Reference 5 contains an overview of technical issues concerning the use of solar cells for laser power conversion, written before the experiments were performed. As the experimental results showed, the actual effects of pulsed operation are more complicated. Reference 6 discusses simulations of the output of GaAs concentrator solar cells under pulsed laser illumination. The present paper continues this work, and compares the output of Si and GaAs solar cells.

A flexible master oscillator for a pulse-burst laser system

NASA Astrophysics Data System (ADS)

Den Hartog, D. J.; Young, W. C.

2015-12-01

A new master oscillator is being installed in the pulse-burst laser system used for high-rep-rate Thomson scattering on the MST experiment. This new master oscillator will enable pulse repetition rates up to 1 MHz, with the ability to program a burst of pulses with arbitrary and varying time separation between each pulse. In addition, the energy of each master oscillator pulse can be adjusted to compensate for gain variations in the power amplifier section of the laser system. This flexibility is accomplished by chopping a CW laser source with a high-bandwidth acousto-optic modulator (AOM). The laser source is a Laser Quantum ventus 1064 diode-pumped solid-state laser with continuous output power variable from 100 to 500 mW. The 1064 nm, 2.7 mm diameter polarized beam is focused into the gallium phosphide crystal of a Brimrose AOM, which deflects the beam by approximately 60 mR when driven by the 400 MHz fixed frequency driver. Beam deflection is controlled by a simple digital input pulse, and is capable of producing deflected pulses of less than 20 ns width at repetition rates much greater than 1 MHz. These deflected pulses from the output of the AOM are collimated and propagated into the laser amplifier system, where they will be amplified to ~ 2 J/pulse and injected into the MST plasma.

Separating and Recycling Plastic, Glass, and Gallium from Waste Solar Cell Modules by Nitrogen Pyrolysis and Vacuum Decomposition.

PubMed

Zhang, Lingen; Xu, Zhenming

2016-09-06

Many countries have gained benefits through the solar cells industry due to its high efficiency and nonpolluting power generation associated with solar energy. Accordingly, the market of solar cell modules is expanding rapidly in recent decade. However, how to environmentally friendly and effectively recycle waste solar cell modules is seldom concerned. Based on nitrogen pyrolysis and vacuum decomposition, this work can successfully recycle useful organic components, glass, and gallium from solar cell modules. The results were summarized as follows: (i) nitrogen pyrolysis process can effectively decompose plastic. Organic conversion rate approached 100% in the condition of 773 K, 30 min, and 0.5 L/min N2 flow rate. But, it should be noted that pyrolysis temperature should not exceed 773 K, and harmful products would be increased with the increasing of temperature, such as benzene and its derivatives by GC-MS measurement; (ii) separation principle, products analysis, and optimization of vacuum decomposition were discussed. Gallium can be well recycled under temperature of 1123 K, system pressure of 1 Pa and reaction time of 40 min. This technology is quite significant in accordance with the "Reduce, Reuse, and Recycle Principle" for solid waste, and provides an opportunity for sustainable development of photovoltaic industry.

Bright Room-Temperature Single-Photon Emission from Defects in Gallium Nitride.

PubMed

Berhane, Amanuel M; Jeong, Kwang-Yong; Bodrog, Zoltán; Fiedler, Saskia; Schröder, Tim; Triviño, Noelia Vico; Palacios, Tomás; Gali, Adam; Toth, Milos; Englund, Dirk; Aharonovich, Igor

2017-03-01

Room-temperature quantum emitters in gallium nitride (GaN) are reported. The emitters originate from cubic inclusions in hexagonal lattice and exhibit narrowband luminescence in the red spectral range. The sources are found in different GaN substrates, and therefore are promising for scalable quantum technologies. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High-pressure behavior of iron-nickel-cobalt phosphides and its implications for meteorites and planetary cores

NASA Astrophysics Data System (ADS)

Dera, P.; Lavina, B.; Borkowski, L. A.; Downs, R. T.; Prewitt, C. T.; Prakapenka, V.; Rivers, M. L.; Sutton, S.; Boctor, N.

2008-12-01

Minerals with composition (Fe,Ni)xP, are rare, but important accessory phases present in iron and chondrite meteorites. The occurrence of these minerals in meteoritic samples is believed to originate either from the equilibrium condensation of protoplanetary materials taking place in solar nebulae or from crystallization processes in the cores of parent bodies. Fe-Ni phosphides are considered an important candidate for a minor phase present in Earth's core, and at least partially responsible for the observed core density deficit with respect to pure Fe. We report results of high-pressure high-temperature single-crystal X- ray diffraction experiments with end-members belonging to the (Fe,Ni,Co)2P family, including Fe2P, Ni2P and Co2P. A new phase transition to the Co2Si-type structure (allabogdanite) has been found in Fe2P barringerite at 8.0 GPa, upon heating. The high-pressure phase can be quenched metastably to ambient conditions and then, if heated again, it transforms back to barringerite. Ni2P barringerite does not undergo transformation to allabogdanite structure up to 50 GPa, but instead exhibits incongruent melting with formation of pyrite-type NiP2 and Ni-P glass. Our results indicate that the presence of allabogdanite in meteoritic samples places two important constraints on the thermodynamic history of the meteorite. First, it imposes a minimum pressure and temperature for the formation of the Fe2P, and additionally rules out any higher temperature low pressure alterations. If present in the Earth's core, Fe2P will have the allabogdanite rather than the barringerite structure. Crystal chemical trends in the compressibility of (Fe,Ni,Co)2P minerals, as well as polymorphic transition paths are analyzed in the context of Earth and planetary core composition and properties.

Fabrication of hierarchical CoP nanosheet@microwire arrays via space-confined phosphidation toward high-efficiency water oxidation electrocatalysis under alkaline conditions.

PubMed

Ji, Xuqiang; Zhang, Rong; Shi, Xifeng; Asiri, Abdullah M; Zheng, Baozhan; Sun, Xuping

2018-05-03

In spite of recent advances in the synthesis of transition metal phosphide nanostructures, the simple fabrication of hierarchical arrays with more accessible active sites still remains a great challenge. In this Communication, we report a space-confined phosphidation strategy toward developing hierarchical CoP nanosheet@microwire arrays on nickel foam (CoP NS@MW/NF) using a Co(H2PO4)2·2H3PO4 microwire array as the precursor. The thermally stable nature of the anion in the precursor is key to hierarchical nanostructure formation. When used as a 3D electrode for water oxidation electrocatalysis, such CoP NS@MW/NF needs an overpotential as low as 296 mV to drive a geometrical catalytic current density of 100 mA cm-2 in 1.0 M KOH, outperforming all reported Co phosphide catalysts in alkaline media. This catalyst also shows superior long-term electrochemical durability, maintaining its activity for at least 65 h. This study offers us a general method for facile preparation of hierarchical arrays for applications.

Highly efficient photocatalytic H2 evolution using TiO2 nanoparticles integrated with electrocatalytic metal phosphides as cocatalysts

NASA Astrophysics Data System (ADS)

Song, Rui; Zhou, Wu; Luo, Bing; Jing, Dengwei

2017-09-01

In this work, electrocatalysts like the metal phosphides Ni2P, NiCoP, and FeP, can serve as cocatalysts of TiO2 to form efficient composite photocatalysts for hydrogen generation from an aqueous methanol solution. On comparing Ni2P, NiCoP, and FeP and optimizing their proportions, the NiCoP(1 wt%)/TiO2 composite was found to exhibit the highest activity toward photocatalytic H2 production (1.54 μmol h-1 mg-1), which is about thirteen times that of the naked TiO2 nanoparticles. Mott-Schottky (MS) analysis indicated that the large upward shift or band bending of the Fermi energy level (EF) in metal phosphides was responsible for the enhanced activity of the composites. The steady-state photoluminescence (PL) spectra and photocurrent transient response further confirmed that the enhanced photoinduced charge transfer and band separation after TiO2 was integrated with the metal phosphides. Thus, these electrocatalysts were shown to be efficient cocatalysts that can replace noble metals as low-cost photocatalytic H2 production.

Holographic lens spectrum splitting photovoltaic system for increased diffuse collection and annual energy yield

NASA Astrophysics Data System (ADS)

Vorndran, Shelby D.; Wu, Yuechen; Ayala, Silvana; Kostuk, Raymond K.

2015-09-01

Concentrating and spectrum splitting photovoltaic (PV) modules have a limited acceptance angle and thus suffer from optical loss under off-axis illumination. This loss manifests itself as a substantial reduction in energy yield in locations where a significant portion of insulation is diffuse. In this work, a spectrum splitting PV system is designed to efficiently collect and convert light in a range of illumination conditions. The system uses a holographic lens to concentrate shortwavelength light onto a smaller, more expensive indium gallium phosphide (InGaP) PV cell. The high efficiency PV cell near the axis is surrounded with silicon (Si), a less expensive material that collects a broader portion of the solar spectrum. Under direct illumination, the device achieves increased conversion efficiency from spectrum splitting. Under diffuse illumination, the device collects light with efficiency comparable to a flat-panel Si module. Design of the holographic lens is discussed. Optical efficiency and power output of the module under a range of illumination conditions from direct to diffuse are simulated with non-sequential raytracing software. Using direct and diffuse Typical Metrological Year (TMY3) irradiance measurements, annual energy yield of the module is calculated for several installation sites. Energy yield of the spectrum splitting module is compared to that of a full flat-panel Si reference module.

Gallium arsenide-gallium nitride wafer fusion and the n-aluminum gallium arsenide/p-gallium arsenide/n-gallium nitride double heterojunction bipolar transistor

NASA Astrophysics Data System (ADS)

Estrada, Sarah M.

This dissertation describes the n-AlGaAs/p-GaAs/n-GaN heterojunction bipolar transistor (HBT), the first transistor formed via wafer fusion. The fusion process was developed as a way to combine lattice-mismatched materials for high-performance electronic devices, not obtainable via conventional all-epitaxial formation methods. Despite the many challenges of wafer fusion, successful transistors were demonstrated and improved, via the optimization of material structure and fusion process conditions. Thus, this project demonstrated the integration of disparate device materials, chosen for their optimal electronic properties, unrestricted by the conventional (and very limiting) requirement of lattice-matching. By combining an AlGaAs-GaAs emitter-base with a GaN collector, the HBT benefited from the high breakdown voltage of GaN, and from the high emitter injection efficiency and low base transit time of AlGaAs-GaAs. Because the GaAs-GaN lattice mismatch precluded an all-epitaxial formation of the HBT, the GaAs-GaN heterostructure was formed via fusion. This project began with the development of a fusion process that formed mechanically robust and electrically active GaAs-GaN heterojunctions. During the correlation of device electrical performance with a systematic variation of fusion conditions over a wide range (500--750°C, 0.5--2hours), a mid-range fusion temperature was found to induce optimal HBT electrical performance. Transmission electron microscopy (TEM) and secondary ion mass spectrometry (SIMS) were used to assess possible reasons for the variations observed in device electrical performance. Fusion process conditions were correlated with electrical (I-V), structural (TEM), and chemical (SIMS) analyses of the resulting heterojunctions, in order to investigate the trade-off between increased interfacial disorder (TEM) with low fusion temperature and increased diffusion (SIMS) with high fusion temperature. The best do device results (IC ˜ 2.9 kA/cm2 and beta ˜ 3.5, at VCE = 20V and IB = 10mA) were obtained with an HBT formed via fusion at 600°C for 1 hour, with an optimized base-collector design. This was quite an improvement, as compared to an HBT with a simpler base-collector structure, also fused at 600°C for 1 hour (IC ˜ 0.83 kA/cm2 and beta ˜ 0.89, at VCE = 20V and IB = 10mA). Fused AlGaAs-GaAs-GaAs HBTs were compared to fused AlGaAs-GaAs-GaN HBTs, demonstrating that the use of a wider bandgap collector (Eg,GaN > Eg,GaAs) did indeed improve HBT performance at high applied voltages, as desired for high-power applications.

Greater-than-bulk melting temperatures explained: Gallium melts Gangnam style

NASA Astrophysics Data System (ADS)

Gaston, Nicola; Steenbergen, Krista

2014-03-01

The experimental discovery of superheating in gallium clusters contradicted the clear and well-demonstrated paradigm that the melting temperature of a particle should decrease with its size. However the extremely sensitive dependence of melting temperature on size also goes to the heart of cluster science, and the interplay between the effects of electronic and geometric structure. We have performed extensive first-principles molecular dynamics calculations, incorporating parallel tempering for an efficient exploration of configurational phase space. This is necessary, due to the complicated energy landscape of gallium. In the nanoparticles, melting is preceded by a transitions between phases. A structural feature, referred to here as the Gangnam motif, is found to increase with the latent heat and appears throughout the observed phase changes of this curious metal. We will present our detailed analysis of the solid-state isomers, performed using extensive statistical sampling of the trajectory data for the assignment of cluster structures to known phases of gallium. Finally, we explain the greater-than-bulk melting through analysis of the factors that stabilise the liquid structures.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Pei; Wang, Yonggang; Wang, Liping

Cubic (space group: Fm3¯m) iridium phosphide, Ir 2P, has been synthesized at high pressure and high temperature. Angle-dispersive synchrotron X-ray diffraction measurements on Ir 2P powder using a diamond-anvil cell at room temperature and high pressures (up to 40.6 GPa) yielded a bulk modulus of B 0 = 306(6) GPa and its pressure derivative B 0'= 6.4(5). Such a high bulk modulus attributed to the short and strongly covalent Ir-P bonds as revealed by first – principles calculations and three-dimensionally distributed [IrP 4] tetrahedron network. Indentation testing on a well–sintered polycrystalline sample yielded the hardness of 11.8(4) GPa. Relatively lowmore » shear modulus of ~64 GPa from theoretical calculations suggests a complicated overall bonding in Ir 2P with metallic, ionic, and covalent characteristics. Additionally, a spin glass behavior is indicated by magnetic susceptibility measurements.« less

Induced superconductivity in high-mobility two-dimensional electron gas in gallium arsenide heterostructures.

PubMed

Wan, Zhong; Kazakov, Aleksandr; Manfra, Michael J; Pfeiffer, Loren N; West, Ken W; Rokhinson, Leonid P

2015-06-11

Search for Majorana fermions renewed interest in semiconductor-superconductor interfaces, while a quest for higher-order non-Abelian excitations demands formation of superconducting contacts to materials with fractionalized excitations, such as a two-dimensional electron gas in a fractional quantum Hall regime. Here we report induced superconductivity in high-mobility two-dimensional electron gas in gallium arsenide heterostructures and development of highly transparent semiconductor-superconductor ohmic contacts. Supercurrent with characteristic temperature dependence of a ballistic junction has been observed across 0.6 μm, a regime previously achieved only in point contacts but essential to the formation of well separated non-Abelian states. High critical fields (>16 T) in NbN contacts enables investigation of an interplay between superconductivity and strongly correlated states in a two-dimensional electron gas at high magnetic fields.

Induced superconductivity in high-mobility two-dimensional electron gas in gallium arsenide heterostructures

PubMed Central

Wan, Zhong; Kazakov, Aleksandr; Manfra, Michael J.; Pfeiffer, Loren N.; West, Ken W.; Rokhinson, Leonid P.

2015-01-01

Search for Majorana fermions renewed interest in semiconductor–superconductor interfaces, while a quest for higher-order non-Abelian excitations demands formation of superconducting contacts to materials with fractionalized excitations, such as a two-dimensional electron gas in a fractional quantum Hall regime. Here we report induced superconductivity in high-mobility two-dimensional electron gas in gallium arsenide heterostructures and development of highly transparent semiconductor–superconductor ohmic contacts. Supercurrent with characteristic temperature dependence of a ballistic junction has been observed across 0.6 μm, a regime previously achieved only in point contacts but essential to the formation of well separated non-Abelian states. High critical fields (>16 T) in NbN contacts enables investigation of an interplay between superconductivity and strongly correlated states in a two-dimensional electron gas at high magnetic fields. PMID:26067452

Gas Source Molecular Beam Epitaxial Growth of GaN

DTIC Science & Technology

1992-11-25

identify by block number) FIELW GROUP SUB-GROUP 19. ABSTRACT (Continue on reverse if necessary and Identify by block number) Aluminum gallium nitride (AlGaN...AND TASK OBJECTIVES Aluminum gallium nitride (AIGaN) has long been recognized as a promising radiation hard optoelectronic material. AIGaN has a wide...Efficient, pure, low temperature sources for the gas source molecular beam epitaxial (GSMBE) growth of aluminum gallium nitride will essentially

The Mobility Enhancement of Indium Gallium Zinc Oxide Transistors via Low-temperature Crystallization using a Tantalum Catalytic Layer.

PubMed

Shin, Yeonwoo; Kim, Sang Tae; Kim, Kuntae; Kim, Mi Young; Oh, Saeroonter; Jeong, Jae Kyeong

2017-09-07

High-mobility indium gallium zinc oxide (IGZO) thin-film transistors (TFTs) are achieved through low-temperature crystallization enabled via a reaction with a transition metal catalytic layer. For conventional amorphous IGZO TFTs, the active layer crystallizes at thermal annealing temperatures of 600 °C or higher, which is not suitable for displays using a glass substrate. The crystallization temperature is reduced when in contact with a Ta layer, where partial crystallization at the IGZO back-channel occurs with annealing at 300 °C, while complete crystallization of the active layer occurs at 400 °C. The field-effect mobility is significantly boosted to 54.0 cm 2 /V·s for the IGZO device with a metal-induced polycrystalline channel formed at 300 °C compared to 18.1 cm 2 /V·s for an amorphous IGZO TFT without a catalytic layer. This work proposes a facile and effective route to enhance device performance by crystallizing the IGZO layer with standard annealing temperatures, without the introduction of expensive laser irradiation processes.

Electrical and Optical Performance Characteristics of 0.74-eV p/n InGaAs Monolithic Interconnected Modules

NASA Technical Reports Server (NTRS)

Wilt, David M.; Fatemi, Navid S.; Jenkins, Phillip P.; Weizer, Victor G.; Hoffman, Richard W., Jr.; Jain, Raj K.; Murray, Christopher S.; Riley, David R.

1997-01-01

There has been a traditional trade-off in thermophotovoltaic (TPV) energy conversion development between system efficiency and power density. This trade-off originates from the use of front surface spectral controls such as selective emitters and various types of filters. A monolithic interconnected module (MIM) structure has been developed which allows for both high power densities and high system efficiencies. The MIM device consists of many individual indium gallium arsenide (InGaAs) cells series-connected on a single semi-insulating indium phosphide (InP) substrate. The MIM is exposed to the entire emitter output, thereby maximizing output power density. An infrared (IR) reflector placed on the rear surface of the substrate returns the unused portion of the emitter output spectrum back to the emitter for recycling, thereby providing for high system efficiencies. Initial MIM development has focused on a 1 sq cm device consisting of eight (8) series interconnected cells. MIM devices, produced from 0.74-eV InGaAs, have demonstrated V(sub oc) = 3.2 volts, J(sub sc) = 70 mA/sq cm, and a fill factor of 66% under flashlamp testing. Infrared (IR) reflectance measurements (greater than 2 micron) of these devices indicate a reflectivity of greater than 82%. MIM devices produced from 0.55-eV InGaAs have also been demonstrated. In addition, conventional p/n InGaAs devices with record efficiencies (11.7% AM0) have been demonstrated.

InGaAs/InP Monolithic Interconnected Modules (MIM) for Thermophotovoltaic Applications

NASA Technical Reports Server (NTRS)

Wilt, David M.; Fatemi, Navid S.; Jenkins, Phillip P.; Weizer, Victor G.; Hoffman, Richard W., Jr.; Scheiman, David A.; Murray, Christopher S.; Riley, David R.

2004-01-01

There has been a traditional trade-off in thermophotovoltaic (TPV) energy conversion development between systems efficiency and power density. This trade-off originates from the use of front surface spectral controls such as selective emitters and various types of filters. A monolithic interconnected module (MIM) structure has been developed which allows for both high power densities and high system efficiencies. The MIM device consists of many individual indium gallium arsenide (InGaAs) devices series -connected on a single semi-insulating indium phosphide (InP) substrate. The MIMs are exposed to the entire emitter output, thereby maximizing output power density. An infrared (IR) reflector placed on the rear surface of the substrate returns the unused portion of the emitter output spectrum back to the emitter for recycling, thereby providing for high system efficiencies. Initial MIM development has focused on a 1 sq cm device consisting of eight series interconnected cells. MIM devices, produced from 0,74 eV InGAAs, have demonstrated V(sub infinity) = 3.23 volts, J(sub sc) = 70 mA/sq cm and a fill factor of 66% under flashlamp testing. Infrared (IR) reflectance measurement (less than 2 microns) of these devices indicate a reflectivity of less than 82%. MIM devices produced from 0.55 eV InGaAs have also been den=monstrated. In addition, conventional p/n InGaAs devices with record efficiencies (11.7% AM1) have been demonstrated.

Epitaxial gallium arsenide wafers

NASA Technical Reports Server (NTRS)

Black, J. F.; Robinson, L. B.

1971-01-01

The preparation of GaAs epitaxial layers by a vapor transport process using AsCl3, Ga and H2 was pursued to provide epitaxial wafers suitable for the fabrication of transferred electron oscillators and amplifiers operating in the subcritical region. Both n-n(+) structures, and n(++)-n-n(+) sandwich structures were grown using n(+) (Si-doped) GaAs substrates. Process variables such as the input AsCl3 concentration, gallium temperature, and substrate temperature and temperature gradient and their effects on properties are presented and discussed.

Why do gallium clusters have a higher melting point than the bulk?

PubMed

Chacko, S; Joshi, Kavita; Kanhere, D G; Blundell, S A

2004-04-02

Density functional molecular dynamical simulations have been performed on Ga17 and Ga13 clusters to understand the recently observed higher-than-bulk melting temperatures in small gallium clusters [Phys. Rev. Lett. 91, 215508 (2003)

General Strategy for the Synthesis of Transition-Metal Phosphide/N-Doped Carbon Frameworks for Hydrogen and Oxygen Evolution.

PubMed

Pu, Zonghua; Zhang, Chengtian; Amiinu, Ibrahim Saana; Li, Wenqiang; Wu, Lin; Mu, Shichun

2017-05-17

Transition metal phosphides (TMPs) have been identified as promising nonprecious metal electrocatalyst for hydrogen evolution reaction (HER) and other energy conversion reactions. Herein, we reported a general strategy for synthesis of a series of TMPs (Fe 2 P, FeP, Co 2 P, CoP, Ni 2 P, and Ni 12 P 5 ) nanoparticles (NPs) with different metal phases embedded in a N-doped carbon (NC) matrix using metal salt, ammonium dihydrogen phosphate, and melamine as precursor with varying molar ratios and thermolysis temperatures. The resultant TMPs can serve as highly active and durable bifunctional electrocatalyst toward HER and oxygen evolution reaction (OER). In particular, the Ni 2 P@NC phase only requires an overpotential of ∼138 mV to derive HER in 0.5 M H 2 SO 4, and ∼320 mV for OER in 1.0 M KOH at the current density of 10 mA cm -2 . Because of the encapsulation of NC that can effectively prevent corrosion of embedded TMP NPs, Ni 2 P@NC exhibits almost unfading catalytic performance even after 10 h under both acidic and alkaline solutions. This synthesis strategy provides a new avenue to exploring TMPs as highly active and stable electrocatalyst for the HER, OER, and other electrochemical applications.

Highly Efficient and Robust Nickel Phosphides as Bifunctional Electrocatalysts for Overall Water-Splitting.

PubMed

Li, Jiayuan; Li, Jing; Zhou, Xuemei; Xia, Zhaoming; Gao, Wei; Ma, Yuanyuan; Qu, Yongquan

2016-05-04

To search for the efficient non-noble metal based and/or earth-abundant electrocatalysts for overall water-splitting is critical to promote the clean-energy technologies for hydrogen economy. Herein, we report nickel phosphide (NixPy) catalysts with the controllable phases as the efficient bifunctional catalysts for water electrolysis. The phases of NixPy were determined by the temperatures of the solid-phase reaction between the ultrathin Ni(OH)2 plates and NaH2PO2·H2O. The NixPy with the richest Ni5P4 phase synthesized at 325 °C (NixPy-325) delivered efficient and robust catalytic performance for hydrogen evolution reaction (HER) in the electrolytes with a wide pH range. The NixPy-325 catalysts also exhibited a remarkable performance for oxygen evolution reaction (OER) in a strong alkaline electrolyte (1.0 M KOH) due to the formation of surface NiOOH species. Furthermore, the bifunctional NixPy-325 catalysts enabled a highly performed overall water-splitting with ∼100% Faradaic efficiency in 1.0 M KOH electrolyte, in which a low applied external potential of 1.57 V led to a stabilized catalytic current density of 10 mA/cm(2) over 60 h.

Near room temperature chemical vapor deposition of graphene with diluted methane and molten gallium catalyst.

PubMed

Fujita, Jun-Ichi; Hiyama, Takaki; Hirukawa, Ayaka; Kondo, Takahiro; Nakamura, Junji; Ito, Shin-Ichi; Araki, Ryosuke; Ito, Yoshikazu; Takeguchi, Masaki; Pai, Woei Wu

2017-09-28

Direct growth of graphene integrated into electronic devices is highly desirable but difficult due to the nominal ~1000 °C chemical vapor deposition (CVD) temperature, which can seriously deteriorate the substrates. Here we report a great reduction of graphene CVD temperature, down to 50 °C on sapphire and 100 °C on polycarbonate, by using dilute methane as the source and molten gallium (Ga) as catalysts. The very low temperature graphene synthesis is made possible by carbon attachment to the island edges of pre-existing graphene nuclei islands, and causes no damages to the substrates. A key benefit of using molten Ga catalyst is the enhanced methane absorption in Ga at lower temperatures; this leads to a surprisingly low apparent reaction barrier of ~0.16 eV below 300 °C. The faster growth kinetics due to a low reaction barrier and a demonstrated low-temperature graphene nuclei transfer protocol can facilitate practical direct graphene synthesis on many kinds of substrates down to 50-100 °C. Our results represent a significant progress in reducing graphene synthesis temperature and understanding its mechanism.

A Hybrid Multi-gate Model of a Gallium Nitride (GaN) High Electron Mobility Transistor (HEMT) Device Incorporating GaN-substrate Thermal Boundary Resistance

DTIC Science & Technology

2012-10-01

right by a pitch (P) and subsequently summed to provide a multi-gate superimposed temperature distribution ( TMG (x)). An example is shown in figure...temperature rise over the coolant, or the difference between the centerline multi gate junction temperature on the upper surface ( TMG ,GaN(0)) of the GaN...TC coolant temperature (°C) TCP(x) cold plate temperature distribution (°C) TGaN(x,y) temperature distribution within GaN (°C) TMG (x) multiple gate

Status of indium phosphide solar cell development at Spire

NASA Technical Reports Server (NTRS)

Spitzer, M. B.; Keavney, C. J.; Vernon, S. M.

1987-01-01

On-going development of indium phosphide solar cells for space applications is presented. The development is being carried out with a view towards both high conversion efficiency and simplicity of manufacture. The cell designs comprise the ion-implanted cell, the indium tin oxide top contact cell, and the epitaxial cell grown by metal organic chemical vapor deposition. Modelling data on the limit to the efficiency are presented and comparison is made to measured performance data.

Phase transformation of GaAs at high pressures and temperatures

NASA Astrophysics Data System (ADS)

Ono, Shigeaki; Kikegawa, Takumi

2018-02-01

The high-pressure behavior of gallium arsenide, GaAs, has been investigated using an in-situ X-ray powder diffraction technique in a diamond anvil cell combined with a resistance heating method, at pressures and temperatures up to 25 GPa and 1000 K respectively. The pressure-induced phase transition from a zincblende to an orthorhombic (Cmcm) structure was observed. This transition occurred at 17.3 GPa and at room temperature, where a negative temperature dependence for this transition was confirmed. The transition boundary was determined to be P (GPa) = 18.0 - 0.0025 × T (K).

Optimization of GaN thin films via MOCVD

NASA Technical Reports Server (NTRS)

Dickens, Corey; Wilson, Sylvia L.

1995-01-01

A unique characteristic of every semiconductor is the amount of energy required to break an electron bond in the lowest band of allowed states, the valence band. The energy necessary to set an electron free and allow it to conduct in the material is termed the energy gap (Eg). Semiconductors with wide bandgap energies have been shown to possess properties for high power, high temperature, radiation resistance damage, and short wavelength optoelectronic applications. Gallium nitride, which has a wide gap of 3.39 eV, is a material that has demonstrated these characteristics. Various growth conditions are being investigated for quality gallium nitride heteroepitaxy growth via the technique of low pressure metal organic chemical vapor deposition (MOCVD) that can be used for device development.

Experimental Analysis of Critical Current and Alternating Current Losses of High-Temperature Superconductor Tape with Resin and Gallium-Indium-Tin

PubMed Central

Sun, Yajie; Zhang, Huiming; Meng, Yuanzhu

2018-01-01

This paper experimentally analyzes the critical current degradation and AC (alternating current) losses of second-generation (2G) high-temperature superconductor (HTS) tape during the impregnation process. Two impregnation materials were utilized: Gallium-Indium-Tin (GaInSn), and an epoxy resin, Araldite. The critical current of the impregnation materials was measured after different thermal cycles and compared with the tape with no impregnation process. The experimental results show that the critical current of Yttrium Barium Copper Oxide (YBCO) short samples varies between differently impregnated materials. The resin, Araldite, degraded the critical current; however, the GaInSn showed no degradation. Two degradation patterns with Araldite were identified due to the impregnation process, and the corresponding causes were analyzed. We further measured the AC losses of tapes impregnated with liquid metal at different frequencies, up to 600 Hz. Based on the experimental results, GaInSn liquid metal should be the most suitable impregnation material in terms of critical current degradation. PMID:29642490

Experimental Analysis of Critical Current and Alternating Current Losses of High-Temperature Superconductor Tape with Resin and Gallium-Indium-Tin.

PubMed

Yu, Dongmin; Sun, Yajie; Zhang, Huiming; Meng, Yuanzhu; Liu, Huanan

2018-04-08

This paper experimentally analyzes the critical current degradation and AC (alternating current) losses of second-generation (2G) high-temperature superconductor (HTS) tape during the impregnation process. Two impregnation materials were utilized: Gallium-Indium-Tin (GaInSn), and an epoxy resin, Araldite. The critical current of the impregnation materials was measured after different thermal cycles and compared with the tape with no impregnation process. The experimental results show that the critical current of Yttrium Barium Copper Oxide (YBCO) short samples varies between differently impregnated materials. The resin, Araldite, degraded the critical current; however, the GaInSn showed no degradation. Two degradation patterns with Araldite were identified due to the impregnation process, and the corresponding causes were analyzed. We further measured the AC losses of tapes impregnated with liquid metal at different frequencies, up to 600 Hz. Based on the experimental results, GaInSn liquid metal should be the most suitable impregnation material in terms of critical current degradation.

Nanostructured Semiconductor Electrodes for Solar Energy Conversion and Innovations in Undergraduate Chemical Lab Curriculum

NASA Astrophysics Data System (ADS)

Lee, Sudarat

This dissertation presents the methodology and discussion of preparing nanostructured, high aspect ratio p-type phosphide-based binary and ternary semiconductors via "top-down" anodic etching, a process which creates nanostructures from a large parent entity, and "bottom-up" vapor-liquid-solid growth, a mechanism which builds up small clusters of molecules block-by-block. Such architecture is particularly useful for semiconducting materials with incompatible optical absorption depth and charge carrier diffusion length, as it not only relaxes the requirement for high-grade crystalline materials, but also increases the carrier collection efficiencies for photons with energy greater than or equal to the band gap. The main focus of this dissertation is to obtain nanostructured p-type phosphide semiconductors for photoelectrochemical (PEC) cell applications. Chapter II in the thesis describes a methodology for creating high-aspect ratio p-GaP that function as a photocathode under white light illumination. Gallium phosphide (GaP, band gap: 2.26 eV) is a suitable candidate for solar conversion and energy storage due to its ability to generate large photocurrent and photovoltage to drive fuel-forming reactions. Furthermore, the band edge positions of GaP can provide sufficient kinetics for the reduction of protons and carbon dioxide. The structure is prepared by anodic etching, and the resulting macroporous structures are subsequently doped with Zn by thermally driving in Zn from conformal ZnO films prepared by atomic layer deposition (ALD). The key finding of this work is a viable doping strategy involving ALD ZnO films for making functioning p-type GaP nanostructures. Chapter III compares the GaP nanowires grown from gold (Au) and tin (Sn) VLS catalysts in a benign solid sublimation growth scheme in terms of crystal structure and photoactivity. Sn is less noble than Au, allowing complete removal of Sn metal catalysts from the nanowires through wet chemical etching which found to be useful for subsequent thermal diffusion p-type doping without fear of contaminations like Au. The main finding of this work is Sn-seeded GaP nanowires although Sn was removed without any residues and the nanowires had less twin defects than Au-seeded GaP, the nanowires were degenerately n-doped. On the contrary, Au-seeded GaP nanowires exhibited n-type characteristics with orthogonalized light absorption and charge separation. Chapter IV describes the synthesis of zinc tin phosphide (ZSP), a ternary analog of GaP comprised of low-cost, earth-abundant elements in the nanowire form using Sn nanoparticles as the VLS growth seed. The as-prepared ZSP nanowire film is capable of sustaining stable cathodic photoresponse in aqueous electrolyte under white light illumination. The nanowires were crystalized in the stoichiometric sphalerite form and possessed a direct optical band gap of ˜ 1.5 eV instead of the chalcopyrite structure that has comparable band gap energy to GaP. The Sn nanoparticles acted as the VLS seed as well as Sn source for the ZnSnP 2 nanowires growth. Chapter V summarizes the progress and findings of p-GaP nanowire array films as well as a phase non-specific, persistent ALD dye attachment scheme that facilitates hole injection into p-GaP photocathodes, extending the photon absorption range beyond its band gap. Lastly, a separate work about undergraduate chemical education development is documented in Chapter VI of this thesis. Chapter VI details the efforts made in two distinct undergraduate laboratory coursework with the intention to introduce modern microfluidics and photovoltaic technologies including multidisciplinary research experience to the undergraduate students.

In-situ, Gate Bias Dependent Study of Neutron Irradiation Effects on AlGaN/GaN HFETs

DTIC Science & Technology

2010-03-01

band gap and high breakdown field, AlGaN devices can operate at very high temperature and operating frequency. AlGaN/GaN based structures, have been...stable under ambient conditions [3]. GaN has a wide, direct band gap of 3.4 eV. It is therefore suitable for high temperature devices. Its high...also be grown with a wurtzite crystal structure and has a band - gap of 6.1 eV. Aluminum, due to having smaller atoms than gallium, forms a smaller

Advances in liquid metals for biomedical applications.

PubMed

Yan, Junjie; Lu, Yue; Chen, Guojun; Yang, Min; Gu, Zhen

2018-04-23

To date, liquid metals have been widely applied in many fields such as electronics, mechanical engineering and energy. In the last decade, with a better understanding of the physicochemical properties such as low viscosity, good fluidity, high thermal/electrical conductivity and good biocompatibility, gallium and gallium-based low-melting-point (near or below physiological temperature) alloys have attracted considerable attention in bio-related applications. This tutorial review introduces the common performances of liquid metals, highlights their featured properties, as well as summarizes various state-of-the-art bio-applications involving carriers for drug delivery, molecular imaging, cancer therapy and biomedical devices. Challenges for the clinical translation of liquid metals are also discussed.

Multiple quarantine treatment using bale compression and a three-day fumigation to control Hessian fly (Diptera: Cecidomyiidae) in exported hay.

PubMed

Yokoyama, Victoria Y

2014-06-01

A multiple quarantine treatment was developed to control Hessian fly puparia, Mayetiola destructor (Say), the stage of regulatory concern in exported hay. In a commercial test using 51.589 puparia, no insects survived to the adult stage after exposure to bale compression at 137 kg/cm2 and fumigation with 61 g/28.3 m3 hydrogen phosphide for 3d. The puparia were fumigated in infested wheat seedlings in cloth bags inside compressed timothy bales placed in different locations in three replicate freight containers in a heated building. Fumigant concentrations were 345-522 ppm on day 1; 580-824 ppm on day 2; and 680-861 ppm on day 3. Monitored temperatures were < 20 degrees C in all locations allowing the fumigation temperature to be established at > or = 20 degrees C. Copper detection plate corrosion values were severe inside the freight container doors, and moderate in the middle of bales in all locations, providing visual confirmation of exposure to hydrogen phosphide. Hydrogen phosphide residues in exposed hay bales were found in trace amounts, below the U.S. Environmental Protection Agency tolerance of 0.1 ppm for animal feeds. Timothy hay used in the commercial test is the representative species for all previously exported hay and straw species. The new multiple quarantine treatment is proposed for use with all previously tested bale sizes and wrapper styles for which 3-d fumigation data has been reported, and for bales and wrappers derived from those tested.

Deoxygenation of Palmitic Acid on Unsupported Transition-Metal Phosphides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peroni, Marco; Lee, Insu; Huang, Xiaoyang

Abstract Highly active bulk transition metal phosphides (WP, MoP, and Ni2P) were synthesized for the catalytic hydrodeoxygenation of palmitic acid, hexadecanol, hexadecanal, and microalgae oil. The specific activities positively correlated with the concentration of exposed metal sites, although the relative rates changed with temperature due to activation energies varying from 57 kJ·mol-1 for MoP to 142 kJ·mol-1 for WP. The reduction of the fatty acid to the aldehyde occurs through a Langmuir-Hinshelwood mechanism, where the rate-determining step is the addition of the second H to the hydrocarbon. On WP, the conversion of palmitic acid proceeds via R-CH2COOH R-CH2CHO R-CH2CH2OH R-CHCH2more » R-CH2CH3 (hydrodeoxygenation). Decarbonylation of the intermittently formed aldehyde (R-CH2COOH R-CH2CHO R-CH3) was an important pathway on MoP and Ni2P. Conversion via dehydration to a ketene, followed by its decarbonylation occurred only on Ni2P. The rates of alcohol dehydration (R-CH2CH2OH R-CHCH2) correlate with the concentration of Lewis acid sites of the phosphides. Acknowledgements The authors would like to thank Roel Prins for the critical discussion of the results. We are also grateful to Xaver Hecht for technical support. Funding by the German Federal Ministry of Food and Agriculture in the framework of the Advanced Biomass Value project (03SF0446A) is gratefully acknowledged. J.A.L. acknowledges support for his contribution by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences for exploring non-oxidic supports for deoxygenation reactions.« less

Effects of O2 plasma post-treatment on ZnO: Ga thin films grown by H2O-thermal ALD

NASA Astrophysics Data System (ADS)

Lee, Yueh-Lin; Chuang, Jia-Hao; Huang, Tzu-Hsuan; Ho, Chong-Long; Wu, Meng-Chyi

2013-03-01

Transparent conducting oxides have been widely employed in optoelectronic devices using the various deposition methods such as sputtering, thermal evaporator, and e-gun evaporator technologies.1-3 In this work, gallium doped zinc oxide (ZnO:Ga) thin films were grown on glass substrates via H2O-thermal atomic layer deposition (ALD) at different deposition temperatures. ALD-GZO thin films were constituted as a layer-by-layer structure by stacking zinc oxides and gallium oxides. Diethylzinc (DEZ), triethylgallium (TEG) and H2O were used as zinc, gallium precursors and oxygen source, respectively. Furthermore, we investigated the influences of O2 plasma post-treatment power on the surface morphology, electrical and optical property of ZnO:Ga films. As the result of O2 plasma post-treatment, the characteristics of ZnO:Ga films exhibit a smooth surface, low resistivity, high carrier concentration, and high optical transmittance in the visible spectrum. However, the transmittance decreases with O2 plasma power in the near- and mid-infrared regions.

Epitaxial Deposition Of Germanium Doped With Gallium

NASA Technical Reports Server (NTRS)

Huffman, James E.

1994-01-01

Epitaxial layers of germanium doped with gallium made by chemical vapor deposition. Method involves combination of techniques and materials used in chemical vapor deposition with GeH4 or GeCl4 as source of germanium and GaCl3 as source of gallium. Resulting epitaxial layers of germanium doped with gallium expected to be highly pure, with high crystalline quality. High-quality material useful in infrared sensors.

Gallium ion-assisted room temperature synthesis of small-diameter ZnO nanorods.

PubMed

Cho, Seungho; Kim, Semi; Lee, Kun-Hong

2011-09-15

We report a method for synthesizing small-diameter ZnO nanorods at room temperature (20 °C), under normal atmospheric pressure (1 atm), and using a relatively short reaction time (1 h) by adding gallium salts to the reaction solution. The ZnO nanorods were, on average, 92 nm in length and 9 nm in diameter and were single crystalline in nature. Quantitative analyses revealed that gallium atoms were not incorporated into the synthesized nanocrystals. On the basis of the experimental results, we propose a mechanism for the formation of small-diameter ZnO nanorods in the presence of gallium ions. The optical properties were probed by UV-Vis diffuse reflectance spectroscopy. The absorption band of the small-diameter ZnO nanorods was blue-shifted relative to the absorption band of the ~230 nm diameter ZnO nanorods (control samples). Control experiments demonstrated that the absence of metal ion-containing precipitants (except ZnO) at room temperature is essential, and that the ZnO nanorod diameter distributions were narrow for the stirred reaction solution and broad when prepared without stirring. Copyright © 2011 Elsevier Inc. All rights reserved.

Characterization of solar cells for space applications. Volume 14: Electrical characteristics of Hughes liquid phase epitaxy gallium arsenide solar cells as a function of intensity, temperature and irradiation

NASA Technical Reports Server (NTRS)

Anspaugh, B. E.; Downing, R. G.; Miyahira, T. F.; Weiss, R. S.

1981-01-01

Electrical characteristics of liquid phase epitaxy, P/N gallium aluminum arsenide solar cells are presented in graphical and tabular format as a function of solar illumination intensity and temperature. The solar cells were exposed to 1 MeV electron fluences of, respectively, 0, one hundred trillion, one quadrillion, and ten quadrillion e/sq cm.

40 CFR 180.284 - Zinc phosphide; tolerances for residues.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 24 2014-07-01 2014-07-01 false Zinc phosphide; tolerances for residues. 180.284 Section 180.284 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Specific Tolerances § 180.284 Zinc phosphide; tolerances for...

40 CFR 180.284 - Zinc phosphide; tolerances for residues.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 25 2012-07-01 2012-07-01 false Zinc phosphide; tolerances for residues. 180.284 Section 180.284 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Specific Tolerances § 180.284 Zinc phosphide; tolerances for...

40 CFR 180.284 - Zinc phosphide; tolerances for residues.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 25 2013-07-01 2013-07-01 false Zinc phosphide; tolerances for residues. 180.284 Section 180.284 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Specific Tolerances § 180.284 Zinc phosphide; tolerances for...

Metal Phosphides and Phosphates-based Electrodes for Electrochemical Supercapacitors.

PubMed

Li, Xin; Elshahawy, Abdelnaby M; Guan, Cao; Wang, John

2017-10-01

Phosphorus compounds, such as metal phosphides and phosphates have shown excellent performances and great potential in electrochemical energy storage, which are demonstrated by research works published in recent years. Some of these metal phosphides and phosphates and their hybrids compare favorably with transition metal oxides/hydroxides, which have been studied extensively as a class of electrode materials for supercapacitor applications, where they have limitations in terms of electrical and ion conductivity and device stability. To be specific, metal phosphides have both metalloid characteristics and good electric conductivity. For metal phosphates, the open-framework structures with large channels and cavities endow them with good ion conductivity and charge storage capacity. In this review, we present the recent progress on metal phosphides and phosphates, by focusing on their advantages/disadvantages and potential applications as a new class of electrode materials in supercapacitors. The synthesis methods to prepare these metal phosphides/phosphates are looked into, together with the scientific insights involved, as they strongly affect the electrochemical energy storage performance. Particular attentions are paid to those hybrid-type materials, where strong synergistic effects exist. In the summary, the future perspectives and challenges for the metal phosphides, phosphates and hybrid-types are proposed and discussed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Two-Dimensional Liquid Structure Explains the Elevated Melting Temperatures of Gallium Nanoclusters.

PubMed

Steenbergen, Krista G; Gaston, Nicola

2016-01-13

Melting in finite-sized materials differs in two ways from the solid-liquid phase transition in bulk systems. First, there is an inherent scaling of the melting temperature below that of the bulk, known as melting point depression. Second, at small sizes changes in melting temperature become nonmonotonic and show a size-dependence that is sensitive to the structure of the particle. Melting temperatures that exceed those of the bulk material have been shown to occur for a very limited range of nanoclusters, including gallium, but have still never been ascribed a convincing physical explanation. Here, we analyze the structure of the liquid phase in gallium clusters based on molecular dynamics simulations that reproduce the greater-than-bulk melting behavior observed in experiments. We observe persistent nonspherical shape distortion indicating a stabilization of the surface, which invalidates the paradigm of melting point depression. This shape distortion suggests that the surface acts as a constraint on the liquid state that lowers its entropy relative to that of the bulk liquid and thus raises the melting temperature.

Reversible Size Control of Liquid-Metal Nanoparticles under Ultrasonication.

PubMed

Yamaguchi, Akihisa; Mashima, Yu; Iyoda, Tomokazu

2015-10-19

This paper describes the reversible control of the size of liquid-metal nanoparticles under ultrasonication. Gallium was utilized as a liquid metal, which has a melting point of 29.8 °C. Investigating the effects of ultrasonication (power, time, and temperature) on the formation of gallium nanoparticles revealed that the process is similar to the formation of oil in water (O/W) or water in oil (W/O) emulsions, as the temperature significantly affects the size of the gallium nanoparticles (GaNPs). Under ultrasonication, the balance between the break-up and coalescence of the GaNPs can be adjusted by changing the temperature or adding acid through modulating the natural surface oxide layer (which can be removed with acid) and the stabilizing effect of the surfactant dodecanethiol. Coalescence was predominant at higher temperatures, whereas particle break-up was found to be predominant at lower temperatures. Furthermore, the change in size was accompanied by a shift in the plasmonic absorption of the GaNPs in the UV region. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Measuring Nanoscale Heat Transfer for Gold-(Gallium Oxide)-Gallium Nitride Interfaces as a Function

NASA Astrophysics Data System (ADS)

Szwejkowski, Chester; Sun, Kai; Constantin, Costel; Giri, Ashutosh; Saltonstall, Christopher; Hopkins, Patrick; NanoSynCh Team; Exsite Team

2014-03-01

Gallium nitride (GaN) is considered the most important semiconductor after the discovery of Silicon. Understanding the properties of GaN is imperative in determining the utility and applicability of this class of materials to devices. We present results of time domain thermoreflectance (TDTR) measurements as a function of surface root mean square (RMS) roughness. We used commercially available 5mm x 5mm, single-side polished GaN (3-7 μm)/Sapphire (430 μm) substrates that have a Wurtzite crystal structure and are slightly n-type doped. The GaN substrates were annealed in the open atmosphere for 10 minutes (900-1000 °C). This high-temperature treatment produced RMS values from 1-60 nm and growth of gallium oxide (GaO) as measured with an atomic force microscopy and transmission electron microscopy respectively. A gold film (80nm) was deposited on the GaN surface using electron beam physical vapor deposition which was verified using ellipsometry and profilometry. The TDTR measurements suggest that the thermal conductivity decays exponentially with RMS roughness and that there is a minimum value for thermal boundary conductance at a roughness of 15nm.

Advanced Density Functional Theory Methods for Materials Science

NASA Astrophysics Data System (ADS)

Demers, Steven

In this work we chiefly deal with two broad classes of problems in computational materials science, determining the doping mechanism in a semiconductor and developing an extreme condition equation of state. While solving certain aspects of these questions is well-trodden ground, both require extending the reach of existing methods to fully answer them. Here we choose to build upon the framework of density functional theory (DFT) which provides an efficient means to investigate a system from a quantum mechanics description. Zinc Phosphide (Zn3P2) could be the basis for cheap and highly efficient solar cells. Its use in this regard is limited by the difficulty in n-type doping the material. In an effort to understand the mechanism behind this, the energetics and electronic structure of intrinsic point defects in zinc phosphide are studied using generalized Kohn-Sham theory and utilizing the Heyd, Scuseria, and Ernzerhof (HSE) hybrid functional for exchange and correlation. Novel 'perturbation extrapolation' is utilized to extend the use of the computationally expensive HSE functional to this large-scale defect system. According to calculations, the formation energy of charged phosphorus interstitial defects are very low in n-type Zn3P2 and act as 'electron sinks', nullifying the desired doping and lowering the fermi-level back towards the p-type regime. Going forward, this insight provides clues to fabricating useful zinc phosphide based devices. In addition, the methodology developed for this work can be applied to further doping studies in other systems. Accurate determination of high pressure and temperature equations of state is fundamental in a variety of fields. However, it is often very difficult to cover a wide range of temperatures and pressures in an laboratory setting. Here we develop methods to determine a multi-phase equation of state for Ta through computation. The typical means of investigating thermodynamic properties is via 'classical' molecular dynamics where the atomic motion is calculated from Newtonian mechanics with the electronic effects abstracted away into an interatomic potential function. For our purposes, a 'first principles' approach such as DFT is useful as a classical potential is typically valid for only a portion of the phase diagram (i.e. whatever part it has been fit to). Furthermore, for extremes of temperature and pressure quantum effects become critical to accurately capture an equation of state and are very hard to capture in even complex model potentials. This requires extending the inherently zero temperature DFT to predict the finite temperature response of the system. Statistical modelling and thermodynamic integration is used to extend our results over all phases, as well as phase-coexistence regions which are at the limits of typical DFT validity. We deliver the most comprehensive and accurate equation of state that has been done for Ta. This work also lends insights that can be applied to further equation of state work in many other materials.

Humidity-induced room-temperature decomposition of Au contacted indium phosphide

NASA Technical Reports Server (NTRS)

Fatemi, Navid S.; Weizer, Victor G.

1990-01-01

It has been found that Au-contacted InP is chemically unstable at room temperature in a humid ambient due to the leaching action of indium nitrate islands that continually remove In from the contact metallization and thus, in effect, from the Inp substrate. While similar appearing islands form on Au-contacted GaAs, that system appears to be stable since leaching of the group III element does not take place.

Microwave-assisted synthesis of transition metal phosphide

DOEpatents

Viswanathan, Tito

2014-12-30

A method of synthesizing transition metal phosphide. In one embodiment, the method has the steps of preparing a transition metal lignosulfonate, mixing the transition metal lignosulfonate with phosphoric acid to form a mixture, and subjecting the mixture to a microwave radiation for a duration of time effective to obtain a transition metal phosphide.

Particle-Based Simulations of Microscopic Thermal Properties of Confined Systems

DTIC Science & Technology

2014-11-01

velocity versus electric field in gallium arsenide (GaAs) computed with the original CMC table structure (squares) at temperature T=150K, and the new...computer-aided design Cellular Monte Carlo Ensemble Monte Carlo gallium arsenide Heat Transport Equation DARPA Defense Advanced Research Projects

Micro-opto-mechanical devices and systems using epitaxial lift off

NASA Technical Reports Server (NTRS)

Camperi-Ginestet, C.; Kim, Young W.; Wilkinson, S.; Allen, M.; Jokerst, N. M.

1993-01-01

The integration of high quality, single crystal thin film gallium arsenide (GaAs) and indium phosphide (InP) based photonic and electronic materials and devices with host microstructures fabricated from materials such as silicon (Si), glass, and polymers will enable the fabrication of the next generation of micro-opto-mechanical systems (MOMS) and optoelectronic integrated circuits. Thin film semiconductor devices deposited onto arbitrary host substrates and structures create hybrid (more than one material) near-monolithic integrated systems which can be interconnected electrically using standard inexpensive microfabrication techniques such as vacuum metallization and photolithography. These integrated systems take advantage of the optical and electronic properties of compound semiconductor devices while still using host substrate materials such as silicon, polysilicon, glass and polymers in the microstructures. This type of materials optimization for specific tasks creates higher performance systems than those systems which must use trade-offs in device performance to integrate all of the function in a single material system. The low weight of these thin film devices also makes them attractive for integration with micromechanical devices which may have difficulty supporting and translating the full weight of a standard device. These thin film devices and integrated systems will be attractive for applications, however, only when the development of low cost, high yield fabrication and integration techniques makes their use economically feasible. In this paper, we discuss methods for alignment, selective deposition, and interconnection of thin film epitaxial GaAs and InP based devices onto host substrates and host microstructures.

Homoepitaxial growth of β-Ga{sub 2}O{sub 3} thin films by low pressure chemical vapor deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rafique, Subrina; Han, Lu; Zhao, Hongping, E-mail: hongping.zhao@case.edu

2016-05-02

This paper presents the homoepitaxial growth of phase pure (010) β-Ga{sub 2}O{sub 3} thin films on (010) β-Ga{sub 2}O{sub 3} substrate by low pressure chemical vapor deposition. The effects of growth temperature on the surface morphology and crystal quality of the thin films were systematically investigated. The thin films were synthesized using high purity metallic gallium (Ga) and oxygen (O{sub 2}) as precursors for gallium and oxygen, respectively. The surface morphology and structural properties of the thin films were characterized by atomic force microscopy, X-ray diffraction, and high resolution transmission electron microscopy. Material characterization indicates the growth temperature played anmore » important role in controlling both surface morphology and crystal quality of the β-Ga{sub 2}O{sub 3} thin films. The smallest root-mean-square surface roughness of ∼7 nm was for thin films grown at a temperature of 950 °C, whereas the highest growth rate (∼1.3 μm/h) with a fixed oxygen flow rate was obtained for the epitaxial layers grown at 850 °C.« less

Low temperature growth of gallium oxide thin films via plasma enhanced atomic layer deposition.

PubMed

O'Donoghue, Richard; Rechmann, Julian; Aghaee, Morteza; Rogalla, Detlef; Becker, Hans-Werner; Creatore, Mariadriana; Wieck, Andreas Dirk; Devi, Anjana

2017-12-21

Herein we describe an efficient low temperature (60-160 °C) plasma enhanced atomic layer deposition (PEALD) process for gallium oxide (Ga 2 O 3 ) thin films using hexakis(dimethylamido)digallium [Ga(NMe 2 ) 3 ] 2 with oxygen (O 2 ) plasma on Si(100). The use of O 2 plasma was found to have a significant improvement on the growth rate and deposition temperature when compared to former Ga 2 O 3 processes. The process yielded the second highest growth rates (1.5 Å per cycle) in terms of Ga 2 O 3 ALD and the lowest temperature to date for the ALD growth of Ga 2 O 3 and typical ALD characteristics were determined. From in situ quartz crystal microbalance (QCM) studies and ex situ ellipsometry measurements, it was deduced that the process is initially substrate-inhibited. Complementary analytical techniques were employed to investigate the crystallinity (grazing-incidence X-ray diffraction), composition (Rutherford backscattering analysis/nuclear reaction analysis/X-ray photoelectron spectroscopy), morphology (X-ray reflectivity/atomic force microscopy) which revealed the formation of amorphous, homogeneous and nearly stoichiometric Ga 2 O 3 thin films of high purity (carbon and nitrogen <2 at.%) under optimised process conditions. Tauc plots obtained via UV-Vis spectroscopy yielded a band gap of 4.9 eV and the transmittance values were more than 80%. Upon annealing at 1000 °C, the transformation to oxygen rich polycrystalline β-gallium oxide took place, which also resulted in the densification and roughening of the layer, accompanied by a slight reduction in the band gap. This work outlines a fast and efficient method for the low temperature ALD growth of Ga 2 O 3 thin films and provides the means to deposit Ga 2 O 3 upon thermally sensitive polymers like polyethylene terephthalate.

Porous Cobalt Phosphide Polyhedrons with Iron Doping as an Efficient Bifunctional Electrocatalyst.

PubMed

Li, Feng; Bu, Yunfei; Lv, Zijian; Mahmood, Javeed; Han, Gao-Feng; Ahmad, Ishfaq; Kim, Guntae; Zhong, Qin; Baek, Jong-Beom

2017-10-01

Iron (Fe)-doped porous cobalt phosphide polyhedrons are designed and synthesized as an efficient bifunctional electrocatalyst for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The synthesis strategy involves one-step route for doping foreign metallic element and forming porous cobalt phosphide polyhedrons. With varying doping levels of Fe, the optimized Fe-doped porous cobalt phosphide polyhedron exhibits significantly enhanced HER and OER performances, including low onset overpotentials, large current densities, as well as small Tafel slopes and good electrochemical stability during HER and OER. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Aqueous corrosion of phosphide minerals from iron meteorites: a highly reactive source of prebiotic phosphorus on the surface of the early Earth.

PubMed

Pasek, Matthew A; Lauretta, Dante S

2005-08-01

We present the results of an experimental study of aqueous corrosion of Fe-phosphide under conditions relevant to the early Earth. The results strongly suggest that iron meteorites were an important source of reactive phosphorus (P), a requirement for the formation of P-based life. We further demonstrate that iron meteorites were an abundant source of phosphide minerals early in Earth history. Phosphide corrosion was studied in five different solutions: deionized water, deionized water buffered with sodium bicarbonate, deionized water with dissolved magnesium and calcium chlorides, deionized water containing ethanol and acetic acid, and deionized water containing the chlorides, ethanol, and acetic acid. Experiments were performed in the presence of both air and pure Ar gas to evaluate the effect of atmospheric chemistry. Phosphide corrosion in deionized water results in a metastable mixture of mixed-valence, P-bearing ions including pyrophosphate and triphosphate, key components for metabolism in modern life. In a pH-buffered solution of NaHCO(3), the condensed and reduced species diphosphonate is an abundant corrosion product. Corrosion in ethanol- and acetic acid-containing solutions yields additional P-bearing organic molecules, including acetyl phosphonate and a cyclic triphosphorus molecule. Phosphonate is a major corrosion product of all experiments and is the only P-bearing molecule that persists in solutions with high concentrations of magnesium and calcium chlorides, which suggests that phosphonate may have been a primitive oceanic source of P. The stability and reactivity of phosphonate and hypophosphite in solution were investigated to elucidate reaction mechanisms and the role of mineral catalysts on P-solution chemistry. Phosphonate oxidation is rapid in the presence of Fe metal but negligible in the presence of magnetite and in the control sample. The rate of hypophosphite oxidation is independent of reaction substrate.

Influence of different chelators on the radiochemical properties of a 68-Gallium labelled bombesin analogue.

PubMed

Asti, Mattia; Iori, Michele; Capponi, Pier C; Atti, Giulia; Rubagotti, Sara; Martin, René; Brennauer, Albert; Müller, Marco; Bergmann, Ralf; Erba, Paola A; Versari, Annibale

2014-01-01

The radiolabelled bombesin analogue AMBA shows high potential for diagnosis and treatment of prostate and breast cancer, but the influence of different chelators, which differ in terms of radiochemical reactivity and stability, have not been explored so far. In order to find the best suitable chelator for labelling of AMBA, we synthesized AMBA analogues linked to the most commonly used chelators DOTA, NOTA and NODAGA and compared their reactivity and stability after labelling with 68-Gallium. For the synthesis of DO3A-, NO2A- and NODAGA-AMBA, a solid-phase synthesis approach was used. The influence of concentration, pH and temperature on the radiolabelling was analysed. The in vitro stability of all complexes in saline, human serum, human whole blood and against transchelation and transmetallation was analysed. The peptides were synthesised in high yield and purity. Purity and identity of products and impurities were confirmed using UHPLC coupled to ESI-MS. Radiolabelling of these peptides was optimal at elevated temperature, although room temperature labelling was reported previously for NOTA and NODAGA chelators. The highest reactivity was observed for NODAGA-AMBA. On preparation of NO2A-AMBA, the formation of a by-product was detected with HPLC. More detailed analysis revealed the formation of an isomer with the same mass to charge ratio which led to the conclusion that a coordination isomer was formed. All complexes showed high stability in saline, human serum or when challenged with DTPA, transferrin and varying metals (Fe(3+), Cu(2+), Zn(2+)). Conversely, the stability in human blood was low, and varying metabolites were detected and identified by ESI-MS. All three precursors are available in high yields suitable for routine production. NODAGA-AMBA showed the most favoured features when labelled with 68-gallium, but a further comparison in vivo should be performed in order to confirm the superior features found in vitro. © 2013.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moreno, Gilbert

The objective for this project is to develop thermal management strategies to enable efficient and high-temperature wide-bandgap (WBG)-based power electronic systems (e.g., emerging inverter and DC-DC converter). Device- and system-level thermal analyses are conducted to determine the thermal limitations of current automotive power modules under elevated device temperature conditions. Additionally, novel cooling concepts and material selection will be evaluated to enable high-temperature silicon and WBG devices in power electronics components. WBG devices (silicon carbide [SiC], gallium nitride [GaN]) promise to increase efficiency, but will be driven as hard as possible. This creates challenges for thermal management and reliability.

Proceedings 43rd Stanford Geothermal Workshop

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simmons, Stuart; Kirby, Stefan; Verplanck, Philip

Herein we summarize the results of an investigation dealing with the concentrations and inventories of strategic, critical and valuable materials (SCVM) in produced fluids from geothermal and hydrocarbon reservoirs (50-250° C) in Nevada and Utah. Water samples were collected from thirty-four production wells across eight geothermal fields, the Uinta Basin oil/gas province in northeast Utah, and the Covenant oil field in southwestern Utah; additional water samples were collected from six hot springs in the Sevier Thermal Belt in southwestern Utah. Most SCVM concentrations in produced waters range from <0.1 to 100 µg/kg; the main exception is lithium, which has concentrationsmore » that range from <1000 to 25,000 ug/kg. Relatively high concentrations of gallium, germanium, scandium, selenium, and tellurium are measured too. Geothermal waters contain very low concentrations of REEs, below analytical detections limits (0.01 µg/kg), but the concentrations of lanthanum, cerium, and europium range from 0.05 to 5 µg/kg in Uinta basin waters. Among the geothermal fields, the Roosevelt Hot Spring reservoir appears to have the largest inventories of germanium and lithium, and Patua appears to have the largest inventories of gallium, scandium, selenium, and tellurium. By comparison, the Uinta basin has larger inventories of gallium. The concentrations of gallium, germanium, lithium, scandium, selenium, and tellurium in produced waters appear to be partly related to reservoir temperature and concentrations of total dissolved salts. The relatively high concentration and large inventory of lithium occurring at Roosevelt Hot Springs may be related to granitic-gneissic crystalline rocks, which host the reservoir. Analyses of calcite scales from Dixie Valley indicate enrichments in cobalt, gallium, gold, palladium, selenium and tellurium, and these metals appear to be depositing at deep levels in production wells due to boiling. Comparisons with SCVM mineral deposits suggest that brines in sedimentary basins, or derived from lacustrine evaporites, enable aqueous transport of gallium, germanium, and lithium.« less

IM-19: a new flexible microporous gallium based-MOF framework with pressure- and temperature-dependent openings.

PubMed

Chaplais, Gérald; Simon-Masseron, Angélique; Porcher, Florence; Lecomte, Claude; Bazer-Bachi, Delphine; Bats, Nicolas; Patarin, Joël

2009-07-14

Five metal-organic frameworks (MOFs) based on the same three-dimensional gallium terephthalate network (IM-19) are described, and an incommensurate structure (for the as-synthesized form) as well as two remarkable guest-free polymorphs (open and closed) are highlighted.

Experimental analysis and modeling of melt growth processes

NASA Astrophysics Data System (ADS)

Müller, Georg

2002-04-01

Melt growth processes provide the basic crystalline materials for many applications. The research and development of crystal growth processes is therefore driven by the demands which arise from these specific applications; however, common goals include an increased uniformity of the relevant crystal properties at the micro- and macro-scale, a decrease of deleterious crystal defects, and an increase of crystal dimensions. As melt growth equipment and experimentation becomes more and more expensive, little room remains for improvements by trial and error procedures. A more successful strategy is to optimize the crystal growth process by a combined use of experimental process analysis and computer modeling. This will be demonstrated in this paper by several examples from the bulk growth of silicon, gallium arsenide, indium phosphide, and calcium fluoride. These examples also involve the most important melt growth techniques, crystal pulling (Czochralski methods) and vertical gradient freeze (Bridgman-type methods). The power and success of the above optimization strategy, however, is not limited only to the given examples but can be generalized and applied to many types of bulk crystal growth.

Surface plasmon polariton nanocavity with ultrasmall mode volume

NASA Astrophysics Data System (ADS)

Yue, Wencheng; Yao, Peijun; Luo, Huiwen; Liu, Wen

2017-08-01

We present a plasmonic nanocavity structure, consisting of a gallium phosphide (GaP) cylinder penetrating into a rectangular silver plate, and study its properties using a finite element method (FEM). An ultrasmall mode volume of 1.5×10-5[λ_0/(2n)]3 is achieved, which is more than 200 times smaller than the previous ultrasmall mode volume plasmonic nanodisk resonators. Meanwhile, the quality factor of the plasmonic nanocavity is about 38.2 and is over two times greater than the ultrasmall mode volume plasmonic nanodisk resonators. Compared to the aforementioned plasmonic nanodisk resonators, a more than one-order of magnitude larger Purcell factor of 1.2×104 is achieved. We determined the resonant modes of our plasmonic nanocavity are dipolar plasmon modes by analyzing the electric field properties. In addition, we investigate the dependence of the optical properties on the refractive index of the cavity material and discuss the effect of including the silica (SiO2) substrate. Our work provides an alternative approach to achieve ultrasmall plasmonic nanocavity of interest in applications to many areas of research, including device physics, nonlinear optics and quantum optics.

Future Directions for Selected Topics in Physics and Materials Science

DTIC Science & Technology

2012-07-12

referred to as lightides (e.g. borides , nitrides, phosphides) • Materials for energy conversion, energy storage, energy transport and energy production...Distributed nanosystems and sensors • Strategy for multilayered combinatorics • lightides ( borides , nitrides, phosphides, • New applications for...Strategy for multilayered combinatorics Lightides ( borides , nitrides, phosphides) • Energy conversion, .storage and production • Precision control

Improvements in the realization of the ITS-90 over the temperature range from the melting point of gallium to the freezing point of silver at NIM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, J.; Zhang, J. T.; Ping, Q.

2013-09-11

The temperature primary standard over the range from the melting point of gallium to the freezing point of silver in National institute of Metrology (NIM), China, was established in the early 1990s. The performance of all of fixed-point furnaces degraded and needs to be updated due to many years of use. Nowadays, the satisfactory fixed point materials can be available with the development of the modern purification techniques. NIM plans to use a group of three cells for each defining fixed point temperature. In this way the eventual drift of individual cells can be evidenced by periodic intercomparison and thismore » will increase the reliability in disseminating the ITS-90 in China. This article describes the recent improvements in realization of ITS-90 over temperature range from the melting point of gallium to the freezing point of silver at NIM. Taking advantages of the technological advances in the design and manufacture of furnaces, the new three-zone furnaces and the open-type fixed points were developed from the freezing point of indium to the freezing point of silver, and a furnace with the three-zone semiconductor cooling was designed to automatically realize the melting point of gallium. The reproducibility of the new melting point of gallium and the new open-type freezing points of In, Sn, Zn. Al and Ag is improved, especially the freezing points of Al and Ag with the reproducibility of 0.2mK and 0.5mK respectively. The expanded uncertainty in the realization of these defining fixed point temperatures is 0.34mK, 0.44mK, 0.54mK, 0.60mK, 1.30mK and 1.88mK respectively.« less

Quantum size effects in the size-temperature phase diagram of gallium: structural characterization of shape-shifting clusters.

PubMed

Steenbergen, Krista G; Gaston, Nicola

2015-02-09

Finite temperature analysis of cluster structures is used to identify signatures of the low-temperature polymorphs of gallium, based on the results of first-principle Born-Oppenheimer molecular dynamics simulations. Pre-melting structural transitions proceed from either the β- and/or the δ-phase to the γ- or δ-phase, with a size- dependent phase progression. We relate the stability of each isomer to the electronic structures of the different phases, giving new insight into the origin of polymorphism in this complicated element. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reliability of body temperature measurements in hospitalised older patients.

PubMed

Giantin, Valter; Toffanello, Elena D; Enzi, Giuliano; Perissinotto, Egle; Vangelista, Stefania; Simonato, Matteo; Ceccato, Corrado; Manzato, Enzo; Sergi, Giuseppe

2008-06-01

To compare different body temperature assessment methods in older people and to assess the role of cognitive and functional characteristics in temperature recordings. Axillary gallium-in-glass thermometers are commonly used. Their accuracy depends on the proper placement of the device and their permanence in place for eight minutes. With adequate instruction, well-functioning patients can measure their axillary temperature by themselves, while in cognitively and functionally impaired older people, inadequate understanding of instructions and misplacement of the thermometer might determine significant recording errors. Electronic ear and axillary temperature measurements are faster, but their accuracy has not been demonstrated convincingly with older people. Patients (n = 107; aged 65-104 years) were recruited. Barthel Index and Short Portable Mental Status Questionnaire (SPMSQ) scores were obtained for each patient. Temperature readings were obtained using: the axillary gallium-in-glass thermometer, with (T(nurse)) and without (T(self)) the nurse's assistance; the electronic axillary thermometer (T(el)) and the infrared tympanic thermometer (T(tymp)). The T(nurse) was considered as the reference method. Mean difference and standard deviation (mean +/- SD) in temperature recordings between the different techniques and T(nurse) differed significantly from zero for T(self) (-0.40 SD 0.42) and T(tymp) (+0.19 SD 0.48). No significant differences in temperature recordings emerged between T(nurse) and T(el). In simple linear regression models, the difference between T(self) and T(nurse) significantly correlated with age, gender, SPMSQ score and Barthel Index. Multiple linear regression analysis showed an underestimation of body temperature in older patients with cognitive impairments. Unassisted gallium-in-glass axillary temperature assessment is inadequate, in older patients. The differences between T(self) and T(nurse) are significantly influenced by age and mental decline. T(el) provides adequate accuracy. Relevance to clinical practice. In geriatric settings, the electronic axillary thermometer is a safe and accurate alternative to the more traditional gallium-in-glass thermometer, with the advantage of saving time (five seconds in recording vs. eight minutes).

Solvothermal synthesis of gallium-indium-zinc-oxide nanoparticles for electrolyte-gated transistors.

PubMed

Santos, Lídia; Nunes, Daniela; Calmeiro, Tomás; Branquinho, Rita; Salgueiro, Daniela; Barquinha, Pedro; Pereira, Luís; Martins, Rodrigo; Fortunato, Elvira

2015-01-14

Solution-processed field-effect transistors are strategic building blocks when considering low-cost sustainable flexible electronics. Nevertheless, some challenges (e.g., processing temperature, reliability, reproducibility in large areas, and cost effectiveness) are requirements that must be surpassed in order to achieve high-performance transistors. The present work reports electrolyte-gated transistors using as channel layer gallium-indium-zinc-oxide nanoparticles produced by solvothermal synthesis combined with a solid-state electrolyte based on aqueous dispersions of vinyl acetate stabilized with cellulose derivatives, acrylic acid ester in styrene and lithium perchlorate. The devices fabricated using this approach display a ION/IOFF up to 1 × 10(6), threshold voltage (VTh) of 0.3-1.9 V, and mobility up to 1 cm(2)/(V s), as a function of gallium-indium-zinc-oxide ink formulation and two different annealing temperatures. These results validates the usage of electrolyte-gated transistors as a viable and promising alternative for nanoparticle based semiconductor devices as the electrolyte improves the interface and promotes a more efficient step coverage of the channel layer, reducing the operating voltage when compared with conventional dielectrics gating. Moreover, it is shown that by controlling the applied gate potential, the operation mechanism of the electrolyte-gated transistors can be modified from electric double layer to electrochemical doping.

Vapor-solid growth of one-dimensional layer-structured gallium sulfide nanostructures.

PubMed

Shen, Guozhen; Chen, Di; Chen, Po-Chiang; Zhou, Chongwu

2009-05-26

Gallium sulfide (GaS) is a wide direct bandgap semiconductor with uniform layered structure used in photoelectric devices, electrical sensors, and nonlinear optical applications. We report here the controlled synthesis of various high-quality one-dimensional GaS nanostructures (thin nanowires, nanobelts, and zigzag nanobelts) as well as other kinds of GaS products (microbelts, hexagonal microplates, and GaS/Ga(2)O(3) heterostructured nanobelts) via a simple vapor-solid method. The morphology and structures of the products can be easily controlled by substrate temperature and evaporation source. Optical properties of GaS thin nanowires and nanobelts were investigated and both show an emission band centered at 580 nm.

Hierarchical cobalt poly-phosphide hollow spheres as highly active and stable electrocatalysts for hydrogen evolution over a wide pH range

NASA Astrophysics Data System (ADS)

Wu, Tianli; Pi, Mingyu; Wang, Xiaodeng; Guo, Weimeng; Zhang, Dingke; Chen, Shijian

2018-01-01

Exploring highly-efficient and low-cost non-noble metal electrocatalyst toward the hydrogen evolution reaction (HER) is highly desired for renewable energy system but remains challenging. In this work, three dimensional hierarchical porous cobalt poly-phosphide hollow spheres (CoP3 HSs) were prepared by topotactic phosphidation of the cobalt-based precursor via vacuum encapsulation technique. As a porous HER cathode, the CoP3 HSs delivers remarkable electrocatalytic performance over the wide pH range. It needs overpotentials of -69 mV and -118 mV with a small Tafel slope of 51 mV dec-1 to obtain current densities of 10 mA cm-2 and 50 mA cm-2, respectively, and maintains its electrocatalytic performance over 30 h in acidic solution. In addition, CoP3 also exhibit superior electrocatalytic performance and stability under neutral and alkaline conditions for the HER. Both experimental measurements and density functional theory (DFT) calculations are performed to explore the mechanism behind the excellent HER performance. The results of our study make the porous CoP3 HSs as a promising electrocatalyst for practical applications toward energy conversion system and present a new way for designing and fabricating HER electrodes through high degree of phosphorization and nano-porous architecture.

Gallium-doped germanium, evaluation of photoconductors, part 1

NASA Technical Reports Server (NTRS)

Moore, W. J.

1979-01-01

Gallium-doped germanium far infrared detectors were evaluated at low temperatures and low background simulating the space environment. Signal and noise characteristics were determined for detector temperatures in the 2K to 4K range. Optimum performance occurs at about 2.5K for all devices tested. The minimum average NEP in the 40-130 micron region was found to be approximately 4 x 10 to the minus 17th power watt Hz(-1/2) at a frequency of 1 Hz.

Colloidal Cobalt Phosphide Nanocrystals as Trifunctional Electrocatalysts for Overall Water Splitting Powered by a Zinc–Air Battery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Hui; Li, Qi; Wen, Peng

Highly efficient and stable electrocatalysts, particularly those that are capable of multifunctionality in the same electrolyte, are in high demand for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR). In this paper, highly monodisperse CoP and Co 2P nanocrystals (NCs) are synthesized using a robust solution-phase method. The highly exposed (211) crystal plane and abundant surface phosphide atoms make the CoP NCs efficient catalysts toward ORR and HER, while metal-rich Co 2P NCs show higher OER performance owing to easier formation of plentiful Co 2P@COOH heterojunctions. Density functional theory calculation results indicate that themore » desorption of OH* from cobalt sites is the rate-limiting step for both CoP and Co 2P in ORR and that the high content of phosphide can lower the reaction barrier. A water electrolyzer constructed with a CoP NC cathode and a Co 2P NC anode can achieve a current density of 10 mA cm -2 at 1.56 V, comparable even to the noble metal-based Pt/C and RuO 2/C pair. Finally and furthermore, the CoP NCs are employed as an air cathode in a primary zinc–air battery, exhibiting a high power density of 62 mW cm -2 and good stability.« less

Colloidal Cobalt Phosphide Nanocrystals as Trifunctional Electrocatalysts for Overall Water Splitting Powered by a Zinc–Air Battery

DOE PAGES

Li, Hui; Li, Qi; Wen, Peng; ...

2018-01-15

Highly efficient and stable electrocatalysts, particularly those that are capable of multifunctionality in the same electrolyte, are in high demand for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR). In this paper, highly monodisperse CoP and Co 2P nanocrystals (NCs) are synthesized using a robust solution-phase method. The highly exposed (211) crystal plane and abundant surface phosphide atoms make the CoP NCs efficient catalysts toward ORR and HER, while metal-rich Co 2P NCs show higher OER performance owing to easier formation of plentiful Co 2P@COOH heterojunctions. Density functional theory calculation results indicate that themore » desorption of OH* from cobalt sites is the rate-limiting step for both CoP and Co 2P in ORR and that the high content of phosphide can lower the reaction barrier. A water electrolyzer constructed with a CoP NC cathode and a Co 2P NC anode can achieve a current density of 10 mA cm -2 at 1.56 V, comparable even to the noble metal-based Pt/C and RuO 2/C pair. Finally and furthermore, the CoP NCs are employed as an air cathode in a primary zinc–air battery, exhibiting a high power density of 62 mW cm -2 and good stability.« less

Novel, high-activity hydroprocessing catalysts: Iron group phosphides

NASA Astrophysics Data System (ADS)

Wang, Xianqin

A series of iron, cobalt and nickel transition metal phosphides was synthesized by means of temperature-programmed reduction (TPR) of the corresponding phosphates. The same materials, Fe2P, CoP and NO, were also prepared on a silica (SiO2) support. The phase purity of these catalysts was established by x-ray diffraction (XRD), and the surface properties were determined by N2 BET specific surface area (Sg) measurements and CO chemisorption. The activities of the silica-supported catalysts were tested in a three-phase trickle bed reactor for the simultaneous hydrodenitrogenation (HDN) of quinoline and hydrodesulfurization (HDS) of dibenzothiophene using a model liquid feed at realistic conditions (30 atm, 370°C). The reactivity studies showed that the nickel phosphide (Ni2P/SiO2) was the most active of the catalysts. Compared with a commercial Ni-Mo-S/gamma-Al 2O3 catalyst at the same conditions, Ni2P/silica had a substantially higher HDS activity (100% vs. 76%) and HDN activity (82% vs. 38%). Because of their good hydrotreating activity, an extensive study of the preparation of silica supported nickel phosphides, Ni2P/SiO 2, was carried out. The parameters investigated were the phosphorus content and the weight loading of the active phase. The most active composition was found to have a starting synthesis Ni/P ratio close to 1/2, and the best loading of this sample on silica was observed to be 18 wt.%. Extended x-ray absorption fine structure (EXAFS) and x-ray absorption near edge spectroscopy (XANES) measurements were employed to determine the structures of the supported samples. The main phase before and after reaction was found to be Ni2P, but some sulfur was found to be retained after reaction. A comprehensive scrutiny of the HDN reaction mechanism was also made over the Ni2P/SiO2 sample (Ni/P = 1/2) by comparing the HDN activity of a series of piperidine derivatives of different structure. It was found that piperidine adsorption involved an alpha-H activation and nitrogen removal proceeded mainly by means of a beta-H activation though an elimination (E2) mechanism. The relative elimination rates depended on the type and number of beta-hydrogen atoms. Elimination of beta-H atoms attached to tertiary carbon atoms occurred faster than those attached to secondary carbon atoms. Also, the greater the number of the beta-H atoms, the higher the elimination rates. The nature of the adsorbed intermediates was probed by Fourier transform infrared spectroscopy (FTIR) and temperature-programmed desorption (TPD) of the probe molecule, ethylamine. This measurement allowed the determination of the likely steps in the hydrodenitrogenation reaction.

P-type gallium nitride

DOEpatents

Rubin, M.; Newman, N.; Fu, T.; Ross, J.; Chan, J.

1997-08-12

Several methods have been found to make p-type gallium nitride. P-type gallium nitride has long been sought for electronic devices. N-type gallium nitride is readily available. Discovery of p-type gallium nitride and the methods for making it will enable its use in ultraviolet and blue light-emitting diodes and lasers. pGaN will further enable blue photocathode elements to be made. Molecular beam epitaxy on substrates held at the proper temperatures, assisted by a nitrogen beam of the proper energy produced several types of p-type GaN with hole concentrations of about 5{times}10{sup 11} /cm{sup 3} and hole mobilities of about 500 cm{sup 2} /V-sec, measured at 250 K. P-type GaN can be formed of unintentionally-doped material or can be doped with magnesium by diffusion, ion implantation, or co-evaporation. When applicable, the nitrogen can be substituted with other group III elements such as Al. 9 figs.

P-type gallium nitride

DOEpatents

Rubin, Michael; Newman, Nathan; Fu, Tracy; Ross, Jennifer; Chan, James

1997-01-01

Several methods have been found to make p-type gallium nitride. P-type gallium nitride has long been sought for electronic devices. N-type gallium nitride is readily available. Discovery of p-type gallium nitride and the methods for making it will enable its use in ultraviolet and blue light-emitting diodes and lasers. pGaN will further enable blue photocathode elements to be made. Molecular beam epitaxy on substrates held at the proper temperatures, assisted by a nitrogen beam of the proper energy produced several types of p-type GaN with hole concentrations of about 5.times.10.sup.11 /cm.sup.3 and hole mobilities of about 500 cm.sup.2 /V-sec, measured at 250.degree. K. P-type GaN can be formed of unintentionally-doped material or can be doped with magnesium by diffusion, ion implantation, or co-evaporation. When applicable, the nitrogen can be substituted with other group III elements such as Al.

Determination of the electromechanical coupling factor of gallium orthophosphate (GaPO4) and its influence on resonance-frequency temperature dependencies.

PubMed

Nosek, Jaroslav; Pustka, Martin

2006-01-01

The quartz homeotype gallium orthophosphate (GaPO4) is a representative of piezoelectric single crystals of large electromechanical coupling factor. It is known that its coupling factor kappa26 associated with the resonators vibrating in the thickness-shear mode is approximately two times greater than that of quartz. This property increases the spacing between the series and parallel resonance frequencies of resonators, as well as the difference between the resonance frequency temperature dependencies of the fundamental and harmonic resonance frequencies of resonators vibrating in the thickness-shear mode. In this paper, the methods for determination of the coupling factor kappa26 are presented, and the computed values are compared with the measured ones. The influence of the coupling factor to the resonance-frequency temperature dependencies of the fundamental and third harmonics of selected rotated Y-cut GaPO4 resonators vibrating in the thickness-shear mode is presented. The purely elastic case for a laterally unbounded plate, which corresponds closely to the limiting case of high harmonic resonance frequency-temperature behavior was assumed for the calculations. The computed temperature coefficients for the Y-cut orientation and calculated turnover point temperatures TTP for different (YX1) orientations are presented.

High-Efficiency Silicon Carbide (SiC) Converters. Delivery Order 0001: Development of High-Temperature, High-Power, High-Efficiency, High-Voltage Converters Using Silicon Carbide

DTIC Science & Technology

2004-03-01

32 Silicon Dioxide as a Mask ......................................................... 34 Silicon Nitride as a Mask...phosphorous (P), and arsenic (As) for n-type material and aluminum (Al), boron (B), beryllium (Be), gallium (Ga), oxygen (O), and scandium (Sc) for...O2 in carbon tetrafluoride (CF4), nitrogen trifluoride (NF3), and sulfur hexafluoride (SF6) were observed because these gases produce high fluorine

Molecular spectroscopy from 5-12 μm using an OP-GaP OPO

NASA Astrophysics Data System (ADS)

Maidment, Luke; Schunemann, Peter G.; Reid, Derryck T.

2017-02-01

We report a femtosecond optical parametric oscillator (OPO) based on the new semiconductor gain material orientation patterned gallium phosphide (OP-GaP) and being the first example of a broadband OPO operating across the molecular fingerprint region. OP-GaP crystals with lengths of 1 mm and several patterning periods were diced, polished, and antireflection (AR) coated for near- to mid-infrared wavelengths. We configured a synchronously pumped OP-GaP OPO in a 101.2-MHz resonator with high reflectivity from 1.15-1.35 μm, pumped with 150-fs pulses from a 1040-nm femtosecond laser (Chromacity Spark). The coating of one spherical mirror was optimized for transmission at the pump wavelength of 1040 nm and for high reflectivity at the resonant signal wavelength in a range from 1.15-1.35 μm, while the other spherical mirror collimated the idler beam emerging from the OP-GaP crystal and was silver coated to provide high reflectivity for all idler wavelengths. This collimated idler beam was output-coupled from the cavity by transmission through a plane mirror coated with high transmission for the idler wavelengths (5-12 μm) and high reflectivity for the signal wavelengths (1.15-1.35 μm) on an infrared-transparent ZnSe substrate. Idler spectra centered from 5.4-11.8 μm and extending to 12.5 μm were collected. The maximum average power was 55 mW at 5.4 μm with 7.5 mW being recorded at 11.8 μm. Details of Fourier transform spectroscopy using water vapor and a polystyrene reference standard are presented.

Investigation of Gate-Stacked In-Ga-Zn-O TFTs with Ga-Zn-O Source/Drain Electrodes by Atmospheric Pressure Plasma-Enhanced Chemical Vapor Deposition.

PubMed

Wu, Chien-Hung; Chang, Kow-Ming; Chen, Yi-Ming; Huang, Bo-Wen; Zhang, Yu-Xin; Wang, Shui-Jinn; Hsu, Jui-Mei

2018-03-01

Atmospheric pressure plasma-enhanced chemical vapor deposition (AP-PECVD) was employed for the fabrication of indium gallium zinc oxide thin-film transistors (IGZO TFTs) with high transparent gallium zinc oxide (GZO) source/drain electrodes. The influence of post-deposition annealing (PDA) temperature on GZO source/drain and device performance was studied. Device with a 300 °C annealing demonstrated excellent electrical characteristics with on/off current ratio of 2.13 × 108, saturation mobility of 10 cm2/V-s, and low subthreshold swing of 0.2 V/dec. The gate stacked LaAlO3/ZrO2 of AP-IGZO TFTs with highly transparent and conductive AP-GZO source/drain electrode show excellent gate control ability at a low operating voltage.

1.55 Micrometer Sub-Micron Finger, Interdigitated MSM Photodetector Arrays with Low Dark Current

DTIC Science & Technology

2010-02-02

pf a- IGZO TFTs. IV. RF Characteristics of Room Temperature Deposited Indium Zinc Oxide Thin - Film Transistors Depletion-mode indium zinc...III. High Performance Indium Gallium Zinc Oxide Thin Film Transistors Fabricated On Polyethylene Terephthalate Substrates High-performance...amorphous (a-) InGaZnO-based thin film transistors (TFTs) were fabricated on flexible polyethylene terephthalate (PET) substrates coated with indium

Innovative Surfaces for Controlled Flow of Liquid Metal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fortini, Arthur J.

2016-03-22

The potential economic, environmental, and strategic benefits associated with the development of fusion energy are numerous. However, application of fusion technology cannot be realized until advanced materials are developed that allow operation under the high heat flux conditions necessary for cost-competitive electric energy generation. Bathing the wall of a fusion reactor plasma-facing component in a liquid metal such as lithium, gallium, or tin is a viable approach for accommodating continuous heat flux levels exceeding 10 MW/m2, and it is also the preferred approach for removing hydrogen isotopes. Stabilizing the liquid film is the key challenge, which can be addressed throughmore » the use of a microtextured surface. In previous work, Ultramet developed high temperature microtextured tungsten and rhenium coatings consisting of thousands of high aspect ratio pyramids per square millimeter that are compatible with lithium, gallium, and tin, and whose effectiveness in wicking molten lithium has been demonstrated even in the presence of strong body forces. Heat transfer and fluid flow characteristics were also modeled. Because of the safety issues surrounding lithium, the current project focused on adapting and optimizing this wicking technology for use with gallium and tin. The coatings were deposited by chemical vapor deposition (CVD), and the height, population density, and morphology of the pyramids was varied to optimize the wetting properties, which were measured and quantified by exposing the coatings to molten gallium or tin. Micron-thick films of other materials were also applied to the textured surfaces to vary the wetting characteristics. Wicking tests were performed with both gallium and tin on a variety of coatings with different textures and surface chemistries, and both metals showed excellent wicking and wettability on virtually all of the textured coatings. Extensive modeling of the interaction between the dendrites and the liquid metal, as well as additional wetting testing, was performed by Digital Materials Solutions (DMS, Carlsbad, CA).« less

Hydrothermal Synthesis and Photocatalytic Property of β-Ga2O3 Nanorods

NASA Astrophysics Data System (ADS)

Reddy, L. Sivananda; Ko, Yeong Hwan; Yu, Jae Su

2015-09-01

Gallium oxide (Ga2O3) nanorods were facilely prepared by a simple hydrothermal synthesis, and their morphology and photocatalytic property were studied. The gallium oxide hydroxide (GaOOH) nanorods were formed in aqueous growth solution containing gallium nitrate and ammonium hydroxide at 95 °C of growth temperature. Through the calcination treatment at 500 and 1000 °C for 3 h, the GaOOH nanorods were converted into single crystalline α-Ga2O3 and β-Ga2O3 phases. From X-ray diffraction analysis, it could be confirmed that a high crystalline quality of β-Ga2O3 nanorods was achieved by calcinating at 1000 °C. The thermal behavior of the Ga2O3 nanorods was also investigated by differential thermal analysis, and their vibrational bands were identified by Fourier transform infrared spectroscopy. In order to examine the photocatalytic activity of samples, the photodegradation of Rhodamine B solution was observed under UV light irradiation. As a result, the α-Ga2O3 and β-Ga2O3 nanorods exhibited high photodegeneration efficiencies of 62 and 79 %, respectively, for 180 min of UV irradiation time.

Hydrothermal Synthesis and Photocatalytic Property of β-Ga2O3 Nanorods.

PubMed

Reddy, L Sivananda; Ko, Yeong Hwan; Yu, Jae Su

2015-12-01

Gallium oxide (Ga2O3) nanorods were facilely prepared by a simple hydrothermal synthesis, and their morphology and photocatalytic property were studied. The gallium oxide hydroxide (GaOOH) nanorods were formed in aqueous growth solution containing gallium nitrate and ammonium hydroxide at 95 °C of growth temperature. Through the calcination treatment at 500 and 1000 °C for 3 h, the GaOOH nanorods were converted into single crystalline α-Ga2O3 and β-Ga2O3 phases. From X-ray diffraction analysis, it could be confirmed that a high crystalline quality of β-Ga2O3 nanorods was achieved by calcinating at 1000 °C. The thermal behavior of the Ga2O3 nanorods was also investigated by differential thermal analysis, and their vibrational bands were identified by Fourier transform infrared spectroscopy. In order to examine the photocatalytic activity of samples, the photodegradation of Rhodamine B solution was observed under UV light irradiation. As a result, the α-Ga2O3 and β-Ga2O3 nanorods exhibited high photodegeneration efficiencies of 62 and 79 %, respectively, for 180 min of UV irradiation time.

Integration of Indium Phosphide Based Devices with Flexible Substrates

NASA Astrophysics Data System (ADS)

Chen, Wayne Huai

2011-12-01

Flexible substrates have many advantages in applications where bendability, space, or weight play important roles or where rigid circuits are undesirable. However, conventional flexible thin film transistors are typically characterized as having low carrier mobility as compared to devices used in the electronics industry. This is in part due to the limited temperature tolerance of plastic flexible substrates, which commonly reduces the highest processing temperature to below 200°C. Common approaches of implementation include low temperature deposition of organic, amorphous, or polycrystalline semiconductors, all of which result in carrier mobility well below 100 cm2V -1s-1. High quality, single crystalline III-V semiconductors such as indium phosphide (InP), on the other hand, have carrier mobility well over 1000 cm 2V-1s-1 at room temperature, depending on carrier concentration. Recently, the ion-cut process has been used in conjunction with wafer bonding to integrate thin layers of III-V material onto silicon for optoelectronic applications. This approach has the advantage of high scalability, reusability of the initial III-V substrate, and the ability to tailor the location (depth) of the layer splitting. However, the transferred substrate usually suffers from hydrogen implantation damage. This dissertation demonstrates a new approach to enable integration of InP with various substrates, called the double-flip transfer process. The process combines ion-cutting with adhesive bonding. The problem of hydrogen implantation was overcome by patterned ion-cut transfer. In this type of transfer, areas of interest are shielded from implantation but still transferred by surrounding implanted regions. We found that patterned ion-cut transfer is strongly dependent upon crystal orientation and that using cleavage-plane oriented donors can be beneficial in transferring large areas of high quality semiconductor material. InP-based devices were fabricated to demonstrate the transfer process and test functionality following transfer. Passive devices (photodetectors) as well as active transistors were transferred and fabricated on various substrates. The transferred device layers were either implanted through with a blanket implant or protected with an ion-mask during implantation. Results demonstrate the viability of the double-flip ion-cut process in achieving very high electron mobility (˜2800 cm2V-1s-1) transistors on plastic flexible substrates.

Gallium oxide thin films from the AACVD of [Ga(NMe2)3]2 and donor functionalised alcohols.

PubMed

Basharat, Siama; Carmalt, Claire J; Binions, Russell; Palgrave, Robert; Parkin, Ivan P

2008-02-07

Thin films of Ga(2)O(3) have been produced from [Ga(NMe(2))(3)](2) and ROH (R = CH(2)CH(2)NMe(2), CH(CH(2)NMe(2))(2), CH(CH(3))CH(2)NMe(2), CH(2)CH(2)OMe and C(CH(3))(2)CH(2)OMe) by aerosol assisted chemical vapour deposition on glass. Transparent, unreflective films were obtained at a deposition temperature of 550 degrees C using toluene as solvent. The gallium oxide films were analyzed by Scanning electron microscopy (SEM), Raman spectroscopy, wavelength dispersive analysis of X-rays (WDX) and X-ray photoelectron spectroscopy (XPS). The gallium oxide films obtained were X-ray amorphous. Gas-sensing experiments indicated that the films showed an n-type response to ethanol at a variety of temperatures.

Effect of gallium alloying on the structure, the phase composition, and the thermoelastic martensitic transformations in ternary Ni-Mn-Ga alloys

NASA Astrophysics Data System (ADS)

Belosludtseva, E. S.; Kuranova, N. N.; Marchenkova, E. B.; Popov, A. G.; Pushin, V. G.

2016-04-01

The effect of gallium alloying on the structure, the phase composition, and the properties of quasibinary Ni50Mn50- z Ga z (0 ⩽ z ⩽ 25 at %) alloys is studied over a wide temperature range. The influence of the alloy composition on the type of crystal structure in high-temperature austenite and martensite and the critical martensitic transformation temperatures is analyzed. A general phase diagram of the magnetic and structural transformations in the alloys is plotted. The temperature-concentration boundaries of the B2 and L21 superstructures in the austenite field, the tetragonal L10 (2 M) martensite, and the 10 M and 14 M martensite phases with complex multilayer crystal lattices are found. The predominant morphology of martensite is shown to be determined by the hierarchy of the packets of thin coherent lamellae of nano- and submicrocrystalline crystals with planar habit plane boundaries close to {011} B2. Martensite crystals are twinned along one of the 24 24{ {011} }{< {01bar 1} rangle _{B2}} "soft" twinning shear systems, which provides coherent accommodation of the martensitic transformation-induced elastic stresses.

Microwave Integrated Circuit Amplifier Designs Submitted to Qorvo for Fabrication with 0.09-micron High Electron Mobility Transistors (HEMTs) using 2-mil Gallium Nitride (GaN) on Silicon Carbide (SiC)

DTIC Science & Technology

2016-03-01

Fabrication with 0.09-µm High-Electron-Mobility Transistors (HEMTs) Using 2-mil Gallium Nitride (GaN) on Silicon Carbide (SiC) by John E Penn...for Fabrication with 0.09-µm High-Electron-Mobility Transistors (HEMTs) using 2-mil Gallium Nitride (GaN) on Silicon Carbide by John E Penn...µm High-Electron-Mobility Transistors (HEMTs) using 2-mil Gallium Nitride (GaN) on Silicon Carbide 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c

Strongly-guided indium phosphide/indium gallium arsenic phosphide Mach-Zehnder modulator for optical communications

NASA Astrophysics Data System (ADS)

Betty, Ian Brian

2006-12-01

The development of strongly-guided InP/In1-x GaxAsyP 1-y based Mach-Zehnder optical modulators for 10Gb/s telecommunications is detailed. The modulators have insertion losses including coupling as low as 4.5dB, due to the incorporation of monolithically integrated optical mode spot-size converters (SSC's). The modulators are optimized to produce system performance that is independent of optical coupling alignment and for wavelength operation between 1525nm and 1565nm. A negatively chirped Mach-Zehnder modulator design is demonstrated, giving optimal dispersion-limited reach for 10Gb/s ON/OFF-keying modulation. It is shown that the optical system performance for this design can be determined from purely DC based optical measurements. A Mach-Zehnder modulator design invoking nearly no transient frequency shifts under intensity modulation is also presented, for the first time, using phase-shifter implementations based on the Quantum-Confined-Stark-Effect (QCSE). The performance impact on the modulator from the higher-order vertical and lateral waveguide modes found in strongly-guided waveguides has been determined. The impact of these higher-order modes has been minimized using the design of the waveguide bends, MMI structures, and doping profiles. The fabrication process and optical design for the spot-size mode converters are also thoroughly explored. The SSC structures are based on butt-joined vertically tapered passive waveguide cores within laterally flared strongly-guided ridges, making them compatible with any strong-guiding waveguide structure. The flexibility of the SSC process is demonstrated by the superior performance it has also enabled in a 40Gb/s electro-absorption modulator. The presented electro-absorption modulator has 3.6dB fiber-to-fiber insertion loss, polarization dependent loss (PDL) of only 0.3dB over 15dB extinction, and low absolute chirp (|alpha H| < 0.6) over the full dynamic range.

Atomistic investigations on the mechanical properties and fracture mechanisms of indium phosphide nanowires.

PubMed

Pial, Turash Haque; Rakib, Tawfiqur; Mojumder, Satyajit; Motalab, Mohammad; Akanda, M A Salam

2018-03-28

The mechanical properties of indium phosphide (InP) nanowires are an emerging issue due to the promising applications of these nanowires in nanoelectromechanical and microelectromechanical devices. In this study, molecular dynamics simulations of zincblende (ZB) and wurtzite (WZ) crystal structured InP nanowires (NWs) are presented under uniaxial tension at varying sizes and temperatures. It is observed that the tensile strengths of both types of NWs show inverse relationships with temperature, but are independent of the size of the nanowires. Moreover, applied load causes brittle fracture by nucleating cleavage on ZB and WZ NWs. When the tensile load is applied along the [001] direction, the direction of the cleavage planes of ZB NWs changes with temperature. It is found that the {111} planes are the cleavage planes at lower temperatures; on the other hand, the {110} cleavage planes are activated at elevated temperatures. In the case of WZ NWs, fracture of the material is observed to occur by cleaving along the (0001) plane irrespective of temperature when the tensile load is applied along the [0001] direction. Furthermore, the WZ NWs of InP show considerably higher strength than their ZB counterparts. Finally, the impact of strain rate on the failure behavior of InP NWs is also studied, and higher fracture strengths and strains at higher strain rates are found. With increasing strain rate, the number of cleavages also increases in the NWs. This paper also provides in-depth understanding of the failure behavior of InP NWs, which will aid the design of efficient InP NWs-based devices.

Novel p-n heterojunction copper phosphide/cuprous oxide photocathode for solar hydrogen production.

PubMed

Chen, Ying-Chu; Chen, Zhong-Bo; Hsu, Yu-Kuei

2018-08-01

A Copper phosphide (Cu 3 P) micro-rod (MR) array, with coverage by an n-Cu 2 O thin layer by electrodeposition as a photocathode, has been directly fabricated on copper foil via simple electro-oxidation and phosphidation for photoelectrochemical (PEC) hydrogen production. The morphology, structure, and composition of the Cu 3 P/Cu 2 O heterostructure are systematically analyzed using a scanning electron microscope (SEM), X-ray diffraction and X-ray photoelectron spectra. The PEC measurements corroborate that the p-Cu 3 P/n-Cu 2 O heterostructural photocathode illustrates efficient charge separation and low charge transfer resistance to achieve the highest photocurrent of 430 μA cm -2 that is greater than other transition metal phosphide materials. In addition, a detailed energy diagram of the p-Cu 3 P/n-Cu 2 O heterostructure was investigated using Mott-Schottky analysis. Our study paves the way to explore phosphide-based materials in a new class for solar energy applications. Copyright © 2018 Elsevier Inc. All rights reserved.

Thin boron phosphide coating as a corrosion-resistant layer

DOEpatents

Not Available

1982-08-25

A surface prone to corrosion in corrosive environments is rendered anticorrosive by CVD growing a thin continuous film, e.g., having no detectable pinholes, thereon, of boron phosphide. In one embodiment, the film is semiconductive. In another aspect, the invention is an improved photoanode, and/or photoelectrochemical cell with a photoanode having a thin film of boron phosphide thereon rendering it anticorrosive, and providing it with unexpectedly improved photoresponsive properties.

Recent developments in indium phosphide space solar cell research

NASA Technical Reports Server (NTRS)

Brinker, David J.; Weinberg, Irving

1987-01-01

Recent developments and progress in indium phosphide solar cell research for space application are reviewed. Indium phosphide homojunction cells were fabricated in both the n+p and p+n configurations with total area efficiencies of 17.9 and 15.9% (air mass 0 and 25 C) respectively. Organometallic chemical vapor deposition, liquid phase epitaxy, ion implantation and diffusion techniques were employed in InP cell fabrication. A theoretical model of a radiation tolerant, high efficiency homojunction cell was developed. A realistically attainable AMO efficiency of 20.5% was calculated using this model with emitter and base doping of 6 x 10 to the 17th power and 5 x 10 the the 16th power/cu cm respectively. Cells of both configurations were irradiated with 1 MeV electrons and 37 MeV protons. For both proton and electron irradiation, the n+p cells are more radiation resistant at higher fluences than the p+n cells. The first flight module of four InP cells was assembled for the Living Plume Shield III satellite.

Intentional fatal metallic phosphide poisoning in a dog--a case report.

PubMed

Nagy, Andras-Laszlo; Bolfa, Pompei; Mihaiu, Marian; Catoi, Cornel; Oros, Adrian; Taulescu, Marian; Tabaran, Flaviu

2015-07-23

Metallic phosphides are extremely toxic pesticides that are regulated in their usage. Information concerning the impact of metallic phosphides on human health is abundant. Data regarding the clinical pathology of phosphide poisoning in humans or domestic and wild animals is largely incomplete with only a few cases of metallic phosphide poisoning being reported every year, especially in humans. For the majority of cases reported in dogs the data are vague or incomplete. Here we report a complete and detailed description of pathological changes in a case of intentional metallic phosphide poisoning in a dog including an exhaustive examination of the brain. A 1 year old, male, Belgian Shepherd crossbreed dog with a clean medical history and no observed clinical signs prior to death, was submitted for post mortem examination. The dog was found dead by the owner. Near the body a suspect mix of bread, fat and a blackish powder was found. The owner announced the authorities and submitted the animal and the possible bait for forensic examination. At necropsy, multisystemic necrotic and degenerative lesions were observed. Histological exam confirmed the presence of necrotic and degenerative lesions of variable severity in all of the examined organs. The toxicological forensic examination revealed the presence of the phosphine gas in the gastric content and the bait. Metallic phosphide poisoning is a rarely reported entity, since the diagnosis of intentional poisoning with these compounds is a great challenge for forensic pathologists and toxicologists. To our knowledge, this is the first study describing the lesions completely in veterinary forensic toxicology. We assume that the toxic shows systemic endotheliotropism and damage of the endothelial cells responsible for the hemorrhagic lesions and for the secondary ischemic necrosis in various organs. This report will contribute to a better understanding of the pathogenesis in cases of acute metallic phosphide exposure in animals.

General One-Pot Synthesis of Transition-Metal Phosphide/Nitrogen-Doped Carbon Hybrid Nanosheets as Ultrastable Anodes for Sodium-Ion Batteries.

PubMed

Li, Jingjing; Shi, Liang; Gao, Jingyu; Zhang, Genqiang

2018-01-26

Sodium-ion batteries (SIBs) have been considered as promising energy storage devices in grid-level applications, owing to their largely reduced cost compared with that of lithium-ion batteries. However, the practical application of SIBs has been seriously hindered because of the lack of appropriate anode materials, limited by the thermodynamics perspective, which is one of the central task at current stage. Herein, we have developed a general one-pot strategy for the synthesis of transition-metal phosphide (TMP) based hybrid nanosheets composed of carbon-coated TMP nanoparticles anchored to the surface of nitrogen-doped carbon nanosheets. This facile and cost-effective method is quite universal and holds potential to be further extended to other metal phosphide materials. Significantly, the hybrid nanosheet electrode possesses excellent sodium storage properties as anodes for SIBs, including high specific capacity, an ultra-long cycle life and a remarkable rate performance. This work makes a significant contribution to not only the synthetic methodology of TMP-carbon two-dimensional hybrid nanostructures, but also the application of TMP-based anodes for high-energy SIBs. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Multiferroic GaN nanofilms grown within Na-4 mica channels

NASA Astrophysics Data System (ADS)

Bhattacharya, Santanu; Datta, A.; Chakravorty, D.

2010-03-01

Gallium nitride nanofilms grown within nanochannels of Na-4 mica structure, exhibit ferromagnetism even at room temperature due to the presence of gallium vacancies at the surfaces of the nanofilms. These nanofilms also show a ferroelectric behavior at room temperature ascribed to a small distortion in the crystal structure of GaN due to its growth within the Na-4 mica nanochannels. A colossal increase in 338% in dielectric constant was observed for an applied magnetic field of 26 kOe. The magnetoelectric effect is ascribed to magnetostriction of magnetic GaN phase.

Semiconductor to metallic transition in bulk accumulated amorphous indium-gallium-zinc-oxide dual gate thin-film transistor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chun, Minkyu; Chowdhury, Md Delwar Hossain; Jang, Jin, E-mail: jjang@khu.ac.kr

We investigated the effects of top gate voltage (V{sub TG}) and temperature (in the range of 25 to 70 {sup o}C) on dual-gate (DG) back-channel-etched (BCE) amorphous-indium-gallium-zinc-oxide (a-IGZO) thin film transistors (TFTs) characteristics. The increment of V{sub TG} from -20V to +20V, decreases the threshold voltage (V{sub TH}) from 19.6V to 3.8V and increases the electron density to 8.8 x 10{sup 18}cm{sup −3}. Temperature dependent field-effect mobility in saturation regime, extracted from bottom gate sweep, show a critical dependency on V{sub TG}. At V{sub TG} of 20V, the mobility decreases from 19.1 to 15.4 cm{sup 2}/V ⋅ s with increasingmore » temperature, showing a metallic conduction. On the other hand, at V{sub TG} of - 20V, the mobility increases from 6.4 to 7.5cm{sup 2}/V ⋅ s with increasing temperature. Since the top gate bias controls the position of Fermi level, the temperature dependent mobility shows metallic conduction when the Fermi level is above the conduction band edge, by applying high positive bias to the top gate.« less

CVD growth and properties of boron phosphide on 3C-SiC

NASA Astrophysics Data System (ADS)

Padavala, Balabalaji; Frye, C. D.; Wang, Xuejing; Raghothamachar, Balaji; Edgar, J. H.

2016-09-01

Improving the crystalline quality of boron phosphide (BP) is essential for realizing its full potential in semiconductor device applications. In this study, 3C-SiC was tested as a substrate for BP epitaxy. BP films were grown on 3C-SiC(100)/Si, 3C-SiC(111)/Si, and 3C-SiC(111)/4H-SiC(0001) substrates in a horizontal chemical vapor deposition (CVD) system. Films were produced with good crystalline orientation and morphological features in the temperature range of 1000-1200 °C using a PH3+B2H6+H2 mixture. Rotational twinning was absent in the BP due to the crystal symmetry-matching with 3C-SiC. Confocal 3D Raman imaging of BP films revealed primarily uniform peak shift and peak widths across the scanned area, except at defects on the surface. Synchrotron white beam X-ray topography showed the epitaxial relationship between BP and 3C-SiC was (100) 〈 011 〉 BP||(100) 〈 011 〉 3C-SiC and (111) 〈 11 2 ̅ 〉 BP||(111) 〈 11 2 ̅ 〉 3C-SiC. Scanning electron microscopy, Raman spectroscopy and X-ray diffraction analysis indicated residual tensile strain in the films and improved crystalline quality at temperatures below 1200 °C. These results indicated that BP properties could be further enhanced by employing high quality bulk 3C-SiC or 3C-SiC epilayers on 4H-SiC substrates.

CVD growth and properties of boron phosphide on 3C-SiC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Padavala, Balabalaji; Frye, C. D.; Wang, Xuejing

Improving the crystalline quality of boron phosphide (BP) is essential for realizing its full potential in semiconductor device applications. In this study, 3C-SiC was tested as a substrate for BP epitaxy. BP films were grown on 3C-SiC(100)/Si, 3C-SiC(111)/Si, and 3C-SiC(111)/4H-SiC(0001) substrates in a horizontal chemical vapor deposition (CVD) system. Films were produced with good crystalline orientation and morphological features in the temperature range of 1000–1200 °C using a PH3+B2H6+H2 mixture. Rotational twinning was absent in the BP due to the crystal symmetry-matching with 3C-SiC. Confocal 3D Raman imaging of BP films revealed primarily uniform peak shift and peak widths acrossmore » the scanned area, except at defects on the surface. Synchrotron white beam X-ray topography showed the epitaxial relationship between BP and 3C-SiC was (100) <011>BP||(100) <011>3C-SiC and (111)View the MathML sourceBP||(111)View the MathML source3C-SiC. Scanning electron microscopy, Raman spectroscopy and X-ray diffraction analysis indicated residual tensile strain in the films and improved crystalline quality at temperatures below 1200 °C. These results indicated that BP properties could be further enhanced by employing high quality bulk 3C-SiC or 3C-SiC epilayers on 4H-SiC substrates.« less

High Performance, Low Temperature Solution-Processed Barium and Strontium Doped Oxide Thin Film Transistors.

PubMed

Banger, Kulbinder K; Peterson, Rebecca L; Mori, Kiyotaka; Yamashita, Yoshihisa; Leedham, Timothy; Sirringhaus, Henning

2014-01-28

Amorphous mixed metal oxides are emerging as high performance semiconductors for thin film transistor (TFT) applications, with indium gallium zinc oxide, InGaZnO (IGZO), being one of the most widely studied and best performing systems. Here, we investigate alkaline earth (barium or strontium) doped InBa(Sr)ZnO as alternative, semiconducting channel layers and compare their performance of the electrical stress stability with IGZO. In films fabricated by solution-processing from metal alkoxide precursors and annealed to 450 °C we achieve high field-effect electron mobility up to 26 cm 2 V -1 s -1 . We show that it is possible to solution-process these materials at low process temperature (225-200 °C yielding mobilities up to 4.4 cm 2 V -1 s -1 ) and demonstrate a facile "ink-on-demand" process for these materials which utilizes the alcoholysis reaction of alkyl metal precursors to negate the need for complex synthesis and purification protocols. Electrical bias stress measurements which can serve as a figure of merit for performance stability for a TFT device reveal Sr- and Ba-doped semiconductors to exhibit enhanced electrical stability and reduced threshold voltage shift compared to IGZO irrespective of the process temperature and preparation method. This enhancement in stability can be attributed to the higher Gibbs energy of oxidation of barium and strontium compared to gallium.

High Performance, Low Temperature Solution-Processed Barium and Strontium Doped Oxide Thin Film Transistors

PubMed Central

2013-01-01

Amorphous mixed metal oxides are emerging as high performance semiconductors for thin film transistor (TFT) applications, with indium gallium zinc oxide, InGaZnO (IGZO), being one of the most widely studied and best performing systems. Here, we investigate alkaline earth (barium or strontium) doped InBa(Sr)ZnO as alternative, semiconducting channel layers and compare their performance of the electrical stress stability with IGZO. In films fabricated by solution-processing from metal alkoxide precursors and annealed to 450 °C we achieve high field-effect electron mobility up to 26 cm2 V–1 s–1. We show that it is possible to solution-process these materials at low process temperature (225–200 °C yielding mobilities up to 4.4 cm2 V–1 s–1) and demonstrate a facile “ink-on-demand” process for these materials which utilizes the alcoholysis reaction of alkyl metal precursors to negate the need for complex synthesis and purification protocols. Electrical bias stress measurements which can serve as a figure of merit for performance stability for a TFT device reveal Sr- and Ba-doped semiconductors to exhibit enhanced electrical stability and reduced threshold voltage shift compared to IGZO irrespective of the process temperature and preparation method. This enhancement in stability can be attributed to the higher Gibbs energy of oxidation of barium and strontium compared to gallium. PMID:24511184

Complete Stokes polarimetry of magneto-optical Faraday effect in a terbium gallium garnet crystal at cryogenic temperatures.

PubMed

Majeed, Hassaan; Shaheen, Amrozia; Anwar, Muhammad Sabieh

2013-10-21

We report the complete determination of the polarization changes caused in linearly polarized incident light due to propagation in a magneto-optically active terbium gallium garnet (TGG) single crystal, at temperatures ranging from 6.3 to 300 K. A 28-fold increase in the Verdet constant of the TGG crystal is seen as its temperature decreases to 6.3 K. In contrast with polarimetry of light emerging from a Faraday material at room temperature, polarimetry at cryogenic temperatures cannot be carried out using the conventional fixed polarizer-analyzer technique because the assumption that ellipticity is negligible becomes increasingly invalid as temperature is lowered. It is shown that complete determination of light polarization in such a case requires the determination of its Stokes parameters, otherwise inaccurate measurements will result with negative implications for practical devices.

Method of making V.sub.3 Ga superconductors

DOEpatents

Dew-Hughes, David

1980-01-01

An improved method for producing a vanadium-gallium superconductor wire having aluminum as a component thereof is disclosed, said wire being encased in a gallium bearing copper sheath. The superconductors disclosed herein may be fabricated under normal atmospheres and room temperatures by forming a tubular shaped billet having a core composed of an alloy of vanadium and aluminum and an outer sheath composed of an alloy of copper, gallium and aluminum. Thereafter the entire billet is swage reduced to form a wire therefrom and heat treated to form a layer of V.sub.3 Ga in the interior of the wire.

Optimized Spiral Metal-Gallium-Nitride Nanowire Cavity for Ultra-High Circular Dichroism Ultraviolet Lasing at Room Temperature.

PubMed

Liao, Wei-Chun; Liao, Shu-Wei; Chen, Kuo-Ju; Hsiao, Yu-Hao; Chang, Shu-Wei; Kuo, Hao-Chung; Shih, Min-Hsiung

2016-05-25

Circularly polarized laser sources with small footprints and high efficiencies can possess advanced functionalities in optical communication and biophotonic integrated systems. However, the conventional lasers with additional circular-polarization converters are bulky and hardly compatible with nanophotonic circuits, and most active chiral plasmonic nanostructures nowadays exhibit broadband emission and low circular dichroism. In this work, with spirals of gallium nitride (GaN) nanowires (NWRs) covered by a metal layer, we demonstrated an ultrasmall semiconductor laser capable of emitting circularly-polarized photons. The left- and right-hand spiral metal nanowire cavities with varied periods were designed at ultraviolet wavelengths to achieve the high quality factor circular dichroism metastructures. The dissymmetry factors characterizing the degrees of circular polarizations of the left- and right-hand chiral lasers were 1.4 and -1.6 (±2 if perfectly circular polarized), respectively. The results show that the chiral cavities with only 5 spiral periods can achieve lasing signals with the high degrees of circular polarizations.

Construction of an electrode modified with gallium(III) for voltammetric detection of ovalbumin.

PubMed

Sugawara, Kazuharu; Okusawa, Makoto; Takano, Yusaku; Kadoya, Toshihiko

2014-01-01

Electrodes modified with gallium(III) complexes were constructed to detect ovalbumin (OVA). For immobilization of a gallium(III)-nitrilotriacetate (NTA) complex, the electrode was first covered with collagen film. After the amino groups of the film had reacted with isothiocyanobenzyl-NTA, the gallium(III) was then able to combine with the NTA moieties. Another design featured an electrode cast with a gallium(III)-acetylacetonate (AA) complex. The amount of gallium(III) in the NTA complex was equivalent to one-quarter of the gallium(III) that could be utilized from an AA complex. However, the calibration curves of OVA using gallium(III)-NTA and gallium(III)-AA complexes were linear in the ranges of 7.0 × 10(-11) - 3.0 × 10(-9) M and 5.0 × 10(-10) - 8.0 × 10(-9) M, respectively. The gallium(III) on the electrode with NTA complex had high flexibility due to the existence of a spacer between the NTA and the collagen film, and, therefore, the reactivity of the gallium(III) to OVA was superior to that of the gallium(III)-AA complex with no spacer.

Method of synthesizing bulk transition metal carbide, nitride and phosphide catalysts

DOEpatents

Choi, Jae Soon; Armstrong, Beth L; Schwartz, Viviane

2015-04-21

A method for synthesizing catalyst beads of bulk transmission metal carbides, nitrides and phosphides is provided. The method includes providing an aqueous suspension of transition metal oxide particles in a gel forming base, dropping the suspension into an aqueous solution to form a gel bead matrix, heating the bead to remove the binder, and carburizing, nitriding or phosphiding the bead to form a transition metal carbide, nitride, or phosphide catalyst bead. The method can be tuned for control of porosity, mechanical strength, and dopant content of the beads. The produced catalyst beads are catalytically active, mechanically robust, and suitable for packed-bed reactor applications. The produced catalyst beads are suitable for biomass conversion, petrochemistry, petroleum refining, electrocatalysis, and other applications.

Glass Fiber Used in Light Communications.

DTIC Science & Technology

1980-11-05

narrow pulse width is extended about 4 millimicroseconds/ kilometer, the gallium arsenide emptying into the laser is extended about 0.1...glass for the core forms quartz glass fiber. Possibly the use of the chemical vapour deposition method can make low ref racting glass for the...directly from the vapour phase and reaches a very high optical homogeneity. When the temperature of the high frequency induction plasma flame is very

Outdoor Performance of a Thin-Film Gallium-Arsenide Photovoltaic Module

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silverman, T. J.; Deceglie, M. G.; Marion, B.

2013-06-01

We deployed a 855 cm2 thin-film, single-junction gallium arsenide (GaAs) photovoltaic (PV) module outdoors. Due to its fundamentally different cell technology compared to silicon (Si), the module responds differently to outdoor conditions. On average during the test, the GaAs module produced more power when its temperature was higher. We show that its maximum-power temperature coefficient, while actually negative, is several times smaller in magnitude than that of a Si module used for comparison. The positive correlation of power with temperature in GaAs is due to temperature-correlated changes in the incident spectrum. We show that a simple correction based on precipitablemore » water vapor (PWV) brings the photocurrent temperature coefficient into agreement with that measured by other methods and predicted by theory. The low operating temperature and small temperature coefficient of GaAs give it an energy production advantage in warm weather.« less

High-Performance Inkjet-Printed Indium-Gallium-Zinc-Oxide Transistors Enabled by Embedded, Chemically Stable Graphene Electrodes.

PubMed

Secor, Ethan B; Smith, Jeremy; Marks, Tobin J; Hersam, Mark C

2016-07-13

Recent developments in solution-processed amorphous oxide semiconductors have established indium-gallium-zinc-oxide (IGZO) as a promising candidate for printed electronics. A key challenge for this vision is the integration of IGZO thin-film transistor (TFT) channels with compatible source/drain electrodes using low-temperature, solution-phase patterning methods. Here we demonstrate the suitability of inkjet-printed graphene electrodes for this purpose. In contrast to common inkjet-printed silver-based conductive inks, graphene provides a chemically stable electrode-channel interface. Furthermore, by embedding the graphene electrode between two consecutive IGZO printing passes, high-performance IGZO TFTs are achieved with an electron mobility of ∼6 cm(2)/V·s and current on/off ratio of ∼10(5). The resulting printed devices exhibit robust stability to aging in ambient as well as excellent resilience to thermal stress, thereby offering a promising platform for future printed electronics applications.

Influences of Gate Bias and Light Stresses on Device Characteristics of High-Energy Electron-Beam-Irradiated Indium Gallium Zinc Oxide Based Thin Film Transistors

NASA Astrophysics Data System (ADS)

Yu, Kyeong Min; Moon, Hye Ji; Ryu, Min Ki; Cho, Kyoung Ik; Yun, Eui-Jung; Bae, Byung Seong

2012-09-01

Under white light illumination, amorphous indium-gallium-zinc oxide (a-IGZO)-based thin-film transistors (TFTs) showed a large negative shift of threshold voltage of more than -15 V depending on the process conditions. We investigated the influences of both gate bias and white light illumination on device properties of IGZO-based TFTs untreated and treated with high-energy electron beam irradiation (HEEBI). The TFTs were treated with HEEBI in air at room temperature (RT), electron beam energy of 0.8 MeV, and a dose of 1×1014 electrons/cm2. The HEEBI-treated TFTs showed an improved stability under negative bias illumination stress (NBIS) and positive bias illumination stress (PBIS) compared with non-HEEBI-treated TFTs, suggesting that the acceptor-like defects might be generated by HEEBI treatment near the valence band edge.

Properties of GaAs:Cr-based Timepix detectors

NASA Astrophysics Data System (ADS)

Smolyanskiy, P.; Bergmann, B.; Chelkov, G.; Kotov, S.; Kruchonak, U.; Kozhevnikov, D.; Mora Sierra, Y.; Stekl, I.; Zhemchugov, A.

2018-02-01

The hybrid pixel detector technology brought to the X-ray imaging a low noise level at a high spatial resolution, thanks to the single photon counting. However, silicon as the most widespread detector material is marginally sensitive to photons with energies above 30 keV. Therefore, the high-Z alternatives to silicon such as gallium arsenide and cadmium telluride are increasingly attracting attention of the community for the development of X-ray imaging systems. The results of our investigations of the Timepix detectors bump bonded to sensors made of gallium arsenide compensated by chromium (GaAs:Cr) are presented in this work. The following properties are most important from the practical point of view: the IV characteristics, the charge transport characteristics, photon detection efficiency, operational stability, homogeneity, temperature dependence, as well as energy and spatial resolution are considered. The applicability of these detectors for spectroscopic X-ray imaging is discussed.

Nitrogen-Polar (000 1 ¯ ) GaN Grown on c-Plane Sapphire with a High-Temperature AlN Buffer.

PubMed

Song, Jie; Han, Jung

2017-03-02

We demonstrate growing nitrogen-polar (N-polar) GaN epilayer on c-plane sapphire using a thin AlN buffer layer by metalorganic chemical vapor deposition. We have studied the influence of the AlN buffer layer on the polarity, crystalline quality, and surface morphology of the GaN epilayer and found that the growth temperature of the AlN buffer layer played a critical role in the growth of the GaN epilayer. The low growth temperature of the AlN buffer results in gallium-polar GaN. Even a nitridation process has been conducted. High growth temperature for an AlN buffer layer is required to achieve pure N-polarity, high crystalline quality, and smooth surface morphology for a GaN epilayer.

Growth of AlGaN under the conditions of significant gallium evaporation: Phase separation and enhanced lateral growth

NASA Astrophysics Data System (ADS)

Mayboroda, I. O.; Knizhnik, A. A.; Grishchenko, Yu. V.; Ezubchenko, I. S.; Zanaveskin, Maxim L.; Kondratev, O. A.; Presniakov, M. Yu.; Potapkin, B. V.; Ilyin, V. A.

2017-09-01

The growth kinetics of AlGaN in NH3 MBE under significant Ga desorption was studied. It was found that the addition of gallium stimulates 2D growth and provides better morphology of films compared to pure AlN. The effect was experimentally observed at up to 98% desorption of the impinging gallium. We found that under the conditions of significant thermal desorption, larger amounts of gallium were retained at lateral boundaries of 3D surface features than at flat terraces because of the higher binding energy of Ga atoms at specific surface defects. The selective accumulation of gallium resulted in an increase in the lateral growth component through the formation of the Ga-enriched AlGaN phase at boundaries of 3D surface features. We studied the temperature dependence of AlGaN growth rate and developed a kinetic model analytically describing this dependence. As the model was in good agreement with the experimental data, we used it to estimate the increase in the binding energy of Ga atoms at surface defects compared to terrace surface sites using data on the Ga content in different AlGaN phases. We also applied first-principles calculations to the thermodynamic analysis of stable configurations on the AlN surface and then used these surface configurations to compare the binding energy of Ga atoms at terraces and steps. Both first-principles calculations and analytical estimations of the experimental results gave similar values of difference in binding energies; this value is 0.3 eV. Finally, it was studied experimentally whether gallium can act as a surfactant in AlN growth by NH3 MBE at elevated temperatures. Gallium application has allowed us to grow a 300 nm thick AlN film with a RMS surface roughness of 2.2 Å over an area of 10 × 10 μm and a reduced density of screw dislocations.

A Flexible Master Oscillator for a Thomson Scattering Pulse-Burst Laser System

NASA Astrophysics Data System (ADS)

den Hartog, D. J.; Young, W. C.

2015-11-01

A new master oscillator will be installed in the pulse-burst laser system used for high-rep-rate Thomson scattering on the MST experiment. This new master oscillator will enable pulse repetition rates up to 1 MHz, with the ability to program a burst of pulses with arbitrary and varying time separation between each pulse. In addition, the energy of each master oscillator pulse can be adjusted to compensate for gain variations in the power amplifier section of the laser system. This flexibility is accomplished by chopping a CW laser source with a high-bandwidth acousto-optic modulator (AOM). The laser source is a 1064 nm diode-pumped solid-state laser with continuous output power variable from 100 to 500 mW. The 2 mm diameter polarized beam is focused into the gallium phosphide crystal of the AOM, which deflects the beam by approximately 60 mrad. Beam deflection is controlled by a simple digital input pulse, and is capable of producing laser pulses of less than 20 ns width at repetition rates much greater than 1 MHz. These pulses from the output of the AOM will be collimated and propagated into the laser amplifier system, where they will be amplified to ~ 2 J/pulse and injected into the MST plasma. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences under Award Number DE-FC02-05ER54814, and by the National Science Foundation under Award Number PHY-0821899.

Photoelectrochemical cell having photoanode with thin boron phosphide coating as a corrosion resistant layer

DOEpatents

Baughman, Richard J.; Ginley, David S.

1984-01-01

A surface prone to corrosion in corrosive environments is rendered anticorrosive by CVD growing a thin continuous film, e.g., having no detectable pinholes, thereon, of boron phosphide. In one embodiment, the film is semiconductive. In another aspect, the invention is an improved photoanode, and/or photoelectrochemical cell with a photoanode having a thin film of boron phosphide thereon rendering it anitcorrosive, and providing it with unexpectedly improved photoresponsive properties.

Enhancement of the emission efficiency of InGaN films by suppressing the incorporation of unintentional gallium atoms

NASA Astrophysics Data System (ADS)

Yang, J.; Liu, S. T.; Wang, X. W.; Zhao, D. G.; Jiang, D. S.; Chen, P.; Zhu, J. J.; Liu, Z. S.; Liang, F.; Liu, W.; Zhang, L. Q.; Yang, H.; Wang, W. J.; Li, M.

2018-01-01

InGaN samples are grown using metalorganic chemical vapor deposition (MOCVD) and the dependences of structural and luminescence properties of InGaN layers on growth temperature are studied. It is found that the luminescence properties of InGaN layer are improved by increasing growth temperature properly. However, when the growth temperature of InGaN layer is too higher (740 °C in our work), a large amount of unintentionally incorporated gallium atoms enter into InGaN, and a spiral growth mode dominates in this case. It results in an inferior crystalline and interface quality, and ultimately degrades the luminescence of InGaN.

High Efficiency Multijunction Solar Cells with Finely-Tuned Quantum Wells

NASA Astrophysics Data System (ADS)

Varonides, Argyrios C.

The field of high efficiency (inorganic) photovoltaics (PV) is rapidly maturing in both efficiency goals and cover all cost reduction of fabrication. On one hand, know-how from space industry in new solar cell design configurations and on the other, fabrication cost reduction challenges for terrestrial uses of solar energy, have paved the way to a new generation of PV devices, capable of capturing most of the solar spectrum. For quite a while now, the goal of inorganic solar cell design has been the total (if possible) capture-absorption of the solar spectrum from a single solar cell, designed in such a way that a multiple of incident wavelengths could be simultaneously absorbed. Multi-absorption in device physics indicates parallel existence of different materials that absorb solar photons of different energies. Bulk solid state devices absorb at specific energy thresholds, depending on their respective energy gap (EG). More than one energy gaps would on principle offer new ways of photon absorption: if such a structure could be fabricated, two or more groups of photons could be absorbed simultaneously. The point became then what lattice-matched semiconductor materials could offer such multiple levels of absorption without much recombination losses. It was soon realized that such layer multiplicity combined with quantum size effects could lead to higher efficiency collection of photo-excited carriers. At the moment, the main reason that slows down quantum effect solar cell production is high fabrication cost, since it involves primarily expensive methods of multilayer growth. Existing multi-layer cells are fabricated in the bulk, with three (mostly) layers of lattice-matched and non-lattice-matched (pseudo-morphic) semiconductor materials (GaInP/InGaN etc), where photo-carrier collection occurs in the bulk of the base (coming from the emitter which lies right under the window layer). These carriers are given excess to conduction via tunnel junction (grown between at each interface and connecting the layers in series). This basic idea of a design has proven very successful in recent years, leading to solar cells of efficiency levels well above 30% (Fraunhofer Institute's multi-gap solar cell at 40.8%, and NREL's device at 40.2% respectively). Successful alloys have demonstrated high performance, such as InxGa1 - xP alloys (x (%) of gallium phosphide and (1 - x) (%) of indium phosphide). Other successful candidates, in current use and perpetual cell design consideration, are the lattice-matched GaAs/AlGaAs and InP/GaAs pairs or AlAs/GaAs/GaAs triple layers and alloys, which are heavily used in both solar and the electronics industry.

Suppression of the self-heating effect in GaN HEMT by few-layer graphene heat spreading elements

NASA Astrophysics Data System (ADS)

Volcheck, V. S.; Stempitsky, V. R.

2017-11-01

Self-heating has an adverse effect on characteristics of gallium nitride (GaN) high electron mobility transistors (HEMTs). Various solutions to the problem have been proposed, however, a temperature rise due to dissipated electrical power still hinders the production of high power and high speed GaN devices. In this paper, thermal management of GaN HEMT via few-layer graphene (FLG) heat spreading elements is investigated. It is shown that integration of the FLG elements on top of the device structure considerably reduces the maximum temperature and improves the DC and small signal AC performance.

The electrical properties of 60 keV zinc ions implanted into semi-insulating gallium arsenide

NASA Technical Reports Server (NTRS)

Littlejohn, M. A.; Anikara, R.

1972-01-01

The electrical behavior of zinc ions implanted into chromium-doped semiinsulating gallium arsenide was investigated by measurements of the sheet resistivity and Hall effect. Room temperature implantations were performed using fluence values from 10 to the 12th to 10 to the 15th power/sq cm at 60 keV. The samples were annealed for 30 minutes in a nitrogen atmosphere up to 800 C in steps of 200 C and the effect of this annealing on the Hall effect and sheet resistivity was studied at room temperature using the Van der Pauw technique. The temperature dependence of sheet resistivity and mobility was measured from liquid nitrogen temperature to room temperature. Finally, a measurement of the implanted profile was obtained using a layer removal technique combined with the Hall effect and sheet resistivity measurements.

Enhanced hydrogen evolution reaction on hybrids of cobalt phosphide and molybdenum phosphide

NASA Astrophysics Data System (ADS)

Fang, Si-Ling; Chou, Tsu-Chin; Samireddi, Satyanarayana; Chen, Kuei-Hsien; Chen, Li-Chyong; Chen, Wei-Fu

2017-03-01

Production of hydrogen from water electrolysis has stimulated the search of sustainable electrocatalysts as possible alternatives. Recently, cobalt phosphide (CoP) and molybdenum phosphide (MoP) received great attention owing to their superior catalytic activity and stability towards the hydrogen evolution reaction (HER) which rivals platinum catalysts. In this study, we synthesize and study a series of catalysts based on hybrids of CoP and MoP with different Co/Mo ratio. The HER activity shows a volcano shape and reaches a maximum for Co/Mo = 1. Tafel analysis indicates a change in the dominating step of Volmer-Hyrovský mechanism. Interestingly, X-ray diffraction patterns confirmed a major ternary interstitial hexagonal CoMoP2 crystal phase is formed which enhances the electrochemical activity.

Yellow phosphorus-induced Brugada phenocopy.

PubMed

Dharanipradab, Mayakrishnan; Viswanathan, Stalin; Kumar, Gokula Raman; Krishnamurthy, Vijayalatchumy; Stanley, Daphene Divya

Metallic phosphides (of aluminum and phosphide) and yellow phosphorus are commonly used rodenticide compounds in developing countries. Toxicity of yellow phosphorus mostly pertains to the liver, kidney, heart, pancreas and the brain. Cardiotoxicity with associated Brugada ECG pattern has been reported only in poisoning with metallic phosphides. Brugada phenocopy and hepatic dysfunction were observed in a 29-year-old male following yellow phosphorus consumption. He had both type 1 (day1) and type 2 (day2) Brugada patterns in the electrocardiogram, which resolved spontaneously by the third day without hemodynamic compromise. Toxins such as aluminum and zinc phosphide have been reported to induce Brugada ECG patterns due to the generation of phosphine. We report the first case of yellow phosphorus-related Brugada phenocopy, without hemodynamic compromise or malignant arrhythmia. Copyright © 2017 Elsevier Inc. All rights reserved.

Pesticide poisoning.

PubMed

Goel, Ashish; Aggarwal, Praveen

2007-01-01

Acute poisoning with pesticides is a global public health problem and accounts for as many as 300,000 deaths worldwide every year. The majority of deaths occur due to exposure to organophosphates, organochlorines and aluminium phosphide. Organophosphate compounds inhibit acetylcholinesterase resulting in acute toxicity. Intermediate syndrome can develop in a number of patients and may lead to respiratory paralysis and death. Management consists of proper oxygenation, atropine in escalating doses and pralidoxime in high doses. It is Important to decontaminate the skin while taking precautions to avoid secondary contamination of health personnel. Organochlorine pesticides are toxic to the central nervous system and sensitize the myocardium to catecholamines. Treatment involves supportive care and avoiding exogenous sympathomimetic agents. Ingestion of paraquat causes severe inflammation of the throat, corrosive injury to the gastrointestinal tract, renal tubular necrosis, hepatic necrosis and pulmonary fibrosis. Administration of oxygen should be avoided as it produces more fibrosis. Use of immunosuppressive agents have improved outcome in patients with paraquat poisoning. Rodenticides include thallium, superwarfarins, barium carbonate and phosphides (aluminium and zinc phosphide). Alopecia is an atypical feature of thallium toxicity. Most exposures to superwarfarins are harmless but prolonged bleeding may occur. Barium carbonate Ingestion can cause severe hypokalaemia and respiratory muscle paralysis. Aluminium phosphide is a highly toxic agent with mortality ranging from 37% to 100%. It inhibits mitochondrial cytochrome c oxidase and leads to pulmonary and cardiac toxicity. Treatment is supportive with some studies suggesting a beneficial effect of magnesium sulphate. Pyrethroids and insect repellants (e.g. diethyltoluamide) are relatively harmless but can cause toxic effects to pulmonary and central nervous systems. Ethylene dibromide-a highly toxic, fumigant pesticide-produces oral ulcerations, followed by liver and renal toxicity, and is almost uniformly fatal. Physicians working in remote and rural areas need to be educated about early diagnosis and proper management using supportive care and antidotes, wherever available.

Liquid gallium columns sheathed with carbon: Bulk synthesis and manipulation.

PubMed

Zhan, Jinhua; Bando, Yoshio; Hu, Junqing; Golberg, Dmitri; Nakanishi, Haruyuki

2005-06-16

It is impossible to fabricate isolated gallium nanomaterials due to the low melting point of Ga (29.8 degrees C) and its high reactivity. We report the bulk synthesis of uniform liquid Ga columns encapsulated into carbon nanotubes through high-temperature chemical reaction between Ga and CH4. The diameter of filled Ga liquid columns is approximately 25 nm, and their length is up to several micrometers. The thickness of the carbon sheaths is approximately 6 nm. Simultaneous condensation of a Ga vapor and carbon clusters results in the generation of Ga-filled carbon nanotubes. A convergent 300 kV electron beam generated in a field emission high-resolution electron microscope is demonstrated to be a powerful tool for delicate manipulation of the liquid Ga nanocolumns: they can be gently joined, cut, and sealed within carbon nanotubes. The self-organization of a carbon sheath during the electron-beam irradiation is discussed. The electron-beam irradiation may also become a decent tool for Ga-filled carbon nanotube thermometer calibration.

Al xGa 1-xN (0⩽ x⩽1) nanocrystalline powder by pyrolysis route

NASA Astrophysics Data System (ADS)

Garcia, R.; Srinivasan, S.; Contreras, O. E.; Thomas, A. C.; Ponce, F. A.

2007-10-01

A novel method to synthesize nanocrystalline Al xGa 1-xN (0⩽ x⩽1) powders is presented in this work. AlGaN nanocrystallites with the wurtzite structure were produced by thermal decomposition of a gallium-aluminum complex compound at 1000 °C in a three-zone horizontal quartz tube reactor under high-purity ammonia atmosphere. The crystallites showed a hexagonal structure, high homogeneity, and a narrow particle-size distribution at around 50 nm. A continuous composition range from 0 to 1 mol fraction can be reached by this method, allowing high control on the gallium and aluminum composition by monitoring the stoichiometry of the reaction between the metal nitrates and carbohydrazide. Low-temperature photoluminescence and cathodoluminescence studies showed that some impurities, such as carbon and oxygen, are unintentionally present in the final product and affect the optical properties. Subsequent thermal treatments between 900 and 1100 °C under an ammonia atmosphere significantly improved the quality of these materials.

A Study of Photoluminiscence and UV-Vis in Enhanced GaN Nanofibers

NASA Astrophysics Data System (ADS)

Robles-Garcia, Joshua; Melendez-Zambrana, Anamaris; Ramos, Idalia

2014-03-01

The photoluminiscence (PL) and UV-Vis properties of Gallium Nitride (GaN) nanofibers were investigated for samples fabricated with a precursor solution containing Gallium Nitrate Hydrate, Cellulose Acetate, and Urea in the solvents Dimethylacetamide (DMA) and Acetone. GaN is a wide bandgap (3.4 eV) semiconductor that can be used in a variety of applications including solid-state lighting, high power, and high frequency devices. In previous work, we produced polycrystalline GaN nanofibers with wurtzite structure, using the electrospinning method and a thermal treatment in nitrogen and ammonia at 1000C. In this research we study the addition of urea to the precursor solution to enhance the crystallinity of the fibers at lower sintering temperatures. The molar ratios of urea added to the precursor range from 0 to 1.7 M. After electrospinning the fibers were sintered in Nitrogen at 450C for 3 hours and then, under ammonia gas flow at 900C for 5 hours. X-Ray Diffraction (XRD), UV-Vis spectroscopy, and PL measurements at room temperature were used to study the structural and optical properties of the fibers during the sintering process. This work was sponsored by UPRH PREM (NSF-DMR-0934195).

Hybrid solar collector using nonimaging optics and photovoltaic components

NASA Astrophysics Data System (ADS)

Winston, Roland; Yablonovitch, Eli; Jiang, Lun; Widyolar, Bennett K.; Abdelhamid, Mahmoud; Scranton, Gregg; Cygan, David; Kozlov, Alexandr

2015-08-01

The project team of University of California at Merced (UC-M), Gas Technology Institute, and Dr. Eli Yablonovitch of University of California at Berkeley developed a novel hybrid concentrated solar photovoltaic thermal (PV/T) collector using nonimaging optics and world record single-junction Gallium arsenide (GaAs) PV components integrated with particle laden gas as thermal transfer and storage media, to simultaneously generate electricity and high temperature dispatchable heat. The collector transforms a parabolic trough, commonly used in CSP plants, into an integrated spectrum-splitting device. This places a spectrum-sensitive topping element on a secondary reflector that is registered to the thermal collection loop. The secondary reflector transmits higher energy photons for PV topping while diverting the remaining lower energy photons to the thermal media, achieving temperatures of around 400°C even under partial utilization of the solar spectrum. The collector uses the spectral selectivity property of Gallium arsenide (GaAs) cells to maximize the exergy output of the system, resulting in an estimated exergy efficiency of 48%. The thermal media is composed of fine particles of high melting point material in an inert gas that increases heat transfer and effectively stores excess heat in hot particles for later on-demand use.

High performance InP JFETs grown by MOCVD using tertiarybutylphosphine

NASA Astrophysics Data System (ADS)

Hashemi, M. M.; Shealy, J. B.; Corvini, P. J.; Denbaars, S. P.; Mishra, U. K.

1994-02-01

Indium phosphide channel junction field effect transistors were fabricated by metalorganic chemical vapor deposition using tertiarybulylphosphine (TBP) as the alternative source for phosphine. At growth temperatures of 600°C, InP with specular surface morphology and mobilities as high as 61000 cm2/V s at 77Khas been achieved using trimethylindium and TBP. To improve device isolation, pinch-off characteristics, and output transconductance, we employ a high resistivity (1 × 108 Ω-cm) semi-insulating InP buffer layer using ferrocene as the Fe-dopant. Devices with gate lengths of 1 urn exhibit very high extrinsic transconductance of 130 mS/mm, gate-drain breakdown voltage exceeding 20 V, maximum current density of >450 mA/mm with record high fT and fmax of 15 GHz and 35 GHz, respectively. These results indicate: that InP JFETs are promising electronic devices for microwave power amplification, and that TBP is capable of device quality materials.

Thermodynamic properties of lanthanum in gallium-zinc alloys

NASA Astrophysics Data System (ADS)

Dedyukhin, A. S.; Shepin, I. E.; Kharina, E. A.; Shchetinskiy, A. V.; Volkovich, V. A.; Yamshchikov, L. F.

2016-09-01

Thermodynamic properties of lanthanum were determined in gallium-zinc alloys of the eutectic and over-eutectic compositions. The electromotive force measurements were used to determine thermodynamic activity and sedimentation technique to measure solubility of lanthanum in liquid metal alloys. Temperature dependencies of lanthanum activity, solubility and activity coefficients in alloys with Ga-Zn mixtures containing 3.64, 15 and 50 wt. % zinc were obtained.

Clinical use of photodynamic antimicrobial chemotherapy for the treatment of deep carious lesions

NASA Astrophysics Data System (ADS)

Guglielmi, Camila De Almeida B.; Simionato, Maria Regina L.; Ramalho, Karen Müller; Imparato, José Carlos P.; Pinheiro, Sérgio Luiz; Luz, Maria A. A. C.

2011-08-01

The purpose of this study was to assess photodynamic antimicrobial chemotherapy (PACT) via irradiation, using a low power laser associated with a photosensitization dye, as an alternative to remove cariogenic microorganisms by drilling. Remaining dentinal samples in deep carious lesions on permanent molars (n = 26) were treated with 0.01% methylene blue dye and irradiated with a low power laser (InGaAIP - indium gallium aluminum phosphide; λ = 660 nm; 100 mW; 320 Jcm-2 90 s; 9J). Samples of dentin from the pulpal wall region were collected with a micropunch before and immediately after PACT and kept in a transport medium for microbiological analysis. Samples were cultured in plates of Brucella blood agar, Mitis Salivarius Bacitracin agar and Rogosa SL agar to determine the total viable bacteria, mutans streptococci and Lactobacillus spp. counts, respectively. After incubation, colony-forming units were counted and microbial reduction was calculated for each group of bacteria. PACT led to statistically significant reductions in mutans streptococci (1.38 log), Lactobacillus spp. (0.93 log), and total viable bacteria (0.91 log). This therapy may be an appropriate approach for the treatment of deep carious lesions using minimally invasive procedures.

Fano-like resonances in split concentric nanoshell dimers in designing negative-index metamaterials for biological-chemical sensing and spectroscopic purposes.

PubMed

Ahmadivand, Arash; Karabiyik, Mustafa; Pala, Nezih

2015-05-01

In this study, we investigated numerically the plasmon response of a dimer configuration composed of a couple of split and concentric Au nanoshells in a complex orientation. We showed that an isolated composition of two concentric split nanoshells could be tailored to support strong plasmon resonant modes in the visible wavelengths. After determining the accurate geometric dimensions for the presented antisymmetric nanostructure, we designed a dimer array that shows complex behavior during exposure to different incident polarizations. We verified that the examined dimer was able to support destructive interference between dark and bright plasmon modes, which resulted in a pronounced Fano-like dip. Observation of a Fano minimum in such a simple molecular orientation of subwavelength particles opens new avenues for employing this structure in designing various practical plasmonic devices. Depositing the final dimer in a strong coupling condition on a semiconductor metasurface and measuring the effective refractive index at certain wavelengths, we demonstrate that each one of dimer units can be considered a meta-atom due to the high aspect ratio in the geometric parameters. Using this method, by extending the number of dimers periodically and illuminating the structure, we examined the isotropic, polarization-dependent, and transmission behavior of the metamaterial configuration. Using numerical methods and calculating the effective refractive indices, we computed and sketched corresponding figure of merit over the transmission window, where the maximum value obtained was 42.3 for Si and 54.6 for gallium phosphide (GaP) substrates.

Characterisation of Ga-coated and Ga-brazed aluminium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ferchaud, E.; Christien, F., E-mail: frederic.christien@univ-nantes.fr; Barnier, V.

This work is devoted to the brazing of aluminium using liquid gallium. Gallium was deposited on aluminium samples at {approx} 50 Degree-Sign C using a liquid gallium 'polishing' technique. Brazing was undertaken for 30 min at 500 Degree-Sign C in air. EDS (Energy Dispersive X-ray Spectroscopy) and AES (Auger Electron Spectroscopy) characterisation of Ga-coated samples has shown that the Ga surface layer thickness is of ten (or a few tens of) nanometres. Furthermore, aluminium oxide layer (Al{sub 2}O{sub 3}) was shown to be 'descaled' during Ga deposition, which ensures good conditions for further brazing. Cross-section examination of Ga-coated samples showsmore » that liquid gallium penetrates into the aluminium grain boundaries during deposition. The thickness of the grain boundary gallium film was measured using an original EDS technique and is found to be of a few tens of nanometres. The depth of gallium grain boundary penetration is about 300 {mu}m at the deposition temperature. The fracture stress of the brazed joints was measured from tensile tests and was determined to be 33 MPa. Cross-section examination of brazed joints shows that gallium has fully dissolved into the bulk and that the joint is really autogenous. - Highlights: Black-Right-Pointing-Pointer Aluminium can be brazed using liquid gallium deposited by a 'polishing' technique. Black-Right-Pointing-Pointer The aluminium oxide layer is 'descaled' during liquid Ga 'polishing' deposition. Black-Right-Pointing-Pointer EDS can be used for determination of surface and grain boundary Ga film thickness. Black-Right-Pointing-Pointer The surface and grain boundary Ga film thickness is of a few tens of nm. Black-Right-Pointing-Pointer Surface and grain boundary gallium dissolves in the bulk during brazing.« less

Surface Chemistry in Cobalt Phosphide-Stabilized Lithium-Sulfur Batteries.

PubMed

Zhong, Yiren; Yin, Lichang; He, Peng; Liu, Wen; Wu, Zishan; Wang, Hailiang

2018-01-31

Chemistry at the cathode/electrolyte interface plays an important role for lithium-sulfur batteries in which stable cycling of the sulfur cathode requires confinement of the lithium polysulfide intermediates and their fast electrochemical conversion on the electrode surface. While many materials have been found to be effective for confining polysulfides, the underlying chemical interactions remain poorly understood. We report a new and general lithium polysulfide-binding mechanism enabled by surface oxidation layers of transition-metal phosphide and chalcogenide materials. We for the first time find that CoP nanoparticles strongly adsorb polysulfides because their natural oxidation (forming Co-O-P-like species) activates the surface Co sites for binding polysulfides via strong Co-S bonding. With a surface oxidation layer capable of confining polysulfides and an inner core suitable for conducting electrons, the CoP nanoparticles are thus a desirable candidate for stabilizing and improving the performance of sulfur cathodes in lithium-sulfur batteries. We demonstrate that sulfur electrodes that hold a high mass loading of 7 mg cm -2 and a high areal capacity of 5.6 mAh cm -2 can be stably cycled for 200 cycles. We further reveal that this new surface oxidation-induced polysulfide-binding scheme applies to a series of transition-metal phosphide and chalcogenide materials and can explain their stabilizing effects for lithium-sulfur batteries.

Moringa oleifera extract (Lam) attenuates Aluminium phosphide-induced acute cardiac toxicity in rats.

PubMed

Gouda, Ahmed S; El-Nabarawy, Nagla A; Ibrahim, Samah F

2018-01-01

Moringa oleifera extract (Lam) has many antioxidant and protective properties. Objective: to investigate the antioxidant activities of Lam in counteracting the high oxidative stress caused by acute sub-lethal aluminium phosphide (AlP) intoxication in rat heart. These activities will be detected by histopathological examination and some oxidative stress biomarkers. a single sub-lethal dose of Alp (2 mg/kg body weight) was administered orally, and Lam was given orally at a dose (100 mg/kg body weight) one hour after receiving AlP to rats. aluminium phosphide caused significant cardiac histopathological changes with a significant increase in malondialdehyde (MDA); lipid peroxidation marker; and a significant depletion of antioxidant enzymes (catalase and glutathione reductase). However, treatment with Lam protected efficiently the cardiac tissue of intoxicated rats by increasing antioxidants levels with slight decreasing in MDA production compared to untreated group. This study suggested that Moringa oleifera extract could possibly restore the altered cardiac histopathology and some antioxidant power in AlP intoxicated rats, and it could even be used as adjuvant therapy against AlP-induced cardiotoxicity.

Surface-oxidized cobalt phosphide used as high efficient electrocatalyst in activated carbon air-cathode microbial fuel cell

NASA Astrophysics Data System (ADS)

Yang, Tingting; Wang, Zhong; Li, Kexun; Liu, Yi; Liu, Di; Wang, Junjie

2017-09-01

Herein, we report a simplistic method to fabricate the surface-oxidized cobalt phosphide (CoP) nanocrystals (NCs), which is used as electrocatalyst for oxygen reduction reaction (ORR) in microbial fuel cell (MFC) for the first time. The corallite-like CoP NCs are successfully prepared by a hydrothermal reaction following a phosphating treatment in N2 atmosphere. When used as an ORR catalyst, cobalt phosphide shows comparable onset potential, inferior resistance, as well as a small Tafel slope with long-term stability in neutral media. The maximum power density of MFC embellished with 10% CoP reached 1914.4 ± 59.7 mW m-2, which is 108.5% higher than the control. The four-electron pathway, observed by the RDE, plays a crucial role in electrochemical catalytic activity. In addition, material characterizations indicate that the surface oxide layer (CoOx) around the metallic CoP core is important and beneficial for ORR. Accordingly, it can be expected that the as-synthesized CoP will be a promising candidate of the non-precious metal ORR electrocatalysts for electrochemical energy applications.

Structure-Activity Relationships for Pt-Free Metal Phosphide Hydrogen Evolution Electrocatalysts.

PubMed

Owens-Baird, Bryan; Kolen'ko, Yury V; Kovnir, Kirill

2018-05-23

In the field of renewable energy, the splitting of water into hydrogen and oxygen fuel gases using water electrolysis is a prominent topic. Traditionally, these catalytic processes have been performed by platinum-group metal catalysts, which are effective at promoting water electrolysis but expensive and rare. The search for an inexpensive and Earth-abundant catalyst has led to the development of 3d-transition-metal phosphides for the hydrogen evolution reaction. These catalysts have shown excellent activity and stability. In this review, we discuss the electronic and crystal structures of bulk and surface of selected Fe, Co, and Ni phosphides, and their relationships to the experimental catalytic activity. The various synthetic protocols towards the state-of-the-art transition metal phosphide electrocatalysts are also discussed. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Morphology, mechanical stability, and protective properties of ultrathin gallium oxide coatings.

PubMed

Lawrenz, Frank; Lange, Philipp; Severin, Nikolai; Rabe, Jürgen P; Helm, Christiane A; Block, Stephan

2015-06-02

Ultrathin gallium oxide layers with a thickness of 2.8 ± 0.2 nm were transferred from the surface of liquid gallium onto solid substrates, including conjugated polymer poly(3-hexylthiophene) (P3HT). The gallium oxide exhibits high mechanical stability, withstanding normal pressures of up to 1 GPa in contact mode scanning force microscopy imaging. Moreover, it lowers the rate of photodegradation of P3HT by 4 orders of magnitude, as compared to uncovered P3HT. This allows us to estimate the upper limits for oxygen and water vapor transmission rates of 0.08 cm(3) m(-2) day(-1) and 0.06 mg m(-2) day(-1), respectively. Hence, similar to other highly functional coatings such as graphene, ultrathin gallium oxide layers can be regarded as promising candidates for protective layers in flexible organic (opto-)electronics and photovoltaics because they offer permeation barrier functionalities in conjunction with high optical transparency.

Renal amyloidosis. Evaluation by gallium imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, V.W.; Skinner, M.; Cohen, A.S.

1986-09-01

A study has been performed to evaluate the efficacy of gallium imaging in the detection of renal amyloidosis. Ten of the 11 patients who had biopsy-proven renal amyloidosis demonstrated marked uptake in both kidneys. One patient revealed moderate gallium uptake in his kidneys. None of the patients had underlying renal or extrarenal pathology other than amyloidosis, which could account for renal gallium uptake (renal infection, neoplasm, hepatic failure or frequent blood transfusions). Four patients also had extrarenal foci of abnormal gallium uptake, suggesting other sites of amyloid deposits. Our data strongly suggest that gallium imaging has a high sensitivity formore » detection of renal amyloidosis. Its specificity is enhanced significantly by careful review of the clinical history to exclude other known causes of renal gallium uptake. Potentially, gallium imaging may be used to monitor the progress of patients under experimental therapy.« less

Effect of gas flow ratio on the microstructure and mechanical properties of boron phosphide films prepared by reactive magnetron sputtering

NASA Astrophysics Data System (ADS)

Jia, Z. C.; Zhu, J. Q.; Jiang, C. Z.; Shen, W. X.; Han, J. C.; Chen, R. R.

2011-10-01

Boron phosphide films were grown on silicon substrate by radio frequency reactive magnetron sputtering using boron target and hydrogen phosphine at different gas flow ratios (PH 3/Ar) at lower temperature. The chemical composition, microstructure and mechanical properties were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectrum, FTIR spectrum, surface profilometer and nano-indenter. The results indicate that the atomic ratio (P/B) rises from 1.06 up to 1.52 with the gas flow ratio increasing from 3/50 to 15/50. Simultaneously, the hardness and Young's modulus decrease from 25.4 GPa to 22.5 GPa, and 250.4 GPa to 238.4 GPa, respectively. Microstructure transforms from microcrystalline state to amorphous state along with the gas flow ratio increasing. Furthermore higher gas flow ratio leads to lower stress. The BP film prepared at the gas flow ratio of 3/50 can be contributed with the best properties.

Accurate Acoustic Thermometry I: The Triple Point of Gallium

NASA Astrophysics Data System (ADS)

Moldover, M. R.; Trusler, J. P. M.

1988-01-01

The speed of sound in argon has been accurately measured in the pressure range 25-380 kPa at the temperature of the triple point of gallium (Tg) and at 340 kPa at the temperature of the triple point of water (Tt). The results are combined with previously published thermodynamic and transport property data to obtain Tg = (302.9169 +/- 0.0005) K on the thermodynamic scale. Among recent determinations of T68 (the temperature on IPTS-68) at the gallium triple point, those with the smallest measurement uncertainty fall in the range 302.923 71 to 302.923 98 K. We conclude that T-T68 = (-6.9 +/- 0.5) mK near 303 K, in agreement with results obtained from other primary thermometers. The speed of sound was measured with a spherical resonator. The volume and thermal expansion of the resonator were determined by weighing the mercury required to fill it at Tt and Tg. The largest part of the standard error in the present determination of Tg is systematic. It results from imperfect knowledge of the thermal expansion of mercury between Tt and Tg. Smaller parts of the error result from imperfections in the measurement of the temperature of the resonator and of the resonance frequencies.

Crystalline-like temperature dependence of the electrical characteristics in amorphous Indium-Gallium-Zinc-Oxide thin film transistors

NASA Astrophysics Data System (ADS)

Estrada, M.; Hernandez-Barrios, Y.; Cerdeira, A.; Ávila-Herrera, F.; Tinoco, J.; Moldovan, O.; Lime, F.; Iñiguez, B.

2017-09-01

A crystalline-like temperature dependence of the electrical characteristics of amorphous Indium-Gallium-Zinc-Oxide (a-IGZO) thin film transistors (TFTs) is reported, in which the drain current reduces as the temperature is increased. This behavior appears for values of drain and gate voltages above which a change in the predominant conduction mechanism occurs. After studying the possible conduction mechanisms, it was determined that, for gate and drain voltages below these values, hopping is the predominant mechanism with the current increasing with temperature, while for values above, the predominant conduction mechanism becomes percolation in the conduction band or band conduction and IDS reduces as the temperature increases. It was determined that this behavior appears, when the effect of trapping is reduced, either by varying the density of states, their characteristic energy or both. Simulations were used to further confirm the causes of the observed behavior.

Onsite Calibration of a Precision IPRT Based on Gallium and Gallium-Based Small-Size Eutectic Points

NASA Astrophysics Data System (ADS)

Sun, Jianping; Hao, Xiaopeng; Zeng, Fanchao; Zhang, Lin; Fang, Xinyun

2017-04-01

Onsite thermometer calibration with temperature scale transfer technology based on fixed points can effectively improve the level of industrial temperature measurement and calibration. The present work performs an onsite calibration of a precision industrial platinum resistance thermometer near room temperature. The calibration is based on a series of small-size eutectic points, including Ga-In (15.7°C), Ga-Sn (20.5°C), Ga-Zn (25.2°C), and a Ga fixed point (29.7°C), developed in a portable multi-point automatic realization apparatus. The temperature plateaus of the Ga-In, Ga-Sn, and Ga-Zn eutectic points and the Ga fixed point last for longer than 2 h, and their reproducibility was better than 5 mK. The device is suitable for calibrating non-detachable temperature sensors in advanced environmental laboratories and industrial fields.

Determination of gallium at trace levels using a spectrofluorimetric method in synthetic U-Ga and Ga-As solutions.

PubMed

Kara, Derya; Fisher, Andrew; Foulkes, Mike; Hill, Steve J

2010-01-01

A simple, easy to use and selective spectrofluorimetric method for the determination of trace levels of gallium has been developed. A new Schiff base, N-o-vanillidine-2-amino-p-cresol (OVAC) was synthesized and its fluorescence activity with gallium investigated. Based on this chelation reaction, a spectrofluorimetric method has been developed for the determination of gallium in synthetically prepared Ga-U and Ga-As samples buffered at pH 4.0 using acetic acid-sodium acetate. The chelation reaction between Ga(III) and N-o-vanillidine-2-amino-p-cresol was very fast, requiring only 30min at room temperature to complex completely. The limit of detection (LOD) (3sigma) for Ga(III) was 7.17 nM (0.50 microgL(-1)), determined from the analysis of 11 different solutions of 20 microg L(-1) Ga(III). Copyright 2009 Elsevier B.V. All rights reserved.

Responses of Siberian ferrets to secondary zinc phosphide poisoning

USGS Publications Warehouse

Hill, E.F.; Carpenter, J.W.

1982-01-01

The hazard of operational-type applications of zinc phosphide (Zn3P2) on a species closely related to the black-footed ferret (Mustela nigripes), was evaluated by feeding 16 Siberian ferrets (M. eversmanni) rats that had been killed by consumption of 2% zinc phosphide treated bait or by an oral dose of 40, 80, or 160 mg of Zn3P2. All ferrets accepted rats and a single emesis by each of 3 ferrets was the only evidence of acute intoxication. All ferrets learned to avoid eating gastrointestinal tracts of the rats. Subacute zinc phosphide toxicity in the ferrets was indicated by significant decreases (18-48%) in hemoglobin, increases of 35-91 % in serum iron, and elevated levels of serum globulin, cholesterol, and triglycerides. Hemoglobin/iron, urea nitrogen/creatinine, and albumin/globulin ratios also were altered by the treatments. This study demonstrated that Siberian ferrets, or other species with a sensitive emetic reflex, are afforded a degree of protection from acute zinc phosphide poisoning due to its emetic action. The importance of toxicity associated with possible respiratory, liver, and kidney damage indicated by altered blood chemistries is not known.

Scalable and Tunable Carbide-Phosphide Composite Catalyst System for the Thermochemical Conversion of Biomass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Regmi, Yagya; Rogers, Bridget; Labbe, Nicole

We have prepared composite materials of hexagonal nickel phosphide and molybdenum carbide (Mo2C) utilizing a simple and scalable two-stage synthesis method comprised of carbothermic reduction followed by hydrothermal incubation. We observe the monophasic hexagonal phosphide Ni2P in the composite at low phosphide-to-carbide (P:C) ratios. Upon increasing the proportion of P:C, the carbide surface becomes saturated, and we detect the emergence of a second hexagonal nickel phosphide phase (Ni5P4) upon annealing. We demonstrate that vapor-phase upgrading (VPU) of whole biomass via catalytic fast pyrolysis is achievable using the composite material as a catalyst, and we monitor the resulting product slates usingmore » pyrolysis gas chromatography/mass spectrometry. Our analysis of the product vapors indicates that variation of the P:C molar ratio in the composite material affords product slates of varying complexity and composition, which is indicated by the number of products and their relative proportions in the product slate. Our results demonstrate that targeted vapor product composition can be obtained, which can potentially be utilized to tune the composition of the bio-oil downstream.« less

Scalable and Tunable Carbide-Phosphide Composite Catalyst System for the Thermochemical Conversion of Biomass

DOE PAGES

Regmi, Yagya; Rogers, Bridget; Labbe, Nicole; ...

2017-07-13

We have prepared composite materials of hexagonal nickel phosphide and molybdenum carbide (Mo2C) utilizing a simple and scalable two-stage synthesis method comprised of carbothermic reduction followed by hydrothermal incubation. We observe the monophasic hexagonal phosphide Ni2P in the composite at low phosphide-to-carbide (P:C) ratios. Upon increasing the proportion of P:C, the carbide surface becomes saturated, and we detect the emergence of a second hexagonal nickel phosphide phase (Ni5P4) upon annealing. We demonstrate that vapor-phase upgrading (VPU) of whole biomass via catalytic fast pyrolysis is achievable using the composite material as a catalyst, and we monitor the resulting product slates usingmore » pyrolysis gas chromatography/mass spectrometry. Our analysis of the product vapors indicates that variation of the P:C molar ratio in the composite material affords product slates of varying complexity and composition, which is indicated by the number of products and their relative proportions in the product slate. Our results demonstrate that targeted vapor product composition can be obtained, which can potentially be utilized to tune the composition of the bio-oil downstream.« less

New possibilities for Cr/sup 3 +/ ions as activators of the active media of solid-state lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zharikov, E.V.; Lavrishchev, S.V.; Laptev, V.V.

An analysis is made of the relationship between the excited-state lifetime of chromium and the ratio of the luminescence intensities in the /sup 4/T/sub 2/--/sup 4/A/sub 2/ and /sup 2/E--/sup 4/A/sub 2/ channels, on one hand, and the Cr/sup 3 +/..-->..acceptor energy transfer efficiency, on the other. A method is proposed for determination of the energy gap ..delta..E between the /sup 2/E and /sup 4/T/sub 2/ levels of Cr/sup 3 +/ from the temperature dependence of the Cr/sup 3 +/..-->..acceptor nonradiative transfer efficiency. Two independent methods were used to determine ..delta..E for gadolinium gallium garnet (GGG) crystals doped with chromiummore » and with chromium and neodymium. The probabilities of Cr/sup 3 +/ intracenter relaxation and typical parameters of the Cr/sup 3 +/--Nd/sup 3 +/ energy transfer process were also determined. It was found that the values of ..delta..E in gadolinium scandium gallium (GdScGaG) and lanthanum lutetium gallium garnet crystals are comparable with the values of kT at liquid helium temperature. It is shown that the high efficiency of the Cr/sup 3 +/..-->..Nd/sup 3 +/ nonradiative transfer in GGG and GdScGaG crystals doped with chromium and neodymium at room temperature is due to the relatively low value of ..delta..E. It is noted that there are many crystals having the garnet structure and low values of ..delta..E that are potentially suitable for developing lasers utilizing the /sup 4/T/sub 2/--/sup 4/A/sub 2/ electronic--vibrational transition in Cr/sup 3 +/ and having an emission frequency continuously tunable over a wide spectral range.« less

Gallium

USGS Publications Warehouse

Foley, Nora K.; Jaskula, Brian W.; Kimball, Bryn E.; Schulte, Ruth F.; Schulz, Klaus J.; DeYoung,, John H.; Seal, Robert R.; Bradley, Dwight C.

2017-12-19

Gallium is a soft, silvery metallic element with an atomic number of 31 and the chemical symbol Ga. Gallium is used in a wide variety of products that have microelectronic components containing either gallium arsenide (GaAs) or gallium nitride (GaN). GaAs is able to change electricity directly into laser light and is used in the manufacture of optoelectronic devices (laser diodes, light-emitting diodes [LEDs], photo detectors, and solar cells), which are important for aerospace and telecommunications applications and industrial and medical equipment. GaAs is also used in the production of highly specialized integrated circuits, semiconductors, and transistors; these are necessary for defense applications and high-performance computers. For example, cell phones with advanced personal computer-like functionality (smartphones) use GaAs-rich semiconductor components. GaN is used principally in the manufacture of LEDs and laser diodes, power electronics, and radio-frequency electronics. Because GaN power transistors operate at higher voltages and with a higher power density than GaAs devices, the uses for advanced GaN-based products are expected to increase in the future. Gallium technologies also have large power-handling capabilities and are used for cable television transmission, commercial wireless infrastructure, power electronics, and satellites. Gallium is also used for such familiar applications as screen backlighting for computer notebooks, flat-screen televisions, and desktop computer monitors.Gallium is dispersed in small amounts in many minerals and rocks where it substitutes for elements of similar size and charge, such as aluminum and zinc. For example, gallium is found in small amounts (about 50 parts per million) in such aluminum-bearing minerals as diaspore-boehmite and gibbsite, which form bauxite deposits, and in the zinc-sulfide mineral sphalerite, which is found in many mineral deposits. At the present time, gallium metal is derived mainly as a byproduct of the processing of bauxite ore for aluminum; lesser amounts of gallium metal are produced from the processing of sphalerite ore from three types of deposits (sediment-hosted, Mississippi Valley-type, and volcanogenic massive sulfide) for zinc. The United States is expected to meet its current and expected future needs for gallium through imports of primary, recycled, and refined gallium, as well as through domestic production of recycled and refined gallium. The U.S. Geological Survey estimates that world resources of gallium in bauxite exceed 1 billion kilograms, and a considerable quantity of gallium could be present in world zinc reserves.

Annealing of gallium nitride under high-N 2 pressure

NASA Astrophysics Data System (ADS)

Porowski, S.; Jun, J.; Krukowski, S.; Grzegory, I.; Leszczynski, M.; Suski, T.; Teisseyre, H.; Foxon, C. T.; Korakakis, D.

1999-04-01

GaN is the key material for blue and ultraviolet optoelectronics. It is a strongly bonded wurztite structure semiconductor with the direct energy gap 3.5 eV. Due to strong bonding, the diffusion processes require high temperatures, above 1300 K. However at this temperature range at ambient pressure, GaN becomes unstable and dissociates into Ga and N 2. Therefore high pressure of N 2 is required to study the diffusion and other annealing related processes. We studied annealing of bulk GaN nitride single crystals grown under high pressure and also annealing of homo- and heteroepitaxial GaN layers grown by MOCVD technique. Annealing at temperatures above 1300 K influences strongly the structural and optical properties of GaN crystals and layers. At this temperature diffusion of the Mg and Zn acceptors have been observed. In spite of very interesting experimental observations the understanding of microscopic mechanisms of these processes is limited.

Room-Temperature Synthesis of GaN Driven by Kinetic Energy beyond the Limit of Thermodynamics.

PubMed

Imaoka, Takane; Okada, Takeru; Samukawa, Seiji; Yamamoto, Kimihisa

2017-12-06

The nitridation reaction is significantly important to utilize the unique properties of nitrides and nitrogen-doped materials. However, nitridation generally requires a high temperature or highly reactive reagents (often explosive) because the energies of N-N bond cleavage and nitrogen anion formation (N 3- ) are very high. We demonstrate the first room-temperature synthesis of GaN directly from GaCl 3 by nanoscale atom exchange reaction. Nonequilibrium nitrogen molecules with very high translational energy were used as a chemically stable and safe nitrogen source. The irradiation of molecular nitrogen to the desired reaction area successfully provided a gallium nitride (GaN) nanosheet that exhibited a typical photoluminescence spectrum. Because this process retains the target substrate room temperature and does not involve any photon nor charged ion, it allows damage-less synthesis of the semiconducting metal nitrides, even directly on plastic substrates such as polyethylene terephthalate (PET).

Gallium-67 activity in bronchoalveolar lavage fluid in sarcoidosis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trauth, H.A.; Heimes, K.; Schubotz, R.

1986-01-01

Roentgenograms and gallium-67 scans and gallium-67 counts of BAL fluid samples, together with differential cell counts, have proved to be useful in assessing activity and lung involvement in sarcoidosis. In active pulmonary sarcoidosis gallium-67 scans are usually positive. Quantitation of gallium-67 uptake in lung scans, however, may be difficult. Because gallium-67 uptake and cell counts in BAL fluid may be correlated, we set out to investigate gallium-67 activity in BAL fluid recovered from patient of different groups. Sixteen patients with recently diagnosed and untreated sarcoidosis, nine patients with healthy lungs, and five patients with CFA were studied. Gallium-67 uptake ofmore » the lung, gallium-67 activity in the lavage fluid, SACE and LACE levels, and alpha 1-AT activity were measured. Significantly more gallium-67 activity was found in BAL fluid from sarcoidosis patients than in that from CFA patients (alpha = .001) or patients with healthy lungs (alpha = .001). Gallium-67 activity in BAL fluid could be well correlated with the number of lymphocytes in BAL fluid, but poorly with the number of macrophages. Subjects with increased levels of SACE or serum alpha 1-AT showed higher lavage gallium-67 activity than did normals, but no correlation could be established. High gallium-67 activity in lavage fluid may be correlated with acute sarcoidosis or physiological deterioration; low activity denotes change for the better. The results show that gallium-67 counts in BAL fluid reflects the intensity of gallium-67 uptake and thus of activity of pulmonary sarcoidosis.« less

New reactions involving the oxidative O-, N-, and C-phosphorylation of organic compounds by phosphorus and phosphides in the presence of metal complexes

NASA Astrophysics Data System (ADS)

Dorfman, Ya A.; Aleshkova, M. M.; Polimbetova, G. S.; Levina, L. V.; Petrova, T. V.; Abdreimova, R. R.; Doroshkevich, D. M.

1993-09-01

The mechanisms of new catalytic reactions leading to the formation of di-, and tri-alkyl phosphates, di- and tri-alkyl phosphites, phosphoramidites, phosphazenes, phosphines, and phosphine oxides from hydrogen, copper, and zinc phosphides and white and red phosphorus are analysed. The mechanisms of the activation of the reactants by metal complexes and of the reactions involving the oxidative P-O, P-N, and P-C coupling of organic compounds to phosphorus and phosphides are considered. The bibliography includes 124 references.

Phase equilibrium modeling for high temperature metallization on GaAs solar cells

NASA Technical Reports Server (NTRS)

Chung, M. A.; Davison, J. E.; Smith, S. R.

1991-01-01

Recent trends in performance specifications and functional requirements have brought about the need for high temperature metallization technology to be developed for survivable DOD space systems and to enhance solar cell reliability. The temperature constitution phase diagrams of selected binary and ternary systems were reviewed to determine the temperature and type of phase transformation present in the alloy systems. Of paramount interest are the liquid-solid and solid-solid transformations. Data are being utilized to aid in the selection of electrical contact materials to gallium arsenide solar cells. Published data on the phase diagrams for binary systems is readily available. However, information for ternary systems is limited. A computer model is being developed which will enable the phase equilibrium predictions for ternary systems where experimental data is lacking.

Aluminum phosphide

Integrated Risk Information System (IRIS)

Aluminum phosphide ; CASRN 20859 - 73 - 8 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinoge

Spray deposited gallium doped tin oxide thinfilm for acetone sensor application

NASA Astrophysics Data System (ADS)

Preethi, M. S.; Bharath, S. P.; Bangera, Kasturi V.

2018-04-01

Undoped and gallium doped (1 at.%, 2 at.% and 3 at.%) tin oxide thin films were prepared using spray pyrolysis technique by optimising the deposition conditions such as precursor concentration, substrate temperature and spraying rate. X-ray diffraction analysis revealed formation of tetragonally structured polycrystalline films. The SEM micrographs of Ga doped films showed microstructures. The electrical resistivity of the doped films was found to be more than that of the undoped films. The Ga-doped tin oxide thin films were characterised for gas sensors. 1 at.% Ga doped thin films were found to be better acetone gas sensor, showed 68% sensitivity at 350°C temperature.

Electron transport near the Mott transition in n-GaAs and n-GaN

NASA Astrophysics Data System (ADS)

Romanets, P. N.; Sachenko, A. V.

2016-01-01

In this paper, we study the temperature dependence of the conductivity and the Hall coefficient near the metal-insulator phase transition. A theoretical investigation is performed within the effective mass approximation. The variational method is used to calculate the eigenvalues and eigenfunctions of the impurity states. Unlike previous studies, we have included nonlinear corrections to the screened impurity potential, because the Thomas-Fermi approximation is incorrect for the insulator phase. It is also shown that near the phase transition the exchange interaction is essential. The obtained temperature dependencies explain several experimental measurements in gallium arsenide (GaAs) and gallium nitride (GaN).

Effects of the substitution of gallium with boron on the physical and mechanical properties of Ni-Mn-Ga shape memory alloys

NASA Astrophysics Data System (ADS)

Aydogdu, Yildirim; Turabi, Ali Sadi; Kok, Mediha; Aydogdu, Ayse; Tobe, Hirobumi; Karaca, Haluk Ersin

2014-12-01

The effects of the substitution of gallium with boron on the physical, mechanical and magnetic shape memory properties of Ni51Mn28.5Ga20.5- xBx (at.%) ( x = 0, 1, 2, 3) polycrystalline alloys are investigated. It has been found that transformation temperatures are decreasing while hardness is increasing with boron addition. B-doping of NiMnGa alloys results in the formation of a second phase that increases its ductility and strength in compression. Moreover, saturation magnetization of austenite is decreasing, while Curie temperature of austenite is increasing with B-doping.

Growth of semiconducting GaN hollow spheres and nanotubes with very thin shells via a controllable liquid gallium-gas interface chemical reaction.

PubMed

Yin, Long-Wei; Bando, Yoshio; Li, Mu-Sen; Golberg, Dmitri

2005-11-01

An in situ liquid gallium-gas interface chemical reaction route has been developed to synthesize semiconducting hollow GaN nanospheres with very small shell size by carefully controlling the synthesis temperature and the ammonia reaction gas partial pressure. In this process the gallium droplet does not act as a catalyst but rather as a reactant and a template for the formation of hollow GaN structures. The diameter of the synthesized hollow GaN spheres is typically 20-25 nm and the shell thickness is 3.5-4.5 nm. The GaN nanotubes obtained at higher synthesis temperatures have a length of several hundreds of nanometers and a wall thickness of 3.5-5.0 nm. Both the hollow GaN spheres and nanotubes are polycrystalline and are composed of very fine GaN nanocrystalline particles with a diameter of 3.0-3.5 nm. The room-temperature photoluminescence (PL) spectra for the synthesized hollow GaN spheres and nanotubes, which have a narrow size distribution, display a sharp, blue-shifted band-edge emission peak at 3.52 eV (352 nm) due to quantum size effects.

Gallium hole traps in irradiated KTiOPO{sub 4}:Ga crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grachev, V.; Meyer, M.; Malovichko, G.

2014-12-07

Nominally pure and gallium doped single crystals of potassium titanyl phosphate (KTiOPO{sub 4}) have been studied by Electron Paramagnetic Resonance at low temperatures before and after irradiation. Irradiation with 20 MeV electrons performed at room temperature and liquid nitrogen temperature caused an appearance of electrons and holes. Gallium impurities act as hole traps in KTiOPO{sub 4} creating Ga{sup 4+} centers. Two different Ga{sup 4+} centers were observed, Ga1 and Ga2. The Ga1 centers are dominant in Ga-doped samples. For the Ga1 center, a superhyperfine structure with one nucleus with nuclear spin ½ was registered and attributed to the interaction of galliummore » electrons with a phosphorus nucleus or proton in its surrounding. In both Ga1 and Ga2 centers, Ga{sup 4+} ions substitute for Ti{sup 4+} ions, but with a preference to one of two electrically distinct crystallographic positions (site selective substitution). The Ga doping eliminates one of the shortcomings of KTP crystals—ionic conductivity of bulk crystals. However, this does not improve significantly the resistance of the crystals to electron and γ-radiation.« less

High-surface Thermally Stable Mesoporous Gallium Phosphates Constituted by Nanoparticles as Primary Building Blocks

DOE Office of Scientific and Technical Information (OSTI.GOV)

V Parvulescu; V Parvulescu; D Ciuparu

In constant, search for micro/mesoporous materials, gallium phosphates, have attracted continued interest due to the large pore size reported for some of these solids in comparison with analogous aluminum phosphates. However up to now, the porosity of gallium phosphates collapsed upon template removal or exposure to the ambient moisture. In the present work, we describe high-surface thermally stable mesoporous gallium phosphates synthesized from gallium propoxide and PCl{sub 3} and different templating agents such as amines (dipropylamine, piperidine and aminopiperidine) and quaternary ammonium salts (C{sub 16}H{sub 33}(CH{sub 3})3NBr and C{sub 16}PyCl). These highly reactive precursors have so far not been usedmore » as gallium and phosphate sources for the synthesis of gallophosphates. Conceptually, our present synthetic procedure is based on the fast formation of gallium phosphate nanoparticles via the reaction of gallium propoxide with PCl{sub 3} and subsequent construction of the porous material with nanoparticles as building blocks. The organization of the gallophosphate nanoparticles in stable porous structures is effected by the templates. Different experimental procedures varying the molar composition of the sol-gel, pH and the pretreatment of gallium precursor were assayed, most of them leading to satisfactory materials in terms of thermal stability and porosity. In this way, a series of gallium phosphates with surface are above 200 m{sup 2} g{sup -1}, and narrow pore size from 3 to 6 nm and remarkable thermal stability (up to 550 C) have been prepared. In some cases, the structure tends to show some periodicity and regularity as determined by XRD. The remarkable stability has allowed us to test the catalytic activity of gallophosphates for the aerobic oxidation of alkylaromatics with notable good results. Our report reopens the interest for gallophosphates in heterogeneous catalysis.« less

Gallium Electromagnetic (GEM) Thrustor Concept and Design

NASA Technical Reports Server (NTRS)

Polzin, Kurt A.; Markusic, Thomas E.

2006-01-01

We describe the design of a new type of two-stage pulsed electromagnetic accelerator, the gallium electromagnetic (GEM) thruster. A schematic illustration of the GEM thruster concept is given in Fig. 1. In this concept, liquid gallium propellant is pumped into the first stage through a porous metal electrode using an electromagneticpump[l]. At a designated time, a pulsed discharge (approx.10-50 J) is initiated in the first stage, ablating the liquid gallium from the porous electrode surface and ejecting a dense thermal gallium plasma into the second state. The presence of the gallium plasma in the second stage serves to trigger the high-energy (approx.500 I), send-stage puke which provides the primary electromagnetic (j x B) acceleration.

Low temperature Voigt effect in the terbium gallium garnet crystal.

PubMed

Akbar, Ali; Khalid, Muhammad Waleed; Anwar, Muhammad Sabieh

2017-11-27

Magnetic linear birefringence and dichroism are investigated for the paramagnetic terbium gallium garnet (TGG) single crystal in the temperature range 8-100 K. The reciprocal nature is confirmed for the linear birefringence. Furthermore a theoretical model is validated that describes the intermixing of linear and circular birefringence. The ellipticity and rotation of the polarization ellipse are investigated in the light of these measurements. These otherwise minuscule magnetically induced effects are amplified at cryogenic temperatures and are determined by a phase-sensitive technique based on the Fourier decomposition of detected signal intensities. The correspondent measurements also allow us to determine the Curie-Weiss constant corroborating the presence of a magnetically frustrated spin system. Additionally we show how the Voigt geometry enables determining the direction of a magnetic field.

An Illumination- and Temperature-Dependent Analytical Model for Copper Indium Gallium Diselenide (CIGS) Solar Cells

DOE PAGES

Sun, Xingshu; Silverman, Timothy; Garris, Rebekah; ...

2016-07-18

In this study, we present a physics-based analytical model for copper indium gallium diselenide (CIGS) solar cells that describes the illumination- and temperature-dependent current-voltage (I-V) characteristics and accounts for the statistical shunt variation of each cell. The model is derived by solving the drift-diffusion transport equation so that its parameters are physical and, therefore, can be obtained from independent characterization experiments. The model is validated against CIGS I-V characteristics as a function of temperature and illumination intensity. This physics-based model can be integrated into a large-scale simulation framework to optimize the performance of solar modules, as well as predict themore » long-term output yields of photovoltaic farms under different environmental conditions.« less

A Comparison of Gallium and Indium Alkoxide Complexes as Catalysts for Ring-Opening Polymerization of Lactide.

PubMed

Kremer, Alexandre B; Andrews, Ryan J; Milner, Matthew J; Zhang, Xu R; Ebrahimi, Tannaz; Patrick, Brian O; Diaconescu, Paula L; Mehrkhodavandi, Parisa

2017-02-06

The impact of the metal size and Lewis acidity on the polymerization activity of group 13 metal complexes was studied, and it was shown that, within the same ligand family, indium complexes are far more reactive and selective than their gallium analogues. To this end, gallium and aluminum complexes supported by a tridentate diaminophenolate ligand, as well as gallium complexes supported by N,N'-ethylenebis(salicylimine)(salen) ligands, were synthesized and compared to their indium analogues. Using the tridentate ligand set, it was possible to isolate the gallium chloride complexes 3 and (±)-4 and the aluminum analogues 5 and (±)-6. The alkoxygallium complex (±)-2, supported by a salen ligand, was also prepared and characterized and, along with the three-component system GaCl 3 /BnOH/NEt 3 , was tested for the ring-opening polymerization of lactide and ε-caprolactone. The polymerization rates and selectivities of both systems were significantly lower than those for the indium analogues. The reaction of (±)-2 with 1 equiv of lactide forms the first insertion product, which is stable in solution and can be characterized at room temperature. In order to understand the differences of the reactivity within the group 13 metal complexes, a Lewis acidity study using triethylphosphine oxide (the Gutmann-Beckett method) was undertaken for a series of aluminum, gallium, and indium halide complexes; this study shows that indium halide complexes are less Lewis acidic than their aluminum and gallium analogues. Density functional theory calculations show that the Mulliken charges for the indium complexes are higher than those for the gallium analogues. These data suggest that the impact of ligands on the reactivity is more significant than that of the metal Lewis acidity.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiong, L. H.; Wang, X. D.; Yu, Q.

Temperature-dependent atomistic structure evolution of liquid gallium (Ga) has been investigated by using in situ high energy X-ray diffraction experiment and ab initio molecular dynamics simulation. Both experimental and theoretical results reveal the existence of a liquid structural change around 1000 K in liquid Ga. Below and above this temperature the liquid exhibits differences in activation energy for selfdiffusion, temperature-dependent heat capacity, coordination numbers, density, viscosity, electric resistivity and thermoelectric power, which are reflected from structural changes of the bond-orientational order parameter Q6, fraction of covalent dimers, averaged string length and local atomic packing. This finding will trigger more studiesmore » on the liquid-to-liquid crossover in metallic melts.« less

Study of sulfur bonding on gallium arsenide (100) surfaces using supercritical fluid extraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cabauy, P.; Darici, Y.; Furton, K.G.

1995-12-01

In the last decades Gallium Arsenide (GaAs) has been considered the semiconductor that will replace silicon because of its direct band gap and high electron mobility. Problems with GaAs Fermi level pinning has halted its widespread use in the electronics industry. The formation of oxides on GaAs results in a high density of surface states that effectively pin the surface Fermi level at the midgap. Studies on sulfur passivation have eliminated oxidation and virtually unpinned the Fermi level on the GaAs surface. This has given rise to interest in sulfur-GaAs bonds. In this presentation, we will discuss the types ofmore » sulfur bonds extracted from a sulfur passivated GaAs (100) using Supercritical Fluid (CO2) Extraction (SFE). SFE can be a valuable tool in the study of chemical speciations on semiconductor surfaces. The variables evaluated to effectively study the sulfur species from the GaAs surface include passivation techniques, supercritical fluid temperatures, densities, and extraction times.« less

Molecular Beam Epitaxial Growth of Iron Nitrides on Zinc-Blende Gallium Nitride(001)

NASA Astrophysics Data System (ADS)

Pak, Jeongihm; Lin, Wenzhi; Chinchore, Abhijit; Wang, Kangkang; Smith, Arthur R.

2008-03-01

Iron nitrides are attractive materials for their high magnetic moments, corrosion, and oxidation resistance. We present the successful epitaxial growth of iron nitride on zinc-blende gallium nitride (c-GaN) in order to develop a novel magnetic transition metal nitride/semiconductor system. First, GaN is grown on magnesium oxide (MgO) substrates having (001) orientation using rf N2-plasma molecular beam epitaxy. Then we grow FeN at substrate temperature of ˜ 210 ^oC up to a thickness of ˜ 10.5 nm. In-situ reflection high-energy electron diffraction (RHEED) is used to monitor the surface during growth. Initial results suggest that the epitaxial relationship is FeN[001] || GaN[001] and FeN[100] || GaN[100]. Work in progress is to investigate the surface using in-situ scanning tunneling microscopy (STM) to reveal the surface structure at atomic scale, as well as to explore more Fe-rich magnetic phases.

Synthesis of GaN by high-pressure ammonolysis of gallium triiodide

NASA Astrophysics Data System (ADS)

Purdy, Andrew P.; Case, Sean; Muratore, Nicole

2003-05-01

The ammonothermal conversion of GaI 3 to both cubic (zinc-blende) and hexagonal GaN was explored in detail. Gallium triiodide, anhydrous NH 3, and in some cases CuI or LiI co-mineralizers, were sealed in quartz tubes and heated in a pressurized autoclave from 300°C to 515°C. At hot-zone temperatures above 430°C, a deposit of mostly c-GaN collects in the upper portion of the tube, and deposits of phase-pure c-GaN were reliably produced on a 50-60 mg scale when CuI co-mineralizer was added. Crystal morphologies of these microcrystalline c-GaN products are highly dependent on growth conditions and range from triangular prisms to triangular plates, dendritic crystals, and irregular particles. Hexagonal GaN products were either in the form of microrods or micron sized prisms. Nanorods, of presumably h-GaN, also formed in some reactions in low yields, intermixed with microcrystalline c-GaN products.

InGaN High-Temperature Photovoltaic Cells

NASA Technical Reports Server (NTRS)

Starikov, David

2015-01-01

This Phase II project developed Indium-Gallium-Nitride (InGaN) photovoltaic cells for high-temperature and high-radiation environments. The project included theoretical and experimental refinement of device structures produced in Phase I as well as modeling and optimization of solar cell device processing. The devices have been tested under concentrated air mass zero (AM0) sunlight, at temperatures from 100 degC to 250 degC, and after exposure to ionizing radiation. The results are expected to further verify that InGaN can be used for high-temperature and high-radiation solar cells. The large commercial solar cell market could benefit from the hybridization of InGaN materials to existing solar cell technology, which would significantly increase cell efficiency without relying on highly toxic compounds. In addition, further development of this technology to even lower bandgap materials for space applications would extend lifetimes of satellite solar cell arrays due to increased radiation hardness. This could be of importance to the Departmentof Defense (DoD) and commercial satellite manufacturers.

Proton Irradiation-Induced Metal Voids in Gallium Nitride High Electron Mobility Transistors

DTIC Science & Technology

2015-09-01

13. ABSTRACT (maximum 200 words) Gallium nitride/aluminum gallium nitride high electron mobility transistors with nickel/ gold (Ni/Au) and...platinum/ gold (Pt/Au) gating are irradiated with 2 MeV protons. Destructive physical analysis revealed material voids underneath the gate finger of the...nickel/ gold (Ni/Au) and platinum/ gold (Pt/Au) gating are irradiated with 2 MeV protons. Destructive physical analysis revealed material voids underneath

Miscut dependent surface evolution in the process of N-polar GaN(000 1 bar) growth under N-rich condition

NASA Astrophysics Data System (ADS)

Krzyżewski, Filip; Załuska-Kotur, Magdalena A.; Turski, Henryk; Sawicka, Marta; Skierbiszewski, Czesław

2017-01-01

The evolution of surface morphology during the growth of N-polar (000 1 bar) GaN under N-rich conditions is studied by kinetic Monte Carlo (kMC) simulations for two substrates miscuts 2° and 4°. The results are compared with experimentally observed surface morphologies of (000 1 bar) GaN layers grown by plasma-assisted molecular beam epitaxy. The proposed kMC two-component model of GaN(000 1 bar) surface where both types of atoms, nitrogen and gallium, attach to the surface and diffuse independently shows that at relatively high rates of the step flow (miscut angle < 2 °) the low mobility of gallium adatoms causes surface instabilities and leads to experimentally observed roughening while for low rates of the step flow (miscut 4°), smooth surface can be obtained. In the presence of almost immobile nitrogen atoms under N-rich conditions crystal growth is realized by the process of two-dimensional island nucleation and coalescence. Larger crystal miscut, lower growth rate or higher temperature results in similar effect of the surface smoothening. We show that the surface also smoothens for the growth conditions with very high N-excess. In the presence of large number of nitrogen atoms the mobility of gallium atoms changes locally thus providing easier coalescence of separated island.

Effect of dopants on annealing performance of silicon solar cells

NASA Technical Reports Server (NTRS)

Scott-Monck, J. A.; Anspaugh, B. E.

1979-01-01

The optimum annealing parameters of time and temperature for producing cell output recovery were established. Devices made from gallium doped and boron doped silicon were investigated. The cells ranged in resistivity from 0.1 to 20 ohm-cm and in thickness from 50 to 250 micrometers. The observations can be explained in a qualitative manner by postulating a pair of competing mechanisms to account for the low temperature reverse annealing seen in most boron and gallium doped silicon solar cells. Still another mechanism dominates at higher temperatures (350 C and greater) to complete this model. One of the mechanisms, defined as B, allows migrators to couple with radiation induced recombination sites thus increasing or enhancing their capture cross sections. This would tend to reduce minority carrier diffusion length. The new recombination complex is postulated to be thermally stable up to temperatures of approximately 350 C.

LETTER TO THE EDITOR: Surface passivation of (100) InP by organic thiols and polyimide as characterized by steady-state photoluminescence

NASA Astrophysics Data System (ADS)

Schvartzman, M.; Sidorov, V.; Ritter, D.; Paz, Y.

2001-10-01

A method for the passivation of indium phosphide, based on thiolated organic self-assembled monolayers (SAMs) that form highly ordered, close-packed structures on the semiconductor surface, is presented. It is shown that the intensity of steady-state photoluminescence (PL) of n-type InP wafers covered with the thiolated SAMs increases significantly (as much as 14-fold) upon their covering with the monolayers. The ease with which one can tailor the outer functional groups of the SAMs provides a way to connect this new class of passivators with standard encapsulators, such as polyimide. Indeed, the PL intensity of SAM-coated InP wafers was not altered upon their overcoating with polyimide, despite the high curing temperature of the polymer (200 °C).

Trends in activity for the oxygen evolution reaction on transition metal (M = Fe, Co, Ni) phosphide pre-catalysts† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c7sc05033j

PubMed Central

Xu, Junyuan; Li, Junjie; Xiong, Dehua; Zhang, Bingsen; Liu, Yuefeng; Wu, Kuang-Hsu; Amorim, Isilda; Li, Wei

2018-01-01

Transition metal phosphides (TMPs) have recently emerged as a new class of pre-catalysts that can efficiently catalyze the oxygen evolution reaction (OER). However, how the OER activity of TMPs varies with the catalyst composition has not been systematically explored. Here, we report the alkaline OER electrolysis of a series of nanoparticulate phosphides containing different equimolar metal (M = Fe, Co, Ni) components. Notable trends in OER activity are observed, following the order of FeP < NiP < CoP < FeNiP < FeCoP < CoNiP < FeCoNiP, which indicate that the introduction of a secondary metal(s) to a mono-metallic TMP substantially boosts the OER performance. We ascribe the promotional effect to the enhanced oxidizing power of bi- and tri-metallic TMPs that can facilitate the formation of MOH and chemical adsorption of OH– groups, which are the rate-limiting steps for these catalysts according to our Tafel analysis. Remarkably, the tri-metallic FeCoNiP pre-catalyst exhibits exceptionally high apparent and intrinsic OER activities, requiring only 200 mV to deliver 10 mA cm–2 and showing a high turnover frequency (TOF) of ≥0.94 s–1 at the overpotential of 350 mV. PMID:29780476

Concept Definition for the Pest Management Component of the Pollution Abatement Management System (PAMS).

DTIC Science & Technology

1982-01-01

able to obtain * Aluminum phosphide, Bromacil, Carbaryl (Sevin), Chlordane, Chlorpyrifos (Oursban), Diazinon, Dichlorovos (DODYP), Malathion, Paraquat...Pentachloro- phenol (PCP), Propoxur (Baygon), Thiram, strychnine/strychnine sulfate, zinc phosphide, and 2,4-D. 10 sufficient data to respond to

Phosphor-Free InGaN White Light Emitting Diodes Using Flip-Chip Technology

PubMed Central

Li, Ying-Chang; Chang, Liann-Be; Chen, Hou-Jen; Yen, Chia-Yi; Pan, Ke-Wei; Huang, Bohr-Ran; Kuo, Wen-Yu; Chow, Lee; Zhou, Dan; Popko, Ewa

2017-01-01

Monolithic phosphor-free two-color gallium nitride (GaN)-based white light emitting diodes (LED) have the potential to replace current phosphor-based GaN white LEDs due to their low cost and long life cycle. Unfortunately, the growth of high indium content indium gallium nitride (InGaN)/GaN quantum dot and reported LED’s color rendering index (CRI) are still problematic. Here, we use flip-chip technology to fabricate an upside down monolithic two-color phosphor-free LED with four grown layers of high indium quantum dots on top of the three grown layers of lower indium quantum wells separated by a GaN tunneling barrier layer. The photoluminescence (PL) and electroluminescence (EL) spectra of this white LED reveal a broad spectrum ranging from 475 to 675 nm which is close to an ideal white-light source. The corresponding color temperature and color rendering index (CRI) of the fabricated white LED, operated at 350, 500, and 750 mA, are comparable to that of the conventional phosphor-based LEDs. Insights of the epitaxial structure and the transport mechanism were revealed through the TEM and temperature dependent PL and EL measurements. Our results show true potential in the Epi-ready GaN white LEDs for future solid state lighting applications. PMID:28772792

Control of Gallium Oxide Growth on Liquid Metal Eutectic Gallium/Indium Nanoparticles via Thiolation.

PubMed

Farrell, Zachary J; Tabor, Christopher

2018-01-09

Eutectic gallium-indium alloy (EGaIn, a room-temperature liquid metal) nanoparticles are of interest for their unique potential uses in self-healing and flexible electronic devices. One reason for their interest is due to a passivating oxide skin that develops spontaneously on exposure to ambient atmosphere which resists deformation and rupture of the resultant liquid particles. It is then of interest to develop methods for control of this oxide growth process. It is hypothesized here that functionalization of EGaIn nanoparticles with thiolated molecules could moderate oxide growth based on insights from the Cabrera-Mott oxidation model. To test this, the oxidation dynamics of several thiolated nanoparticle systems were tracked over time with X-ray photoelectron spectroscopy. These results demonstrate the ability to suppress gallium oxide growth by up to 30%. The oxide progressively matures over a 28 day period, terminating in different final thicknesses as a function of thiol selection. These results indicate not only that thiols moderate gallium oxide growth via competition with oxygen for surface sites but also that different thiols alter the thermodynamics of oxide growth through modification of the EGaIn work function.

Laser ablation synthesis of arsenic-phosphide Asm Pn clusters from As-P mixtures. Laser desorption ionisation with quadrupole ion trap time-of-flight mass spectrometry: The mass spectrometer as a synthesizer.

PubMed

Kubáček, Pavel; Prokeš, Lubomír; Pamreddy, Annapurna; Peña-Méndez, Eladia María; Conde, José Elias; Alberti, Milan; Havel, Josef

2018-05-30

Only a few arsenic phosphides are known. A high potential for the generation of new compounds is offered by Laser Ablation Synthesis (LAS) and when Laser Desorption Ionization (LDI) is coupled with simultaneous Time-Of-Flight Mass Spectrometry (TOFMS), immediate identification of the clusters can be achieved. LAS was used for the generation of arsenic phosphides via laser ablation of phosphorus-arsenic mixtures while quadrupole ion trap time-of-flight mass spectrometry (QIT-TOFMS) was used to acquire the mass spectra. Many new As m P n ± clusters (479 binary and 369 mono-elemental) not yet described in the literature were generated in the gas phase and their stoichiometry determined. The likely structures for some of the observed clusters arbitrary selected (20) were computed by density functional theory (DFT) optimization. LAS is an advantageous approach for the generation of new As m P n clusters, while mass spectrometry was found to be an efficient technique for the determination of cluster stoichiometry. The results achieved might inspire the synthesis of new materials. Copyright © 2018 John Wiley & Sons, Ltd.

Ionothermal synthesis, characterization of a new layered gallium phosphate with an unusual heptamer SBU

NASA Astrophysics Data System (ADS)

Gao, Fan; Huang, Liangliang; Ma, Yike; Jiao, Shufei; Jiang, Yansong; Bi, Yanfeng

2017-10-01

A new layered gallium phosphate Ga3(PO4)4(C2N2H8)·(H2C2N2H8)2·Cl (compound 1), has been ionothermally synthesized in the presence of deep eutectic solvent (DES) comprising mixtures of choline chloride and 2-imidazolidone (IMI). Single-crystal X-ray diffraction analysis reveals that compound 1 shows 2D layered framework with 10-ring windows, which is constructed from unusual heptamer second building units (SBUs). The ethylenediamine (en) units deriving from the decomposition of IMI, play a dual role as bidentate ligands coordinated with 6-fold coordinate gallium atoms and the templates. Additionally, compound 1 shows photoluminescence property in solid state at room temperature.

Emerging Applications of Liquid Metals Featuring Surface Oxides

PubMed Central

2014-01-01

Gallium and several of its alloys are liquid metals at or near room temperature. Gallium has low toxicity, essentially no vapor pressure, and a low viscosity. Despite these desirable properties, applications calling for liquid metal often use toxic mercury because gallium forms a thin oxide layer on its surface. The oxide interferes with electrochemical measurements, alters the physicochemical properties of the surface, and changes the fluid dynamic behavior of the metal in a way that has, until recently, been considered a nuisance. Here, we show that this solid oxide “skin” enables many new applications for liquid metals including soft electrodes and sensors, functional microcomponents for microfluidic devices, self-healing circuits, shape-reconfigurable conductors, and stretchable antennas, wires, and interconnects. PMID:25283244

(Polyfluoroaryl) fluoroanions of aluminum, gallium, and indium of enhanced utility, uses thereof, and products based thereon

DOEpatents

Marks, Tobin J.; Chen, You-Xian

2001-01-01

The (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium are novel weakly coordinating anions which are highly fluorinated. (Polyfluoroaryl)fluoroanions of one such type contain at least one ring substituent other than fluorine. These (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium have greater solubility in organic solvents, or have a coordinative ability essentially equal to or less than that of the corresponding (polyfluoroaryl)fluoroanion of aluminum, gallium, or indium in which the substituent is replaced by fluorine. Another type of new (polyfluoroaryl)fluoroanion of aluminum, gallium, and indium have 1-3 perfluorinated fused ring groups and 2-0 perfluorophenyl groups. When used as a cocatalyst in the formation of novel catalytic complexes with d- or f-block metal compounds having at least one leaving group such as a methyl group, these anions, because of their weak coordination to the metal center, do not interfere in the ethylene polymerization process, while affecting the propylene process favorably, if highly isotactic polypropylene is desired. Thus, the (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium of this invention are useful in various polymerization processes such as are described.

(Polyfluoroaryl) fluoroanions of aluminum, gallium, and indium of enhanced utility, uses thereof, and products based thereon

DOEpatents

Marks, Tobin J.; Chen, You-Xian

2002-01-01

The (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium are novel weakly coordinating anions which are highly fluorinated. (Polyfluoroaryl)fluoroanions of one such type contain at least one ring substituent other than fluorine. These (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium have greater solubility in organic solvents, or have a coordinative ability essentially equal to or less than that of the corresponding (polyfluoroaryl)fluoroanion of aluminum, gallium, or indium in which the substituent is replaced by fluorine. Another type of new (polyfluoroaryl)fluoroanion of aluminum, gallium, and indium have 1-3 perfluorinated fused ring groups and 2-0 perfluorophenyl groups. When used as a cocatalyst in the formation of novel catalytic complexes with d- or f-block metal compounds having at least one leaving group such as a methyl group, these anions, because of their weak coordination to the metal center, do not interfere in the ethylene polymerization process, while affecting the propylene process favorably, if highly isotactic polypropylene is desired. Thus, the (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium of this invention are useful in various polymerization processes such as are described.

The study of aluminium anodes for high power density Al/air batteries with brine electrolytes

NASA Astrophysics Data System (ADS)

Nestoridi, Maria; Pletcher, Derek; Wood, Robert J. K.; Wang, Shuncai; Jones, Richard L.; Stokes, Keith R.; Wilcock, Ian

Aluminium alloys containing small additions of both tin (∼0.1 wt%) and gallium (∼0.05 wt%) are shown to dissolve anodically at high rates in sodium chloride media at room temperatures; current densities >0.2 A cm -2 can be obtained at potentials close to the open circuit potential, ∼-1500 mV versus SCE. The tin exists in the alloys as a second phase, typically as ∼1 μm inclusions (precipitates) distributed throughout the aluminium structure, and anodic dissolution occurs to form pits around the tin inclusions. Although the distribution of the gallium in the alloy could not be established, it is also shown to be critical in the formation of these pits as well as maintaining their activity. The stability of the alloys to open circuit corrosion and the overpotential for high rate dissolution, both critical to battery performance, are shown to depend on factors in addition to elemental composition; both heat treatment and mechanical working influence the performance of the alloy. The correlation between alloy performance and their microstructure has been investigated.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Zhe, E-mail: zhenzhe1201@sina.com; Yang, Lei; Hang, Yin

Highly transparent Dy{sup 3+}-doped terbium gallium garnet (TGG) single crystal was grown by Czochralski (Cz) method. Phase composition of the crystal was tested by XRD measurements. The distribution coefficient of Dy{sup 3+} in the crystal was obtained. The optical and magneto-optical properties were analyzed in detail, and magnetic properties of the Dy{sup 3+}-TGG crystal were studied. The paramagnetic behavior is observed down to 10 K. The as-grown crystal exhibited high optical transmittance, particularly in the visible region. The Faraday rotation was investigated over visible and near-infrared regions (VIS–NIR) at room temperature. The Verdet constants increase at measured wavelengths and highmore » thermal stability was found in Dy{sup 3+}-doped TGG, as compared to the properties of pure TGG, indicating that Dy{sup 3+}-doped crystals are preferable for magneto-active materials used in Faraday devices at VIS–NIR wavelengths. - Graphical abstract: Highly transparent Dy{sup 3+}-doped terbium gallium garnet (TGG) and pure TGG single crystals were grown by Czochralski method. The Dy{sup 3+}-doped TGG possesses 20–30% higher Verdet values in reference to TGG independently on wavelength.« less

Thermal stability of gallium arsenide solar cells

NASA Astrophysics Data System (ADS)

Papež, Nikola; Škvarenina, Ľubomír.; Tofel, Pavel; Sobola, Dinara

2017-12-01

This article summarizes a measurement of gallium arsenide (GaAs) solar cells during their thermal processing. These solar cells compared to standard silicon cells have better efficiency and high thermal stability. However, their use is partly limited due to high acquisition costs. For these reasons, GaAs cells are deployed only in the most demanding applications where their features are needed, such as space applications. In this work, GaAs solar cells were studied in a high temperature range within 30-650 °C where their functionality and changes in surface topology were monitored. These changes were recorded using an electron microscope which determined the position of the defects; using an atomic force microscope we determined the roughness of the surface and an infrared camera that showed us the thermal radiated places of the defected parts of the cell. The electrical characteristics of the cells during processing were determined by its current-voltage characteristics. Despite the occurrence of subtle changes on the solar cell with newly created surface features after 300 °C thermal processing, its current-voltage characteristic remained without a significant change.

Modeling and Simulation of a Gallium Nitride (GaN) Betavoltaic Energy Converter

DTIC Science & Technology

2016-06-01

information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM-YYYY...June 2016 2. REPORT TYPE Final 3. DATES COVERED (From - To) 05/2015–08/2015 4. TITLE AND SUBTITLE Modeling and Simulation of a Gallium Nitride...current battery technology has several drawbacks, such as charge leakage, temperature and environment sensitivity, and finite charge cycles. Radioisotope

Effects of vacuum rapid thermal annealing on the electrical characteristics of amorphous indium gallium zinc oxide thin films

NASA Astrophysics Data System (ADS)

Lee, Hyun-Woo; Cho, Won-Ju

2018-01-01

We investigated the effects of vacuum rapid thermal annealing (RTA) on the electrical characteristics of amorphous indium gallium zinc oxide (a-IGZO) thin films. The a-IGZO films deposited by radiofrequency sputtering were subjected to vacuum annealing under various temperature and pressure conditions with the RTA system. The carrier concentration was evaluated by Hall measurement; the electron concentration of the a-IGZO film increased and the resistivity decreased as the RTA temperature increased under vacuum conditions. In a-IGZO thin-film transistors (TFTs) with a bottom-gate top-contact structure, the threshold voltage decreased and the leakage current increased as the vacuum RTA temperature increased. As the annealing pressure decreased, the threshold voltage decreased, and the leakage current increased. X-ray photoelectron spectroscopy indicated changes in the lattice oxygen and oxygen vacancies of the a-IGZO films after vacuum RTA. At higher annealing temperatures, the lattice oxygen decreased and oxygen vacancies increased, which suggests that oxygen was diffused out in a reduced pressure atmosphere. The formation of oxygen vacancies increased the electron concentration, which consequently increased the conductivity of the a-IGZO films and reduced the threshold voltage of the TFTs. The results showed that the oxygen vacancies and electron concentrations of the a-IGZO thin films changed with the vacuum RTA conditions and that high-temperature RTA treatment at low pressure converted the IGZO thin film to a conductor.

Pulpal thermal responses to an erbium,chromium: YSGG pulsed laser hydrokinetic system.

PubMed

Rizoiu, I; Kohanghadosh, F; Kimmel, A I; Eversole, L R

1998-08-01

Laser systems are known to raise pulpal temperatures when applied to tooth surfaces. Dental biocalcified tissues can be cut with an erbium,chromium:yttrium-scandium-gallium-garnet laser-powered hydrokinetic system. This device is effective for caries removal and cavity preparation in vitro. Pulpal monitoring of temperature changes during hard tissue cutting by a hydrokinetic system have not been reported. This study compared the effects of hydrokinetic system, dry bur, and wet bur tooth cutting on pulpal temperature. In vivo thermocouple intrapulpal measurements were made on cuspid teeth in anesthetized beagle dogs. In vitro measurements were made on extracted human molar teeth preserved in high-salt solution and later rinsed in phosphate-buffered saline (pH 7.4) to simulate in vivo conditions. The hydrokinetic system was compared with conventional air-turbine-powered bur cutting. The hydrokinetic system cuts and bur preparations were randomly made on the buccal surfaces at the cervical one third of the crown and extended until exposure of the pulp was confirmed clinically. Pulpal temperatures associated with the hydrokinetic system either showed no change or decreased by up to 2 degrees C. Wet bur preparations resulted in a 3 degrees to 4 degrees C rise. With dry bur preparations, a 14 degrees C rise in temperature was recorded. Under the conditions of this study, the erbium,chromium:yttrium-scandium-gallium-garnet laser-powered hydrokinetic system, when used for cavity preparation, had no apparent adverse thermal effect as measured in the pulp space.

The sensitivity of the electron transport within bulk zinc-blende gallium nitride to variations in the crystal temperature, the doping concentration, and the non-parabolicity coefficient associated with the lowest energy conduction band valley

DOE Office of Scientific and Technical Information (OSTI.GOV)

Siddiqua, Poppy; O'Leary, Stephen K., E-mail: stephen.oleary@ubc.ca

2016-09-07

Within the framework of a semi-classical three-valley Monte Carlo simulation approach, we analyze the steady-state and transient electron transport that occurs within bulk zinc-blende gallium nitride. In particular, we examine how the steady-state and transient electron transport that occurs within this material changes in response to variations in the crystal temperature, the doping concentration, and the non-parabolicity coefficient associated with the lowest energy conduction band valley. These results are then contrasted with those corresponding to a number of other compound semiconductors of interest.

Room temperature solid-state quantum emitters in the telecom range.

PubMed

Zhou, Yu; Wang, Ziyu; Rasmita, Abdullah; Kim, Sejeong; Berhane, Amanuel; Bodrog, Zoltán; Adamo, Giorgio; Gali, Adam; Aharonovich, Igor; Gao, Wei-Bo

2018-03-01

On-demand, single-photon emitters (SPEs) play a key role across a broad range of quantum technologies. In quantum networks and quantum key distribution protocols, where photons are used as flying qubits, telecom wavelength operation is preferred because of the reduced fiber loss. However, despite the tremendous efforts to develop various triggered SPE platforms, a robust source of triggered SPEs operating at room temperature and the telecom wavelength is still missing. We report a triggered, optically stable, room temperature solid-state SPE operating at telecom wavelengths. The emitters exhibit high photon purity (~5% multiphoton events) and a record-high brightness of ~1.5 MHz. The emission is attributed to localized defects in a gallium nitride (GaN) crystal. The high-performance SPEs embedded in a technologically mature semiconductor are promising for on-chip quantum simulators and practical quantum communication technologies.

^1H NMR studies of the diamagnetic gallium (III) and paramagnetic iron (III) complexes of a chiral macrobicyclic ligand of bicapped tris (binaphtol) type

NASA Astrophysics Data System (ADS)

Baret, P.; Beaujolais, V.; Bougault, C.; Gaude, D.; Pierre, J.-L.

1998-01-01

^1H NMR studies of the diamagnetic gallium (III) and paramagnetic iron (III) complexes of a chiral macrobicyclic ligand of bicapped tris (binaphtol) type are described. The study of the gallium complex emphasizes: (i) that the inversion of the octahedral center is not observed and: (ii) the absence of exchange between free ligand and complex, at room temperature. In the case of the iron complex, assignments of the hyperfine shifted resolved resonances are achieved, based on temperature-behavior studies, which evidence the D3 symmetry of the complex. These assignments are in complete agreement with measured T1 values and proton-to-iron distances obtained from molecular modelling. Les complexes du gallium (III) et du fer (III) d'un ligand macrobicyclique chiral impliquant trois sous-unités de type binaphtol sont étudiés en RMN du proton en solution méthanolique. L'étude du complexe (diamagnétique) du gallium permet de montrer que le complexe : (i) ne subit pas d'inversion de la configuration (Δ/Λ) du site octaédrique et : (ii) qu'il n'y a pas d'échange entre ligand libre et complexe à la température ambiante. L'évolution du spectre du complexe paramagnétique du fer avec la température permet une attribution des protons du ligand et met en évidence la symétrie D3 du complexe. Une bonne corrélation est obtenue entre la distance fer-proton (donnée par la modélisation moléculaire) et le T1 du proton considéré.

A case of accidental fatal aluminum phosphide poisoning involving humans and dogs.

PubMed

Behera, Chittaranjan; Krishna, Karthik; Bhardwaj, Daya Nand; Rautji, Ravi; Kumar, Arvind

2015-05-01

Aluminum phosphide is one of the commonest poisons encountered in agricultural areas, and manner of death in the victims is often suicidal and rarely homicidal or accidental. This paper presents an unusual case, where two humans (owner and housemaid) and eight dogs were found dead in the morning hours inside a room of a house, used as shelter for stray dogs. There was allegation by the son of the owner that his father had been killed. Crime scene visit by forensic pathologists helped to collect vital evidence. Autopsies of both the human victims and the dogs were conducted. Toxicological analysis of viscera, vomitus, leftover food, and chemical container at the crime scene tested positive for aluminum phosphide. The cause of death in both humans and dogs was aluminum phosphide poisoning. Investigation by police and the forensic approach to the case helped in ascertaining the manner of death, which was accidental. © 2015 American Academy of Forensic Sciences.

High-efficiency indium tin oxide/indium phosphide solar cells

NASA Technical Reports Server (NTRS)

Li, X.; Wanlass, M. W.; Gessert, T. A.; Emery, K. A.; Coutts, T. J.

1989-01-01

Improvements in the performance of indium tin oxide (ITO)/indium phosphide solar cells have been realized by the dc magnetron sputter deposition of n-ITO onto an epitaxial p/p(+) structure grown on commercial p(+) bulk substrates. The highest efficiency cells were achieved when the surface of the epilayer was exposed to an Ar/H2 plasma before depositing the bulk of the ITO in a more typical Ar/O2 plasma. With H2 processing, global efficiencies of 18.9 percent were achieved. It is suggested that the excellent performance of these solar cells results from the optimization of the doping, thickness, transport, and surface properties of the p-type base, as well as from better control over the ITO deposition procedure.

Strained quantum well photovoltaic energy converter

NASA Technical Reports Server (NTRS)

Freundlich, Alexandre (Inventor); Renaud, Philippe (Inventor); Vilela, Mauro Francisco (Inventor); Bensaoula, Abdelhak (Inventor)

1998-01-01

An indium phosphide photovoltaic cell is provided where one or more quantum wells are introduced between the conventional p-conductivity and n-conductivity indium phosphide layer. The approach allows the cell to convert the light over a wider range of wavelengths than a conventional single junction cell and in particular convert efficiently transparency losses of the indium phosphide conventional cell. The approach hence may be used to increase the cell current output. A method of fabrication of photovoltaic devices is provided where ternary InAsP and InGaAs alloys are used as well material in the quantum well region and results in an increase of the cell current output.

Sinterless Fabrication Of Contact Pads On InP Devices

NASA Technical Reports Server (NTRS)

Weizer, Victor G.; Fatemi, Navid S.; Korenyi-Both, Andras L.

1995-01-01

Research has shown that with proper choice of material, low-resistance contact pads deposited on solar cells and other devices by improved technique that does not involve sintering. Research directed at understanding mechanisms involved in contact-sintering process has resulted in identification of special group of materials that includes phosphides of gold, silver, and nickel; specifically, Au(2)P(3), AgP(2), and Ni(3)P. Incorporation of phosphide interlayer substantially reduces resistivity between gold current-carrying layer and indium phosphide substrate. Further research indicated only very thin interlayer of any of these compounds needed to obtain low contact resistance, without subjecting contact to destructive sintering process.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mokshin, A. V., E-mail: anatolii.mokshin@mail.ru; Khusnutdinoff, R. M., E-mail: khrm@mail.ru; Novikov, A. G.

The features of the microscopic structure, as well as one-particle and collective dynamics of liquid gallium in the temperature range from T = 313 to 1273 K, are studied on the p = 1.0 atm isobar. Detailed analysis of the data on diffraction of neutrons and X-rays, as well as the results of atomic dynamics simulation, lead to some conclusions about the structure. In particular, for preset conditions, gallium is in the equilibrium liquid phase showing no features of any stable local crystalline clusters. The pronounced asymmetry of the principle peak of the static structure factor and the characteristic “shoulder”more » in its right-hand part appearing at temperatures close to the melting point, which are clearly observed in the diffraction data, are due to the fact that the arrangement of the nearest neighbors of an arbitrary atom in the system is estimated statistically from the range of correlation length values and not by a single value as in the case of simple liquids. Compactly located dimers with a very short bond make a significant contribution to the statistics of nearest neighbors. The temperature dependence of the self-diffusion coefficient calculated from atomic dynamics simulation agrees well with the results obtained from experimental spectra of the incoherent scattering function. Interpolation of the temperature dependence of the self-diffusion coefficient on a logarithmic scale reveals two linear regions with a transition temperature of about 600 K. The spectra of the dynamic structure factor and spectral densities of the local current calculated by simulating the atomic dynamics indicate the existence of acoustic vibrations with longitudinal and transverse polarizations in liquid gallium, which is confirmed by experimental data on inelastic scattering of neutrons and X-rays. It is found that the vibrational density of states is completely reproduced by the generalized Debye model, which makes it possible to decompose the total vibrational motion into individual contributions associated with the formation of acoustic waves with longitudinal and transverse polarizations. Comparison of the heights of the low-frequency component and of the high-frequency peak in the spectral density of vibrational states also indicates a temperature of T ≈ 600 K, at which the diffusion type of one-particle dynamics changes to the vibrational type upon a decrease in temperature. It is demonstrated that the modified Einstein–Stokes relation can be derived using the generalized Debye model.« less

Temperature dependence of carrier capture by defects in gallium arsenide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wampler, William R.; Modine, Normand A.

2015-08-01

This report examines the temperature dependence of the capture rate of carriers by defects in gallium arsenide and compares two previously published theoretical treatments of this based on multi phonon emission (MPE). The objective is to reduce uncertainty in atomistic simulations of gain degradation in III-V HBTs from neutron irradiation. A major source of uncertainty in those simulations is poor knowledge of carrier capture rates, whose values can differ by several orders of magnitude between various defect types. Most of this variation is due to different dependence on temperature, which is closely related to the relaxation of the defect structuremore » that occurs as a result of the change in charge state of the defect. The uncertainty in capture rate can therefore be greatly reduced by better knowledge of the defect relaxation.« less

High-Performance Rh 2 P Electrocatalyst for Efficient Water Splitting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duan, Haohong; Li, Dongguo; Tang, Yan

2017-04-05

Search for active, stable and cost-efficient electrocatalysts for hydrogen production via water splitting could make substantial impact to the energy technologies that do not rely on fossil fuels. Here we report the synthesis of rhodium phosphide electrocatalyst with low metal loading in the form of nanocubes (NCs) dispersed in high surface area carbon (Rh2P/C) by a facile solvo-thermal approach. The Rh2P/C NCs exhibit remarkable performance for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) compared to Rh/C and Pt/C catalysts. The atomic structure of the rhodium phosphide nanocubes was directly observed by annular dark-field scanning transmission electron microscopy (ADF-STEM),more » which revealed phosphorous-rich outermost atomic layer. Combined experimental and computational studies suggest that surface phosphorous plays crucial role in determining the robust catalyst properties.« less

Preliminary Development and Testing of a Self-Injecting Gallium MPD Thruster

NASA Technical Reports Server (NTRS)

Thomas, Robert E.; Burton, Rodney L.; Polzin, Kurt A.

2008-01-01

Discharge current and terminal voltage measurements were performed on a gallium electromagnetic thruster at discharge currents in the range of 20-54 kA. It was found that the arc impedance has a value of 6-7 m(Omega) at peak current. The absence of high-frequency oscillations in the terminal voltage trace indicates lack of the "onset" condition often seen in MPD arcs, suggesting that a sufficient number of charge carriers are present for current conduction. The mass ablated per pulse was not measured experimentally; however the mass flow rate was calculated using an ion current assumption and an anode power balance. Measurement of arc impedance predicts a temperature of 3.5 eV which from Saha equilibrium corresponds to Z = 2.0 - 3.5, and assuming Z = 2 yields an Isp of 3000 s and thrust efficiency of 50%.

Vertically Emitting Indium Phosphide Nanowire Lasers.

PubMed

Xu, Wei-Zong; Ren, Fang-Fang; Jevtics, Dimitars; Hurtado, Antonio; Li, Li; Gao, Qian; Ye, Jiandong; Wang, Fan; Guilhabert, Benoit; Fu, Lan; Lu, Hai; Zhang, Rong; Tan, Hark Hoe; Dawson, Martin D; Jagadish, Chennupati

2018-06-13

Semiconductor nanowire (NW) lasers have attracted considerable research effort given their excellent promise for nanoscale photonic sources. However, NW lasers currently exhibit poor directionality and high threshold gain, issues critically limiting their prospects for on-chip light sources with extremely reduced footprint and efficient power consumption. Here, we propose a new design and experimentally demonstrate a vertically emitting indium phosphide (InP) NW laser structure showing high emission directionality and reduced energy requirements for operation. The structure of the laser combines an InP NW integrated in a cat's eye (CE) antenna. Thanks to the antenna guidance with broken asymmetry, strong focusing ability, and high Q-factor, the designed InP CE-NW lasers exhibit a higher degree of polarization, narrower emission angle, enhanced internal quantum efficiency, and reduced lasing threshold. Hence, this NW laser-antenna system provides a very promising approach toward the achievement of high-performance nanoscale lasers, with excellent prospects for use as highly localized light sources in present and future integrated nanophotonics systems for applications in advanced sensing, high-resolution imaging, and quantum communications.

Susan Habas | NREL

Science.gov Websites

chemical transformations Scalable methods for solution-phase nanomaterials synthesis Production of premium Patents "Metal Phosphide Catalysts and Methods for Making the Same and Uses Thereof," U.S . Patent No. 9,636,664 B1 (2017) "Metal Phosphide Catalysts and Methods for Making the Same and Uses

Effects of site disorder, off-stoichiometry and epitaxial strain on the optical properties of magnetoelectric gallium ferrite.

PubMed

Roy, Amritendu; Mukherjee, Somdutta; Sarkar, Surajit; Auluck, Sushil; Prasad, Rajendra; Gupta, Rajeev; Garg, Ashish

2012-10-31

We present a combined experimental-theoretical study demonstrating the role of site disorder, off-stoichiometry and strain on the optical properties of magnetoelectric gallium ferrite. Optical properties (bandgap, refractive indices and dielectric constants) were experimentally obtained by performing ellipsometric studies over the energy range 0.8-4.2 eV on pulsed laser deposited epitaxial thin films of stoichiometric gallium ferrite with b-axis orientation and the data were compared with theoretical results. Calculations on the ground state structure show that the optical activity in GaFeO(3) arises primarily from O 2p-Fe 3d transitions. Further, inclusion of site disorder and epitaxial strain in the ground state structure significantly improves the agreement between the theory and the room temperature experimental data substantiating the presence of site disorder in the experimentally derived strained GaFeO(3) films at room temperature. We attribute the modification of the ground state optical behavior upon inclusion of site disorder to the corresponding changes in the electronic band structure, especially in Fe 3d states leading to a lowered bandgap of the material.

Phase composition and magnetism of sol-gel synthesized Ga-Fe-O nanograins

NASA Astrophysics Data System (ADS)

Rećko, K.; Waliszewski, J.; Klekotka, U.; Soloviov, D.; Ostapczuk, G.; Satuła, D.; Biernacka, M.; Balasoiu, M.; Basa, A.; Kalska-Szostko, B.; Szymański, K.

2018-02-01

We have succeeded in synthesizing orthorhombic Ga(1-x)Fe(1+x)O3 (-0.05? x?0.5), hexagonal GayFe(2-y)O3 (0?y?1.8) and cubic Ga(1+z)Fe(2-z)O4 (-0.1?z?0.8) nanograins of gallium ferrites using conventional precursors and an organic environment of Pechini scenario under atmospheric-pressure conditions (SG method). Phase composition and homogeneity were analyzed using X-ray diffraction. Small angle neutron scattering disclosed ellipsoidal particle shapes of gallium iron oxides (GFO) crystallizing in orthorhombic (o-GFO) and hexagonal (h-GFO) symmetry and parallelepiped shapes of Ga(1+y)Fe(2-y)O4 (c-GFO) grains. Despite local agglomeration among the magnetic grains, the scanning electron microscopy and transmission electron microscopy images point to faced-elliptical shapes. The Mössbauer spectroscopy with magnetization measurements was carried out in the temperature range of 5-295 K. The analysis of gallium ferrites magnetism demonstrates that iron atoms locate with various probabilities in crystallographic positions and the spontaneous magnetization preserves up to room temperature (RT).

A noise thermometry investigation of the melting point of gallium at the NIM

NASA Astrophysics Data System (ADS)

Zhang, J. T.; Xue, S.

2006-06-01

This paper describes a study of the melting point of gallium with the new NIM Johnson noise thermometer (JNT). The new thermometer adopts the structure of switching correlator and commutator with the reference resistor maintained at the triple point of water. The electronic system of the new thermometer is basically the same as the current JNT, but the preamplifiers have been improved slightly. This study demonstrates that examining the characteristics of the noise signals in the frequency domain is of critical importance in constructing an improved new thermometer, where a power spectral analysis is found to be critical in establishing appropriate grounding for the new thermometer. The new JNT is tested on measurements of the thermodynamic temperature of the melting point of gallium, which give the thermodynamic temperature of 302.9160 K, with an overall integration time of 190 h and a combined standard uncertainty of 9.4 mK. The uncertainty analysis indicates that a standard combined uncertainty of 3 mK could be achieved with the new thermometer over an integration period of 1750 h.

Studies of high temperature ternary phases in mixed-metal-rich early transition metal sulfide and phosphide systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marking, Gregory Allen

1994-01-04

Investigations of ternary mixed early transition metal-rich sulfide and phosphide systems resulted in the discovery of new structures and new phases. A new series of Zr and Hf - group V transition metal - sulfur K-phases was synthesized and crystallographically characterized. When the group V transition metal was Nb or Ta, the unit cell volume was larger than any previously reported K-phase. The presence of adventitious oxygen was determined in two K-phases through a combination of neutron scattering and X-ray diffraction experiments. A compound Hf 10Ta 3S 3 was found to crystallize in a new-structure type similar to the knownmore » gamma brasses. This structure is unique in that it is the only reported "stuffed" gamma-brass type structure. The metal components, Hf and Ta, are larger in size and more electropositive than the metals found in normal gamma brasses (e.g. Cu and Zn) and because of the larger metallic radii, sulfur can be incorporated into the structure where it plays an integral role in stabilizing this phase relative to others. X-ray single-crystal, X-ray powder and neutron powder refinements were performed on this structure. A new structure was found in the ternary Nb-Zr-P system which has characteristics in common with many known early transition metal-rich sulfides, selenides, and phosphides. This structure has the simplest known interconnection of the basic building blocks known for this structural class. Anomalous scattering was a powerful tool for differentiating between Zr and Nb when using Mo Kα X-radiation. The compounds ZrNbP and HfNbP formed in the space group Prima with the simple Co 2Si structure which is among the most common structures found for crystalline solid materials. Solid solution compounds in the Ta-Nb-P, Ta-Zr-P, Nb-Zr-P, Hf-Nb-P, and Hf-Zr-S systems were crystallographically characterized. The structural information corroborated ideas about bonding in metal-rich compounds.« less

Galium Electromagnetic (GEM) Thruster Concept and Design

NASA Technical Reports Server (NTRS)

Polzin, Kurt A.; Markusic, Thomas E.

2005-01-01

We describe the design of a new type of two-stage pulsed electromagnetic accelerator, the gallium electromagnetic (GEM) thruster. A schematic illustration of the GEM thruster concept is given. In this concept, liquid gallium propellant is pumped into the first stage through a porous metal electrode using an electromagnetic pump. At a designated time, a pulsed discharge (approx. 10-50 J) is initiated in the first stage, ablating the liquid gallium from the porous electrode surface and ejecting a dense thermal gallium plasma into the second state. The presence of the gallium plasma in the second stage serves to trigger the high-energy (approx. 500 J), second-stage pulse which provides the primary electromagnetic (j x B) acceleration.

High resolution x-ray diffraction analysis of annealed low-temperature gallium arsenide

NASA Astrophysics Data System (ADS)

Matyi, R. J.; Melloch, M. R.; Woodall, J. M.

1992-05-01

High resolution x-ray diffraction methods have been used to characterize GaAs grown at low substrate temperatures by molecular beam epitaxy and to examine the effects of post-growth annealing on the structure of the layers. Double crystal rocking curves from the as-deposited epitaxial layer show well-defined interference fringes, indicating a high level of structural perfection despite the presence of excess arsenic. Annealing at temperatures from 700 to 900 °C resulted in a decrease in the perpendicular lattice mismatch between the GaAs grown at low temperature and the substrate from 0.133% to 0.016% and a decrease (but not total elimination) of the visibility of the interference fringes. Triple-crystal diffraction scans around the 004 point in reciprocal space exhibited an increase in the apparent mosaic spread of the epitaxial layer with increasing anneal temperature. The observations are explained in terms of the growth of arsenic precipitates in the epitaxial layer.

Noncrystalline structure of Ni-P nanoparticles prepared by liquid pulse discharge.

PubMed

Tan, Yuanyuan; Yu, Hongying; Wu, Zhonghua; Yang, Bin; Gong, Yu; Yan, Shi; Du, Rong; Chen, Zhongjun; Sun, Dongbai

2015-03-01

Noncrystalline nickel phosphide (Ni-P) nanoparticles have drawn great attention due to their high potential as catalysts. However, the structure of noncrystalline Ni-P nanoparticles is still unknown, which may shed light on explaining the catalysis mechanism of the Ni-P nanoparticles. In this paper, noncrystalline Ni-P nanoparticles were synthesized. Their morphology, particle size, element contents, local atomic structures, as well as the catalysis in the thermal decomposition of ammonium perchlorate were studied. The results demonstrate that the as-prepared Ni-P nanoparticles are spherical with an average diameter of about 13.5 nm. The Ni and P contents are, respectively, 78.15% and 21.85%. The noncrystalline nature of the as-prepared Ni-P nanoparticles can be attributed to cross-linkage between P-doping f.c.c.-like Ni centers and Ni3P-like P centers. The locally ordered Ni centers and P centers are the nuclei sites, which can explain well the origin of initial nuclei to form the crystalline phases after high-temperature annealing. The starting temperature of high-temperature decomposition of ammonium perchlorate was found having a significant decrease in the presence of the noncrystalline Ni-P nanoparticles. Therefore, the as-prepared noncrystalline Ni-P nanoparticles can be used as a potential catalyst in the thermal decomposition of ammonium perchlorate.

Intrinsic and metal-doped gallium oxide based high-temperature oxygen sensors for combustion processes

NASA Astrophysics Data System (ADS)

Rubio, Ernesto Javier

Currently, there is enormous interest in research, development and optimization of the combustion processes for energy harvesting. Recent statistical and economic analyses estimated that by improving the coal-based firing/combustion processes in the power plants, savings up to $450-500 million yearly can be achieved. Advanced sensors and controls capable of withstanding extreme environments such as high temperatures, highly corrosive atmospheres, and high pressures are critical to such efficiency enhancement and cost savings. For instance, optimization of the combustion processes in power generation systems can be achieved by sensing, monitoring and control of oxygen, which is a measure of the completeness of the process and can lead to enhanced efficiency and reduced greenhouse gas emissions. However, despite the fact that there exists a very high demand for advanced sensors, the existing technologies suffer from poor 'response and recovery times' and 'long-term stability.' Motivated by the aforementioned technological challenges, the present work was focused on high-temperature (≥700 °C) oxygen sensors for application in power generation systems. The objective of the present work is to investigate nanostructured gallium oxide (2O3) based sensors for oxygen sensing, where we propose to conduct in-depth exploration of the role of refractory metal (tungsten, W, in this case) doping into 2O 3 to enhance the sensitivity, selectivity, stability ("3S" criteria) and reliability of such sensors while keeping cost economical. Tungsten (W) doped gallium oxide (2O3) thin films were deposited via rf-magnetron co-sputtering of W-metal and Ga2O3-ceramic targets. Films were produced by varying the sputtering power applied to the W-target in order to achieve variable W content into 2O3 films while substrate temperature was kept constant at 500 °C. Chemical composition, chemical valence states, microstructure and crystal structure of as-grown and post-annealed W-doped 2O3 films were evaluated as a function of W-content. The structural analyses indicate the formation of monoclinic beta-phase 2O3 in as-grown W-doped 2O3 films for all W-content. Thermally induced secondary phase (W-oxide) formation was observed after the annealing process. Chemical analysis demonstrates the increasing W atomic percentage in the films with increasing sputtering power, whereas the main metallic ionic species for the films are W6+ and Ga3+. Evidence of W interdiffusion due to the annealing process is presented, and the mechanism of diffusion is discussed. Surface morphology of the films is also discussed, and the transition to mesoporous surface is observed after annealing. Finally, the oxygen sensor performance evaluation demonstrated that the W-incorporated 2O3 exhibits improved response time compared to intrinsic 2O3 based oxygen sensors.

Development of orientation-patterned GaP grown on foreign substrates for QPM frequency conversion devices

NASA Astrophysics Data System (ADS)

Vangala, Shivashankar; Peterson, Rita; Snure, Michael; Tassev, Vladimir

2017-02-01

Thick hydride vapor phase epitaxially grown orientation-patterned gallium phosphide (OPGaP) is a leading material for quasi-phase matching (QPM) frequency conversion in the mid- and longwave infrared (IR). This is due to its negligible two-photon absorption (2PA) in the convenient pumping range 1 - 1.7 μm, compared with the 2PA of some traditional QPM materials, such as GaAs. In this paper, we describe homo- and heteroepitaxial growth techniques aimed to produce hundreds of microns thick OPGaP on: 1) OPGaAs templates fabricated using an improved wafer-fusion process; 2) OPGaAs templates fabricated by using a molecular beam epitaxy (MBE) for sublattice polarity inversion, but one with and one without MBE regrowth after the inversion. Some of the advantages of the heteroepitaxial growth of OPGaP on OPGaAs templates include: 1) achieving good domain fidelity as a result of the significantly higher OPGaAs template quality; 2) eliminating the needs of using the poor quality commercially available GaP in the production of thick OPGaP material, and 3) suppression of the additional absorption band between 2 - 4 μm (which is due to incorporation of n-type impurities) and, in general, improvement of the IR transmittance in the entire IR region. Combining the advantages of the two most promising nonlinear materials, GaAs and GaP, will accelerate the development of high power, broadly tunable laser sources in the IR which, in addition, will be offered with higher device quality and at a reasonably lower unit cost.

Synthesis of indium phosphide nanocrystals by sonochemical method and survey of optical properties

NASA Astrophysics Data System (ADS)

Trung, Ho Minh; Duy Thien, Nguyen; Van Vu, Le; Long, Nguyen Ngoc; Hieu, Truong Kim

2013-10-01

Indium phosphide semiconductor materials (InP) have various applications in the field of semiconductor optoelectronics because of its advantages. But the making of this material is difficult due to the very weak chemical activity of In element. In this report we present a simple method to synthesize InP nanocrystals from inorganic precursors such as indium chloride (InCl3), yellow phosphorus (P4), reduction agent NaBH4 at low temperature with the aid of ultrasound. Structural, morphological and optical properties of the formed InP nanocrystals were examined by transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersed X-ray analysis (EDS), Raman scattering, absorption and photoluminscence (PL) spectroscopy. After the surface treatment of InP nanocrystals with liquid hydrofluoric (HF) acid, the luminescence spectra have an enhanced intensity and consist of the peaks in the region from 500 nm to 700 nm. The intensity of these peaks strongly depends on the concentration and etching time of HF. International Workshop on Advanced Materials and Nanotechnology 2012 (IWAMN 2012).

The Effects of Thermal Cycling on Gallium Nitride and Silicon Carbide Semiconductor Devices for Aerospace Use

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Hammoud, Ahmad

2012-01-01

Electronics designed for use in NASA space missions are required to work efficiently and reliably under harsh environment conditions. These Include radiation, extreme temperatures, thermal cycling, to name a few. Preliminary data obtained on new Gallium Nitride and Silicon Carbide power devices under exposure to radiation followed by long term thermal cycling are presented. This work was done in collaboration with GSFC and JPL in support of the NASA Electronic Parts and Packaging (NEPP) Program

Effect of Variation of Silicon Nitride Passivation Layer on Electron Irradiated Aluminum Gallium Nitride/Gallium Nitride HEMT Structures

DTIC Science & Technology

2014-06-19

the AlGaN is unintentionally doped . Figure 2.3. AlGaN/GaN band diagram showing polarization charges. The band diagram in Figure 2.3 shows...intentionally doped as are MESFETS, and the channel gets its electrons from the unintentional doping . There is less Coulomb scattering in the...temperature measurements are often used to provide spatial PL maps of doping and trap densities. Laser excitation (quasi-monochromatic) is

Exploring Cryogenic Focused Ion Beam Milling as a Group III-V Device Fabrication Tool

DTIC Science & Technology

2013-09-01

boiling, triple , and critical points of the elements” in CRC Handbook of Chemistry and Physics, 92nd ed., Boca Raton, FL: CRC press, 2011-2012, p. 4...The most widely used ion source in FIB instruments is a gallium (Ga) liquid metal ion source (LMIS) [4]. Gallium is attractive as an ion source...Figure 3b. EDS spectra were captured at different points across the patterned region of the room temperature milled sample, as indicated in Figure 4

Electric dipole (hyper)polarizabilities of selected X2Y2 and X3Y3 (X = Al, Ga, In and Y = P, As): III-V semiconductor clusters. An ab initio comparative study.

PubMed

Karamanis, Panaghiotis; Pouchan, Claude; Leszczynski, Jerzy

2008-12-25

A systematic ab initio comparative study of the (hyper)polarizabilities of selected III-V stoichiometric semiconductor clusters has been carried out. Our investigation focuses on the ground state structures of the dimers and on two dissimilar trimer configurations of aluminum, gallium, indium phosphide and arsenide. The basis set effect on both the polarizabilities and hyperpolarizabilities of the studied systems has been explicitly taken into account relying on the augmented correlation consistent aug-cc-pVnZ (n = D, T, Q, and 5) basis sets series. In addition, a rough estimation of the effects of the relativistic effects on the investigated properties is provided by extension of the study to include calculations performed with relativistic electron core potentials (or pseudopotentials). Electron correlation effects have been estimated utilizing methods of increasing predictive reliability, e.g., the Møller-Plesset many body perturbation theory and the couple cluster approach. Our results reveal that in the considered semiconductor species the Group III elements (Al, Ga, In) play a vital role on the values of their relative (hyper)polarizability. At all levels of theory employed the most hyperpolarizable clusters are the indium derivatives while the aluminum arsenide clusters also exhibit high, comparable hyperpolarizabilities. The less hyperpolarizable species are those composed of gallium and this is associated with the strong influence of the nuclear charge on the valence electrons of Ga due to the poor shielding that is provided by the semicore d electrons. In addition, the analysis of the electronic structure and the hyperpolarizability magnitudes reveals that clusters, in which their bonding is characterized by strong electron transfer from the electropositive to the electronegative atoms, are less hyperpolarizable than species in which the corresponding electron transfer is weaker. Lastly, from the methodological point of view our results point out that the hyperpolarizabilities of those species converge when an augmented triple-zeta quality basis set is used and, also, that the second order Møller-Plesset approximation (MP2) overestimates considerably their second hyperpolarizabilities with respect to the highest level of coupled cluster theory applied in this study (CCSD(T)).

Black-tailed prairie dog populations one year after treatment with rodenticides

Treesearch

Anthony D. Apa; Daniel W. Uresk; Raymond L. Linder

1990-01-01

Three rodenticide treatments, zinc phosphide with prebait, strychnine with prebait, and strychnine without prebait, were applied to black-tailed prairie dog (Cynomys ludovicianus) colonies in west central South Dakota. Results were compared immediately posttreatment and for one year after application. Zinc phosphide was the most effective for...

Electron transport in zinc-blende wurtzite biphasic gallium nitride nanowires and GaNFETs

DOE PAGES

Jacobs, Benjamin W.; Ayres, Virginia M.; Stallcup, Richard E.; ...

2007-10-19

Two-point and four-point probe electrical measurements of a biphasic gallium nitride nanowire and current–voltage characteristics of a gallium nitride nanowire based field effect transistor are reported. The biphasic gallium nitride nanowires have a crystalline homostructure consisting of wurtzite and zinc-blende phases that grow simultaneously in the longitudinal direction. There is a sharp transition of one to a few atomic layers between each phase. Here, all measurements showed high current densities. Evidence of single-phase current transport in the biphasic nanowire structure is discussed.

Reliability study of refractory gate gallium arsenide MESFETS

NASA Technical Reports Server (NTRS)

Yin, J. C. W.; Portnoy, W. M.

1981-01-01

Refractory gate MESFET's were fabricated as an alternative to aluminum gate devices, which have been found to be unreliable as RF power amplifiers. In order to determine the reliability of the new structures, statistics of failure and information about mechanisms of failure in refractory gate MESFET's are given. Test transistors were stressed under conditions of high temperature and forward gate current to enhance failure. Results of work at 150 C and 275 C are reported.

Reliability study of refractory gate gallium arsenide MESFETS

NASA Astrophysics Data System (ADS)

Yin, J. C. W.; Portnoy, W. M.

Refractory gate MESFET's were fabricated as an alternative to aluminum gate devices, which have been found to be unreliable as RF power amplifiers. In order to determine the reliability of the new structures, statistics of failure and information about mechanisms of failure in refractory gate MESFET's are given. Test transistors were stressed under conditions of high temperature and forward gate current to enhance failure. Results of work at 150 C and 275 C are reported.

Gallium nitrate: effects on cartilage during limb regeneration in the axolotl, Ambystoma mexicanum.

PubMed

Tassava, Roy A; Mendenhall, Luciara; Apseloff, Glen; Gerber, Nicholas

2002-09-01

Gallium nitrate, a drug shown to have efficacy in Paget's disease of bone, hypercalcemia of malignancy, and a variety of experimental autoimmune diseases, also inhibits the growth of some types of cancer. We examined dose and timing of administration of gallium nitrate on limb regeneration in the Mexican axolotl, Ambystoma mexicanum. Administered by intraperitoneal injection, gallium nitrate inhibited limb regeneration in a dose-dependent manner. Gallium nitrate initially suppressed epithelial wound healing and subsequently distorted both anterior-posterior and proximo-distal chondrogenic patterns. Gallium nitrate given at three days after amputation severely inhibited regeneration at high doses (6.25 mg/axolotl) and altered the normal patterning of the regenerates at low doses (3.75 mg/axolotl). Administration of 6.25 mg of gallium nitrate at four or 14 days prior to amputation also inhibited regeneration. In amputated limbs of gallium-treated axolotls, the chondrocytes were lost from inside the radius/ulna. Limbs that regenerated after gallium treatment was terminated showed blastema formation preferentially over the ulna. New cartilage of the regenerate often attached to the sides of the existing radius/ulna proximally into the stump and less so to the distal cut ends. J. Exp. Zool. 293:384-394, 2002. Copyright 2002 Wiley-Liss, Inc.

Mechanical strength and tribological behavior of ion-beam deposited boron nitride films on non-metallic substrates

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa; Buckley, Donald H.; Pouch, John J.; Alterovitz, Samuel A.; Sliney, Harold E.

1987-01-01

An investigation was conducted to examine the mechanical strength and tribological properties of boron nitride (BN) films ion-beam deposited on silicon (Si), fused silica (SiO2), gallium arsenide (GaAs), and indium phosphide (InP) substrates in sliding contact with a diamond pin under a load. The results of the investigation indicate that BN films on nonmetallic substrates, like metal films on metallic substrates, deform elastically and plastically in the interfacial region when in contact with a diamond pin. However, unlike metal films and substrates, BN films on nonmetallic substrates can fracture when they are critically loaded. Not only does the yield pressure (hardness) of Si and SiO2 substrates increase by a factor of 2 in the presence of a BN film, but the critical load needed to fracture increases as well. The presence of films on the brittle substrates can arrest crack formation. The BN film reduces adhesion and friction in the sliding contact. BN adheres to Si and SiO2 and forms a good quality film, while it adheres poorly to GaAs and InP. The interfacial adhesive strengths were 1 GPa for a BN film on Si and appreciably higher than 1 GPa for a BN film on SiO2.

Mechanical strength and tribological behavior of ion-beam-deposited boron nitride films on non-metallic substrates

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa; Pouch, John J.; Alterovitz, Samuel A.; Sliney, Harold E.; Buckley, Donald H.

1987-01-01

An investigation was conducted to examine the mechanical strength and tribological properties of boron nitride (BN) films ion-beam deposited on silicon (Si), fused silica (SiO2), gallium arsenide (GaAs), and indium phosphide (InP) substrates in sliding contact with a diamond pin under a load. The results of the investigation indicate that BN films on nonmetallic substrates, like metal films on metallic substrates, deform elastically and plastically in the interfacial region when in contact with a diamond pin. However, unlike metal films and substrates, BN films on nonmetallic substrates can fracture when they are critically loaded. Not only does the yield pressure (hardness) of Si and SiO2 substrates increase by a factor of 2 in the presence of a BN film, but the critical load needed to fracture increases as well. The presence of films on the brittle substrates can arrest crack formation. The BN film reduces adhesion and friction in the sliding contact. BN adheres to Si and SiO2 and forms a good quality film, while it adheres poorly to GaAs and InP. The interfacial adhesive strengths were 1 GPa for a BN film on Si and appreciably higher than 1 GPa for a BN film on SiO2.

Measurement of body temperature in adult patients: comparative study of accuracy, reliability and validity of different devices.

PubMed

Rubia-Rubia, J; Arias, A; Sierra, A; Aguirre-Jaime, A

2011-07-01

We compared a range of alternative devices with core body temperature measured at the pulmonary artery to identify the most valid and reliable instrument for measuring temperature in routine conditions in health services. 201 patients from the intensive care unit of the Candelaria University Hospital, Canary Islands, admitted to hospital between April 2006 and July 2007. All patients (or their families) gave informed consent. Readings from gallium-in-glass, reactive strip and digital in axilla, infra-red ear and frontal thermometers were compared with the pulmonary artery core temperature simultaneously. External factors suspected of having an influence on the differences were explored. The cut-off point readings for each thermometer were fixed for the maximum negative predictive value in comparison with the core temperature. The validity, reliability, accuracy, external influence, the waste they generated, ease of use, speed, durability, security, comfort and cost of each thermometer was evaluated. An ad hoc overall valuation score was obtained from these parameters for each instrument. For an error of ± 0.2°C and concordance with respect to fever, the gallium-in-glass thermometer gave the best results. The largest area under the receiver operating characteristic (ROC) curve is obtained by the digital axillar thermometer with probe (0.988 ± 0.007). The minimum difference between readings was given by the infrared ear thermometer, in comparison with the core temperature (-0.1 ± 0.3°C). Age, weight, level of conscience, male sex, environmental temperature and vaso-constrictor medication increases the difference in the readings and fever treatment reduces it, although this is not the same for all thermometers. The compact digital axillar thermometer and the digital thermometer with probe obtained the highest overall valuation score. If we only evaluate the aspects of validity, reliability, accuracy and external influence, the best thermometer would be the gallium-in-glass after 12 min. The gallium-in-glass thermometer is less accurate after only 5 min in comparison with the reading taken after being placed for 12 min. If we add the evaluation of waste production, ease-of-use, speed, durability, security, patient comfort and costs, the thermometers that obtain the highest score are the compact digital and digital with probe in right axilla. Copyright © 2010 Elsevier Ltd. All rights reserved.

Temperature-Dependent Compensation and Optical Quenching by Thermal Oxygen Donors in Germanium

NASA Technical Reports Server (NTRS)

Watson, D.; Guptill, M.; Huffman, J.; Krabach, T.; Raines, S.

1994-01-01

Photothermal ionization spectroscopy of germanium, doped in the impurity-band conduction range with gallium acceptors and with thermal oxygen donors, reveals that the donors and acceptors compensate each other at temperatures higher than about 5K, but that the impurities coexist as neutral donors and acceptors at lower temperatures.

(Polyfluoroaryl)fluoroanions of aluminum, gallium, and indium of enhanced utility, uses thereof, and products based thereon

DOEpatents

Marks, Tobin J.; Chen, You-Xian

2001-01-01

The (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium are novel weakly coordinating anions which are are highly fluorinated. (Polyfluoroaryl)fluoroanions of one such type contain at least one ring substituent other than fluorine. These (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium have greater solubility in organic solvents, or have a coordinative ability essentially equal to or less than that of the corresponding (polyfluoroaryl)fluoroanion of aluminum, gallium, or indium in which the substituent is replaced by fluorine. Another type of new (polyfluoroaryl)fluoroanion of aluminum, gallium, and indium have 1-3 perfluorinated fused ring groups and 2-0 perfluorophenyl groups. When used as a cocatalyst in the formation of novel catalytic complexes with d- or f-block metal compounds having at least one leaving group such as a methyl group, these anions, because of their weak coordination to the metal center, do not interefere in the ethylene polymerization process, while affecting the the propylene process favorably, if highly isotactic polypropylene is desired. Thus, the (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium of this invention are useful in various polymerization processes such as are described.

Buffer Layer Effects on Tandem InGaAs TPV Devices

NASA Technical Reports Server (NTRS)

Wilt, David M.; Wehrer, Rebecca J.; Maurer, William F.

2004-01-01

Single junction indium gallium arsenide (InGaAs) based TPV devices have demonstrated efficiencies in excess of 20% at radiator temperatures of 1058 C. Modeling suggests that efficiency improvements in single bandgap devices should continue although they will eventually plateau. One approach for extending efficiencies beyond the single bandgap limit is to follow the technique taken in the solar cell field, namely tandem TPV cells. Tandem photovoltaic devices are traditionally composed of cells of decreasing bandgap, connected electrically and optically in series. The incident light impinges upon the highest bandgap first. This device acts as a sieve, absorbing the high-energy photons, while allowing the remainder to pass through to the underlying cell(s), and so on. Tandem devices reduce the energy lost to overexcitation as well as reducing the current density (Jsc). Reduced Jsc results in lower resistive losses and enables the use of thinner and lower doped lateral current conducting layers as well as a higher pitch grid design. Fabricating TPV tandem devices utilizing InGaAs for all of the component cells in a two cell tandem necessitates the inclusion of a buffer layer in-between the high bandgap device (In0.53 Ga0.47As - 0.74eV) and the low bandgap device (In0.66Ga0.34As - 0.63eV) to accommodate the approximately 1% lattice strain generated due to the change in InGaAs composition. To incorporate only a single buffer layer structure, we have investigated the use of the indium phosphide (InP) substrate as a superstrate. Thus the high-bandgap, lattice- matched device is deposited first, followed by the buffer structure and the low-bandgap cell. The near perfect transparency of the high bandgap (1.35eV) iron-doped InP permits the device to be oriented such that the light enters through the substrate. In this paper we examine the impact of the buffer layer on the underlying lattice-matched InGaAs device. 0.74eV InGaAs devices were produced in a variety of configurations both with and without buffer layers. All structures were characterized by reciprocal space x-ray diffraction to determine epilayer composition and residual strain. Electrical characterization of the devices was performed to examine the effect of the buffer on the device performance. The effect of the buffer structure depends upon where it is positioned. When near the emitter region, a 2.6x increase in dark current was measured, whereas no change in dark current was observed when it was near the base region.

Synthesis and Structural characterization of β-ketoiminate-stabilized gallium hydrides for chemical vapor deposition applications.

PubMed

Marchand, Peter; Pugh, David; Parkin, Ivan P; Carmalt, Claire J

2014-08-11

Bis-β-ketoimine ligands of the form [(CH2 )n {N(H)C(Me)CHC(Me)O}2 ] (L(n) H2 , n=2, 3 and 4) were employed in the formation of a range of gallium complexes [Ga(L(n) )X] (X=Cl, Me, H), which were characterised by NMR spectroscopy, mass spectrometry and single-crystal X-ray diffraction analysis. The β-ketoimine ligands have also been used for the stabilisation of rare gallium hydride species [Ga(L(n) )H] (n=2 (7); n=3 (8)), which have been structurally characterised for the first time, confirming the formation of five-coordinate, monomeric species. The stability of these hydrides has been probed through thermal analysis, revealing stability at temperatures in excess of 200 °C. The efficacy of all the gallium β-ketoiminate complexes as molecular precursors for the deposition of gallium oxide thin films by chemical vapour deposition (CVD) has been investigated through thermogravimetric analysis and deposition studies, with the best results being found for a bimetallic gallium methyl complex [L(3) {GaMe2 }2 ] (5) and the hydride [Ga(L(3) )H] (8). The resulting films (F5 and F8, respectively) were amorphous as-deposited and thus were characterised primarily by XPS, EDXA and SEM techniques, which showed the formation of stoichiometric (F5) and oxygen-deficient (F8) Ga2 O3 thin films. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development of Fixed-Point Cells at the SMU

NASA Astrophysics Data System (ADS)

Ďuriš, S.; Ranostaj, J.; Palenčár, R.

2008-06-01

One of the research programs realized at the thermometry laboratory of the Slovak Institute of Metrology (SMU) in recent years has focused on the development of fixed-point cells. In the frame of this research, several primary cells for realization of the International Temperature Scale of 1990 (ITS-90) and several secondary cells for industrial thermometer calibrations were built and studied. This article discusses primary cells for the gallium and mercury fixed points and miniature cells for the zinc point that were developed at the SMU. Information about the cell designs is provided, the materials that were used are specified, and the procedures for their manufacture are described. Briefly, the realization of the fixed points of mercury, gallium, and zinc by using these cells is also described. Many experiments were carried out to study the characteristics of these cells. One of the gallium cells was compared with the circulating transfer cell during the key comparison CCT-K3, and it and the mercury cell were used for the EUROMET Project No. 552. The results of the experiments together with the results of the comparisons show the high quality of these cells. Secondary zinc-point cells were compared against SMU primary zinc-point cells. The comparison shows agreement within 0.12 mK.

Growth of 1.5 micron gallium indium nitrogen arsenic antimonide vertical cavity surface emitting lasers by molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Wistey, Mark Allan

Fiber optics has revolutionized long distance communication and long haul networks, allowing unimaginable data speeds and noise-free telephone calls around the world for mere pennies per hour at the trunk level. But the high speeds of optical fiber generally do not extend to individual workstations or to the home, in large part because it has been difficult and expensive to produce lasers which emitted light at wavelengths which could take advantage of optical fiber. One of the most promising solutions to this problem is the development of a new class of semiconductors known as dilute nitrides. Dilute nitrides such as GaInNAs can be grown directly on gallium arsenide, which allows well-established processing techniques. More important, gallium arsenide allows the growth of vertical-cavity surface-emitting lasers (VCSELs), which can be grown in dense, 2D arrays on each wafer, providing tremendous economies of scale for manufacturing, testing, and packaging. Unfortunately, GaInNAs lasers have suffered from what has been dubbed the "nitrogen penalty," with high thresholds and low efficiency as the fraction of nitrogen in the semiconductor was increased. This thesis describes the steps taken to identify and essentially eliminate the nitrogen penalty. Protecting the wafer surface from plasma ignition, using an arsenic cap, greatly improved material quality. Using a Langmuir probe, we further found that the nitrogen plasma source produced a large number of ions which damaged the wafer during growth. The ions were dramatically reduced using deflection plates. Low voltage deflection plates were found to be preferable to high voltages, and simulations showed low voltages to be adequate for ion removal. The long wavelengths from dilute nitrides can be partly explained by wafer damage during growth. As a result of these studies, we demonstrated the first CW, room temperature lasers at wavelengths beyond 1.5mum on gallium arsenide, and the first GaInNAs(Sb) VCSELs beyond 1.31mum: 1.46mum. These techniques offer the promise of inexpensive, high speed fiber networking.

Self-assembly of single "square" quantum rings in gold-free GaAs nanowires.

PubMed

Zha, Guowei; Shang, Xiangjun; Su, Dan; Yu, Ying; Wei, Bin; Wang, Li; Li, Mifeng; Wang, Lijuan; Xu, Jianxing; Ni, Haiqiao; Ji, Yuan; Sun, Baoquan; Niu, Zhichuan

2014-03-21

Single nanostructures embedded within nanowires (NWs) represent one of the most promising technologies for applications in quantum photonics. However, fabrication imperfections and etching-induced defects are inevitable for top-down fabrications, whereas self-assembly bottom-up approaches cannot avoid the difficulties of its stochastic nature and are limited to restricted heterogeneous material systems. Here we demonstrate the versatile self-assembly of single "square" quantum rings (QR) on the sidewalls of gold-free GaAs NWs for the first time. By tuning the deposition temperature, As overpressure and amount of gallium-droplets, we were able to control the density and morphology of the structure, yielding novel single quantum dots, QR, coupled QRs, and nano-antidots. A proposed model based on a strain-driven, transport-dependent nucleation of gallium droplets at high temperature accounts for the formation mechanism of these structures. We achieved a single-QR-in-NW structure, of which the optical properties were analyzed using micro-photoluminescence at 10 K and a spatially resolved cathodoluminescence technique at 77 K. The spectra show sharp discrete peaks; of these peaks, the narrowest linewidth (separation) was 578 μeV (1-3 meV), reflecting the quantized nature of the ring-type electronic states.

Two-stage magnetic refrigerator for astronomical applications with reservoir temperatures above 4 K

NASA Astrophysics Data System (ADS)

Hagmann, C.; Richards, P. L.

We propose a novel adiabatic demagnetization refrigerator (ADR) to produce temperatures as low as 100 mK starting from a high temperature reservoir between 4 and 8 K. The high temperature reservoir for the ADR can be provided by a mechanical cooler or an unpumped liquid helium bath. This refrigerator can be used to cool bolometric infrared detectors for low background astronomy from mountain tops, balloons or satellites, as well as to cool cryogenic X-ray detectors. The two-stage ADR consists of a single magnet with a paramagnetic chromic caesium alum (CCA) salt pill to produce the low temperature and paramagnetic gadolinium gallium garnet (GGG) as the first stage to intercept heat from the high temperature reservoir. Thermal contact between the paramagnets and the reservoir during magnetization is made with a mechanical heat switch. The ADR is suspended with Kevlar cords under tension for high mechanical stiffness and low parasitic heat leak. In a single cycle, the ADR maintains a temperature of 100 mK for 10-100 h. This time depends strongly on the magnetic field and reservoir temperature but not on the volume of the paramagnetic material as long as the heat leak is dominated by the suspension.

Gallium Electromagnetic (GEM) Thruster Performance Measurements

NASA Technical Reports Server (NTRS)

Thomas, Robert E.; Burton, Rodney L.; Polzin, K. A.

2009-01-01

Discharge current, terminal voltage, and mass bit measurements are performed on a coaxial gallium electromagnetic thruster at discharge currents in the range of 7-23 kA. It is found that the mass bit varies quadratically with the discharge current which yields a constant exhaust velocity of 20 km/s. Increasing the electrode radius ratio of the thruster from to 2.6 to 3.4 increases the thruster efficiency from 21% to 30%. When operating with a central gallium anode, macroparticles are ejected at all energy levels tested. A central gallium cathode ejects macroparticles when the current density exceeds 3.7 10(exp 8) A/square m . A spatially and temporally broad spectroscopic survey in the 220-520 nm range is used to determine which species are present in the plasma. The spectra show that neutral, singly, and doubly ionized gallium species are present in the discharge, as well as annular electrode species at higher energy levels. Axial Langmuir triple probe measurements yield electron temperatures in the range of 0.8-3.8 eV and electron densities in the range of 8 x 10(exp )20 to 1.6 x 10(exp 21) m(exp -3) . Triple probe measurements suggest an exhaust plume with a divergence angle of 9 , and a completely doubly ionized plasma at the ablating thruster cathode.

Low Noise Amplifiers for 140 Ghz Wide-Band Cryogenic Receivers

NASA Technical Reports Server (NTRS)

Larkoski, Patricia V.; Kangaslahti, Pekka; Samoska, Lorene; Lai, Richard; Sarkozy, Stephen

2013-01-01

We report S-parameter and noise measurements for three different Indium Phosphide 35-nanometer-gate-length High Electron Mobility Transistor (HEMT) Low Noise Amplifier (LNA) designs operating in the frequency range centered on 140 gigahertz. When packaged in a Waveguide Rectangular-6.1 waveguide housing, the LNAs have an average measured noise figure of 3.0 decibels - 3.6 decibels over the 122-170 gigahertz band. One LNA was cooled to 20 degrees Kelvin and a record low noise temperature of 46 Kelvin, or 0.64 decibels noise figure, was measured at 152 gigahertz. These amplifiers can be used to develop receivers for instruments that operate in the 130-170 gigahertz atmospheric window, which is an important frequency band for ground-based astronomy and millimeter-wave imaging applications.

Room temperature solid-state quantum emitters in the telecom range

PubMed Central

Bodrog, Zoltán; Adamo, Giorgio; Gali, Adam

2018-01-01

On-demand, single-photon emitters (SPEs) play a key role across a broad range of quantum technologies. In quantum networks and quantum key distribution protocols, where photons are used as flying qubits, telecom wavelength operation is preferred because of the reduced fiber loss. However, despite the tremendous efforts to develop various triggered SPE platforms, a robust source of triggered SPEs operating at room temperature and the telecom wavelength is still missing. We report a triggered, optically stable, room temperature solid-state SPE operating at telecom wavelengths. The emitters exhibit high photon purity (~5% multiphoton events) and a record-high brightness of ~1.5 MHz. The emission is attributed to localized defects in a gallium nitride (GaN) crystal. The high-performance SPEs embedded in a technologically mature semiconductor are promising for on-chip quantum simulators and practical quantum communication technologies. PMID:29670945