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Sample records for gallium nitride materials

  1. Indium gallium nitride multijunction solar cell simulation using silvaco atlas

    OpenAIRE

    Garcia, Baldomero

    2007-01-01

    This thesis investigates the potential use of wurtzite Indium Gallium Nitride as photovoltaic material. Silvaco Atlas was used to simulate a quad-junction solar cell. Each of the junctions was made up of Indium Gallium Nitride. The band gap of each junction was dependent on the composition percentage of Indium Nitride and Gallium Nitride within Indium Gallium Nitride. The findings of this research show that Indium Gallium Nitride is a promising semiconductor for solar cell use. United...

  2. Electrospun Gallium Nitride Nanofibers

    International Nuclear Information System (INIS)

    Melendez, Anamaris; Morales, Kristle; Ramos, Idalia; Campo, Eva; Santiago, Jorge J.

    2009-01-01

    The high thermal conductivity and wide bandgap of gallium nitride (GaN) are desirable characteristics in optoelectronics and sensing applications. In comparison to thin films and powders, in the nanofiber morphology the sensitivity of GaN is expected to increase as the exposed area (proportional to the length) increases. In this work we present electrospinning as a novel technique in the fabrication of GaN nanofibers. Electrospinning, invented in the 1930s, is a simple, inexpensive, and rapid technique to produce microscopically long ultrafine fibers. GaN nanofibers are produced using gallium nitrate and dimethyl-acetamide as precursors. After electrospinning, thermal decomposition under an inert atmosphere is used to pyrolyze the polymer. To complete the preparation, the nanofibers are sintered in a tube furnace under a NH 3 flow. Both scanning electron microscopy and profilometry show that the process produces continuous and uniform fibers with diameters ranging from 20 to a few hundred nanometers, and lengths of up to a few centimeters. X-ray diffraction (XRD) analysis shows the development of GaN nanofibers with hexagonal wurtzite structure. Future work includes additional characterization using transmission electron microscopy and XRD to understand the role of precursors and nitridation in nanofiber synthesis, and the use of single nanofibers for the construction of optical and gas sensing devices.

  3. High Q gallium nitride microring resonators

    DEFF Research Database (Denmark)

    Stassen, Erik; Pu, Minhao; Semenova, Elizaveta

    2017-01-01

    Summary form only given. Gallium nitride (GaN) is a promising material for nonlinear microresonators. It has large intrinsic χ(2) and χ(3), excellent thermal properties and a relatively large bandgap [1] and can be used for example for parametric conversion and frequency doubling [2]. Furthermore...

  4. Gallium-nitride-based field-effect transistors: Key material synthesis and device processing issues

    Science.gov (United States)

    Gaffey, Brendan Martin

    Gallium nitride (GaN) is viewed as an excellent candidate for the fabrication of high-power and high-frequency transistors operating at elevated temperatures, due to its wide bandgap, high electron saturation velocity, high breakdown electric-field strength, and potential for lattice-matched heterojunctions with other group-III nitrides. This thesis focuses on the following three open areas of research important to the eventual commercialization of GaN-based field-effect transistors: (1) metal-organic chemical vapor deposition (MOCVD) of high-mobility, low-doped GaN, (2) n- and p-type conductivity control of GaN through ion implantation and in-situ doping during MOCVD growth, and (3) potential gate insulators deposited on GaN. Parameters affecting the MOCVD growth of GaN, including source quality, buffer-layer thickness, growth temperature, and epitaxial-layer thickness, are explored, and optimum conditions for the MOCVD growth of unintentionally-doped GaN are identified. In addition, electron-density and electron-mobility values extracted from Hall-effect measurements are shown to be misleading indications of material quality for unintentionally-doped GaN, caused by structural non-homogeneity along the direction of growth in theses samples. N- and p-type doping of GaN is also investigated. Silane and Bis(cyclopentadienyl)magnesium are used for in-situ silicon and magnesium doping of GaN during MOCVD growth, respectively. Silicon is demonstrated to be a very effective donor in GaN, allowing for the growth of n-type GaN over a large range of electron densities (10 16--1019 cm-3) with high electron mobilities (maximum of 543 cm2/V·sec). Magnesium doping, while producing p-type conductivity in GaN (maximum p = 2.3 x 1017 cm-3 with a corresponding mu h = 17 cm2/V·sec), demonstrates an anomalous relationship between the Mg incorporation and the hole density. The cause of this behavior is identified as native-defect formation during GaN growth. Ion implantation of Si

  5. Gallium nitride on gallium oxide substrate for integrated nonlinear optics

    KAUST Repository

    Awan, Kashif M.

    2017-11-22

    Gallium Nitride (GaN), being a direct bandgap semiconductor with a wide bandgap and high thermal stability, is attractive for optoelectronic and electronic applications. Furthermore, due to its high optical nonlinearity — the characteristic of all 111-V semiconductors — GaN is also expected to be a suitable candidate for integrated nonlinear photonic circuits for a plethora of apphcations, ranging from on-chip wavelength conversion to quantum computing. Although GaN devices are in commercial production, it still suffers from lack of a suitable substrate material to reduce structural defects like high densities of threading dislocations (TDs), stacking faults, and grain boundaries. These defects significandy deteriorate the optical quality of the epi-grown GaN layer, since they act as non-radiative recombination centers. Recent studies have shown that GaN grown on (−201) β-Gallium Oxide (Ga2O3) has superior optical quality due to a better lattice matching as compared to GaN grown on Sapphire (Al2O3) [1-3]. In this work, we report on the fabrication of GaN waveguides on GaiOj substrate and their optical characterization to assess their feasibihty for efficient four-wave mixing (FWM).

  6. Two-Dimensional Modeling of Aluminum Gallium Nitride/Gallium Nitride High Electron Mobility Transistor

    National Research Council Canada - National Science Library

    Holmes, Kenneth

    2002-01-01

    Gallium Nitride (GaN) High Electron Mobility Transistors (HEMT's) are microwave power devices that have the performance characteristics to improve the capabilities of current and future Navy radar and communication systems...

  7. Solar cell with a gallium nitride electrode

    Science.gov (United States)

    Pankove, Jacques I.

    1979-01-01

    A solar cell which comprises a body of silicon having a P-N junction therein with a transparent conducting N-type gallium nitride layer as an ohmic contact on the N-type side of the semiconductor exposed to solar radiation.

  8. Optical characterization of gallium nitride

    NARCIS (Netherlands)

    Kirilyuk, Victoria

    2002-01-01

    Group III-nitrides have been considered a promising system for semiconductor devices since a few decades, first for blue- and UV-light emitting diodes, later also for high-frequency/high-power applications. Due to the lack of native substrates, heteroepitaxially grown III-nitride layers are usually

  9. Growth of Gallium Nitride Nanorods and Their Coalescence Overgrowth

    Science.gov (United States)

    2012-09-07

    improved to obtain a crack-free and smooth surface. 15. SUBJECT TERMS Gallium Nitride , nano materials, Detector Technology , Electronic Devices...writing [21], focused ion beam [22], holography [23], and nano-imprint [1, 14]. In regularly patterned growth, vertically oriented NRs of uniform...Patterned Sapphire Substrate for Fabricating Vertical Light-emitting Diode,” accepted for publication in IEEE Photonics Technology Letters. 3

  10. Gallium nitride at the millennial transition

    International Nuclear Information System (INIS)

    Pankovo, J.I.

    2000-01-01

    The properties of gallium nitride were uncovered in the early years of exploratory research and endowed with negative electron affinity that could be used to make efficient cold cathodes and even dynodes for electron multipliers. GaN has another property i.e. polar nature of the crystal which makes this material piezo-electric and has non-linear optical properties. The piezo-electric properties led to new piezo electric effect may cause interfacial charge. The non-uniform distribution of acceptors, there is also presence of threading and other dislocation in GaN. Defects reappear where two adjacent overgrowth merge, but the good lateral overgrow region is large enough to make lasers. Injection lasers benefit from strong electrical and optical environment. This was achieved by using quantum wells of InGaN in GaN and this can be doped with rare earth elements to exploit the atomic transition between core levels in these elements. The emission efficiency of electrically excited Er in GaN is nearly temperature incentive from 80K to room temperature. An other application of GaN is as a heterojunction emitter for a bi-polar transistor (HBT) that can operate at high temperatures. (A.B.)

  11. Proton Irradiation-Induced Metal Voids in Gallium Nitride High Electron Mobility Transistors

    Science.gov (United States)

    2015-09-01

    13. ABSTRACT (maximum 200 words) Gallium nitride / aluminum gallium nitride high electron mobility transistors with nickel/gold (Ni/Au) and...Engineering iv THIS PAGE INTENTIONALLY LEFT BLANK v ABSTRACT Gallium nitride / aluminum gallium nitride high electron mobility transistors with...ABBREVIATIONS 2DEG two-dimensional electron gas AlGaN aluminum gallium nitride AlOx aluminum oxide CCD charged coupled device CTE coefficient of

  12. Thermal Plasma Synthesis of Crystalline Gallium Nitride Nanopowder from Gallium Nitrate Hydrate and Melamine

    Directory of Open Access Journals (Sweden)

    Tae-Hee Kim

    2016-02-01

    Full Text Available Gallium nitride (GaN nanopowder used as a blue fluorescent material was synthesized by using a direct current (DC non-transferred arc plasma. Gallium nitrate hydrate (Ga(NO33∙xH2O was used as a raw material and NH3 gas was used as a nitridation source. Additionally, melamine (C3H6N6 powder was injected into the plasma flame to prevent the oxidation of gallium to gallium oxide (Ga2O3. Argon thermal plasma was applied to synthesize GaN nanopowder. The synthesized GaN nanopowder by thermal plasma has low crystallinity and purity. It was improved to relatively high crystallinity and purity by annealing. The crystallinity is enhanced by the thermal treatment and the purity was increased by the elimination of residual C3H6N6. The combined process of thermal plasma and annealing was appropriate for synthesizing crystalline GaN nanopowder. The annealing process after the plasma synthesis of GaN nanopowder eliminated residual contamination and enhanced the crystallinity of GaN nanopowder. As a result, crystalline GaN nanopowder which has an average particle size of 30 nm was synthesized by the combination of thermal plasma treatment and annealing.

  13. Fabrication of Aluminum Gallium Nitride/Gallium Nitride MESFET And It's Applications in Biosensing

    Science.gov (United States)

    Alur, Siddharth

    Gallium Nitride has been researched extensively for the past three decades for its application in Light Emitting Diodes (LED's), power devices and UV photodetectors. With the recent developments in crystal growth technology and the ability to control the doping there has been an increased interest in heterostructures formed between Gallium nitride and it's alloy Aluminium Gallium Nitride. These heterostructures due to the combined effect of spontaneous and piezoelectric effect can form a high density and a high mobility electron gas channel without any intentional doping. This high density electron gas makes these heterostructures ideal to be used as sensors. Gallium Nitride is also chemically very stable. Detection of biomolecules in a fast and reliable manner is very important in the areas of food safety and medical research. For biomolecular detection it is paramount to have a robust binding of the probes on the sensor surface. Therefore, in this dissertation, the fabrication and application of the AlGaN/GaN heterostructures as biological sensors for the detection of DNA and Organophosphate hydrolase enzyme is discussed. In order to use these AlGaN/GaN heterostructures as biological sensors capable of working in a liquid environment photodefinable polydimethyl-siloxane is used as an encapsulant. The immobilization conditions for a robust binding of thiolated DNA and the catalytic receptor enzyme organophosphate hydrolase on gold surfaces is developed with the help of X-ray photoelectron spectroscopy. DNA and OPH are detected by measuring the change in the drain current of the device as a function of time.

  14. Gallium Nitride Schottky betavoltaic nuclear batteries

    International Nuclear Information System (INIS)

    Lu Min; Zhang Guoguang; Fu Kai; Yu Guohao; Su Dan; Hu Jifeng

    2011-01-01

    Research highlights: → Gallium Nitride nuclear batteries with Ni-63 are demonstrated for the first time. → Open circuit voltage of 0.1 V and conversion efficiency of 0.32% have been obtained. → The limited performance is due to thin effective energy deposition layer. → The output power is expected to greatly increase with growing thick GaN films. -- Abstract: Gallium Nitride (GaN) Schottky betavoltaic nuclear batteries (GNBB) are demonstrated in our work for the first time. GaN films are grown on sapphire substrates by metalorganic chemical vapor deposition (MOCVD), and then GaN Schottky diodes are fabricated by normal micro-fabrication process. Nickel with mass number of 63 ( 63 Ni), which emits β particles, is loaded on the GaN Schottky diodes to achieve GNBB. X-ray diffraction (XRD) and photoluminescence (PL) are carried out to investigate the crystal quality for the GaN films as grown. Current-voltage (I-V) characteristics shows that the GaN Schottky diodes are not jet broken down at -200 V due to consummate fabrication processes, and the open circuit voltage of the GNBB is 0.1 V and the short circuit current density is 1.2 nA cm -2 . The limited performance of the GNBB is due to thin effective energy deposition layer, which is only 206 nm to absorb very small partial energy of the β particles because of the relatively high dislocation density and carrier concentration. However, the conversion efficiency of 0.32% and charge collection efficiency (CCE) of 29% for the GNBB have been obtained. Therefore, the output power of the GNBB are expected to greatly increase with growing high quality thick GaN films.

  15. Gallium nitride photocathode development for imaging detectors

    Science.gov (United States)

    Siegmund, Oswald H. W.; Tremsin, Anton S.; Vallerga, John V.; McPhate, Jason B.; Hull, Jeffrey S.; Malloy, James; Dabiran, Amir M.

    2008-07-01

    Recent progress in Gallium Nitride (GaN, AlGaN, InGaN) photocathodes show great promise for future detector applications in Astrophysical instruments. Efforts with opaque GaN photocathodes have yielded quantum efficiencies up to 70% at 120 nm and cutoffs at ~380 nm, with low out of band response, and high stability. Previous work with semitransparent GaN photocathodes produced relatively low quantum efficiencies in transmission mode (4%). We now have preliminary data showing that quantum efficiency improvements of a factor of 5 can be achieved. We have also performed two dimensional photon counting imaging with 25mm diameter semitransparent GaN photocathodes in close proximity to a microchannel plate stack and a cross delay line readout. The imaging performance achieves spatial resolution of ~50μm with low intrinsic background (below 1 event sec-1 cm-2) and reasonable image uniformity. GaN photocathodes with significant quantum efficiency have been fabricated on ceramic MCP substrates. In addition GaN has been deposited at low temperature onto quartz substrates, also achieving substantial quantum efficiency.

  16. Gallium nitride photocathodes for imaging photon counters

    Science.gov (United States)

    Siegmund, Oswald H. W.; Hull, Jeffrey S.; Tremsin, Anton S.; McPhate, Jason B.; Dabiran, Amir M.

    2010-07-01

    Gallium nitride opaque and semitransparent photocathodes provide high ultraviolet quantum efficiencies from 100 nm to a long wavelength cutoff at ~380 nm. P (Mg) doped GaN photocathode layers ~100 nm thick with a barrier layer of AlN (22 nm) on sapphire substrates also have low out of band response, and are highly robust. Opaque GaN photocathodes are relatively easy to optimize, and consistently provide high quantum efficiency (70% at 120 nm) provided the surface cleaning and activation (Cs) processes are well established. We have used two dimensional photon counting imaging microchannel plate detectors, with an active area of 25 mm diameter, to investigate the imaging characteristics of semitransparent GaN photocathodes. These can be produced with high (20%) efficiency, but the thickness and conductivity of the GaN must be carefully optimized. High spatial resolution of ~50 μm with low intrinsic background (~7 events sec-1 cm-2) and good image uniformity have been achieved. Selectively patterned deposited GaN photocathodes have also been used to allow quick diagnostics of optimization parameters. GaN photocathodes of both types show great promise for future detector applications in ultraviolet Astrophysical instruments.

  17. Microstructures of group III-nitrides after implantation with gallium

    International Nuclear Information System (INIS)

    Kench, P.J.

    2001-05-01

    High doses of gallium have been implanted into layers of aluminium nitride (AIN), indium nitride (InN) and amorphous silicon nitride (a-SiN x ) in an attempt to bond gallium with nitrogen and form binary or ternary alloys. The microstructure of the resultant layers have been characterised using, principally, transmission electron microscopy and X-ray photoelectron spectroscopy. The implantation of a high dose of Ga ions into AIN was successful in synthesising a GaN/GaAlN compound. The resultant layers were largely uniform but contained aluminium precipitates near the surface. These precipitates were pure Al and were most common in the region associated with the maximum Ga concentration. Deconvolution of X-ray photoelectron spectroscopy peaks indicated that Ga existed in a number of chemical states, including the nitride. Electron diffraction patterns from the implanted layers were closely indexed to both AIN and GaN. A further N implant was used to reduce the concentration of the aluminium precipitates and increase the concentration of GaN bonds. The yield of Ga-N bonds dramatically increased and a reduction in the concentration of Al precipitates was observed. Laser and thermal annealing was performed on the implanted AIN substrates. The near surface regions of the implanted specimens appeared to free of precipitates and bubbles. Laser annealing did have a noticeable effect on the electrical and optical properties of the layers. After laser annealing the conductivity of the Ga implanted layer was lower, indicating that the quality of the material had improved. PL measurements showed that a new PL peak at 2.6 eV appeared after laser annealing. It has been found that implanting InN with gallium can yield Ga-N bonds. However, Ga implants into InN were not as successful at synthesising GaN compounds as those by implanting Ga into AIN, due to the low thermal stability of InN. The implanted InN layers were very irregular and contained large indium precipitates and

  18. Gallium-Nitride-Based Light-Emitting Diodes

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 20; Issue 7. Gallium-Nitride-Based Light-Emitting Diodes: 2014 Nobel Prize in Physics. Kota V R M Murali Vinayak Bharat Naik Deepanjan Datta. General Article Volume 20 Issue 7 July 2015 pp 605-616 ...

  19. Radiation-induced metastable ordered phase in gallium nitride

    International Nuclear Information System (INIS)

    Ishimaru, Manabu

    2010-01-01

    Energetic particle irradiation is one of the useful ways for realizing metastable phases far from the equilibrium state. In the present study, we performed electron-beam-irradiation into gallium nitride (GaN) with a wurtzite structure and examined its structural changes using transmission electron microscopy. It was found that superlattice Bragg reflections appear in the electron diffraction patterns of the irradiated GaN. This suggests that the wurtzite GaN transforms to another crystalline structure with atomic ordering.

  20. Optical and Micro-Structural Characterization of MBE Grown Indium Gallium Nitride Polar Quantum Dots

    KAUST Repository

    El Afandy, Rami

    2011-07-07

    Gallium nitride and related materials have ushered in scientific and technological breakthrough for lighting, mass data storage and high power electronic applications. These III-nitride materials have found their niche in blue light emitting diodes and blue laser diodes. Despite the current development, there are still technological problems that still impede the performance of such devices. Three-dimensional nanostructures are proposed to improve the electrical and thermal properties of III-nitride optical devices. This thesis consolidates the characterization results and unveils the unique physical properties of polar indium gallium nitride quantum dots grown by molecular beam epitaxy technique. In this thesis, a theoretical overview of the physical, structural and optical properties of polar III-nitrides quantum dots will be presented. Particular emphasis will be given to properties that distinguish truncated-pyramidal III-nitride quantum dots from other III-V semiconductor based quantum dots. The optical properties of indium gallium nitride quantum dots are mainly dominated by large polarization fields, as well as quantum confinement effects. Hence, the experimental investigations for such quantum dots require performing bandgap calculations taking into account the internal strain fields, polarization fields and confinement effects. The experiments conducted in this investigation involved the transmission electron microscopy and x-ray diffraction as well as photoluminescence spectroscopy. The analysis of the temperature dependence and excitation power dependence of the PL spectra sheds light on the carrier dynamics within the quantum dots, and its underlying wetting layer. A further analysis shows that indium gallium nitride quantum dots through three-dimensional confinements are able to prevent the electronic carriers from getting thermalized into defects which grants III-nitrides quantum dot based light emitting diodes superior thermally induced optical

  1. Epitaxially-grown Gallium Nitride on Gallium Oxide substrate for photon pair generation in visible and telecomm wavelengths

    KAUST Repository

    Awan, Kashif M.

    2016-08-11

    Gallium Nitride (GaN), along with other III-Nitrides, is attractive for optoelectronic and electronic applications due to its wide direct energy bandgap, as well as high thermal stability. GaN is transparent over a wide wavelength range from infra-red to the visible band, which makes it suitable for lasers and LEDs. It is also expected to be a suitable candidate for integrated nonlinear photonic circuits for a wide range of applications from all-optical signal processing to quantum computing and on-chip wavelength conversion. Despite its abundant use in commercial devices, there is still need for suitable substrate materials to reduce high densities of threading dislocations (TDs) and other structural defects like stacking faults, and grain boundaries. All these defects degrade the optical quality of the epi-grown GaN layer as they act as non-radiative recombination centers.

  2. Polarity Control and Doping in Aluminum Gallium Nitride

    Science.gov (United States)

    2013-06-01

    Kontrolle der Polarität und Dotierung in Aluminium Gallium Nitrid vorgelegt von Diplom-Physiker Marc Patrick Hoffmann aus Berlin von der...that are either in metalorganic or hydride form. The MOCVD system is specifically designed for AlGaN alloy growth, including pure GaN and AlN. Both...free exciton transitions in nominally undoped GaN samples grown by hydride vapor phase epitaxy (HVPE) were found at 3.478 eV (FXA) and 3.484 eV (FXB

  3. Gallium nitride electrodes for membrane-based electrochemical biosensors.

    Science.gov (United States)

    Schubert, T; Steinhoff, G; von Ribbeck, H-G; Stutzmannn, M; Eickhoff, M; Tanaka, M

    2009-10-01

    We report on the deposition of planar lipid bilayers (supported membranes) on gallium nitride (GaN) electrodes for potential applications as membrane-based biosensors. The kinetics of the lipid membrane formation upon vesicle fusion were monitored by simultaneous measurements of resistance and capacitance of the membrane using AC impedance spectroscopy in the frequency range between 50 mHz and 50 kHz. We could identify a two-step process of membrane spreading and self-healing. Despite its relatively low resistance, the membrane can be modeled by a parallel combination of an ideal resistor and capacitor, indicating that the membrane efficiently blocks the diffusion of ions.

  4. Characterization and Reliability of Vertical N-Type Gallium Nitride Schottky Contacts

    Science.gov (United States)

    2016-09-01

    aluminum / gallium arsenide Schottky diodes,” J. Appl. Phys., vol. 69, no. 10, pp. 7142–7145, May, 1991. 80 THIS PAGE INTENTIONALLY LEFT BLANK...EECP equilibrium of electrochemical potential GaAs gallium arsenide GaN gallium nitride HEMT high-electron mobility transistor HF hydrofluoric acid...only one of the mechanisms [8]-[11]. For high mobility n-type Schottky contacts like Si, gallium arsenide (GaAs), and GaN, thermionic emission is

  5. Optimal indium-gallium-nitride Schottky-barrier thin-film solar cells

    Science.gov (United States)

    Anderson, Tom H.; Lakhtakia, Akhlesh; Monk, Peter B.

    2017-08-01

    A two-dimensional model was developed to simulate the optoelectronic characteristics of indium-gallium-nitride (InξGa1-ξN), thin-film, Schottky-barrier-junction solar cells. The solar cell comprises a window designed to reduce the reflection of incident light, Schottky-barrier and ohmic front electrodes, an n-doped InξGa1-ξN wafer, and a metallic periodically corrugated back-reflector (PCBR). The ratio of indium to gallium in the wafer varies periodically in the thickness direction, and thus the optical and electrical constitutive properties of the alloy also vary periodically. This material nonhomogeneity could be physically achieved by varying the fractional composition of indium and gallium during deposition. Empirical models for indium nitride and gallium nitride, combined with Vegard's law, were used to calculate the optical and electrical constitutive properties of the alloy. The periodic nonhomogeneity aids charge separation and, in conjunction with the PCBR, enables incident light to couple to multiple surface plasmon-polariton waves and waveguide modes. The profile of the resulting chargecarrier-generation rate when the solar cell is illuminated by the AM1.5G spectrum was calculated using the rigorous coupled-wave approach. The steady-state drift-diffusion equations were solved using COMSOL, which employs finite-element methods, to calculate the current density as a function of the voltage. Mid-band Shockley- Read-Hall, Auger, and radiative recombination rates were taken to be the dominant methods of recombination. The model was used to study the effects of the solar-cell geometry and the shape of the periodic material nonhomogeneity on efficiency. The solar-cell efficiency was optimized using the differential evolution algorithm.

  6. Smooth cubic commensurate oxides on gallium nitride

    Energy Technology Data Exchange (ETDEWEB)

    Paisley, Elizabeth A.; Gaddy, Benjamin E.; LeBeau, James M.; Shelton, Christopher T.; Losego, Mark D.; Mita, Seiji; Collazo, Ramón; Sitar, Zlatko; Irving, Douglas L.; Maria, Jon-Paul, E-mail: jpmaria@ncsu.edu [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Biegalski, Michael D.; Christen, Hans M. [Center for Nanophase Materials Science, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

    2014-02-14

    Smooth, commensurate alloys of 〈111〉-oriented Mg{sub 0.52}Ca{sub 0.48}O (MCO) thin films are demonstrated on Ga-polar, c+ [0001]-oriented GaN by surfactant-assisted molecular beam epitaxy and pulsed laser deposition. These are unique examples of coherent cubic oxide|nitride interfaces with structural and morphological perfection. Metal-insulator-semiconductor capacitor structures were fabricated on n-type GaN. A comparison of leakage current density for conventional and surfactant-assisted growth reveals a nearly 100× reduction in leakage current density for the surfactant-assisted samples. HAADF-STEM images of the MCO|GaN interface show commensurate alignment of atomic planes with minimal defects due to lattice mismatch. STEM and DFT calculations show that GaN c/2 steps create incoherent boundaries in MCO over layers which manifest as two in-plane rotations and determine consequently the density of structural defects in otherwise coherent MCO. This new understanding of interfacial steps between HCP and FCC crystals identifies the steps needed to create globally defect-free heterostructures.

  7. Preparation of negative electron affinity gallium nitride photocathode

    Science.gov (United States)

    Qiao, Jianliang; Chang, Benkang; Qian, Yunsheng; Du, Xiaoqing; Zhang, Yijun; Wang, Xiaohui

    2010-10-01

    Negative electron affinity (NEA) Gallium Nitride (GaN) photocathode is an ideal new kind of UV photocathode. NEA GaN photocathode is widely used in such fields as high-performance ultraviolet photoelectric detector, electron beam lithography etc. The preparation of negative electron affinity gallium nitride photocathode relates to the growth technology, the cleaning method, the activation method and the evaluation of photocathode. The mainstream growth technology of GaN photocathode such as metal organic chemistry vapor phase deposits technology, molecule beam epitaxial technology and halide vapor phase epitaxial technology were discussed. The chemical cleaning method and the heat cleaning method for GaN photocathode were given in detail. After the chemical cleaning, the atom clean surface was gotten by a 700 °C heat about 20 minutes in the vacuum system. The activation of GaN photocathode can be realized with only Cs or with Cs/O alternately. Using the activation and evaluation system for NEA photocathode, the photocurrent curve during Cs activation process for GaN photocathode was gotten. The evaluation of photocathode can be done by measuring the quantum efficiency. Employing the UV spectral response measurement instrument, the spectral response and quantum efficiency of NEA GaN photocathode were measured. The measured quantum efficiency of reflection-mode NEA GaN photocathode reached up to 37% at 230 nm.

  8. Variation of crystallinity and stoichiometry in films of gallium oxide, gallium nitride and barium zirconate prepared by means of PLD

    International Nuclear Information System (INIS)

    Brendt, Jochen

    2011-01-01

    Pulsed Laser Deposition (PLD) is an ablation technique for thin film preparation of many materials. The film properties can be well controlled by the process parameters. Therefore, in many cases a given material can be deposited with different properties by changing one or more process parameters. In this thesis thin films of gallium oxide, gallium nitride and barium zirconate were deposited with a large variation in structure and stoichiometry by means of Pulsed Laser Deposition. The characterization of the film crystallinity, phase purity and short range structural order was completed by means of X-ray diffraction and X-ray absorption spectroscopy. The stoichiometry was investigated using electron probe microanalysis. For analyzing the correlation between the structure and stoichiometry with the optical and electrical properties, optical absorption and electrical conductivity measurements were carried out. The investigation of all three material systems showed that very unique properties can be realized when combining an amorphous structure and a non-stoichiometric composition. For example, in amorphous and oxygen deficient gallium oxide an insulator-metal-transition can be induced by partial crystallization of the as prepared phase accomplished by annealing at about 400 C in argon atmosphere (as shown in literature). Furthermore, amorphous and highly non-stoichiometric barium zirconate has the ability to split water molecules to hydrogen and oxygen at room temperature. A detailed analysis of both phenomena has been performed by means of photoemission and transmission electron microscopy in the case of gallium oxide and via X-ray absorption spectroscopy and gas chromatography in the case of barium zirconate.

  9. Potential effects of gallium on cladding materials

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, D.F.; Beahm, E.C.; Besmann, T.M.; DeVan, J.H.; DiStefano, J.R.; Gat, U.; Greene, S.R.; Rittenhouse, P.L.; Worley, B.A.

    1997-10-01

    This paper identifies and examines issues concerning the incorporation of gallium in weapons derived plutonium in light water reactor (LWR) MOX fuels. Particular attention is given to the more likely effects of the gallium on the behavior of the cladding material. The chemistry of weapons grade (WG) MOX, including possible consequences of gallium within plutonium agglomerates, was assessed. Based on the calculated oxidation potentials of MOX fuel, the effect that gallium may have on reactions involving fission products and possible impact on cladding performance were postulated. Gallium transport mechanisms are discussed. With an understanding of oxidation potentials and assumptions of mechanisms for gallium transport, possible effects of gallium on corrosion of cladding were evaluated. Potential and unresolved issues and suggested research and development (R and D) required to provide missing information are presented.

  10. Potential effects of gallium on cladding materials

    International Nuclear Information System (INIS)

    Wilson, D.F.; Beahm, E.C.; Besmann, T.M.; DeVan, J.H.; DiStefano, J.R.; Gat, U.; Greene, S.R.; Rittenhouse, P.L.; Worley, B.A.

    1997-10-01

    This paper identifies and examines issues concerning the incorporation of gallium in weapons derived plutonium in light water reactor (LWR) MOX fuels. Particular attention is given to the more likely effects of the gallium on the behavior of the cladding material. The chemistry of weapons grade (WG) MOX, including possible consequences of gallium within plutonium agglomerates, was assessed. Based on the calculated oxidation potentials of MOX fuel, the effect that gallium may have on reactions involving fission products and possible impact on cladding performance were postulated. Gallium transport mechanisms are discussed. With an understanding of oxidation potentials and assumptions of mechanisms for gallium transport, possible effects of gallium on corrosion of cladding were evaluated. Potential and unresolved issues and suggested research and development (R and D) required to provide missing information are presented

  11. Deep Level Defects in Electron-Irradiated Aluminum Gallium Nitride Grown by Molecular Beam Epitaxy

    National Research Council Canada - National Science Library

    Hogsed, Michael R

    2005-01-01

    Aluminum gallium nitride (AlGaN)-based devices are attractive candidates for integration into future Air Force communication and sensor platforms, including those that must operate in harsh radiation environments...

  12. Micro-Scale Gallium Nitride Pressure Sensors for Advanced Harsh Environment Space Technology

    Data.gov (United States)

    National Aeronautics and Space Administration — The goal of this research is to study the high-temperature response of the 2-dimesional electron gas (2DEG) that occurs at the interface of aluminum gallium nitride...

  13. Broadband 0.25-um Gallium Nitride (GaN) Power Amplifier Designs

    Science.gov (United States)

    2017-08-14

    ARL-TR-8091 ● AUG 2017 US Army Research Laboratory Broadband 0.25-µm Gallium Nitride (GaN) Power Amplifier Designs by John E...return it to the originator. ARL-TR-8091 ● AUG 2017 US Army Research Laboratory Broadband 0.25-µm Gallium Nitride (GaN) Power ...notwithstanding any other provision of law , no person shall be subject to any penalty for failing to comply with a collection of information if it does not display

  14. Gallium Nitride Electrical Characteristics Extraction and Uniformity Sorting

    Directory of Open Access Journals (Sweden)

    Shyr-Long Jeng

    2015-01-01

    Full Text Available This study examined the output electrical characteristics—current-voltage (I-V output, threshold voltage, and parasitic capacitance—of novel gallium nitride (GaN power transistors. Experimental measurements revealed that both enhanced- and depletion-mode GaN field-effect transistors (FETs containing different components of identical specifications yielded varied turn-off impedance; hence, the FET quality was inconsistent. Establishing standardized electrical measurements can provide necessary information for designers, and measuring transistor electrical characteristics establishes its equivalent-circuit model for circuit simulations. Moreover, high power output requires multiple parallel power transistors, and sorting the difference between similar electrical characteristics is critical in a power system. An isolated gate driver detection method is proposed for sorting the uniformity from the option of the turn-off characteristic. In addition, an equivalent-circuit model for GaN FETs is established on the basis of the measured electrical characteristics and verified experimentally.

  15. Modeling and simulation of bulk gallium nitride power semiconductor devices

    Directory of Open Access Journals (Sweden)

    G. Sabui

    2016-05-01

    Full Text Available Bulk gallium nitride (GaN power semiconductor devices are gaining significant interest in recent years, creating the need for technology computer aided design (TCAD simulation to accurately model and optimize these devices. This paper comprehensively reviews and compares different GaN physical models and model parameters in the literature, and discusses the appropriate selection of these models and parameters for TCAD simulation. 2-D drift-diffusion semi-classical simulation is carried out for 2.6 kV and 3.7 kV bulk GaN vertical PN diodes. The simulated forward current-voltage and reverse breakdown characteristics are in good agreement with the measurement data even over a wide temperature range.

  16. Modeling and simulation of bulk gallium nitride power semiconductor devices

    Science.gov (United States)

    Sabui, G.; Parbrook, P. J.; Arredondo-Arechavala, M.; Shen, Z. J.

    2016-05-01

    Bulk gallium nitride (GaN) power semiconductor devices are gaining significant interest in recent years, creating the need for technology computer aided design (TCAD) simulation to accurately model and optimize these devices. This paper comprehensively reviews and compares different GaN physical models and model parameters in the literature, and discusses the appropriate selection of these models and parameters for TCAD simulation. 2-D drift-diffusion semi-classical simulation is carried out for 2.6 kV and 3.7 kV bulk GaN vertical PN diodes. The simulated forward current-voltage and reverse breakdown characteristics are in good agreement with the measurement data even over a wide temperature range.

  17. Electrical and optoelectronic properties of gallium nitride

    International Nuclear Information System (INIS)

    Flannery, Lorraine Barbara

    2002-01-01

    substrates using the CARS25 RF source. The chemical concentration of Mg, [Mg] and the hole density, p H were found to increase both with layer thickness and Mg cell temperature in material grown at 700 deg C. A maximum free hole density, p H and mobility, μ H of 4.8 x 10 17 cm -3 and 10.7 cm 2 V -1 s -1 respectively were obtained for a 2.1 μm layer grown at a Mg cell temperature of 507 deg C. Photoconductive UV detectors were successfully fabricated from the highest quality n and p-type GaN layers grown by MBE on sapphire substrates. The p-type UV devices represented the first Mg doped p-type GaN based UV photoconductive detectors grown on sapphire substrates produced by the MBE growth method. The performances of both the n and p-type detectors were assessed by measurement of their optoelectronic and electrical properties and some conclusions were drawn regarding their operating principles. (author)

  18. Microfabrication in free-standing gallium nitride using UV laser micromachining

    International Nuclear Information System (INIS)

    Gu, E.; Howard, H.; Conneely, A.; O'Connor, G.M.; Illy, E.K.; Knowles, M.R.H.; Edwards, P.R.; Martin, R.W.; Watson, I.M.; Dawson, M.D.

    2006-01-01

    Gallium nitride (GaN) and related alloys are important semiconductor materials for fabricating novel photonic devices such as ultraviolet (UV) light-emitting diodes (LEDs) and vertical cavity surface-emitting lasers (VCSELs). Recent technical advances have made free-standing GaN substrates available and affordable. However, these materials are strongly resistant to wet chemical etching and also, low etch rates restrict the use of dry etching. Thus, to develop alternative high-resolution processing for these materials is increasingly important. In this paper, we report the fabrication of microstructures in free-standing GaN using pulsed UV lasers. An effective method was first developed to remove the re-deposited materials due to the laser machining. In order to achieve controllable machining and high resolution in GaN, machining parameters were carefully optimised. Under the optimised conditions, precision features such as holes (through holes, blind or tapered holes) on a tens of micrometer length scale have been machined. To fabricate micro-trenches in GaN with vertical sidewalls and a flat bottom, different process strategies of laser machining were tested and optimised. Using this technique, we have successfully fabricated high-quality micro-trenches in free-standing GaN with various widths and depths. The approach combining UV laser micromachining and other processes is also discussed. Our results demonstrate that the pulsed UV laser is a powerful tool for fabricating precision microstructures and devices in gallium nitride

  19. Gallium

    Science.gov (United States)

    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

  20. Graphitic Carbon Nitride Materials for Energy Applications

    OpenAIRE

    Belen Jorge, A.; Dedigama, I.; Mansor, N.; Jervis, R.; Corà, F.; McMillan, P. F.; Brett, D.

    2015-01-01

    Polymeric layered carbon nitrides were investigated for use as catalyst support materials for proton exchange membrane fuel cells (PEMFCs) and water electrolyzers (PEMWEs). Three different carbon nitride materials were prepared: a heptazine-based graphitic carbon nitride material (gCNM), poly (triazine) imide carbon nitride intercalated with LiCl component (PTI-Li+Cl-) and boron-doped graphitic carbon nitride (B-gCNM). Following accelerated corrosion testing, all graphitic carbon nitride mate...

  1. Piezoelectric effect on the thermal conductivity of monolayer gallium nitride

    Science.gov (United States)

    Zhang, Jin

    2018-01-01

    Using molecular dynamics and density functional theory simulations, in this work, we find that the heat transport property of the monolayer gallium nitride (GaN) can be efficiently tailored by external electric field due to its unique piezoelectric characteristic. As the monolayer GaN possesses different piezoelectric properties in armchair and zigzag directions, different effects of the external electric field on thermal conductivity are observed when it is applied in the armchair and zigzag directions. Our further study reveals that due to the elastoelectric effect in the monolayer GaN, the external electric field changes the Young's modulus and therefore changes the phonon group velocity. Also, due to the inverse piezoelectric effect, the applied electric field induces in-plane stress in the monolayer GaN subject to a length constraint, which results in the change in the lattice anharmonicity and therefore affects the phonon mean free path. Furthermore, for relatively long GaN monolayers, the in-plane stress may trigger the buckling instability, which can significantly reduce the phonon mean free path.

  2. Schottky Barrier Transport for Multiphase Gallium Nitride Nanowire

    Science.gov (United States)

    Hartz, Steven; Xie, Kan; Liu, Zhun; Ayres, Virginia

    2013-03-01

    Our group has shown that gallium nitride nanowires grown by catalyst-free vapor deposition at 850oC have multiple internal crystalline regions that may be zinc blende or wurtzite phase. Stability is enabled by one or more totally coherent (0001)/(111) internal interfaces. Cross-section HRTEM has further demonstrated that, while the transverse nanowire profile appears triangular, it is actually made up of two or more surface orientations corresponding to the multi-phase internal regions. We present results of a transport investigation of these multiphase nanowires within a nanoFET circuit architecture, focusing on injection from the contacts into the nanowires. Experimental results demonstrated that a variety of surface state derived Schottky barriers could be present at the contact-nanowire interfaces. Transport across the Schottky barriers was modeled using a combined thermionic emission-tunnelling approach, leading to information about barrier height, carrier concentrations, and expected temperature behavior. The experimental and theoretical results indicate that with optimal design taking surface and internal structures into account, high current densities can be supported.

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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 hydrogen 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.

  5. Photoelectrochemical etching of gallium nitride surface by complexation dissolution mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Miao-Rong [Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, 215123 Suzhou (China); University of Chinese Academy of Sciences, 100049 Beijing (China); Hou, Fei; Wang, Zu-Gang; Zhang, Shao-Hui [Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, 215123 Suzhou (China); Changchun University of Science and Technology, 130022 Changchun (China); Pan, Ge-Bo, E-mail: gbpan2008@sinano.ac.cn [Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, 215123 Suzhou (China)

    2017-07-15

    Graphical abstract: GaN surface was etched by 0.3 M EDTA-2Na. The proposed complexation dissolution mechanism can be applicable to almost all neutral etchants under the prerequisite of strong light and electric field. - Highlights: • GaN surface was etched by EDTA-2Na. • GaN may be dissolved into EDTA-2Na by forming Ga–EDTA complex. • We propose the complexation dissolution mechanism for the first time. - Abstract: Gallium nitride (GaN) surface was etched by 0.3 M ethylenediamine tetraacetic acid disodium (EDTA-2Na) via photoelectrochemical etching technique. SEM images reveal the etched GaN surface becomes rough and irregular. The pore density is up to 1.9 × 10{sup 9} per square centimeter after simple acid post-treatment. The difference of XPS spectra of Ga 3d, N 1s and O 1s between the non-etched and freshly etched GaN surfaces can be attributed to the formation of Ga–EDTA complex at the etching interface between GaN and EDTA-2Na. The proposed complexation dissolution mechanism can be broadly applicable to almost all neutral etchants under the prerequisite of strong light and electric field. From the point of view of environment, safety and energy, EDTA-2Na has obvious advantages over conventionally corrosive etchants. Moreover, as the further and deeper study of such nearly neutral etchants, GaN etching technology has better application prospect in photoelectric micro-device fabrication.

  6. Photoelectrochemical etching of gallium nitride surface by complexation dissolution mechanism

    International Nuclear Information System (INIS)

    Zhang, Miao-Rong; Hou, Fei; Wang, Zu-Gang; Zhang, Shao-Hui; Pan, Ge-Bo

    2017-01-01

    Graphical abstract: GaN surface was etched by 0.3 M EDTA-2Na. The proposed complexation dissolution mechanism can be applicable to almost all neutral etchants under the prerequisite of strong light and electric field. - Highlights: • GaN surface was etched by EDTA-2Na. • GaN may be dissolved into EDTA-2Na by forming Ga–EDTA complex. • We propose the complexation dissolution mechanism for the first time. - Abstract: Gallium nitride (GaN) surface was etched by 0.3 M ethylenediamine tetraacetic acid disodium (EDTA-2Na) via photoelectrochemical etching technique. SEM images reveal the etched GaN surface becomes rough and irregular. The pore density is up to 1.9 × 10 9 per square centimeter after simple acid post-treatment. The difference of XPS spectra of Ga 3d, N 1s and O 1s between the non-etched and freshly etched GaN surfaces can be attributed to the formation of Ga–EDTA complex at the etching interface between GaN and EDTA-2Na. The proposed complexation dissolution mechanism can be broadly applicable to almost all neutral etchants under the prerequisite of strong light and electric field. From the point of view of environment, safety and energy, EDTA-2Na has obvious advantages over conventionally corrosive etchants. Moreover, as the further and deeper study of such nearly neutral etchants, GaN etching technology has better application prospect in photoelectric micro-device fabrication.

  7. Layer-by-layer composition and structure of silicon subjected to combined gallium and nitrogen ion implantation for the ion synthesis of gallium nitride

    Energy Technology Data Exchange (ETDEWEB)

    Korolev, D. S.; Mikhaylov, A. N.; Belov, A. I.; Vasiliev, V. K.; Guseinov, D. V.; Okulich, E. V. [Nizhny Novgorod State University (Russian Federation); Shemukhin, A. A. [Moscow State University, Skobeltsyn Institute of Nuclear Physics (Russian Federation); Surodin, S. I.; Nikolitchev, D. E.; Nezhdanov, A. V.; Pirogov, A. V.; Pavlov, D. A.; Tetelbaum, D. I., E-mail: tetelbaum@phys.unn.ru [Nizhny Novgorod State University (Russian Federation)

    2016-02-15

    The composition and structure of silicon surface layers subjected to combined gallium and nitrogen ion implantation with subsequent annealing have been studied by the X-ray photoelectron spectroscopy, Rutherford backscattering, electron spin resonance, Raman spectroscopy, and transmission electron microscopy techniques. A slight redistribution of the implanted atoms before annealing and their substantial migration towards the surface during annealing depending on the sequence of implantations are observed. It is found that about 2% of atoms of the implanted layer are replaced with gallium bonded to nitrogen; however, it is impossible to detect the gallium-nitride phase. At the same time, gallium-enriched inclusions containing ∼25 at % of gallium are detected as candidates for the further synthesis of gallium-nitride inclusions.

  8. Improvement of efficiency in graphene/gallium nitride nanowire on Silicon photoelectrode for overall water splitting

    Science.gov (United States)

    Bae, Hyojung; Rho, Hokyun; Min, Jung-Wook; Lee, Yong-Tak; Lee, Sang Hyun; Fujii, Katsushi; Lee, Hyo-Jong; Ha, Jun-Seok

    2017-11-01

    Gallium nitride (GaN) nanowires are one of the most promising photoelectrode materials due to their high stability in acidic and basic electrolytes, and tunable band edge potentials. In this study, GaN nanowire arrays (GaN NWs) were prepared by molecular beam epitaxy (MBE); their large surface area enhanced the solar to hydrogen conversion efficiency. More significantly, graphene was grown by chemical vapor deposition (CVD), which enhanced the electron transfer between NWs for water splitting and protected the GaN NW surface. Structural characterizations of the prepared composite were performed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The photocurrent density of Gr/GaN NWs exhibited a two-fold increase over pristine GaN NWs and sustained water splitting up to 70 min. These improvements may accelerate possible applications for hydrogen generation with high solar to hydrogen conversion efficiency.

  9. Slot silicon-gallium nitride waveguide in MMI structures based 1x8 wavelength demultiplexer

    Science.gov (United States)

    Ben Zaken, Bar Baruch; Zanzury, Tal; Malka, Dror

    2017-06-01

    We propose a novel 8-channel wavelength multimode interference (MMI) demultiplexer in slot waveguide structures that operated at 1530 nm, 1535 nm, 1540 nm, 1545 nm, 1550 nm, 1555 nm, 1560 nm and 1565 nm wavelengths. Gallium nitride (GaN) surrounded by silicon (Si) was founded as suitable materials for the slot-waveguide structures. The proposed device was designed by seven 1x2 MMI couplers, fourteen S-band and one input taper. Numerical investigations were carried out on the geometrical parameters by using a full vectorial-beam propagation method (FVBPM). Simulation results show that the proposed device can transmit 8-channel that works in the whole C-band (1530- 1565 nm) with low crosstalk ((-19.97)-(-13.77) dB) and bandwidth (1.8-3.6 nm). Thus, the device can be very useful in optical networking systems that work on dense wavelength division multiplexing (DWDM) technology.

  10. Localized surface plasmon resonances in gold nano-patches on a gallium nitride substrate

    International Nuclear Information System (INIS)

    D’Antonio, Palma; Vincenzo Inchingolo, Alessio; Perna, Giuseppe; Capozzi, Vito; Stomeo, Tiziana; De Vittorio, Massimo; Magno, Giovanni; Grande, Marco; Petruzzelli, Vincenzo; D’Orazio, Antonella

    2012-01-01

    In this paper we describe the design, fabrication and characterization of gold nano-patches, deposited on gallium nitride substrate, acting as optical nanoantennas able to efficiently localize the electric field at the metal–dielectric interface. We analyse the performance of the proposed device, evaluating the transmission and the electric field localization by means of a three-dimensional finite difference time domain (FDTD) method. We detail the fabrication protocol and show the morphological characterization. We also investigate the near-field optical transmission by means of scanning near-field optical microscope measurements, which reveal the excitation of a localized surface plasmon resonance at a wavelength of 633 nm, as expected by the FDTD calculations. Such results highlight how the final device can pave the way for the realization of a single optical platform where the active material and the metal nanostructures are integrated together on the same chip. (paper)

  11. Outphasing control of gallium nitride based very high frequency resonant converters

    DEFF Research Database (Denmark)

    Madsen, Mickey Pierre; Knott, Arnold; Andersen, Michael A. E.

    2015-01-01

    and purely resistive loading of the inverters. Combined with a proper design of the inverters that, insures they can achieve zero voltage switching across a wide load range, and gallium nitride FETs for the switching devices, this makes it possible to achieve more than 90% efficiency across most of the input...

  12. Flexible Gallium Nitride for High-Performance, Strainable Radio-Frequency Devices.

    Science.gov (United States)

    Glavin, Nicholas R; Chabak, Kelson D; Heller, Eric R; Moore, Elizabeth A; Prusnick, Timothy A; Maruyama, Benji; Walker, Dennis E; Dorsey, Donald L; Paduano, Qing; Snure, Michael

    2017-12-01

    Flexible gallium nitride (GaN) thin films can enable future strainable and conformal devices for transmission of radio-frequency (RF) signals over large distances for more efficient wireless communication. For the first time, strainable high-frequency RF GaN devices are demonstrated, whose exceptional performance is enabled by epitaxial growth on 2D boron nitride for chemical-free transfer to a soft, flexible substrate. The AlGaN/GaN heterostructures transferred to flexible substrates are uniaxially strained up to 0.85% and reveal near state-of-the-art values for electrical performance, with electron mobility exceeding 2000 cm 2 V -1 s -1 and sheet carrier density above 1.07 × 10 13 cm -2 . The influence of strain on the RF performance of flexible GaN high-electron-mobility transistor (HEMT) devices is evaluated, demonstrating cutoff frequencies and maximum oscillation frequencies greater than 42 and 74 GHz, respectively, at up to 0.43% strain, representing a significant advancement toward conformal, highly integrated electronic materials for RF applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Advanced W-Band Gallium Nitride Monolithic Microwave Integrated Circuits (MMICs) for Cloud Doppler Radar Supporting ACE Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Develop W-band Gallium Nitride (GaN) MMICs to enable the advanced cross-track scanning, dual-frequency Doppler cloud radar concept in support of the...

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

    Science.gov (United States)

    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.

  15. Micromachining and dicing of sapphire, gallium nitride and micro LED devices with UV copper vapour laser

    International Nuclear Information System (INIS)

    Gu, E.; Jeon, C.W.; Choi, H.W.; Rice, G.; Dawson, M.D.; Illy, E.K.; Knowles, M.R.H.

    2004-01-01

    Gallium nitride (GaN) and sapphire are important materials for fabricating photonic devices such as high brightness light emitting diodes (LEDs). These materials are strongly resistant to wet chemical etching and also, low etch rates restrict the use of dry etching. Thus, to develop alternative high resolution processing and machining techniques for these materials is important in fabricating novel photonic devices. In this work, a repetitively pulsed UV copper vapour laser (255 nm) has been used to machine and dice sapphire, GaN and micro LED devices. Machining parameters were optimised so as to achieve controllable machining and high resolution. For sapphire, well-defined grooves 30 μm wide and 430 μm deep were machined. For GaN, precision features such as holes on a tens of micron length scale have been fabricated. By using this technique, compact micro LED chips with a die spacing 100 and a 430 μm thick sapphire substrate have been successfully diced. Measurements show that the performances of LED devices are not influenced by the UV laser machining. Our results demonstrate that the pulsed UV copper vapour laser is a powerful tool for micromachining and dicing of photonic materials and devices

  16. Ab initio investigations of the strontium gallium nitride ternaries Sr 3GaN3 and Sr6GaN5: Promising materials for optoelectronic

    KAUST Repository

    Goumri-Said, Souraya

    2013-05-31

    Sr3GaN3 and Sr6GaN5 could be promising potential materials for applications in the microelectronics, optoelectronics and coating materials areas of research. We studied in detail their structural, elastic, electronic, optical as well as the vibrational properties, by means of density functional theory framework. Both of these ternaries are semiconductors, where Sr3GaN3 exhibits a small indirect gap whereas Sr6GaN5 has a large direct gap. Indeed, their optical properties are reported for radiation up to 40 eV. Charge densities contours, Hirshfeld and Mulliken populations, are reported to investigate the role of each element in the bonding. From the mechanical properties calculation, it is found that Sr6GaN5 is harder than Sr3GaN3, and the latter is more anisotropic than the former. The phonon dispersion relation, density of phonon states and the vibrational stability are reported from the density functional perturbation theory calculations. © 2013 IOP Publishing Ltd.

  17. Advanced Epi Tools for Gallium Nitride Light Emitting Diode Devices

    Energy Technology Data Exchange (ETDEWEB)

    Patibandla, Nag; Agrawal, Vivek

    2012-12-01

    Over the course of this program, Applied Materials, Inc., with generous support from the United States Department of Energy, developed a world-class three chamber III-Nitride epi cluster tool for low-cost, high volume GaN growth for the solid state lighting industry. One of the major achievements of the program was to design, build, and demonstrate the world’s largest wafer capacity HVPE chamber suitable for repeatable high volume III-Nitride template and device manufacturing. Applied Materials’ experience in developing deposition chambers for the silicon chip industry over many decades resulted in many orders of magnitude reductions in the price of transistors. That experience and understanding was used in developing this GaN epi deposition tool. The multi-chamber approach, which continues to be unique in the ability of the each chamber to deposit a section of the full device structure, unlike other cluster tools, allows for extreme flexibility in the manufacturing process. This robust architecture is suitable for not just the LED industry, but GaN power devices as well, both horizontal and vertical designs. The new HVPE technology developed allows GaN to be grown at a rate unheard of with MOCVD, up to 20x the typical MOCVD rates of 3{micro}m per hour, with bulk crystal quality better than the highest-quality commercial GaN films grown by MOCVD at a much cheaper overall cost. This is a unique development as the HVPE process has been known for decades, but never successfully commercially developed for high volume manufacturing. This research shows the potential of the first commercial-grade HVPE chamber, an elusive goal for III-V researchers and those wanting to capitalize on the promise of HVPE. Additionally, in the course of this program, Applied Materials built two MOCVD chambers, in addition to the HVPE chamber, and a robot that moves wafers between them. The MOCVD chambers demonstrated industry-leading wavelength yield for GaN based LED wafers and industry

  18. Adsorption configuration of magnesium on wurtzite gallium nitride surface using first-principles calculations

    International Nuclear Information System (INIS)

    Yan Han; Gan Zhiyin; Song Xiaohui; Chen Zhaohui; Xu Jingping; Liu Sheng

    2009-01-01

    First-principles calculations of magnesium adsorption at the Ga-terminated and N-terminated {0 0 0 1} basal plane wurtzite gallium nitride surfaces have been carried out to explain the atomic-scale insight into the initial adsorption processes of magnesium doping in gallium nitride. The results reveal that magnesium adsorption on N-terminated surfaces is preferred than that on Ga-terminated surfaces. Furthermore, the surface diffusivity of magnesium atom on the N-terminated surface is much lower than that on the Ga-terminated surface, which is due to both the larger average adsorption energies and the lower adsorption distance on N-terminated surface than that on Ga-terminated surface. The results indicate that the p-type doping on the Ga-terminated surface will be better distributed than that on the N-terminated surface.

  19. Gallium Nitride Monolithic Microwave Integrated Circuit Designs Using 0.25-micro m Qorvo Process

    Science.gov (United States)

    2017-07-27

    ARL-TN-0836 ● July 2017 US Army Research Laboratory Gallium Nitride Monolithic Microwave Integrated Circuit Designs Using 0.25...findings in this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents...Citation of manufacturer’s or trade names does not constitute an official endorsement or approval of the use thereof. Destroy this report when it is no

  20. The Effects of Thermal Cycling on Gallium Nitride and Silicon Carbide Semiconductor Devices for Aerospace Use

    Science.gov (United States)

    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

  1. Gallium Nitride (GaN) High Power Electronics (FY11)

    Science.gov (United States)

    2012-01-01

    methods shown in figure 2. In the MOCVD method a source of C is the methyl groups on trimethyl gallium (TMGa). Whereas the methyls do not appear to be...RSRCH LAB ATTN IMNE ALC HRR MAIL & RECORDS MGMT ATTN RDRL CHO LL TECHL LIB ATTN RDRL CIO LT TECHL PUB ATTN RDRL SED E K A JONES (15 HCS) ADELPHI MD 20783-1197 TOTAL 19 (1 ELEC, 18 HCS)

  2. Spectral response characteristics of the transmission-mode aluminum gallium nitride photocathode with varying aluminum composition.

    Science.gov (United States)

    Hao, Guanghui; Liu, Junle; Ke, Senlin

    2017-12-10

    In order to research spectral response characteristics of transmission-mode nanostructure aluminum gallium nitride (AlGaN) photocathodes, the AlGaN photocathodes materials with varied aluminum (Al) composition were grown by metalorganic chemical vapor deposition (MOCVD) and its optical properties were measured. The Al compositions of each AlGaN film of the photocathodes were analyzed from their adsorption properties curves; their thickness was also calculated by the matrix formula of thin-film optics. The nanostructure AlGaN photocathodes were activated with the Caesium-Oxygen (Cs-O) alternation, and after the photocathode was packaged in vacuum, their spectrum responses were measured. The experimental results showed that the trend of spectrum response curves first increased and then decreased along with the increasing of the incident light wavelength. The peak spectrum response value was 17.5 mA/W at 255 nm, and its quantum efficiency was 8.5%. The lattice defects near the interface of the AlGaN heterostructure could impede the electron motion crossing this region and moving toward the photocathode surface; this was a factor that reduces the electron emission performance of the photocathodes. Also, the experimental result showed that the thickness of each AlGaN layer affected the electron diffusion characteristics; this was a key factor that influenced the spectrum response performance.

  3. Electronic properties of blue phosphorene/graphene and blue phosphorene/graphene-like gallium nitride heterostructures.

    Science.gov (United States)

    Sun, Minglei; Chou, Jyh-Pin; Yu, Jin; Tang, Wencheng

    2017-07-05

    Blue phosphorene (BlueP) is a graphene-like phosphorus nanosheet which was synthesized very recently for the first time [Nano Lett., 2016, 16, 4903-4908]. The combination of electronic properties of two different two-dimensional materials in an ultrathin van der Waals (vdW) vertical heterostructure has been proved to be an effective approach to the design of novel electronic and optoelectronic devices. Therefore, we used density functional theory to investigate the structural and electronic properties of two BlueP-based heterostructures - BlueP/graphene (BlueP/G) and BlueP/graphene-like gallium nitride (BlueP/g-GaN). Our results showed that the semiconducting nature of BlueP and the Dirac cone of G are well preserved in the BlueP/G vdW heterostructure. Moreover, by applying a perpendicular electric field, it is possible to tune the position of the Dirac cone of G with respect to the band edge of BlueP, resulting in the ability to control the Schottky barrier height. For the BlueP/g-GaN vdW heterostructure, BlueP forms an interface with g-GaN with a type-II band alignment, which is a promising feature for unipolar electronic device applications. Furthermore, we discovered that both G and g-GaN can be used as an active layer for BlueP to facilitate charge injection and enhance the device performance.

  4. Structure and Properties of Epitaxial Dielectrics on gallium nitride

    Science.gov (United States)

    Wheeler, Virginia Danielle

    GaN is recognized as a possible material for metal oxide semiconductor field effect transistors (MOSFETs) used in high temperature, high power and high speed electronic applications. However, high gate leakage and low device breakdown voltages limit their use in these applications. The use of high-kappa dielectrics, which have both a high permittivity (ε) and high band gap energy (Eg), can reduce the leakage current density that adversely affects MOS devices. La2O3 and Sc2O 3 are rare earth oxides with a large Eg (6.18 eV and 6.3 eV respectively) and a relatively high ε (27 and 14.1 respectively), which make them good candidates for enhancing MOSFET performance. Epitaxial growth of oxides is a possible approach to reducing leakage current and Fermi level pinning related to a high density of interface states for dielectrics on compound semiconductors. In this work, La2O3 and Sc2O 3 were characterized structurally and electronically as potential epitaxial gate dielectrics for use in GaN based MOSFETs. GaN surface treatments were examined as a means for additional interface passivation and influencing subsequent oxide formation. Potassium persulfate (K2(SO4)2) and potassium hydroxide (KOH) were explored as a way to achieve improved passivation and desired surface termination for GaN films deposited on sapphire substrates by metal organic chemical vapor deposition (MOCVD). X-ray photoelectron spectroscopy (XPS) showed that KOH left a nitrogen-rich interface, while K2(SO 4)2 left a gallium-rich interface, which provides a way to control surface oxide formation. K2(SO4)2 exhibited a shift in the O1s peak indicating the formation of a gallium-rich GaOx at the surface with decreased carbon contaminants. GaO x acts as a passivating layer prior to dielectric deposition, which resulted in an order of magnitude reduction in leakage current, a reduced hysteresis window, and an overall improvement in device performance. Furthermore, K2(SO4)2 resulted in an additional 0.4 eV of

  5. Properties of Erbium and Ytterbium Doped Gallium Nitride Layers Fabricated by Magnetron Sputtering

    Directory of Open Access Journals (Sweden)

    V. Prajzler

    2006-01-01

    Full Text Available We report about some properties of erbium and erbium/ytterbium doped gallium nitride (GaN layers fabricated by magnetron sputtering onsilicon, quartz and Corning glass substrates. For fabricating GaN layers two types of targets were used - gallium in a stainless steel cup anda Ga2O3 target. Deposition was carried out in the Ar+N2 gas mixture. For erbium and ytterbium doping into GaN layers, erbium metallicpowder and ytterbium powder or Er2O3 and Yb2O3 pellets were laid on the top of the target. The samples were characterized by X-raydiffraction (XRD, photoluminescence spectra and nuclear analytical methods. While the use of a metallic gallium target ensured thedeposition of well-developed polycrystalline layers, the use of gallium oxide target provided GaN films with poorly developed crystals. Bothapproaches enabled doping with erbium and ytterbium ions during deposition, and typical emission at 1 530 nm due to the Er3+ intra-4f 4I13/2 → 4I15/2 transition was observed.

  6. Large scale 2D/3D hybrids based on gallium nitride and transition metal dichalcogenides.

    Science.gov (United States)

    Zhang, Kehao; Jariwala, Bhakti; Li, Jun; Briggs, Natalie C; Wang, Baoming; Ruzmetov, Dmitry; Burke, Robert A; Lerach, Jordan O; Ivanov, Tony G; Haque, Md; Feenstra, Randall M; Robinson, Joshua A

    2017-12-21

    Two and three-dimensional (2D/3D) hybrid materials have the potential to advance communication and sensing technologies by enabling new or improved device functionality. To date, most 2D/3D hybrid devices utilize mechanical exfoliation or post-synthesis transfer, which can be fundamentally different from directly synthesized layers that are compatible with large scale industrial needs. Therefore, understanding the process/property relationship of synthetic heterostructures is priority for industrially relevant material architectures. Here we demonstrate the scalable synthesis of molybdenum disulfide (MoS 2 ) and tungsten diselenide (WSe 2 ) via metal organic chemical vapor deposition (MOCVD) on gallium nitride (GaN), and elucidate the structure, chemistry, and vertical transport properties of the 2D/3D hybrid. We find that the 2D layer thickness and transition metal dichalcogenide (TMD) choice plays an important role in the transport properties of the hybrid structure, where monolayer TMDs exhibit direct tunneling through the layer, while transport in few layer TMDs on GaN is dominated by p-n diode behavior and varies with the 2D/3D hybrid structure. Kelvin probe force microscopy (KPFM), low energy electron microscopy (LEEM) and X-ray photoelectron spectroscopy (XPS) reveal a strong intrinsic dipole and charge transfer between n-MoS 2 and p-GaN, leading to a degraded interface and high p-type leakage current. Finally, we demonstrate integration of heterogeneous 2D layer stacks of MoS 2 /WSe 2 on GaN with atomically sharp interface. Monolayer MoS 2 /WSe 2 /n-GaN stacks lead to near Ohmic transport due to the tunneling and non-degenerated doping, while few layer stacking is Schottky barrier dominated.

  7. Effects of Radiation and Long-Term Thermal Cycling on EPC 1001 Gallium Nitride Transistors

    Science.gov (United States)

    Patterson, Richard L.; Scheick, Leif; Lauenstein, Jean-Marie; Casey, Megan; 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, and thermal cycling, to name a few. Data obtained on long-term thermal cycling of new un-irradiated and irradiated samples of EPC1001 gallium nitride enhancement-mode transistors are presented. This work was done by a collaborative effort including GRC, GSFC, and support the NASA www.nasa.gov 1 JPL in of Electronic Parts and Packaging (NEPP) Program

  8. Investigating Enhancement Mode Gallium Nitride Power FETs in High Voltage, High Frequency Soft Switching Converters

    DEFF Research Database (Denmark)

    Nour, Yasser; Knott, Arnold; Jørgensen, Ivan Harald Holger

    2016-01-01

    An increased attention has been detected to develop smaller and lighter high voltage power converters in the range of 50V to 400V domain. The main applications for these converters are mainly focused for Power over Ethernet (PoE), LED lighting and AC adapters. This work will discuss a study...... of using enhancement mode gallium nitride switches to form a 50V quasi-square-wave zero-voltage-switching buck converter running at 2-6 MHz under full load. The designed converter achieved 83% efficiency converting 50V input voltage to 12.2V at 9W load....

  9. Broadband 1.2- and 2.4-mm Gallium Nitride (GaN) Power Amplifier Designs

    Science.gov (United States)

    2017-10-01

    ARL-TR-8180 ● OCT 2017 US Army Research Laboratory Broadband 1.2- and 2.4-mm Gallium Nitride (GaN) Power Amplifier Designs by...Nitride (GaN) Power Amplifier Designs by John E Penn Sensors and Electron Devices Directorate, ARL Approved for...should be aware that notwithstanding any other provision of law , no person shall be subject to any penalty for failing to comply with a collection of

  10. A Photonic 1 × 4 Power Splitter Based on Multimode Interference in Silicon–Gallium-Nitride Slot Waveguide Structures

    Directory of Open Access Journals (Sweden)

    Dror Malka

    2016-06-01

    Full Text Available In this paper, a design for a 1 × 4 optical power splitter based on the multimode interference (MMI coupler in a silicon (Si–gallium nitride (GaN slot waveguide structure is presented—to our knowledge, for the first time. Si and GaN were found as suitable materials for the slot waveguide structure. Numerical optimizations were carried out on the device parameters using the full vectorial-beam propagation method (FV-BPM. Simulation results show that the proposed device can be useful to divide optical signal energy uniformly in the C-band range (1530–1565 nm into four output ports with low insertion losses (0.07 dB.

  11. Development of III-nitride semiconductors by molecular beam epitaxy and cluster beam epitaxy and fabrication of LEDs based on indium gallium nitride MQWs

    Science.gov (United States)

    Chen, Tai-Chou Papo

    The family of III-Nitrides (the binaries InN, GaN, AIN, and their alloys) is one of the most important classes of semiconductor materials. Of the three, Indium Nitride (InN) and Aluminum Nitride (AIN) have been investigated much less than Gallium Nitride (GaN). However, both of these materials are important for optoelectronic infrared and ultraviolet devices. In particular, since InN was found recently to be a narrow gap semiconductor (Eg=0.7eV), its development should extend the applications of nitride semiconductors to the spectral region appropriate to fiber optics communication and photovoltaic applications. Similarly, the development of AIN should lead to deep UV light emitting diodes (LEDs). The first part of this work addresses the evaluation of structural, optical and transport properties of InN films grown by two different deposition methods. In one method, active nitrogen was produced in the form of nitrogen radicals by a radio frequency (RF) plasma-assisted source. In an alternative method, active nitrogen was produced in the form of clusters containing approximately 2000 nitrogen molecules. These clusters were produced by adiabatic expansion from high stagnation pressure through a narrow nozzle into vacuum. The clusters were singly or doubly ionized with positive charge by electron impact and accelerated up to approximately 20 to 25 KV prior to their disintegration on the substrate. Due to the high local temperature produced during the impact of clusters with the substrate, this method is suitable for the deposition of InN at very low temperatures. The films are auto-doped n-type with carrier concentrations varying from 3 x 1018 to 1020 cm-3 and the electron effective mass of these films was determined to be 0.09m0. The majority of the AIN films was grown by the cluster beam epitaxy method and was doped n- and p- type by incorporating silicon (Si) and magnesium (Mg) during the film deposition. All films were grown under Al-rich conditions at relatively

  12. Direct growth of graphene on gallium nitride by using chemical vapor deposition without extra catalyst

    International Nuclear Information System (INIS)

    Zhao Yun; An Tie-Lei; Yang Jian-Kun; Wei Tong-Bo; Duan Rui-Fei; Wang Gang; Yang Huai-Chao; Chen Min-Jiang; Yu Fang; Tao Li; Sun Lian-Feng

    2014-01-01

    Graphene on gallium nitride (GaN) will be quite useful when the graphene is used as transparent electrodes to improve the performance of gallium nitride devices. In this work, we report the direct synthesis of graphene on GaN without an extra catalyst by chemical vapor deposition. Raman spectra indicate that the graphene films are uniform and about 5–6 layers in thickness. Meanwhile, the effects of growth temperatures on the growth of graphene films are systematically studied, of which 950 °C is found to be the optimum growth temperature. The sheet resistance of the grown graphene is 41.1 Ω/square, which is close to the lowest sheet resistance of transferred graphene reported. The mechanism of graphene growth on GaN is proposed and discussed in detail. XRD spectra and photoluminescence spectra indicate that the quality of GaN epi-layers will not be affected after the growth of graphene. (condensed matter: structural, mechanical, and thermal properties)

  13. Microstructure and micro-Raman studies of nitridation and structure transition of gallium oxide nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Ning, J.Q. [Department of Physics and HKU-CAS Joint Laboratory on New Materials, The University of Hong Kong, Pokfulam Road, Hong Kong (China); Xu, S.J., E-mail: sjxu@hku.hk [Department of Physics and HKU-CAS Joint Laboratory on New Materials, The University of Hong Kong, Pokfulam Road, Hong Kong (China); Wang, P.W.; Song, Y.P.; Yu, D.P. [Electronic Microscopy Laboratory and State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, Hong Kong (China); Shan, Y.Y.; Lee, S.T. [Department of Physics and Materials Science, City University of Hong Kong, Kowloon, Hong Kong (China); Yang, H. [Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215123, Hong Kong (China)

    2012-11-15

    Here we present a detailed study on nitridation and structure transition in monoclinic gallium oxide ({beta}-Ga{sub 2}O{sub 3}) nanowires grown on Si substrates with chemical vapor phase epitaxy. The nanowires were systematically nitridated at different temperatures. Their morphologies and microstructures were precisely characterized using field-emission scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and confocal micro-Raman spectroscopy. It is found that heat treatment of Ga{sub 2}O{sub 3} nanowires in the gas of ammonia results in rich substructures including the Ga{sub 2}O{sub 3} phase, the crystalline GaN phase, and other meta structures. The identification of these structures helps to understand some interesting phenomena observed in nanostructures, such as the microstructural origin of the unknown Raman lines in GaN nanowires. - Highlights: Black-Right-Pointing-Pointer Nitridation and structure transition of Ga{sub 2}O{sub 3} significantly depend on temperature. Black-Right-Pointing-Pointer G-N bonds form at lower temperatures but the Ga{sub 2}O{sub 3} lattice is still dominant. Black-Right-Pointing-Pointer Amorphous GaN coexists with crystalline Ga{sub 2}O{sub 3} at higher temperatures. Black-Right-Pointing-Pointer Crystalline GaN with distinct morphology is obtained at much higher temperatures.

  14. Gallium Nitride Based Semiconductors for Short Wavelength Optoelectronics

    Science.gov (United States)

    Denbaars, S. P.

    In this article we review the key technologies for GaN based materials and devices. Developments in the methods for thin film deposition by metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) and resulting film properties are highlighted. Breakthroughs in materials growth has enabled extremely high efficiency blue and green GaN LEDs to be achieved for the first time. GaN LEDs complete the primary color spectrum and have enabled bright and reliable full-color solid state displays to be realized. Recently, room temperature operation of pulsed current injection blue-violet lasers emitting at 417 nm has further increased possible applications for GaN based optoelectronic devices.

  15. Modeling and Simulation of a Gallium Nitride (GaN) Betavoltaic Energy Converter

    Science.gov (United States)

    2016-06-01

    are from reference [23]. The remaining values are from reference [24]. Parameters Silicon (Si) Gallium Arsenide (GaAs) Silicon Carbide (4H-SiC... Aluminum x.min=102 x.max=104 conductor #Electrodes – The connection to the device. The widths are set to match the active area of the device...resistive, to simulate a equivalent shunt resistance material material= Aluminum resistivity=1.763e13 #GaN material deep level traps trap mat

  16. Review of using gallium nitride for ionizing radiation detection

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jinghui [Nuclear Engineering Program, Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Department of Radiology, Stanford University, Stanford, California 94305 (United States); Mulligan, Padhraic; Cao, Lei R., E-mail: cao.152@osu.edu [Nuclear Engineering Program, Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Brillson, Leonard [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States)

    2015-09-15

    With the largest band gap energy of all commercial semiconductors, GaN has found wide application in the making of optoelectronic devices. It has also been used for photodetection such as solar blind imaging as well as ultraviolet and even X-ray detection. Unsurprisingly, the appreciable advantages of GaN over Si, amorphous silicon (a-Si:H), SiC, amorphous SiC (a-SiC), and GaAs, particularly for its radiation hardness, have drawn prompt attention from the physics, astronomy, and nuclear science and engineering communities alike, where semiconductors have traditionally been used for nuclear particle detection. Several investigations have established the usefulness of GaN for alpha detection, suggesting that when properly doped or coated with neutron sensitive materials, GaN could be turned into a neutron detection device. Work in this area is still early in its development, but GaN-based devices have already been shown to detect alpha particles, ultraviolet light, X-rays, electrons, and neutrons. Furthermore, the nuclear reaction presented by {sup 14}N(n,p){sup 14}C and various other threshold reactions indicates that GaN is intrinsically sensitive to neutrons. This review summarizes the state-of-the-art development of GaN detectors for detecting directly and indirectly ionizing radiation. Particular emphasis is given to GaN's radiation hardness under high-radiation fields.

  17. Two-dimensional dopant profiling of gallium nitride p–n junctions by scanning capacitance microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lamhamdi, M. [GREMAN UMR 7347-Université de Tours, 10 Rue Thales de Milet, BP 7155, 37071 Tours (France); Ecole national des sciences appliquées khouribga, Université Hassan 1er, 26000 Settat (Morocco); Cayrel, F. [GREMAN UMR 7347-Université de Tours, 10 Rue Thales de Milet, BP 7155, 37071 Tours (France); Frayssinet, E. [CRHEA-CNRS, Rue Bernard Grégory, Sophia Antipolis, 06560 Valbonne (France); Bazin, A.E.; Yvon, A.; Collard, E. [STMicroelectronics, 16 Rue Pierre et Marie Curie, BP 7155, 37071 Tours (France); Cordier, Y. [CRHEA-CNRS, Rue Bernard Grégory, Sophia Antipolis, 06560 Valbonne (France); Alquier, D. [GREMAN UMR 7347-Université de Tours, 10 Rue Thales de Milet, BP 7155, 37071 Tours (France)

    2016-04-01

    Two-dimensional imaging of dopant profiles for n and p-type regions are relevant for the development of new power semiconductors, especially for gallium nitride (GaN) for which classical profiling techniques are not adapted. This is a challenging task since it needs a technique with simultaneously good sensitivity, high spatial resolution and high dopant gradient resolution. To face these challenges, scanning capacitance microscopy combined with Atomic Force Microscopy is a good candidate, presenting reproducible results, as demonstrated in literature. In this work, we attempt to distinguish reliably and qualitatively the various doping concentrations and type at p–n and unipolar junctions. For both p–n and unipolar junctions three kinds of samples were prepared and measured separately. The space-charge region of the p–n metallurgical junction, giving rise to different contrasts under SCM imaging, is clearly observed, enlightening the interest of the SCM technique.

  18. Fabrication of gallium nitride nanowires by metal-assisted photochemical etching

    Science.gov (United States)

    Zhang, Miao-Rong; Jiang, Qing-Mei; Zhang, Shao-Hui; Wang, Zu-Gang; Hou, Fei; Pan, Ge-Bo

    2017-11-01

    Gallium nitride (GaN) nanowires (NWs) were fabricated by metal-assisted photochemical etching (MaPEtch). Gold nanoparticles (AuNPs) as metal catalyst were electrodeposited on the GaN substrate. SEM and HRTEM images show the surface of GaN NWs is smooth and clean without any impurity. SAED and FFT patterns demonstrate GaN NWs have single crystal structure, and the crystallographic orientation of GaN NWs is (0002) face. On the basis of the assumption of localized galvanic cells, combined with the energy levels and electrochemical potentials of reactants in this etching system, the generation, transfer and consumption of electron-hole pairs reveal the whole MaPEtch reaction process. Such easily fabricated GaN NWs have great potential for the assembly of GaN-based single-nanowire nanodevices.

  19. Radiation and Thermal Cycling Effects on EPC1001 Gallium Nitride Power Transistors

    Science.gov (United States)

    Patterson, Richard L.; Scheick, Leif Z.; Lauenstein, Jean M.; Casey, Megan C.; 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, and thermal cycling, to name a few. Information pertaining to performance of electronic parts and systems under hostile environments is very scarce, especially for new devices. Such data is very critical so that proper design is implemented in order to ensure mission success and to mitigate risks associated with exposure of on-board systems to the operational environment. In this work, newly-developed enhancement-mode field effect transistors (FET) based on gallium nitride (GaN) technology were exposed to various particles of ionizing radiation and to long-term thermal cycling over a wide temperature range. Data obtained on control (un-irradiated) and irradiated samples of these power transistors are presented and the results are discussed.

  20. Free-Standing Self-Assemblies of Gallium Nitride Nanoparticles: A Review

    Directory of Open Access Journals (Sweden)

    Yucheng Lan

    2016-08-01

    Full Text Available Gallium nitride (GaN is an III-V semiconductor with a direct band-gap of 3 . 4 e V . GaN has important potentials in white light-emitting diodes, blue lasers, and field effect transistors because of its super thermal stability and excellent optical properties, playing main roles in future lighting to reduce energy cost and sensors to resist radiations. GaN nanomaterials inherit bulk properties of the compound while possess novel photoelectric properties of nanomaterials. The review focuses on self-assemblies of GaN nanoparticles without templates, growth mechanisms of self-assemblies, and potential applications of the assembled nanostructures on renewable energy.

  1. Aluminum Gallium Nitride Alloys Grown via Metalorganic Vapor-Phase Epitaxy Using a Digital Growth Technique

    Science.gov (United States)

    Rodak, L. E.; Korakakis, D.

    2011-04-01

    This work investigates the use of a digital growth technique as a viable method for achieving high-quality aluminum gallium nitride (Al x Ga1- x N) films via metalorganic vapor-phase epitaxy. Digital alloys are superlattice structures with period thicknesses of a few monolayers. Alloys with an AlN mole fraction ranging from 0.1 to 0.9 were grown by adjusting the thickness of the AlN layer in the superlattice. High-resolution x-ray diffraction was used to determine the superlattice period and c-lattice parameter of the structure, while reciprocal-space mapping was used to determine the a-lattice parameter and evaluate growth coherency. A comparison of the measured lattice parameter with both the nominal value and also the underlying buffer layer is discussed.

  2. Imaging the p-n junction in a gallium nitride nanowire with a scanning microwave microscope

    Energy Technology Data Exchange (ETDEWEB)

    Imtiaz, Atif [Physical Measurement Laboratory, National Institute of Standards and Technology, Boulder, Colorado 80305 (United States); Department of Electrical, Computer, and Energy Engineering, University of Colorado, Boulder, Colorado 80309 (United States); Wallis, Thomas M.; Brubaker, Matt D.; Blanchard, Paul T.; Bertness, Kris A.; Sanford, Norman A.; Kabos, Pavel, E-mail: kabos@boulder.nist.gov [Physical Measurement Laboratory, National Institute of Standards and Technology, Boulder, Colorado 80305 (United States); Weber, Joel C. [Physical Measurement Laboratory, National Institute of Standards and Technology, Boulder, Colorado 80305 (United States); Department of Mechanical Engineering, University of Colorado, Boulder, Colorado 80309 (United States); Coakley, Kevin J. [Information Technology Laboratory, National Institute of Standards and Technology, Boulder, Colorado 80305 (United States)

    2014-06-30

    We used a broadband, atomic-force-microscope-based, scanning microwave microscope (SMM) to probe the axial dependence of the charge depletion in a p-n junction within a gallium nitride nanowire (NW). SMM enables the visualization of the p-n junction location without the need to make patterned electrical contacts to the NW. Spatially resolved measurements of S{sub 11}{sup ′}, which is the derivative of the RF reflection coefficient S{sub 11} with respect to voltage, varied strongly when probing axially along the NW and across the p-n junction. The axial variation in S{sub 11}{sup ′}  effectively mapped the asymmetric depletion arising from the doping concentrations on either side of the junction. Furthermore, variation of the probe tip voltage altered the apparent extent of features associated with the p-n junction in S{sub 11}{sup ′} images.

  3. Imaging the p-n junction in a gallium nitride nanowire with a scanning microwave microscope

    Science.gov (United States)

    Imtiaz, Atif; Wallis, Thomas M.; Weber, Joel C.; Coakley, Kevin J.; Brubaker, Matt D.; Blanchard, Paul T.; Bertness, Kris A.; Sanford, Norman A.; Kabos, Pavel

    2014-06-01

    We used a broadband, atomic-force-microscope-based, scanning microwave microscope (SMM) to probe the axial dependence of the charge depletion in a p-n junction within a gallium nitride nanowire (NW). SMM enables the visualization of the p-n junction location without the need to make patterned electrical contacts to the NW. Spatially resolved measurements of S11', which is the derivative of the RF reflection coefficient S11 with respect to voltage, varied strongly when probing axially along the NW and across the p-n junction. The axial variation in S11' effectively mapped the asymmetric depletion arising from the doping concentrations on either side of the junction. Furthermore, variation of the probe tip voltage altered the apparent extent of features associated with the p-n junction in S11' images.

  4. Gallium nitride nanoneedles grown in extremely non-equilibrium nitrogen plasma

    Energy Technology Data Exchange (ETDEWEB)

    Mangla, O., E-mail: onkarmangla@gmail.com [Department of Physics and Astrophysics, University of Delhi, Delhi, 110007 (India); Physics Department, Hindu College, University of Delhi, Delhi, 110007 (India); Roy, S. [Physics Department, Daulat Ram College, University of Delhi, Delhi, 110007 (India)

    2016-05-23

    In the present work, gallium nitride (GaN) nanoneedles are grown on quartz substrates using the high fluence ions of GaN produced by hot, dense and extremely non-equlibrium nitrogen plasma in a modified dense plasma focus device. The formation of nanoneedles is obtained from the scanning electron microscopy with mean size of the head of nanoneedles ~ 70 nm. The nanoneedles are found to be poly-crystalline when studied structurally through the X-ray diffraction. The optical properties of nanoneedles studied using absorption spectra which show more absorption for nanoneedles depsoited one shot of ions irradiation. In addition, the band gap of nanoneedles is found to be increased as compared to bulk GaN. The obtained nanoneedles with increased band gap have potential applications in detector systems.

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

    Science.gov (United States)

    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.

  6. Compatibility of ITER candidate structural materials with static gallium

    International Nuclear Information System (INIS)

    Luebbers, P.R.; Michaud, W.F.; Chopra, O.K.

    1993-12-01

    Tests were conducted on the compatibility of gallium with candidate structural materials for the International Thermonuclear Experimental Reactor, e.g., Type 316 SS, Inconel 625, and Nb-5 Mo-1 Zr alloy, as well as Armco iron, Nickel 270, and pure chromium. Type 316 stainless steel is least resistant to corrosion in static gallium and Nb-5 Mo-1 Zr alloy is most resistant. At 400 degrees C, corrosion rates are ∼4.0, 0.5, and 0.03 mm/yr for type 316 SS, Inconel 625, and Nb-5 Mo- 1 Zr alloy, respectively. The pure metals react rapidly with gallium. In contrast to findings in earlier studies, pure iron shows greater corrosion than nickel. The corrosion rates at 400 degrees C are ≥88 and 18 mm/yr, respectively, for Armco iron and Nickel 270. The results indicate that at temperatures up to 400 degrees C, corrosion occurs primarily by dissolution and is accompanied by formation of metal/gallium intermetallic compounds. The solubility data for pure metals and oxygen in gallium are reviewed. The physical, chemical, and radioactive properties of gallium are also presented. The supply and availability of gallium, as well as price predictions through the year 2020, are summarized

  7. Compatibility of ITER candidate structural materials with static gallium

    Energy Technology Data Exchange (ETDEWEB)

    Luebbers, P.R.; Michaud, W.F.; Chopra, O.K.

    1993-12-01

    Tests were conducted on the compatibility of gallium with candidate structural materials for the International Thermonuclear Experimental Reactor, e.g., Type 316 SS, Inconel 625, and Nb-5 Mo-1 Zr alloy, as well as Armco iron, Nickel 270, and pure chromium. Type 316 stainless steel is least resistant to corrosion in static gallium and Nb-5 Mo-1 Zr alloy is most resistant. At 400{degrees}C, corrosion rates are {approx}4.0, 0.5, and 0.03 mm/yr for type 316 SS, Inconel 625, and Nb-5 Mo- 1 Zr alloy, respectively. The pure metals react rapidly with gallium. In contrast to findings in earlier studies, pure iron shows greater corrosion than nickel. The corrosion rates at 400{degrees}C are {ge}88 and 18 mm/yr, respectively, for Armco iron and Nickel 270. The results indicate that at temperatures up to 400{degrees}C, corrosion occurs primarily by dissolution and is accompanied by formation of metal/gallium intermetallic compounds. The solubility data for pure metals and oxygen in gallium are reviewed. The physical, chemical, and radioactive properties of gallium are also presented. The supply and availability of gallium, as well as price predictions through the year 2020, are summarized.

  8. A thin film P-type gallium nitride photocathode: Prospect for a high performance electron emitter

    Science.gov (United States)

    Machuca, Francisco Javier, Jr.

    The study of the electronic structure of gallium nitride (GaN) surfaces is undertaken in order to evaluate a wide band gap photocathode as a high performance electron source. In considering detailed studies targeting the starting surface of GaN (0001) and the nature of the activation layers using Cs only and Cs/O, an efficient and robust emitter is proposed. Achieving clean surfaces is a major and challenging requirement for the study of any semiconductor surface. The use of synchrotron radiation (SR) to probe the electronic structure of the GaN (0001) surface that has undergone wet chemical cleaning sequences followed by heating is described. The refractive properties of GaN allow a simple and non-destructive surface preparation to be successful in removing C and O contaminants, involving chemical cleaning followed by thermal desorption. The electron affinity for the clean surface measured is 3.3 +/- 0.2 eV using SRPES. The maximum reduction achieved in the electron affinity is approximately 3.0 +/- 0.2 eV by depositing ¾ ML of cesium at room temperature. In addition, the threshold for photoemission emission in spectral yield curves is at the band gap energy of GaN (3.4eV), demonstrating the NEA activation of GaN with Cs alone. The chemistry of the traditional co-deposited cesium and oxygen (Cs/0) adlayer commonly used with small band gap III-V's is also investigated. These are the first studies reporting a molecular form of oxygen incorporated in the thin NEA activation layers and the charge state is found to determine the net dipole strength leading to the maximum yield obtainable with the Cs/O activation. Last, a comparative study is performed between Cs/0 activated GaN (0001) and GaAs (100) investigating the decay in the quantum yield using low photon density. The quantum efficiency (QE) from the GaN (0001) photocathode remains constant within a few percent over a 10 hour period at ≥20% QE and decays by less than a factor of 2 over the subsequent 7 hours

  9. Structure and luminescence of nanocrystalline gallium nitride synthesized by a novel polymer pyrolysis route

    Science.gov (United States)

    Garcia, Rafael; Hirata, Gustavo A.; Thomas, Alan C.; Ponce, Fernando A.

    2006-10-01

    Thermal decomposition in a horizontal quartz tube reactor of a polymer [-(CH 6N 4O) 3Ga(NO 3) 3-] in a nitrogen atmosphere, yield directly nano-structured gallium nitride (GaN) powder. The polymer was obtained by the reaction between high purity gallium nitrate (Ga(NO 3) 3) dissolved in toluene and carbohydrazide as an azotic ligand. The powder synthesized by this method showed a yellow color and elemental analysis suggested that the color is due to some carbon and oxygen impurities in the as-synthesized powder. Electron microscopy showed that the as-synthesized powders consist of a mixture of various porous particles containing nanowires and nano-sized platelets. The size of the crystallites can be controlled by annealing processes under ammonia. Photoluminescence analysis at 10 K on as-synthesized powders showed a broad red luminescence around 668 nm under UV laser excitation (He-Cd laser, 325 nm). However after annealing process the red luminescence disappears and the typical band edge emission of GaN around 357 nm (3.47 eV) and the UV band were the dominant emissions in the PL spectra.

  10. Chemical exfoliation and optical characterization of threading-dislocation-free gallium-nitride ultrathin nanomembranes

    KAUST Repository

    Elafandy, Rami T.

    2014-11-13

    Semiconductor nanostructures have generated tremendous scientific interests as well as practical applications stemming from the engineering of low dimensional physics phenomena. Unlike 0D and 1D nanostructures, such as quantum dots and nanowires, respectively, 2D structures, such as nanomembranes, are unrivalled in their scalability for high yield manufacture and are less challenging in handling with the current transfer techniques. Furthermore, due to their planar geometry, nanomembranes are compatible with the current complementary metal oxide semiconductor (CMOS) technology. Due to these superior characteristics, there are currently different techniques in exfoliating nanomembranes with different crystallinities, thicknesses and compositions. In this work we demonstrate a new facile technique of exfoliating gallium nitride (GaN) nanomembranes with novel features, namely with the non-radiative cores of their threading-dislocations (TDs) being etched away. The exfoliation process is based on engineering the gallium vacancy (VGa) density during the GaN epitaxial growth with subsequent preferential etching. Based on scanning and transmission electron microscopies, as well as micro-photoluminescence measurements, a model is proposed to uncover the physical processes underlying the formation of the nanomembranes. Raman measurements are also performed to reveal the internal strain within the nanomembranes. After transferring these freely suspended 25 nm thin GaN nanomembranes to other substrates, we demonstrate the temperature dependence of their bandgap by photoluminescence technique, in order to shed light on the internal carrier dynamics. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

  11. Compatibility of candidate structural materials with static gallium

    International Nuclear Information System (INIS)

    Luebbers, P.R.; Michaud, W.F.; Chopra, O.K.

    1993-01-01

    Scoping tests were conducted on compatibility of gallium with candidate structural materials, e.g., Type 316 SS, Inconel 625, and Nb-5 Mo-1 Zr alloy, as well as Armco iron, Nickel 270, and pure chronimum. Type 316 stainless steel is least resistant and Nb-5 Mo-1 Zr alloy is most resistant to corrosion in static gallium. At 400 degrees C, corrosion rates are ∼4.0, 0.5, and 0.03 mm/y for Type 316 SS, Inconel 625, and Nb-5 Mo-1 Zr alloy, respectively. The pure metals react rapidly with gallium. In contrast to findings in earlier studies, pure iron shows greater corrosion than does nickel. The corrosion rates at 400 degrees C are ≥90 and 17 mm/y, respectively, for Armco iron and Nickel 270. The results indicate that at temperatures up to 400 degrees C, corrosion occurs primarily by dissolution accompanied by formation of metal/gallium intermetallic compounds

  12. Current status and scope of gallium nitride-based vertical transistors for high-power electronics application

    International Nuclear Information System (INIS)

    Chowdhury, Srabanti; Swenson, Brian L; Wong, Man Hoi; Mishra, Umesh K

    2013-01-01

    Gallium nitride (GaN) is becoming the material of choice for power electronics to enable the roadmap of increasing power density by simultaneously enabling high-power conversion efficiency and reduced form factor. This is because the low switching losses of GaN enable high-frequency operation which reduces bulky passive components with negligible change in efficiency. Commercialization of GaN-on-Si materials for power electronics has led to the entry of GaN devices into the medium-power market since the performance-over-cost of even first-generation products looks very attractive compared to today's mature Si-based solutions. On the other hand, the high-power market still remains unaddressed by lateral GaN devices. The current and voltage demand for high-power conversion application makes the chip area in a lateral topology so large that it becomes difficult to manufacture. Vertical GaN devices would play a big role alongside silicon carbide (SiC) to address the high-power conversion needs. In this paper vertical GaN devices are discussed with emphasis on current aperture vertical electron transistors (CAVETs) which have shown promising performance. The fabrication-related challenges and the future possibilities enabled by the availability of good-quality, cost-competitive bulk GaN material are also evaluated for CAVETs. (invited review)

  13. Variation of crystallinity and stoichiometry in films of gallium oxide, gallium nitride and barium zirconate prepared by means of PLD; Variation von Kristallinitaet und Stoechiometrie in mittels PLD hergestellten Schichten aus Galliumoxid, Galliumnitrid und Bariumzirkonat

    Energy Technology Data Exchange (ETDEWEB)

    Brendt, Jochen

    2011-08-05

    Pulsed Laser Deposition (PLD) is an ablation technique for thin film preparation of many materials. The film properties can be well controlled by the process parameters. Therefore, in many cases a given material can be deposited with different properties by changing one or more process parameters. In this thesis thin films of gallium oxide, gallium nitride and barium zirconate were deposited with a large variation in structure and stoichiometry by means of Pulsed Laser Deposition. The characterization of the film crystallinity, phase purity and short range structural order was completed by means of X-ray diffraction and X-ray absorption spectroscopy. The stoichiometry was investigated using electron probe microanalysis. For analyzing the correlation between the structure and stoichiometry with the optical and electrical properties, optical absorption and electrical conductivity measurements were carried out. The investigation of all three material systems showed that very unique properties can be realized when combining an amorphous structure and a non-stoichiometric composition. For example, in amorphous and oxygen deficient gallium oxide an insulator-metal-transition can be induced by partial crystallization of the as prepared phase accomplished by annealing at about 400 C in argon atmosphere (as shown in literature). Furthermore, amorphous and highly non-stoichiometric barium zirconate has the ability to split water molecules to hydrogen and oxygen at room temperature. A detailed analysis of both phenomena has been performed by means of photoemission and transmission electron microscopy in the case of gallium oxide and via X-ray absorption spectroscopy and gas chromatography in the case of barium zirconate.

  14. Spectroscopic Ellipsometry Measurements of Wurtzite Gallium Nitride Surfaces as a Function of Buffered Oxide Etch Substrate Submersion

    Science.gov (United States)

    Szwejkowski, Chester; Constantin, Costel; Duda, John; Hopkins, Patrick; Optical Studies of GaN interfaces Collaboration

    2013-03-01

    Gallium nitride (GaN) is considered the most important semiconductor after the discovery of silicon. Understanding the optical properties of GaN surfaces is imperative in determining the utility and applicability of this class of materials to devices. In this work, we present preliminary results of spectroscopic ellipsometry measurements as a function of surface root mean square (RMS). We used commercially available 5mm x 5mm, one side polished GaN (3-7 μm)/Sapphire (430 μm) substrates that have a wurtzite crystal structure and they are slightly n-type doped. The GaN substrates were cleaned with Acetone (20 min)/Isopropanol(20 min)/DI water (20 min) before they were submerged into Buffered Oxide Etch (BOE) for 10s - 60s steps. This BOE treatment produced RMS values of 1-30 nm as measured with an atomic force microscope. Preliminary qualitative ellipsometric measurements show that the complex refractive index and the complex dielectric function decrease with an increase of RMS. More measurements need to be done in order to provide explicit quantitative results. This work was supported by the 4-VA Collaborative effort between James Madison University and University of Virginia.

  15. Significant improvement in the electrical characteristics of Schottky barrier diodes on molecularly modified Gallium Nitride surfaces

    Science.gov (United States)

    Garg, Manjari; Naik, Tejas R.; Pathak, C. S.; Nagarajan, S.; Rao, V. Ramgopal; Singh, R.

    2018-04-01

    III-Nitride semiconductors face the issue of localized surface states, which causes fermi level pinning and large leakage current at the metal semiconductor interface, thereby degrading the device performance. In this work, we have demonstrated the use of a Self-Assembled Monolayer (SAM) of organic molecules to improve the electrical characteristics of Schottky barrier diodes (SBDs) on n-type Gallium Nitride (n-GaN) epitaxial films. The electrical characteristics of diodes were improved by adsorption of SAM of hydroxyl-phenyl metallated porphyrin organic molecules (Zn-TPPOH) onto the surface of n-GaN. SAM-semiconductor bonding via native oxide on the n-GaN surface was confirmed using X-ray photoelectron spectroscopy measurements. Surface morphology and surface electronic properties were characterized using atomic force microscopy and Kelvin probe force microscopy. Current-voltage characteristics of different metal (Cu, Ni) SBDs on bare n-GaN were compared with those of Cu/Zn-TPPOH/n-GaN and Ni/Zn-TPPOH/n-GaN SBDs. It was found that due to the molecular monolayer, the surface potential of n-GaN was decreased by ˜350 mV. This caused an increase in the Schottky barrier height of Cu and Ni SBDs from 1.13 eV to 1.38 eV and 1.07 eV to 1.22 eV, respectively. In addition to this, the reverse bias leakage current was reduced by 3-4 orders of magnitude for both Cu and Ni SBDs. Such a significant improvement in the electrical performance of the diodes can be very useful for better device functioning.

  16. Modeling, Fabrication, and Analysis of Vertical Conduction Gallium Nitride Fin MOSFET

    Science.gov (United States)

    Tahhan, Maher Bishara

    Gallium Nitride has seen much interest in the field of electronics due to its large bandgap and high mobility. In the field of power electronics, this combination leads to a low on-resistance for a given breakdown voltage. To take full advantage of this, vertical conduction transistors in GaN can give high breakdown voltages independent of chip area, leading to transistors with nominally low on resistance with high breakdown at a low cost. Acknowledging this, a vertical transistor design is presented with a small footprint area. This design utilizes a fin structure as a double gated insulated MESFET with electrons flowing from the top of the fin downward. The transistor's characteristics and design is initially explored via simulation and modelling. In this modelling, it is found that the narrow dimension of the fin must be sub-micron to allow for the device to be turned off with no leakage current and have a positive threshold voltage. Several process modules are developed and integrated to fabricate the device. A smooth vertical etch leaving low damage to the surfaces is demonstrated and characterized, preventing micromasking during the GaN dry etch. Methods of removing damage from the dry etch are tested, including regrowth and wet etching. Several hard masks were developed to be used in conjunction with this GaN etch for various requirements of the process, such as material constraints and self-aligning a metal contact. Multiple techniques are tested to deposit and pattern the gate oxide and metal to ensure good contact with the channel without causing unwanted shorts. To achieve small fin dimensions, a self-aligned transistor process flow is presented allowing for smaller critical dimensions at increased fabrication tolerances by avoiding the use of lithographic steps that require alignments to very high accuracy. In the case of the device design presented, the fins are lithographically defined at the limit of i-line stepper system. From this single

  17. In-situ multi-information measurement system for preparing gallium nitride photocathode

    International Nuclear Information System (INIS)

    Fu Xiao-Qian; Chang Ben-Kang; Qian Yun-Sheng; Zhang Jun-Ju

    2012-01-01

    We introduce the first domestic in-situ multi-information measurement system for a gallium nitride (GaN) photocathode. This system can successfully fulfill heat cleaning and activation for GaN in an ultrahigh vacuum environment and produce a GaN photocathode with a negative electron affinity (NEA) status. Information including the heat cleaning temperature, vacuum degree, photocurrent, electric current of cesium source, oxygen source, and the most important information about the spectral response, or equivalently, the quantum efficiency (QE) can be obtained during preparation. The preparation of a GaN photocathode with this system indicates that the optimal heating temperature in a vacuum is about 700 °C. We also develop a method of quickly evaluating the atomically clean surface with the vacuum degree versus wavelength curve to prevent possible secondary contamination when the atomic level cleaning surface is tested with X-ray photoelectron spectroscopy. The photocurrent shows a quick enhancement when the current ratio between the cesium source and oxygen source is 1.025. The spectral response of the GaN photocathode is flat in a wavelength range from 240 nm to 365 nm, and an abrupt decline is observed at 365 nm, which demonstrates that with the in-situ multi-information measurement system the NEA GaN photocathode can be successfully prepared. (rapid communication)

  18. In-situ multi-information measurement system for preparing gallium nitride photocathode

    Science.gov (United States)

    Fu, Xiao-Qian; Chang, Ben-Kang; Qian, Yun-Sheng; Zhang, Jun-Ju

    2012-03-01

    We introduce the first domestic in-situ multi-information measurement system for a gallium nitride (GaN) photocathode. This system can successfully fulfill heat cleaning and activation for GaN in an ultrahigh vacuum environment and produce a GaN photocathode with a negative electron affinity (NEA) status. Information including the heat cleaning temperature, vacuum degree, photocurrent, electric current of cesium source, oxygen source, and the most important information about the spectral response, or equivalently, the quantum efficiency (QE) can be obtained during preparation. The preparation of a GaN photocathode with this system indicates that the optimal heating temperature in a vacuum is about 700 °C. We also develop a method of quickly evaluating the atomically clean surface with the vacuum degree versus wavelength curve to prevent possible secondary contamination when the atomic level cleaning surface is tested with X-ray photoelectron spectroscopy. The photocurrent shows a quick enhancement when the current ratio between the cesium source and oxygen source is 1.025. The spectral response of the GaN photocathode is flat in a wavelength range from 240 nm to 365 nm, and an abrupt decline is observed at 365 nm, which demonstrates that with the in-situ multi-information measurement system the NEA GaN photocathode can be successfully prepared.

  19. Exfoliation of Threading Dislocation-Free, Single-Crystalline, Ultrathin Gallium Nitride Nanomembranes

    KAUST Repository

    Elafandy, Rami T.

    2014-04-01

    Despite the recent progress in gallium nitride (GaN) growth technology, the excessively high threading dislocation (TD) density within the GaN crystal, caused by the reliance on heterogeneous substrates, impedes the development of high-efficiency, low-cost, GaN-based heterostructure devices. For the first time, the chemical exfoliation of completely TD-free, single-crystalline, ultrathin (tens of nanometers) GaN nanomembranes is demonstrated using UV-assisted electroless chemical etching. These nanomembranes can act as seeding layers for subsequent overgrowth of high-quality GaN. A model is proposed, based on scanning and transmission electron microscopy as well as optical measurements to explain the physical processes behind the formation of the GaN nanomembranes. These novel nanomembranes, once transferred to other substrates, present a unique and technologically attractive path towards integrating high-efficiency GaN optical components along with silicon electronics. Interestingly, due to their nanoscale thickness and macroscopic sizes, these nanomembranes may enable the production of flexible GaN-based optoelectronics. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Surface Preparation and Deposited Gate Oxides for Gallium Nitride Based Metal Oxide Semiconductor Devices

    Science.gov (United States)

    Long, Rathnait D.; McIntyre, Paul C.

    2012-01-01

    The literature on polar Gallium Nitride (GaN) surfaces, surface treatments and gate dielectrics relevant to metal oxide semiconductor devices is reviewed. The significance of the GaN growth technique and growth parameters on the properties of GaN epilayers, the ability to modify GaN surface properties using in situ and ex situ processes and progress on the understanding and performance of GaN metal oxide semiconductor (MOS) devices are presented and discussed. Although a reasonably consistent picture is emerging from focused studies on issues covered in each of these topics, future research can achieve a better understanding of the critical oxide-semiconductor interface by probing the connections between these topics. The challenges in analyzing defect concentrations and energies in GaN MOS gate stacks are discussed. Promising gate dielectric deposition techniques such as atomic layer deposition, which is already accepted by the semiconductor industry for silicon CMOS device fabrication, coupled with more advanced physical and electrical characterization methods will likely accelerate the pace of learning required to develop future GaN-based MOS technology.

  1. Basic Equations for the Modeling of Gallium Nitride (gan) High Electron Mobility Transistors (hemts)

    Science.gov (United States)

    Freeman, Jon C.

    2003-01-01

    Gallium nitride (GaN) is a most promising wide band-gap semiconductor for use in high-power microwave devices. It has functioned at 320 C, and higher values are well within theoretical limits. By combining four devices, 20 W has been developed at X-band. GaN High Electron Mobility Transistors (HEMTs) are unique in that the two-dimensional electron gas (2DEG) is supported not by intentional doping, but instead by polarization charge developed at the interface between the bulk GaN region and the AlGaN epitaxial layer. The polarization charge is composed of two parts: spontaneous and piezoelectric. This behavior is unlike other semiconductors, and for that reason, no commercially available modeling software exists. The theme of this document is to develop a self-consistent approach to developing the pertinent equations to be solved. A Space Act Agreement, "Effects in AlGaN/GaN HEMT Semiconductors" with Silvaco Data Systems to implement this approach into their existing software for III-V semiconductors, is in place (summer of 2002).

  2. Channeling study of lattice disorder and gold implants in gallium nitride

    International Nuclear Information System (INIS)

    Jiang, W.; Weber, W.J.; Thevuthasan, S.; Shutthanandan, V.

    2002-01-01

    Irradiation experiments have been performed 60 deg. off normal for a gallium nitride (GaN) single-crystal film at 300 K using 3 MeV Au 3+ ions over fluences ranging from 0.88 to 86.2 ions/nm 2 . The accumulation of disorder on both the Ga and N sublattices has been simultaneously investigated using 3.8 MeV He + non-Rutherford backscattering spectrometry (non-RBS) along the and axial channeling directions. The accumulated disorder at the damage peak increases with dose below 10 dpa and saturates at a relative level of ∼0.7 between 10 and 60 dpa. Complete amorphization starts at the surface and grows into the damage peak regime. A higher rate of disordering on the N sublattice is observed at low damage levels, which suggests a lower threshold displacement energy on the N sublattice in GaN. Isochronal annealing (20 min) at temperatures up to 1000 K has been used to follow the thermal response of the Ga disorder and Au implants. Some defect recovery occurs at the intermediate damage levels. A fraction of Au occupancy on the Ga lattice site is observed in the as-implanted GaN, and the substitutional fraction of the implanted Au increases with increasing temperature

  3. Hall effect and photoconductivity lifetime studies of gallium nitride, indium nitride, and mercury cadmium telluride

    Science.gov (United States)

    Swartz, Craig H.

    A deep understanding of both carrier recombination and transport is necessary for semiconductor engineering, particularly in defining the ultimate limits of performance for a given device before spending the resources to perfect its fabrication. Hall effect measurements utilizing a variable magnetic field are necessary to discriminate between conduction in epitaxial layers and conduction originating at the surface or at an interfacial layer. For thick hydride vapor phase epitaxy (HVPE) grown GaN, variable field Hall measurements revealed the presence of small but significant lower mobility surface and interface electrons which would otherwise lead to errors in interpreting the electrical properties. In addition, QMSA analysis of the measurements indicates that thick GaN samples contain a large spread in electron mobility values, most likely with depth. For molecular beam epitaxial InN, it was found that electrical measurements are affected by surface charge conduction, as well as the non-uniformity of mobility and carrier concentration with depth. Both of these effects mask the surprisingly high quality of the material close to the surface. Photoconductance lifetime and variable-magnetic-field Hall and transient measurements were performed on a series of undoped, In-doped and As-doped HgCdTe grown by MBE and MOCVD. N-type layers often significantly influence the interpretation of the electrical measurements. Even the best Low Wavelength Infrared (LWIR) n-type material still appears to be dominated by defect-related recombination, as intrinsic lifetimes calculated with full band structure can be well above those measured. Mid-Wavelength Infrared (MWIR) lifetimes increase somewhat with carrier concentration, as if the n-type doping process were passivating Schockley-Read-Hall (SRH) defects. P-type MWIR films lie mainly below the predicted values, and their relationship between concentration and lifetime is essentially unchanged by growth technique, indicating that a

  4. Development of gallium-nitride-based light-emitting diodes (LEDs) and laser diodes for energy-efficient lighting and displays

    International Nuclear Information System (INIS)

    DenBaars, Steven P.; Feezell, Daniel; Kelchner, Katheryn; Pimputkar, Siddha; Pan, Chi-Chen; Yen, Chia-Chen; Tanaka, Shinichi; Zhao, Yuji; Pfaff, Nathan; Farrell, Robert; Iza, Mike; Keller, Stacia; Mishra, Umesh; Speck, James S.; Nakamura, Shuji

    2013-01-01

    Light-emitting diodes (LEDs) fabricated from gallium nitride (GaN) have led to the realization of high-efficiency white solid-state lighting. Currently, GaN white LEDs exhibit luminous efficacy greater than 150 lm W −1 , and external quantum efficiencies higher than 60%. This has enabled LEDs to compete with traditional lighting technologies, such as incandescent and compact fluorescent (CFL) lighting. Further improvements in materials quality and cost reduction are necessary for widespread adoption of LEDs for lighting. A review of the unique polarization anisotropy in GaN is included for the different crystal orientations. The emphasis on nonpolar and semipolar LEDs highlights high-power violet and blue emitters, and we consider the effects of indium incorporation and well width. Semipolar GaN materials have enabled the development of high-efficiency LEDs in the blue region and recent achievements of green laser diodes at 520 nm

  5. Surface and interface properties of polar gallium nitride layers; Oberflaechen- und Grenzflaecheneigenschaften von polaren Galliumnitrid-Schichten

    Energy Technology Data Exchange (ETDEWEB)

    Lorenz, Pierre

    2010-07-09

    The material properties of group III-nitrides allows manifold applications. Especially for the GaN-based gas and biosensor technology, an understanding of the GaN surfaces and their interaction with molecules is crucial for the successful development of sensor systems. Especially the influence of crystal orientation, surface termination and reconstruction on the interaction was analysed. To study the interaction of the GaN surface with molecules the reproducible and controllable preparation of GaN surfaces is necessary. Polar GaN layers were grown by molecular beam epitaxy. The surface reconstruction and termination could be selectively adjusted by the growth parameters or further preparation steps. On the Ga-polar surface, gallium-induced and nitrogen-induced 2 x 2 reconstructed as well as non-reconstructed surface modifications could be generated and on the N-polar surface non-reconstructed. The different surface modifications differ considerably in the formation of surface states. The Ga-induced and N-induced 2 x 2 reconstructed surfaces presented two surface states (SS) at 1.4 eV and 3 eV as well as 2 eV and 3 eV, respectively. The non-reconstructed GaN(0001) presented three SS (1.5 eV, 2.5 eV and 3.4 eV) and the GaN(000-1) one SS (2.5 eV). The theoretical predicted surfaces sates (density functional theory) shows a good agreement with the measurements. The analysis revealed a dependence of the interaction of GaN surfaces with O{sub 2} and H{sub 2}O on the orientation, reconstruction, and surface termination of the films. The GaN(000-1) surface is much more reactive to oxygen and water than the (0001) orientated surfaces, while GaN is in general significantly more sensitive to water than to oxygen. The chemical bond configuration of the adsorbed species shows a significant dependence on surface termination. The measurements presented that the formation of nitrogen oxide and/or gallium oxide bonds depends on the surface modification. Furthermore the interaction

  6. High Quality, Low Cost Bulk Gallium Nitride Substrates Grown by the Electrochemical Solution Growth Method

    Energy Technology Data Exchange (ETDEWEB)

    Seacrist, Michael [SunEdison Inc., St. Peters, MO (United States)

    2017-08-15

    The objective of this project was to develop the Electrochemical Solution Growth (ESG) method conceived / patented at Sandia National Laboratory into a commercially viable bulk gallium nitride (GaN) growth process that can be scaled to low cost, high quality, and large area GaN wafer substrate manufacturing. The goal was to advance the ESG growth technology by demonstrating rotating seed growth at the lab scale and then transitioning process to prototype commercial system, while validating the GaN material and electronic / optical device quality. The desired outcome of the project is a prototype commercial process for US-based manufacturing of high quality, large area, and lower cost GaN substrates that can drive widespread deployment of energy efficient GaN-based power electronic and optical devices. In year 1 of the project (Sept 2012 – Dec 2013) the overall objective was to demonstrate crystalline GaN growth > 100um on a GaN seed crystal. The development plan included tasks to demonstrate and implement a method for purifying reagent grade salts, develop the reactor 1 process for rotating seed Electrochemical Solution Growth (ESG) of GaN, grow and characterize ESG GaN films, develop a fluid flow and reaction chemistry model for GaN film growth, and design / build an improved growth reactor capable of scaling to 50mm seed diameter. The first year’s project objectives were met in some task areas including salt purification, film characterization, modeling, and reactor 2 design / fabrication. However, the key project objective of the growth of a crystalline GaN film on the seed template was not achieved. Amorphous film growth on the order of a few tenths of a micron has been detected with a film composition including Ga and N, plus several other impurities originating from the process solution and hardware. The presence of these impurities, particularly the oxygen, has inhibited the demonstration of crystalline GaN film growth on the seed template. However, the

  7. Vertical 2D/3D Semiconductor Heterostructures Based on Epitaxial Molybdenum Disulfide and Gallium Nitride.

    Science.gov (United States)

    Ruzmetov, Dmitry; Zhang, Kehao; Stan, Gheorghe; Kalanyan, Berc; Bhimanapati, Ganesh R; Eichfeld, Sarah M; Burke, Robert A; Shah, Pankaj B; O'Regan, Terrance P; Crowne, Frank J; Birdwell, A Glen; Robinson, Joshua A; Davydov, Albert V; Ivanov, Tony G

    2016-03-22

    When designing semiconductor heterostructures, it is expected that epitaxial alignment will facilitate low-defect interfaces and efficient vertical transport. Here, we report lattice-matched epitaxial growth of molybdenum disulfide (MoS2) directly on gallium nitride (GaN), resulting in high-quality, unstrained, single-layer MoS2 with strict registry to the GaN lattice. These results present a promising path toward the implementation of high-performance electronic devices based on 2D/3D vertical heterostructures, where each of the 3D and 2D semiconductors is both a template for subsequent epitaxial growth and an active component of the device. The MoS2 monolayer triangles average 1 μm along each side, with monolayer blankets (merged triangles) exhibiting properties similar to that of single-crystal MoS2 sheets. Photoluminescence, Raman, atomic force microscopy, and X-ray photoelectron spectroscopy analyses identified monolayer MoS2 with a prominent 20-fold enhancement of photoluminescence in the center regions of larger triangles. The MoS2/GaN structures are shown to electrically conduct in the out-of-plane direction, confirming the potential of directly synthesized 2D/3D semiconductor heterostructures for vertical current flow. Finally, we estimate a MoS2/GaN contact resistivity to be less than 4 Ω·cm(2) and current spreading in the MoS2 monolayer of approximately 1 μm in diameter.

  8. Electron-phonon relaxation and excited electron distribution in gallium nitride

    Energy Technology Data Exchange (ETDEWEB)

    Zhukov, V. P. [Institute of Solid State Chemistry, Urals Branch of the Russian Academy of Sciences, Pervomayskaya st. 91, Yekaterinburg (Russian Federation); Donostia International Physics Center (DIPC), P. Manuel de Lardizabal 4, 20018 San Sebastian (Spain); Tyuterev, V. G., E-mail: valtyut00@mail.ru [Donostia International Physics Center (DIPC), P. Manuel de Lardizabal 4, 20018 San Sebastian (Spain); Tomsk State Pedagogical University, Kievskaya st. 60, Tomsk (Russian Federation); Tomsk State University, Lenin st. 36, Tomsk (Russian Federation); Chulkov, E. V. [Donostia International Physics Center (DIPC), P. Manuel de Lardizabal 4, 20018 San Sebastian (Spain); Tomsk State University, Lenin st. 36, Tomsk (Russian Federation); Departamento de Fisica de Materiales, Facultad de Ciencias Qumicas, UPV/EHU and Centro de Fisica de Materiales CFM-MPC and Centro Mixto CSIC-UPV/EHU, Apdo. 1072, 20080 San Sebastian (Spain); Echenique, P. M. [Donostia International Physics Center (DIPC), P. Manuel de Lardizabal 4, 20018 San Sebastian (Spain); Departamento de Fisica de Materiales, Facultad de Ciencias Qumicas, UPV/EHU and Centro de Fisica de Materiales CFM-MPC and Centro Mixto CSIC-UPV/EHU, Apdo. 1072, 20080 San Sebastian (Spain)

    2016-08-28

    We develop a theory of energy relaxation in semiconductors and insulators highly excited by the long-acting external irradiation. We derive the equation for the non-equilibrium distribution function of excited electrons. The solution for this function breaks up into the sum of two contributions. The low-energy contribution is concentrated in a narrow range near the bottom of the conduction band. It has the typical form of a Fermi distribution with an effective temperature and chemical potential. The effective temperature and chemical potential in this low-energy term are determined by the intensity of carriers' generation, the speed of electron-phonon relaxation, rates of inter-band recombination, and electron capture on the defects. In addition, there is a substantial high-energy correction. This high-energy “tail” largely covers the conduction band. The shape of the high-energy “tail” strongly depends on the rate of electron-phonon relaxation but does not depend on the rates of recombination and trapping. We apply the theory to the calculation of a non-equilibrium distribution of electrons in an irradiated GaN. Probabilities of optical excitations from the valence to conduction band and electron-phonon coupling probabilities in GaN were calculated by the density functional perturbation theory. Our calculation of both parts of distribution function in gallium nitride shows that when the speed of the electron-phonon scattering is comparable with the rate of recombination and trapping then the contribution of the non-Fermi “tail” is comparable with that of the low-energy Fermi-like component. So the high-energy contribution can essentially affect the charge transport in the irradiated and highly doped semiconductors.

  9. Growth of III-V nitride materials by MOCVD for device applications

    Science.gov (United States)

    Eiting, Christopher James

    This dissertation describes an investigation of the growth of gallium nitride (GaN) and aluminum gallium nitride (AlxGa1-x N) semiconductor materials by metalorganic chemical vapor deposition (MOCVD) for heterojunction field-effect transistor (HFET) and photodetector device applications. In Chapter I, the III-V nitride material system is discussed, and the current status of growth and device research in this material system is reviewed. Chapter 2 presents a detailed discussion of two important tensor properties of the wurtzite III-V nitrides: elasticity and piezoelectricity. In this discussion, a series of equations are developed that are used throughout this work to calculate properties such as strain, composition, and piezoelectric charge. In Chapter 3, the characterization techniques used to gather data for this dissertation are described. Particular attention is given to x-ray diffraction because of the usefulness and versatility of this technique. Chapter 4 is a description of the MOCVD reactor used to grow all of the films in this work. Chapter 5 presents a complete discussion of the growth and doping of GaN epitaxial layers. This chapter is divided into five sections: buffer layer optimization, GaN:ud growth, GaN:Si growth, Si-implantation of GaN, and GaN:Mg growth. In Chapter 6, the focus shifts to AlGaN epitaxial growth. The first part of the chapter is devoted to the growth and doping of AlGaN layers, while the second part deals with the characteristics of AlGaN/GaN heterostructures. Chapter 7 displays some of the device data from HFETs and photodetectors fabricated from the material described in Chapter 5 and Chapter 6. Finally, this dissertation concludes with Chapter 8, a summary of results and a discussion of potential research for the future.

  10. Determination of nitride nitrogen in irradiated materials

    International Nuclear Information System (INIS)

    Maez, M.A.

    1979-03-01

    A method for determining nitride nitrogen was adapted for analyses of irradiated samples in a hot cell. Sections of stainless steel cladding material or fuel are dissolved remotely using various combinations of H 2 SO 4 , HCl, and HF. The nitrogen is separated from the highly radioactive sample solution by steam distillation using the Kjeldahl method. The collected distillates are moved from the hot cell to an open-front box where they are treated with Nessler's reagents for spectrophotometric measurement. The absorbance is measured at a 410-nm wavelength. The standard deviation for measuring 50 μg of nitrogen is < 2 μg of nitrogen using this method

  11. Bulk Expansion Effect of Gallium-Based Thermal Interface Material

    Science.gov (United States)

    Ding, Yujie; Deng, Zhongshan; Cai, Changli; Yang, Zejun; Yang, Yingbao; Lu, Jinrong; Gao, Yunxia; Liu, Jing

    2017-06-01

    The bulk expansion effect of gallium-based thermal interface materials (GBTIMs) was experimentally disclosed and clarified for the first time. GBTIMs were prepared under low (26 %) and high (96 %) relative humidity for a short (2 h) and long (5 h) time periods. An evident volume expansion phenomenon was observed with adequate humidity. Higher humidity resulted in bigger expansion rate and expansion coefficient. The expansion coefficient could reach surprisingly large value of 1.5 for GBTIMs under 96% relative humidity. Assuming that the volume change was related to chemical reactions in the mixture, SEM and XRD were adopted to determine the structure and phase components of the samples. The gases produced in the expansion process were detected with gas chromatography and a large amount of hydrogen was found. The results indicated that the hydrogen produced by the reaction between gallium oxide \\hbox {Ga}2\\hbox {O} and water in GBTIMs caused the expansion effect. The corroded GBTIMs were mainly composed of gallium oxide \\hbox {Ga}2\\hbox {O}3 and became loose and porous solids after expansion. Thermal conductivity decreased dramatically after the expansion process due to the composition and structure changes. From the view point of application, the ambient humidity and oxidation degree must be controlled during preparation of such thermal interface material to avoid its bulk expansion effect.

  12. Hot-Electron Gallium Nitride Two Dimensional Electron Gas Nano-bolometers For Advanced THz Spectroscopy

    Science.gov (United States)

    Ramaswamy, Rahul

    Two-dimensional electron gas (2DEG) in semiconductor heterostructures was identified as a promising medium for hot-electron bolometers (HEB) in the early 90s. Up until now all research based on 2DEG HEBs is done using high mobility AlGaAs/GaAs heterostructures. These systems have demonstrated very good performance, but only in the sub terahertz (THz) range. However, above ˜0.5 THz the performance of AlGaAs/GaAs detectors drastically deteriorates. It is currently understood, that detectors fabricated from standard AlGaAs/GaAs heterostructures do not allow for reasonable coupling to THz radiation while maintaining high conversion efficiency. In this work we have developed 2DEG HEBs based on disordered Gallium Nitride (GaN) semiconductor, that operate at frequencies beyond 1THz at room temperature. We observe strong free carrier absorption at THz frequencies in our disordered 2DEG film due to Drude absorption. We show the design and fabrication procedures of novel micro-bolometers having ultra-low heat capacities. In this work the mechanism of 2DEG response to THz radiation is clearly identified as bolometric effect through our direct detection measurements. With optimal doping and detector geometry, impedances of 10--100 O have been achieved, which allow integration of these devices with standard THz antennas. We also demonstrate performance of the antennas used in this work in effectively coupling THz radiation to the micro-bolometers through polarization dependence and far field measurements. Finally heterodyne mixing due to hot electrons in the 2DEG micro-bolometer has been performed at sub terahertz frequencies and a mixing bandwidth greater than 3GHz has been achieved. This indicates that the characteristic cooling time in our detectors is fast, less than 50ps. Due to the ultra-low heat capacity; these detectors can be used in a heterodyne system with a quantum cascade laser (QCL) as a local oscillator (LO) which typically provides output powers in the micro

  13. MBE growth of nitride-arsenide materials for long wavelength optoelectronics[Molecular Beam Epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Spruytte, S.G.; Coldren, C.W.; Marshall, A.F.; Larson, M.C.; Harris, J.S.

    2000-07-01

    Group III-Nitride-Arsenides are promising materials for 1.3{micro}m and 1.55{micro}m telecommunications optoelectronic devices grown on GaAs substrates. Nitride-Arsenide materials were grown by molecular beam epitaxy (MBE) using a radio frequency (rf) nitrogen plasma. The plasma conditions that maximize the amount of atomic nitrogen versus molecular nitrogen were determined using the emission spectrum of the plasma. Under constant plasma source conditions and varying group III flux, the nitrogen concentration in the film is inversely proportional to the group III flux (i.e., the nitrogen sticking coefficient is unity). The relationship between nitrogen concentration in the film and lattice parameter of the film is not linear for nitrogen concentrations above 2.9 mole % GaN, indicating that some nitrogen is incorporated on other locations than the group V lattice sites. For films with these higher nitrogen concentrations, XPS indicates that the nitrogen exists in two configurations: a Gallium-Nitrogen bond and another type of nitrogen complex in which nitrogen is less strongly bonded to Gallium atoms. Annealing removes this nitrogen complex and allows some of the nitrogen to diffuse out of the film. Annealing also improves the crystal quality of GaAsN quantum wells.

  14. High-power X- and Ka-band Gallium Nitride Amplifiers with Exceptional Efficiency Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Achieving very high-power amplification with maximum efficiency at X- and Ka-band is challenging using solid-state technology. Gallium Arsenide (GaAs) has been the...

  15. Investigation of a Simplified Mechanism Model for Prediction of Gallium Nitride Thin Film Growth through Numerical Analysis

    Directory of Open Access Journals (Sweden)

    Chih-Kai Hu

    2017-03-01

    Full Text Available A numerical procedure was performed to simplify the complicated mechanism of an epitaxial thin-film growth process. In this study, three numerical mechanism models are presented for verifying the growth rate of the gallium nitride (GaN mechanism. The mechanism models were developed through rate of production analysis. All of the results can be compared in one schematic diagram, and the differences among these three mechanisms are pronounced at high temperatures. The simplified reaction mechanisms were then used as input for a two-dimensional computational fluid dynamics code FLUENT, enabling the accurate prediction of growth rates. Validation studies are presented for two types of laboratory-scale reactors (vertical and horizontal. A computational study including thermal and flow field was also performed to investigate the fluid dynamic in those reactors. For each study, the predictions agree acceptably well with the experimental data, indicating the reasonable accuracy of the reaction mechanisms.

  16. Low Damage, High Anisotropy Inductively Coupled Plasma for Gallium Nitride based Devices

    KAUST Repository

    Ibrahim, Youssef H.

    2013-05-27

    Group III-nitride semiconductors possess unique properties, which make them versatile materials for suiting many applications. Structuring vertical and exceptionally smooth GaN profiles is crucial for efficient optical device operation. The processing requirements for laser devices and ridge waveguides are stringent as compared to LEDs and other electronic devices. Due to the strong bonding and chemically inert nature of GaN, dry etching becomes a critical fabrication step. The surface morphology and facet etch angle are analyzed using SEM and AFM measurements. The influence of different mask materials is also studied including Ni as well as a SiO2 and resist bilayer. The high selectivity Ni Mask is found to produce high sidewall angles ~79°. Processing parameters are optimized for both the mask material and GaN in order to achieve a highly anisotropic, smooth profile, without resorting to additional surface treatment steps. An optimizing a SF6/O2 plasma etch process resulted in smooth SiO2 mask sidewalls. The etch rate and GaN surface roughness dependence on the RF power was also examined. Under a low 2mTorr pressure, the RF and ICP power were optimized to 150W and 300W respectively, such that a smooth GaN morphology and sidewalls was achieved with reduced ion damage. The The AFM measurements of the etched GaN surface indicate a low RMS roughness ranging from 4.75 nm to 7.66 nm.

  17. Gallium Nitride (GaN) Monolithic Microwave Integrated Circuit (MMIC) Designs Submitted to Air Force Research Laboratory (AFRL) Sponsored Qorvo Fabrication

    Science.gov (United States)

    2017-07-01

    ARL-TN-0835● July 2017 US Army Research Laboratory Gallium Nitride (GaN) Monolithic Microwave Integrated Circuit (MMIC) Designs...distribution is unlimited. NOTICES Disclaimers The findings in this report are not to be construed as an official Department of the Army...approval of the use thereof. Destroy this report when it is no longer needed. Do not return it to the originator. ARL-TN-0835 ● JULY

  18. Properties of Er and Yb Doped Gallium nitride layers fabricated by magnetron sputtering

    Czech Academy of Sciences Publication Activity Database

    Prajzler, V.; Burian, Z.; Hüttel, I.; Špirková, J.; Hamáček, J.; Oswald, J.; Zavadil, Jiří; Peřina, Vratislav

    2006-01-01

    Roč. 46, č. 6 (2006), s. 49-55 ISSN 1210-2709 R&D Projects: GA ČR(CZ) GA102/06/0424 Institutional research plan: CEZ:AV0Z20670512; CEZ:AV0Z10480505 Keywords : fluorescence * gallium * rare earth compounds Subject RIV: BM - Solid Matter Physics ; Magnetism

  19. Interlayer interaction and mechanical properties in multi-layer graphene, Boron-Nitride, Aluminum-Nitride and Gallium-Nitride graphene-like structure: A quantum-mechanical DFT study

    Science.gov (United States)

    Ghorbanzadeh Ahangari, Morteza; Fereidoon, A.; Hamed Mashhadzadeh, Amin

    2017-12-01

    In present study, we investigated mechanical, electronic and interlayer properties of mono, bi and 3layer of Boron-Nitride (B-N), Aluminum-Nitride (Al-N) and Gallium-Nitride (Ga-N) graphene sheets and compared these results with results obtained from carbonic graphenes (C-graphenes). For reaching this purpose, first we optimized the geometrical parameters of these graphenes by using density functional theory (DFT) method. Then we calculated Young's modulus of graphene sheet by compressing and then elongating these sheets in small increment. Our results indicates that Young's modulus of graphenes didn't changed obviously by increasing the number of layer sheet. We also found that carbonic graphene has greatest Young's modulus among another mentioned sheets because of smallest equilibrium distance between its elements. Next we modeled the van der Waals interfacial interaction exist between two sheets with classical spring model by using general form of Lennard-Jones (L-J) potential for all of mentioned graphenes. For calculating L-J parameters (ε and σ), the potential energy between layers of mentioned graphene as a function of the separation distance was plotted. Moreover, the density of states (DOS) are calculated to understand the electronic properties of these systems better.

  20. Challenges for critical raw material recovery from WEEE - The case study of gallium.

    Science.gov (United States)

    Ueberschaar, Maximilian; Otto, Sarah Julie; Rotter, Vera Susanne

    2017-02-01

    Gallium and gallium compounds are more frequently used in future oriented technologies such as photovoltaics, light diodes and semiconductor technology. In the long term the supply risk is estimated to be critical. Germany is one of the major primary gallium producer, recycler of gallium from new scrap and GaAs wafer producer. Therefore, new concepts for a resource saving handling of gallium and appropriate recycling strategies have to be designed. This study focus on options for a possible recycling of gallium from waste electric and electronic equipment. To identify first starting points, a substance flow analysis was carried out for gallium applied in integrated circuits applied on printed circuit boards and for LEDs used for background lighting in Germany in 2012. Moreover, integrated circuits (radio amplifier chips) were investigated in detail to deduce first approaches for a recycling of such components. An analysis of recycling barriers was carried out in order to investigate general opportunities and risks for the recycling of gallium from chips and LEDs. Results show, that significant gallium losses arose in primary production and in waste management. 93±11%, equivalent to 43,000±4700kg of the total gallium potential was lost over the whole primary production process until applied in electronic goods. The largest share of 14,000±2300kggallium was lost in the production process of primary raw materials. The subsequent refining process was related to additional 6900±3700kg and the chip and wafer production to 21,700±3200kg lost gallium. Results for the waste management revealed only low collection rates for related end-of-life devices. Not collected devices held 300 ± 200 kg gallium. Due to the fact, that current waste management processes do not recover gallium, further 80 ± 10 kg gallium were lost. A thermal pre-treatment of the chips, followed by a manual separation allowed an isolation of gallium rich fractions, with gallium mass fractions up to

  1. Preparation of gallium nitride surfaces for atomic layer deposition of aluminum oxide.

    Science.gov (United States)

    Kerr, A J; Chagarov, E; Gu, S; Kaufman-Osborn, T; Madisetti, S; Wu, J; Asbeck, P M; Oktyabrsky, S; Kummel, A C

    2014-09-14

    A combined wet and dry cleaning process for GaN(0001) has been investigated with XPS and DFT-MD modeling to determine the molecular-level mechanisms for cleaning and the subsequent nucleation of gate oxide atomic layer deposition (ALD). In situ XPS studies show that for the wet sulfur treatment on GaN(0001), sulfur desorbs at room temperature in vacuum prior to gate oxide deposition. Angle resolved depth profiling XPS post-ALD deposition shows that the a-Al2O3 gate oxide bonds directly to the GaN substrate leaving both the gallium surface atoms and the oxide interfacial atoms with XPS chemical shifts consistent with bulk-like charge. These results are in agreement with DFT calculations that predict the oxide/GaN(0001) interface will have bulk-like charges and a low density of band gap states. This passivation is consistent with the oxide restoring the surface gallium atoms to tetrahedral bonding by eliminating the gallium empty dangling bonds on bulk terminated GaN(0001).

  2. Iron Carbides and Nitrides: Ancient Materials with Novel Prospects.

    Science.gov (United States)

    Ye, Zhantong; Zhang, Peng; Lei, Xiang; Wang, Xiaobai; Zhao, Nan; Yang, Hua

    2018-02-07

    Iron carbides and nitrides have aroused great interest in researchers, due to their excellent magnetic properties, good machinability and the particular catalytic activity. Based on these advantages, iron carbides and nitrides can be applied in various areas such as magnetic materials, biomedical, photo- and electrocatalysis. In contrast to their simple elemental composition, the synthesis of iron carbides and nitrides still has great challenges, particularly at the nanoscale, but it is usually beneficial to improve performance in corresponding applications. In this review, we introduce the investigations about iron carbides and nitrides, concerning their structure, synthesis strategy and various applications from magnetism to the catalysis. Furthermore, the future prospects are also discussed briefly. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Low-cost growth of magnesium doped gallium nitride thin films by sol-gel spin coating method

    Science.gov (United States)

    Amin, N. Mohd; Ng, S. S.

    2018-01-01

    Low-cost sol-gel spin coating growth of magnesium (Mg) doped gallium nitride (GaN) thin films with different concentrations of Mg was reported. The effects of the Mg concentration on the structural, surface morphology, elemental compositions, lattice vibrational, and electrical properties of the deposited films were investigated. X-ray diffraction results show that the Mg-doped samples have wurtzite structure with preferred orientation of GaN(002). The crystallite size decreases and the surface of the films with pits/pores were formed, while the crystalline quality of the films degraded as the Mg concentration increases from 2% to 6. %. All the Raman active phonon modes of the wurtzite GaN were observed while a broad peak attributed to the Mg-related lattice vibrational mode was detected at 669 cm-1. Hall effect results show that the resistivity of the thin films decreases while the hole concentration and hall mobility of thin films increases as the concentration of the Mg increases.

  4. Study of the dosimetric response of Gallium Nitride (GaN): modeling, simulation and characterization on radiotherapy

    International Nuclear Information System (INIS)

    Wang, Ruoxi

    2015-01-01

    The work in this thesis has the objective to increase the measurement precision of the dosimetry based on the Gallium Nitride (GaN) transducer and develop its applications on radiotherapy. The study includes the aspects of modeling, simulation and characterization of this response in external radiotherapy and brachytherapy. In modeling, we have proposed two approaches to model the GaN transducer's response in external radiotherapy. For the first approach, a model has been built based on experimental data, while separating the primary and scattering component of the beam. For the second approach, we have adopted a response model initially developed for the silicon diodes for the GaN radioluminescent transducer. We have also proposed an original concept of bi-media dosimetry which evaluates the dose in tissue according to different responses from two media without prior information on the conditions of irradiation. This concept has been shown by Monte Carlo simulation. Moreover, for High Dose Rate brachytherapy, the response of GaN transducer irradiated by iridium 192 and cobalt 60 sources has been evaluated by Monte Carlo simulation and confirmed by the measurements. Studies on the property characterization of GaN radioluminescent transducer has been carried out with these sources as well. An instrumented phantom prototype with GaN probe has been developed for the HDR brachytherapy quality control. It allows a real-time verification of the physics parameters of a treatment (source dwell position, source dwell time, source activity). (author) [fr

  5. Effect of gas flow on the selective area growth of gallium nitride via metal organic vapor phase epitaxy

    Science.gov (United States)

    Rodak, L. E.; Kasarla, K. R.; Korakakis, D.

    2007-08-01

    The effect of gas flow on the selective area growth (SAG) of gallium nitride (GaN) grown via metal organic vapor phase epitaxy (MOVPE) has been investigated. In this study, the SAG of GaN was carried out on a silicon dioxide striped pattern along the GaN direction. SAG was initiated with the striped pattern oriented parallel and normal to the incoming gas flow in a horizontal reactor. The orientation of the pattern did not impact cross section of the structure after re-growth as both orientations resulted in similar trapezoidal structures bounded by the (0 0 0 1) and {1 1 2¯ n} facets ( n≈1.7-2.2). However, the growth rates were shown to depend on the orientation of the pattern as the normally oriented samples exhibited enhanced vertical and cross-sectional growth rates compared to the parallel oriented samples. All growths occurred under identical conditions and therefore the difference in growth rates must be attributed to a difference in mass transport of species.

  6. Molecular beam epitaxy of germanium nanoclusters and indium gallium nitride thin films

    Science.gov (United States)

    Liu, Bing

    made by electron bean lithography and chlorine plasma etching. By minimizing the sizes of the patterns, laterally well-ordered arrays of Ge islands are achieved, and the mechanisms of the preferential nucleation of Ge islands at certain sites are examined. Next, another important issue of preserving the two-dimensional growth of Ge on silicon by intentionally introducing some impurities (surfactants) during growth to suppress the three-dimensional Ge island formation is investigated. In particular, arsenic as a surfactant is studied. The role of arsenic in MBE of Ge on Si(100) is proposed to be both associated with reduction of Ge adatom surface diffusion and chemically decorating the surface atomic steps to increase the reactivity of the steps with the Ge adatoms. Finally, I present studies of MBE of group III-nitride materials. The bulk strain of InGaN is first calculated using a simplified valence force field method. A phase diagram of InGaN is obtained for an overview of the thermodynamic properties of these materials. MBE experiments of GaN and InGaN thin films are then performed using both an electron cyclotron resonance (ECR) plasma and ammonia as the nitrogen sources. Thick GaN films of good crystal qualities and smooth surfaces are obtained by introducing a small amount of indium as a surfactant. InxGa1-xN films with different indium fraction x are also achieved by balancing the major growth parameters such as the substrate temperature and In/Ga flux ratio. The mechanisms of the film growth and evolution are discussed.

  7. Wet chemical functionalization of III-V semiconductor surfaces: alkylation of gallium arsenide and gallium nitride by a Grignard reaction sequence.

    Science.gov (United States)

    Peczonczyk, Sabrina L; Mukherjee, Jhindan; Carim, Azhar I; Maldonado, Stephen

    2012-03-13

    Crystalline gallium arsenide (GaAs) (111)A and gallium nitride (GaN) (0001) surfaces have been functionalized with alkyl groups via a sequential wet chemical chlorine activation, Grignard reaction process. For GaAs(111)A, etching in HCl in diethyl ether effected both oxide removal and surface-bound Cl. X-ray photoelectron (XP) spectra demonstrated selective surface chlorination after exposure to 2 M HCl in diethyl ether for freshly etched GaAs(111)A but not GaAs(111)B surfaces. GaN(0001) surfaces exposed to PCl(5) in chlorobenzene showed reproducible XP spectroscopic evidence for Cl-termination. The Cl-activated GaAs(111)A and GaN(0001) surfaces were both reactive toward alkyl Grignard reagents, with pronounced decreases in detectable Cl signal as measured by XP spectroscopy. Sessile contact angle measurements between water and GaAs(111)A interfaces after various levels of treatment showed that GaAs(111)A surfaces became significantly more hydrophobic following reaction with C(n)H(2n-1)MgCl (n = 1, 2, 4, 8, 14, 18). High-resolution As 3d XP spectra taken at various times during prolonged direct exposure to ambient lab air indicated that the resistance of GaAs(111)A to surface oxidation was greatly enhanced after reaction with Grignard reagents. GaAs(111)A surfaces terminated with C(18)H(37) groups were also used in Schottky heterojunctions with Hg. These heterojunctions exhibited better stability over repeated cycling than heterojunctions based on GaAs(111)A modified with C(18)H(37)S groups. Raman spectra were separately collected that suggested electronic passivation by surficial Ga-C bonds at GaAs(111)A. Specifically, GaAs(111)A surfaces reacted with alkyl Grignard reagents exhibited Raman signatures comparable to those of samples treated with 10% Na(2)S in tert-butanol. For GaN(0001), high-resolution C 1s spectra exhibited the characteristic low binding energy shoulder demonstrative of surface Ga-C bonds following reaction with CH(3)MgCl. In addition, 4

  8. Simultaneous specimen current and time-dependent cathodoluminescence measurements on gallium nitride

    Energy Technology Data Exchange (ETDEWEB)

    Campo, E. M., E-mail: e.campo@bangor.ac.uk; Hopkins, L. [School of Electronic Engineering, Bangor University, Gwynedd LL57 1UT (United Kingdom); Pophristic, M. [Department of Chemistry and Biochemistry, University of the Science, Philadelphia, Pennsylvania 19104 (United States); Ferguson, I. T. [Department of Electrical and Computer Engineering, Missouri University of Science and Technology, Rolla, Missouri 65409 (United States)

    2016-06-28

    Time-dependent cathodoluminescence (CL) and specimen current (SC) are monitored to evaluate trapping behavior and evolution of charge storage. Examination of CL and SC suggests that the near band edge emission in GaN is reduced primarily by the activation of traps upon irradiation, and Gallium vacancies are prime candidates. At the steady state, measurement of the stored charge by empiric-analytical methods suggests that all available traps within the interaction volume have been filled, and that additional charge is being stored interstitially, necessarily beyond the interaction volume. Once established, the space charge region is responsible for the steady state CL emission and, prior to build up, it is responsible for the generation of diffusion currents. Since the non-recombination effects resulting from diffusion currents that develop early on are analogous to those leading to device failure upon aging, this study is fundamental toward a holistic insight into optical properties in GaN.

  9. Synthesis of gallium nitride and related oxides via ammonobasic reactive sublimation (ARS)

    Energy Technology Data Exchange (ETDEWEB)

    Hernández-Hernández, Luis Alberto; Aguilar-Hernández, Jorge R.; Mejía-García, Concepción; Cruz-Gandarilla, Francisco; Contreras-Puente, Gerardo [Escuela Superior de Física y Matemáticas, Instituto Politécnico Nacional, Ciudad de México (Mexico); Moure-Flores, Francisco de [Facultad de Química, Materiales-Energía, Universidad Autónoma de Querétaro (Mexico); Melo-Pereira, Osvaldo de, E-mail: schwarzerengelxv@hotmail.com [Facultad de Física, Universidad de La Habana, La Habana (Cuba)

    2017-11-15

    Ammonobasic reactive sublimation (ARS) is proposed as a novel method to synthesize GaN and related oxides. Results indicate that GaN growth occurs by a nitriding process of Ga and related oxides, establishing a direct dependence on NH{sub 4} OH amount added as a primary chemical reactive. The samples were grown on p-type Si (111) substrates inside a tube furnace, employing GaN powder and NH{sub 4} OH. The characterizations of the samples were carried out by XRD, SEM, EDS and PL techniques, revealing the influence of NH{sub 4} OH on the improvement of GaN synthesis and the enhancement of its optical and structural properties. (author)

  10. Thermal Conductivity of Wurtzite Zinc-Oxide from First-Principles Lattice Dynamics – a Comparative Study with Gallium Nitride

    Science.gov (United States)

    Wu, Xufei; Lee, Jonghoon; Varshney, Vikas; Wohlwend, Jennifer L.; Roy, Ajit K.; Luo, Tengfei

    2016-01-01

    Wurtzite Zinc-Oxide (w-ZnO) is a wide bandgap semiconductor that holds promise in power electronics applications, where heat dissipation is of critical importance. However, large discrepancies exist in the literature on the thermal conductivity of w-ZnO. In this paper, we determine the thermal conductivity of w-ZnO using first-principles lattice dynamics and compare it to that of wurtzite Gallium-Nitride (w-GaN) – another important wide bandgap semiconductor with the same crystal structure and similar atomic masses as w-ZnO. However, the thermal conductivity values show large differences (400 W/mK of w-GaN vs. 50 W/mK of w-ZnO at room temperature). It is found that the much lower thermal conductivity of ZnO originates from the smaller phonon group velocities, larger three-phonon scattering phase space and larger anharmonicity. Compared to w-GaN, w-ZnO has a smaller frequency gap in phonon dispersion, which is responsible for the stronger anharmonic phonon scattering, and the weaker interatomic bonds in w-ZnO leads to smaller phonon group velocities. The thermal conductivity of w-ZnO also shows strong size effect with nano-sized grains or structures. The results from this work help identify the cause of large discrepancies in w-ZnO thermal conductivity and will provide in-depth understanding of phonon dynamics for the design of w-ZnO-based electronics. PMID:26928396

  11. Development of a Photoelectrochemical Etch Process to Enable Heterogeneous Substrate Integration of Epitaxial III-Nitride Semiconductors

    Science.gov (United States)

    2017-12-01

    and Acronyms Al2O3 aluminum oxide (sapphire) AlN aluminum nitride AlGaN aluminum gallium nitride Au gold BCl3 boron trichloride (gas) Black...Approved for public release; distribution is unlimited. 1 1. Introduction The III-nitride class of materials ( aluminum nitride [AlN], gallium...on which these materials are grown have been mostly limited to aluminum oxide (Al2O3, single-crystal sapphire), a GaN-on-sapphire template, or free

  12. State and prospects of Russian and world gallium market

    Directory of Open Access Journals (Sweden)

    F. D. Larichkin

    2017-12-01

    Full Text Available The authors consider the state of Russian and world mineral and raw materials base of gallium, the main spheres of application in various branches and industries of the national economy. The article presents the generalization and analysis of trends in world and Russian production, consumption of rare metal and its compounds, the world trade and global market of gallium and products based on it, consuming it in new science-intensive innovative industries, including the production of military equipment. The unique chemical properties of gallium remained unclaimed for a long time. Only after the discovery of the semiconductor properties of gallium compounds has the situation radically changed: the rate of growth in production and consumption of metallic gallium at the end of the twentieth and beginning of the 21st century amounted to an average of more than 8% per year. The largest area of consumption of gallium is the production of semiconductor materialsgallium arsenide (GaAs and gallium nitride (GaN. The areas of application of gallium not related to the semiconductor industry are very small. Industry structure of consumption of GaAs and GaN: in integrated circuits is 66%; optoelectronic devices (light-emitting diodes, laser diodes, photodetectors and solar batteries – 20%; the remaining 14% – scientific research, special alloys, etc. Optoelectronic devices are used in aerospace industry, consumer goods, industrial and medical equipment and telecommunications. Integral circuits are used in the military industry, high-power computers and electronic communications. The most significant growing sectors of the market are LEDs, electronics based on gallium nitride and solar cells. Solar energy has become the fastest growing branch of the world economy. The volumes of gallium production in Russia do not correspond to its raw material, scientific and technological potential as the country and require the development activation based on state

  13. Nitrides

    International Nuclear Information System (INIS)

    Uehlls, A.

    1987-01-01

    The structure and certain properties of the ionic and covalent nitrides of alkali earth, rare earth, transition elements, cadmium, boron, indium and thorium are considered briefly. Peculiarities of the crystal structure, the structure of coordinated polyhedrons, the character and parameters of chemical bond depending on nitride composition are discussed

  14. Opaque gallium nitride photocathodes in UV imaging detectors with microchannel plates

    Science.gov (United States)

    Tremsin, Anton S.; Hull, Jeffrey S.; Siegmund, Oswald H. W.; McPhate, Jason B.; Vallerga, John V.; Dabiran, Amir M.; Mane, Anil; Elam, Jeff

    2013-09-01

    The optimization and performance of opaque Galium Nitride (GaN) photocathodes deposited directly on novel Microchannel Plates (MCPs) are presented in this paper. The novel borosilicate glass MCPs, which are manufactured with the help of Atomic Layer Deposition, can withstand higher temperatures enabling direct deposition of GaN films on their surfaces. The quantum efficiency of MBE-grown GaN photocathodes of various thickness and buffer layers was studied in the spectral range of ~200-400 nm for the films grown on different surface layers (such as Al2O3 or buffer AlN layer) in order to determine the optimal opaque photocathode configuration. The MCPs with the GaN photocathodes were activated with surface cesiation in order to achieve the negative Electron Affinity for the efficient photon detection. The opaque photocathodes enable substantial broadening of the spectral sensitivity range compared to the semitransparent configuration when the photocathodes are deposited on the input window. The design of currently processed sealed tube event counting detector with an opaque GaN photocathode are also described in this paper. Our experiments demonstrate that although there is still development work required the detection quantum efficiencies exceeding 20% level should be achievable in 200-400 nm range and <50% in 100-200 nm range for the event counting MCP detectors with high spatial resolution (better than 50 μm) and timing resolution of <100 ps and very low background levels of only few events cm-2 s-1.

  15. Gallium nitride-dielectric interface formation for gate dielectrics and passivation layers using remote plasma processing

    Science.gov (United States)

    Bae, Choelhwyi

    In previous studies, device quality Si-SiO2 interfaces and dielectric bulk films (SiO2) were prepared using a two-step process; (i) remote plasma-assisted oxidation (RPAO) to form a superficially interfacial oxide (˜0.6 nm) and (ii) remote plasma enhanced chemical vapor deposition (RPECVD) to deposit the oxide film. The same approach has been applied to the GaN-SiO2 system. After a 300°C remote N2/He plasma treatment of the GaN surface, residual C and Cl were reduced below Auger electron spectroscopy (AES) detection, and the AES peak ratio of O KLL and N KLL was ˜0.06 or ˜0.1 monolayer of oxygen. RPAO of GaN surfaces using O2, N2O, and N 2O in N2 source gases were investigated by on-line AES to determine the oxidation kinetics and chemical composition of the interfacial oxide. Without an RPAO step, subcutaneous oxidation of GaN takes place during RPECVD deposition of SiO2, and on-line AES indicates a ˜0.7 nm subcutaneous oxide. Compared to single step SiO2 deposition, significantly reduced interface state density (Dit) was obtained at the GaN-SiO2 interface by independent control of GaN-Ga2O3 interface formation by thin RPAO oxide (˜1 nm) and SiO2 film deposition by RPECVD. High-low frequency method and conductance method indicate that Dit of GaN Metal-Oxide-Semiconductor (MOS) sample without RPAO is ˜5 times larger than that of the sample with RPAO. For the GaN MOS structures with remote plasma-assisted oxidation and nitridation, determined values of D it were in the range of low-to-mid x 1011 cm-2eV-1. Also, we report on high temperature and photo-assisted capacitance-voltage (C-V) characteristics.

  16. Interface Study on Amorphous Indium Gallium Zinc Oxide Thin Film Transistors Using High-k Gate Dielectric Materials

    Directory of Open Access Journals (Sweden)

    Yu-Hsien Lin

    2015-01-01

    Full Text Available We investigated amorphous indium gallium zinc oxide (a-IGZO thin film transistors (TFTs using different high-k gate dielectric materials such as silicon nitride (Si3N4 and aluminum oxide (Al2O3 at low temperature process (<300°C and compared them with low temperature silicon dioxide (SiO2. The IGZO device with high-k gate dielectric material will expect to get high gate capacitance density to induce large amount of channel carrier and generate the higher drive current. In addition, for the integrating process of integrating IGZO device, postannealing treatment is an essential process for completing the process. The chemical reaction of the high-k/IGZO interface due to heat formation in high-k/IGZO materials results in reliability issue. We also used the voltage stress for testing the reliability for the device with different high-k gate dielectric materials and explained the interface effect by charge band diagram.

  17. III-Nitrides growth and AlGaN/GaN heterostructures on ferroelectric materials

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Kyoung-Keun [Georgia Institute of Technology, School of Electrical and Computer Engineering, 777 Atlantic Dr., Atlanta, GA 30332 (United States); Namkoong, Gon [Old Dominion University, Department of Electrical and Computer Engineering, Norfolk, VA 23529 (United States); Madison, Shannon M. [Georgia Institute of Technology, School of Electrical and Computer Engineering, 777 Atlantic Dr., Atlanta, GA 30332 (United States); Ralph, Stephen E. [Georgia Institute of Technology, School of Electrical and Computer Engineering, 777 Atlantic Dr., Atlanta, GA 30332 (United States); Doolittle, W. Alan [Georgia Institute of Technology, School of Electrical and Computer Engineering, 777 Atlantic Dr., Atlanta, GA 30332 (United States)]. E-mail: alan.doolittle@ece.gatech.edu; Losurdo, Maria [Institute of Inorganic Methodologies and of Plasmas, IMIP-CNR, Department of Chemistry, University of Bari, via Orabona, 4 70126 Bari (Italy); Bruno, Giovanni [Institute of Inorganic Methodologies and of Plasmas, IMIP-CNR, Department of Chemistry, University of Bari, via Orabona, 4 70126 Bari (Italy); Cho, Hyung Koun [Department of Materials Science and Engineering, Sung Kyun Kwan University, Suwon 440-746 (Korea, Republic of)

    2007-06-15

    The growth of III-nitrides on the ferroelectric materials lithium niobate (LN) and lithium tantalate (LT) via molecular beam epitaxy (MBE) using rf plasma source has been investigated. We have found that gallium nitride (GaN) epitaxial layers have a crystalline relationship with lithium niobate (tantalate) as follows: (0 0 0 1) GaN || (0 0 0 1) LN (LT) with [10-10] GaN || [11-20] LN (LT). The surface stability of LN and LT substrates has been monitored by in situ spectroscopic ellipsometry in the vacuum chamber. Three different temperature zones have been discerned; surface degas and loss of OH group (100-350 deg. C); surface segregation/accumulation of Li and O-species (400-700 deg. C); surface evaporation of O-species and Li desorption (over 750 deg. C). However, LT shows only surface degassing in the range of 100-800 deg. C. Therefore, congruent LN substrates were chemically unstable at the growth temperature of 550-650 deg. C, and therefore developed an additional phase of Li-deficient lithium niobate (LiNb{sub 3}O{sub 8}) along with lithium niobate (LiNbO{sub 3}), confirmed by X-ray diffraction. On the other hand, LT showed better chemical stability at these temperatures, with no additional phase development. The structural quality of GaN epitaxial layers has shown slight improvement on LT substrates over LN substrates, according to X-ray diffraction. Herein, we demonstrate AlGaN/GaN heterostructure devices on ferroelectric materials that will allow future development of multifunctional electrical and optical applications.

  18. Acidic ammonothermal growth of gallium nitride in a liner-free molybdenum alloy autoclave

    Science.gov (United States)

    Malkowski, Thomas F.; Pimputkar, Siddha; Speck, James S.; DenBaars, Steven P.; Nakamura, Shuji

    2016-12-01

    This paper discusses promising materials for use as internal, non-load bearing components as well as molybdenum-based alloys for autoclave structural components for an ammonothermal autoclave. An autoclave was constructed from the commercial titanium-zirconium-molybdenum (TZM) alloy and was found to be chemically inert and mechanically stable under acidic ammonothermal conditions. Preliminary seeded growth of GaN was demonstrated with negligible incorporation of transition metals (including molybdenum) into the grown material (560 °C). The possibility of a 'universal', inexpensive, liner-free ammonothermal autoclave capable of exposure to basic and acidic chemistry is demonstrated.

  19. Electrical Activation Studies of Silicon Implanted Aluminum Gallium Nitride with High Aluminum Mole Fraction

    Science.gov (United States)

    2007-12-01

    Marciniak, T. Zens, E. Moore, R. Hengehold Stiener. “ Electrica 283 Implanted AlxGa1-xN,” Journal of Electromagnetic Materials, 35(4): 647-653 36...Proceedings of the 2001:125-130 (2001). 286 68. Fellows, James A., Y. K. Yeo, Mee-Yi Ryu, and R. L. Hengehold. “ Electrica and Optical Activation

  20. Low frequency noise of gallium nitride-based deep ultraviolet light emitting diodes

    Science.gov (United States)

    Sawyer, Shayla Maya Louise

    This study covers the investigation of deep UV GaN-based light emitting diodes using low frequency noise characterization. Using this technique, device improvements were analyzed as feedback to developers and practical parameters were created for system use. AlGaN LEDs emit wavelengths into the deep UV spectral region (lambda food and water sterilization, non-line-of-sight short range communication, counterfeit identification, photolithography, and general white lighting. The current technological trend demonstrates a decrease in material quality and device performance with decreasing wavelength. However, progress has allowed for its commercialization in a relatively short period of time. Characterization of material and device improvements provides feedback for changes in development. Secondly, methods to determine the reliability and stability of these devices are essential to the applications for which they are used. One such method is through optical and current low frequency noise (LFN) measurements in which both system related parameters such as a signal-to-noise ratio for light sources and insight into the fundamental physics within the devices can be determined. The quality of the device can be compared before costly integration into systems that require low noise, high reliability, and optical stability. It not only quantifies performance limiting noise levels, but it is known to be a sensitive, nondestructive measure of material quality and reliability. The research highlighted in this thesis demonstrates a new measurement technique in analyzing the light intensity fluctuations through low frequency optical noise. From this work, a proposed figure-of-merit is presented. Low frequency current noise was performed as a well known indicator of material quality. Each technique compares LEDs grown by SET Inc. LEDs of varying wavelengths along the UV spectrum, with different growth methods and device structures. The cross-correlation between optical and current

  1. Aluminum gallium nitride (GaN)/GaN high electron mobility transistor-based sensors for glucose detection in exhaled breath condensate.

    Science.gov (United States)

    Chu, Byung Hwan; Kang, Byoung Sam; Hung, Sheng Chun; Chen, Ke Hung; Ren, Fan; Sciullo, Andrew; Gila, Brent P; Pearton, Stephen J

    2010-01-01

    Immobilized aluminum gallium nitride (AlGaN)/GaN high electron mobility transistors (HEMTs) have shown great potential in the areas of pH, chloride ion, and glucose detection in exhaled breath condensate (EBC). HEMT sensors can be integrated into a wireless data transmission system that allows for remote monitoring. This technology offers the possibility of using AlGaN/GaN HEMTs for extended investigations of airway pathology of detecting glucose in EBC without the need for clinical visits. HEMT structures, consisting of a 3-microm-thick undoped GaN buffer, 30-A-thick Al(0.3)Ga(0.7)N spacer, and 220-A-thick silicon-doped Al(0.3)Ga(0.7)N cap layer, were used for fabricating the HEMT sensors. The gate area of the pH, chloride ion, and glucose detection was immobilized with scandium oxide (Sc(2)O(3)), silver chloride (AgCl) thin film, and zinc oxide (ZnO) nanorods, respectively. The Sc(2)O(3)-gated sensor could detect the pH of solutions ranging from 3 to 10 with a resolution of approximately 0.1 pH. A chloride ion detection limit of 10(-8) M was achieved with a HEMT sensor immobilized with the AgCl thin film. The drain-source current of the ZnO nanorod-gated AlGaN/GaN HEMT sensor immobilized with glucose oxidase showed a rapid response of less than 5 seconds when the sensor was exposed to the target glucose in a buffer with a pH value of 7.4. The sensor could detect a wide range of concentrations from 0.5 nM to 125 microM. There is great promise for using HEMT-based sensors to enhance the detection sensitivity for glucose detection in EBC. Depending on the immobilized material, HEMT-based sensors can be used for sensing different materials. These electronic detection approaches with rapid response and good repeatability show potential for the investigation of airway pathology. The devices can also be integrated into a wireless data transmission system for remote monitoring applications. This sensor technology could use the exhaled breath condensate to measure the

  2. The Growth of Gallium Nitride Films Via the Innovative Technique of Atomic Layer Epitaxy.

    Science.gov (United States)

    1987-06-01

    of excess incident atoms. Among the materials which have been deposited by ALE to date are ZnS, ZnSe, GaAs, AlI._Ga As, SnTe, GaP, SnO2 , A12 0 3...uppermost layer ,- of the film, excess incident atoms that do not form A-B bonds in the film are allowed to re-evaporate (by making use of the larger...were subsequently polished with 0.1 um diamond paste and then oxidized at 1200°C in flowing dry oxygen for 1.5 h to consume the 50 nm of surface which

  3. Fe-doping in hydride vapor-phase epitaxy for semi-insulating gallium nitride

    Science.gov (United States)

    Richter, E.; Gridneva, E.; Weyers, M.; Tränkle, G.

    2016-12-01

    Fe-doping of GaN layers of 3 in. in diameter and a thickness of 1 mm in a vertical AIX-HVPE reactor is studied. Ferrocen was used as Fe source. It is shown that a sufficient uniformity of growth conditions, a high purity of undoped GaN layers, and a moderate Fe incorporation of 2×1018 cm-3 allow for growth of semi-insulating GaN layers with a sufficiently high specific resistivity even at elevated temperature. This makes the material suitable as substrate for electronic power devices at high power or in harsh ambient.

  4. The Effects of Rare Earth Doping on Gallium Nitride Thin Films

    Science.gov (United States)

    2011-09-01

    6LiF, Cd, U, or Gd coatings as the neutron reactive layer, although the most successful conversion layer devices are based on 10B enriched boron ...l D !J Date v 3o J\\CA.-~ 2olf Date AFIT/DS/ENP/11-S05 Abstract The thermal neutron capture cross section of the rare earth metal isotope 157Gd...is 255,000 barns and is the largest of all known natural isotopes , which distinguishes the material as a logical candidate for neutron detection

  5. Covalent attachment of a peptide to the surface of gallium nitride

    Science.gov (United States)

    Makowski, Matthew S.; Zemlyanov, Dmitry Y.; Lindsey, Jason A.; Bernhard, Jonathan C.; Hagen, Evan M.; Chan, Burke K.; Petersohn, Adam A.; Medow, Matthew R.; Wendel, Lindsay E.; Chen, Dafang; Canter, Jamie M.; Ivanisevic, Albena

    2011-08-01

    The properties of GaN have made it not only an ideal material for high power and high frequency electronic devices, but also a semiconductor suitable for application in biosensing devices. The utilization of GaN in electronic biosensors has increased the importance of characterizing robust and easily implemented organic functionalization methods for GaN surfaces. This work demonstrates and characterizes a route to functionalize the GaN (0001) surface with two organic molecules, hexylamine and a peptide, through olefin cross-metathesis with Grubbs first generation catalyst. The GaN (0001) surface was chlorinated, functionalized with a terminal alkene group using a Grignard reaction, and then terminated with a carboxyl group using an olefin cross-metathesis reaction. With a condensation reaction, the final step in the reaction scheme bound hexylamine or a peptide to the carboxyl terminated GaN surface. Qualitative and quantitative X-ray photoelectron spectroscopy (XPS) data verified the success of each step in the reaction scheme. Surface element composition, adlayer coverages, and adlayer thicknesses were calculated based on the XPS data. At least a monolayer of surface molecules covered the GaN surface.

  6. Graphitic Carbon Nitride Materials: Sensing, Imaging and Therapy.

    Science.gov (United States)

    Dong, Yongqiang; Wang, Qian; Wu, Haishan; Chen, Yingmei; Lu, Chun-Hua; Chi, Yuwu; Yang, Huang-Hao

    2016-10-01

    Graphitic carbon nitrides (g-C 3 N 4 ) are a class of 2D polymeric materials mainly composed of carbon and nitrogen atoms. g-C 3 N 4 are attracting dramatically increasing interest in the areas of sensing, imaging, and therapy, due to their unique optical and electronic properties. Here, the luminescent properties (mainly includes photoluminescence and electrochemiluminescence), and catalytic and photoelectronic properties related to sensing and therapy applications of g-C 3 N 4 materials are reviewed. Furthermore, the fabrication and advantages of sensing, imaging and therapy systems based on g-C 3 N 4 materials are summarized. Finally, the future perspectives for developing the sensing, imaging and therapy applications of the g-C 3 N 4 materials are discussed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Separation of gallium and actinides in plutonium nuclear materials by extraction chromatography

    International Nuclear Information System (INIS)

    Eitrheim, E.S.; Knight, A.W.

    2015-01-01

    Analysis of stable gallium in nuclear materials has applications in nuclear fuel characterization and nuclear forensics. The use of positron-emitting gallium isotope 68 Ga as a tracer for Ga recoveries for analyses in materials containing actinides was explored. A radiochemical method for the separation of Ga, Pu, U, Th, and Am using commercially-available extraction chromatography resins was developed and evaluated. The method effectively allows precise determination of Ga yield (97 ± 3 %) in the analysis of stable Ga (spike recovery 101 ± 1 %) and radioactive Pu (radiochemical yield, 82 ± 10 %; spike recovery, 96 ± 3 %), while also providing pure elemental fractions of other actinides relevant to materials encountered in the analysis Pu-containing materials. (author)

  8. The comparison between gallium arsenide and indium gallium arsenide as materials for solar cell performance using Silvaco application

    International Nuclear Information System (INIS)

    Zahari, Suhaila Mohd; Norizan, Mohd Natashah; Mohamad, Ili Salwani; Osman, Rozana Aina Maulat; Taking, Sanna

    2015-01-01

    The work presented in this paper is about the development of single and multilayer solar cells using GaAs and InGaAs in AM1.5 condition. The study includes the modeling structure and simulation of the device using Silvaco applications. The performance in term of efficiency of Indium Gallium Arsenide (InGaAs) and GaAs material was studied by modification of the doping concentration and thickness of material in solar cells. The efficiency of the GaAs solar cell was higher than InGaAs solar cell for single layer solar cell. Single layer GaAs achieved an efficiency about 25% compared to InGaAs which is only 2.65% of efficiency. For multilayer which includes both GaAs and InGaAs, the output power, P max was 8.91nW/cm² with the efficiency only 8.51%. GaAs is one of the best materials to be used in solar cell as a based compared to InGaAs

  9. The comparison between gallium arsenide and indium gallium arsenide as materials for solar cell performance using Silvaco application

    Energy Technology Data Exchange (ETDEWEB)

    Zahari, Suhaila Mohd; Norizan, Mohd Natashah; Mohamad, Ili Salwani; Osman, Rozana Aina Maulat; Taking, Sanna [School of Microelectronic Engineering, Universiti Malaysia Perlis, Kampus Pauh Putra, 02600 Arau, Perlis (Malaysia)

    2015-05-15

    The work presented in this paper is about the development of single and multilayer solar cells using GaAs and InGaAs in AM1.5 condition. The study includes the modeling structure and simulation of the device using Silvaco applications. The performance in term of efficiency of Indium Gallium Arsenide (InGaAs) and GaAs material was studied by modification of the doping concentration and thickness of material in solar cells. The efficiency of the GaAs solar cell was higher than InGaAs solar cell for single layer solar cell. Single layer GaAs achieved an efficiency about 25% compared to InGaAs which is only 2.65% of efficiency. For multilayer which includes both GaAs and InGaAs, the output power, P{sub max} was 8.91nW/cm² with the efficiency only 8.51%. GaAs is one of the best materials to be used in solar cell as a based compared to InGaAs.

  10. The comparison between gallium arsenide and indium gallium arsenide as materials for solar cell performance using Silvaco application

    Science.gov (United States)

    Zahari, Suhaila Mohd; Norizan, Mohd Natashah; Mohamad, Ili Salwani; Osman, Rozana Aina Maulat; Taking, Sanna

    2015-05-01

    The work presented in this paper is about the development of single and multilayer solar cells using GaAs and InGaAs in AM1.5 condition. The study includes the modeling structure and simulation of the device using Silvaco applications. The performance in term of efficiency of Indium Gallium Arsenide (InGaAs) and GaAs material was studied by modification of the doping concentration and thickness of material in solar cells. The efficiency of the GaAs solar cell was higher than InGaAs solar cell for single layer solar cell. Single layer GaAs achieved an efficiency about 25% compared to InGaAs which is only 2.65% of efficiency. For multilayer which includes both GaAs and InGaAs, the output power, Pmax was 8.91nW/cm² with the efficiency only 8.51%. GaAs is one of the best materials to be used in solar cell as a based compared to InGaAs.

  11. Titanium Nitride and Nitrogen Ion Implanted Coated Dental Materials

    Directory of Open Access Journals (Sweden)

    David W. Berzins

    2012-07-01

    Full Text Available Titanium nitride and/or nitrogen ion implanted coated dental materials have been investigated since the mid-1980s and considered in various applications in dentistry such as implants, abutments, orthodontic wires, endodontic files, periodontal/oral hygiene instruments, and casting alloys for fixed restorations. Multiple methodologies have been employed to create the coatings, but detailed structural analysis of the coatings is generally lacking in the dental literature. Depending on application, the purpose of the coating is to provide increased surface hardness, abrasion/wear resistance, esthetics, and corrosion resistance, lower friction, as well as greater beneficial interaction with adjacent biological and material substrates. While many studies have reported on the achievement of these properties, a consensus is not always clear. Additionally, few studies have been conducted to assess the efficacy of the coatings in a clinical setting. Overall, titanium nitride and/or nitrogen ion implanted coated dental materials potentially offer advantages over uncoated counterparts, but more investigation is needed to document the structure of the coatings and their clinical effectiveness.

  12. Solvothermal synthesis: a new route for preparing nitrides

    CERN Document Server

    Demazeau, G; Denis, A; Largeteau, A

    2002-01-01

    Solvothermal synthesis appears to be an interesting route for preparing nitrides such as gallium nitride and aluminium nitride, using ammonia as solvent. A nitriding additive is used to perform the reaction and, in the case of gallium nitride, is encapsulated by melt gallium. The syntheses are performed in the temperature range 400-800 deg. C and in the pressure range 100-200 MPa. The synthesized powders are characterized by x-ray diffraction and scanning electron microscopy. Finely divided gallium nitride GaN and aluminium nitride AlN, both with wurtzite-type structure, can be obtained by this route.

  13. Titanium nitride as a plasmonic material for visible and near-infrared wavelengths

    DEFF Research Database (Denmark)

    Naik, Gururaj V.; Schroeder, Jeremy L.; Ni, Xingjie

    2012-01-01

    that titanium nitride could perform as an alternative plasmonic material in the visible and near-infrared regions. We demonstrate the excitation of surface-plasmon-polaritons on titanium nitride thin films and discuss the performance of various plasmonic and metamaterial structures with titanium nitride...... as the plasmonic component. We also show that titanium nitride could provide performance that is comparable to that of gold for plasmonic applications and can significantly outperform gold and silver for transformation-optics and some metamaterial applications in the visible and near-infrared regions....

  14. Combined angle-resolved X-ray photoelectron spectroscopy, density functional theory and kinetic study of nitridation of gallium arsenide

    Science.gov (United States)

    Mehdi, H.; Monier, G.; Hoggan, P. E.; Bideux, L.; Robert-Goumet, C.; Dubrovskii, V. G.

    2018-01-01

    The high density of interface and surface states that cause the strong Fermi pinning observed on GaAs surfaces can be reduced by depositing GaN ultra-thin films on GaAs. To further improve this passivation, it is necessary to investigate the nitridation phenomena by identifying the distinct steps occurring during the process and to understand and quantify the growth kinetics of GaAs nitridation under different conditions. Nitridation of the cleaned GaAs substrate was performed using N2 plasma source. Two approaches have been combined. Firstly, an AR-XPS (Angle Resolved X-ray Photoelectron Spectroscopy) study is carried out to determine the chemical environments of the Ga, As and N atoms and the composition depth profile of the GaN thin film which allow us to summarize the nitridation process in three steps. Moreover, the temperature and time treatment have been investigated and show a significant impact on the formation of the GaN layer. The second approach is a refined growth kinetic model which better describes the GaN growth as a function of the nitridation time. This model clarifies the exchange mechanism of arsenic with nitrogen atoms at the GaN/GaAs interface and the phenomenon of quasi-saturation of the process observed experimentally.

  15. Nitride-Based Materials for Flexible MEMS Tactile and Flow Sensors in Robotics.

    Science.gov (United States)

    Abels, Claudio; Mastronardi, Vincenzo Mariano; Guido, Francesco; Dattoma, Tommaso; Qualtieri, Antonio; Megill, William M; De Vittorio, Massimo; Rizzi, Francesco

    2017-05-10

    The response to different force load ranges and actuation at low energies is of considerable interest for applications of compliant and flexible devices undergoing large deformations. We present a review of technological platforms based on nitride materials (aluminum nitride and silicon nitride) for the microfabrication of a class of flexible micro-electro-mechanical systems. The approach exploits the material stress differences among the constituent layers of nitride-based (AlN/Mo, Si x N y /Si and AlN/polyimide) mechanical elements in order to create microstructures, such as upwardly-bent cantilever beams and bowed circular membranes. Piezoresistive properties of nichrome strain gauges and direct piezoelectric properties of aluminum nitride can be exploited for mechanical strain/stress detection. Applications in flow and tactile sensing for robotics are described.

  16. Nitride-Based Materials for Flexible MEMS Tactile and Flow Sensors in Robotics

    Science.gov (United States)

    Abels, Claudio; Mastronardi, Vincenzo Mariano; Guido, Francesco; Dattoma, Tommaso; Qualtieri, Antonio; Megill, William M.; De Vittorio, Massimo; Rizzi, Francesco

    2017-01-01

    The response to different force load ranges and actuation at low energies is of considerable interest for applications of compliant and flexible devices undergoing large deformations. We present a review of technological platforms based on nitride materials (aluminum nitride and silicon nitride) for the microfabrication of a class of flexible micro-electro-mechanical systems. The approach exploits the material stress differences among the constituent layers of nitride-based (AlN/Mo, SixNy/Si and AlN/polyimide) mechanical elements in order to create microstructures, such as upwardly-bent cantilever beams and bowed circular membranes. Piezoresistive properties of nichrome strain gauges and direct piezoelectric properties of aluminum nitride can be exploited for mechanical strain/stress detection. Applications in flow and tactile sensing for robotics are described. PMID:28489040

  17. Deposition of metallic gallium on re-crystallized ceramic material during focused ion beam milling

    Energy Technology Data Exchange (ETDEWEB)

    Muñoz-Tabares, J.A., E-mail: j.a.munoz.tabares@gmail.com [Instituto de Física, Universidad Nacional Autónoma de México, Circuito de la Investigación Científica s/n, Cd Universitaria, 04510 México DF, México (Mexico); Anglada, M. [Departament de Ciència dels Materials i Enginyeria Metallúrgica, Universitat Politècnica de Catalunya, Avda. Diagonal 647 (ETSEIB), 08028 Barcelona (Spain); Reyes-Gasga, J. [Instituto de Física, Universidad Nacional Autónoma de México, Circuito de la Investigación Científica s/n, Cd Universitaria, 04510 México DF, México (Mexico)

    2013-12-15

    We report a new kind of artifact observed in the preparation of a TEM sample of zirconia by FIB, which consists in the deposition of metallic gallium nano-dots on the TEM sample surface. High resolution TEM images showed a microstructure of fine equiaxed grains of ∼ 5 nm, with some of them possessing two particular characteristics: high contrast and well-defined fast Fourier transform. These grains could not be identified as any phase of zirconia but it was possible to identify them as gallium crystals in the zone axis [110]. Based on HRTEM simulations, the possible orientations between zirconia substrate and deposited gallium are discussed in terms of lattice mismatch and oxygen affinity. - Highlights: • We show a new type of artifact induced during preparation of TEM samples by FIB. • Deposition of Ga occurs due to its high affinity for oxygen. • Materials with small grain size (∼ 5 nm) could promote Ga deposition. • Small grain size permits the elastic accommodation of deposited Ga.

  18. Effect of nitrogen doping on the structural, optical and electrical properties of indium tin oxide films prepared by magnetron sputtering for gallium nitride light emitting diodes

    Science.gov (United States)

    Tian, Lifei; Cheng, Guoan; Wang, Hougong; Wu, Yulong; Zheng, Ruiting; Ding, Peijun

    2017-01-01

    The indium tin oxide (ITO) films are prepared by the direct current magnetron sputtering technology with an ITO target in a mixture of argon and nitrogen gas at room temperature. The blue transmittance at 455 nm rises from 63% to 83% after nitrogen doping. The resistivity of the ITO film reduces from 4.6 × 10-3 (undoped film) to 5.7 × 10-4 Ω cm (N-doped film). The X-ray photoelectron spectroscopy data imply that the binding energy of the In3d5/2 peak is declined 0.05 eV after nitrogen doping. The high resolution transmission electron microscope images show that the nitrogen loss density of the GaN/ITO interface with N-doped ITO film is smaller than that of the GaN/ITO interface with undoped ITO film. The forward turn-on voltage of gallium nitride light emitting diode reduces by 0.5 V after nitrogen doping. The fabrication of the N-doped ITO film is conducive to modify the N component of the interface between GaN and ITO layer.

  19. Pure silver ohmic contacts to N- and P- type gallium arsenide materials

    Science.gov (United States)

    Hogan, Stephen J.

    1986-01-01

    Disclosed is an improved process for manufacturing gallium arsenide semiconductor devices having as its components an n-type gallium arsenide substrate layer and a p-type gallium arsenide diffused layer. The improved process comprises forming a pure silver ohmic contact to both the diffused layer and the substrate layer, wherein the n-type layer comprises a substantially low doping carrier concentration.

  20. Characterization and electrochemical activities of nanostructured transition metal nitrides as cathode materials for lithium sulfur batteries

    Science.gov (United States)

    Mosavati, Negar; Salley, Steven O.; Ng, K. Y. Simon

    2017-02-01

    The Lithium Sulfur (Li-S) battery system is one of the most promising candidates for electric vehicle applications due to its higher energy density when compared to conventional lithium ion batteries. However, there are some challenges facing Li-S battery commercialization, such as: low active material utilization, high self-discharge rate, and high rate of capacity fade. In this work, a series of transition metal nitrides: Tungsten nitride (WN), Molybdenum Nitride (Mo2N), and Vanadium Nitride (VN) was investigated as cathode materials for lithium polysulfide conversion reactions. Capacities of 697, 569, and 264 mAh g-1 were observed for WN, Mo2N, VN, respectively, with 8 mg cm-2 loading, after 100 cycles at a 0.1 C rate. WN higher electrochemical performance may be attributed to a strong reversible reaction between nitrides and polysulfide, which retains the sulfur species on the electrode surface, and minimizes the active material and surface area loss. X-ray photoelectron spectroscopy (XPS) analysis was performed to gain a better understanding of the mechanism underlying each metal nitride redox reactions.

  1. The Role of Defect Complexes in the Magneto-Optical Properties of Rare Earth Doped Gallium Nitride

    Science.gov (United States)

    Mitchell, Brandon

    Wide band gap semiconductors doped with rare earth ions (RE) have shown great potential for applications in optoelectronics, photonics, and spintronics. The 1.54mum Erbium (Er) emission has been extensively utilized in optical fiber communications, and Europium (Eu) is commonly used as a red color component for LEDs and fluorescence lamps. For the realization of spintronic-type devices, a dilutely doped semiconductor that exhibits room temperature ferromagnetic behavior would be desirable. Such behavior has been observed in GaN:Er. Furthermore, it was demonstrated that strain may play an important role in the control of this ferromagnetism; however, this requires further investigation. One motivation of this work is the realization of an all solid state white light source monolithically integrated into III/V nitride semiconductor materials, ideally GaN. For this, the current AlGaAs-based LEDs need to be replaced. One approach for achieving efficient red emission from GaN is dilute doping with fluorescent ions. In this regard, Eu has consistently been the most promising candidate as a dopant in the active layer for a red, GaN based, LED due to the sharp 5D0 to 7F2 transitions that result in red emission around 620nm. The success of GaN:Eu as the active layer for a red LED is based on the ability for the Eu ions to be efficiently excited by electron hole pairs. Thus, the processes by which energy is transferred from the host to the Eu ions has been studied. Complications arise, however, from the fact that Eu ions incorporate into multiple center environments, the structures of which are found to have a profound influence on the excitation pathways and efficiencies of the Eu ion. Therefore the nature of Eu incorporation and the resulting luminescence efficiency in GaN has been extensively investigated. By performing a comparative study on GaN:Eu samples grown under a variety of controlled conditions and using a variety of experimental techniques, the majority site has

  2. Solid State Synthesis and Characterization of Carbo-Nitride Materials

    National Research Council Canada - National Science Library

    Khabashesku, Valery

    2000-01-01

    The preparation of stoichiometric sp(sup 2)-bonded amorphous carbon nitride a-C3N4 in gram quantities was successfully achieved by performing a solid-state reaction of cyanuric halides C3N3X3 (X=Cl, F...

  3. Gallium oxide nanorods as novel, safe and durable anode material for Li- and Na-ion batteries

    NARCIS (Netherlands)

    Meligrana, Giuseppina; Lueangchaichaweng, Warunee; Colo, Francesca; Destro, Matteo; Fiorilli, Sonia; Pescarmona, Paolo P.; Gerbaldi, Claudio

    2017-01-01

    Gallium oxide nanorods prepared by template-free synthesis are reported for the first time as safe and durable anode material for lithium- and sodium-ion batteries. The ambient temperature electrochemical response of the nanorods, tested by cyclic voltammetry and constant-current reversible cycling,

  4. Nanopipe formation as a result of boron impurity segregation in gallium nitride grown by halogen-free vapor phase epitaxy

    Science.gov (United States)

    Kimura, Taishi; Aoki, Yuko; Horibuchi, Kayo; Nakamura, Daisuke

    2016-12-01

    The work reported herein demonstrated that nanopipes can be formed via a surfactant effect, in which boron impurities preferentially migrate to semipolar and nonpolar facets. Approximately 3 μm-thick GaN layers were grown using halogen-free vapor phase epitaxy. All layers grown in pyrolytic boron nitride (pBN) crucibles were found to contain a high density of nanopipes in the range of 1010 to 1011 cm-2. The structural properties of these nanopipes were analyzed by X-ray rocking curve measurements, transmission electron microscopy, and three-dimensional atom probe (3DAP) tomography. The resulting 3DAP maps showed nanopipe-sized regions of boron segregation, and these nanopipes were not associated with the presence of dislocations. A mechanism for nanopipe formation was developed based on the role of boron as a surfactant and considering energy minima. A drastic reduction in the nanopipe density was achieved upon replacing the pBN crucibles with tantalum carbide-coated carbon crucibles. Consequently, we have confirmed that nanopipes can be formed solely due to surface energy changes induced by boron impurity surface segregation. For this reason, these results also indicate that nanopipes should be formed by other surfactant impurities such as Mg and Si.

  5. Conductivity of materials made of aluminum nitride and silicon nitride mixtures

    Science.gov (United States)

    Gorbatov, A. G.; Kamyshov, V. M.

    1978-01-01

    To establish the possible mechanism for conductivity in aluminum nitride a study was made of the electric conductivity of pure AlN and its mixtures with silicon nitride at different temperatures and partial pressures of nitrogen in the gas phase. The thermoelectromotive force was also measured. The experiments used polycrystalline samples of cylindrical shape 18 mm in diameter made of powders by hot pressing in graphite press molds at a temperature of 1973-2273 K and pressure 1,470,000 n/sqm. The items obtained by this method had porosity not over 5%. After pressing, the samples were machined to remove carbon from the surface, and were annealed in a stream of dry ammonia for 10 h at a temperature of 1273-1373 K. Electric conductivity was measured according to the bridge scheme on an alternating current of frequency 10 kHz. In order to guarantee close contact of the platinum electrodes with the surface of the samples, a thin layer of platinum was sprayed on them. Experiments were conducted in the temperature interval 1273-1573 K with a half hour delay at each assigned temperature with heating and cooling.

  6. Structural materialization of stainless steel molds and dies by the low temperature high density plasma nitriding

    Directory of Open Access Journals (Sweden)

    Aizawa Tatsuhiko

    2015-01-01

    Full Text Available Various kinds of stainless steels have been widely utilized as a mold substrate material for injection molding and as a die for mold-stamping and direct stamping processes. Since they suffered from high temperature transients and thermal cycles in practice, they must be surface-treated by dry and wet coatings, or, by plasma nitriding. Martensitic stainless steel mold was first wet plated by the nickel phosphate (NiP, which was unstable at the high temperature stamping condition; and, was easy to crystalize or to fracture by itself. This issue of nuisance significantly lowered the productivity in fabrication of optical elements at present. In the present paper, the stainless steel mold was surface-treated by the low-temperature plasma nitriding. The nitrided layer by this surface modification had higher nitrogen solute content than 4 mass%; the maximum solid-solubility of nitrogen is usually 0.1 mass% in the equilibrium phase diagram. Owing to this solid-solution with high nitrogen concentration, the nitrided layer had high hardness of 1400 Hv within its thickness of 40 μm without any formation of nitrides after 14.4 ks plasma nitriding at 693 K. This nitrogen solid-solution treated stainless steel had thermal resistivity even at the mold-stamping conditions up to 900 K.

  7. A comparative study of the thermal interface materials with graphene and boron nitride fillers

    Science.gov (United States)

    Kargar, F.; Salgado, R.; Legedza, S.; Renteria, J.; Balandin, A. A.

    2014-09-01

    We report the results of an experimental study that compares the performance of graphene and boron nitride flakes as fillers in the thermal interface materials. The thickness of both fillers varied from a single atomic plane to about a hundred. The measurements have been conducted using a standard TIM tester. Our results show that the addition of a small fraction of graphene (f=4 wt%) to a commercial thermal interface material increases the resulting apparent thermal conductivity substantially stronger than the addition of boron nitride. The obtained data suggest that graphene and fewlayer graphene flakes couple better to the matrix materials than the boron nitride fillers. A combination of both fillers can be used to increase the thermal conductivity while controlling the electrical conduction.

  8. Performance analysis of nitride alternative plasmonic materials for localized surface plasmon applications

    DEFF Research Database (Denmark)

    Guler, U.; Naik, G. V.; Boltasseva, Alexandra

    2012-01-01

    efficiency, which is a generalized form of the well-known scattering efficiency, is a more flexible and useful metric for local-field enhancement applications. We also examine the evolution of the field enhancement from a particle surface to the far-field regime for spherical nanoparticles with varying radii......We consider methods to define the performance metrics for different plasmonic materials to be used in localized surface plasmon applications. Optical efficiencies are shown to be better indicators of performance as compared to approximations in the quasistatic regime. The near-field intensity....... Titanium nitride and zirconium nitride, which were recently suggested as alternative plasmonic materials in the visible and near-infrared ranges, are compared to the performance of gold. In contrast to the results from quasistatic methods, both nitride materials are very good alternatives to the usual...

  9. Polar and Nonpolar Gallium Nitride and Zinc Oxide based thin film heterostructures Integrated with Sapphire and Silicon

    Science.gov (United States)

    Gupta, Pranav

    This dissertation work explores the understanding of the relaxation and integration of polar and non-polar of GaN and ZnO thin films with Sapphire and silicon substrates. Strain management and epitaxial analysis has been performed on wurtzitic GaN(0001) thin films grown on c-Sapphire and wurtzitic non-polar a-plane GaN(11-20) thin films grown on r-plane Sapphire (10-12) by remote plasma atomic nitrogen source assisted UHV Pulsed Laser Deposition process. It has been established that high-quality 2-dimensional c-axis GaN(0001) nucleation layers can be grown on c-Sapphire by PLD process at growth temperatures as low as ˜650°C. Whereas the c-axis GaN on c-sapphire has biaxially negative misfit, the crystalline anisotropy of the a-plane GaN films on r-Sapphire results in compressive and tensile misfits in the two major orthogonal directions. The measured strains have been analyzed in detail by X-ray, Raman spectroscopy and TEM. Strain relaxation in GaN(0001)/Sapphire thin film heterostructure has been explained by the principle of domain matched epitaxial growth in large planar misfit system and has been demonstrated by TEM study. An attempt has been made to qualitatively understand the minimization of free energy of the system from the strain perspective. Analysis has been presented to quantify the strain components responsible for the compressive strain observed in the GaN(0001) thin films on c-axis Sapphire substrates. It was also observed that gallium rich deposition conditions in PLD process lead to smoother nucleation layers because of higher ad-atom mobility of gallium. We demonstrate near strain relaxed epitaxial (0001) GaN thin films grown on (111) Si substrates using TiN as intermediate buffer layer by remote nitrogen plasma assisted UHV pulsed laser deposition (PLD). Because of large misfits between the TiN/GaN and TiN/Si systems the TIN buffer layer growth occurs via nucleation of interfacial dislocations under domain matching epitaxy paradigm. X-ray and

  10. Boron nitride composites

    Science.gov (United States)

    Kuntz, Joshua D.; Ellsworth, German F.; Swenson, Fritz J.; Allen, Patrick G.

    2017-02-21

    According to one embodiment, a composite product includes: a matrix material including hexagonal boron nitride and one or more borate binders; and a plurality of cubic boron nitride particles dispersed in the matrix material. According to another embodiment, a composite product includes: a matrix material including hexagonal boron nitride and amorphous boron nitride; and a plurality of cubic boron nitride particles dispersed in the matrix material.

  11. Reassembling Solid Materials by Femtosecond Laser Ablation: Case of Aluminum Nitride

    Science.gov (United States)

    Kobayashi, Tohru; Matsuo, Yukari

    2013-06-01

    Through atomization and ionization, we could completely alter the composition of a nonconductive material, aluminum nitride, by femtosecond laser ablation. Preferential production of pure aluminum cluster cations Aln+ (n≤32) reflects not only their higher energetic stability compared with mixed clusters AlnNm+ but also completion of thermal relaxation in ablation plasma. Observation of metastable dissociation of Aln+ indicates that cluster cations have still enough internal energy for dissociation to occur, although the process is much slower than the cluster formation. Almost no cluster formation has been observed after nanosecond laser ablation of aluminum nitride, which highlights the distinct nature of ablation plasma produced by femtosecond laser ablation.

  12. Evaluation of critical materials for five advanced design photovoltaic cells with an assessment of indium and gallium

    Energy Technology Data Exchange (ETDEWEB)

    Watts, R.L.; Gurwell, W.E.; Jamieson, W.M.; Long, L.W.; Pawlewicz, W.T.; Smith, S.A.; Teeter, R.R.

    1980-05-01

    The objective of this study is to identify potential material supply constraints due to the large-scale deployment of five advanced photovoltaic (PV) cell designs, and to suggest strategies to reduce the impacts of these production capacity limitations and potential future material shortages. This report presents the results of the screening of the five following advanced PV cell designs: polycrystalline silicon, amorphous silicon, cadmium sulfide/copper sulfide frontwall, polycrystalline gallium arsenide MIS, and advanced concentrator-500X. Each of these five cells is screened individually assuming that they first come online in 1991, and that 25 GWe of peak capacity is online by the year 2000. A second computer screening assumes that each cell first comes online in 1991 and that each cell has 5 GWe of peak capacity by the year 2000, so that the total online cpacity for the five cells is 25 GWe. Based on a review of the preliminary basline screening results, suggestions were made for varying such parameters as the layer thickness, cell production processes, etc. The resulting PV cell characterizations were then screened again by the CMAP computer code. Earlier DOE sponsored work on the assessment of critical materials in PV cells conclusively identtified indium and gallium as warranting further investigation as to their availability. Therefore, this report includes a discussion of the future availability of gallium and indium. (WHK)

  13. Investigation of an Electrochemical Method for Separation of Copper, Indium, and Gallium from Pretreated CIGS Solar Cell Waste Materials

    Directory of Open Access Journals (Sweden)

    Anna M. K. Gustafsson

    2015-01-01

    Full Text Available Recycling of the semiconductor material copper indium gallium diselenide (CIGS is important to ensure a future supply of indium and gallium, which are relatively rare and therefore expensive elements. As a continuation of our previous work, where we recycled high purity selenium from CIGS waste materials, we now show that copper and indium can be recycled by electrodeposition from hydrochloric acid solutions of dissolved selenium-depleted material. Suitable potentials for the reduction of copper and indium were determined to be −0.5 V and −0.9 V (versus the Ag/AgCl reference electrode, respectively, using cyclic voltammetry. Electrodeposition of first copper and then indium from a solution containing the dissolved residue from the selenium separation and ammonium chloride in 1 M HCl gave a copper yield of 100.1 ± 0.5% and an indium yield of 98.1 ± 2.5%. The separated copper and indium fractions contained no significant contamination of the other elements. Gallium remained in solution together with a small amount of indium after the separation of copper and indium and has to be recovered by an alternative method since electrowinning from the chloride-rich acid solution was not effective.

  14. Self-healing in carbon nitride evidenced as material inflation and superlubric behavior.

    Science.gov (United States)

    Bakoglidis, Konstantinos D; Palisaitis, Justinas; Dos Santos, Renato Batista; Rivelino, Roberto; Persson, Per O Å; Gueorguiev, Gueorgui K; Hultman, Lars

    2018-05-01

    All known materials wear under extended mechanical contacting. Superlubricity may present solutions, but is an expressed mystery in C-based materials. We report negative wear of carbon nitride films; a wear-less condition with mechanically-induced material inflation at the nanoscale and friction coefficient approaching ultralow values (0.06). Superlubricity in carbon nitride is expressed as C-N bond breaking for reduced coupling between graphitic-like sheets and eventual N 2 desorption. The transforming surface layer acts as a solid lubricant, while the film bulk retains its high elasticity. The present findings offer new means for materials design at the atomic level, and for property optimization in wear-critical applications like magnetic reading devices or nanomachines.

  15. Silicon nitride: A ceramic material with outstanding resistance to thermal shock and corrosion

    Science.gov (United States)

    Huebner, K. H.; Saure, F.

    1983-01-01

    The known physical, mechanical and chemical properties of reaction-sintered silicon nitride are summarized. This material deserves interest especially because of its unusually good resistance to thermal shock and corrosion at high temperatures. Two types are distinguished: reaction-sintered (porous) and hot-pressed (dense) Si3N4. Only the reaction-sintered material which is being produced today in large scale as crucibles, pipes, nozzles and tiles is considered.

  16. UV-Assisted Alcohol Sensors using Gallium Nitride Nanowires Functionalized with Zinc Oxide and Tin Dioxide Nanoparticles

    Science.gov (United States)

    Bajpai, Ritu

    The motivation behind this work has been to address two of the most challenging issues posed to semiconductor gas sensors--- tuning the device selectivity and sensitivity to a wide variety of gases. In a chemiresistor type nanowire sensor, the sensitivity and selectivity depend on the interaction of different chemical analytes with the nanowire surface. Constrained by the surface properties of the nanowire material, most nanowire sensors can detect only specific type of analytes. In order to make a nano-sensor array for a wide range of analytes, there is a need to tune the device sensitivity and selectivity towards different chemicals. Employing the inherent advantages of nanostructure based sensing such as large surface area, miniature size, low power consumption, and nmol/mol (ppb) sensitivity, an attempt has been made to propose a device with tunable selectivity and sensitivity. The idea proposed in this work is to functionalize GaN nanowires which have relatively inactive surface properties (i.e., with no chemiresistive sensitivity to different classes of organic vapors), with analyte dependent active metal oxides. The selectivity of the sensor devices is controlled independent of the surface properties of the nanowire itself. It is the surface properties of the functionalizing metal oxides which determine the selectivity of these sensors. Further facilitated by the proposed fabrication technique, these sensors can be easily tuned to detect different gases. The prototype developed in this work is that of a UV assisted alcohol sensor using GaN nanowires functionalized with ZnO and SnO2 nanoparticles. As opposed to the widely demonstrated metal oxide based sensors assisted by elevated temperature, the operation of photoconductive semiconductor sensor devices such as those fabricated in this work, can also be assisted by UV illumination at room temperature. Temperature assisted sensing requires an integrated on-chip heater, which could impose constraints on the

  17. Piezoelectric characterization and thermal stability of a high-performance α-quartz-type material, gallium arsenate

    International Nuclear Information System (INIS)

    Cambon, Olivier; Haines, Julien; Fraysse, Guillaume; Detaint, Jacques; Capelle, Bernard; Lee, Arie van der

    2005-01-01

    Piezoelectric measurements were performed on large single crystals (8 mm along the c direction) of an α-quartz-type piezoelectric material, gallium arsenate, GaAsO 4 , which allow us to extend the structure-property relationships in the α-quartz-type materials. These first measurements on Y-rotated-cut plates have shown that gallium arsenate is the highest-performance piezoelectric material of this group. As compared to the coupling coefficients of the other materials with the same structure (k SiO 2 =8%, k AlPO 4 =11%, and k GaPO 4 =16%), gallium arsenate exhibits the highest piezoelectric coupling coefficient of about 22%, as has been predicted by the structure-property relationships. Moreover, from these piezoelectric measurements, the C 66 ' elastic constant was determined and compared with elastic constants in quartz-type materials. The proposed value for the cut angle of the AT plane in GaAsO 4 is -6.3 deg. . In order to extend the previous thermal stability results, thermal gravimetric analysis (TGA) and x-ray diffraction have been carried out on GaAsO 4 powder at high temperatures. It has been shown that GaAsO 4 is stable up to 1030 deg. C. The thermal-expansion coefficient of GaAsO 4 is 4.0x10 -5 K -1 . The thermal expansion of the predicted AT plane (Y-6.3 deg. ) in GaAsO 4 is shown to be similar to that of the other materials. Finally, it is demonstrated that the intertetrahedral bridging angle θ (A-O-B) of GaAsO 4 is the most stable in α-quartz materials, which enables one to predict that GaAsO 4 should retain high piezoelectric performances up to 925 deg. C

  18. Optical Properties of GaN and Other III-Nitride Semiconductor Materials Studied by Variable Angle Spectroscopic Ellipsometry

    National Research Council Canada - National Science Library

    Yao, Huade

    2000-01-01

    .... It is for the first time, the ordinary and extraordinary optical constants of the important III-Nitride materials, GaN, AlN and sapphire, have been determined by variable angle spectroscopic ellipsometry (VASE...

  19. Optical and Electrical Properties of III-Nitrides and Related Materials

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Hongxing [Texas Tech Univ., Lubbock, TX (United States); Lin, Jingyu [Texas Tech Univ., Lubbock, TX (United States)

    2016-01-22

    Among the members of the III-nitride material system, boron-nitride (BN) is the least studied and understood. Its extraordinary physical properties, such as ultra-high chemical stability, thermal conductivity, electrical resistivity, band gap (Eg ~ 6 eV), and optical absorption near the band gap make hexagonal BN (h-BN) the material of choice for emerging applications such as deep ultraviolet (DUV) optoelectronic devices. Moreover, h-BN has a close lattice match to graphene and is the most suitable substrate and dielectric/separation layer for graphene electronics and optoelectronics. Similar to graphene, low dimensional h-BN is expected to possess rich new physics. Other potential applications include super-capacitors and electron emitters. However, our knowledge concerning the semiconducting properties of h-BN is very scarce. The project aims to extend our studies to the “newest” family member of the III-nitride material system, h-BN, and to address issues that have not yet been explored but are expected to profoundly influence our understanding on its fundamental properties and device applications. During the supporting period, we have improved the growth processes of h-BN epilayers by metal organic chemical vapor deposition (MOCVD), investigated the fundamental material properties, and identified several unique features of h-BN as well as critical issues that remain to be addressed.

  20. Progress in III–nitrides: Process issue and purity perspective

    Indian Academy of Sciences (India)

    Unknown

    and economic parameters. The major objective of the investigation is to develop gallium nitride (GaN) device quality layers and evaluate their characteristics. We have designed and fabricated the vapour phase epitaxy system (VPE) for the growth of gallium nitride (GaN). GaN samples with different transition metal dopants ...

  1. High Kinetic Energy Penetrator Shielding and High Wear Resistance Materials Fabricated with Boron Nitride Nanotubes (BNNTS) and BNNT Polymer Composites

    Science.gov (United States)

    Kang, Jin Ho (Inventor); Park, Cheol (Inventor); Sauti, Godfrey (Inventor); Smith, Michael W. (Inventor); Jordan, Kevin C. (Inventor); Lowther, Sharon E. (Inventor); Bryant, Robert George (Inventor)

    2015-01-01

    Boron nitride nanotubes (BNNTs), boron nitride nanoparticles (BNNPs), carbon nanotubes (CNTs), graphites, or combinations, are incorporated into matrices of polymer, ceramic or metals. Fibers, yarns, and woven or nonwoven mats of BNNTs are used as toughening layers in penetration resistant materials to maximize energy absorption and/or high hardness layers to rebound or deform penetrators. They can be also used as reinforcing inclusions combining with other polymer matrices to create composite layers like typical reinforcing fibers such as Kevlar.RTM., Spectra.RTM., ceramics and metals. Enhanced wear resistance and usage time are achieved by adding boron nitride nanomaterials, increasing hardness and toughness. Such materials can be used in high temperature environments since the oxidation temperature of BNNTs exceeds 800.degree. C. in air. Boron nitride based composites are useful as strong structural materials for anti-micrometeorite layers for spacecraft and space suits, ultra strong tethers, protective gear, vehicles, helmets, shields and safety suits/helmets for industry.

  2. Nanocomposite Diamond and Nitride Films on Structural Materials

    National Research Council Canada - National Science Library

    White, Henry

    2001-01-01

    ...) An electron cyclotron resonance microwave plasma enhanced chemical vapor deposition system was designed and used to grow diamond and diamond-like films on structural materials such as Fe-based alloys (316 stainless steel...

  3. Synthesis of ternary metal nitride nanoparticles using mesoporous carbon nitride as reactive template.

    Science.gov (United States)

    Fischer, Anna; Müller, Jens Oliver; Antonietti, Markus; Thomas, Arne

    2008-12-23

    Mesoporous graphitic carbon nitride was used as both a nanoreactor and a reactant for the synthesis of ternary metal nitride nanoparticles. By infiltration of a mixture of two metal precursors into mesoporous carbon nitride, the pores act first as a nanoconfinement, generating amorphous mixed oxide nanoparticles. During heating and decomposition, the carbon nitride second acts as reactant or, more precisely, as a nitrogen source, which converts the preformed mixed oxide nanoparticles into the corresponding nitride (reactive templating). Using this approach, ternary metal nitride particles with diameters smaller 10 nm composed of aluminum gallium nitride (Al-Ga-N) and titanium vanadium nitride (Ti-V-N) were synthesized. Due to the confinement effect of the carbon nitride matrix, the composition of the resulting metal nitride can be easily adjusted by changing the concentration of the preceding precursor solution. Thus, ternary metal nitride nanoparticles with continuously adjustable metal composition can be produced.

  4. Formation of Mach angle profiles during wet etching of silica and silicon nitride materials

    Energy Technology Data Exchange (ETDEWEB)

    Ghulinyan, M., E-mail: ghulinyan@fbk.eu [Centre for Materials and Microsystems, Fondazione Bruno Kessler, I-38123 Povo (Italy); Bernard, M.; Bartali, R. [Centre for Materials and Microsystems, Fondazione Bruno Kessler, I-38123 Povo (Italy); Deptartment of Physics, University of Trento, I-38123 Povo (Italy); Pucker, G. [Centre for Materials and Microsystems, Fondazione Bruno Kessler, I-38123 Povo (Italy)

    2015-12-30

    Highlights: • Photoresist adhesion induces the formation of complex etch profiles in dielectrics. • Hydrofluoric acid etching of silica glass and silicon nitride materials was studied. • The phenomenon has been modeled in analogy with sonic boom propagation. • The material etch rate and resist adhesion/erosion define the final profile. - Abstract: In integrated circuit technology peeling of masking photoresist films is a major drawback during the long-timed wet etching of materials. It causes an undesired film underetching, which is often accompanied by a formation of complex etch profiles. Here we report on a detailed study of wedge-shaped profile formation in a series of silicon oxide, silicon oxynitride and silicon nitride materials during wet etching in a buffered hydrofluoric acid (BHF) solution. The shape of etched profiles reflects the time-dependent adhesion properties of the photoresist to a particular material and can be perfectly circular, purely linear or a combination of both, separated by a knee feature. Starting from a formal analogy between the sonic boom propagation and the wet underetching process, we model the wedge formation mechanism analytically. This model predicts the final form of the profile as a function of time and fits the experimental data perfectly. We discuss how this knowledge can be extended to the design and the realization of optical components such as highly efficient etch-less vertical tapers for passive silicon photonics.

  5. Aluminum nitride as nonlinear optical material for on-chip frequency comb generation and frequency conversion

    Directory of Open Access Journals (Sweden)

    Jung Hojoong

    2016-06-01

    Full Text Available A number of dielectric materials have been employed for on-chip frequency comb generation. Silicon based dielectrics such as silicon dioxide (SiO2 and silicon nitride (SiN are particularly attractive comb materials due to their low optical loss and maturity in nanofabrication. They offer third-order Kerr nonlinearity (χ(3, but little second-order Pockels (χ(2 effect. Materials possessing both strong χ(2 and χ(3 are desired to enable selfreferenced frequency combs and active control of comb generation. In this review, we introduce another CMOS-compatible comb material, aluminum nitride (AlN,which offers both second and third order nonlinearities. A review of the advantages of AlN as linear and nonlinear optical material will be provided, and fabrication techniques of low loss AlN waveguides from the visible to infrared (IR region will be discussed.We will then show the frequency comb generation including IR, red, and green combs in high-Q AlN micro-rings from single CW IR laser input via combination of Kerr and Pockels nonlinearity. Finally, the fast speed on-off switching of frequency comb using the Pockels effect of AlN will be shown,which further enriches the applications of the frequency comb.

  6. Electronics Devices and Materials

    Science.gov (United States)

    2008-03-17

    bonding. The direct bonded wafers will include substrates of silicon, silicon geranium, silicon carbide, gallium arsenide, gallium antimonide and other Il...Acronyms AL ................... Aluminum A LN......... Aluminum Nitride A-Si .................... Silicon AU ..................... Gold CIGS

  7. Effect of Projectile Materials on Foreign Object Damage of a Gas-Turbine Grade Silicon Nitride

    Science.gov (United States)

    Choi, Sung R.; Racz, Zsolt; Bhatt, Ramakrishna T.; Brewer, David N.; Gyekenyesi, John P.

    2005-01-01

    Foreign object damage (FOD) behavior of AS800 silicon nitride was determined using four different projectile materials at ambient temperature. The target test specimens rigidly supported were impacted at their centers by spherical projectiles with a diameter of 1.59 mm. Four different types of projectiles were used including hardened steel balls, annealed steel balls, silicon nitride balls, and brass balls. Post-impact strength of each target specimen impacted was determined as a function of impact velocity to better understand the severity of local impact damage. The critical impact velocity where target specimens fail upon impact was highest with brass balls, lowest with ceramic ball, and intermediate with annealed and hardened steel balls. Degree of strength degradation upon impact followed the same order as in the critical impact velocity with respect to projectile materials. For steel balls, hardened projectiles yielded more significant impact damage than annealed counterparts. The most important material parameter affecting FOD was identified as hardness of projectiles and was correlated in terms of critical impact velocity, impact deformation, and impact load.

  8. Investigation of Emerging Materials for Optoelectronic Devices Based on III-Nitrides

    KAUST Repository

    Muhammed, Mufasila Mumthaz

    2018-03-11

    III-nitride direct bandgap semiconductors have attracted significant research interest due to their outstanding potential for modern optoelectronic and electronic applications. However, the high cost of III-nitride devices, along with low performance due to dislocation defects, remains an obstacle to their further improvement. In this dissertation, I present a significant enhancement of III-nitride devices based on emerging materials. A promising substrate, (-201)-oriented β-Ga2O3 with unique properties that combine high transparency and conductivity, is used for the first time in the development of high-quality vertical III-nitride devices, which can be cost-effective for large-scale production. In addition, hybridizing GaN with emerging materials, mainly perovskite, is shown to extend the functionality of III-nitride applications. As a part of this investigation, high-performance and high-responsivity fast perovskite/GaN-based UV-visible broadband photodetectors were developed. State-of-the-art GaN epilayers grown on (-201)-oriented β-Ga2O3 using AlN and GaN buffer layers are discussed, and their high optical quality without using growth enhancement techniques is demonstrated. In particular, a low lattice mismatch (⁓4.7%) between GaN and the substrate results in a low density of dislocations ~4.8Å~107 cm−2. To demonstrates the effect of (-201)-oriented β-Ga2O3 substrate on the quality of III-nitride alloys, high-quality ternary alloy InxGa1−xN film is studied, followed by the growth of high quality InxGa1−xN/GaN single and multiple quantum wells (QWs). The optical characterization and carrier dynamics by photoluminescence (PL) and time-resolved PL measurements were subsequently performed. Lastly, to investigate the performance of a vertical emitting device based on InGaN/GaN multiple QWs grown on (-201)-oriented β-Ga2O3 substrate, high-efficiency vertical-injection emitting device is developed and extensively investigated. The conductive nature of

  9. Synthesis of functional boron or aluminium nitride materials for energy applications (production and storage of hydrogen)

    International Nuclear Information System (INIS)

    Salameh, Chrystelle

    2014-01-01

    Porous inorganic materials are of great interest owing to their potential in energy applications. The general objective of the present thesis concerns the development of functional (carbon)nitrides for hydrogen generation and storage (material design, elaboration, properties and applications). The PDCs route, which offers a large number of opportunities in chemistry and ceramic sciences, has been applied to produce functional (carbon)nitrides materials. Firstly, we prepared porous binary systems such as AlN and BN by replicating the structure of CMK-3 and that of activated carbon. After pyrolysis and removal of the template, we demonstrated the feasibility of producing nitrides with tailored porosity. Moreover, by coupling the PDCs route with the aerogel technology, we succeeded in preparing polymer-derived AlN and BN aerogels. We assessed the potential of these porous AlN and BN materials in nano-confinement of two chemical hydrides, namely sodium alanate and ammonia borane, respectively. In both cases, the nano-confinement destabilized the network of the hydride and favored the release of H 2 at low temperature. Besides, in the case of nano-confined ammonia borane, no evolution of undesired gaseous by-products was observed, which means that pure hydrogen was produced in our conditions. Secondly, we prepared porous quaternary systems through the association of AlN/BN with Si-based ceramics. In particular, we investigated the preparation of SiAlCN with tailored porosity by using two approaches: the 'molecular building block' and 'single-source precursor' approaches. Concerning the former, we investigated the preparation of ordered meso-porous materials to be used as catalytic supports for hydrolysis of alkaline solution of sodium borohydride. We succeeded in generating high amounts of H 2 with attractive kinetics. Concerning the latter approach, the work was focused on the investigation of the chemistry of SiAlCN and SiBCN materials with a

  10. Effect of post-deposition annealing on low temperature metalorganic chemical vapor deposited gallium oxide related materials

    Science.gov (United States)

    Takiguchi, Yuki; Miyajima, Shinsuke

    2017-06-01

    Low temperature metalorganic chemical vapor deposition using trimethylgallium and water was investigated. The surface morphology of the film was almost flat at a deposition temperature below 182 °C. This flat film was a mixture of nanocrystalline and amorphous phase. The film deposited at a temperature of 272 °C resulted in a nanowire structure. X-ray diffraction measurements revealed that the nanowire film was a mixture of gallium hydroxide, gallium oxyhydroxide, and gallium tohdite or gallium oxide. We also found that post-deposition annealing above 600 °C significantly changed the crystal structure of the both flat and nanowire films. Monoclinic gallium oxide phase was dominant after the post-deposition annealing above 600 °C.

  11. Biopolymer-activated graphitic carbon nitride towards a sustainable photocathode material.

    Science.gov (United States)

    Zhang, Yuanjian; Schnepp, Zoë; Cao, Junyu; Ouyang, Shuxin; Li, Ying; Ye, Jinhua; Liu, Songqin

    2013-01-01

    Photoelectrochemical (PEC) conversion of solar light into chemical fuels is one of the most promising solutions to the challenge of sustainable energy. Graphitic carbon (IV) nitride polymer (g-CN) is an interesting sustainable photocathode material due to low-cost, visible-light sensitivity, and chemical stability up to 500 °C in air. However, grain boundary effects and limited active sites greatly hamper g-CN activity. Here, we demonstrate biopolymer-activation of g-CN through simultaneous soft-templating of a sponge-like structure and incorporation of active carbon-dopant sites. This facile approach results in an almost 300% increase in the cathodic PEC activity of g-CN under simulated solar-irradiation.

  12. Single Photon Counting UV Solar-Blind Detectors Using Silicon and III-Nitride Materials

    Science.gov (United States)

    Nikzad, Shouleh; Hoenk, Michael; Jewell, April D.; Hennessy, John J.; Carver, Alexander G.; Jones, Todd J.; Goodsall, Timothy M.; Hamden, Erika T.; Suvarna, Puneet; Bulmer, J.; Shahedipour-Sandvik, F.; Charbon, Edoardo; Padmanabhan, Preethi; Hancock, Bruce; Bell, L. Douglas

    2016-01-01

    Ultraviolet (UV) studies in astronomy, cosmology, planetary studies, biological and medical applications often require precision detection of faint objects and in many cases require photon-counting detection. We present an overview of two approaches for achieving photon counting in the UV. The first approach involves UV enhancement of photon-counting silicon detectors, including electron multiplying charge-coupled devices and avalanche photodiodes. The approach used here employs molecular beam epitaxy for delta doping and superlattice doping for surface passivation and high UV quantum efficiency. Additional UV enhancements include antireflection (AR) and solar-blind UV bandpass coatings prepared by atomic layer deposition. Quantum efficiency (QE) measurements show QE > 50% in the 100–300 nm range for detectors with simple AR coatings, and QE ≅ 80% at ~206 nm has been shown when more complex AR coatings are used. The second approach is based on avalanche photodiodes in III-nitride materials with high QE and intrinsic solar blindness. PMID:27338399

  13. Biopolymer-Activated Graphitic Carbon Nitride towards a Sustainable Photocathode Material

    Science.gov (United States)

    Zhang, Yuanjian; Schnepp, Zoë; Cao, Junyu; Ouyang, Shuxin; Li, Ying; Ye, Jinhua; Liu, Songqin

    2013-01-01

    Photoelectrochemical (PEC) conversion of solar light into chemical fuels is one of the most promising solutions to the challenge of sustainable energy. Graphitic carbon (IV) nitride polymer (g-CN) is an interesting sustainable photocathode material due to low-cost, visible-light sensitivity, and chemical stability up to 500°C in air. However, grain boundary effects and limited active sites greatly hamper g-CN activity. Here, we demonstrate biopolymer-activation of g-CN through simultaneous soft-templating of a sponge-like structure and incorporation of active carbon-dopant sites. This facile approach results in an almost 300% increase in the cathodic PEC activity of g-CN under simulated solar-irradiation. PMID:23831846

  14. Conductive Graphitic Carbon Nitride as an Ideal Material for Electrocatalytically Switchable CO2 Capture.

    Science.gov (United States)

    Tan, Xin; Kou, Liangzhi; Tahini, Hassan A; Smith, Sean C

    2015-12-01

    Good electrical conductivity and high electron mobility of the sorbent materials are prerequisite for electrocatalytically switchable CO2 capture. However, no conductive and easily synthetic sorbent materials are available until now. Here, we examined the possibility of conductive graphitic carbon nitride (g-C4N3) nanosheets as sorbent materials for electrocatalytically switchable CO2 capture. Using first-principle calculations, we found that the adsorption energy of CO2 molecules on g-C4N3 nanosheets can be dramatically enhanced by injecting extra electrons into the adsorbent. At saturation CO2 capture coverage, the negatively charged g-C4N3 nanosheets achieve CO2 capture capacities up to 73.9 × 10(13) cm(-2) or 42.3 wt%. In contrast to other CO2 capture approaches, the process of CO2 capture/release occurs spontaneously without any energy barriers once extra electrons are introduced or removed, and these processes can be simply controlled and reversed by switching on/off the charging voltage. In addition, these negatively charged g-C4N3 nanosheets are highly selective for separating CO2 from mixtures with CH4, H2 and/or N2. These predictions may prove to be instrumental in searching for a new class of experimentally feasible high-capacity CO2 capture materials with ideal thermodynamics and reversibility.

  15. Conductive Graphitic Carbon Nitride as an Ideal Material for Electrocatalytically Switchable CO2 Capture

    Science.gov (United States)

    Tan, Xin; Kou, Liangzhi; Tahini, Hassan A.; Smith, Sean C.

    2015-12-01

    Good electrical conductivity and high electron mobility of the sorbent materials are prerequisite for electrocatalytically switchable CO2 capture. However, no conductive and easily synthetic sorbent materials are available until now. Here, we examined the possibility of conductive graphitic carbon nitride (g-C4N3) nanosheets as sorbent materials for electrocatalytically switchable CO2 capture. Using first-principle calculations, we found that the adsorption energy of CO2 molecules on g-C4N3 nanosheets can be dramatically enhanced by injecting extra electrons into the adsorbent. At saturation CO2 capture coverage, the negatively charged g-C4N3 nanosheets achieve CO2 capture capacities up to 73.9 × 1013 cm-2 or 42.3 wt%. In contrast to other CO2 capture approaches, the process of CO2 capture/release occurs spontaneously without any energy barriers once extra electrons are introduced or removed, and these processes can be simply controlled and reversed by switching on/off the charging voltage. In addition, these negatively charged g-C4N3 nanosheets are highly selective for separating CO2 from mixtures with CH4, H2 and/or N2. These predictions may prove to be instrumental in searching for a new class of experimentally feasible high-capacity CO2 capture materials with ideal thermodynamics and reversibility.

  16. Conductive Graphitic Carbon Nitride as an Ideal Material for Electrocatalytically Switchable CO2 Capture

    Science.gov (United States)

    Tan, Xin; Kou, Liangzhi; Tahini, Hassan A.; Smith, Sean C.

    2015-01-01

    Good electrical conductivity and high electron mobility of the sorbent materials are prerequisite for electrocatalytically switchable CO2 capture. However, no conductive and easily synthetic sorbent materials are available until now. Here, we examined the possibility of conductive graphitic carbon nitride (g-C4N3) nanosheets as sorbent materials for electrocatalytically switchable CO2 capture. Using first-principle calculations, we found that the adsorption energy of CO2 molecules on g-C4N3 nanosheets can be dramatically enhanced by injecting extra electrons into the adsorbent. At saturation CO2 capture coverage, the negatively charged g-C4N3 nanosheets achieve CO2 capture capacities up to 73.9 × 1013 cm−2 or 42.3 wt%. In contrast to other CO2 capture approaches, the process of CO2 capture/release occurs spontaneously without any energy barriers once extra electrons are introduced or removed, and these processes can be simply controlled and reversed by switching on/off the charging voltage. In addition, these negatively charged g-C4N3 nanosheets are highly selective for separating CO2 from mixtures with CH4, H2 and/or N2. These predictions may prove to be instrumental in searching for a new class of experimentally feasible high-capacity CO2 capture materials with ideal thermodynamics and reversibility. PMID:26621618

  17. Modeling, Growth and Characterization of III-V and Dilute Nitride Antimonide Materials and Solar Cells

    Science.gov (United States)

    Maros, Aymeric

    III-V multijunction solar cells have demonstrated record efficiencies with the best device currently at 46 % under concentration. Dilute nitride materials such as GaInNAsSb have been identified as a prime choice for the development of high efficiency, monolithic and lattice-matched multijunction solar cells as they can be lattice-matched to both GaAs and Ge substrates. These types of cells have demonstrated efficiencies of 44% for terrestrial concentrators, and with their upright configuration, they are a direct drop-in product for today's space and concentrator solar panels. The work presented in this dissertation has focused on the development of relatively novel dilute nitride antimonide (GaNAsSb) materials and solar cells using plasma-assisted molecular beam epitaxy, along with the modeling and characterization of single- and multijunction solar cells. Nitrogen-free ternary compounds such as GaInAs and GaAsSb were investigated first in order to understand their structural and optical properties prior to introducing nitrogen. The formation of extended defects and the resulting strain relaxation in these lattice-mismatched materials is investigated through extensive structural characterization. Temperature- and power-dependent photoluminescence revealed an inhomogeneous distribution of Sb in GaAsSb films, leading to carrier localization effects at low temperatures. Tuning of the growth parameters was shown to suppress these Sb-induced localized states. The introduction of nitrogen was then considered and the growth process was optimized to obtain high quality GaNAsSb films lattice-matched to GaAs. Near 1-eV single-junction GaNAsSb solar cells were produced. The best devices used a p-n heterojunction configuration and demonstrated a current density of 20.8 mA/cm2, a fill factor of 64 % and an open-circuit voltage of 0.39 V, corresponding to a bandgap-voltage offset of 0.57 V, comparable with the state-of-the-art for this type of solar cells. Post-growth annealing

  18. Assessing the Reliability of Material Flow Analysis Results: The Cases of Rhenium, Gallium, and Germanium in the United States Economy.

    Science.gov (United States)

    Meylan, Grégoire; Reck, Barbara K; Rechberger, Helmut; Graedel, Thomas E; Schwab, Oliver

    2017-10-17

    Decision-makers traditionally expect "hard facts" from scientific inquiry, an expectation that the results of material flow analyses (MFAs) can hardly meet. MFA limitations are attributable to incompleteness of flowcharts, limited data quality, and model assumptions. Moreover, MFA results are, for the most part, based less on empirical observation but rather on social knowledge construction processes. Developing, applying, and improving the means of evaluating and communicating the reliability of MFA results is imperative. We apply two recently proposed approaches for making quantitative statements on MFA reliability to national minor metals systems: rhenium, gallium, and germanium in the United States in 2012. We discuss the reliability of results in policy and management contexts. The first approach consists of assessing data quality based on systematic characterization of MFA data and the associated meta-information and quantifying the "information content" of MFAs. The second is a quantification of data inconsistencies indicated by the "degree of data reconciliation" between the data and the model. A high information content and a low degree of reconciliation indicate reliable or certain MFA results. This article contributes to reliability and uncertainty discourses in MFA, exemplifying the usefulness of the approaches in policy and management, and to raw material supply discussions by providing country-level information on three important minor metals often considered critical.

  19. Crystalline boron nitride aerogels

    Energy Technology Data Exchange (ETDEWEB)

    Zettl, Alexander K.; Rousseas, Michael; Goldstein, Anna P.; Mickelson, William; Worsley, Marcus A.; Woo, Leta

    2017-12-12

    This disclosure provides methods and materials related to boron nitride aerogels. For example, one aspect relates to a method for making an aerogel comprising boron nitride, comprising: (a) providing boron oxide and an aerogel comprising carbon; (b) heating the boron oxide to melt the boron oxide and heating the aerogel; (c) mixing a nitrogen-containing gas with boron oxide vapor from molten boron oxide; and (d) converting at least a portion of the carbon to boron nitride to obtain the aerogel comprising boron nitride. Another aspect relates to a method for making an aerogel comprising boron nitride, comprising heating boron oxide and an aerogel comprising carbon under flow of a nitrogen-containing gas, wherein boron oxide vapor and the nitrogen-containing gas convert at least a portion of the carbon to boron nitride to obtain the aerogel comprising boron nitride.

  20. Characterization of nanostructure ferrite material on gallium nitride on SiC substrate for millimeter wave integrated circuit

    Science.gov (United States)

    O'Keefe, Brian; Liang, Tinghao; Afsar, Mohammad N.; Koomson, Valencia J.

    2017-05-01

    In this paper, for the first time, the characterization of spin-casted thick Barium nano-hexaferrite film on GaN-on-SiC substrate over a broad frequency range of 30-110 GHz is presented. Real and imaginary parts of both permittivity and permeability of the ferrite/polymer film are computed from transmittance data obtained by using a free space quasi-optical millimeter wave spectrometer. The spin-casted composite film shows strong resonance in the Q band, and mixing the powder with polymer slightly shifts the resonance frequency lower compared to pure powder. The high temperature compatibility of GaN substrate enables us to run burn-out tests at temperatures up to 900°C. Significant shortening phenomenon of resonance linewidth after heat treatment was found. Linewidth is reduced from 2.8 kOe to 1.7 kOe. Experiment results show that the aforementioned film is a good candidate in applications of non-reciprocal ferrite devices like isolators, phase shifters, and circulators.

  1. Characterization of nanostructure ferrite material on gallium nitride on SiC substrate for millimeter wave integrated circuit

    Directory of Open Access Journals (Sweden)

    Brian O’Keefe

    2017-05-01

    Full Text Available In this paper, for the first time, the characterization of spin-casted thick Barium nano-hexaferrite film on GaN-on-SiC substrate over a broad frequency range of 30-110 GHz is presented. Real and imaginary parts of both permittivity and permeability of the ferrite/polymer film are computed from transmittance data obtained by using a free space quasi-optical millimeter wave spectrometer. The spin-casted composite film shows strong resonance in the Q band, and mixing the powder with polymer slightly shifts the resonance frequency lower compared to pure powder. The high temperature compatibility of GaN substrate enables us to run burn-out tests at temperatures up to 900°C. Significant shortening phenomenon of resonance linewidth after heat treatment was found. Linewidth is reduced from 2.8 kOe to 1.7 kOe. Experiment results show that the aforementioned film is a good candidate in applications of non-reciprocal ferrite devices like isolators, phase shifters, and circulators.

  2. Development of an aluminum nitride-silicon carbide material set for high-temperature sensor applications

    Science.gov (United States)

    Griffin, Benjamin A.; Habermehl, Scott D.; Clews, Peggy J.

    2014-06-01

    A number of important energy and defense-related applications would benefit from sensors capable of withstanding extreme temperatures (>300°C). Examples include sensors for automobile engines, gas turbines, nuclear and coal power plants, and petroleum and geothermal well drilling. Military applications, such as hypersonic flight research, would also benefit from sensors capable of 1000°C. Silicon carbide (SiC) has long been recognized as a promising material for harsh environment sensors and electronics because it has the highest mechanical strength of semiconductors with the exception of diamond and its upper temperature limit exceeds 2500°C, where it sublimates rather than melts. Yet today, many advanced SiC MEMS are limited to lower temperatures because they are made from SiC films deposited on silicon wafers. Other limitations arise from sensor transduction by measuring changes in capacitance or resistance, which require biasing or modulation schemes that can with- stand elevated temperatures. We are circumventing these issues by developing sensing structures directly on SiC wafers using SiC and piezoelectric aluminum nitride (AlN) thin films. SiC and AlN are a promising material combination due to their high thermal, electrical, and mechanical strength and closely matched coefficients of thermal expansion. AlN is also a non-ferroelectric piezoelectric material, enabling piezoelectric transduction at temperatures exceeding 1000°C. In this paper, the challenges of incorporating these two materials into a compatible MEMS fabrication process are presented. The current progress and initial measurements of the fabrication process are shown. The future direction and the need for further investigation of the material set are addressed.

  3. 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.

    Science.gov (United States)

    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.

  4. Metal Nitrides for Plasmonic Applications

    DEFF Research Database (Denmark)

    Naik, Gururaj V.; Schroeder, Jeremy; Guler, Urcan

    2012-01-01

    Metal nitrides as alternatives to metals such as gold could offer many advantages when used as plasmonic material. We show that transition metal nitrides can replace metals providing equally good optical performance for many plasmonic applications.......Metal nitrides as alternatives to metals such as gold could offer many advantages when used as plasmonic material. We show that transition metal nitrides can replace metals providing equally good optical performance for many plasmonic applications....

  5. A color-tunable luminescent material with functionalized graphitic carbon nitride as multifunctional supports

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Jiutian; Cao, Yudong; Fan, Hai; Hou, Juying; Ai, Shiyun, E-mail: ashy@sdau.edu.cn

    2015-12-15

    A color-tunable luminescent material was prepared based on the composition of functionalized graphitic carbon nitride (g-C{sub 3}N{sub 4}) and europium (III). The functionalized g-C{sub 3}N{sub 4} layers not only behave as multifunctional supports including ligand coordinated with europium (III) and a support structure for the formation of the luminescent material, but exhibit excitation wavelength-dependent luminescence, thus the energy transfer between the functionalized g-C{sub 3}N{sub 4} and europium (III) can match very well by controlling the emission wavelength of functionalized g-C{sub 3}N{sub 4}. The as-prepared materials was comprehensively characterized via X-ray photoelectron spectroscopy, Fourier Transform Infrared spectroscopy, X-ray scattering techniques, Ultraviolet and Visible spectrophotometer, fluorescence spectrophotometer, thermogravimetric analysis, etc. The luminescent material exhibits multi-color emissions which are consistent with the characteristic emissions of europium (III) and functionalized g-C{sub 3}N{sub 4}, and the photoluminescence quality and density of the europium (III) can be greatly enhanced. The brilliant optical properties of the materials make them suiting for multipurpose applications in practical fields. - Graphical abstract: Schematic illustration of the synthesis and basic composition of the luminescent material. Inset figures were luminescence emission spectra of g-C{sub 3}N{sub 4} (A), europium (III) complex (a) and luminescent material (b) with the same concentration in (B) (K{sub ex}=350 nm) and photographs of (left) H{sub 2}O and (right) the H{sub 2}O dispersion of luminescence emission spectra under 350 nm UV radiation. The energy transfer in the luminescent material matchs very well and it exhibits multi-color emissions simultaneously. The enhanced photoluminescence quality and density of the europium (III) makes them suiting for multipurpose applications in practical fields. - Highlights: • Luminescent

  6. Gallium interstitial contributions to diffusion in gallium arsenide

    Science.gov (United States)

    Schick, Joseph T.; Morgan, Caroline G.

    2011-09-01

    A new diffusion path is identified for gallium interstitials, which involves lower barriers than the barriers for previously identified diffusion paths [K. Levasseur-Smith and N. Mousseau, J. Appl. Phys. 103, 113502 (2008), P. A. Schultz and O. A. von Lilienfeld, Modelling and Simulation in Materials Science and Engineering 17, 084007 (2009)] for the charge states which dominate diffusion over most of the available range of Fermi energies. This path passes through the ⟨110⟩ gallium-gallium split interstitial configuration, and has a particularly low diffusion barrier of 0.35 eV for diffusion in the neutral charge state. As a part of this work, the character of the charge states for the gallium interstitials which are most important for diffusion is investigated, and it is shown that the last electron bound to the neutral interstitial occupies a shallow hydrogenic bound state composed of conduction band states for the hexagonal interstitial and both tetrahedral interstitials. How to properly account for the contributions of such interstitials is discussed for density-functional calculations with a k-point mesh not including the conduction band edge point. Diffusion barriers for gallium interstitials are calculated in all the charge states which can be important for a Fermi level anywhere in the gap, q = 0, +1, +2, and +3, for diffusion via the ⟨110⟩ gallium-gallium split interstitial configuration and via the hexagonal interstitial configuration. The lowest activation enthalpies over most of the available range of Fermi energies are found to correspond to diffusion in the neutral or singly positive state via the ⟨110⟩ gallium-gallium split interstitial configuration. It is shown that several different charge states and diffusion paths contribute significantly for Fermi levels within 0.2 eV above the valence band edge, which may help to explain some of the difficulties [H. Bracht and S. Brotzmann, Phys. Rev. B 71, 115216 (2005)] which have been

  7. Gallium interstitial contributions to diffusion in gallium arsenide

    Directory of Open Access Journals (Sweden)

    Joseph T. Schick

    2011-09-01

    Full Text Available A new diffusion path is identified for gallium interstitials, which involves lower barriers than the barriers for previously identified diffusion paths [K. Levasseur-Smith and N. Mousseau, J. Appl. Phys. 103, 113502 (2008, P. A. Schultz and O. A. von Lilienfeld, Modelling and Simulation in Materials Science and Engineering 17, 084007 (2009] for the charge states which dominate diffusion over most of the available range of Fermi energies. This path passes through the ⟨110⟩ gallium-gallium split interstitial configuration, and has a particularly low diffusion barrier of 0.35 eV for diffusion in the neutral charge state. As a part of this work, the character of the charge states for the gallium interstitials which are most important for diffusion is investigated, and it is shown that the last electron bound to the neutral interstitial occupies a shallow hydrogenic bound state composed of conduction band states for the hexagonal interstitial and both tetrahedral interstitials. How to properly account for the contributions of such interstitials is discussed for density-functional calculations with a k-point mesh not including the conduction band edge point. Diffusion barriers for gallium interstitials are calculated in all the charge states which can be important for a Fermi level anywhere in the gap, q = 0, +1, +2, and +3, for diffusion via the ⟨110⟩ gallium-gallium split interstitial configuration and via the hexagonal interstitial configuration. The lowest activation enthalpies over most of the available range of Fermi energies are found to correspond to diffusion in the neutral or singly positive state via the ⟨110⟩ gallium-gallium split interstitial configuration. It is shown that several different charge states and diffusion paths contribute significantly for Fermi levels within 0.2 eV above the valence band edge, which may help to explain some of the difficulties [H. Bracht and S. Brotzmann, Phys. Rev. B 71, 115216 (2005] which

  8. Fabrication of Silicon Nitride Dental Core Ceramics with Borosilicate Veneering material

    International Nuclear Information System (INIS)

    Wananuruksawong, R; Jinawath, S; Wasanapiarnpong, T; Padipatvuthikul, P

    2011-01-01

    Silicon nitride (Si 3 N 4 ) ceramic is a great candidate for clinical applications due to its high fracture toughness, strength, hardness and bio-inertness. This study has focused on the Si 3 N 4 ceramic as a dental core material. The white Si 3 N 4 was prepared by pressureless sintering at relative low sintering temperature of 1650 deg. C in nitrogen atmosphere. The coefficient of thermal expansion (CTE) of Si 3 N 4 ceramic is lower than that of Zirconia and Alumina ceramic which are popular in this field. The borosilicate glass veneering was employed due to its compatibility in thermal expansion. The sintered Si 3 N 4 specimens represented the synthetic dental core were paintbrush coated by a veneer paste composed of borosilicate glass powder ( 2 O 3 - partial stabilized zirconia) and 30 wt% of polyvinyl alcohol (5 wt% solution). After coating the veneer on the Si 3 N 4 specimens, the firing was performed in electric tube furnace between 1000-1200 deg. C. The veneered specimens fired at 1100 deg. C for 15 mins show good bonding, smooth and glossy without defect and crazing. The veneer has thermal expansion coefficient as 3.98x10 -6 deg. C -1 , rather white and semi opaque, due to zirconia addition, the Vickers hardness as 4.0 GPa which is closely to the human teeth.

  9. Fabrication of Silicon Nitride Dental Core Ceramics with Borosilicate Veneering material

    Science.gov (United States)

    Wananuruksawong, R.; Jinawath, S.; Padipatvuthikul, P.; Wasanapiarnpong, T.

    2011-10-01

    Silicon nitride (Si3N4) ceramic is a great candidate for clinical applications due to its high fracture toughness, strength, hardness and bio-inertness. This study has focused on the Si3N4 ceramic as a dental core material. The white Si3N4 was prepared by pressureless sintering at relative low sintering temperature of 1650 °C in nitrogen atmosphere. The coefficient of thermal expansion (CTE) of Si3N4 ceramic is lower than that of Zirconia and Alumina ceramic which are popular in this field. The borosilicate glass veneering was employed due to its compatibility in thermal expansion. The sintered Si3N4 specimens represented the synthetic dental core were paintbrush coated by a veneer paste composed of borosilicate glass powder (<150 micrometer, Pyrex) with 5 wt% of zirconia powder (3 wt% Y2O3 - partial stabilized zirconia) and 30 wt% of polyvinyl alcohol (5 wt% solution). After coating the veneer on the Si3N4 specimens, the firing was performed in electric tube furnace between 1000-1200°C. The veneered specimens fired at 1100°C for 15 mins show good bonding, smooth and glossy without defect and crazing. The veneer has thermal expansion coefficient as 3.98×10-6 °C-1, rather white and semi opaque, due to zirconia addition, the Vickers hardness as 4.0 GPa which is closely to the human teeth.

  10. Chemisorption of Hydroxide on 2D Materials from DFT Calculations: Graphene versus Hexagonal Boron Nitride.

    Science.gov (United States)

    Grosjean, Benoit; Pean, Clarisse; Siria, Alessandro; Bocquet, Lydéric; Vuilleumier, Rodolphe; Bocquet, Marie-Laure

    2016-11-17

    Recent nanofluidic experiments revealed strongly different surface charge measurements for boron-nitride (BN) and graphitic nanotubes when in contact with saline and alkaline water (Nature 2013, 494, 455-458; Phys. Rev. Lett. 2016, 116, 154501). These observations contrast with the similar reactivity of a graphene layer and its BN counterpart, using density functional theory (DFT) framework, for intact and dissociative adsorption of gaseous water molecules. Here we investigate, by DFT in implicit water, single and multiple adsorption of anionic hydroxide on single layers. A differential adsorption strength is found in vacuum for the first ionic adsorption on the two materials-chemisorbed on BN while physisorbed on graphene. The effect of implicit solvation reduces all adsorption values, resulting in a favorable (nonfavorable) adsorption on BN (graphene). We also calculate a pK a ≃ 6 for BN in water, in good agreement with experiments. Comparatively, the unfavorable results for graphene in water echo the weaker surface charge measurements but point to an alternative scenario.

  11. Single Photon Counting UV Solar-Blind Detectors Using Silicon and III-Nitride Materials

    Directory of Open Access Journals (Sweden)

    Shouleh Nikzad

    2016-06-01

    Full Text Available Ultraviolet (UV studies in astronomy, cosmology, planetary studies, biological and medical applications often require precision detection of faint objects and in many cases require photon-counting detection. We present an overview of two approaches for achieving photon counting in the UV. The first approach involves UV enhancement of photon-counting silicon detectors, including electron multiplying charge-coupled devices and avalanche photodiodes. The approach used here employs molecular beam epitaxy for delta doping and superlattice doping for surface passivation and high UV quantum efficiency. Additional UV enhancements include antireflection (AR and solar-blind UV bandpass coatings prepared by atomic layer deposition. Quantum efficiency (QE measurements show QE > 50% in the 100–300 nm range for detectors with simple AR coatings, and QE ≅ 80% at ~206 nm has been shown when more complex AR coatings are used. The second approach is based on avalanche photodiodes in III-nitride materials with high QE and intrinsic solar blindness.

  12. Co-implantation of carbon and nitrogen into silicon dioxide for synthesis of carbon nitride materials

    CERN Document Server

    Huang, M B; Nuesca, G; Moore, R

    2002-01-01

    Materials synthesis of carbon nitride has been attempted with co-implantation of carbon and nitrogen into thermally grown SiO sub 2. Following implantation of C and N ions to doses of 10 sup 1 sup 7 cm sup - sup 2 , thermal annealing of the implanted SiO sub 2 sample was conducted at 1000 degree sign C in an N sub 2 ambient. As evidenced in Fourier transform infrared measurements and X-ray photoelectron spectroscopy, different bonding configurations between C and N, including C-N single bonds, C=N double bonds and C=N triple bonds, were found to develop in the SiO sub 2 film after annealing. Chemical composition profiles obtained with secondary ion mass spectroscopy were correlated with the depth information of the chemical shifts of N 1s core-level electrons, allowing us to examine the formation of C-N bonding for different atomic concentration ratios between N and C. X-ray diffraction and transmission electron microscopy showed no sign of the formation of crystalline C sub 3 N sub 4 precipitates in the SiO ...

  13. Single photon emitters in boron nitride: More than a supplementary material

    Science.gov (United States)

    Koperski, M.; Nogajewski, K.; Potemski, M.

    2018-03-01

    We present comprehensive optical studies of recently discovered single photon sources in boron nitride, which appear in form of narrow lines emitting centres. Here, we aim to compactly characterise their basic optical properties, including the demonstration of several novel findings, in order to inspire discussion about their origin and utility. Initial inspection reveals the presence of narrow emission lines in boron nitride powder and exfoliated flakes of hexagonal boron nitride deposited on Si/SiO2 substrates. Generally rather stable, the boron nitride emitters constitute a good quality visible light source. However, as briefly discussed, certain specimens reveal a peculiar type of blinking effects, which are likely related to existence of meta-stable electronic states. More advanced characterisation of representative stable emitting centres uncovers a strong dependence of the emission intensity on the energy and polarisation of excitation. On this basis, we speculate that rather strict excitation selectivity is an important factor determining the character of the emission spectra, which allows the observation of single and well-isolated emitters. Finally, we investigate the properties of the emitting centres in varying external conditions. Quite surprisingly, it is found that the application of a magnetic field introduces no change in the emission spectra of boron nitride emitters. Further analysis of the impact of temperature on the emission spectra and the features seen in second-order correlation functions is used to provide an assessment of the potential functionality of boron nitride emitters as single photon sources capable of room temperature operation.

  14. Engineering barrier materials in niobium and niobium nitride Josephson junctions for high-speed superconductor electronics

    Science.gov (United States)

    Kaul, Anupama Bhat

    Superconductor electronics promises some of the highest circuit speeds of any known digital technology. Two classes of superconducting logic families exist: voltage-state logic, and Rapid-Single-Flux-Quantum (RSFQ) logic. The ideal devices for the two logic families are fundamentally different. In this dissertation, we describe alterations in the barrier materials of the respective devices, coupled with process innovations, which lead to junctions that enable higher speed operation. For voltage-state logic, where speeds are limited by junction capacitance, a high-Jc process was developed, where thin AlOx barrier layers were formed in Nb/Al-AlOx/Nb trilayers. Small-area devices of inherently lower capacitance were fabricated, which was made possible by an anodization step, and this obviated complicated planarization techniques. This high-Jc process was used to demonstrate a clocked Josephson amplifier, whose design, simulation and high-speed test results were presented. The circuit was fabricated in a 9.4 kA/cm2 process, and was operational to speeds of at least 10 GHz. It exhibited error rates as low as 5 x 10-12 at 5 GHz, and eye diagram measurements revealed a clear-eye area, even up to 10 GHz. This Josephson amplifier represents the first circuit to be fabricated and successfully tested in a ˜10 kA/cm 2 process, and is of importance for interfacing superconductive circuitry with semiconductor electronics. While the basic device for voltage-state logic is the superconductor/insulator/superconductor (SIS) junction, the ideal device for RSFQ technology is a superconductor/normal-conductor/superconductor (SNS) junction. Since the figure of merit of this device, the IcR n, is directly influenced by the resistivity of the barrier material, high resistivity materials are desired to raise Rn, without significantly reducing Ic. We have proposed and demonstrated a new barrier material TaNx with NbN electrodes for the realization of an all-nitride SNS junction technology

  15. Chemically linked metal-matrix nanocomposites of boron nitride nanosheets and silver as thermal interface materials

    Science.gov (United States)

    Nagabandi, N.; Yegin, C.; Feng, X.; King, C.; Oh, J. K.; Scholar, E. A.; Narumanchi, S.; Akbulut, M.

    2018-03-01

    Herein, novel hybrid nanocomposite thermal interface materials (TIMs) relying on the chemical linkage of silver, boron nitride nanosheets (BNNSs), and organic ligands are reported. These TIMs were prepared using a co-electrodeposition/chemisorption approach where the electrolytic reduction of silver ions into silver nano-/micro-crystals was coupled with the conjugation of ligand-coated nanosheets onto silver crystals. Furthermore, the influence of the bond strength of silver/nanosheet links on the thermal, mechanical, and structural properties is investigated using a combination of techniques including laser flash analysis, phase-sensitive transient thermoreflectance, nanoindentation, and electron microscopy. The internal nanostructure was found to be strongly dependent on the linker chemistry. While the chemical grafting of 4-cyano-benzoyl chloride (CBC) and 2-mercapto-5-benzimidazole carboxylic acid (MBCA) on BNNSs led to the uniform distribution of functionalized-nanosheets in the silver crystal matrix, the physical binding of 4-bromo-benzoyl chloride linkers on nanosheets caused the aggregation and phase separation. The thermal conductivity was 236-258 W m-1 K and 306-321 W m-1 K for physically and chemically conjugated TIMs, respectively, while their hardness varied from 400-495 MPa and from 240 to 360 MPa, respectively. The corresponding ratio of thermal conductivity to hardness, which is a critical parameter controlling the performance of TIMs, was ultrahigh for the chemically conjugated TIMs: 1.3 × 10-6 m2 K-1 s for MBCA-BNNS and 8.5 × 10-7 m2 K-1 s for CBC-BNNS. We anticipate that these materials can satisfy some of the emerging thermal management needs arising from the improved performance and efficiency, miniaturization, and/or high throughput of electronic devices, energy storage devices, energy conversion systems, light-emitting diodes, and telecommunication components.

  16. Chemically Linked Metal-Matrix Nanocomposites of Boron Nitride Nanosheets and Silver as Thermal Interface Materials

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Xuhui [National Renewable Energy Laboratory (NREL), Golden, CO (United States); King, Charles C [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Narumanchi, Sreekant V [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Nagabandi, Nirup [Texas A& M University; Yegin, Cengiz [Texas A& M University; Oh, Jun Kyun [Texas A& M University; Scholar, Ethan Adam [Texas A& M University; Akbulut, Mustafa [Texas A& M University

    2018-01-31

    Herein, novel hybrid nanocomposite thermal interface materials (TIMs) relying on the chemical linkage of silver, boron nitride nanosheets (BNNSs), and organic ligands are reported. These TIMs were prepared using a co-electrodeposition/chemisorption approach where the electrolytic reduction of silver ions into silver nano-/micro-crystals was coupled with the conjugation of ligand-coated nanosheets onto silver crystals. Furthermore, the influence of bond strength of silver/nanosheet links on the thermal, mechanical, and structural properties is investigated using a combination of techniques; including laser flash analysis, phase-sensitive transient thermoreflectance, nanoindentation, and electron microscopy. Internal nanostructure was found to be strongly dependent on the linker chemistry. While the chemical grafting of 4-cyano-benzoyl chloride (CBC) and 2-mercapto-5-benzimidazole carboxylic acid (MBCA) on BNNSs led to the uniform distribution of functionalized-nanosheets in the silver crystal matrix, the physical binding of 4-bromo-benzoyl chloride (BBC) linkers on nanosheets caused the aggregation and phase separation. The thermal conductivity was 236-258 W/m-K and 306-321 W/m-K for physically and chemically conjugated TIMs, respectively, while their hardness varied from 495 to 400 MPa and from 240 to 360 MPa, respectively. The corresponding ratio of thermal conductivity to hardness, which is a critical parameter controlling the performance of TIMs, was ultrahigh for the chemically conjugated TIMs: 1.3x10-6 m2/K-s for MBCA-BNNS and 8.5x10-7 m2/K-s for CBC-BNNS. We anticipate that these materials can satisfy some of the emerging thermal management needs arising from the improved performance and efficiency, miniaturization, and/or high throughput of electronic devices, energy storage devices, energy conversion systems, light-emitting diodes, and telecommunication components.

  17. Gallium imaging in pediatrics

    International Nuclear Information System (INIS)

    Handmaker, H.; O'Mara, R.E.

    1977-01-01

    Gallium-67 citrate imaging was carried out in 59 children from 3 mo to 20 yr of age. Indications for the study included the search for occult inflammatory disease and the detection and staging of malignant disease. The Ga-67 citrate scan had a 96% reliability in confirming or excluding the site of purulent material as a cause of sepsis, and 76% reliability in detecting malignant disease. Tissue distributions in children differ from those in adults primarily in that the epiphyseal plates, spleen, and thymus may show increased activity normally and in the presence of sepsis. These variations are illustrated as possible sources of incorrect interpretation. ''Cold'' defects may be seen in sterile collections and avascular masses. Experience in this age group seems sufficiently encouraging to continue the use of gallium-67 citrate for the purposes described

  18. Fabrication of Silicon Nitride Dental Core Ceramics with Borosilicate Veneering material

    Energy Technology Data Exchange (ETDEWEB)

    Wananuruksawong, R; Jinawath, S; Wasanapiarnpong, T [Research Unit of Advanced Ceramic, Department of Materials Science, Faculty of Science, Chulalongkorn University, Bangkok (Thailand); Padipatvuthikul, P, E-mail: raayaa_chula@hotmail.com [Faculty of Dentistry, Srinakharinwirot University, Bangkok (Thailand)

    2011-10-29

    Silicon nitride (Si{sub 3}N{sub 4}) ceramic is a great candidate for clinical applications due to its high fracture toughness, strength, hardness and bio-inertness. This study has focused on the Si{sub 3}N{sub 4} ceramic as a dental core material. The white Si{sub 3}N{sub 4} was prepared by pressureless sintering at relative low sintering temperature of 1650 deg. C in nitrogen atmosphere. The coefficient of thermal expansion (CTE) of Si{sub 3}N{sub 4} ceramic is lower than that of Zirconia and Alumina ceramic which are popular in this field. The borosilicate glass veneering was employed due to its compatibility in thermal expansion. The sintered Si{sub 3}N{sub 4} specimens represented the synthetic dental core were paintbrush coated by a veneer paste composed of borosilicate glass powder (<150 micrometer, Pyrex) with 5 wt% of zirconia powder (3 wt% Y{sub 2}O{sub 3} - partial stabilized zirconia) and 30 wt% of polyvinyl alcohol (5 wt% solution). After coating the veneer on the Si{sub 3}N{sub 4} specimens, the firing was performed in electric tube furnace between 1000-1200 deg. C. The veneered specimens fired at 1100 deg. C for 15 mins show good bonding, smooth and glossy without defect and crazing. The veneer has thermal expansion coefficient as 3.98x10{sup -6} deg. C{sup -1}, rather white and semi opaque, due to zirconia addition, the Vickers hardness as 4.0 GPa which is closely to the human teeth.

  19. Toxicity of indium arsenide, gallium arsenide, and aluminium gallium arsenide.

    Science.gov (United States)

    Tanaka, Akiyo

    2004-08-01

    Gallium arsenide (GaAs), indium arsenide (InAs), and aluminium gallium arsenide (AlGaAs) are semiconductor applications. Although the increased use of these materials has raised concerns about occupational exposure to them, there is little information regarding the adverse health effects to workers arising from exposure to these particles. However, available data indicate these semiconductor materials can be toxic in animals. Although acute and chronic toxicity of the lung, reproductive organs, and kidney are associated with exposure to these semiconductor materials, in particular, chronic toxicity should pay much attention owing to low solubility of these materials. Between InAs, GaAs, and AlGaAs, InAs was the most toxic material to the lung followed by GaAs and AlGaAs when given intratracheally. This was probably due to difference in the toxicity of the counter-element of arsenic in semiconductor materials, such as indium, gallium, or aluminium, and not arsenic itself. It appeared that indium, gallium, or aluminium was toxic when released from the particles, though the physical character of the particles also contributes to toxic effect. Although there is no evidence of the carcinogenicity of InAs or AlGaAs, GaAs and InP, which are semiconductor materials, showed the clear evidence of carcinogenic potential. It is necessary to pay much greater attention to the human exposure of semiconductor materials.

  20. Narrow energy band gap gallium arsenide nitride semi-conductors and an ion-cut-synthesis method for producing the same

    Science.gov (United States)

    Weng, Xiaojun; Goldman, Rachel S.

    2006-06-06

    A method for forming a semi-conductor material is provided that comprises forming a donor substrate constructed of GaAs, providing a receiver substrate, implanting nitrogen into the donor substrate to form an implanted layer comprising GaAs and nitrogen. The implanted layer is bonded to the receiver substrate and annealed to form GaAsN and nitrogen micro-blisters in the implanted layer. The micro-blisters allow the implanted layer to be cleaved from the donor substrate.

  1. (-201) β-Gallium oxide substrate for high quality GaN materials

    KAUST Repository

    Roqan, Iman S.

    2015-03-13

    (-201) oriented β-Ga2O3 has the potential to be used as a transparent and conductive substrate for GaN-growth. The key advantages of Ga2O3 are its small lattice mismatches (4.7%), appropriate structural, thermal and electrical properties and a competitive price compared to other substrates. Optical characterization show that GaN layers grown on (-201) oriented β-Ga2O3 are dominated by intense bandedge emission with a high luminescence efficiency. Atomic force microscopy studies show a modest threading dislocation density of ~108 cm-2, while complementary Raman spectroscopy indicates that the GaN epilayer is of high quality with slight compressive strain. Room temperature time-findings suggest that the limitation of the photoluminescence lifetime (~500 ps) is due to nonradiative recombination arising from threading dislocation. Therefore, by optimizing the growth conditions, high quality material with significant optical efficiency can be obtained.

  2. Indium(III) and Gallium(III) phthalocyanines-based nanohybrid materials for optical limiting

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Huili; Li, Shuai [Key Lab for Adv. Mater., Institute of Applied Chemistry, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237 (China); Wang, Jun, E-mail: jwang@siom.ac.cn [Key Lab of Materials for High-Power Laser, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Blau, Werner J., E-mail: wblau@tcd.ie [School of Physics and the Centre for Research on Adaptative Nanostructures and Nanodevices(CRANN), Trinity College Dublin, Dublin 2 (Ireland); Chen, Yu, E-mail: chentangyu@yahoo.com [Key Lab for Adv. Mater., Institute of Applied Chemistry, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237 (China)

    2012-11-15

    Linear and nonlinear optical properties of a phthalocyanine (Pc)-based nanohybrid material PCIGS [Cu{sub 2}(tBu{sub 4}PcGa)(tBu{sub 4}PcIn)S{sub 2}TPP{sub 2}] are described. The overall aggregation of phthalocyanines in poly(methylmethacrylate) (PMMA) films was evident, which is indicated by the broadening of linear spectra in the Q-band region and the shift of wavelength. Upon excitation with nanosecond laser pulse at 355 nm, the transient absorption band appeared at about 500 nm is attributed to the triplet-triplet absorption of the Pcs. For PCIGS and its starting materials tBu{sub 4}PcGaCl and tBu{sub 4}PcInCl, all Z-scans exhibit a decrease in transmittance about the focus typical of an induced positive nonlinear absorption of incident light. The absorption mechanism is due to population of excited states through a multi-step nonlinear absorption. When these Pc compounds were embedded into a commercially available polymer PMMA, all the Pc/PMMA composites display much larger nonlinear absorption coefficient and lower saturable fluence for optical limiting when compared to the same Pc molecules in solution. However, in contrast to tBu{sub 4}PcGaCl and tBu{sub 4}PcInCl, PCIGS displayed decreased optical limiting response, possibly due to competing electron accepting processes in the In and Ga metals, and the highly ordered structure of the PCIGS complex itself. -- Highlights: Black-Right-Pointing-Pointer The {alpha}{sub 0} values of PCIGS in the solid state is 150 times that in the dilute solution. Black-Right-Pointing-Pointer All the Pc/PMMA composites display lower saturable fluence for optical limiting. Black-Right-Pointing-Pointer PCIGS showed decreased OL responses when compared to tBu{sub 4}PcMCl (M = Ga, In).

  3. Indium(III) and Gallium(III) phthalocyanines-based nanohybrid materials for optical limiting

    International Nuclear Information System (INIS)

    Gu, Huili; Li, Shuai; Wang, Jun; Blau, Werner J.; Chen, Yu

    2012-01-01

    Linear and nonlinear optical properties of a phthalocyanine (Pc)-based nanohybrid material PCIGS [Cu 2 (tBu 4 PcGa)(tBu 4 PcIn)S 2 TPP 2 ] are described. The overall aggregation of phthalocyanines in poly(methylmethacrylate) (PMMA) films was evident, which is indicated by the broadening of linear spectra in the Q-band region and the shift of wavelength. Upon excitation with nanosecond laser pulse at 355 nm, the transient absorption band appeared at about 500 nm is attributed to the triplet–triplet absorption of the Pcs. For PCIGS and its starting materials tBu 4 PcGaCl and tBu 4 PcInCl, all Z-scans exhibit a decrease in transmittance about the focus typical of an induced positive nonlinear absorption of incident light. The absorption mechanism is due to population of excited states through a multi-step nonlinear absorption. When these Pc compounds were embedded into a commercially available polymer PMMA, all the Pc/PMMA composites display much larger nonlinear absorption coefficient and lower saturable fluence for optical limiting when compared to the same Pc molecules in solution. However, in contrast to tBu 4 PcGaCl and tBu 4 PcInCl, PCIGS displayed decreased optical limiting response, possibly due to competing electron accepting processes in the In and Ga metals, and the highly ordered structure of the PCIGS complex itself. -- Highlights: ► The α 0 values of PCIGS in the solid state is 150 times that in the dilute solution. ► All the Pc/PMMA composites display lower saturable fluence for optical limiting. ► PCIGS showed decreased OL responses when compared to tBu 4 PcMCl (M = Ga, In).

  4. Propagation of ultrasonic waves in bulk gallium Nitride (GaN) semiconductor in the presence of high-frequency electric Field

    International Nuclear Information System (INIS)

    Mensah, S.Y.; Mensah, N.G.; Elloh, V.W.; Banini, G.K.; Sam, F.; Allotey, F.K.A.

    2005-01-01

    The propagation of ultrasound is studied in bulk GaN semiconductor in the presence of a strong, ac field oscillating at a frequency much higher than that of the ultrasound. Analytical expressions have been obtained for the attenuation coefficient (α) and the renormalized velocity (ν) of the acoustic wave. It is shown that the dependencies of the ultrasonic absorption coefficient of the conduction electrons and the renormalized sound velocity on the field amplitude and the sound frequency have an oscillatory character which can be used to determine the effective mass and mobility of the material. The threshold field E min = 3.3x10 2 V/ cm needed to observe the oscillation is two orders smaller than that needed in the case of CdS. (author)

  5. Propagation of ultrasonic waves in bulk gallium nitride (GaN) semiconductor in the presence of high-frequency electric field II

    International Nuclear Information System (INIS)

    Elloh, V.W.; Banini, G.K.; Sam, Frederick; Twum, A.K.

    2006-12-01

    We report the calculations of the electron mobility and electron drift-velocity in the propagation of ultrasound in bulk GaN semiconductor in the presence of a strong ac field oscillating at a frequency much higher than that of the ultrasound. Analytical expressions have been obtained for the attenuation coefficient (α) and the renormalized velocity (v) of the acoustic wave. It is shown that the dependencies of the ultrasonic absorption coefficient of the conduction electrons and the renormalized sound velocity on the field amplitude and the sound frequency have an oscillatory character which can be used to determine the effective mass and mobility of the material. The threshold field E min = 3.3 x 10 2 V / cm needed to observe the oscillations is two orders smaller than that needed in the case of CdS. The electron mobility μ = 1500cm 2 / Vs and electron drift-velocity v D 2.7 x 10 7 cm/s are obtained for bulk GaN in the presence of the high-frequency electric field. (author)

  6. Interface phenomena in (super)hard nitride nanocomposites: from coatings to bulk materials.

    Science.gov (United States)

    Rafaja, David; Wüstefeld, Christina; Motylenko, Mykhailo; Schimpf, Christian; Barsukova, Tatiana; Schwarz, Marcus R; Kroke, Edwin

    2012-08-07

    Mechanical properties of nanocomposites usually surpass the mechanical properties of their micro-structured and single-crystalline counterparts. This is mainly due to an extremely high density of internal interfaces in nanocomposites like grain, crystallite and phase boundaries. When compared to diamond, carbides and borides, nitrides are of interest because of their high temperature oxidation resistance and compatibility with iron containing alloys. This tutorial review classifies the contributions of various internal interfaces to the hardness of the nanocomposites, and appreciates the outstanding role of partially coherent phase boundaries in the hardness enhancement. With selected examples of transition metal nitrides containing aluminium and silicon as well as of boron nitrides, it is explained how the nanocomposites with partially coherent phase boundaries and thus with enhanced hardness can be synthesised. As the possible ways of the formation of coherent phase boundaries, the local epitaxial growth of phases with limited mutual solubility, the production of supersaturated solid solutions followed by the segregation of elements during the spinodal decomposition and the incomplete phase transformation are discussed. The most important techniques, used for synthesis of nitride nanocomposites, like CVD, PVD, precursor-based methods, mechanical alloying and high-pressure-high-temperature synthesis are briefly reviewed. Besides, a short overview on hardness definitions and hardness measurements is included.

  7. Thermal expansion of TRU nitride solid solutions as fuel materials for transmutation of minor actinides

    International Nuclear Information System (INIS)

    Takano, Masahide; Akabori, Mitsuo; Arai, Yasuo; Minato, Kazuo

    2009-01-01

    The lattice thermal expansion of the transuranium nitride solid solutions was measured to investigate the composition dependence. The single-phase solid solution samples of (Np 0.55 Am 0.45 )N, (Pu 0.59 Am 0.41 )N, (Np 0.21 Pu 0.52 Am 0.22 Cm 0.05 )N and (Pu 0.21 Am 0.18 Zr 0.61 )N were prepared by carbothermic nitridation of the respective transuranium dioxides and nitridation of Zr metal through hydride. The lattice parameters were measured by the high temperature X-ray diffraction method from room temperature up to 1478 K. The linear thermal expansion of each sample was determined as a function of temperature. The average thermal expansion coefficients over the temperature range of 293-1273 K for the solid solution samples were 10.1, 11.5, 10.8 and 8.8 x 10 -6 K -1 , respectively. Comparison of these values with those for the constituent nitrides showed that the average thermal expansion coefficients of the solid solution samples could be approximated by the linear mixture rule within the error of 2-3%.

  8. Processing to obtain high-purity gallium

    Science.gov (United States)

    Bautista, Renato G.

    2003-03-01

    Gallium has become increasingly popular as a substrate material for electronic devices. Aside from ore, gallium can be obtained from such industrial sources as the Bayer process caustic liquor that is a byproduct of bauxite processing, flue dust removed from the fume-collection system in plants that produce aluminum by the electrolytic process, zinc refinery residues, gallium scrap materials, and coal fly ash. The purification process for gallium can start with solvent-extraction processes where the concentrations of impurities, especially metals, are reduced to the ppm range. This article describes how ultra-purification techniques can be employed to reduce the undesirable impurities to the low ppb range. The various procedures described give an idea as to the extent of work needed to obtain and prepare high-purity gallium for electronic application.

  9. Magnetic semiconductors for spinelectronics. Europium sulfide and magnetically doped gallium nitride; Magnetische Halbleiter zum Einsatz in der Spinelektronik. Europiumsulfid und magnetisch dotiertes Galliumnitrid

    Energy Technology Data Exchange (ETDEWEB)

    Keller, J.

    2007-07-02

    In this work, magnetic semiconductors were investigated. As ferromagnetic compound semiconductor, EuS was investigated as thin film system. Particular attention was paid to the influence of the substrate temperature during growth on the sample properties. The samples grown and investigated here show an anomalous Hall effect. As diluted magnetic semiconductors (DMS), GaN films magnetically doped with Mn or Gd were investigated. In both material systems, ferromagnetism far above room temperature was demonstrated.While GaGdN shows a homogeneous magnetism, all ferromagnetic GaMnN samples show small clusters (phase separations). In addition, measurements of the optical absorption and the magnetic circular dichroism (MCD) were performed on the GaMnN samples. In the optical measurements, the Mn was identified as deep acceptor. At low temperatures, both the magneto-absorption and the MCD show a Zeeman-shift of an absorption band for all doping levels. The exchange energies between valence band and localized magnetic moments can be extracted from fits of the Brillouin function to the Zeeman shifts. This yields values between 1.4 eV and 1.7 eV for the lowest doping levels and between 1.7 eV and 2.1 eV for the highest doped sample. At low temperatures, no ferromagnetic behavior was found in the magneto-optical experiments. The signal is dominated by the localized Mn spin system. At room temperature, the MCD shows a ferromagnetic signature. At elevated temperatures, the signal from the Mn spin system is small enough that the influence of the clusters on the band structure of the host lattice becomes visible. Contrary to the GaMnN samples, the GaGdN films show a homogeneous magnetism. The magnetically doped GaN thin film systems investigated here exhibit different behavior. The exchange mechanism proposed for GaGdN leads to a homogeneous ferromagnetism and is similar to the magnetic exchange in the Eu chalcogenides. The interplay between this intra-atomic f-d exchange and the

  10. Discovery of earth-abundant nitride semiconductors by computational screening and high-pressure synthesis

    OpenAIRE

    Hinuma, Yoyo; Hatakeyama, Taisuke; Kumagai, Yu; Burton, Lee A.; Sato, Hikaru; Muraba, Yoshinori; Iimura, Soshi; Hiramatsu, Hidenori; Tanaka, Isao; Hosono, Hideo; Oba, Fumiyasu

    2016-01-01

    Nitride semiconductors are attractive because they can be environmentally benign, comprised of abundant elements and possess favourable electronic properties. However, those currently commercialized are mostly limited to gallium nitride and its alloys, despite the rich composition space of nitrides. Here we report the screening of ternary zinc nitride semiconductors using first-principles calculations of electronic structure, stability and dopability. This approach identifies as-yet-unreporte...

  11. Plasmonic titanium nitride nanostructures for perfect absorbers

    DEFF Research Database (Denmark)

    Guler, Urcan; Li, Wen-Wei; Kinsey, Nathaniel

    2013-01-01

    We propose a metamaterial based perfect absorber in the visible region, and investigate the performance of titanium nitride as an alternative plasmonic material. Numerical and experimental results reveal that titanium nitride performs better than gold as a plasmonic absorbing material...

  12. Electro-optic and magneto-dielectric properties of multifunctional nitride and oxide materials

    Science.gov (United States)

    Dixit, Ambesh

    Materials that simultaneously exhibit different physical properties provide a rich area of research leading to the development of new devices. For example, materials having a strong coupling between charge and spin degrees of freedom are essential to realizing a new class of devices referred to generally as spintronics. However, these multifunctional systems pose new scientific challenges in understanding the origin and mechanisms for cross-control of different functionalities. The core of this Ph.D. dissertation deals with multifunctional nitride and oxide compound semiconductors as well as multiferroic magnetic oxide systems by investigating structural, optical, electrical, magnetic, magnetodielectric and magnetoelectric properties. Thin films of InN nitride compound semiconductors and closely related alloys have been investigated to understand the effects of intrinsic defects on the materials properties while considering possible applications of highly degenerate InN thin films. As grown rf sputtered InN films on c-axis (0001) sapphire exhibit highly degenerate n-type behaviour due to oxygen defects introduced during growth. The effect of oxygen in InN matrix has been further investigated by intentionally adding oxygen into the films. These studies confirm that oxygen is one of the main sources of donor electrons in degenerate InN. Above some critical concentration of oxygen, secondary phases of In 2O3 and In-O-N complexes were formed. It was also possible to tune the carrier concentration to produce changes in the plasmon frequency, which varied from 0.45 eV to 0.8 eV. This characteristic energy scale suggests that these highly degenerate InN thin films could be used for thermophotovoltaic cells, optical filters, and other IR electro-optic applications. To probe the magnetism in transition metal doped InN system, In 0.98Cr0.02N and In0.95Cr0.05N thin films were fabricated. Our results suggest that these films develop ferromagnetic order above room temperature

  13. Growth process for gallium nitride porous nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Wildeson, Isaac Harshman; Sands, Timothy David

    2015-03-24

    A GaN nanorod and formation method. Formation includes providing a substrate having a GaN film, depositing SiN.sub.x on the GaN film, etching a growth opening through the SiN.sub.x and into the GaN film, growing a GaN nanorod through the growth opening, the nanorod having a nanopore running substantially through its centerline. Focused ion beam etching can be used. The growing can be done using organometallic vapor phase epitaxy. The nanopore diameter can be controlled using the growth opening diameter or the growing step duration. The GaN nanorods can be removed from the substrate. The SiN.sub.x layer can be removed after the growing step. A SiO.sub.x template can be formed on the GaN film and the GaN can be grown to cover the SiO.sub.x template before depositing SiN.sub.x on the GaN film. The SiO.sub.x template can be removed after growing the nanorods.

  14. Technology of gallium nitride crystal growth

    CERN Document Server

    Ehrentraut, Dirk; Bockowski, Michal

    2010-01-01

    This book deals with the important technological aspects of the growth of GaN single crystals by HVPE, MOCVD, ammonothermal and flux methods for the purpose of free-standing GaN wafer production. Leading experts from industry and academia report in a very comprehensive way on the current state-of-the-art of the growth technologies and optical and structural properties of the GaN crystals are compared.

  15. Tungsten nitride coatings obtained by HiPIMS as plasma facing materials for fusion applications

    Czech Academy of Sciences Publication Activity Database

    Tiron, V.; Velicu, I. L.; Porosnicu, C.; Burducea, I.; Dinca, P.; Malinský, Petr

    2017-01-01

    Roč. 416, SEP (2017), s. 878-884 ISSN 0169-4332 R&D Projects: GA ČR(CZ) GBP108/12/G108; GA MŠk LM2015056 Institutional support: RVO:61389005 Keywords : Tugensten nitride layers * m-HIPIMS * deuterium retention * deuterium plasma jet * thermal desorption spectrometry Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders OBOR OECD: Nuclear physics Impact factor: 3.387, year: 2016

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

    Science.gov (United States)

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

    2016-11-22

    Correction for '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' by James P. Dombrowski et al., Dalton Trans., 2016, 45, 11025-11034.

  17. Molecular coatings of nitride semiconductors for optoelectronics, electronics, and solar energy harvesting

    KAUST Repository

    Ng, Tien Khee

    2018-02-01

    Gallium nitride based semiconductors are provided having one or more passivated surfaces. The surfaces can have a plurality of thiol compounds attached thereto for enhancement of optoelectronic properties and/or solar water splitting properties. The surfaces can also include wherein the surface has been treated with chemical solution for native oxide removal and / or wherein the surface has attached thereto a plurality of nitrides, oxides, insulating compounds, thiol compounds, or a combination thereof to create a treated surface for enhancement of optoelectronic properties and / or solar water splitting properties. Methods of making the gallium nitride based semiconductors are also provided. Methods can include cleaning a native surface of a gallium nitride semiconductor to produce a cleaned surface, etching the cleaned surface to remove oxide layers on the surface, and applying single or multiple coatings of nitrides, oxides, insulating compounds, thiol compounds, or a combination thereof attached to the surface.

  18. Cubic boron nitride (cBN) - A new material for advanced optoelectronic devices. Properties and perspectives

    International Nuclear Information System (INIS)

    Nistor, S.V.; Nistor, L.C.; Dinca, G.

    2001-01-01

    Cubic boron nitride (cBN) exhibits, besides exceptional thermal and mechanical properties similar to diamond, an excellent ability to be n or p doped, which makes it a strong candidate for advanced, high - temperature optical and microelectronic devices. Despite its outstanding characteristics, there are quite a few reports concerning the physical properties of cBN. This is partly due to the absence of natural cBN gems and the extreme difficulties in producing enough large (mm 3 sized) single crystals, or single phase thin films, for physical characterization. The state of the art knowledge concerning the basic properties of crystalline cBN, as well as our recent results of microstructure and defect properties studies will be presented. (authors)

  19. Gallium beam lithography for superconductive structure formation

    Energy Technology Data Exchange (ETDEWEB)

    Henry, Michael David; Lewis, Rupert M.

    2018-01-30

    The present invention relates to the use of gallium beam lithography to form superconductive structures. Generally, the method includes exposing a surface to gallium to form an implanted region and then removing material adjacent to and/or below that implanted region. In particular embodiments, the methods herein provide microstructures and nanostructures in any useful substrate, such as those including niobium, tantalum, tungsten, or titanium.

  20. Fluorimetric analysis of gallium in bauxite, by-products, products from gallium processing and its control solutions

    International Nuclear Information System (INIS)

    Ferreira, C.A.M.; Medeiros, V.

    1987-01-01

    The gallium processing since raw material analysis until end-products analysis is studied. Gallium presence in by-products and products, as well as the fluorimetric method is analyzed. Equipments and materials used in laboratory, reagents and chemical solutions are described. (M.J.C.) [pt

  1. Hard template synthesis of porous carbon nitride materials with improved efficiency for photocatalytic CO{sub 2} utilization

    Energy Technology Data Exchange (ETDEWEB)

    Ovcharov, M. [L.V Pysarzhevsky Institute of Physical Chemistry, NAS of Ukraine, 31 pr. Nauky, 03028 Kyiv (Ukraine); Shcherban, N., E-mail: nataliyalisenko@ukr.net [L.V Pysarzhevsky Institute of Physical Chemistry, NAS of Ukraine, 31 pr. Nauky, 03028 Kyiv (Ukraine); Filonenko, S.; Mishura, A. [L.V Pysarzhevsky Institute of Physical Chemistry, NAS of Ukraine, 31 pr. Nauky, 03028 Kyiv (Ukraine); Skoryk, M. [NanoMedTech LLC, 68 Gorkogo str., Kyiv (Ukraine); Shvalagin, V.; Granchak, V. [L.V Pysarzhevsky Institute of Physical Chemistry, NAS of Ukraine, 31 pr. Nauky, 03028 Kyiv (Ukraine)

    2015-12-15

    Graphical abstract: - Highlights: • Porous carbon nitrides were obtained via bulk and matrix pyrolysis of melamine. • Carbon nitride obtained in MCF has the highest bandgap and photocatalytic activity. • Acetaldehyde was the major product of the photoreduction reaction of CO2. - Abstract: Porous carbon nitrides of different morphology were obtained via bulk and hard template (SBA-15 and MCF) pyrolysis of melamine. Matrix method allowed obtaining ordered porous C{sub 3}N{sub 4} with higher bandgap (2.87 eV) in the contrary to the bulk sample (2.45 eV). Obtained carbon nitrides were found to be p-type semiconductors with catalytic activity towards photoreduction of carbon dioxide with water vapour. Carbon nitride obtained in MCF has the higher bandgap, developed surface, sponge-like morphology, spatially ordering and it's characterized by the highest photocatalytic activity.

  2. Gallium-cladding compatibility testing plan. Phases 1 and 2: Test plan for gallium corrosion tests. Revision 2

    International Nuclear Information System (INIS)

    Wilson, D.F.; Morris, R.N.

    1998-05-01

    This test plan is a Level-2 document as defined in the Fissile Materials Disposition Program Light-Water-Reactor Mixed-Oxide Fuel Irradiation Test Project Plan. The plan summarizes and updates the projected Phases 1 and 2 Gallium-Cladding compatibility corrosion testing and the following post-test examination. This work will characterize the reactions and changes, if any, in mechanical properties that occur between Zircaloy clad and gallium or gallium oxide in the temperature range 30--700 C

  3. Investigations in gallium removal

    International Nuclear Information System (INIS)

    Philip, C.V.; Pitt, W.W.; Beard, C.A.

    1997-11-01

    Gallium present in weapons plutonium must be removed before it can be used for the production of mixed-oxide (MOX) nuclear reactor fuel. The main goal of the preliminary studies conducted at Texas A and M University was to assist in the development of a thermal process to remove gallium from a gallium oxide/plutonium oxide matrix. This effort is being conducted in close consultation with the Los Alamos National Laboratory (LANL) personnel involved in the development of this process for the US Department of Energy (DOE). Simple experiments were performed on gallium oxide, and cerium-oxide/gallium-oxide mixtures, heated to temperatures ranging from 700--900 C in a reducing environment, and a method for collecting the gallium vapors under these conditions was demonstrated

  4. Investigations in gallium removal

    Energy Technology Data Exchange (ETDEWEB)

    Philip, C.V.; Pitt, W.W. [Texas A and M Univ., College Station, TX (United States); Beard, C.A. [Amarillo National Resource Center for Plutonium, TX (United States)

    1997-11-01

    Gallium present in weapons plutonium must be removed before it can be used for the production of mixed-oxide (MOX) nuclear reactor fuel. The main goal of the preliminary studies conducted at Texas A and M University was to assist in the development of a thermal process to remove gallium from a gallium oxide/plutonium oxide matrix. This effort is being conducted in close consultation with the Los Alamos National Laboratory (LANL) personnel involved in the development of this process for the US Department of Energy (DOE). Simple experiments were performed on gallium oxide, and cerium-oxide/gallium-oxide mixtures, heated to temperatures ranging from 700--900 C in a reducing environment, and a method for collecting the gallium vapors under these conditions was demonstrated.

  5. Fiscal Year 2011 Director’s Strategic Initiative Final Report Heterogeneous Device Architectures Incorporating Nitride Semiconductors for Enhanced Functionality of Optoelectronic Devices

    Science.gov (United States)

    2014-03-01

    from the UV (200 nm) to the IR (1800 nm) by varying the alloy composition from aluminum nitride (AlN) (6.1 eV) to 2 gallium nitride (GaN) (3.4 eV...the significantly larger breakdown field of AlN over SiC (approximately 6 times) implies that aluminum gallium nitride (AlGaN)-based deep UV (DUV...challenges that are unlike traditional heterojunction APDs such as indium gallium arsenide /indium phosphorous (InGaAs/InP) telecommunications devices

  6. The Effect of Radiation on the Electrical Properties of Aluminum Gallium Nitride/Gallium Nitride Heterostructures

    National Research Council Canada - National Science Library

    McClory, John W

    2008-01-01

    AlGaN/GaN Heterojunction Field Effect Transistors (HFETs) were irradiated at low temperature and the temperature dependent changes to drain current, gate current, capacitance, and transconductance were measured...

  7. Two-Dimensional Modeling of Aluminum Gallium Nitride/Gallium Nitride High Electron Mobility Transistor

    National Research Council Canada - National Science Library

    Holmes, Kenneth

    2002-01-01

    .... This thesis studies the effects of AIGaN/GaN HEMTs' polarization, piezoelectric (PZ) and spontaneous, properties utilizing the TM commercially available Silvaco Atlas software for modeling and simulation...

  8. Technical Progress Report for "Optical and Electrical Properties of III-Nitrides and Related Materials"

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Hongxing

    2008-10-31

    Investigations have been conducted focused on the fundamental material properties of AIN and high AI-content AIGaN alloys and further developed MOCVD growth technologies for obtaining these materials with improved crystalline quality and conductivities.

  9. Strength and microstructure of gallium alloys.

    Science.gov (United States)

    Miller, B H; Woldu, M; Nakajima, H; Okabe, T

    1999-03-01

    This study investigated the physical and mechanical properties and the microstructure of four different gallium alloys. For all gallium alloys, the compressive strengths measured at one hour (86-223 MPa) and 24 hours (265-286 MPa) after specimen preparation were found to be well within the range exhibited by many high-copper amalgams. The creep values and dimensional change of the gallium alloys were comparable to those of leading amalgams, except for the dimensional change value of one alloy. The set gallium alloys consisted of a multi-phase structure including beta-Sn, CuGa2, In4Ag9, Ag72Ga28, and Ga5Pd (except for one product that did not contain Pd) that was more complicated than the structure of dental amalgams. Although the gallium alloys had physical and mechanical properties comparable to those of high-copper amalgams, the microstructure, coupled with the instability of the element gallium itself, could make these materials more prone to corrosive attack compared to amalgams.

  10. Interactions of Zircaloy cladding with gallium: 1998 midyear status

    International Nuclear Information System (INIS)

    Wilson, D.F.; DiStefano, J.R.; Strizak, J.P.; King, J.F.; Manneschmidt, E.T.

    1998-06-01

    A program has been implemented to evaluate the effect of gallium in mixed-oxide (MOX) fuel derived from weapons-grade (WG) plutonium on Zircaloy cladding performance. The objective is to demonstrate that low levels of gallium will not compromise the performance of the MOX fuel system in a light-water reactor. The graded, four-phase experimental program was designed to evaluate the performance of prototypic Zircaloy cladding materials against (1) liquid gallium (Phase 1), (2) various concentrations of Ga 2 O 3 (Phase 2), (3) centrally heated surrogate fuel pellets with expected levels of gallium (Phase 3), and (4) centrally heated prototypic MOX fuel pellets (Phase 4). This status report describes the results of a series of tests for Phases 1 and 2. Three types of tests are being performed: (1) corrosion, (2) liquid metal embrittlement, and (3) corrosion-mechanical. These tests will determine corrosion mechanisms, thresholds for temperature and concentration of gallium that may delineate behavioral regimes, and changes in the mechanical properties of Zircaloy. Initial results have generally been favorable for the use of WG-MOX fuel. The MOX fuel cladding, Zircaloy, does react with gallium to form intermetallic compounds at ≥300 C; however, this reaction is limited by the mass of gallium and is therefore not expected to be significant with a low level (parts per million) of gallium in the MOX fuel. Although continued migration of gallium into the initially formed intermetallic compound can result in large stresses that may lead to distortion, this was shown to be extremely unlikely because of the low mass of gallium or gallium oxide present and expected clad temperatures below 400 C. Furthermore, no evidence for grain boundary penetration by gallium has been observed

  11. Interface Characterization of Metals and Metal-nitrides to Phase Change Materials

    NARCIS (Netherlands)

    Roy, Deepu; Gravesteijn, Dirk J; Wolters, Robertus A.M.

    2011-01-01

    We have investigated the interfacial contact properties of the CMOS compatible electrode materials W, TiW, Ta, TaN and TiN to doped-Sb2Te phase change material (PCM). This interface is characterized both in the amorphous and in the crystalline state of the doped-Sb2Te. The electrical nature of the

  12. Graphitic Carbon Nitride Supported Catalysts for Polymer Electrolyte Fuel Cells.

    OpenAIRE

    Mansor, N.; Jorge, A. B.; Corà, F.; Gibbs, C.; Jervis, R.; McMillan, P. F.; Wang, X.; Brett, D. J.

    2014-01-01

    Graphitic carbon nitrides are investigated for developing highly durable Pt electrocatalyst supports for polymer electrolyte fuel cells (PEFCs). Three different graphitic carbon nitride materials were synthesized with the aim to address the effect of crystallinity, porosity, and composition on the catalyst support properties: polymeric carbon nitride (gCNM), poly(triazine) imide carbon nitride (PTI/Li(+)Cl(-)), and boron-doped graphitic carbon nitride (B-gCNM). Following accelerated corrosion...

  13. Energy transfer phenomena and radiative processes in silicon nitride based materials for on-chip photonics applications

    Science.gov (United States)

    Li, Rui

    Rare-earth (RE) doping of silicon-based structures provides a valuable approach for light-emitting devices which could be monolithically integrated atop the widespread silicon electronics platform and enables inexpensive integration of on-chip optical components. However, the small excitable fraction of RE ions and the substantial free carrier losses in Si nanostructures severely limit the possibility to achieve net optical gain using traditional Er doped materials, such as Er doped Si-rich oxides (Er:SRO). On the other hand, a novel material platform based on RE-doped silicon nitride (RE:Six) materials has recently revealed unique advantages for on-chip light source. Based on a variety of light emission spectroscopic techniques and rate equation modeling, light emission and energy transfer phenomena were studied to quantitatively assess the benefits of the novel Er and Nd doped SiNx (Er: SiN x and Nd:SiNx) material platform compared to the standard Er:SRO. Efficient energy transfer and nanosecond-time dynamics from SiN x matrices to RE ions with two orders of magnitude larger coupling coefficient than Er:SRO were demonstrated for the first time. The origin of this energy transfer was shown to consist of non-resonant phonon-mediated coupling by temperature-dependent experiments. In addition, a tradeoff between excitation efficiency by energy transfer and emission efficiency, determined by excess Si concentration, was discovered and studied. Although carrier absorption and non-radiative recombination jeopardize the observation of optical gain, differential loss measurements under femtosecond pulsed excitation resulted in the bleaching of the Er ground state absorption by energy transfer in Er:SiN x materials, which bears great hope for the engineering of Si-based lasers. On the other hand, with a superior 4-level system, Nd:SiNx is promising to lase with a lower threshold. To make use of the better field confinement in SiNx due to its higher refractive index, RE

  14. Plasma-assisted atomic layer epitaxial growth of aluminum nitride studied with real time grazing angle small angle x-ray scattering

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Virginia R.; Nepal, Neeraj; Johnson, Scooter D.; Robinson, Zachary R.; Nath, Anindya; Kozen, Alexander C.; Qadri, Syed B.; DeMasi, Alexander; Hite, Jennifer K.; Ludwig, Karl F.; Eddy, Charles R.

    2017-05-01

    Wide bandgap semiconducting nitrides have found wide-spread application as light emitting and laser diodes and are under investigation for further application in optoelectronics, photovoltaics, and efficient power switching technologies. Alloys of the binary semiconductors allow adjustments of the band gap, an important semiconductor material characteristic, which is 6.2 eV for aluminum nitride (AlN), 3.4 eV for gallium nitride, and 0.7 eV for (InN). Currently, the highest quality III-nitride films are deposited by metalorganic chemical vapor deposition and molecular beam epitaxy. Temperatures of 900 °C and higher are required to deposit high quality AlN. Research into depositing III-nitrides with atomic layer epitaxy (ALEp) is ongoing because it is a fabrication friendly technique allowing lower growth temperatures. Because it is a relatively new technique, there is insufficient understanding of the ALEp growth mechanism which will be essential to development of the process. Here, grazing incidence small angle x-ray scattering is employed to observe the evolving behavior of the surface morphology during growth of AlN by ALEp at temperatures from 360 to 480 °C. Increased temperatures of AlN resulted in lower impurities and relatively fewer features with short range correlations.

  15. Effects of erbium-and chromium-doped yttrium scandium gallium garnet and diode lasers on the surfaces of restorative dental materials: a scanning electron microscope study.

    Science.gov (United States)

    Hatipoglu, M; Barutcigil, C

    2015-01-01

    The aim of this study is to evaluate the potential effects of laser irradiation, which is commonly performed in periodontal surgery, on the surfaces of restorative materials. Five different restorative dental materials were used in this study, as follows: (1) Resin composite, (2) poly acid-modified resin composite (compomer), (3) conventional glass ionomer cement (GIC), (4) resin-modified glass ionomer cement (RMGIC), and (5) amalgam. Four cylindrical samples (8 mm diameter, 2 mm height) were prepared for each restorative material. In addition, four freshly extracted, sound human incisors teeth were selected. Two different laser systems commonly used in periodontal surgery were examined in this study: A 810 nm diode laser at a setting of 1 W with continuous-phase laser irradiation for 10 s, and an erbium-and chromium-doped yttrium scandium gallium garnet (Er, Cr: YSGG) laser at settings of 2.5 W, 3.25 W, and 4 W with 25 Hz laser irradiation for 10 s. Scanning electron microscopy (SEM) analysis was performed to evaluate the morphology and surface deformation of the restorative materials and tooth surfaces. According to the SEM images, the Er, Cr: YSGG laser causes irradiation markings that appear as demineralized surfaces on tooth samples. The Er, Cr: YSGG laser also caused deep defects on composite, compomer, and RMGIC surfaces because of its high power, and the ablation was deeper for these samples. High-magnification SEM images of GIC samples showed the melting and combustion effects of the Er, Cr: YSGG laser, which increased as the laser power was increased. In amalgam samples, neither laser left significant harmful effects at the lowest power setting. The diode laser did cause irradiation markings, but they were insignificant compared with those left by the Er, Cr: YSGG laser on the surfaces of the different materials and teeth. Within the limitations of this study, it can be concluded that Er, Cr: YSGG laser irradiation could cause distortions of the surfaces

  16. Thermally conductive tough flexible elastomers as composite of slide-ring materials and surface modified boron nitride particles via plasma in solution

    Science.gov (United States)

    Goto, Taku; Iida, Masaki; Tan, Helen; Liu, Chang; Mayumi, Koichi; Maeda, Rina; Kitahara, Koichi; Hatakeyama, Kazuto; Ito, Tsuyohito; Shimizu, Yoshiki; Yokoyama, Hideaki; Kimura, Kaoru; Ito, Kohzo; Hakuta, Yukiya; Terashima, Kazuo

    2018-03-01

    We have developed a thermally conductive flexible elastomer as a composite material with slide-ring (SR) materials and boron nitride (BN) particles surface-modified via plasma in solution. This composite shows excellent properties as a flexible insulator for thermal management. Surface modification of BN particles using plasma in solution increases the tensile strength, extension ratio at break, toughness, and rubber characteristics of the composites, compared to SR and non-modified BN, while the Young's modulus values are identical. Furthermore, the thermal conductivity also improved as a result of plasma surface modification.

  17. Novel nitrogen/gallium precursor [Ga(bdma)H2] for MOVPE

    Science.gov (United States)

    Sterzer, E.; Beyer, A.; Nattermann, L.; Schorn, W.; Schlechter, K.; Pulz, S.; Sundermeyer, J.; Stolz, W.; Volz, K.

    2016-11-01

    Dilute nitrogen (N) containing III/V semiconductors are promising candidates for solar cell and laser applications. The N incorporation efficiency of 1,1-dimethylhydrazine (UMDHy) in metal organic vapor phase epitaxy (MOVPE), however, happens to be only in the one percentage range and below. This leads to an extremely high offer of UDMHy in the MOVPE reactor and, therefore, a drastic change in the growth conditions. Furthermore, the device efficiency of dilute nitride materials is currently hampered by carbon (C) incorporation, which is believed to be incorporated either jointly with the N from the dimethylamine radical of the UMDHy or from short hydrocarbon radicals originating from the decomposition of the other metal organics. Therefore, this work presents a novel N precursor N,N'-Bis(dimethylamino)acetamidinato-galliumdihydride [Ga(bdma)H2], which provides not only N but also gallium (Ga) during MOVPE. The direct N-Ga bond in this molecule might facilitate the N incorporation and hence increase the efficiency. For a systematic N incorporation study Ga(NAs)/GaAs heterostructures were grown by MOVPE. The N content was determined via high resolution X-ray diffraction and photoluminescence (PL) studies. Good structural quality and as grown room temperature PL were obtained. It will be also shown that the N incorporation efficiency in GaAs using [Ga(bdma)H2] is significantly higher than for growths using UDMHy under comparable conditions, making this class of molecules promising candidates for the growth of dilute nitride materials.

  18. Ion nitridation - physical and technological aspects

    International Nuclear Information System (INIS)

    Elbern, A.W.

    1980-01-01

    Ion nitridation, is a technique which allows the formation of a controlled thickness of nitrides in the surface of the material, using this material as the cathode in a low pressure glow discharge, which presents many advantages over the conventional method. A brief review of the ion nitriding technique, the physical fenomena involved, and we discuss technological aspects of this method, are presented. (Author) [pt

  19. Lung gallium scan

    Science.gov (United States)

    ... produced by the gallium. Images display on a computer screen. During the scan, it is important that ... M. is also a founding member of Hi-Ethics and subscribes to the principles of the Health ...

  20. EDITORIAL: Non-polar and semipolar nitride semiconductors Non-polar and semipolar nitride semiconductors

    Science.gov (United States)

    Han, Jung; Kneissl, Michael

    2012-02-01

    topics including growth and heteroepitaxy, bulk GaN substrates, theory and modelling, optical properties, laser diodes and LEDs as well as transport properties and electronics. Farrell et al review materials and growth issues for high-performance non- and semipolar light-emitting devices, and Scholz provides an overview of heteroepitaxial growth of semipolar GaN. Okada et al review growth mechanisms of non- and semipolar GaN layers on patterned sapphire substrates, and Vennéguès discusses defect reduction methods for heteroepitaxially grown non- and semipolar III-nitride films. Leung et al explain how kinetic Wulff plots can be used to design and control non-polar and semipolar GaN heteroepitaxy, and a contribution by Sawaki et al explores the impurity incorporation in (1-101) GaN grown on Si substrates. In the area of bulk crystal growth Kucharski et al review non- and semipolar GaN substrates by ammonothermal growth, and Chichibu et al discuss the challenges for epitaxial growth of InGaN on free-standing m-plane GaN substrates. Calculation of semipolar orientations for wurtzitic semiconductor heterostructures and their application to nitrides and oxides are reviewed by Bigenwald et al, and Ito et al present an ab initio approach to reconstruction, adsorption, and incorporation on GaN surfaces. Finally, the theoretical description of non-polar and semipolar nitride semiconductor quantum-well structures is presented by Ahn et al. In a discussion of the optical properties, Kisin et al discuss the effect of the quantum well population on the optical characteristics of polar, semipolar and non-polar III-nitride light emitters, and Jönen et al investigate the indium incorporation and optical properties of non- and semipolar GaInN QW structures. Wernicke et al explore the emission wavelength of polar, non-polar, and semipolar InGaN quantum wells and the incorporation of indium. In a contribution by Melo et al, the gain in polar and non-polar/semipolar gallium-nitride

  1. Effect of Variation of Silicon Nitride Passivation Layer on Electron Irradiated Aluminum Gallium Nitride/Gallium Nitride HEMT Structures

    Science.gov (United States)

    2014-06-19

    1.071 x 1013 , ↓ 24% 1.425 ↓ 57% 200E0 200 200 Å 0 1547 1.42x 1013 3.5 200E1 200 200 Å 1016 cm-2 695 ↓ 55% 1.23 x 1013 .865 ↓ 75% 500E0...Klein, P. B., and Kazior, T. E.. “Trapping effects in GaN and SiC microwave FETs.” Proceedings of the IEEE , 90, no. 6 (2002): 1048-1058. Borchi, E...34 IEEE 252 Transactions on Nuclear Science, 46, no. 4 (1999): 834. Calleja, E., Sánchez, F. J., Basak, D., Sánchez-García, M. A., Muñoz, E

  2. Nuclear microprobe imaging of gallium nitrate in cancer cells

    International Nuclear Information System (INIS)

    Ortega, Richard; Suda, Asami; Deves, Guillaume

    2003-01-01

    Gallium nitrate is used in clinical oncology as treatment for hypercalcemia and for cancer that has spread to the bone. Its mechanism of antitumor action has not been fully elucidated yet. The knowledge of the intracellular distribution of anticancer drugs is of particular interest in oncology to better understand their cellular pharmacology. In addition, most metal-based anticancer compounds interact with endogenous trace elements in cells, altering their metabolism. The purpose of this experiment was to examine, by use of nuclear microprobe analysis, the cellular distribution of gallium and endogenous trace elements within cancer cells exposed to gallium nitrate. In a majority of cellular analyses, gallium was found homogeneously distributed in cells following the distribution of carbon. In a smaller number of cells, however, gallium appeared concentrated together with P, Ca and Fe within round structures of about 2-5 μm diameter located in the perinuclear region. These intracellular structures are typical of lysosomial material

  3. Designing nanoscale constructs from atomic thin sheets of graphene, boron nitride and gold nanoparticles for advanced material applications

    Science.gov (United States)

    Jasuja, Kabeer

    2011-12-01

    Nanoscale materials invite immense interest from diverse scientific disciplines as these provide access to precisely understand the physical world at their most fundamental atomic level. In concert with this aim of enhancing our understanding of the fundamental behavior at nanoscale, this dissertation presents research on three nanomaterials: Gold nanoparticles (GNPs), Graphene and ultra-thin Boron Nitride sheets (UTBNSs). The three-fold goals which drive this research are: incorporating mobility in nanoparticle based single-electron junction constructs, developing effective strategies to functionalize graphene with nano-forms of metal, and exfoliating ultrathin sheets of Boron Nitride. Gold nanoparticle based electronic constructs can achieve a new degree of operational freedom if nanoscale mobility is incorporated in their design. We achieved such a nano-electromechanical construct by incorporating elastic polymer molecules between GNPs to form 2-dimensional (2-D) molecular junctions which show a nanoscale reversible motion on applying macro scale forces. This GNP-polymer assembly works like a molecular spring opening avenues to maneuver nano components and store energy at nano-scale. Graphene is the first isolated nanomaterial that displays single-atom thickness. It exhibits quantum confinement that enables it to possess a unique combination of fascinating electronic, optical, and mechanical properties. Modifying the surface of graphene is extremely significant to enable its incorporation into applications of interest. We demonstrated the ability of chemically modified graphene sheets to act as GNP stabilizing templates in solution, and utilized this to process GNP composites of graphene. We discovered that GNPs synthesized by chemical or microwave reduction stabilize on graphene-oxide sheets to form snow-flake morphologies and bare-surfaces respectively. These hybrid nano constructs were extensively studied to understand the effect and nature of GNPs

  4. Development of On-Demand Non-Polar and Semi-Polar Bulk Gallium Nitride Materials for Next Generation Electronic and Optoelectrode Devices

    National Research Council Canada - National Science Library

    Fini, P

    2007-01-01

    ...) wafers that will act as seeds for subsequent GaN boule growth in Phase II. Inlustra developed non-polar a-plane and m-plane GaN films with smooth surfaces and minimal wafer bowing and cracking...

  5. 1997 IEEE/LEOS Summer Topical Meeting on Gallium Nitride Materials, Processing and Devices Held in Montreal, Quebec, Canada on 11-15 August 1997

    Science.gov (United States)

    1998-01-01

    Tetu Centre d’Optique, Photonique et Laser Departement de Genie Electrique et de Genie Informatique, Universite LAVAL Ste-Foy, Qc, G1K 7P4, Canada...Leslie Ann Rusch, Michel Tetu Centre d’Optique, Photonique et Lasers (COPL) Departement de Genie Electrique et de Genie Informatique Universite...that the dark spots spread out, forming a triangular dark region composed of dislocation dipoles and loops. The dipoles are closely aligned to the

  6. Spectroscopic investigations of plasma nitriding processes: A comparative study using steel and carbon as active screen materials

    Science.gov (United States)

    Hamann, S.; Burlacov, I.; Spies, H.-J.; Biermann, H.; Röpcke, J.

    2017-04-01

    Low-pressure pulsed DC H2-N2 plasmas were investigated in the laboratory active screen plasma nitriding monitoring reactor, PLANIMOR, to compare the usage of two different active screen electrodes: (i) a steel screen with the additional usage of CH4 as carbon containing precursor in the feeding gas and (ii) a carbon screen without the usage of any additional gaseous carbon precursor. Applying the quantum cascade laser absorption spectroscopy, the evolution of the concentration of four stable molecular species, NH3, HCN, CH4, and C2H2, has been monitored. The concentrations were found to be in a range of 1012-1016 molecules cm-3. By analyzing the development of the molecular concentrations at variations of the screen plasma power, a similar behavior of the monitored reaction products has been found for both screen materials, with NH3 and HCN as the main reaction products. When using the carbon screen, the concentration of HCN and C2H2 was 30 and 70 times higher, respectively, compared to the usage of the steel screen with an admixture of 1% CH4. Considering the concentration of the three detected hydrocarbon reaction products, a combustion rate of the carbon screen of up to 69 mg h-1 has been found. The applied optical emission spectroscopy enabled the determination of the rotational temperature of the N2+ ion which has been in a range of 650-900 K increasing with the power in a similar way in the plasma of both screens. Also with power the ionic component of nitrogen molecules, represented by the N2+ (0-0) band of the first negative system, as well as the CN (0-0) band of the violet system increase strongly in relation to the intensity of the neutral nitrogen component, i.e., the N2 (0-0) band of the second positive system. In addition, steel samples have been treated with both the steel and the carbon screen resulting in a formation of a compound layer of up to 10 wt. % nitrogen and 10 wt. % carbon, respectively, depending on the screen material.

  7. Optical Parametric Oscillation in Orientation-Patterned Gallium Arsenide

    National Research Council Canada - National Science Library

    Shell, Scott A

    2007-01-01

    .... Orientation patterned gallium arsenide (OPGaAs) is a promising nonlinear conversion material because it has broad transparency and can be engineered for specific pump laser and output wavelengths using quasi-phase matching techniques...

  8. Optical Characterization of Thick Growth Orientation-Patterned Gallium Arsenide

    National Research Council Canada - National Science Library

    Meyer, Joshua W

    2006-01-01

    .... Orientation patterned gallium arsenide (OPGaAs) is a promising nonlinear conversion material because it has broad transparency and can be engineered for specific pump laser and output wavelengths using quasi-phase matching techniques...

  9. Electrodeposition of gallium for photovoltaics

    Science.gov (United States)

    Bhattacharya, Raghu N.

    2016-08-09

    An electroplating solution and method for producing an electroplating solution containing a gallium salt, an ionic compound and a solvent that results in a gallium thin film that can be deposited on a substrate.

  10. Gallium-containing conducting metallopolymers which display chemically tunable reactivity for the growth of Ga2S3 semiconducting nanoparticles.

    Science.gov (United States)

    Mejía, Michelle L; Reeske, Gregor; Holliday, Bradley J

    2010-08-07

    Electropolymerization of novel gallium Schiff-base complexes results in conducting metallopolymers containing either coordinatively saturated or unsaturated gallium metal centers. Depending on the chemical coordination of the metal centers, the embedded metal ions can act as seed points for the direct growth of size-controlled gallium sulfide nanoparticles in a conducting polymer, yielding a hybrid electronic material.

  11. Gallium scintigraphy in AIDS

    International Nuclear Information System (INIS)

    Van der Wall, Hans; Provan, I.; Murray, C.; Dwyer, M.; Jones, P.D.

    1990-01-01

    Gallium-67 scanning, indicated either for the elucidation of symptoms or for the assessment of appropriate therapy, was performed in 56 AIDS patients who underwent a total of 77 scans from 1986 to 1988. The age range of the patients was 13-66 years with an average age of 39 years. The majority of patients (95%) were male homosexuals. Gallium scanning has been applied to a wide spectrum of malignancies and to the detection of occult infections. Several mechanisms of uptake have been postulated for the localization of gallium. In general, gallium-67 acts as an analogue of the ferric ion, binding to transferrin soon after intravenous injection. It is believed that it is bound to transferrin receptors on the surface of tumour cells with subsequent intracellular transport. In infection, the association is probably with lactoferrin elaborated by polymorphonuclear cells and siderophores elaborated by bacteria. Gallium-67 is normally distributed to bone and bone marrow, liver, spleen, breast and bowel. In particular, the concentration in the ascending and transverse colon necessitates adequate bowel preparation. Lacrimal, nasopharyngeal and genital activity may also be seen. 11 refs., 2 tabs., 6 figs

  12. Light-induced degradation in copper-contaminated gallium-doped silicon

    OpenAIRE

    Lindroos, Jeanette; Yli-Koski, Marko; Haarahiltunen, Antti; Schubert, Martin C.; Savin, Hele

    2013-01-01

    To date, gallium-doped Czochralski (Cz) silicon has constituted a solar cell bulk material free of light-induced degradation. However, we measure light-induced degradation in gallium-doped Cz silicon in the presence of copper impurities. The measured degradation depends on the copper concentration and the material resistivity. Gallium-doped Cz silicon is found to be less sensitive to copper impurities than borondoped Cz silicon, emphasizing the role of boron in the formation of copper-related...

  13. Elastic strain relief in nitridated Ga metal buffer layers for epitaxial GaN growth

    International Nuclear Information System (INIS)

    Kim, Yihwan; Shapiro, Noad A.; Feick, Henning; Armitage, Robert; Weber, Eicke R.; Yang, Yi; Cerrina, Franco

    2001-01-01

    Gallium nitride epitaxial layers were grown on sapphire by molecular-beam epitaxy using nitridated gallium metal films as buffer layers. The mechanical properties of the buffer layers were investigated and correlated with their chemical composition as determined by synchrotron radiation photoelectron spectroscopy. Biaxial tension experiments were performed by bending the substrates in a pressure cell designed for simultaneous photoluminescence measurements. The shift of the excitonic luminescence peak was used to determine the stress induced in the main GaN epilayer. The fraction of stress transferred from substrate to main layer was as low as 27% for samples grown on nitridated metal buffer layers, compared to nearly 100% for samples on conventional low-temperature GaN buffer layers. The efficiency of stress relief increased in proportion to the fraction of metallic Ga in the nitridated metal buffer layers. These findings suggest GaN films containing residual metallic Ga may serve as compliant buffer layers for heteroepitaxy

  14. Nitride alloy layer formation of duplex stainless steel using nitriding process

    Science.gov (United States)

    Maleque, M. A.; Lailatul, P. H.; Fathaen, A. A.; Norinsan, K.; Haider, J.

    2018-01-01

    Duplex stainless steel (DSS) shows a good corrosion resistance as well as the mechanical properties. However, DSS performance decrease as it works under aggressive environment and at high temperature. At the mentioned environment, the DSS become susceptible to wear failure. Surface modification is the favourable technique to widen the application of duplex stainless steel and improve the wear resistance and its hardness properties. Therefore, the main aim of this work is to nitride alloy layer on the surface of duplex stainless steel by the nitriding process temperature of 400°C and 450°C at different time and ammonia composition using a horizontal tube furnace. The scanning electron microscopy and x-ray diffraction analyzer are used to analyse the morphology, composition and the nitrided alloy layer for treated DSS. The micro hardnesss Vickers tester was used to measure hardness on cross-sectional area of nitrided DSS. After nitriding, it was observed that the hardness performance increased until 1100 Hv0.5kgf compared to substrate material of 250 Hv0.5kgf. The thickness layer of nitride alloy also increased from 5μm until 100μm due to diffusion of nitrogen on the surface of DSS. The x-ray diffraction results showed that the nitride layer consists of iron nitride, expanded austenite and chromium nitride. It can be concluded that nitride alloy layer can be produced via nitriding process using tube furnace with significant improvement of microstructural and hardness properties.

  15. Hafnium nitride buffer layers for growth of GaN on silicon

    Science.gov (United States)

    Armitage, Robert D.; Weber, Eicke R.

    2005-08-16

    Gallium nitride is grown by plasma-assisted molecular-beam epitaxy on (111) and (001) silicon substrates using hafnium nitride buffer layers. Wurtzite GaN epitaxial layers are obtained on both the (111) and (001) HfN/Si surfaces, with crack-free thickness up to 1.2 {character pullout}m. However, growth on the (001) surface results in nearly stress-free films, suggesting that much thicker crack-free layers could be obtained.

  16. Numerical Simulation of Ballistic Impact of Layered Aluminum Nitride Ceramic

    Science.gov (United States)

    2015-09-01

    ARL-TR-7416 ● SEP 2015 US Army Research Laboratory Numerical Simulation of Ballistic Impact of Layered Aluminum Nitride Ceramic...of Ballistic Impact of Layered Aluminum Nitride Ceramic by JD Clayton Weapons and Materials Research Directorate, ARL...Numerical Simulation of Ballistic Impact of Layered Aluminum Nitride Ceramic 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6

  17. Synthesis of ternary nitrides by mechanochemical alloying

    DEFF Research Database (Denmark)

    Jacobsen, C.J.H.; Zhu, J.J.; Lindelov, H.

    2002-01-01

    nitrides by mechanochemical alloying of a binary transition metal nitride (MxN) with an elemental transition metal. In this way, we have been able to prepare Fe3Mo3N and Co3Mo3N by ball-milling of Mo2N with Fe and Co, respectively. The transformation sequence from the starting materials ( the binary...

  18. PECVD silicon nitride diaphragms for condenser microphones

    NARCIS (Netherlands)

    Scheeper, P.R.; Scheeper, P.R.; Voorthuyzen, J.A.; Voorthuyzen, J.A.; Bergveld, Piet

    1991-01-01

    The application of plasma-enhanced chemical vapour deposited (PECVD) silicon nitride as a diaphragm material for condenser microphones has been investigated. By means of adjusting the SiH4/NH3 gas-flow composition, silicon-rich silicon nitride films have been obtained with a relatively low tensile

  19. III-nitride devices and nanoengineering

    National Research Council Canada - National Science Library

    Feng, Zhe Chuan

    2008-01-01

    ... devices applications. III-Nitrides-based industry is forming up and new economic developments these materials are promising. It is expected that III-Nitrides-based LEDs might replace the traditional light bulbs to a revolution in lightings and change entire human life in this century, similar to Edison's invention of the electric lig...

  20. A Ceramic Armor Material Database

    National Research Council Canada - National Science Library

    Holmquist, T

    1999-01-01

    .... The data include nine different ceramic materials. The ceramics are Silicon Carbide, Boron Carbide, Titanium Diboride, Aluminum Nitride, Silicon Nitride, Aluminum Oxide (85% pure), Aluminum Oxide (high purity...

  1. Power Electronic Semiconductor Materials for Automotive and Energy Saving Applications - SiC, GaN, Ga2O3, and Diamond.

    Science.gov (United States)

    Wellmann, Peter J

    2017-11-17

    Power electronics belongs to the future key technologies in order to increase system efficiency as well as performance in automotive and energy saving applications. Silicon is the major material for electronic switches since decades. Advanced fabrication processes and sophisticated electronic device designs have optimized the silicon electronic device performance almost to their theoretical limit. Therefore, to increase the system performance, new materials that exhibit physical and chemical properties beyond silicon need to be explored. A number of wide bandgap semiconductors like silicon carbide, gallium nitride, gallium oxide, and diamond exhibit outstanding characteristics that may pave the way to new performance levels. The review will introduce these materials by (i) highlighting their properties, (ii) introducing the challenges in materials growth, and (iii) outlining limits that need innovation steps in materials processing to outperform current technologies.

  2. Aluminum nitride grating couplers.

    Science.gov (United States)

    Ghosh, Siddhartha; Doerr, Christopher R; Piazza, Gianluca

    2012-06-10

    Grating couplers in sputtered aluminum nitride, a piezoelectric material with low loss in the C band, are demonstrated. Gratings and a waveguide micromachined on a silicon wafer with 600 nm minimum feature size were defined in a single lithography step without partial etching. Silicon dioxide (SiO(2)) was used for cladding layers. Peak coupling efficiency of -6.6 dB and a 1 dB bandwidth of 60 nm have been measured. This demonstration of wire waveguides and wideband grating couplers in a material that also has piezoelectric and elasto-optic properties will enable new functions for integrated photonics and optomechanics.

  3. Gallium and copper radiopharmaceutical chemistry

    International Nuclear Information System (INIS)

    Green, M.A.

    1991-01-01

    Gallium and copper radionuclides have a long history of use in nuclear medicine. Table 1 presents the nuclear properties of several gallium and copper isotopes that either are used in the routine practice of clinical nuclear medicine or exhibit particular characteristics that might make them useful in diagnostic or therapeutic medicine. This paper will provide some historic perspective along with an overview of some current research directions in gallium and copper radiopharmaceutical chemistry. A more extensive review of gallium radiopharmaceutical chemistry has recently appeared and can be consulted for a more in-depth treatment of this topic

  4. Plasma nitriding of steels

    CERN Document Server

    Aghajani, Hossein

    2017-01-01

    This book focuses on the effect of plasma nitriding on the properties of steels. Parameters of different grades of steels are considered, such as structural and constructional steels, stainless steels and tools steels. The reader will find within the text an introduction to nitriding treatment, the basis of plasma and its roll in nitriding. The authors also address the advantages and disadvantages of plasma nitriding in comparison with other nitriding methods. .

  5. Aluminum Nitride Micro-Channels Grown via Metal Organic Vapor Phase Epitaxy for MEMs Applications

    Energy Technology Data Exchange (ETDEWEB)

    Rodak, L.E.; Kuchibhatla, S.; Famouri, P.; Ting, L.; Korakakis, D.

    2008-01-01

    Aluminum nitride (AlN) is a promising material for a number of applications due to its temperature and chemical stability. Furthermore, AlN maintains its piezoelectric properties at higher temperatures than more commonly used materials, such as Lead Zirconate Titanate (PZT) [1, 2], making AlN attractive for high temperature micro and nanoelectromechanical (MEMs and NEMs) applications including, but not limited to, high temperature sensors and actuators, micro-channels for fuel cell applications, and micromechanical resonators. This work presents a novel AlN micro-channel fabrication technique using Metal Organic Vapor Phase Epitaxy (MOVPE). AlN easily nucleates on dielectric surfaces due to the large sticking coefficient and short diffusion length of the aluminum species resulting in a high quality polycrystalline growth on typical mask materials, such as silicon dioxide and silicon nitride [3,4]. The fabrication process introduced involves partially masking a substrate with a silicon dioxide striped pattern and then growing AlN via MOVPE simultaneously on the dielectric mask and exposed substrate. A buffered oxide etch is then used to remove the underlying silicon dioxide and leave a free standing AlN micro-channel. The width of the channel has been varied from 5 ìm to 110 ìm and the height of the air gap from 130 nm to 800 nm indicating the stability of the structure. Furthermore, this versatile process has been performed on (111) silicon, c-plane sapphire, and gallium nitride epilayers on sapphire substrates. Reflection High Energy Electron Diffraction (RHEED), Atomic Force Microscopy (AFM), and Raman measurements have been taken on channels grown on each substrate and indicate that the substrate is influencing the growth of the AlN micro-channels on the SiO2 sacrificial layer.

  6. Functionalized carbon nitride (g-CN) monolayer as a promising energy storage material: A density functional theory study

    Science.gov (United States)

    Hussain, T.; Kaewmaraya, T.; Hankel, M.; Amornkitbamrung, V.

    2017-10-01

    Two-dimensional graphitic carbon nitride (g-CN) sheet, functionalized with polylithiated molecules (CLi2, OLi2), has been investigated to study their structural, electronic and hydrogen (H2) storage properties by van der Waals corrected first principles calculation. A strong binding of both CLi2/OLi2 with two-sided coverage and large enough molecular distance ensures their uniform dispersion over the g-CN monolayer without forming clusters. Each Li in g-CN@2CLi2 (g-CN@2OLi2) adsorbs 3H2, due to its cationic nature through transferring a portion of its charge, resulting into a high H2 storage capacity of 10.34% (9.76%). The calculated H2 adsorption energies are well suited for practical applications.

  7. Graphitic Carbon Nitride Supported Catalysts for Polymer Electrolyte Fuel Cells

    Science.gov (United States)

    2014-01-01

    Graphitic carbon nitrides are investigated for developing highly durable Pt electrocatalyst supports for polymer electrolyte fuel cells (PEFCs). Three different graphitic carbon nitride materials were synthesized with the aim to address the effect of crystallinity, porosity, and composition on the catalyst support properties: polymeric carbon nitride (gCNM), poly(triazine) imide carbon nitride (PTI/Li+Cl–), and boron-doped graphitic carbon nitride (B-gCNM). Following accelerated corrosion testing, all graphitic carbon nitride materials are found to be more electrochemically stable compared to conventional carbon black (Vulcan XC-72R) with B-gCNM support showing the best stability. For the supported catalysts, Pt/PTI-Li+Cl– catalyst exhibits better durability with only 19% electrochemical surface area (ECSA) loss versus 36% for Pt/Vulcan after 2000 scans. Superior methanol oxidation activity is observed for all graphitic carbon nitride supported Pt catalysts on the basis of the catalyst ECSA. PMID:24748912

  8. Graphitic Carbon Nitride Supported Catalysts for Polymer Electrolyte Fuel Cells.

    Science.gov (United States)

    Mansor, Noramalina; Jorge, A Belen; Corà, Furio; Gibbs, Christopher; Jervis, Rhodri; McMillan, Paul F; Wang, Xiaochen; Brett, Daniel J L

    2014-04-03

    Graphitic carbon nitrides are investigated for developing highly durable Pt electrocatalyst supports for polymer electrolyte fuel cells (PEFCs). Three different graphitic carbon nitride materials were synthesized with the aim to address the effect of crystallinity, porosity, and composition on the catalyst support properties: polymeric carbon nitride (gCNM), poly(triazine) imide carbon nitride (PTI/Li + Cl - ), and boron-doped graphitic carbon nitride (B-gCNM). Following accelerated corrosion testing, all graphitic carbon nitride materials are found to be more electrochemically stable compared to conventional carbon black (Vulcan XC-72R) with B-gCNM support showing the best stability. For the supported catalysts, Pt/PTI-Li + Cl - catalyst exhibits better durability with only 19% electrochemical surface area (ECSA) loss versus 36% for Pt/Vulcan after 2000 scans. Superior methanol oxidation activity is observed for all graphitic carbon nitride supported Pt catalysts on the basis of the catalyst ECSA.

  9. Method of fabricating germanium and gallium arsenide devices

    Science.gov (United States)

    Jhabvala, Murzban (Inventor)

    1990-01-01

    A method of semiconductor diode fabrication is disclosed which relies on the epitaxial growth of a precisely doped thickness layer of gallium arsenide or germanium on a semi-insulating or intrinsic substrate, respectively, of gallium arsenide or germanium by either molecular beam epitaxy (MBE) or by metal-organic chemical vapor deposition (MOCVD). The method involves: depositing a layer of doped or undoped silicon dioxide on a germanium or gallium arsenide wafer or substrate, selectively removing the silicon dioxide layer to define one or more surface regions for a device to be fabricated thereon, growing a matched epitaxial layer of doped germanium or gallium arsenide of an appropriate thickness using MBE or MOCVD techniques on both the silicon dioxide layer and the defined one or more regions; and etching the silicon dioxide and the epitaxial material on top of the silicon dioxide to leave a matched epitaxial layer of germanium or gallium arsenide on the germanium or gallium arsenide substrate, respectively, and upon which a field effect device can thereafter be formed.

  10. Continuum modeling of boron nitride nanotubes

    International Nuclear Information System (INIS)

    Song, J; Wu, J; Hwang, K C; Huang, Y

    2008-01-01

    Boron nitride nanotubes display unique properties and have many potential applications. A finite-deformation shell theory is developed for boron nitride nanotubes directly from the interatomic potential to account for the effect of bending and curvature. Its constitutive relation accounts for the nonlinear, multi-body atomistic interactions, and therefore can model the important effect of tube chirality and radius. The theory is then used to determine whether a single-wall boron nitride nanotube can be modeled as a linear elastic isotropic shell. Instabilities of boron nitride nanotubes under different loadings (e.g., tension, compression, and torsion) are also studied. It is shown that the tension instability of boron nitride nanotubes is material instability, while the compression and torsion instabilities are structural instabilities.

  11. A gel aging effect in the synthesis of open-framework gallium phosphates: structure solution and solid-state NMR of a large-pore, open-framework material.

    Science.gov (United States)

    Broom, Lucy K; Clarkson, Guy J; Guillou, Nathalie; Hooper, Joseph E; Dawson, Daniel M; Tang, Chiu C; Ashbrook, Sharon E; Walton, Richard I

    2017-12-12

    The templated zeolite-analogue GaPO-34 (CHA structure type) crystallises from a gel precursor Ga 2 O 3  : 2H 3 PO 4  : 1HF : 1.7SDA : 70H 2 O (where SDA = structure directing agent), treated hydrothermally for 24 hours at 170 °C using either pyridine or 1-methylimizadole as SDA and one of either poorly crystalline ε-Ga 2 O 3 or γ-Ga 2 O 3 as gallium precursor. If the same gels are stirred for periods shorter than 2 hours but treated under identical hydrothermal conditions, then a second phase crystallises, free of GaPO-34. If β-Ga 2 O 3 is used as a reagent only the second phase is found to crystallise, irrespective of gel aging time. The competing phase, which we denote GaPO-34A, has been structurally characterised using synchrotron powder X-ray diffraction for the pyridine material, GaPO-34A(pyr), and using single-crystal X-ray diffraction for the 1-methylimiazole material, GaPO-34A(mim). The structure of GaPO-34A(pyr), P1[combining macron], a = 10.22682(6) Å, b = 12.09585(7) Å, c = 13.86713(8) Å, α = 104.6531(4)°, β = 100.8111(6)°, γ = 102.5228(6)°, contains 7 unique gallium sites and 6 phosphorus sites, with empirical formula [Ga 7 P 6 O 24 (OH) 2 F 3 (H 2 O) 2 ]·2(C 5 NH 6 ). GaPO-34A(mim) is isostructural but is modelled as a half volume unit cell, P1[combining macron], a = 5.0991(2) Å, b = 12.0631(6) Å, c = 13.8405(9) Å, α = 104.626(5)°, β = 100.346(5)°, γ = 101.936(4)°, with a gallium and a bridging fluoride partially occupied and two partially occupied SDA sites. Solid-state 31 P and 71 Ga NMR spectroscopy confirms the structural complexity of GaPO-34A with signals resulting from overlapping lineshapes from multiple Ga and P sites, while 1 H and 13 C solid-state NMR spectra confirm the presence of the protonated SDA and provide evidence for disorder in the SDA. The protonated SDA is located in 14-ring one-dimensional channels with hydrogen bonding deduced from the SDA nitrogens to framework oxygen distances. Upon

  12. Gallium--A smart metal

    Science.gov (United States)

    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.

  13. Simulation of the Nitriding Process

    Science.gov (United States)

    Krukovich, M. G.

    2004-01-01

    Simulation of the nitriding process makes it possible to solve many practical problems of process control, prediction of results, and development of new treatment modes and treated materials. The presented classification systematizes nitriding processes and processes based on nitriding, enables consideration of the theory and practice of an individual process in interrelation with other phenomena, outlines ways for intensification of various process variants, and gives grounds for development of recommendations for controlling the structure and properties of the obtained layers. The general rules for conducting the process and formation of phases in the layer and properties of the treated surfaces are used to create a prediction computational model based on analytical, numerical, and empirical approaches.

  14. Functionalized boron nitride nanotubes

    Science.gov (United States)

    Sainsbury, Toby; Ikuno, Takashi; Zettl, Alexander K

    2014-04-22

    A plasma treatment has been used to modify the surface of BNNTs. In one example, the surface of the BNNT has been modified using ammonia plasma to include amine functional groups. Amine functionalization allows BNNTs to be soluble in chloroform, which had not been possible previously. Further functionalization of amine-functionalized BNNTs with thiol-terminated organic molecules has also been demonstrated. Gold nanoparticles have been self-assembled at the surface of both amine- and thiol-functionalized boron nitride Nanotubes (BNNTs) in solution. This approach constitutes a basis for the preparation of highly functionalized BNNTs and for their utilization as nanoscale templates for assembly and integration with other nanoscale materials.

  15. Facility for low-temperature spin-polarized-scanning tunneling microscopy studies of magnetic/spintronic materials prepared in situ by nitride molecular beam epitaxy.

    Science.gov (United States)

    Lin, Wenzhi; Foley, Andrew; Alam, Khan; Wang, Kangkang; Liu, Yinghao; Chen, Tianjiao; Pak, Jeongihm; Smith, Arthur R

    2014-04-01

    Based on the interest in, as well as exciting outlook for, nitride semiconductor based structures with regard to electronic, optoelectronic, and spintronic applications, it is compelling to investigate these systems using the powerful technique of spin-polarized scanning tunneling microscopy (STM), a technique capable of achieving magnetic resolution down to the atomic scale. However, the delicate surfaces of these materials are easily corrupted by in-air transfers, making it unfeasible to study them in stand-alone ultra-high vacuum STM facilities. Therefore, we have carried out the development of a hybrid system including a nitrogen plasma assisted molecular beam epitaxy/pulsed laser epitaxy facility for sample growth combined with a low-temperature, spin-polarized scanning tunneling microscope system. The custom-designed molecular beam epitaxy growth system supports up to eight sources, including up to seven effusion cells plus a radio frequency nitrogen plasma source, for epitaxially growing a variety of materials, such as nitride semiconductors, magnetic materials, and their hetero-structures, and also incorporating in situ reflection high energy electron diffraction. The growth system also enables integration of pulsed laser epitaxy. The STM unit has a modular design, consisting of an upper body and a lower body. The upper body contains the coarse approach mechanism and the scanner unit, while the lower body accepts molecular beam epitaxy grown samples using compression springs and sample skis. The design of the system employs two stages of vibration isolation as well as a layer of acoustic noise isolation in order to reduce noise during STM measurements. This isolation allows the system to effectively acquire STM data in a typical lab space, which during its construction had no special and highly costly elements included, (such as isolated slabs) which would lower the environmental noise. The design further enables tip exchange and tip coating without

  16. Facility for low-temperature spin-polarized-scanning tunneling microscopy studies of magnetic/spintronic materials prepared in situ by nitride molecular beam epitaxy

    International Nuclear Information System (INIS)

    Lin, Wenzhi; Foley, Andrew; Alam, Khan; Wang, Kangkang; Liu, Yinghao; Chen, Tianjiao; Pak, Jeongihm; Smith, Arthur R.

    2014-01-01

    Based on the interest in, as well as exciting outlook for, nitride semiconductor based structures with regard to electronic, optoelectronic, and spintronic applications, it is compelling to investigate these systems using the powerful technique of spin-polarized scanning tunneling microscopy (STM), a technique capable of achieving magnetic resolution down to the atomic scale. However, the delicate surfaces of these materials are easily corrupted by in-air transfers, making it unfeasible to study them in stand-alone ultra-high vacuum STM facilities. Therefore, we have carried out the development of a hybrid system including a nitrogen plasma assisted molecular beam epitaxy/pulsed laser epitaxy facility for sample growth combined with a low-temperature, spin-polarized scanning tunneling microscope system. The custom-designed molecular beam epitaxy growth system supports up to eight sources, including up to seven effusion cells plus a radio frequency nitrogen plasma source, for epitaxially growing a variety of materials, such as nitride semiconductors, magnetic materials, and their hetero-structures, and also incorporating in situ reflection high energy electron diffraction. The growth system also enables integration of pulsed laser epitaxy. The STM unit has a modular design, consisting of an upper body and a lower body. The upper body contains the coarse approach mechanism and the scanner unit, while the lower body accepts molecular beam epitaxy grown samples using compression springs and sample skis. The design of the system employs two stages of vibration isolation as well as a layer of acoustic noise isolation in order to reduce noise during STM measurements. This isolation allows the system to effectively acquire STM data in a typical lab space, which during its construction had no special and highly costly elements included, (such as isolated slabs) which would lower the environmental noise. The design further enables tip exchange and tip coating without

  17. Gallium Arsenide Domino Circuit

    Science.gov (United States)

    Yang, Long; Long, Stephen I.

    1990-01-01

    Advantages include reduced power and high speed. Experimental gallium arsenide field-effect-transistor (FET) domino circuit replicated in large numbers for use in dynamic-logic systems. Name of circuit denotes mode of operation, which logic signals propagate from each stage to next when successive stages operated at slightly staggered clock cycles, in manner reminiscent of dominoes falling in a row. Building block of domino circuit includes input, inverter, and level-shifting substages. Combinational logic executed in input substage. During low half of clock cycle, result of logic operation transmitted to following stage.

  18. Simple process to fabricate nitride alloy powders

    International Nuclear Information System (INIS)

    Yang, Jae Ho; Kim, Dong-Joo; Kim, Keon Sik; Rhee, Young Woo; Oh, Jang-Soo; Kim, Jong Hun; Koo, Yang Hyun

    2013-01-01

    Uranium mono-nitride (UN) is considered as a fuel material [1] for accident-tolerant fuel to compensate for the loss of fissile fuel material caused by adopting a thickened cladding such as SiC composites. Uranium nitride powders can be fabricated by a carbothermic reduction of the oxide powders, or the nitriding of metal uranium. Among them, a direct nitriding process of metal is more attractive because it has advantages in the mass production of high-purity powders and the reusing of expensive 15 N 2 gas. However, since metal uranium is usually fabricated in the form of bulk ingots, it has a drawback in the fabrication of fine powders. The Korea Atomic Energy Research Institute (KAERI) has a centrifugal atomisation technique to fabricate uranium and uranium alloy powders. In this study, a simple reaction method was tested to fabricate nitride fuel powders directly from uranium metal alloy powders. Spherical powder and flake of uranium metal alloys were fabricated using a centrifugal atomisation method. The nitride powders were obtained by thermal treating the metal particles under nitrogen containing gas. The phase and morphology evolutions of powders were investigated during the nitriding process. A phase analysis of nitride powders was also part of the present work. KAERI has developed the centrifugal rotating disk atomisation process to fabricate spherical uranium metal alloy powders which are used as advanced fuel materials for research reactors. The rotating disk atomisation system involves the tasks of melting, atomising, and collecting. A nozzle in the bottom of melting crucible introduces melt at the center of a spinning disk. The centrifugal force carries the melt to the edge of the disk and throws the melt off the edge. Size and shape of droplets can be controlled by changing the nozzle size, the disk diameter and disk speed independently or simultaneously. By adjusting the processing parameters of the centrifugal atomiser, a spherical and flake shape

  19. Gallium nitride nanoparticles for solar-blind detectors

    Indian Academy of Sciences (India)

    We investigate the properties of GaN semiconducting nanoparticles as a potential candidate for photodetection in the solar-blind region. The photocurrent spectral response is studied spanning the range 1.6-5.5 eV. A significant fraction of the response is in the range 4-5.5 eV. The results are compared to other optical ...

  20. Electrical and optical properties of silicon-doped gallium nitride ...

    Indian Academy of Sciences (India)

    WINTEC

    The main technological interest in the polycrystalline based devices lies in its very low production cost and ... ing (13⋅56 MHz) technique using a GaN target containing. 1 at % Si. The Si-doped GaN target was made by ... power ~ 200 W. Before starting the deposition, the target was pre-sputtered for ~ 10 min with a shutter ...

  1. Thermal characterization of gallium nitride p-i-n diodes

    Science.gov (United States)

    Dallas, J.; Pavlidis, G.; Chatterjee, B.; Lundh, J. S.; Ji, M.; Kim, J.; Kao, T.; Detchprohm, T.; Dupuis, R. D.; Shen, S.; Graham, S.; Choi, S.

    2018-02-01

    In this study, various thermal characterization techniques and multi-physics modeling were applied to understand the thermal characteristics of GaN vertical and quasi-vertical power diodes. Optical thermography techniques typically used for lateral GaN device temperature assessment including infrared thermography, thermoreflectance thermal imaging, and Raman thermometry were applied to GaN p-i-n diodes to determine if each technique is capable of providing insight into the thermal characteristics of vertical devices. Of these techniques, thermoreflectance thermal imaging and nanoparticle assisted Raman thermometry proved to yield accurate results and are the preferred methods of thermal characterization of vertical GaN diodes. Along with this, steady state and transient thermoreflectance measurements were performed on vertical and quasi-vertical GaN p-i-n diodes employing GaN and Sapphire substrates, respectively. Electro-thermal modeling was performed to validate measurement results and to demonstrate the effect of current crowding on the thermal response of quasi-vertical diodes. In terms of mitigating the self-heating effect, both the steady state and transient measurements demonstrated the superiority of the tested GaN-on-GaN vertical diode compared to the tested GaN-on-Sapphire quasi-vertical structure.

  2. Gallium-Nitride-Based Light-Emitting Diodes

    Indian Academy of Sciences (India)

    IAS Admin

    The advent of the semiconductor light-emitting diode (LED) emerged as a key component in our modern lighting technologies. While LEDs of various colors have been invented since 1950s, the blue LED was elusive till the 1990s. Blue light, with blue being one of the primary colors, is essential for white light emission.

  3. Gallium Nitride Direct Energy Conversion Betavoltaic Modeling and Optimization

    Science.gov (United States)

    2017-03-01

    Autonomous sensors could be used by being placed in situations where replacement of the power source is difficult such as inside concrete pillars...EHP creation takes place beyond the depletion region. Higher energy electrons increase the energy deposited, but less of it is available to be...device blocking the input electron beam. The impact of the metal contact effectively shields the semiconductor, reducing the effective EHP

  4. Gallium-Nitride-Based Light-Emitting Diodes

    Indian Academy of Sciences (India)

    IAS Admin

    ing filament [1, 2]. Figure 1 shows the picture of the incandescent lamp built by Edison in 1870s (a), and the schematic of an incandescent and fluorescent lamp (b). While these inventions have dramatically transformed human society, a lot more needed to be done to improve the energy efficiency of artificial sources of light.

  5. Synthesis of ternary nitrides by mechanochemical alloying

    DEFF Research Database (Denmark)

    Jacobsen, C.J.H.; Zhu, J.J.; Lindelov, H.

    2002-01-01

    Ternary metal nitrides ( of general formula MxM'N-y(z)) attract considerable interest because of their special mechanical, electrical, magnetic, and catalytic properties. Usually they are prepared by ammonolysis of ternary oxides (MxM'O-y(m)) at elevated temperatures. We show that ternary...... nitrides by mechanochemical alloying of a binary transition metal nitride (MxN) with an elemental transition metal. In this way, we have been able to prepare Fe3Mo3N and Co3Mo3N by ball-milling of Mo2N with Fe and Co, respectively. The transformation sequence from the starting materials ( the binary...

  6. Preparation of uranium nitride

    International Nuclear Information System (INIS)

    Potter, R.A.; Tennery, V.J.

    1976-01-01

    A process is described for preparing actinide-nitrides from massive actinide metal which is suitable for sintering into low density fuel shapes by partially hydriding the massive metal and simultaneously dehydriding and nitriding the dehydrided portion. The process is repeated until all of the massive metal is converted to a nitride

  7. Solvothermal synthesis, crystal structure, and second-order nonlinear optical properties of a new noncentrosymmetric gallium-organic framework material, [N(C3H7)4]3Ga3[C6H3(CO2)3]4

    Science.gov (United States)

    Lee, Dong Woo; Jo, Vinna; Ok, Kang Min

    2012-10-01

    A novel noncentrosymmetric (NCS) gallium-organic framework material, [N(C3H7)4]3Ga3[C6H3(CO2)3]4 (CAUMOF-11) has been synthesized by a solvothermal reaction using Ga(NO3)3·xH2O, 1,3,5-C6H3(CO2H)3, N(C3H7)4Cl, HNO3, and HCON(CH3)2 at 180 °C. The structure of the reported material has been determined by single-crystal X-ray diffraction. CAUMOF-11 has an anionic three-dimensional framework with aligned four-coordinate GaO4 tetrahedra and 1,3,5-benzenetricarboxylate groups. Tetrapropylammonim cations reside within the channel and maintain the charge balance. Detailed structural analyses with full characterization including infrared spectroscopy, thermogravimetric analysis, elemental analysis, ion-exchange reactions, topotactic decomposition, and gas adsorption experiments are reported. Powder second-harmonic generating (SHG) measurements on CAUMOF-11, using 1064 nm radiation, exhibit SHG efficiency of 15 times that of α-SiO2 and the material is phase-matchable (type-1).

  8. Electrochemical Solution Growth of Magnetic Nitrides

    Energy Technology Data Exchange (ETDEWEB)

    Monson, Todd C. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Pearce, Charles [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2014-10-01

    Magnetic nitrides, if manufactured in bulk form, would provide designers of transformers and inductors with a new class of better performing and affordable soft magnetic materials. According to experimental results from thin films and/or theoretical calculations, magnetic nitrides would have magnetic moments well in excess of current state of the art soft magnets. Furthermore, magnetic nitrides would have higher resistivities than current transformer core materials and therefore not require the use of laminates of inactive material to limit eddy current losses. However, almost all of the magnetic nitrides have been elusive except in difficult to reproduce thin films or as inclusions in another material. Now, through its ability to reduce atmospheric nitrogen, the electrochemical solution growth (ESG) technique can bring highly sought after (and previously inaccessible) new magnetic nitrides into existence in bulk form. This method utilizes a molten salt as a solvent to solubilize metal cations and nitrogen ions produced electrochemically and form nitrogen compounds. Unlike other growth methods, the scalable ESG process can sustain high growth rates (~mm/hr) even under reasonable operating conditions (atmospheric pressure and 500 °C). Ultimately, this translates into a high throughput, low cost, manufacturing process. The ESG process has already been used successfully to grow high quality GaN. Below, the experimental results of an exploratory express LDRD project to access the viability of the ESG technique to grow magnetic nitrides will be presented.

  9. Speed gallium arsenide photoconductors; Photoconducteurs rapides en arseniure de gallium

    Energy Technology Data Exchange (ETDEWEB)

    Foulon, F.; Pochet, T. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. d`Electronique et d`Instrumentation Nucleaire; Brullot, B. [CEA Centre d`Etudes de Bruyeres-le-Chatel, 91 (France)

    1993-12-31

    Gallium arsenide detectors are one of the most efficient gamma and X ray detectors at room temperature. Due to the high carrier mobility and short carrier lifetime, GaAs can be used for the detection of ultrafast gamma, X or laser pulses. GaAs photoconductors allow both pulse shape and intensity measurements. In this paper, we review the results of studies carried out jointly by the CEA/LETI/DEIN and CEA/DAM/CEM in France to improve the response of such detectors. The geometry of the photodetectors and their electrical contacts have been optimized for specific radiation measurements: low energy X rays (< 1 KeV), gamma rays or protons. It has been shown that a pre-irradiation treatment with fission neutrons at doses above 10{sup 14} n/cm{sup 2} induces a significant improvement of the response speed. This result from defect generation in the material and the subsequent carrier life time decrease. Detectors with sensitivities of about 10{sup -8} A/R.s for gamma rays and 10{sup -16} coulomb/proton, response times below 100 ps and good linearity over more than five decades are currently fabricated in our laboratory. (authors). 18 refs., 5 figs., 3 tabs.

  10. Gallium Safety in the Laboratory

    International Nuclear Information System (INIS)

    Cadwallader, L.C.

    2003-01-01

    A university laboratory experiment for the US Department of Energy magnetic fusion research program required a simulant for liquid lithium. The simulant choices were narrowed to liquid gallium and galinstan (Ga-In-Sn) alloy. Safety information on liquid gallium and galinstan were compiled, and the choice was made to use galinstan. A laboratory safety walkthrough was performed in the fall of 2002 to support the galinstan experiment. The experiment has been operating successfully since early 2002

  11. Gallium Safety in the Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Cadwallader, L.C.

    2003-05-07

    A university laboratory experiment for the US Department of Energy magnetic fusion research program required a simulant for liquid lithium. The simulant choices were narrowed to liquid gallium and galinstan (Ga-In-Sn) alloy. Safety information on liquid gallium and galinstan were compiled, and the choice was made to use galinstan. A laboratory safety walkthrough was performed in the fall of 2002 to support the galinstan experiment. The experiment has been operating successfully since early 2002.

  12. Gallium Safety in the Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Lee C. Cadwallader

    2003-06-01

    A university laboratory experiment for the US Department of Energy magnetic fusion research program required a simulant for liquid lithium. The simulant choices were narrowed to liquid gallium and galinstan (Ga-In-Sn) alloy. Safety information on liquid gallium and galinstan were compiled, and the choice was made to use galinstan. A laboratory safety walkthrough was performed in the fall of 2002 to support the galinstan experiment. The experiment has been operating successfully since early 2002.

  13. Liquid gallium jet-plasma interaction studies in ISTTOK tokamak

    International Nuclear Information System (INIS)

    Gomes, R.B.; Fernandes, H.; Silva, C.; Sarakovskis, A.; Pereira, T.; Figueiredo, J.; Carvalho, B.; Soares, A.; Duarte, P.; Varandas, C.; Lielausis, O.; Klyukin, A.; Platacis, E.; Tale, I.; Alekseyv, A.

    2009-01-01

    Liquid metals have been pointed out as a suitable solution to solve problems related to the use of solid walls submitted to high power loads allowing, simultaneously, an efficient heat exhaustion process from fusion devices. The most promising candidate materials are lithium and gallium. However, lithium has a short liquid state temperature range when compared with gallium. To explore further this property, ISTTOK tokamak is being used to test the interaction of a free flying liquid gallium jet with the plasma. ISTTOK has been successfully operated with this jet without noticeable discharge degradation and no severe effect on the main plasma parameters or a significant plasma contamination by liquid metal. Additionally the response of an infrared sensor, intended to measure the jet surface temperature increase during its interaction with the plasma, has been studied. The jet power extraction capability is extrapolated from the heat flux profiles measured in ISTTOK plasmas.

  14. Surface Passivation of CIGS Solar Cells Using Gallium Oxide

    KAUST Repository

    Garud, Siddhartha

    2018-02-27

    This work proposes gallium oxide grown by plasma-enhanced atomic layer deposition, as a surface passivation material at the CdS buffer interface of Cu(In,Ga)Se2 (CIGS) solar cells. In preliminary experiments, a metal-insulator-semiconductor (MIS) structure is used to compare aluminium oxide, gallium oxide, and hafnium oxide as passivation layers at the CIGS-CdS interface. The findings suggest that gallium oxide on CIGS may show a density of positive charges and qualitatively, the least interface trap density. Subsequent solar cell results with an estimated 0.5 nm passivation layer show an substantial absolute improvement of 56 mV in open-circuit voltage (VOC), 1 mA cm−2 in short-circuit current density (JSC), and 2.6% in overall efficiency as compared to a reference (with the reference showing 8.5% under AM 1.5G).

  15. Graphene on gallium arsenide: Engineering the visibility

    OpenAIRE

    Friedemann, M.; Pierz, K.; Stosch, R.; Ahlers, F. J.

    2009-01-01

    Graphene consists of single or few layers of crystalline ordered carbon atoms. Its visibility on oxidized silicon (Si/SiO\\_2) enabled its discovery and spawned numerous studies of its unique electronic properties. The combination of graphene with the equally unique electronic material gallium arsenide (GaAs) has up to now lacked such easy visibility. Here we demonstrate that a deliberately tailored GaAs/AlAs (aluminum arsenide) multi-layer structure makes graphene just as visible on GaAs as o...

  16. Elastic properties of indium nitrides grown on sapphire substrates determined by nano-indentation: In comparison with other nitrides

    Directory of Open Access Journals (Sweden)

    Ichiro Yonenaga

    2015-07-01

    Full Text Available The hardness of wurtzite indium nitride (α-InN films of 0.5 to 4 μm in thickness was measured by the nano-indentation method at room temperature. After investigation of crystalline quality by x-ray diffraction, the hardness and Young’s modulus were determined to be 8.8 ± 0.4 and 184 ± 5 GPa, respectively, for the In (0001- and N ( 000 1 ̄ -growth faces of InN films. The bulk and shear moduli were then derived to be 99 ± 3 and 77 ± 2 GPa, respectively. The Poisson’s ratio was evaluated to be 0.17 ± 0.03. The results were examined comprehensively in comparison with previously reported data of InN as well as those of other nitrides of aluminum nitride and gallium nitride. The underlying physical process determining the moduli and hardness was examined in terms of atomic bonding and dislocation energy of the nitrides and wurtzite zinc oxide.

  17. Amorphous and nanocrystalline titanium nitride and carbonitride materials obtained by solution phase ammonolysis of Ti(NMe2)4

    International Nuclear Information System (INIS)

    Jackson, Andrew W.; Shebanova, Olga; Hector, Andrew L.; McMillan, Paul F.

    2006-01-01

    Solution phase reactions between tetrakisdimethylamidotitanium (Ti(NMe 2 ) 4 ) and ammonia yield precipitates with composition TiC 0.5 N 1.1 H 2.3 . Thermogravimetric analysis (TGA) indicates that decomposition of these precursor materials proceeds in two steps to yield rocksalt-structured TiN or Ti(C,N), depending upon the gas atmosphere. Heating to above 700 deg. C in NH 3 yields nearly stoichiometric TiN. However, heating in N 2 atmosphere leads to isostructural carbonitrides, approximately TiC 0.2 N 0.8 in composition. The particle sizes of these materials range between 4-12 nm. Heating to a temperature that corresponds to the intermediate plateau in the TGA curve (450 deg. C) results in a black powder that is X-ray amorphous and is electrically conducting. The bulk chemical composition of this material is found to be TiC 0.22 N 1.01 H 0.07 , or Ti 3 (C 0.17 N 0.78 H 0.05 ) 3.96 , close to Ti 3 (C,N) 4 . Previous workers have suggested that the intermediate compound was an amorphous form of Ti 3 N 4 . TEM investigation of the material indicates the presence of nanocrystalline regions x (C,N) y crystalline phases

  18. 10 Gallium Complexes as Anticancer Drugs.

    Science.gov (United States)

    Chitambar, Christopher R

    2018-02-05

    Clinical trials have shown gallium nitrate, a group 13 (formerly IIIa) metal salt, to have antineoplastic activity against non-Hodgkin's lymphoma and urothelial cancers. Interest in gallium as a metal with anticancer properties emerged when it was discovered that 67Ga(III) citrate injected in tumor-bearing animals localized to sites of tumor. Animal studies showed non-radioactive gallium nitrate to inhibit the growth of implanted solid tumors. Following further evaluation of its efficacy and toxicity in animals, gallium nitrate, Ga(NO3)3, was designated an investigational drug by the National Cancer Institute (USA) and advanced to Phase 1 and 2 clinical trials. Gallium(III) shares certain chemical characteristics with iron(III) which enable it to interact with iron-binding proteins and disrupt iron-dependent tumor cell growth. Gallium's mechanisms of action include the inhibition of cellular iron uptake and disruption of intracellular iron homeostasis, these effects result in inhibition of ribonucleotide reductase and mitochondrial function, and changes in the expression in proteins of iron transport and storage. Whereas the growth-inhibitory effects of gallium become apparent after 24 to 48 hours of incubation of cells, an increase in intracellular reactive oxygen species (ROS) is seen with 1 to 4 hours of incubation. Gallium-induced ROS consequently triggers the upregulation of metallothionein and hemoxygenase-1 genes. Beyond the first generation of gallium salts such as gallium nitrate and gallium chloride, a new generation of gallium-ligand complexes such as tris(8-quinolinolato)gallium(III) (KP46) and gallium maltolate has emerged. These agents are being evaluated in the clinic while other ligands for gallium are in preclinical development. These newer agents appear to possess greater antitumor efficacy and a broader spectrum of antineoplastic activity than the earlier generation of gallium compounds.

  19. Nano boron nitride flatland.

    Science.gov (United States)

    Pakdel, Amir; Bando, Yoshio; Golberg, Dmitri

    2014-02-07

    Recent years have witnessed many breakthroughs in research on two-dimensional (2D) nanomaterials, among which is hexagonal boron nitride (h-BN), a layered material with a regular network of BN hexagons. This review provides an insight into the marvellous nano BN flatland, beginning with a concise introduction to BN and its low-dimensional nanostructures, followed by an overview of the past and current state of research on 2D BN nanostructures. A comprehensive review of the structural characteristics and synthetic routes of BN monolayers, multilayers, nanomeshes, nanowaves, nanoflakes, nanosheets and nanoribbons is presented. In addition, electronic, optical, thermal, mechanical, magnetic, piezoelectric, catalytic, ecological, biological and wetting properties, applications and research perspectives for these novel 2D nanomaterials are discussed.

  20. Shock Response of Silicon Nitride

    Science.gov (United States)

    Dandekar, D. P.; Casem, D. T.; Motoyashiki, Y.; Sato, E.

    2009-06-01

    Silicon nitride is suitable for varied applications. The properties of silicon nitride have been tailored through processing and doping. The current work presents shock response of silicon nitride marketed as SN282. The density of this material, 3.4 Mg/m^3, exceeds its single crystal density due to the presence of lutetium oxide as an additive in ca. 5% by weight in the material. While the average grain size is 3.4 microns, aspect ratio of the grains exceed 3. Preliminary results of shock wave experiments may be summarized as follows: (1) The Hugoniot Elastic Limit (HEL) of SN282 is 11.2 GPa. (2) The magnitude of the inelastic wave velocity just above the HEL is 8.73 km/s, suggesting that inelastic deformation above the HEL is due to shock induced plasticity in the material. (3) The estimated value of the spall strength is 0.5 GPa. The spall strength of SN282 remains unchanged even when shocked beyond the HEL. The non-vanishing spall strength suggests that doping plays a role in the retention of spall strength of SN282. The role of doping needs to be further investigated.

  1. Glutathione role in gallium induced toxicity

    African Journals Online (AJOL)

    Asim

    2012-01-26

    Jan 26, 2012 ... It is very important and interesting to study the reaction of gallium nitrate and glutathione as biomarker of glutathione ... Key words: Gallium nitrate, reduced glutathione (GSH), whole blood, plasma, cytosolic fraction (CF), oxidized ..... DMSA effect on gallium arsenide induced pathological liver injury in rats.

  2. Synthesis of Uranium nitride powders using metal uranium powders

    International Nuclear Information System (INIS)

    Yang, Jae Ho; Kim, Dong Joo; Oh, Jang Soo; Rhee, Young Woo; Kim, Jong Hun; Kim, Keon Sik

    2012-01-01

    Uranium nitride (UN) is a potential fuel material for advanced nuclear reactors because of their high fuel density, high thermal conductivity, high melting temperature, and considerable breeding capability in LWRs. Uranium nitride powders can be fabricated by a carbothermic reduction of the oxide powders, or the nitriding of metal uranium. The carbothermic reduction has an advantage in the production of fine powders. However it has many drawbacks such as an inevitable engagement of impurities, process burden, and difficulties in reusing of expensive N 15 gas. Manufacturing concerns issued in the carbothermic reduction process can be solved by changing the starting materials from oxide powder to metals. However, in nitriding process of metal, it is difficult to obtain fine nitride powders because metal uranium is usually fabricated in the form of bulk ingots. In this study, a simple reaction method was tested to fabricate uranium nitride powders directly from uranium metal powders. We fabricated uranium metal spherical powder and flake using a centrifugal atomization method. The nitride powders were obtained by thermal treating those metal particles under nitrogen containing gas. We investigated the phase and morphology evolutions of powders during the nitriding process. A phase analysis of nitride powders was also a part of the present work

  3. Manipulation of surface plasmon polariton propagation on isotropic and anisotropic two-dimensional materials coupled to boron nitride heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Inampudi, Sandeep; Nazari, Mina; Forouzmand, Ali; Mosallaei, Hossein, E-mail: hosseinm@coe.neu.edu [Department of Electrical and Computer Engineering, Northeastern University, 360 Huntington Ave., Boston, Massachusetts 02115 (United States)

    2016-01-14

    We present a comprehensive analysis of surface plasmon polariton dispersion characteristics associated with isotropic and anisotropic two-dimensional atomically thin layered materials (2D sheets) coupled to h-BN heterostructures. A scattering matrix based approach is presented to compute the electromagnetic fields and related dispersion characteristics of stacked layered systems composed of anisotropic 2D sheets and uniaxial bulk materials. We analyze specifically the surface plasmon polariton (SPP) dispersion characteristics in case of isolated and coupled two-dimensional layers with isotropic and anisotropic conductivities. An analysis based on residue theorem is utilized to identify optimum optical parameters (surface conductivity) and geometrical parameters (separation between layers) to maximize the SPP field at a given position. The effect of type and degree of anisotropy on the shapes of iso-frequency curves and propagation characteristics is discussed in detail. The analysis presented in this paper gives an insight to identify optimum setup to enhance the SPP field at a given position and in a given direction on the surface of two-dimensional materials.

  4. Medical Applications and Toxicities of Gallium Compounds

    Directory of Open Access Journals (Sweden)

    Christopher R. Chitambar

    2010-05-01

    Full Text Available Over the past two to three decades, gallium compounds have gained importance in the fields of medicine and electronics. In clinical medicine, radioactive gallium and stable gallium nitrate are used as diagnostic and therapeutic agents in cancer and disorders of calcium and bone metabolism. In addition, gallium compounds have displayed anti-inflammatory and immunosuppressive activity in animal models of human disease while more recent studies have shown that gallium compounds may function as antimicrobial agents against certain pathogens. In a totally different realm, the chemical properties of gallium arsenide have led to its use in the semiconductor industry. Gallium compounds, whether used medically or in the electronics field, have toxicities. Patients receiving gallium nitrate for the treatment of various diseases may benefit from such therapy, but knowledge of the therapeutic index of this drug is necessary to avoid clinical toxicities. Animals exposed to gallium arsenide display toxicities in certain organ systems suggesting that environmental risks may exist for individuals exposed to this compound in the workplace. Although the arsenic moiety of gallium arsenide appears to be mainly responsible for its pulmonary toxicity, gallium may contribute to some of the detrimental effects in other organs. The use of older and newer gallium compounds in clinical medicine may be advanced by a better understanding of their mechanisms of action, drug resistance, pharmacology, and side-effects. This review will discuss the medical applications of gallium and its mechanisms of action, the newer gallium compounds and future directions for development, and the toxicities of gallium compounds in current use.

  5. Methods of forming boron nitride

    Science.gov (United States)

    Trowbridge, Tammy L; Wertsching, Alan K; Pinhero, Patrick J; Crandall, David L

    2015-03-03

    A method of forming a boron nitride. The method comprises contacting a metal article with a monomeric boron-nitrogen compound and converting the monomeric boron-nitrogen compound to a boron nitride. The boron nitride is formed on the same or a different metal article. The monomeric boron-nitrogen compound is borazine, cycloborazane, trimethylcycloborazane, polyborazylene, B-vinylborazine, poly(B-vinylborazine), or combinations thereof. The monomeric boron-nitrogen compound is polymerized to form the boron nitride by exposure to a temperature greater than approximately 100.degree. C. The boron nitride is amorphous boron nitride, hexagonal boron nitride, rhombohedral boron nitride, turbostratic boron nitride, wurzite boron nitride, combinations thereof, or boron nitride and carbon. A method of conditioning a ballistic weapon and a metal article coated with the monomeric boron-nitrogen compound are also disclosed.

  6. Nonlinear optics of light induced structural transitions in confined gallium

    International Nuclear Information System (INIS)

    MacDonald, Kevin Francis

    2002-01-01

    An ultra-high-vacuum system has been constructed to facilitate atomic-beam deposition of gallium on cryogenically cooled substrates, including optical fibre tips. Alongside this, a fibre-optic pump-probe diagnostic system, based on semiconductor lasers, has been developed to perform in-situ measurements of the linear and transient nonlinear optical properties of gallium nanostructures, both during and after deposition. This unique combination of deposition and optical diagnostic techniques has provided a new means of studying the growth and optical characteristics of gallium nanostructures under highly controlled conditions. The linear and nonlinear optical properties of a new material structure, namely gallium/glass interfaces prepared by ultrafast pulsed laser deposition (UPLD), have been studied for the first time. The reflectivity characteristics of these high-quality interfaces were measured under varying conditions of temperature and light intensity at 810 nm: At temperatures several degrees below gallium's melting point T m , excitation intensities of just a few kW.cm -2 were seen to induce reflectivity changes of more than 30%. Experiments performed with a nanosecond optical parametric oscillator have illustrated that UPLD gallium/silica interfaces show a nonlinear response to optical excitation in the 440-680 nm wavelength range: Fluences of less than 10 mJ.cm -2 were seen to induce reflectivity changes of up to 35%, even at temperatures 15 deg below T m . It has been found that low power (17 μW average) laser illumination of cryogenically cooled substrates during atomic-beam deposition of gallium leads to the formation of uniformly sized gallium nanoparticles. This phenomenon is believed to be the result of a non-thermal light-assisted particle self-assembly process. Gallium nanoparticles have been seen to show a strongly temperature-dependent nonlinear response to low intensity, infrared (1550 nm) optical excitation: 1 μs pulses with peak intensities

  7. Nitriding behavior of Ni and Ni-based binary alloys

    Energy Technology Data Exchange (ETDEWEB)

    Fonovic, Matej

    2015-01-15

    Gaseous nitriding is a prominent thermochemical surface treatment process which can improve various properties of metallic materials such as mechanical, tribological and/or corrosion properties. This process is predominantly performed by applying NH{sub 3}+H{sub 2} containing gas atmospheres serving as the nitrogen donating medium at temperatures between 673 K and 873 K (400 C and 600 C). NH{sub 3} decomposes at the surface of the metallic specimen and nitrogen diffuses into the surface adjacent region of the specimen whereas hydrogen remains in the gas atmosphere. One of the most important parameters characterizing a gaseous nitriding process is the so-called nitriding potential (r{sub N}) which determines the chemical potential of nitrogen provided by the gas phase. The nitriding potential is defined as r{sub N} = p{sub NH{sub 3}}/p{sub H{sub 2}{sup 3/2}} where p{sub NH{sub 3}} and p{sub H{sub 2}} are the partial pressures of the NH{sub 3} and H{sub 2} in the nitriding atmosphere. In contrast with nitriding of α-Fe where the nitriding potential is usually in the range between 0.01 and 1 atm{sup -1/2}, nitriding of Ni and Ni-based alloys requires employing nitriding potentials higher than 100 atm{sup -1/2} and even up to ∞ (nitriding in pure NH{sub 3} atmosphere). This behavior is compatible with decreased thermodynamic stability of the 3d-metal nitrides with increasing atomic number. Depending on the nitriding conditions (temperature, nitriding potential and treatment time), different phases are formed at the surface of the Ni-based alloys. By applying very high nitriding potential, formation of hexagonal Ni{sub 3}N at the surface of the specimen (known as external nitriding) leads to the development of a compound layer, which may improve tribological properties. Underneath the Ni{sub 3}N compound layer, two possibilities exist: (i) alloying element precipitation within the nitrided zone (known as internal nitriding) and/or (ii) development of metastable and

  8. Boron nitride - Composition, optical properties, and mechanical behavior

    Science.gov (United States)

    Pouch, John J.; Alterovitz, Samuel A.; Miyoshi, Kazuhisa; Warner, Joseph D.

    1987-01-01

    A low energy ion beam deposition technique was used to grow boron nitride films on quartz, germanium, silicon, gallium arsenide, and indium phosphate. The film structure was amorphous with evidence of a hexagonal phase. The peak boron concentration was 82 at. percent. The carbon and oxygen impurities were in the 5 to 8 at. percent range. Boron-nitrogen and boron-boron bonds were revealed by X-ray photoelectron spectroscopy. The index of refraction varied from 1.65 to 1.67 for films deposited on III-V compound semiconductors. The coefficient of friction for boron nitride in sliding contact with diamond was less than 0.1. The substrate was silicon.

  9. Boron nitride: Composition, optical properties and mechanical behavior

    Science.gov (United States)

    Pouch, John J.; Alterovitz, Samuel A.; Miyoshi, Kazuhisa; Warner, Joseph D.

    1987-01-01

    A low energy ion beam deposition technique was used to grow boron nitride films on quartz, germanium, silicon, gallium arsenide, and indium phosphate. The film structure was amorphous with evidence of a hexagonal phase. The peak boron concentration was 82 at %. The carbon and oxygen impurities were in the 5 to 8 at % range. Boron-nitrogen and boron-boron bonds were revealed by X-ray photoelectron spectroscopy. The index of refraction varied from 1.65 to 1.67 for films deposited on III-V compound semiconductors. The coefficient of friction for boron nitride in sliding contact with diamond was less than 0.1. The substrate was silicon.

  10. Microstructure and antibacterial properties of microwave plasma nitrided layers on biomedical stainless steels

    International Nuclear Information System (INIS)

    Lin, Li-Hsiang; Chen, Shih-Chung; Wu, Ching-Zong; Hung, Jing-Ming; Ou, Keng-Liang

    2011-01-01

    Nitriding of AISI 303 austenitic stainless steel using microwave plasma system at various temperatures was conducted in the present study. The nitrided layers were characterized via scanning electron microscopy, glancing angle X-ray diffraction, transmission electron microscopy and Vickers microhardness tester. The antibacterial properties of this nitrided layer were evaluated. During nitriding treatment between 350 deg. C and 550 deg. C, the phase transformation sequence on the nitrided layers of the alloys was found to be γ → (γ + γ N ) → (γ + α + CrN). The analytical results revealed that the surface hardness of AISI 303 stainless steel could be enhanced with the formation of γ N phase in nitriding process. Antibacterial test also demonstrated the nitrided layer processed the excellent antibacterial properties. The enhanced surface hardness and antibacterial properties make the nitrided AISI 303 austenitic stainless steel to be one of the essential materials in the biomedical applications.

  11. Superconducting structure with layers of niobium nitride and aluminum nitride

    Science.gov (United States)

    Murduck, J.M.; Lepetre, Y.J.; Schuller, I.K.; Ketterson, J.B.

    1989-07-04

    A superconducting structure is formed by depositing alternate layers of aluminum nitride and niobium nitride on a substrate. Deposition methods include dc magnetron reactive sputtering, rf magnetron reactive sputtering, thin-film diffusion, chemical vapor deposition, and ion-beam deposition. Structures have been built with layers of niobium nitride and aluminum nitride having thicknesses in a range of 20 to 350 Angstroms. Best results have been achieved with films of niobium nitride deposited to a thickness of approximately 70 Angstroms and aluminum nitride deposited to a thickness of approximately 20 Angstroms. Such films of niobium nitride separated by a single layer of aluminum nitride are useful in forming Josephson junctions. Structures of 30 or more alternating layers of niobium nitride and aluminum nitride are useful when deposited on fixed substrates or flexible strips to form bulk superconductors for carrying electric current. They are also adaptable as voltage-controlled microwave energy sources. 8 figs.

  12. Method of activating an article of passive ferrous or non-ferrous metal prior to carburising, nitriding and /or nitrocarburising

    DEFF Research Database (Denmark)

    2011-01-01

    , nitrided or nitrocarburised in shorter time at lower temperature and resulting superior mechanical properties compared with non-activated articles and even articles of stainless steel, nickel alloy, cobalt alloy or titanium based material can be carburised, nitrided or nitrocarburised....

  13. Local Heating with Lithographically Fabricated Plasmonic Titanium Nitride Nanoparticles

    DEFF Research Database (Denmark)

    Guler, Urcan; Ndukaife, Justus C.; Naik, Gururaj V.

    2013-01-01

    Titanium nitride is considered a promising alternative plasmonic material and is known to exhibit localized surface plasmon resonances within the near-infrared biological transparency window. Here, local heating efficiencies of disk-shaped nanoparticles made of titanium nitride and gold are compa......Titanium nitride is considered a promising alternative plasmonic material and is known to exhibit localized surface plasmon resonances within the near-infrared biological transparency window. Here, local heating efficiencies of disk-shaped nanoparticles made of titanium nitride and gold...... are compared in the visible and near-infrared regions numerically and experimentally with samples fabricated using e-beam lithography. Results show that plasmonic titanium nitride nanodisks are efficient local heat sources and outperform gold nanodisks in the biological transparency window, dispensing the need...

  14. Monolithic Gyroidal Mesoporous Mixed Titanium–Niobium Nitrides

    Science.gov (United States)

    2015-01-01

    Mesoporous transition metal nitrides are interesting materials for energy conversion and storage applications due to their conductivity and durability. We present ordered mixed titanium–niobium (8:2, 1:1) nitrides with gyroidal network structures synthesized from triblock terpolymer structure-directed mixed oxides. The materials retain both macroscopic integrity and mesoscale ordering despite heat treatment up to 600 °C, without a rigid carbon framework as a support. Furthermore, the gyroidal lattice parameters were varied by changing polymer molar mass. This synthesis strategy may prove useful in generating a variety of monolithic ordered mesoporous mixed oxides and nitrides for electrode and catalyst materials. PMID:25122534

  15. Gallium antimonide texturing for enhanced light extraction from infrared optoelectronics devices

    Directory of Open Access Journals (Sweden)

    Ella Wassweiler

    2016-06-01

    Full Text Available The use of gallium antimonide (GaSb is increasing, especially for optoelectronic devices in the infrared wavelengths. It has been demonstrated in gallium nitride (GaN devices operating at ultraviolet (UV wavelengths, that surface textures increase the overall device efficiency. In this work, we fabricated eight different surface textures in GaSb to be used in enhancing efficiency in infrared wavelength devices. Through chemical etching with hydrofluoric acid, hydrogen peroxide, and tartaric acid we characterize the types of surface textures formed and the removal rate of entire layers of GaSb. Through optimization of the etching recipes we lower the reflectivity from 35.7% to 1% at 4 μm wavelength for bare and textured GaSb, respectively. In addition, we simulate surface textures using ray optics in finite element method solver software to provide explanation of our experimental findings.

  16. Common features of gallium perovskites

    NARCIS (Netherlands)

    Aleksiyko, R; Berkowski, M; Byszewski, P; Dabrowski, B; Diduszko, R; Fink-Finowicki, J; Vasylechko, LO

    2001-01-01

    The Czochralski and floating zone methods have been used to grow single crystals of gallium perovskites solid solutions with rare earth elements La, Pr, Nd, Sm and with Sr. The structure of the crystals has been investigated by powder X-ray, synchrotron radiation and neutron diffraction methods over

  17. Zirconia doped silicon nitride ceramics

    International Nuclear Information System (INIS)

    Ekstroem, T.; Falk, L.K.L.; Knutson-Wedel, E.M.

    1992-01-01

    This presentation is concerned with the value added to silicon nitride ceramics by doping with smaller amounts of zirconia. The effects which the different sintering additives ZrO 2 , Y 2 O 3 stabilized ZrO 2 , Y 2 O 3 , Al 2 O 3 and AIN have upon densification, α- to β-Si 3 N 4 phase transformation and final microstructure are discussed. Silicon nitride ceramics containing these additives have been formed either by pressureless sintering or by hot isostatic pressing (HIP) at temperatures in the range 1550 to 1775 deg C. The fine scale microstructures of the densified materials, characterized by analytical electron microscopy and X-ray diffractometry, have been related to mechanical properties viz. strength, hardness and indentation fracture toughness. The most pronounced value added by ZrO 2 doping is that a properly adjusted combination of sintering aids makes it possible to substantially reduce the volume fraction of residual intergranular glass through formation of crystalline ZrO 2 (Y 2 O 3 ) solid solutions. This behaviours opens the possibility of developing new silicon nitride ceramics for high temperature applications. 25 refs., 4 figs

  18. Biocompatible nano-gallium/hydroxyapatite nanocomposite with antimicrobial activity.

    Science.gov (United States)

    Kurtjak, Mario; Vukomanović, Marija; Kramer, Lovro; Suvorov, Danilo

    2016-11-01

    Intensive research in the area of medical nanotechnology, especially to cope with the bacterial resistance against conventional antibiotics, has shown strong antimicrobial action of metallic and metal-oxide nanomaterials towards a wide variety of bacteria. However, the important remaining problem is that nanomaterials with highest antibacterial activity generally express also a high level of cytotoxicity for mammalian cells. Here we present gallium nanoparticles as a new solution to this problem. We developed a nanocomposite from bioactive hydroxyapatite nanorods (84 wt %) and antibacterial nanospheres of elemental gallium (16 wt %) with mode diameter of 22 ± 11 nm. In direct comparison, such nanocomposite with gallium nanoparticles exhibited better antibacterial properties against Pseudomonas aeruginosa and lower in-vitro cytotoxicity for human lung fibroblasts IMR-90 and mouse fibroblasts L929 (efficient antibacterial action and low toxicity from 0.1 to 1 g/L) than the nanocomposite of hydroxyapatite and silver nanoparticles (efficient antibacterial action and low toxicity from 0.2 to 0.25 g/L). This is the first report of a biomaterial composite with gallium nanoparticles. The observed strong antibacterial properties and low cytotoxicity make the investigated material promising for the prevention of implantation-induced infections that are frequently caused by P. aeruginosa.

  19. Ion nitriding of aluminium

    International Nuclear Information System (INIS)

    Fitz, T.

    2002-09-01

    The present study is devoted to the investigation of the mechanism of aluminium nitriding by a technique that employs implantation of low-energy nitrogen ions and diffusional transport of atoms. The nitriding of aluminium is investigated, because this is a method for surface modification of aluminium and has a potential for application in a broad spectrum of fields such as automobile, marine, aviation, space technologies, etc. However, at present nitriding of aluminium does not find any large scale industrial application, due to problems in the formation of stoichiometric aluminium nitride layers with a sufficient thickness and good quality. For the purposes of this study, ion nitriding is chosen, as an ion beam method with the advantage of good and independent control over the process parameters, which thus can be related uniquely to the physical properties of the resulting layers. Moreover, ion nitriding has a close similarity to plasma nitriding and plasma immersion ion implantation, which are methods with a potential for industrial application. (orig.)

  20. Preparation and characterization of morph-genetic aluminum nitride/carbon composites from filter paper

    International Nuclear Information System (INIS)

    Wang Wei; Xue Tao; Jin Zhihao; Qiao Guanjun

    2008-01-01

    Morph-genetic aluminum nitride/carbon composites with cablelike structure were prepared from filter paper template through the surface sol-gel process and carbothermal nitridation reaction. The resulting materials have a hierarchical structure originating from the morphology of cellulose paper. The aluminum nitride/carbon composites have the core-shell microstructure, the core is graphitic carbon, and the shell is aluminum nitride nanocoating formed by carbothermal nitridation reduction of alumina with the interfacial carbon in nitrogen atmosphere. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and transmission electron microscope were employed to characterize the structural morphology and phase compositions of the final products

  1. Running droplets of gallium from evaporation of gallium arsenide.

    Science.gov (United States)

    Tersoff, J; Jesson, D E; Tang, W X

    2009-04-10

    High-temperature annealing of gallium arsenide in vacuum causes excess evaporation of arsenic, with accumulation of gallium as liquid droplets on the surface. Using real-time in situ surface electron microscopy, we found that these droplets spontaneously run across the crystal surface. Running droplets have been seen in many systems, but they typically require special surface preparation or gradient forces. In contrast, we show that noncongruent evaporation automatically provides a driving force for running droplets. The motion is predicted and observed to slow and stop near a characteristic temperature, with the speed increasing both below and above this temperature. The same behavior is expected to occur during the evaporation of similar III-V semiconductors such as indium arsenide.

  2. The Effect of Polymer Char on Nitridation Kinetics of Silicon

    Science.gov (United States)

    Chan, Rickmond C.; Bhatt, Ramakrishna T.

    1994-01-01

    Effects of polymer char on nitridation kinetics of attrition milled silicon powder have been investigated from 1200 to 1350 C. Results indicate that at and above 1250 C, the silicon compacts containing 3.5 wt percent polymer char were fully converted to Si3N4 after 24 hr exposure in nitrogen. In contrast, the silicon compacts without polymer char could not be fully converted to Si3N4 at 1350 C under similar exposure conditions. At 1250 and 1350 C, the silicon compacts with polymer char showed faster nitridation kinetics than those without the polymer char. As the polymer char content is increased, the amount of SiC in the nitrided material is also increased. By adding small amounts (approx. 2.5 wt percent) of NiO, the silicon compacts containing polymer char can be completely nitrided at 1200 C. The probable mechanism for the accelerated nitridation of silicon containing polymer char is discussed.

  3. Gallium-67 scintigraphy and the Heart

    International Nuclear Information System (INIS)

    Garayt, D.

    1987-01-01

    Although gallium-67 was initially used for tumor imaging, clinical studies suggested its potential use as a method of detecting occult inflammatory lesions. The demonstration of diffuse myocardial uptake of gallium-67 during Lyme disease myocarditis is consistent with a pattern of diffuse myocarditis as seen in sarcoid myocarditis. Two cases are presented. A critical review of the various applications of gallium-67 scintigraphy to myocardium investigation is carried out [fr

  4. Conducting metal oxide and metal nitride nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    DiSalvo, Jr., Francis J.; Subban, Chinmayee V.

    2017-12-26

    Conducting metal oxide and nitride nanoparticles that can be used in fuel cell applications. The metal oxide nanoparticles are comprised of for example, titanium, niobium, tantalum, tungsten and combinations thereof. The metal nitride nanoparticles are comprised of, for example, titanium, niobium, tantalum, tungsten, zirconium, and combinations thereof. The nanoparticles can be sintered to provide conducting porous agglomerates of the nanoparticles which can be used as a catalyst support in fuel cell applications. Further, platinum nanoparticles, for example, can be deposited on the agglomerates to provide a material that can be used as both an anode and a cathode catalyst support in a fuel cell.

  5. Boron nitride nanosheets reinforced glass matrix composites

    Czech Academy of Sciences Publication Activity Database

    Saggar, Richa; Porwal, H.; Tatarko, P.; Dlouhý, Ivo; Reece, M. J.

    2015-01-01

    Roč. 114, SEP (2015), S26-S32 ISSN 1743-6753 R&D Projects: GA MŠk(CZ) 7AMB14SK155 EU Projects: European Commission(XE) 264526 Institutional support: RVO:68081723 Keywords : Boron nitride nanosheets * Borosilicate glass * Mechanical properties Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 1.162, year: 2015

  6. Doped Aluminum Gallium Arsenide (AlGaAs)/Gallium Arsenide (GaAs) Photoconductive Semiconductor Switch (PCSS) Fabrication

    Science.gov (United States)

    2016-09-27

    ARL-TR-7819 ● SEP 2016 US Army Research Laboratory Doped Aluminum Gallium Arsenide (AlGaAs)/Gallium Arsenide (GaAs...Laboratory Doped Aluminum Gallium Arsenide (AlGaAs)/Gallium Arsenide (GaAs) Photoconductive Semiconductor Switch (PCSS) Fabrication by...Report 3. DATES COVERED (From - To) January 2016–September 2016 4. TITLE AND SUBTITLE Doped Aluminum Gallium Arsenide (AlGaAs)/Gallium Arsenide (GaAs

  7. Thermodynamics, kinetics and process control of nitriding

    DEFF Research Database (Denmark)

    Mittemeijer, Eric J.; Somers, Marcel A. J.

    1997-01-01

    As a prerequisite for the predictability of properties obtained by a nitriding treatment of iron based workpieces, the relation between the process parameters and the composition and structure of the surface layer produced must be known. At present, even the description of thermodynamic equilibrium...... of the International Federation for Heat Treatment and Surface Engineering held in Brighton, UK on 1-5 September 1996. (C) 1997 The Institute of Materials......., the nitriding result is determined largely by kinetics. Nitriding kinetics are shown to be characterised by local near equilibria and stationary states at surfaces and interfaces, and the diffusion coefficient of nitrogen in the various phases, for which new data are presented. The necessary background...

  8. Efficacy of gallium in tooth loss prevention

    Directory of Open Access Journals (Sweden)

    Aleksić Milena D.

    2016-01-01

    Full Text Available Introduction: Over the past three decades, gallium compounds have gained importance in medicine. Radioactive gallium and stable gallium nitrate are used as diagnostic and therapeutic agents in cancer and disorders of calcium and bone metabolism. In addition, gallium compounds have displayed anti inflammatory and immunosuppressive activity in animal models of human diseases. More recent studies have shown that gallium compounds may also function as antimicrobial agents. In the review, the potential application of gallium in the future treatment of periodontitis and prevention of tooth loss will be discussed. Gingival inflammation, bacterial infection, alveolar bone destruction and subsequent tooth loss are characteristic features of periodontal disease. Surgical techniques, mechanical debridement of the denuded root surface, and local or systemic application of antimicrobial agents are currently used treatments for periodontitis. However, the development of antibiotic resistance in bacteria has prompted a great need for new and alternative treatment methods for infection. Conclusion: The potential anti-periodontitis benefits of gallium are related to eradicating infection due to bacterial biofilms, increasing bone deposition and downregulating unwanted immune responses. Adjunctive use of gallium laser therapy with mechanical instrumentation in combination with gallium-containing gingival gels, toothpastes and mouth rinses may represent the final solutions for tooth loss prevention.

  9. Contact formation in gallium arsenide solar cells

    Science.gov (United States)

    Weizer, Victor G.; Fatemi, Navid S.

    1988-01-01

    Gold and gold-based alloys, commonly used as solar cell contact materials, are known to react readily with gallium arsenide. Experiments were performed to identify the mechanisms involved in these GaAs-metal interactions. It is shown that the reaction of GaAs with gold takes place via a dissociative diffusion process. It is shown further that the GaAs-metal reaction rate is controlled to a very great extent by the condition of the free surface of the contact metal, an interesting example of which is the previously unexplained increase in the reaction rate that has been observed for samples annealed in a vacuum environment as compared to those annealed in a gaseous ambient. A number of other hard-to-explain observations, such as the low-temperature formation of voids in the gold lattice and crystallite growth on the gold surface, are explained by invoking this mechanism.

  10. The interaction of gold with gallium arsenide

    Science.gov (United States)

    Weizer, Victor G.; Fatemi, Navid S.

    1988-01-01

    Gold and gold-based alloys, commonly used as solar-cell contact materials, are known to react readily with gallium arsenide. Experiments designed to identify the mechanisms involved in these GaAs-metal interactions have yielded several interesting results. It is shown that the reaction of GaAs with gold takes place via a dissociative diffusion process. It is shown further that the GaAs-metal reaction rate is controlled to a very great extent by the condition of the free surface of the contact metal, an interesting example of which is the previously unexplained increase in the reaction rate that has been observed for samples annealed in a vacuum environment as compared to those annealed in a gaseous ambient. A number of other hard-to-explain observations, such as the low-temperature formation of voids in the gold lattice and crystallite growth on the gold surface, are also explained by invoking this mechanism.

  11. Cavity optomechanics in gallium phosphide microdisks

    International Nuclear Information System (INIS)

    Mitchell, Matthew; Barclay, Paul E.; Hryciw, Aaron C.

    2014-01-01

    We demonstrate gallium phosphide (GaP) microdisk optical cavities with intrinsic quality factors >2.8 × 10 5 and mode volumes 3 , and study their nonlinear and optomechanical properties. For optical intensities up to 8.0 × 10 4 intracavity photons, we observe optical loss in the microcavity to decrease with increasing intensity, indicating that saturable absorption sites are present in the GaP material, and that two-photon absorption is not significant. We observe optomechanical coupling between optical modes of the microdisk around 1.5 μm and several mechanical resonances, and measure an optical spring effect consistent with a theoretically predicted optomechanical coupling rate g 0 /2π∼30 kHz for the fundamental mechanical radial breathing mode at 488 MHz

  12. Boron Nitride Nanotubes

    Science.gov (United States)

    Smith, Michael W. (Inventor); Jordan, Kevin (Inventor); Park, Cheol (Inventor)

    2012-01-01

    Boron nitride nanotubes are prepared by a process which includes: (a) creating a source of boron vapor; (b) mixing the boron vapor with nitrogen gas so that a mixture of boron vapor and nitrogen gas is present at a nucleation site, which is a surface, the nitrogen gas being provided at a pressure elevated above atmospheric, e.g., from greater than about 2 atmospheres up to about 250 atmospheres; and (c) harvesting boron nitride nanotubes, which are formed at the nucleation site.

  13. Gallium-68 in Medical Imaging.

    Science.gov (United States)

    Martiniova, Lucia; Palatis, Louis De; Etchebehere, Elba; Ravizzini, Gregory

    2016-01-01

    Over the past several years, Positron Emission Tomography (PET) imaging agents labeled with ;68Gallium (68Ga) have undergone a significant increase in clinical utilization. 68Ga is conveniently produced from a germanium-68/gallium-68 (68Ge/68Ga) generator. Because of the compact size and ease of use of the generator, 68Ga labeled compounds may be more cost-effective than PET radioisotopes that are cyclotron-produced. The convenient half-life of 68Ga (T1/2=68 min) provides sufficient radioactivity for various PET imaging applications, while delivering acceptable radiation doses to patients. This chapter summarizes the emerging clinical utilization of 68Ga-based radiotracers in medical imaging. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  14. Materials Integration and Metamorphic Substrate Engineering from Silicon to Gallium Arsenide to Indium Phosphide for Advanced III-V/Silicon Photovoltaics

    Science.gov (United States)

    Carlin, Andrew M.

    Lattice-mismatched epitaxy in the III-V compound semiconductor system based on III-AsP and related alloys are of enormous importance, and considerable research interest, for many years. The reason is straightforward if one considers the limitations placed on available materials properties for devices dictated by lattice matching to the dominant substrate technologies - Si, GaAs (and/or Ge) and InP. For III-V epitaxy, the lattice constants of these substrates have defined a generation or more of device advances since growth of heterostructures possessing the same equilibrium lattice constants as the substrate yields essentially defect-free (specifically extended defect-free) materials and devices. Removing the restriction of lattice matching to current substrate technology opens a rich spectrum of bandgaps, bandgap combinations, conduction and valence band offsets, etc., that are desirable and exploitable for advancing device technologies for new functionality and greater performance. However successful exploitation of these properties requires mitigation of a variety of extended defects that result from the lattice mismatch between substrate and epitaxial heterostructures. A well known method to achieve this solution is through the use of compositionally (lattice constant-graded) buffer interlayers, in which the equilibrium lattice constants of interlayers are slowly altered by controlled changes in layer composition so that the mismatch strain between the initial substrate and the final device layers is spread across a thickness of buffer. The research accomplished has yielded success for both lattice constant ranges Si - GaAs and GaAs - InP. For the Si - GaAs system, a three step GaP nucleation process on Si has been developed and demonstrated, which maintains total avoidance of creating coalescence-related defects such as antiphase domains and stacking faults resulting from the initial III-V/IV interfaces while reducing overall threading dislocation density by

  15. ASSESSMENT OF GALLIUM OXIDE TECHNOLOGY

    Science.gov (United States)

    2017-08-01

    heterojunction to implement p-n junctions. This would bring a large number of new device types into play, especially for power electronics where Ga2O3 is...AFRL-RY-WP-TR-2017-0167 ASSESSMENT OF GALLIUM OXIDE TECHNOLOGY Burhan Bayraktaroglu Devices for Sensing Branch Aerospace... Devices for Sensing Branch Aerospace Component & Subsystems Division *//Signature// ROSS W. DETTMER Chief Devices for Sensing Branch

  16. Anisotropic Hexagonal Boron Nitride Nanomaterials - Synthesis and Applications

    Energy Technology Data Exchange (ETDEWEB)

    Han,W.Q.

    2008-08-01

    Boron nitride (BN) is a synthetic binary compound located between III and V group elements in the Periodic Table. However, its properties, in terms of polymorphism and mechanical characteristics, are rather close to those of carbon compared with other III-V compounds, such as gallium nitride. BN crystallizes into a layered or a tetrahedrally linked structure, like those of graphite and diamond, respectively, depending on the conditions of its preparation, especially the pressure applied. Such correspondence between BN and carbon readily can be understood from their isoelectronic structures [1, 2]. On the other hand, in contrast to graphite, layered BN is transparent and is an insulator. This material has attracted great interest because, similar to carbon, it exists in various polymorphic forms exhibiting very different properties; however, these forms do not correspond strictly to those of carbon. Crystallographically, BN is classified into four polymorphic forms: Hexagonal BN (h-BN) (Figure 1(b)); rhombohedral BN (r-BN); cubic BN (c-BN); and wurtzite BN (w-BN). BN does not occur in nature. In 1842, Balmain [3] obtained BN as a reaction product between molten boric oxide and potassium cyanide under atmospheric pressure. Thereafter, many methods for its synthesis were reported. h-BN and r-BN are formed under ambient pressure. c-BN is synthesized from h-BN under high pressure at high temperature while w-BN is prepared from h-BN under high pressure at room temperature [1]. Each BN layer consists of stacks of hexagonal plate-like units of boron and nitrogen atoms linked by SP{sup 2} hybridized orbits and held together mainly by Van der Waals force (Fig 1(b)). The hexagonal polymorph has two-layered repeating units: AA'AA'... that differ from those in graphite: ABAB... (Figure 1(a)). Within the layers of h-BN there is coincidence between the same phases of the hexagons, although the boron atoms and nitrogen atoms are alternatively located along the c

  17. Physics of wurtzite nitrides and oxides passport to devices

    CERN Document Server

    Gil, Bernard

    2014-01-01

    This book gives a survey of the current state of the art of a special class of nitrides semiconductors, Wurtzite Nitride and Oxide Semiconductors. It includes properties, growth and applications. Research in the area of nitrides semiconductors is still booming although some basic materials sciences issues were solved already about 20 years ago. With the advent of modern technologies and the successful growth of nitride substrates, these materials currently experience a second birth. Advanced new applications like light-emitters, including UV operating LEDs, normally on and normally off high frequency operating transistors are expected. With progress in clean room technology, advanced photonic and quantum optic applications are envisioned in a close future. This area of research is fascinating for researchers and students in materials science, electrical engineering, chemistry, electronics, physics and biophysics. This book aims to be the ad-hoc instrument to this active field of research.

  18. Density Functional Theory Study on Defect Feature of AsGaGaAs in Gallium Arsenide

    Directory of Open Access Journals (Sweden)

    Deming Ma

    2015-01-01

    Full Text Available We investigate the defect feature of AsGaGaAs defect in gallium arsenide clusters in detail by using first-principles calculations based on the density functional theory (DFT. Our calculations reveal that the lowest donor level of AsGaGaAs defect on the gallium arsenide crystal surface is 0.85 eV below the conduction band minimum, while the lowest donor level of the AsGaGaAs defect inside the gallium arsenide bulk is 0.83 eV below the bottom of the conduction band, consistent with gallium arsenide EL2 defect level of experimental value (Ec-0.82 eV. This suggests that AsGaGaAs defect is one of the possible gallium arsenide EL2 deep-level defects. Moreover, our results also indicate that the formation energies of internal AsGaGaAs and surface AsGaGaAs defects are predicted to be around 2.36 eV and 5.54 eV, respectively. This implies that formation of AsGaGaAs defect within the crystal is easier than that of surface. Our results offer assistance in discussing the structure of gallium arsenide deep-level defect and its effect on the material.

  19. Photonics of 2D materials

    Science.gov (United States)

    Zhang, Han; Wang, Junzhuan; Hasan, Tawfique; Bao, Qiaoliang

    2018-01-01

    The emergence of graphene and graphene-like two dimensional (2D) materials has attracted a strong interest from the photonics community in recent decade. Apart from zero-gap graphene, insulating hexagonal boron nitride and semiconducting transition metal dichalcogenides and phosphorene/black phosphorus are being intensively investigated because of their fascinating photonic and optoelectronic properties. Compared to traditional bulk photonic materials such as Gallium Arsenide (GaAs) and Silicon (Si), 2D materials exhibit many unique properties important for device applications in nanophotonics. Firstly, quantum confinement in the direction perpendicular to 2D plane leads to novel electronic and optical features that are distinctively different from their bulk counterparts. Secondly, their surfaces are naturally passivated without any dangling bonds making them readily compatible for integration with photonic structures such as waveguides and cavities. It is also possible to construct vertical hetero-structures by using different 2D materials, without considering lattice mismatch issues that are common in bulk semiconductors. This is because the 2D layers with different lattice constants in heterostructures are only weakly bounded by van der Waals force. Thirdly, despite being atomically thin, many 2D materials interact very strongly with light.

  20. A comparative study of nitride purity and Am fabrication losses in PuN materials by the powder and internal gelation production routes

    Energy Technology Data Exchange (ETDEWEB)

    Hedberg, Marcus, E-mail: marhed@chalmers.se; Ekberg, Christian

    2016-12-15

    Fabrication of plutonium containing fuels through the internal gelation method has mostly been studied in mixed metal systems such as U, Pu or Zr,Pu. In this work production of undiluted PuN has been performed by carbothermal reduction on both oxide powder and Pu microspheres produced by the internal gelation method. Nitride purities reached using the different methods have been studied together with final densities achieved during pellet fabrication as well as losses of ingrown Am during the different production steps. Formation of Pu microspheres was successfully performed using the internal gelation method, although extensive microsphere fracturing occurred during thermal treatment. Final densities of PuN pellets produced by cold pressing and sintering reached 70–80% of theoretical density. Am losses during the carbothermal reduction step was on average about 3.7%. After sintering about 11% of Am was lost in total through the entire production process if sintering in N{sub 2} + 5% H{sub 2} atmosphere while about 50% of the Am in total was lost when using Ar as sintering atmosphere. - Highlights: • Internal gelation Pu based sols was performed. • Nitride formation by carbothermal reduction on Pu microspheres and powders was performed. • Pelletization and sintering of pellets was performed. • Am losses were measured throughout the production steps.

  1. Gallium 67 uptake in thymic rebound

    International Nuclear Information System (INIS)

    Hurst, R.; Sabio, H.; Teates, C.D.

    1988-01-01

    We have reported a case of localized thymic enlargement and uptake of gallium 67 in a child who had received antineoplastic chemotherapy. The enlarged thymus showed normal histology, a picture consistent with thymic rebound after nonspecific stress. This case further demonstrates the need to consider thymic rebound as a cause of gallium 67 uptake in children with neoplastic diseases

  2. Properties of minor actinide nitrides

    International Nuclear Information System (INIS)

    Takano, Masahide; Itoh, Akinori; Akabori, Mitsuo; Arai, Yasuo; Minato, Kazuo

    2004-01-01

    The present status of the research on properties of minor actinide nitrides for the development of an advanced nuclear fuel cycle based on nitride fuel and pyrochemical reprocessing is described. Some thermal stabilities of Am-based nitrides such as AmN and (Am, Zr)N were mainly investigated. Stabilization effect of ZrN was cleary confirmed for the vaporization and hydrolytic behaviors. New experimental equipments for measuring thermal properties of minor actinide nitrides were also introduced. (author)

  3. Modelling of the modulation properties of arsenide and nitride VCSELs

    Science.gov (United States)

    Wasiak, Michał; Śpiewak, Patrycja; Moser, Philip; Gebski, Marcin; Schmeckebier, Holger; Sarzała, Robert P.; Lott, James A.

    2017-02-01

    In this paper, using our model of capacitance in vertical-cavity surface-emitting lasers (VCSELs), we analyze certain differences between an oxide-confined arsenide VCSEL emitting in the NIR region, and a nitride VCSEL emitting violet radiation. In the nitride laser its high differential resistance, caused partially by the low conductivity of p-type GaN material and the bottom contact configuration, is one of the main reasons why the nitride VCSEL has much worse modulation properties than the arsenide VCSEL. Using the complicated arsenide structure, we also analyze different possible ways of constructing the laser's equivalent circuit.

  4. Gallium plasmonics: deep subwavelength spectroscopic imaging of single and interacting gallium nanoparticles.

    Science.gov (United States)

    Knight, Mark W; Coenen, Toon; Yang, Yang; Brenny, Benjamin J M; Losurdo, Maria; Brown, April S; Everitt, Henry O; Polman, Albert

    2015-02-24

    Gallium has recently been demonstrated as a phase-change plasmonic material offering UV tunability, facile synthesis, and a remarkable stability due to its thin, self-terminating native oxide. However, the dense irregular nanoparticle (NP) ensembles fabricated by molecular-beam epitaxy make optical measurements of individual particles challenging. Here we employ hyperspectral cathodoluminescence (CL) microscopy to characterize the response of single Ga NPs of various sizes within an irregular ensemble by spatially and spectrally resolving both in-plane and out-of-plane plasmonic modes. These modes, which include hybridized dipolar and higher-order terms due to phase retardation and substrate interactions, are correlated with finite difference time domain (FDTD) electrodynamics calculations that consider the Ga NP contact angle, substrate, and native Ga/Si surface oxidation. This study experimentally confirms previous theoretical predictions of plasmonic size-tunability in single Ga NPs and demonstrates that the plasmonic modes of interacting Ga nanoparticles can hybridize to produce strong hot spots in the ultraviolet. The controlled, robust UV plasmonic resonances of gallium nanoparticles are applicable to energy- and phase-specific applications such as optical memory, environmental remediation, and simultaneous fluorescence and surface-enhanced Raman spectroscopies.

  5. Gallium-67 citrate scan in extrapulmonary tuberculosis

    Energy Technology Data Exchange (ETDEWEB)

    Lin Wanyu [Taichung Veterans General Hospital (Taiwan). Dept. of Nuclear Medicine; Hsieh Jihfang [Chi-Mei Foundation Hospital, Tainan (Taiwan)

    1999-07-01

    Aim: Whole-body gallium scan was performed to evaluate the usefulness of gallium scan for detecting extrapulmonary tuberculosis (TB) lesions. Methods: Thirty-seven patients with extrapulmonary TB were included in this study. Four patients were found to have two lesions. Totally, 41 lesions were identified, including 19 TB arthritis, 8 spinal TB, 5 TB meningitis, 3 TB lymphadenopathy, 2 TB pericarditis, 1 TB peritonitis, 1 intestinal TB, 1 skin TB and 1 renal TB. Results: Of the 41 extrapulmonary TB lesions, gallium scan detected 32 lesions with a sensitivity of 78%. All the patients with TB meningitis showed negative gallium scan. When the five cases of TB meningitis were excluded, the detection sensitivity of gallium scan increased to 88.9% (32/36). Conclusion: Our data revealed that gallium scan is a convenient and useful method for evaluating extrapulmonary TB lesions other than TB-meningitis. We suggest that gallium scan be included in the clinical routine for patients with suspected extrapulmonary TB. (orig.) [German] Ziel: Es wurden Ganzkoerper-Gallium-Szintigramme angefertigt, um den Nutzen der Gallium-Szintigraphie zur Erfassung von extrapulmonalen Tuberkuloseherden (TB) zu erfassen. Methoden: 37 Patienten mit extrapulmonaler TB wurden eingeschlossen. 4 Patienten hatten 2 Laesionen. Insgesamt wurden 41 Laesionen identifiziert, hierunter 19 TB-Arthritis, 8 spinale TB, 5 TB-Meningitis, 3 TB-Lymphadenopathie, 2 TB-Perikarditis, 1 TB-Peritonitis, 1 intestinale TB, 1 Haut-TB und eine Nieren-TB. Ergebnisse: Von den 41 extrapulmonalen TB-Herden erfasste die Gallium-Szintigraphie 32 Herde mit einer Sensitivitaet von 78%. Alle Patienten mit TB-Meningitis zeigten einen negativen Gallium-Scan. Wenn die 5 Faelle mit TB-Meningitis ausgeschlossen wurden, stieg die Sensitivititaet der Gallium-Szintigraphie auf 88,9% (32/36). Schlussfolgerung: Die Daten zeigen, dass die Gallium-Szintigraphie eine einfache und nuetzliche Methode zur Erfassung extrapulmonaler TB-Herde ist

  6. Nitriding of high temperature alloys

    International Nuclear Information System (INIS)

    Kiparisov, S.S.; Levinskii, Yu.V.

    This book reviews the nitriding of refractory metals (Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W) and the mechanism involved in this process. Particular attention is paid to the diffusion aspects of nitriding. Application of nitriding to technological processes is also treated. Characteristics of solid solutions and phases in refractory metal-nitrogen systems are mentioned in the text

  7. Large grain gallium arsenide thin films

    Science.gov (United States)

    Chu, S. S.; Chu, T. L.; Firouzi, H.; Han, Y. X.; Chen, W. J.; Wang, Q. H.

    Polycrystalline gallium arsenide films deposited on tungsten/graphite substrates have been used for the fabrication of thin film solar cells. Gallium arsenide films deposited on foreign substrates of 10 microns or less thickness exhibit, in most cases, pronounced shunting effects due to grain boundaries. MOS solar cells of 9 sq cm area with an AM1 efficiency of 8.5 percent and p(+)/n/n(+) homojunction solar cells of 1 sq cm area with an AM1 efficiency of 8.8 percent have been prepared. However, in order to further improve the conversion efficiency before the development of effective passivation techniques, gallium arsenide films with large and uniform grain structure are necessary. The large grain gallium arsenide films have been prepared by using (1) the arsine treatment of a thin layer of molten gallium on the substrate surface and (2) the recrystallized germanium films on tungsten/graphite as substrates.

  8. Plasmonic spectral tunability of conductive ternary nitrides

    Energy Technology Data Exchange (ETDEWEB)

    Kassavetis, S.; Patsalas, P., E-mail: ppats@physics.auth.gr [Department of Physics, Aristotle University of Thessaloniki, GR-54124 Thessaloniki (Greece); Bellas, D. V.; Lidorikis, E. [Department of Materials Science and Engineering, University of Ioannina, GR-45110 Ioannina (Greece); Abadias, G. [Institut Pprime, Département Physique et Mécanique des Matériaux, Université de Poitiers-CNRS-ENSMA, 86962 Chasseneuil-Futuroscope (France)

    2016-06-27

    Conductive binary transition metal nitrides, such as TiN and ZrN, have emerged as a category of promising alternative plasmonic materials. In this work, we show that ternary transition metal nitrides such as Ti{sub x}Ta{sub 1−x}N, Ti{sub x}Zr{sub 1−x}N, Ti{sub x}Al{sub 1−x}N, and Zr{sub x}Ta{sub 1−x}N share the important plasmonic features with their binary counterparts, while having the additional asset of the exceptional spectral tunability in the entire visible (400–700 nm) and UVA (315–400 nm) spectral ranges depending on their net valence electrons. In particular, we demonstrate that such ternary nitrides can exhibit maximum field enhancement factors comparable with gold in the aforementioned broadband range. We also critically evaluate the structural features that affect the quality factor of the plasmon resonance and we provide rules of thumb for the selection and growth of materials for nitride plasmonics.

  9. Micro-crack detection in high-performance cementitious materials

    DEFF Research Database (Denmark)

    Lura, Pietro; Guang, Ye; Tanaka, Kyoji

    2005-01-01

    aggregate size. Gallium intrusion of the cracks and subsequent examination by electron probe micro analysis, EPMA, are used to identify the cracks. The gallium intrusion technique allows controllable impregnation of cracks in the cement paste. A distinct contrast between gallium and the surrounding material...

  10. Bulk Group-III Nitride Crystal Growth in Supercritical Ammonia-Sodium Solutions

    Science.gov (United States)

    Griffiths, Steven Herbert

    Gallium nitride (GaN) and its alloys with indium nitride (InGaN) and aluminum nitride (AlGaN), collectively referred to as Group-III Nitride semiconductors, have enabled white solid-state lighting (SSL) sources and power electronic devices. While these technologies have already made a lasting, positive impact on society, improvements in design and efficiency are anticipated by shifting from heteroepitaxial growth on foreign substrates (such as sapphire, Si, SiC, etc.) to homoepitaxial growth on native, bulk GaN substrates. Bulk GaN has not supplanted foreign substrate materials due to the extreme conditions required to achieve a stoichiometric GaN melt (temperatures and pressures in excess of 2200°C and 6 GPa, respectively). The only method used to produce bulk GaN on an industrial scale is hydride vapor phase epitaxy (HVPE), but the high cost of gaseous precursors and relatively poor crystal quality have limited the adoption of this technology. A solution growth technique known as the ammonothermal method has attracted interest from academia and industry alike for its ability to produce bulk GaN boules of exceedingly high crystal quality. The ammonothermal method employs supercritical ammonia (NH3) solutions to dissolve, transport, and crystallize GaN. However, ammonothermal growth pressures are still relatively high (˜200 MPa), which has thus far prevented the acquisition of fundamental crystal growth knowledge needed to efficiently (i.e. through data-driven approaches) advance the field. This dissertation focused on addressing the gaps in the literature through two studies employing in situ fluid temperature analysis. The first study focused on identifying the solubility of GaN in supercritical NH3-Na solutions. The design and utilization of in situ and ex situ monitoring equipment enabled the first reports of the two-phase nature of supercritical NH3-Na solutions, and of Ga-alloying of Ni-containing autoclave components. The effects of these error sources on

  11. Anomalous piezoelectricity in two-dimensional graphene nitride nanosheets.

    Science.gov (United States)

    Zelisko, Matthew; Hanlumyuang, Yuranan; Yang, Shubin; Liu, Yuanming; Lei, Chihou; Li, Jiangyu; Ajayan, Pulickel M; Sharma, Pradeep

    2014-06-27

    Piezoelectricity is a unique property of materials that permits the conversion of mechanical stimuli into electrical and vice versa. On the basis of crystal symmetry considerations, pristine carbon nitride (C3N4) in its various forms is non-piezoelectric. Here we find clear evidence via piezoresponse force microscopy and quantum mechanical calculations that both atomically thin and layered graphitic carbon nitride, or graphene nitride, nanosheets exhibit anomalous piezoelectricity. Insights from ab inito calculations indicate that the emergence of piezoelectricity in this material is due to the fact that a stable phase of graphene nitride nanosheet is riddled with regularly spaced triangular holes. These non-centrosymmetric pores, and the universal presence of flexoelectricity in all dielectrics, lead to the manifestation of the apparent and experimentally verified piezoelectric response. Quantitatively, an e11 piezoelectric coefficient of 0.758 C m(-2) is predicted for C3N4 superlattice, significantly larger than that of the commonly compared α-quartz.

  12. Radiochemical neutron activation analysis based multi-elemental analysis of high purity gallium

    International Nuclear Information System (INIS)

    Tashimova, F.A.; Sadikov, I.I; Salimov, M.I.; Zinov'ev, V.G.

    2006-01-01

    Full text: Gallium is one of the widely used materials in semiconductor and optoelectronics industry. Gallium is used to produce infrared detectors, piezoelectric sensors, high- and low-temperature transistors for space and defense technology. One of the most important requirements for semiconductor materials of gallium compounds is an excessive high purity for layers and films. Information on impurities (type of an impurity, concentration, character of distribution) is important as for better understanding of the physical and chemical processes taking place in formed semiconductor structures and for the 'know-how' of devices on their basis. The object of this work is to develop radiochemical neutron activation technique for analysis of high purity gallium. Irradiation of 0.1 g of gallium sample in neutron flux of 5·10 13 cm -2 s -1 for 5 hours will result in induced activity of more than 10 8 Bq, due to 72 Ga radionuclide, half-life of which is 14.1 hours. Therefore to perform instrumental NAA of gallium long period (10 day) cooling is required, and high sensitive determination of elements producing short- and long-lived radionuclides (T 1/2 72 Ga. We have studied the behavior of gallium in extraction-chromatographic system 'TBP-HCl'. The experiments have shown that higher factor of distribution (D) and capacity on gallium can be achieved when 'TBP-4M HCl' system is used. However more than 10 trace elements have high D and thus they cannot be separated from 72 Ga. To resolve the problem and increase the number of separated trace elements we have used preliminary satisfaction of chromatographic column with tellurium, which has D higher than the most of elements in 'TBP-4M HCl' system and thus suppresses extraction of elements. Distribution profile of gallium along the column and elution curve of 25 trace elements have been measured. Chemical yields of separated elements measured by using radiotracers are more than 93%. On the basis of the carried out researches

  13. Gallium determination in biological samples

    International Nuclear Information System (INIS)

    Stulzaft, O.; Maziere, B.; Ly, S.

    1980-01-01

    A sensitive, simple and time-saving method has been developed for the neutron activation analysis of gallium at concentrations around 10 -4 ppm in biological tissues. After a 24-hour irradiation in a thermal neutron flux of 2.8x10 13 nxcm -2 xs -1 and a purification by ion-exchange chromatography to eliminate troublesome elements such as sodium, iron and copper, the 72 Ga activity is measured with enough accuracy for the method to be applicable in animal physiology and clinical toxicology. (author)

  14. Preparation of phosphorus targets using the compound phosphorus nitride

    International Nuclear Information System (INIS)

    Maier-Komor, P.

    1987-01-01

    Commercially available phosphorus nitride (P 3 N 5 ) shows a high oxygen content. Nevertheless, this material is attractive for use as phosphorus targets in experiments where red phosphorus would disappear due to its high vapor pressure and where a metal partner in the phosphide must be excluded due to its high atomic number. Methods are described to produce phosphorus nitride targets by vacuum evaporation condensation. (orig.)

  15. Triple templating of graphitic carbon nitride to enhance photocatalytic properties

    Directory of Open Access Journals (Sweden)

    Z. Yang

    2016-01-01

    Full Text Available Graphitic carbon nitride materials show some promising properties for applications such as photocatalytic water splitting. However, the conversion efficiency is still low due to factors such as a low surface area and limited light absorption. In this paper, we describe a “triple templating” approach to generating porous graphitic carbon nitride. The introduction of pores on several length-scales results in enhanced photocatalytic properties.

  16. Triple templating of graphitic carbon nitride to enhance photocatalytic properties

    OpenAIRE

    Z. Yang; A. E. Danks; J. Wang; Y. Zhang; Z. Schnepp

    2016-01-01

    Graphitic carbon nitride materials show some promising properties for applications such as photocatalytic water splitting. However, the conversion efficiency is still low due to factors such as a low surface area and limited light absorption. In this paper, we describe a “triple templating” approach to generating porous graphitic carbon nitride. The introduction of pores on several length-scales results in enhanced photocatalytic properties.

  17. Effects of erbium‑and chromium‑doped yttrium scandium gallium ...

    African Journals Online (AJOL)

    Effects of erbium‑and chromium‑doped yttrium scandium gallium garnet and diode lasers on the surfaces of restorative dental materials: A scanning electron microscope study. ... Four cylindrical samples (8 mm diameter, 2 mm height) were prepared for each restorative material. In addition, four freshly extracted, sound ...

  18. Maskless proton beam writing in gallium arsenide

    Energy Technology Data Exchange (ETDEWEB)

    Mistry, P. [Ion Beam Centre, University of Surrey, Guildford GU2 7XH (United Kingdom) and Nano-Electronics Centre, Advanced Technology Institute, University of Surrey, Guildford GU2 7XH (United Kingdom)]. E-mail: p.mistry@surrey.ac.uk; Gomez-Morilla, I. [Ion Beam Centre, University of Surrey, Guildford GU2 7XH (United Kingdom); Smith, R.C. [Nano-Electronics Centre, Advanced Technology Institute, University of Surrey, Guildford GU2 7XH (United Kingdom); Thomson, D. [Advanced Technology Institute, University of Surrey, Guildford GU2 7XH (United Kingdom); Grime, G.W. [Ion Beam Centre, University of Surrey, Guildford GU2 7XH (United Kingdom); Webb, R.P. [Ion Beam Centre, University of Surrey, Guildford GU2 7XH (United Kingdom); Gwilliam, R. [Ion Beam Centre, University of Surrey, Guildford GU2 7XH (United Kingdom); Jeynes, C. [Ion Beam Centre, University of Surrey, Guildford GU2 7XH (United Kingdom); Cansell, A. [Ion Beam Centre, University of Surrey, Guildford GU2 7XH (United Kingdom); Merchant, M. [Ion Beam Centre, University of Surrey, Guildford GU2 7XH (United Kingdom); Kirkby, K.J. [Ion Beam Centre, University of Surrey, Guildford GU2 7XH (United Kingdom)

    2007-07-15

    Proton beam writing (PBW) is a direct write technique that employs a focused MeV proton beam which is scanned in a pre-determined pattern over a target material which is subsequently electrochemically etched or chemically developed. By changing the energy of the protons the range of the protons can be changed. The ultimate depth of the structure is determined by the range of the protons in the material and this allows structures to be formed to different depths. PBW has been successfully employed on etchable glasses, polymers and semiconductor materials such as silicon (Si) and gallium arsenide (GaAs). This study reports on PBW in p-type GaAs and compares experimental results with computer simulations using the Atlas (copy right) semiconductor device package from SILVACO. It has already been proven that hole transport is required for the electrochemical etching of GaAs using Tiron (4,5-dihydroxy-m-benzenedisulfonic acid, di-sodium salt). PBW in GaAs results in carrier removal in the irradiated regions and consequently minimal hole transport (in these regions) during electrochemical etching. As a result the irradiated regions are significantly more etch resistant than the non-irradiated regions. This allows high aspect ratio structures to be formed.

  19. Maskless proton beam writing in gallium arsenide

    International Nuclear Information System (INIS)

    Mistry, P.; Gomez-Morilla, I.; Smith, R.C.; Thomson, D.; Grime, G.W.; Webb, R.P.; Gwilliam, R.; Jeynes, C.; Cansell, A.; Merchant, M.; Kirkby, K.J.

    2007-01-01

    Proton beam writing (PBW) is a direct write technique that employs a focused MeV proton beam which is scanned in a pre-determined pattern over a target material which is subsequently electrochemically etched or chemically developed. By changing the energy of the protons the range of the protons can be changed. The ultimate depth of the structure is determined by the range of the protons in the material and this allows structures to be formed to different depths. PBW has been successfully employed on etchable glasses, polymers and semiconductor materials such as silicon (Si) and gallium arsenide (GaAs). This study reports on PBW in p-type GaAs and compares experimental results with computer simulations using the Atlas (copy right) semiconductor device package from SILVACO. It has already been proven that hole transport is required for the electrochemical etching of GaAs using Tiron (4,5-dihydroxy-m-benzenedisulfonic acid, di-sodium salt). PBW in GaAs results in carrier removal in the irradiated regions and consequently minimal hole transport (in these regions) during electrochemical etching. As a result the irradiated regions are significantly more etch resistant than the non-irradiated regions. This allows high aspect ratio structures to be formed

  20. Optical Design of Dilute Nitride Quantum Wells Vertical Cavity Semiconductor Optical Amplifiers for Communication Systems

    Directory of Open Access Journals (Sweden)

    Faten A. Chaqmaqchee

    2016-04-01

    Full Text Available III-V semiconductors components such as Gallium Arsenic (GaAs, Indium Antimony (InSb, Aluminum Arsenic (AlAs and Indium Arsenic (InAs have high carrier mobilities and direct energy gaps. This is making them indispensable for today’s optoelectronic devices such as semiconductor lasers and optical amplifiers at 1.3 μm wavelength operation. In fact, these elements are led to the invention of the Gallium Indium Nitride Arsenic (GaInNAs, where the lattice is matched to GaAs for such applications. This article is aimed to design dilute nitride GaInNAs quantum wells (QWs enclosed between top and bottom of Aluminum (Gallium Arsenic Al(GaAs distributed bragg mirrors (DBRs using MATLAB® program. Vertical cavity semiconductor optical amplifiers (VCSOAs structures are based on Fabry Perot (FP method to design optical gain and bandwidth gain to be operated in reflection and transmission modes. The optical model gives access to the contact layer of epitaxial structure and the reflectivity for successive radiative modes, their lasing thresholds, emission wavelengths and optical field distributions in the laser cavity.

  1. Properties of gallium arsenide alloyed with Ge and Se by irradiation in nuclear reactor thermal column

    International Nuclear Information System (INIS)

    Kolin, N.G.; Osvenskij, V.B.; Tokarevskij, V.V.; Kharchenko, V.A.; Ievlev, S.M.

    1985-01-01

    Dependences of electrophysical properties as well as lattice unit spacing and density of nuclear-alloyed gallium arsenide on the fluence of reactor neutrons and heat treatment are investigated. Neutron radiation of gallium arsenide with different energy spectra is shown to differently affect material properties. Fast neutrons make the main contribution to defect formation. Concentration of compensating acceptor defects formed under GaAs radiation in a thermal column practically equals concentration of introduced donor impurities. Radiation defects of acceptor type are not annealed in the material completely even at 900-1000 deg C

  2. Evaluation of the male reproductive toxicity of gallium arsenide.

    Science.gov (United States)

    Bomhard, Ernst M; Cohen, Samuel M; Gelbke, Heinz-Peter; Williams, Gary M

    2012-10-01

    Gallium arsenide is an important semiconductor material marketed in the shape of wafers and thus is not hazardous to the end user. Exposure to GaAs particles may, however, occur during manufacture and processing. Potential hazards require evaluation. In 14-week inhalation studies with small GaAs particles, testicular effects have been reported in rats and mice. These effects occurred only in animals whose lungs showed marked inflammation and also had hematologic changes indicating anemia and hemolysis. The time- and concentration-dependent progressive nature of the lung and blood effects together with bioavailability data on gallium and arsenic lead us to conclude that the testicular/sperm effects are secondary to hypoxemia resulting from lung damage rather than due to a direct chemical effect of gallium or arsenide. Conditions leading to such primary effects are not expected to occur in humans at production and processing sites. This has to be taken into consideration for any classification decision for reproductive toxicity; especially a category 1 according to the EU CLP system is not warranted. Copyright © 2012 Elsevier Inc. All rights reserved.

  3. Metal surface nitriding by laser induced plasma

    Science.gov (United States)

    Thomann, A. L.; Boulmer-Leborgne, C.; Andreazza-Vignolle, C.; Andreazza, P.; Hermann, J.; Blondiaux, G.

    1996-10-01

    We study a nitriding technique of metals by means of laser induced plasma. The synthesized layers are composed of a nitrogen concentration gradient over several μm depth, and are expected to be useful for tribological applications with no adhesion problem. The nitriding method is tested on the synthesis of titanium nitride which is a well-known compound, obtained at present by many deposition and diffusion techniques. In the method of interest, a laser beam is focused on a titanium target in a nitrogen atmosphere, leading to the creation of a plasma over the metal surface. In order to understand the layer formation, it is necessary to characterize the plasma as well as the surface that it has been in contact with. Progressive nitrogen incorporation in the titanium lattice and TiN synthesis are studied by characterizing samples prepared with increasing laser shot number (100-4000). The role of the laser wavelength is also inspected by comparing layers obtained with two kinds of pulsed lasers: a transversal-excited-atmospheric-pressure-CO2 laser (λ=10.6 μm) and a XeCl excimer laser (λ=308 nm). Simulations of the target temperature rise under laser irradiation are performed, which evidence differences in the initial laser/material interaction (material heated thickness, heating time duration, etc.) depending on the laser features (wavelength and pulse time duration). Results from plasma characterization also point out that the plasma composition and propagation mode depend on the laser wavelength. Correlation of these results with those obtained from layer analyses shows at first the important role played by the plasma in the nitrogen incorporation. Its presence is necessary and allows N2 dissociation and a better energy coupling with the target. Second, it appears that the nitrogen diffusion governs the nitriding process. The study of the metal nitriding efficiency, depending on the laser used, allows us to explain the differences observed in the layer features

  4. Gallium-67 citrate scan in extrapulmonary tuberculosis

    International Nuclear Information System (INIS)

    Lin Wanyu

    1999-01-01

    Aim: Whole-body gallium scan was performed to evaluate the usefulness of gallium scan for detecting extrapulmonary tuberculosis (TB) lesions. Methods: Thirty-seven patients with extrapulmonary TB were included in this study. Four patients were found to have two lesions. Totally, 41 lesions were identified, including 19 TB arthritis, 8 spinal TB, 5 TB meningitis, 3 TB lymphadenopathy, 2 TB pericarditis, 1 TB peritonitis, 1 intestinal TB, 1 skin TB and 1 renal TB. Results: Of the 41 extrapulmonary TB lesions, gallium scan detected 32 lesions with a sensitivity of 78%. All the patients with TB meningitis showed negative gallium scan. When the five cases of TB meningitis were excluded, the detection sensitivity of gallium scan increased to 88.9% (32/36). Conclusion: Our data revealed that gallium scan is a convenient and useful method for evaluating extrapulmonary TB lesions other than TB-meningitis. We suggest that gallium scan be included in the clinical routine for patients with suspected extrapulmonary TB. (orig.) [de

  5. Laterally Vibrating Resonator Based Elasto-Optic Modulation in Aluminum Nitride

    Science.gov (United States)

    2016-08-15

    APL PHOTONICS 1, 036101 (2016) Laterally vibrating resonator based elasto-optic modulation in aluminum nitride Siddhartha Ghosha and Gianluca Piazza...enable overlap of the guided optical mode with the induced strain field. Both types of resonators are defined in an aluminum nitride (AlN) thin film...concept, we pattern devices in thin films of aluminum nitride (AlN). On account of its wurtzite crystal structure, AlN has been a popular material for

  6. Sample Size Induced Brittle-to-Ductile Transition of Single-Crystal Aluminum Nitride

    Science.gov (United States)

    2015-08-01

    Aluminum Nitride by GA Gazonas and JW McCauley Weapons and Materials Research Directorate, ARL JJ Guo, KM Reddy, A Hirata, T Fujita, and MW Chen...Sample Size Induced Brittle-to-Ductile Transition of Single-Crystal Aluminum Nitride 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...their microscopic structure. In this study, we report a size induced brittle-to-ductile transition in single-crystal aluminum nitride (AlN). When the

  7. Epitaxial Titanium Nitride on Sapphire: Effects of Substrate Temperature on Microstructure and Optical Properties (Preprint)

    Science.gov (United States)

    2017-12-20

    plasmonics are gold and silver ; however both metals have low melting points and high conduction electron losses that exclude them from high-temperature...have indicated transition metal nitrides as possible alternatives to gold and silver . Transition metal nitrides offer several advantages: They are...Titanium Nitride (TiN) is a mechanically-robust, high-temperature stable metallic material receiving considerable attention for resilient

  8. Adsorption of sugars on Al- and Ga-doped boron nitride surfaces: A computational study

    Energy Technology Data Exchange (ETDEWEB)

    Darwish, Ahmed A. [Center for Nanotechnology, Zewail City of Science and Technology, Giza 12588 (Egypt); Department of Nuclear and Radiation Engineering, Faculty of Engineering, Alexandria University, Alexandria (Egypt); Fadlallah, Mohamed M. [Center for Fundamental Physics, Zewail City of Science and Technology, Giza 12588 (Egypt); Department of Physics, Faculty of Science, Benha University, Benha (Egypt); Badawi, Ashraf [Center for Nanotechnology, Zewail City of Science and Technology, Giza 12588 (Egypt); Maarouf, Ahmed A., E-mail: ahmed.maarouf@egnc.gov.eg [Center for Fundamental Physics, Zewail City of Science and Technology, Giza 12588 (Egypt); Egypt Nanotechnology Center & Department of Physics, Faculty of Science, Cairo University, Giza 12613 (Egypt)

    2016-07-30

    Highlights: • Doping boron nitride sheets with aluminum or gallium atoms significantly enhances their molecular adsorption properties. • Adsorption of glucose or glucosamine on Al- and Ga-doped boron nitride sheets changes the band gap. • Doping concentration changes the bad gap, but has a minor effect on the adsorption energy. - Abstract: Molecular adsorption on surfaces is a key element for many applications, including sensing and catalysis. Non-invasive sugar sensing has been an active area of research due to its importance to diabetes care. The adsorption of sugars on a template surface study is at the heart of matter. Here, we study doped hexagonal boron nitride sheets (h-BNNs) as adsorbing and sensing template for glucose and glucosamine. Using first principles calculations, we find that the adsorption of glucose and glucosamine on h-BNNs is significantly enhanced by the substitutional doping of the sheet with Al and Ga. Including long range van der Waals corrections gives adsorption energies of about 2 eV. In addition to the charge transfer occurring between glucose and the Al/Ga-doped BN sheets, the adsorption alters the size of the band gap, allowing for optical detection of adsorption. We also find that Al-doped boron nitride sheet is better than Ga-doped boron nitride sheet to enhance the adsorption energy of glucose and glucosamine. The results of our work can be potentially utilized when designing support templates for glucose and glucosamine.

  9. Plasma nitriding of a precipitation hardening stainless steel to improve erosion and corrosion resistance

    International Nuclear Information System (INIS)

    Cabo, Amado; Bruhl, Sonia P.; Vaca, Laura S.; Charadia, Raul Charadia

    2010-01-01

    Precipitation hardening stainless steels are used as structural materials in the aircraft and the chemical industry because of their good combination of mechanical and corrosion properties. The aim of this work is to analyze the structural changes produced by plasma nitriding in the near surface of Thyroplast PH X Supra®, a PH stainless steel from ThyssenKrupp, and to study the effect of nitriding parameters in wear and corrosion resistance. Samples were first aged and then nitriding was carried out in an industrial facility at two temperatures, with two different nitrogen partial pressures in the gas mixture. After nitriding, samples were cut, polished, mounted in resin and etched with Vilella reagent to reveal the nitrided case. Nitrided structure was also analyzed with XRD. Erosion/Corrosion was tested against sea water and sand flux, and corrosion in a salt spray fog (ASTM B117). All nitrided samples presented high hardness. Samples nitrided at 390 deg C with different nitrogen partial pressure showed similar erosion resistance against water and sand flux. The erosion resistance of the nitrided samples at 500 deg C was the highest and XRD revealed nitrides. Corrosion resistance, on the contrary, was diminished; the samples suffered of general corrosion during the salt spray fog test. (author)

  10. Synthesis of graphitic carbon nitride by reaction of melamine and uric acid

    Energy Technology Data Exchange (ETDEWEB)

    Dante, Roberto C., E-mail: rcdante@yahoo.com [Laboratorio de Tecnologias del Medio Ambiente, Departamento de Ingenieria Agricola y Forestal, Universidad de Valladolid, Avenida de Madrid 44, 34004 Palencia (Spain); Martin-Ramos, Pablo, E-mail: pablomartinramos@gmail.com [Laboratorio de Tecnologias del Medio Ambiente, Departamento de Ingenieria Agricola y Forestal, Universidad de Valladolid, Avenida de Madrid 44, 34004 Palencia (Spain); Correa-Guimaraes, Adriana, E-mail: acg@iaf.uva.es [Laboratorio de Tecnologias del Medio Ambiente, Departamento de Ingenieria Agricola y Forestal, Universidad de Valladolid, Avenida de Madrid 44, 34004 Palencia (Spain); Martin-Gil, Jesus, E-mail: jesusmartingil@gmail.com [Laboratorio de Tecnologias del Medio Ambiente, Departamento de Ingenieria Agricola y Forestal, Universidad de Valladolid, Avenida de Madrid 44, 34004 Palencia (Spain)

    2011-11-01

    Highlights: {yields} Graphitic carbon nitrides by CVD of melamine and uric acid on alumina. {yields} The building blocks of carbon nitrides are heptazine nuclei. {yields} Composite particles with alumina core and carbon nitride coating. - Abstract: Graphitic carbon nitrides were synthesized starting from melamine and uric acid. Uric acid was chosen because it thermally decomposes, and reacts with melamine by condensation at temperatures in the range of 400-600 deg. C. The reagents were mixed with alumina and subsequently the samples were treated in an oven under nitrogen flux. Alumina favored the deposition of the graphitic carbon nitrides layers on the exposed surface. This method can be assimilated to an in situ chemical vapor deposition (CVD). Infrared (IR) spectra, as well as X-ray diffraction (XRD) patterns, are in accordance with the formation of a graphitic carbon nitride with a structure based on heptazine blocks. These carbon nitrides exhibit poor crystallinity and a nanometric texture, as shown by transmission electron microscopy (TEM) analysis. The thermal degradation of the graphitic carbon nitride occurs through cyano group formation, and involves the bridging tertiary nitrogen and the bonded carbon, which belongs to the heptazine ring, causing the ring opening and the consequent network destruction as inferred by connecting the IR and X-ray photoelectron spectroscopy (XPS) results. This seems to be an easy and promising route to synthesize graphitic carbon nitrides. Our final material is a composite made of an alumina core covered by carbon nitride layers.

  11. The Advanced Aluminum Nitride Synthesis Methods and Its Applications: Patent Review.

    Science.gov (United States)

    Shishkin, Roman A; Elagin, Andrey A; Mayorova, Ekaterina S; Beketov, Askold R

    2016-01-01

    High purity nanosized aluminum nitride synthesis is a current issue for both industry and science. However, there is no up-to-date review considering the major issues and the technical solutions for different methods. This review aims to investigate the advanced methods of aluminum nitride synthesis and its development tendencies. Also the aluminum nitride application patents and prospects for development of the branch have been considered. The patent search on "aluminum nitride synthesis" has been carried out. The research activity has been analyzed. Special attention has been paid to the patenting geography and the leading researchers in aluminum nitride synthesis. Aluminum nitride synthesis methods have been divided into 6 main groups, the most studied approaches are carbothermal reduction (88 patents) and direct nitridation (107 patents). The current issues for each group have been analyzed; the main trends are purification of the final product and nanopowder synthesis. The leading researchers in aluminum nitride synthesis have represented 5 countries, namely: Japan, China, Russia, South Korea and USA. The main aluminum nitride application spheres are electronics (59,1 percent of applications) and new materials manufacturing (30,9 percent). The review deals with the state of the art data in nanosized aluminum nitride synthesis, the major issues and the technical solutions for different synthesis methods. It gives a full understanding of the development tendencies and of the current leaders in the sphere.

  12. Preparation of boron nitride fiber by organic precursor method

    Directory of Open Access Journals (Sweden)

    Yingying Zhou

    Full Text Available In this paper, boron nitride polymer precursor was made by boric acid, melamine, twelve sodium alkyl sulfate as raw materials and pure water as medium which is heated to 70 °C. Boron nitride precursor polymer was soluble in formic acid solution. The boron nitride precursor can be electrostatically spun at the voltage in 23 kV and the distance between the positive and negative poles is 15 cm. The formed fiber is very uniform. The properties of the precursors were analyzed through electron microscope, infrared spectrum, X-ray and ultraviolet spectrum. The aim of the job is to got the precursor of BN and spun it. Keywords: Melamine, Boric acid, Boron nitride precursor, Electrostatic spinning

  13. Electrooptic Waveguide Directional Coupler Modulator in Aluminum Gallium Arsenide-Gallium Arsenide.

    Science.gov (United States)

    Khan, Mujibun Nisa

    A novel optical waveguide intensity modulator in aluminum gallium arsenide and gallium arsenide material system is modeled, designed, and experimentally demonstrated at 0.83 μm wavelength. The modulator utilizes the linear electrooptic effect in a coupled waveguide structure to achieve high extinction ratio at low drive voltage. The device structure consists of a differentially -etched ridge directional coupler, where the ridge height in the gap is smaller that that of the outer sides. The effective index and semivectorial finite difference modeling techniques are developed to analyze the single ridge guides and directional coupler structures. The mode structure results from the two models are compared and the limitations of the effective index method are determined. The differential -etch design is employed to reduce the length as well as the drive voltage of the modulator. A modulation voltage of 2 volts for a 3.5-mm-long device is achieved, which is the lowest reported in literature. These results are compared with those obtained from the simplified analytical expressions for conventional couplers, and higher performance expected from the differential-etch design is verified. The modulator extinction ratio is measured to be 13 dB at 2 volts. The measured optical propagation loss of approximately 3.4 dB/cm for the modulator is speculated to be primarily due to the surface morphology of the epitaxially-grown material, and the light scattering from rough ridge walls produced during the anisotropic dry etching process. The high microwave loss of 15 dB/cm calculated for the modulator electrode design suggests a trade-off between the modulation voltage and the bandwidth, which is expected to be limited to 500 MHz. The measurement of the modulator frequency response up to 100 KHz is presented, because of the test limitations at higher frequencies due to the weak modulated intensity signals.

  14. Fluorescent lighting with aluminum nitride phosphors

    Science.gov (United States)

    Cherepy, Nerine J.; Payne, Stephen A.; Seeley, Zachary M.; Srivastava, Alok M.

    2016-05-10

    A fluorescent lamp includes a glass envelope; at least two electrodes connected to the glass envelope; mercury vapor and an inert gas within the glass envelope; and a phosphor within the glass envelope, wherein the phosphor blend includes aluminum nitride. The phosphor may be a wurtzite (hexagonal) crystalline structure Al.sub.(1-x)M.sub.xN phosphor, where M may be drawn from beryllium, magnesium, calcium, strontium, barium, zinc, scandium, yttrium, lanthanum, cerium, praseodymium, europium, gadolinium, terbium, ytterbium, bismuth, manganese, silicon, germanium, tin, boron, or gallium is synthesized to include dopants to control its luminescence under ultraviolet excitation. The disclosed Al.sub.(1-x)M.sub.xN:Mn phosphor provides bright orange-red emission, comparable in efficiency and spectrum to that of the standard orange-red phosphor used in fluorescent lighting, Y.sub.2O.sub.3:Eu. Furthermore, it offers excellent lumen maintenance in a fluorescent lamp, and does not utilize "critical rare earths," minimizing sensitivity to fluctuating market prices for the rare earth elements.

  15. Thermodynamics, kinetics and process control of nitriding

    DEFF Research Database (Denmark)

    Mittemeijer, Eric J.; Somers, Marcel A. J.

    1997-01-01

    for process control of gaseous nitriding by monitoring the partial pressure of oxygen in the furnace using a solid state electrolyte is provided. At the time the work was carried out the authors were in the Laboratory of Materials Science, Delft University of Technology, Rotterdamseweg 137, 2628 AL Delft......As a prerequisite for the predictability of properties obtained by a nitriding treatment of iron based workpieces, the relation between the process parameters and the composition and structure of the surface layer produced must be known. At present, even the description of thermodynamic equilibrium...... of the International Federation for Heat Treatment and Surface Engineering held in Brighton, UK on 1-5 September 1996. (C) 1997 The Institute of Materials....

  16. Gallium-67 activity in bronchoalveolar lavage fluid in sarcoidosis

    International Nuclear Information System (INIS)

    Trauth, H.A.; Heimes, K.; Schubotz, R.; von Wichert, P.

    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 of 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

  17. Scanning proximal microscopy study of the thin layers of silicon carbide-aluminum nitride solid solution manufactured by fast sublimation epitaxy

    Directory of Open Access Journals (Sweden)

    Tománek P.

    2013-05-01

    Full Text Available The objective of the study is a growth of SiC/(SiC1−x(AlNx structures by fast sublimation epitaxy of the polycrystalline source of (SiC1−x(AlNx and their characterisation by proximal scanning electron microscopy and atomic force microscopy. For that purpose optimal conditions of sublimation process have been defined. Manufactured structures could be used as substrates for wide-band-gap semiconductor devices on the basis of nitrides, including gallium nitride, aluminum nitride and their alloys, as well as for the production of transistors with high mobility of electrons and also for creation of blue and ultraviolet light emitters (light-emitted diodes and laser diodes. The result of analysis shows that increasing of the growth temperature up to 2300 K allows carry out sublimation epitaxy of thin layers of aluminum nitride and its solid solution.

  18. Properties of gallium lanthanum sulphide glass

    OpenAIRE

    Bastock, P.; Craig, C.; Khan, K.; Weatherby, E.; Yao, J.; Hewak, D.W.

    2015-01-01

    A series of gallium lanthanum sulphide (GLS) glasses has been studied in order to ascertain properties across the entire glass forming region. This is the first comprehensive study of GLS glass over a wide compositional range.

  19. Glutathione role in gallium induced toxicity

    African Journals Online (AJOL)

    Asim

    2012-01-26

    GSH) present in tissues. It is very important and interesting to study the reaction of gallium nitrate and glutathione as biomarker of glutathione role in detoxification and conjugation in whole blood components (plasma and ...

  20. Water thermostatic bath to compare gallium cells

    OpenAIRE

    Santiago, José Felipe Neves; Petkovic, Slavolhub Garcia; Moreira, Valquimar Marvila

    2001-01-01

    In general, gallium cells can be realised in any water thermostatic bath, however, some manufactures have developed air furnaces or heat-cooling ovens (with peltier cells and heating resistors) to avoid mechanic vibrations, electromagnetic interference, and to allow for easier and dedicated operation mode. Generally, all of these devices are dedicated and they are used with only one cell. As we want to compare two different gallium cells, we have developed a water thermostatic bath, whi...

  1. Compressive creep of silicon nitride

    International Nuclear Information System (INIS)

    Silva, C.R.M. da; Melo, F.C.L. de; Cairo, C.A.; Piorino Neto, F.

    1990-01-01

    Silicon nitride samples were formed by pressureless sintering process, using neodymium oxide and a mixture of neodymium oxide and yttrio oxide as sintering aids. The short term compressive creep behaviour was evaluated over a stress range of 50-300 MPa and temperature range 1200 - 1350 0 C. Post-sintering heat treatments in nitrogen with a stepwise decremental variation of temperature were performed in some samples and microstructural analysis by X-ray diffraction and transmission electron microscopy showed that the secondary crystalline phase which form from the remnant glass are dependent upon composition and percentage of aditives. Stress exponent values near to unity were obtained for materials with low glass content suggesting grain boundary diffusion accommodation processes. Cavitation will thereby become prevalent with increase in stress, temperature and decrease in the degree of crystallization of the grain boundary phase. (author) [pt

  2. The global anthropogenic gallium system: determinants of demand, supply and efficiency improvements.

    Science.gov (United States)

    Løvik, Amund N; Restrepo, Eliette; Müller, Daniel B

    2015-05-05

    Gallium has been labeled as a critical metal due to rapidly growing consumption, importance for low-carbon technologies such as solid state lighting and photovoltaics, and being produced only as a byproduct of other metals (mainly aluminum). The global system of primary production, manufacturing, use and recycling has not yet been described or quantified in the literature. This prevents predictions of future demand, supply and possibilities for efficiency improvements on a system level. We present a description of the global anthropogenic gallium system and quantify the system using a combination of statistical data and technical parameters. We estimated that gallium was produced from 8 to 21% of alumina plants in 2011. The most important applications of gallium are NdFeB permanent magnets, integrated circuits and GaAs/GaP-based light-emitting diodes, demanding 22-37%, 16-27%, and 11-21% of primary metal production, respectively. GaN-based light-emitting diodes and photovoltaics are less important, both with 2-6%. We estimated that 120-170 tons, corresponding to 40-60% of primary production, ended up in production wastes that were either disposed of or stored. While demand for gallium is expected to rise in the future, our results indicated that it is possible to increase primary production substantially with conventional technology, as well as improve the system-wide material efficiency.

  3. Clinical applications of Gallium-68

    International Nuclear Information System (INIS)

    Banerjee, Sangeeta Ray; Pomper, Martin G.

    2013-01-01

    Gallium-68 is a positron-emitting radioisotope that is produced from a 68 Ge/ 68 Ga generator. As such it is conveniently used, decoupling radiopharmacies from the need for a cyclotron on site. Gallium-68-labeled peptides have been recognized as a new class of radiopharmaceuticals showing fast target localization and blood clearance. 68 Ga-DOTATOC, 8 Ga-DOTATATE, 68 Ga-DOTANOC, are the most prominent radiopharmaceuticals currently in use for imaging and differentiating lesions of various somatostatin receptor subtypes, overexpressed in many neuroendocrine tumors. There has been a tremendous increase in the number of clinical studies with 68 Ga over the past few years around the world, including within the United States. An estimated ∼10,000 scans are being performed yearly in Europe at about 100 centers utilizing 68 Ga-labeled somatostatin analogs within clinical trials. Two academic sites within the US have also begun to undertake human studies. This review will focus on the clinical experience of selected, well-established and recently applied 68 Ga-labeled imaging agents used in nuclear medicine. - Highlights: ► A summary of the emerging clinical uses of 68 Ga-based radiopharmaceuticals is provided. ► 68 Ga-PET may prove as or more clinically robust than the corresponding 18 F-labeled agents. ► 68 Ga-radiopeptides were studied for targeting of somatostatin receptors subtypes. ► 68 Ga-DOTATOC, 68 Ga-DOTATATE, 68 Ga-DOTANOC, are currently in clinical trials

  4. Effect of magnetic field on the mechanical properties of magnetostrictive iron-gallium nanowires

    International Nuclear Information System (INIS)

    Downey, Patrick R.; Flatau, Alison B.; McGary, Patrick D.; Stadler, Bethanie J. H.

    2008-01-01

    This study experimentally investigates the elastic properties of individual iron-gallium nanowires with and without an applied magnetic bias field. The experiments were conducted with a custom manipulator stage designed for use within a scanning electron microscope, where nanowires were mechanically tested both statically and dynamically. Experiments were also performed in the presence of a 20 Oe dc magnetic field in order to identify any variation in wire properties. The results suggest that iron-gallium nanowires possess an elastic modulus very similar to the macroscale value, tensile strengths of more than double the bulk material, and minor magnetic field induced stiffening at low stresses

  5. Spectral and luminescence properties of Cr(3+) ad Nd(3+) ions in gallium garnet crystals

    Science.gov (United States)

    Denisov, A. L.; Ostroumov, V. G.; Saidov, Z. S.; Smirnov, V. A.; Shcherbakov, I. A.

    1986-01-01

    The effective peak stimulated-emission cross section of chromium-doped gadolinium-scandium-gallium garnets (GSGG) has been determined to be 8.5 x 10 to the -21st sq cm at room temperature. The values of the energy-gap Delta E(2E-4T2) chromim fluorescence lifetime and the chromium to neodymium energy-transfer parameter C(DA) (Cr-Nd) are determined for several gallium garnets. Temperature-dependent absorption and luminescence spectra of neodymium-doped GGG and GSGG are reported and discussed in the context of their use as laser materials.

  6. Results of the Gallium-Clad Phase 3 and Phase 4 tasks (canceled prior to completion)

    International Nuclear Information System (INIS)

    Morris, R.N.

    1998-08-01

    This report summarizes the results of the Gallium-Clad interactions Phase 3 and 4 tasks. Both tasks were to involve examining the out-of-pile stability of residual gallium in short fuel rods with an imposed thermal gradient. The thermal environment was to be created by an electrical heater in the center of the fuel rod and coolant flow on the rod outer cladding. Both tasks were canceled due to difficulties with fuel pellet fabrication, delays in the preparation of the test apparatus, and changes in the Fissile Materials Disposition program budget

  7. Results of the Gallium-Clad Phase 3 and Phase 4 tasks (canceled prior to completion)

    Energy Technology Data Exchange (ETDEWEB)

    Morris, R.N.

    1998-08-01

    This report summarizes the results of the Gallium-Clad interactions Phase 3 and 4 tasks. Both tasks were to involve examining the out-of-pile stability of residual gallium in short fuel rods with an imposed thermal gradient. The thermal environment was to be created by an electrical heater in the center of the fuel rod and coolant flow on the rod outer cladding. Both tasks were canceled due to difficulties with fuel pellet fabrication, delays in the preparation of the test apparatus, and changes in the Fissile Materials Disposition program budget.

  8. Sodium enhances indium-gallium interdiffusion in copper indium gallium diselenide photovoltaic absorbers.

    Science.gov (United States)

    Colombara, Diego; Werner, Florian; Schwarz, Torsten; Cañero Infante, Ingrid; Fleming, Yves; Valle, Nathalie; Spindler, Conrad; Vacchieri, Erica; Rey, Germain; Guennou, Mael; Bouttemy, Muriel; Manjón, Alba Garzón; Peral Alonso, Inmaculada; Melchiorre, Michele; El Adib, Brahime; Gault, Baptiste; Raabe, Dierk; Dale, Phillip J; Siebentritt, Susanne

    2018-02-26

    Copper indium gallium diselenide-based technology provides the most efficient solar energy conversion among all thin-film photovoltaic devices. This is possible due to engineered gallium depth gradients and alkali extrinsic doping. Sodium is well known to impede interdiffusion of indium and gallium in polycrystalline Cu(In,Ga)Se 2 films, thus influencing the gallium depth distribution. Here, however, sodium is shown to have the opposite effect in monocrystalline gallium-free CuInSe 2 grown on GaAs substrates. Gallium in-diffusion from the substrates is enhanced when sodium is incorporated into the film, leading to Cu(In,Ga)Se 2 and Cu(In,Ga) 3 Se 5 phase formation. These results show that sodium does not decrease per se indium and gallium interdiffusion. Instead, it is suggested that sodium promotes indium and gallium intragrain diffusion, while it hinders intergrain diffusion by segregating at grain boundaries. The deeper understanding of dopant-mediated atomic diffusion mechanisms should lead to more effective chemical and electrical passivation strategies, and more efficient solar cells.

  9. Magnetoelectric effect in layered structures of amorphous ferromagnetic alloy and gallium arsenide

    Energy Technology Data Exchange (ETDEWEB)

    Bichurin, M.I., E-mail: mirza.bichurin@novsu.ru; Petrov, V.M.; Leontiev, V.S.; Ivanov, S.N.; Sokolov, O.V.

    2017-02-15

    A paper devotes to theoretical and experimental studying the magnetoelectric interaction in layered structures of amorphous ferromagnetic alloy and single- crystal gallium arsenide. The authors investigated the magnetoelectric effect in the (100) plane of gallium arsenide in the electromechanical resonance range of 200–240 kHz and obtained maximal ME voltage coefficient of 120 V/A at bias field equaled 3.6 kA/m for the direction parallel to the [011] axis. Also the magnetoelectric effect in the (110) and (111) planes is discussed. The results can be used for design of new electronic devices based on the magnetostrictive-semiconductor materials. - Highlights: • Theoretical modeling of ME interaction was conducted. • Experimental dependencies in the resonance range were done. • Maximal ME effect of gallium arsenide was observed.

  10. Fatigue modelling for gas nitriding

    Directory of Open Access Journals (Sweden)

    H. Weil

    2016-10-01

    Full Text Available The present study aims to develop an algorithm able to predict the fatigue lifetime of nitrided steels. Linear multi-axial fatigue criteria are used to take into account the gradients of mechanical properties provided by the nitriding process. Simulations on rotating bending fatigue specimens are made in order to test the nitrided surfaces. The fatigue model is applied to the cyclic loading of a gear from a simulation using the finite element software Ansys. Results show the positive contributions of nitriding on the fatigue strength

  11. Material and device studies for the development of ultra-violet light emitting diodes (UV-LEDS) along polar, non-polar and semi-polar directions

    Science.gov (United States)

    Chandrasekaran, Ramya

    Over the past few years, significant effort was dedicated to the development of ultraviolet light emitting diodes (UV-LEDs) for a variety of applications. Such applications include chemical and biological detection, water purification and solid-state lighting. III-Nitride LEDs based on multiple quantum wells (MQWs) grown along the conventional [0001] (polar) direction suffer from the quantum confined Stark effect (QCSE), due to the existence of strong electric fields that arise from spontaneous and piezoelectric polarization. Thus, there is strong motivation to develop MQW-based III-nitride LED structures grown along non-polar and semi-polar directions. The goal of this dissertation is to develop UV-LEDs along the [0001] polar and [11 2¯ 0] non-polar directions by the method of Molecular Beam Epitaxy (MBE). The polar and non-polar LEDs were grown on the C-plane and R-plane sapphire substrates respectively. This work is a combination of materials science studies related to the nucleation, growth and n- and p-type doping of III-nitride films on these two substrates, as well as device studies related to fabrication and characterization of UV-LEDs. It was observed that the crystallographic orientation of the III-nitride films grown on R-plane sapphire depends strongly on the kinetic conditions of growth of the Aluminum Nitride (AIN) buffer. Specifically, growth of the AIN buffer under group III-rich conditions leads to nitride films having the (11 2¯ 0) non polar planes parallel to the sapphire surface, while growth of the buffer under nitrogen rich conditions leads to nitride films with the (11 2¯ 6) semi-polar planes parallel to the sapphire surface. The electron concentration and mobility for the films grown along the polar, non-polar and semi-polar directions were investigated. P-type doping of Gallium Nitride (GaN) films grown on the nonpolar (11 2¯ 0) plane do not suffer from polarity inversion and thus the material was doped p-type with a hole concentration

  12. Evaluation of the carcinogenicity of gallium arsenide.

    Science.gov (United States)

    Bomhard, Ernst M; Gelbke, Heinz-Peter; Schenk, Hermann; Williams, Gary M; Cohen, Samuel M

    2013-05-01

    Gallium arsenide (GaAs) is an important semiconductor material. In 2-year inhalation studies, GaAs increased the incidence of lung tumors in female rats, but not in male rats or male and female mice. Alveolar proteinosis followed by chronic active inflammation was the predominant non-neoplastic pulmonary findings. IARC classified GaAs as carcinogenic to humans (group 1) based on the assumption that As and Ga ions are bioavailable. The European Chemical Agency Risk Assessment Committee concluded that GaAs should be classified into Carcinogenicity Category 1B (presumed to have carcinogenic potential for humans; ECHA). We evaluate whether these classifications are justified. Physico-chemical properties of GaAs particles and the degree of mechanical treatment are critical in this evaluation. The available data on mode of action (MOA), genotoxicity and bioavailability do not support the contribution of As or Ga ions to the lung tumors in female rats. Most toxicological studies utilized small particles produced by strong mechanical treatment, destroying the crystalline structure. The resulting amorphous GaAs is not relevant to crystalline GaAs at production and processing sites. The likely tumorigenic MOA is lung toxicity related to particulate-induced inflammation and increased proliferation. It is concluded that there is no evidence for a primary carcinogenic effect of GaAs.

  13. Testing of gallium arsenide solar cells on the CRRES vehicle

    Science.gov (United States)

    Trumble, T. M.

    1985-01-01

    A flight experiment was designed to determine the optimum design for gallium arsenide (GaAs) solar cell panels in a radiation environment. Elements of the experiment design include, different coverglass material and thicknesses, welded and soldered interconnects, different solar cell efficiencies, different solar cell types, and measurement of annealing properties. This experiment is scheduled to fly on the Combined Release and Radiation Effects Satellite (CRRES). This satellite will simultaneously measure the radiation environment and provide engineering data on solar cell degradation that can be directly related to radiation damage.

  14. Testing of gallium arsenide solar cells on the CRRES vehicle

    International Nuclear Information System (INIS)

    Trumble, T.M.

    1985-01-01

    A flight experiment was designed to determine the optimum design for gallium arsenide (GaAs) solar cell panels in a radiation environment. Elements of the experiment design include, different coverglass material and thicknesses, welded and soldered interconnects, different solar cell efficiencies, different solar cell types, and measurement of annealing properties. This experiment is scheduled to fly on the Combined Release and Radiation Effects Satellite (CRRES). This satellite will simultaneously measure the radiation environment and provide engineering data on solar cell degradation that can be directly related to radiation damage

  15. Nanotribological response of a plasma nitrided bio-steel.

    Science.gov (United States)

    Samanta, Aniruddha; Chakraborty, Himel; Bhattacharya, Manjima; Ghosh, Jiten; Sreemany, Monjoy; Bysakh, Sandip; Rane, Ramkrishna; Joseph, Alphonsa; Jhala, Ghanshyam; Mukherjee, Subroto; Das, Mitun; Mukhopadhyay, Anoop K

    2017-01-01

    AISI 316L is a well known biocompatible, austenitic stainless steel (SS). It is thus a bio-steel. Considering its importance as a bio-prosthesis material here we report the plasma nitriding of AISI 316L (SS) followed by its microstructural and nanotribological characterization. Plasma nitriding of the SS samples was carried out in a plasma reactor with a hot wall vacuum chamber. For ease of comparison these plasma nitrided samples were termed as SSPN. The experimental results confirmed the formations of an embedded nitrided metal layer zone (ENMLZ) and an interface zone (IZ) between the ENMLZ and the unnitrided bulk metallic layer zone (BMLZ) in the SSPN sample. These ENMLZ and IZ in the SSPN sample were richer in iron nitride (FeN) chromium nitride (CrN) along with the austenite phase. The results from nanoindentation, microscratch, nanoscratch and sliding wear studies confirmed that the static contact deformation resistance, the microwear, nanowear and sliding wear resistance of the SSPN samples were much better than those of the SS samples. These results were explained in terms of structure-property correlations. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Plasmonic Titanium Nitride Nanostructures via Nitridation of Nanopatterned Titanium Dioxide

    DEFF Research Database (Denmark)

    Guler, Urcan; Zemlyanov, Dmitry; Kim, Jongbum

    2017-01-01

    Plasmonic titanium nitride nanostructures are obtained via nitridation of titanium dioxide. Nanoparticles acquired a cubic shape with sharper edges following the rock-salt crystalline structure of TiN. Lattice constant of the resulting TiN nanoparticles matched well with the tabulated data. Energy...

  17. Window structure for passivating solar cells based on gallium arsenide

    Science.gov (United States)

    Barnett, Allen M. (Inventor)

    1985-01-01

    Passivated gallium arsenide solar photovoltaic cells with high resistance to moisture and oxygen are provided by means of a gallium arsenide phosphide window graded through its thickness from arsenic rich to phosphorus rich.

  18. Generation and Characteristics of IV-VI transition Metal Nitride and Carbide Nanoparticles using a Reactive Mesoporous Carbon Nitride

    KAUST Repository

    Alhajri, Nawal Saad

    2016-02-22

    Interstitial nitrides and carbides of early transition metals in groups IV–VI exhibit platinum-like electronic structures, which make them promising candidates to replace noble metals in various catalytic reactions. Herein, we present the preparation and characterization of nano-sized transition metal nitries and carbides of groups IV–VI (Ti, V, Nb, Ta, Cr, Mo, and W) using mesoporous graphitic carbon nitride (mpg-C3N4), which not only provides confined spaces for restricting primary particle size but also acts as a chemical source of nitrogen and carbon. We studied the reactivity of the metals with the template under N2 flow at 1023 K while keeping the weight ratio of metal to template constant at unity. The produced nanoparticles were characterized by powder X-ray diffraction, CHN elemental analysis, nitrogen sorption, X-ray photoelectron spectroscopy, and transmission electron microscopy. The results show that Ti, V, Nb, Ta, and Cr form nitride phases with face centered cubic structure, whereas Mo and W forme carbides with hexagonal structures. The tendency to form nitride or carbide obeys the free formation energy of the transition metal nitrides and carbides. This method offers the potential to prepare the desired size, shape and phase of transition metal nitrides and carbides that are suitable for a specific reaction, which is the chief objective of materials chemistry.

  19. Pulsed laser heating of silicon-nitride capped GaAs: Optical properties at high temperature

    Science.gov (United States)

    Bhat, A.; Yao, H. D.; Compaan, A.; Horak, A.; Rys, A.

    1988-09-01

    The optical properties of silicon nitride and gallium arsenide were studied at temperatures up to and beyond the melting point of GaAs by means of laser heating. XeCl excimer and pulsed dye laser pulses, ˜10 ns in duration, were used to heat the semiconductor under nitride capping layers of varying thickness. The transient reflectivity response at 514.5 nm was used together with a multilayer interference analysis to obtain the optical constants of solid and molten GaAs and of solid Si3N4 near the 1513-K melting point of GaAs. In addition, we report the melt duration as a function of laser pulse energy for GaAs with and without capping layers.

  20. Electrochemical nitridation of metal surfaces

    Science.gov (United States)

    Wang, Heli; Turner, John A.

    2015-06-30

    Electrochemical nitridation of metals and the produced metals are disclosed. An exemplary method of electrochemical nitridation of metals comprises providing an electrochemical solution at low temperature. The method also comprises providing a three-electrode potentiostat system. The method also comprises stabilizing the three-electrode potentiostat system at open circuit potential. The method also comprises applying a cathodic potential to a metal.

  1. 67Gallium • the D,etection and Localization

    African Journals Online (AJOL)

    1971-12-11

    Dec 11, 1971 ... radioactivity into areas of increased osteogenic activity. Dudley et al: investigating deposition of "Gallium in ... dency for gallium to localize in areas of bone activity, whether osteoblastic or osteolytic, as well as .... Gallium citrate was obtained from the Nuclear Physics and Radioactivity Division at the National ...

  2. Composite boron nitride neutron detectors

    Science.gov (United States)

    Roth, M.; Mojaev, E.; Khakhan, O.; Fleider, A.; Dul`kin, E.; Schieber, M.

    2014-09-01

    Single phase polycrystalline hexagonal boron nitride (BN) or mixed with boron carbide (BxC) embedded in an insulating polymeric matrix acting as a binder and forming a composite material as well as pure submicron size polycrystalline BN has been tested as a thermal neutron converter in a multilayer thermal neutron detector design. Metal sheet electrodes were covered with 20-50 μm thick layers of composite materials and assembled in a multi-layer sandwich configuration. High voltage was applied to the metal electrodes to create an interspacing electric field. The spacing volume could be filled with air, nitrogen or argon. Thermal neutrons were captured in converter layers due to the presence of the 10B isotope. The resulting nuclear reaction produced α-particles and 7Li ions which ionized the gas in the spacing volume. Electron-ion pairs were collected by the field to create an electrical signal proportional to the intensity of the neutron source. The detection efficiency of the multilayer neutron detectors is found to increase with the number of active converter layers. Pixel structures of such neutron detectors necessary for imaging applications and incorporation of internal moderator materials for field measurements of fast neutron flux intensities are discussed as well.

  3. Gallium arsenide processing for gate array logic

    Science.gov (United States)

    Cole, Eric D.

    1989-01-01

    The development of a reliable and reproducible GaAs process was initiated for applications in gate array logic. Gallium Arsenide is an extremely important material for high speed electronic applications in both digital and analog circuits since its electron mobility is 3 to 5 times that of silicon, this allows for faster switching times for devices fabricated with it. Unfortunately GaAs is an extremely difficult material to process with respect to silicon and since it includes the arsenic component GaAs can be quite dangerous (toxic) especially during some heating steps. The first stage of the research was directed at developing a simple process to produce GaAs MESFETs. The MESFET (MEtal Semiconductor Field Effect Transistor) is the most useful, practical and simple active device which can be fabricated in GaAs. It utilizes an ohmic source and drain contact separated by a Schottky gate. The gate width is typically a few microns. Several process steps were required to produce a good working device including ion implantation, photolithography, thermal annealing, and metal deposition. A process was designed to reduce the total number of steps to a minimum so as to reduce possible errors. The first run produced no good devices. The problem occurred during an aluminum etch step while defining the gate contacts. It was found that the chemical etchant attacked the GaAs causing trenching and subsequent severing of the active gate region from the rest of the device. Thus all devices appeared as open circuits. This problem is being corrected and since it was the last step in the process correction should be successful. The second planned stage involves the circuit assembly of the discrete MESFETs into logic gates for test and analysis. Finally the third stage is to incorporate the designed process with the tested circuit in a layout that would produce the gate array as a GaAs integrated circuit.

  4. Handbook of refractory carbides and nitrides properties, characteristics, processing and applications

    CERN Document Server

    Pierson, Hugh O

    1996-01-01

    Refractory carbides and nitrides are useful materials with numerous industrial applications and a promising future, in addition to being materials of great interest to the scientific community. Although most of their applications are recent, the refractory carbides and nitrides have been known for over one hundred years. The industrial importance of the refractory carbides and nitrides is growing rapidly, not only in the traditional and well-established applications based on the strength and refractory nature of these materials such as cutting tools and abrasives, but also in new and promising fields such as electronics and optoelectronics.

  5. Development of a Multi-layer Anti-reflective Coating for Gallium Arsenide/Aluminum Gallium Arsenide Solar Cells

    Science.gov (United States)

    2015-07-01

    Aluminum Gallium Arsenide Solar Cells by Kimberley A Olver Approved for public release; distribution unlimited...Development of a Multi-layer Anti-reflective Coating for Gallium Arsenide / Aluminum Gallium Arsenide Solar Cells by Kimberley A Olver... Aluminum Gallium Arsenide (AlGaAs) Solar Cells 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Kimberley A Olver

  6. Magnesium doping of boron nitride nanotubes

    Science.gov (United States)

    Legg, Robert; Jordan, Kevin

    2015-06-16

    A method to fabricate boron nitride nanotubes incorporating magnesium diboride in their structure. In a first embodiment, magnesium wire is introduced into a reaction feed bundle during a BNNT fabrication process. In a second embodiment, magnesium in powder form is mixed into a nitrogen gas flow during the BNNT fabrication process. MgB.sub.2 yarn may be used for superconducting applications and, in that capacity, has considerably less susceptibility to stress and has considerably better thermal conductivity than these conventional materials when compared to both conventional low and high temperature superconducting materials.

  7. Chemical stability of carbon-based inorganic materials for in situ x-ray investigations of ammonothermal crystal growth of nitrides

    Science.gov (United States)

    Schimmel, Saskia; Künecke, Ulrike; Meisel, Magnus; Hertweck, Benjamin; Steigerwald, Thomas G.; Nebel, Christoph; Alt, Nicolas S. A.; Schlücker, Eberhard; Wellmann, Peter

    2016-12-01

    The chemical stability of diamond, silicon carbide, vitreous carbon, and boron carbide in supercritical ammonia containing different mineralizers was investigated. The materials were found to show good corrosion resistance in the presence of selective or all tested mineralizers. Diamond was found to be virtually inert in both ammonoacidic and ammonobasic reaction media. Silicon carbide showed good chemical stability in varying ammonothermal reaction media. The chemical stability of vitreous carbon was found to depend on its manufacturing temperature. Corrosion of boron carbide strongly depends on the mineralizer used as well as on applied mechanical stress. Based on their chemical stability and mechanical properties, the applicability of the materials in the respective ammonothermal reaction media as construction materials is evaluated. Additionally, the applicability of the materials as a window material for both high energy in situ x-ray imaging and low energy in situ x-ray diffraction is discussed.

  8. A Gallium-Based Magnetocaloric Liquid Metal Ferrofluid.

    Science.gov (United States)

    A de Castro, Isabela; Chrimes, Adam F; Zavabeti, Ali; Berean, Kyle J; Carey, Benjamin J; Zhuang, Jincheng; Du, Yi; Dou, Shi X; Suzuki, Kiyonori; Shanks, Robert A; Nixon-Luke, Reece; Bryant, Gary; Khoshmanesh, Khashayar; Kalantar-Zadeh, Kourosh; Daeneke, Torben

    2017-12-13

    We demonstrate a magnetocaloric ferrofluid based on a gadolinium saturated liquid metal matrix, using a gallium-based liquid metal alloy as the solvent and suspension medium. The material is liquid at room temperature, while exhibiting spontaneous magnetization and a large magnetocaloric effect. The magnetic properties were attributed to the formation of gadolinium nanoparticles suspended within the liquid gallium alloy, which acts as a reaction solvent during the nanoparticle synthesis. High nanoparticle weight fractions exceeding 2% could be suspended within the liquid metal matrix. The liquid metal ferrofluid shows promise for magnetocaloric cooling due to its high thermal conductivity and its liquid nature. Magnetic and thermoanalytic characterizations reveal that the developed material remains liquid within the temperature window required for domestic refrigeration purposes, which enables future fluidic magnetocaloric devices. Additionally, the observed formation of nanometer-sized metallic particles within the supersaturated liquid metal solution has general implications for chemical synthesis and provides a new synthetic pathway toward metallic nanoparticles based on highly reactive rare earth metals.

  9. Conductive Carbon Nitride for Excellent Energy Storage.

    Science.gov (United States)

    Xu, Jijian; Xu, Feng; Qian, Meng; Xu, Fangfang; Hong, Zhanglian; Huang, Fuqiang

    2017-08-01

    Conductive carbon nitride, as a hypothetical carbon material demonstrating high nitrogen doping, high electrical conductivity, and high surface area, has not been fabricated. A major challenge towards its fabrication is that high conductivity requires high temperature synthesis, but the high temperature eliminates nitrogen from carbon. Different from conventional methods, a facile preparation of conductive carbon nitride from novel thermal decomposition of nickel hydrogencyanamide in a confined space is reported. New developed nickel hydrogencyanamide is a unique precursor which provides self-grown fragments of ⋅NCN⋅ or NCCN and conductive carbon (C-sp 2 ) catalyst of Ni metal during the decomposition. The final product is a tubular structure of rich mesoporous and microporous few-layer carbon with extraordinarily high N doping level (≈15 at%) and high extent of sp 2 carbon (≈65%) favoring a high conductivity (>2 S cm -1 ); the ultrahigh contents of nongraphitic nitrogen, redox active pyridinic N (9 at%), and pyrrolic N (5 at%), are stabilized by forming NiN bonds. The conductive carbon nitride harvests a large capacitance of 372 F g -1 with >90% initial capacitance after 10 000 cycles as a supercapacitor electrode, far exceeding the activated carbon electrodes that have <250 F g -1 . © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Synthesis and Processing of Nanocrystalline Aluminum Nitride

    OpenAIRE

    Duarte, Matthew Albert

    2016-01-01

    Synthesis, processing and characterization of nanocrystalline aluminum nitride has been systematically studied. Non-carbon based gas nitridation was used to reduce nanocrystalline γ-alumina, having a grain size of ~80 nm. Single phase aluminum nitride powder was obtained at firing temperatures of 1200°C. Further processing of AlN powders was performed by CAPAD (Current Activated Pressure Assisted Densification) to obtain dense single phase aluminum nitride. Dense bulk aluminum nitride was ob...

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

    Science.gov (United States)

    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.

  12. Thermodynamic and transport properties of liquid gallium

    International Nuclear Information System (INIS)

    Park, H.Y.; Jhon, M.S.

    1982-01-01

    The significant structure theory of liquids has been successfully applied to liquid gallium. In this work, we have assumed that two structures exist simultaneously in liquid gallium. One is considerec as loosely close packed β-Ga-like structure and the other is remainder of solid α-Ga or α-Ga-like structure. This two structural model is introduced to construct the liquid partition function. Using the partition function, the thermodynamic and transport properties are calculated ever a wide temperature range. The calculated results are quite satisfactory when compared with the experimental results. (Author)

  13. Radiation damage of gallium arsenide production cells

    Science.gov (United States)

    Mardesich, N.; Joslin, D.; Garlick, J.; Lillington, D.; Gillanders, M.; Cavicchi, B.; Scott-Monck, J.; Kachare, R.; Anspaugh, B.

    1987-01-01

    High efficiency liquid phase epitaxy (LPE) gallium arsenide cells were irradiated with 1 Mev electrons up to fluences of 1 times 10 to the 16th power cm-2. Measurements of spectral response and dark and illuminated I-V data were made at each fluence and then, using computer codes, the experimental data was fitted to gallium arsenide cell models. In this way it was possible to determine the extent of the damage, and hence damage coefficients in both the emitter and base of the cell.

  14. Ternary nitrides for hydrogen storage: Li-B-N, Li-Al-N and Li-Ga-N systems

    International Nuclear Information System (INIS)

    Langmi, Henrietta W.; McGrady, G. Sean

    2008-01-01

    This paper reports an investigation of hydrogen storage performance of ternary nitrides based on lithium and the Group 13 elements boron, aluminum and gallium. These were prepared by ball milling Li 3 N together with the appropriate Group 13 nitride-BN, AlN or GaN. Powder X-ray diffraction of the products revealed that the ternary nitrides obtained are not the known Li 3 BN 2 , Li 3 AlN 2 and Li 3 GaN 2 phases. At 260 deg. C and 30 bar hydrogen pressure, the Li-Al-N ternary system initially absorbed 3.7 wt.% hydrogen, although this is not fully reversible. We observed, for the first time, hydrogen uptake by a pristine ternary nitride of Li and Al synthesized from the binary nitrides of the metals. While the Li-Ga-N ternary system also stored a significant amount of hydrogen, the storage capacity for the Li-B-N system was near zero. The hydrogenation reaction is believed to be similar to that of Li 3 N, and the enthalpies of hydrogen absorption for Li-Al-N and Li-Ga-N provide evidence that AlN and GaN, as well as the ball milling process, play a significant role in altering the thermodynamics of Li 3 N

  15. Optimization of time–temperature schedule for nitridation of silicon ...

    Indian Academy of Sciences (India)

    weight gain. Green compact of density 66%, the nitridation schedule was maneuvered for complete nitridation. Iron promotes nitridation reaction. Higher weight loss during nitridation of iron doped compact is the main cause of lower ...

  16. Design and analysis of novel photocatalytic materials

    Science.gov (United States)

    Boppana, Venkata Bharat Ram

    The development of sustainable sources of energy to decrease our dependence on non-renewable fossil fuels and the reduction of emissions causing global warming are important technological challenges of the 21st century. Production of solar fuels by photocatalysis is one potential route to reduce the impact of those problems. The most widely applied photocatalyst is TiO2 because it is stable, non-toxic and inexpensive. Still, it cannot utilize the solar spectrum efficiently as its band gap is 3.2 eV thus able to absorb only 3% of sun light. This thesis therefore explores multiple avenues towards improving the light absorption capability of semiconductor materials without loss in activity. To achieve this objective, the valence band hybridization method of band gap reduction was utilized. This technique is based on introducing new orbitals at the top of valence band of the semiconductor that can then hybridize with existing orbitals. The hybridization then raises the maximum of the valence band thereby reducing the band gap. This technique has the added advantage of increasing the mobility of oxidizing holes in the now dispersed valence band. In practice, this can be achieved by introducing N 2p or Sn 5s orbitals in the valence band of an oxide. We initially designed novel zinc gallium oxy-nitrides, with the spinel structure and band gaps in the visible region of the solar spectrum, by nitridation of a zinc gallate precursor produced by sol-gel synthesis. These spinel oxy-nitrides have band gaps of 2.5 to 2.7 eV, surface areas of 16 to 36 m 2/g, and nitrogen content less than 1.5%. They are active towards degradation of organic molecules in visible light. Density functional theory calculations show that this band gap reduction in part is associated with hybridization between the dopant N 2p states with Zn 3d orbitals at the top of the valence band. While spinel oxy-nitrides are produced under nitridation at 550°C, at higher temperatures they are consumed to form

  17. Influence of Plastic Deformation on Low Temperature Surface Hardening of Austenitic Stainless Steel by Gaseous Nitriding

    DEFF Research Database (Denmark)

    Bottoli, Federico; Winther, Grethe; Christiansen, Thomas Lundin

    2015-01-01

    This article addresses an investigation of the influence of plastic deformation on low temperature surface hardening by gaseous nitriding of two commercial austenitic stainless steels: AISI 304 and EN 1.4369. The materials were plastically deformed to different equivalent strains by uniaxial...... tension. Gaseous nitriding of the strained material was performed in ammonia gas at atmospheric pressure at 703 K. Microstructural characterization of the as-deformed states and the nitrided case produced included X-ray diffraction analysis, reflected light microscopy, microhardness testing. The results...

  18. Strain distribution and defect analysis in III-nitrides by dynamical AFM analysis

    International Nuclear Information System (INIS)

    Minj, Albert; Cavalcoli, Daniela; Cavallini, Anna; Gamarra, Piero; Di Forte Poisson, Marie-Antoinette

    2013-01-01

    Here, we report on significant material information provided by semi-contact phase-images in a wide range of hard III-nitride surfaces. We show that the phase contrast, which is fundamentally related to the energy dissipation during tip–surface interaction, is sensitive to the crystalline nature of the material and thus could potentially be used to determine the crystalline quality of thin nitride layers. Besides, we found that the structural defects, especially threading dislocations and cracks, act as selective sites where energy mainly dissipates. Consequently, in nitrides defects with very low dimensions can actually be imaged with phase-contrast imaging. (paper)

  19. Probing magnetoelastic coupling and structural changes in magnetoelectric gallium ferrite.

    Science.gov (United States)

    Mukherjee, Somdutta; Garg, Ashish; Gupta, Rajeev

    2011-11-09

    Temperature dependent x-ray diffraction and Raman spectroscopic studies were carried out on flux-grown single crystals of gallium ferrite with a Ga:Fe ratio of 0.9:1.1. Site occupancy calculations from the Rietveld refinement of the x-ray data led to an estimated magnetic moment of ~0.60 μ(B)/f.u. which was in good agreement with the experimental data. A combination of these two measurements indicates that there is no structural phase transition in the material between 18 and 700 K. A detailed line shape analysis of the Raman mode at ~374 cm(-1) revealed a discontinuity in the peak position data indicating the presence of spin-phonon coupling in gallium ferrite. A correlation of the peak frequency with the magnetization data led to two distinct regions across a temperature ~180 K with appreciable change in the spin-phonon coupling strength from ~0.9 (T change in the coupling strength at ~180 K strongly suggests an altered spin dynamics across this temperature. © 2011 IOP Publishing Ltd

  20. Probing magnetoelastic coupling and structural changes in magnetoelectric gallium ferrite

    International Nuclear Information System (INIS)

    Mukherjee, Somdutta; Gupta, Rajeev; Garg, Ashish

    2011-01-01

    Temperature dependent x-ray diffraction and Raman spectroscopic studies were carried out on flux-grown single crystals of gallium ferrite with a Ga:Fe ratio of 0.9:1.1. Site occupancy calculations from the Rietveld refinement of the x-ray data led to an estimated magnetic moment of ∼0.60 μ B /f.u. which was in good agreement with the experimental data. A combination of these two measurements indicates that there is no structural phase transition in the material between 18 and 700 K. A detailed line shape analysis of the Raman mode at ∼374 cm -1 revealed a discontinuity in the peak position data indicating the presence of spin-phonon coupling in gallium ferrite. A correlation of the peak frequency with the magnetization data led to two distinct regions across a temperature ∼180 K with appreciable change in the spin-phonon coupling strength from ∼0.9 (T -1 (180 K c ). This abrupt change in the coupling strength at ∼180 K strongly suggests an altered spin dynamics across this temperature. (paper)

  1. Hardness and thermal stability of cubic silicon nitride

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Kragh, Flemming; Frost, D. J.

    2001-01-01

    The hardness and thermal stability of cubic spinel silicon nitride (c-Si3N4), synthesized under high-pressure and high-temperature conditions, have been studied by microindentation measurements, and x-ray powder diffraction and scanning electron microscopy, respectively The phase at ambient...... temperature has an average hardness of 35.31 GPa, slightly larger than SiO2 stishovite, which is often referred to as the third hardest material after diamond and cubic boron nitride. The cubic phase is stable up to 1673 K in air. At 1873 K, alpha -and beta -Si3N4 phases are observed, indicating a phase...

  2. Synthesis and Optimization of the Sintering Kinetics of Actinide Nitrides

    International Nuclear Information System (INIS)

    Butt, Drryl P.; Jaques, Brian

    2009-01-01

    Research conducted for this NERI project has advanced the understanding and feasibility of nitride nuclear fuel processing. In order to perform this research, necessary laboratory infrastructure was developed; including basic facilities and experimental equipment. Notable accomplishments from this project include: the synthesis of uranium, dysprosium, and cerium nitrides using a novel, low-cost mechanical method at room temperature; the synthesis of phase pure UN, DyN, and CeN using thermal methods; and the sintering of UN and (U x , Dy 1-x )N (0.7 (le) X (le) 1) pellets from phase pure powder that was synthesized in the Advanced Materials Laboratory at Boise State University.

  3. Synthesis and Optimization of the Sintering Kinetics of Actinide Nitrides

    Energy Technology Data Exchange (ETDEWEB)

    Drryl P. Butt; Brian Jaques

    2009-03-31

    Research conducted for this NERI project has advanced the understanding and feasibility of nitride nuclear fuel processing. In order to perform this research, necessary laboratory infrastructure was developed; including basic facilities and experimental equipment. Notable accomplishments from this project include: the synthesis of uranium, dysprosium, and cerium nitrides using a novel, low-cost mechanical method at room temperature; the synthesis of phase pure UN, DyN, and CeN using thermal methods; and the sintering of UN and (Ux, Dy1-x)N (0.7 ≤ X ≤ 1) pellets from phase pure powder that was synthesized in the Advanced Materials Laboratory at Boise State University.

  4. Damage initiation and evolution in silicon nitride under\

    Czech Academy of Sciences Publication Activity Database

    Raga, R.; Khader, I.; Chlup, Zdeněk; Kailer, A.

    360-361, AUG (2016), s. 147-159 ISSN 0043-1648 EU Projects: European Commission(XE) 263476 - ROLICER Institutional support: RVO:68081723 Keywords : Silicon nitride * Rollingcontactfatigue * Subsurface damage Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 2.531, year: 2016

  5. Continuous Fiber Ceramic Composite (CFCC) Program: Gaseous Nitridation

    Energy Technology Data Exchange (ETDEWEB)

    R. Suplinskas G. DiBona; W. Grant

    2001-10-29

    Textron has developed a mature process for the fabrication of continuous fiber ceramic composite (CFCC) tubes for application in the aluminum processing and casting industry. The major milestones in this project are System Composition; Matrix Formulation; Preform Fabrication; Nitridation; Material Characterization; Component Evaluation

  6. Microstructure characterization of fluidized bed nitrided Fe–Si and ...

    Indian Academy of Sciences (India)

    Unknown

    nitrogen atoms and chemical surface modifications produce structural modifications leading to substantial improve- ments in the properties of the material (Billard et al 1990;. Kooi et al 1994; Boettger et al 1997; Niederdrenk et al. 1996; Schaaf 1998). The compound layer resulting from the nitriding treatment meets some of ...

  7. Assessment of industrial nitriding processes for fusion steel applications

    Directory of Open Access Journals (Sweden)

    M. Seitz

    2017-12-01

    While conventional gas nitriding showed no beneficial effect on the material, the Hard-Inox-P treatment showed a significant improvement in the cycles to failure while retaining an acceptable toughness. Microstructural investigations showed the presence of very small chromium- and nitrogen-rich precipitates in the area close to the surface.

  8. Effect of microstructure on the high temperature strength of nitride ...

    Indian Academy of Sciences (India)

    Unknown

    chrome, Model No. Autoscan 60, USA). Existence of phases (α-, β-Si3N4, SiO2, etc) were determined by XRD technique. Both room temperature and high temperature. MOR were determined by 4-point loading in a bending ... Properties of nitride bonded SiC composite materials. Density (g/cm3). Open porosity Mean pore.

  9. Anisotropy of the magnetic susceptibility of gallium

    Science.gov (United States)

    Pankey, T.

    1960-01-01

    The bulk magnetic susceptibilities of single gallium crystals and polycrystalline gallium spheres were measured at 25??C. The following anisotropic diamagnetic susceptibilities were found: a axis (-0.119??0. 001)??10-6 emu/g, b axis (-0.416??0.002)??10 -6 emu/g, and c axis (-0.229??0.001) emu/g. The susceptibility of the polycrystalline spheres, assumed to be the average value for the bulk susceptibility of gallium, was (-0.257??0.003)??10-6 emu/g at 25??C, and (-0.299??0.003)??10-6 emu/g at -196??C. The susceptibility of liquid gallium was (0.0031??0.001) ??10-6 emu/g at 30??C and 100??C. Rotational diagrams of the susceptibilities in the three orthogonal planes of the unit cell were not sinusoidal. The anisotropy in the single crystals was presumably caused by the partial overlap of Brillouin zone boundaries by the Fermi-energy surface. The large change in susceptibility associated with the change in state was attributed to the absence of effective mass influence in the liquid state. ?? 1960 The American Institute of Physics.

  10. Thermodynamic binding constants for gallium transferrin

    Energy Technology Data Exchange (ETDEWEB)

    Harris, W.R.; Pecoraro, V.L.

    1983-01-18

    Gallium-67 is widely used as an imaging agent for tumors and inflammatory abscesses. It is well stablished that Ga/sup 3 +/ travels through the circulatory system bound to the serum iron transport protein transferrin and that this protein binding is an essential step in tumor localization. However, there have been conflicting reports on the magnitude of the gallium-transferrin binding constants. Therefore, thermodynamic binding constants for gallium complexation at the two specific metal binding sites of human serum transferrin at pH 7.4 and 5 mM NaHCO/sub 3/ have been determined by UV difference spectroscopy. The conditional constants calculated for 27 mM NaHCO/sub 3/ are log K/sub 1/* = 20.3 and log K/sub 2/* = 19.3. These results are discussed in relation to the thermodynamics of transferrin binding of Fe/sup 3 +/ and to previous reports on gallium binding. The strength of transferrin complexation is also compared to that of a series of low molecular weight ligands by using calculated pM values (pM = -log (Ga(H/sub 2/O)/sub 6/)) to express the effective binding strength at pH 7.4.

  11. Gallium Electromagnetic (GEM) Thruster Performance Measurements

    Science.gov (United States)

    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.

  12. One dimensional aluminum nitride nanostructures: synthesis, structural, and luminescence properties.

    Science.gov (United States)

    Mousavi, S H; Gharavi, M A; Haratizadeh, H; Kitai, A; de Oliveira, P W

    2011-09-01

    Aluminum nitride (AIN) is a direct bandgap semiconductor with a bandgap about 6.1 eV at room temperature, the largest among semiconductors. This paper emphasizes experimental results of the growth and optical properties of AIN nanostructures by direct nitridation. The nitridation process was performed by chemical vapor deposition method with nitrogen (N2) gas flow. AIN nanostructures were analyzed by scanning electron microscope (SEM) equipped with energy-dispersive X-ray (EDX) spectroscope and photoluminescence (PL) spectroscopy. AIN nanowires with different widths from ultrathin to thick were synthesized with this method. All of the samples had high purity without presence of any other material in EDX spectrum. The PL spectra were obtained by a 325-nm helium-cadmium (He-Cd) laser as the excitation source showing high-intensity light emitting visible wavelengths for these structures at room temperature.

  13. Kinetic modelling of chlorination of nitrided ilmenite using MATLAB

    Energy Technology Data Exchange (ETDEWEB)

    Ramakrishnan, Sivakumar, E-mail: srsivakumar@usm.my; Kwok, Teong Chen, E-mail: ctck@live.com; Hamid, Sheikh Abdul Rezan Sheikh Abdul, E-mail: rezanshk@gmail.com [School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, 14300, Nibong Tebal, Penang (Malaysia)

    2016-07-19

    In the present study, chlorination of nitride ilmenite using 2{sup k} factorial design was investigated. The reduction experiments were carried out in a temperature range of 400°C to 500°C, chlorination duration from 1 hour to 3 hours and using different type of carbon reactant. Phases of raw materials and reduced samples were analyzed by X-ray diffraction (XRD). Ilmenite was reduced to TiO{sub x}C{sub y}N{sub z} through carbothermal and nitridation for further chlorination into titanium tetrachloride. The Design of Experiment analysis suggested that the types of carbon reactant contribute most influence to the extent of chlorination of nitride ilmenite. The extent of chlorination was highest at 500°C with 3 hours chlorination time and carbon nanotube as carbon reactant.

  14. Colloidal characterization of silicon nitride and silicon carbide

    Science.gov (United States)

    Feke, Donald L.

    1986-01-01

    The colloidal behavior of aqueous ceramic slips strongly affects the forming and sintering behavior and the ultimate mechanical strength of the final ceramic product. The colloidal behavior of these materials, which is dominated by electrical interactions between the particles, is complex due to the strong interaction of the solids with the processing fluids. A surface titration methodology, modified to account for this interaction, was developed and used to provide fundamental insights into the interfacial chemistry of these systems. Various powder pretreatment strategies were explored to differentiate between true surface chemistry and artifacts due to exposure history. The colloidal behavior of both silicon nitride and carbide is dominated by silanol groups on the powder surfaces. However, the colloid chemistry of silicon nitride is apparently influenced by an additional amine group. With the proper powder treatments, silicon nitride and carbide powder can be made to appear colloidally equivalent. The impact of these results on processing control will be discussed.

  15. Morphology of interior interfaces in dilute nitride III/V material systems; Morphologie innerer Grenzflaechen in verduennt stickstoffhaltigen III/V-Materialsystemen

    Energy Technology Data Exchange (ETDEWEB)

    Oberhoff, S.

    2007-12-03

    This study aims to clarify structure formation processes in dilute N-containing III/V-based material systems, using highly selective etching methods and subsequent atomic force microscopy (AFM) to expose and analyse interior interfaces. In the first part of this study it was directly proved for the first time that adding Sb during growth interruption inhibits the GI-induced structural phase transition and reduces the diffusivity on GaAs and (GaIn)(NAs) surfaces. However, applying Sb during GI does not affect the driving force of the structural phase transition. Therefore a fundamental analysis about the incorporation of Sb into GaAs, Ga(NAs) and (GaIn)(NAs) was carried out in the second part of the study. Using a combination of high resolution X-ray diffraction, transmission electron microscopy and SIMS measurements, it was verified that incorporating Sb into (GaIn)(NAs) causes an increase of the In content and a decrease of the N content. In the third part of the study, novel etching methods for the GaP-based material system Ga(NAsP) are introduced which provide the opportunity to analyse structure formation processes on interior interfaces in this material system by AFM. (orig.)

  16. Method for exfoliation of hexagonal boron nitride

    Science.gov (United States)

    Lin, Yi (Inventor); Connell, John W. (Inventor)

    2012-01-01

    A new method is disclosed for the exfoliation of hexagonal boron nitride into mono- and few-layered nanosheets (or nanoplatelets, nanomesh, nanoribbons). The method does not necessarily require high temperature or vacuum, but uses commercially available h-BN powders (or those derived from these materials, bulk crystals) and only requires wet chemical processing. The method is facile, cost efficient, and scalable. The resultant exfoliated h-BN is dispersible in an organic solvent or water thus amenable for solution processing for unique microelectronic or composite applications.

  17. Thermodynamic property evaluation and magnetic refrigeration cycle analysis for gadolinium gallium garnet

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, R.W.

    1994-12-01

    Based on relevant material property data and previous model formulations, a magnetothermodynamic property map for gadolinium gallium garnet (Gd{sub 3}Ga{sub 5}O{sub 12}) was adapted for refrigeration cycle analysis in the temperature range 4-40 K and the magnetic field range 0-6 T. Employing methods similar to those previously developed for other materials and temperature ranges, assessments of limitations and relative performance were made for Carnot, ideal regenerative, and pseudo-constant field regenerative cycles. It was found that although Carnot cycle limitations on available temperature lift for gadolinium gallium garnet are not as severe as the limitations for materials previously examined, considerable improvement in cooling capacity and temperature lift combinations can be achieved by using regenerative cycles if serious loss mechanisms are avoided.

  18. Magnetic refrigeration cycle analysis using selected thermodynamic property characterizations for gadolinium gallium garnet

    International Nuclear Information System (INIS)

    Murphy, R.W.

    1992-01-01

    Magneto-thermodynamic property characterizations were selected, adapted, and compared to material property data for gadolinium gallium garnet in the temperature range 4--40 K and magnetic field range 0--6 T. The most appropriate formulations were incorporated into a model in which methods similar to those previously developed for other materials and temperature ranges were used to make limitation and relative performance assessments of Carnot, ideal regenerative, and pseudo-constant field regenerative cycles. Analysis showed that although Carnot cycle limitations on available temperature lift for gadolinium gallium garnet are not as severe as those for materials previously examined, substantial improvements in cooling capacity/temperature lift combinations can be achieved using regenerative cycles within specified fields limits if significant loss mechanisms are mitigated

  19. Boron nitride converted carbon fiber

    Science.gov (United States)

    Rousseas, Michael; Mickelson, William; Zettl, Alexander K.

    2016-04-05

    This disclosure provides systems, methods, and apparatus related to boron nitride converted carbon fiber. In one aspect, a method may include the operations of providing boron oxide and carbon fiber, heating the boron oxide to melt the boron oxide and heating the carbon fiber, mixing a nitrogen-containing gas with boron oxide vapor from molten boron oxide, and converting at least a portion of the carbon fiber to boron nitride.

  20. Gallium 67 scintigraphy in glomerular disease

    Energy Technology Data Exchange (ETDEWEB)

    Bakir, A.A.; Lopez-Majano, V.; Levy, P.S.; Rhee, H.L.; Dunea, G.

    1988-12-01

    To evaluate the diagnostic usefulness of gallium 67 scintigraphy in glomerular disease, 45 patients with various glomerulopathies, excluding lupus nephritis and renal vasculitis, were studied. Persistent renal visualization 48 hours after the gallium injection, a positive scintigram, was graded as + (less than), ++ (equal to), and +++ (greater than) the hepatic uptake. Positive scintigrams were seen in ten of 16 cases of focal segmental glomerulosclerosis, six of 11 cases of proliferative glomerulonephritis, and one case of minimal change, and one of two cases of membranous nephropathy; also in three of six cases of sickle glomerulopathy, two cases of diabetic neuropathy, one of two cases of amyloidosis, and one case of mild chronic allograft rejection. The 25 patients with positive scans were younger than the 20 with negative scans (31 +/- 12 v 42 +/- 17 years; P less than 0.01), and exhibited greater proteinuria (8.19 +/- 7.96 v 2.9 +/- 2.3 S/d; P less than 0.01) and lower serum creatinine values (2 +/- 2 v 4.1 +/- 2.8 mg/dL; P less than 0.01). The amount of proteinuria correlated directly with the intensity grade of the gallium image (P less than 0.02), but there was no correlation between the biopsy diagnosis and the outcome of the gallium scan. It was concluded that gallium scintigraphy is not useful in the differential diagnosis of the glomerular diseases under discussion. Younger patients with good renal function and heavy proteinuria are likely to have a positive renal scintigram regardless of the underlying glomerulopathy.

  1. Nitride stabilized core/shell nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Kuttiyiel, Kurian Abraham; Sasaki, Kotaro; Adzic, Radoslav R.

    2018-01-30

    Nitride stabilized metal nanoparticles and methods for their manufacture are disclosed. In one embodiment the metal nanoparticles have a continuous and nonporous noble metal shell with a nitride-stabilized non-noble metal core. The nitride-stabilized core provides a stabilizing effect under high oxidizing conditions suppressing the noble metal dissolution during potential cycling. The nitride stabilized nanoparticles may be fabricated by a process in which a core is coated with a shell layer that encapsulates the entire core. Introduction of nitrogen into the core by annealing produces metal nitride(s) that are less susceptible to dissolution during potential cycling under high oxidizing conditions.

  2. Zirconium nitride hard coatings

    International Nuclear Information System (INIS)

    Roman, Daiane; Amorim, Cintia Lugnani Gomes de; Soares, Gabriel Vieira; Figueroa, Carlos Alejandro; Baumvol, Israel Jacob Rabin; Basso, Rodrigo Leonardo de Oliveira

    2010-01-01

    Zirconium nitride (ZrN) nanometric films were deposited onto different substrates, in order to study the surface crystalline microstructure and also to investigate the electrochemical behavior to obtain a better composition that minimizes corrosion reactions. The coatings were produced by physical vapor deposition (PVD). The influence of the nitrogen partial pressure, deposition time and temperature over the surface properties was studied. Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and corrosion experiments were performed to characterize the ZrN hard coatings. The ZrN films properties and microstructure changes according to the deposition parameters. The corrosion resistance increases with temperature used in the films deposition. Corrosion tests show that ZrN coating deposited by PVD onto titanium substrate can improve the corrosion resistance. (author)

  3. III-Nitride Vertical-Cavity Surface-Emitting Lasers

    Science.gov (United States)

    Leonard, John T.

    Vertical-cavity surface-emitting lasers (VCSELs) have a long history of development in GaAs-based and InP-based systems, however III-nitride VCSELs research is still in its infancy. Yet, over the past several years we have made dramatic improvements in the lasing characteristics of these highly complex devices. Specifically, we have reduced the threshold current density from ˜100 kA/cm2 to ˜3 kA/cm2, while simultaneously increasing the output power from ˜10 muW to ˜550 muW. These developments have primarily come about by focusing on the aperture design and intracavity contact design for flip-chip dual dielectric DBR III-nitride VCSELs. We have carried out a number of studies developing an Al ion implanted aperture (IIA) and photoelectrochemically etched aperture (PECA), while simultaneously improving the quality of tin-doped indium oxide (ITO) intracavity contacts, and demonstrating the first III-nitride VCSEL with an n-GaN tunnel junction intracavity contact. Beyond these most notable research fronts, we have analyzed numerous other parameters, including epitaxial growth, flip-chip bonding, substrate removal, and more, bringing further improvement to III-nitride VCSEL performance and yield. This thesis aims to give a comprehensive discussion of the relevant underlying concepts for nonpolar VCSELs, while detailing our specific experimental advances. In Section 1, we give an overview of the applications of VCSELs generally, before describing some of the potential applications for III-nitride VCSELs. This is followed by a summary of the different material systems used to fabricate VCSELs, before going into detail on the basic design principles for developing III-nitride VCSELs. In Section 2, we outline the basic process and geometry for fabricating flip-chip nonpolar VCSELs with different aperture and intracavity contact designs. Finally, in Section 3 and 4, we delve into the experimental results achieved in the last several years, beginning with a discussion on

  4. Solvothermal synthesis, crystal structure, and second-order nonlinear optical properties of a new noncentrosymmetric gallium-organic framework material, [N(C{sub 3}H{sub 7}){sub 4}]{sub 3}Ga{sub 3}[C{sub 6}H{sub 3}(CO{sub 2}){sub 3}]{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Dong Woo; Jo, Vinna [Department of Chemistry, Chung-Ang University, Seoul, 156-756 (Korea, Republic of); Ok, Kang Min, E-mail: kmok@cau.ac.kr [Department of Chemistry, Chung-Ang University, Seoul, 156-756 (Korea, Republic of)

    2012-10-15

    A novel noncentrosymmetric (NCS) gallium-organic framework material, [N(C{sub 3}H{sub 7}){sub 4}]{sub 3}Ga{sub 3}[C{sub 6}H{sub 3}(CO{sub 2}){sub 3}]{sub 4} (CAUMOF-11) has been synthesized by a solvothermal reaction using Ga(NO{sub 3}){sub 3}{center_dot}xH{sub 2}O, 1,3,5-C{sub 6}H{sub 3}(CO{sub 2}H){sub 3}, N(C{sub 3}H{sub 7}){sub 4}Cl, HNO{sub 3}, and HCON(CH{sub 3}){sub 2} at 180 Degree-Sign C. The structure of the reported material has been determined by single-crystal X-ray diffraction. CAUMOF-11 has an anionic three-dimensional framework with aligned four-coordinate GaO{sub 4} tetrahedra and 1,3,5-benzenetricarboxylate groups. Tetrapropylammonim cations reside within the channel and maintain the charge balance. Detailed structural analyses with full characterization including infrared spectroscopy, thermogravimetric analysis, elemental analysis, ion-exchange reactions, topotactic decomposition, and gas adsorption experiments are reported. Powder second-harmonic generating (SHG) measurements on CAUMOF-11, using 1064 nm radiation, exhibit SHG efficiency of 15 times that of {alpha}-SiO{sub 2} and the material is phase-matchable (type-1). - Graphical Abstract: Second-order nonlinear optical measurements on CAUMOF-11 reveal that the material is phase-matchable (type-1) with SHG efficiency of 15 times that of {alpha}-SiO{sub 2}. Highlights: Black-Right-Pointing-Pointer A new NCS Ga-organic framework was solvothermally synthesized. Black-Right-Pointing-Pointer CAUMOF-11 exhibits SHG efficiency of 15 times that of {alpha}-SiO{sub 2}. Black-Right-Pointing-Pointer Thermal decomposition of CAUMOF-11 crystal maintains the original morphology.

  5. Role of Lysosomes in gallium concentration by mammalian tissues

    International Nuclear Information System (INIS)

    Berry, J.P.; Galle, S.; Escaig, F.; Poupon, M.F.

    1984-01-01

    Gallium is used as a tracer in nuclear medicine for the localization of malignant tumors. Two microanalytical methods, electron probe X ray analysis (EPMA) and ion mass analysis (IAM) were used to study gallium incorporation in normal tissues (kidney, liver, mammary gland, bone marrow, bone tissue) and in experimental tumors. The very high sensitivity of IMA makes possible the detection of very low cencentration of gallium (1 ppm) with a spatial resolution of 0.5 μm, on the other hand, EPMA of lower sensitivity (100 ppm) makes possible the relation between the gallium concentration and the ultrastructure of the cell. It was shown that gallium is concentrated in the lysosomes of both types of tissues, where it is precipitated in an insoluble form. In addition, gallium is systematically combined with phosphorus in these precipitates. These observations suggest an active intralysosomal concentrating mechanism related to the presence of local phosphatase activity

  6. Determination of gallium in flint clay by neutron activation analysis

    International Nuclear Information System (INIS)

    Padova, A.; Even, O.

    1975-01-01

    Neutron activation analysis was applied to determine gallium traces in different flint clay samples found in Israel. The principal 835 KeV gamma ray of gallium-72 was measured with a 60 cm 2 Ge(Li) spectrometer in conjunction with a Packard 4000 channel analyzer and Wang table computer, model 720 C. Samples were weighed into polyethylene vials, sealed and inserted into polyethylene rabbit. Gallium metal and gallium oxide used as standards were similarly prepared for irradiation for 10 minutes in the I.R.R.I., at a thermal flux of 3.5x10 12 n/cm 2 sec. Careful calibration of the spectrometer and judicious choice of cooling time eliminate the influence of such elements as europium-152, and sodium-24 and make possible the determination of gallium without prior chemical separation. Representative Israel flint clay samples contain about 55 ppm gallium. (B.G.)

  7. Aluminum nitride insulating films for MOSFET devices

    Science.gov (United States)

    Lewicki, G. W.; Maserjian, J.

    1972-01-01

    Application of aluminum nitrides as electrical insulator for electric capacitors is discussed. Electrical properties of aluminum nitrides are analyzed and specific use with field effect transistors is defined. Operational limits of field effect transistors are developed.

  8. Boron Nitride Nanotubes for Spintronics

    Directory of Open Access Journals (Sweden)

    Kamal B. Dhungana

    2014-09-01

    Full Text Available With the end of Moore’s law in sight, researchers are in search of an alternative approach to manipulate information. Spintronics or spin-based electronics, which uses the spin state of electrons to store, process and communicate information, offers exciting opportunities to sustain the current growth in the information industry. For example, the discovery of the giant magneto resistance (GMR effect, which provides the foundation behind modern high density data storage devices, is an important success story of spintronics; GMR-based sensors have wide applications, ranging from automotive industry to biology. In recent years, with the tremendous progress in nanotechnology, spintronics has crossed the boundary of conventional, all metallic, solid state multi-layered structures to reach a new frontier, where nanostructures provide a pathway for the spin-carriers. Different materials such as organic and inorganic nanostructures are explored for possible applications in spintronics. In this short review, we focus on the boron nitride nanotube (BNNT, which has recently been explored for possible applications in spintronics. Unlike many organic materials, BNNTs offer higher thermal stability and higher resistance to oxidation. It has been reported that the metal-free fluorinated BNNT exhibits long range ferromagnetic spin ordering, which is stable at a temperature much higher than room temperature. Due to their large band gap, BNNTs are also explored as a tunnel magneto resistance device. In addition, the F-BNNT has recently been predicted as an ideal spin-filter. The purpose of this review is to highlight these recent progresses so that a concerted effort by both experimentalists and theorists can be carried out in the future to realize the true potential of BNNT-based spintronics.

  9. Survey of the market, supply and availability of gallium

    Energy Technology Data Exchange (ETDEWEB)

    Rosi, F.D.

    1980-07-01

    The objective of this study was to assess the present consumption and supply of gallium, its potential availability in the satellite power system (SPS) implementation time frame, and commercial and new processing methods for increasing the production of gallium. Findings are reported in detail. The findings strongly suggest that with proper long range planning adequate gallium would be available from free-enterprise world supplies of bauxite for SPS implementation.

  10. Phase Change of Gallium Enables Highly Reversible and Switchable Adhesion.

    Science.gov (United States)

    Ye, Zhou; Lum, Guo Zhan; Song, Sukho; Rich, Steven; Sitti, Metin

    2016-07-01

    Gallium exhibits highly reversible and switchable adhesion when it undergoes a solid-liquid phase transition. The robustness of gallium is notable as it exhibits strong performance on a wide range of smooth and rough surfaces, under both dry and wet conditions. Gallium may therefore find numerous applications in transfer printing, robotics, electronic packaging, and biomedicine. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Inflammatory pseudotumor: A gallium-avid mobile mesenteric mass

    International Nuclear Information System (INIS)

    Auringer, S.T.; Scott, M.D.; Sumner, T.E.

    1991-01-01

    An 8-yr-old boy with a 1-mo history of culture-negative fever and anemia underwent gallium, ultrasound, and computed tomography studies as part of the evaluation of a fever of unknown origin. These studies revealed a mobile gallium-avid solid abdominal mass subsequently proven to be an inflammatory pseudotumor of the mesentery, a rare benign mass. This report documents the gallium-avid nature of this rare lesion and discusses associated characteristic clinical, pathologic, and radiographic features

  12. Psoas abscess localization by gallium scan in aplastic anemia

    International Nuclear Information System (INIS)

    Oster, M.W.; Gelrud, L.G.; Lotz, M.J.; Herzig, G.P.; Johnston, G.S.

    1975-01-01

    Gallium 67 scanning is an effective method of detecting inflammatory lesions, especially abscesses. A 10-year-old boy with aplastic anemia and severe leukopenia and granulocytopenia had a psoas abscess diagnosed by gallium scan. The patient died with Candida sepsis 18 days after bone marrow transplantation. At autopsy, a chronic psoas abscess with Candida was found. The gallium scan offers a clinically effective and noninvasive means of evaluating suspected infection in the granulocytopenia patient. (U.S.)

  13. Use of high-thermal conductive aluminum nitride based ceramics in vacuum UHF electronic devices

    Directory of Open Access Journals (Sweden)

    Chasnyk V. I.

    2013-06-01

    Full Text Available Analysis of properties and characteristics of the alumina, beryllium oxide and aluminum nitride based ceramic materials used in UHF electronic devices has been made. It was shown that the complex of parameters including structural and functional characteristics of the high-thermal conductive aluminum nitride ceramics prevail over all types of alumina ceramics and is not lower than the same characteristics of the beryllium oxide ceramics especially at the temperatures higher than 450 °C. The examples of the prevailing use of the aluminum nitride ceramics inside vacuum UHF-region devices: TWT’s and klystrons.

  14. Metachromasy of methylene blue due to aggregation over phosphate-modified polymeric carbon nitride

    Science.gov (United States)

    Lakshminarasimhan, N.; Sangeetha, D. N.; Nivetha, G.

    2017-05-01

    Polymeric carbon nitride in graphitic form (g-C3N4) is an emerging visible light active photocatalyst. In this work, phosphate-modified polymeric carbon nitride (PCN) was synthesized by thermal condensation of melamine in the presence of ammonium dihydrogen phosphate (ADP). The addition of PCN to methylene blue (MB) solution showed the color intensification. The hypsochromic shift in the absorption spectrum of MB is due to metachromasy, a phenomenon in which aggregation of dye molecules occurs over the surface of a material. The polymerization of melamine into carbon nitride and MB trimerization depend on the amount of ADP and nature of phosphate species, respectively.

  15. Studies on the biological behaviour of gallium-67 citrate

    International Nuclear Information System (INIS)

    Sephton, R.G.; Harris, A.

    1975-01-01

    Gallium-67 citrate, though not a universal tumour seeker, has nevertheless a remarkable, unexplained affinity in vivo for some malignant deposits. Its value as a clinical tracer would be enhanced by a clearer understanding of its biological significance. This paper describes studies using gallium-67 in experimental animals and in cell cultures. Mice bearing various transplanted solid tumours (mostly lymphomas and myelomas) have been examined for gallium-67 concentrations in tumour, other soft tissues and bone. Subcellular fractionation confirms intracellular tracer in lysosomes, for gallium-avid and neutral tumours and for liver but, to judge from acid phosphatase burdens of these tissues, gallium-67 uptake may not bear simple correlation with lysosomal activity. Gallium-67 distributions differ between juvenile and mature animals and, in either case, changes favouring soft tissue uptake over bone can occur even within days of tumour inoculation. Mice reacting to allogeneic spleen cell injections (GVH) also show increased soft tissue retention of tracer. Tumour cells exposed in culture to gallium-67 show an increasing uptake with time, reaching 5-10 times the specific activity of the culture medium within 48 hours. For several lines at least, a low (approximately 1%) concentration in the medium of mouse and even human serum can strikingly increase gallium-67 uptake by the cells. Subcellular fractionation shows again a lysosomal spectrum for both stimulated and unstimulated cell-bound gallium. (author)

  16. Inelastic neutron scattering on solid and liquid gallium

    International Nuclear Information System (INIS)

    Luzny, W.; Niziol, S.; Mayer, J.; Natkaniec, I.

    1989-01-01

    In order to find a physical property which would be able to distinguish the liquid gallium obtained by melting the α-phase and the liquid gallium annealed at temperatures higher than 333 K, measurements of incoherent inelastic neutron scattering (IINS) spectra were made with the aim to observe changes in the excitation spectrum occuring during the melting and then annealing of liquid gallium. The results of neutron experiments have shown that the diatomic-type structure of α-Ga is destroyed just in the melting point and that the dynamic properties of liquid gallium do not depend on the thermal history of the sample

  17. Anomalous piezoelectricity in two-dimensional graphene nitride nanosheets

    Science.gov (United States)

    Zelisko, Matthew; Hanlumyuang, Yuranan; Yang, Shubin; Liu, Yuanming; Lei, Chihou; Li, Jiangyu; Ajayan, Pulickel M.; Sharma, Pradeep

    2014-06-01

    Piezoelectricity is a unique property of materials that permits the conversion of mechanical stimuli into electrical and vice versa. On the basis of crystal symmetry considerations, pristine carbon nitride (C3N4) in its various forms is non-piezoelectric. Here we find clear evidence via piezoresponse force microscopy and quantum mechanical calculations that both atomically thin and layered graphitic carbon nitride, or graphene nitride, nanosheets exhibit anomalous piezoelectricity. Insights from ab inito calculations indicate that the emergence of piezoelectricity in this material is due to the fact that a stable phase of graphene nitride nanosheet is riddled with regularly spaced triangular holes. These non-centrosymmetric pores, and the universal presence of flexoelectricity in all dielectrics, lead to the manifestation of the apparent and experimentally verified piezoelectric response. Quantitatively, an e11 piezoelectric coefficient of 0.758 C m-2 is predicted for C3N4 superlattice, significantly larger than that of the commonly compared α-quartz.

  18. Optimal power settings of aluminum gallium arsenide lasers in caries inhibition ? An in vitro study

    OpenAIRE

    Sharma, Sonali; Hegde, Mithra N; Sadananda, Vandana; Mathews, Blessen

    2016-01-01

    Context: Incipient carious lesions are characterized by subsurface dissolution due to more fluoride ions in the 50-100 microns of the tooth′s outer surface. Aims: To determine an optimal power setting for 810 nm aluminum gallium arsenide laser for caries inhibition. Materials and Methods: Fifty-four caries-free extracted teeth were sectioned mesiodistally. The samples were divided into 18 groups for each power setting being evaluated. Each group had six samples. The laser used is 810 n...

  19. Gallium isotopic evidence for extensive volatile loss from the Moon during its formation

    OpenAIRE

    Kato, Chizu; Moynier, Fr?d?ric

    2017-01-01

    The distribution and isotopic composition of volatile elements in planetary materials holds a key to the characterization of the early solar system and the Moon's formation. The Moon and Earth are chemically and isotopically very similar. However, the Moon is highly depleted in volatile elements and the origin of this depletion is still debated. We present gallium isotopic and elemental measurements in a large set of lunar samples to constrain the origin of this volatile depletion. We show th...

  20. Chemistry and Pharmacokinetics of Gallium Maltolate, a Compound With High Oral Gallium Bioavailability

    OpenAIRE

    Bernstein, Lawrence R.; Tanner, Trevor; Godfrey, Claire; Noll, Bruce

    2000-01-01

    Gallium maltolate, tris(3-hydroxy-2-methyl-4H-pyran-4-onato)gallium (GaM), is an orally active gallium compound for therapeutic use. It is moderately soluble in water (10.7 ± 0.9 mg/mL at 25∘C) with an octanol partition coefficient of 0.41±0.08. The molecule is electrically neutral in aqueous solution at neutral pH; a dilute aqueous solution (2.5 ×10−-5 M) showed little dissociation at pH 5.5-8.0. Single crystal X-ray diffraction analysis found the GaM molecule to consist of three maltolate l...

  1. Conduction electrons in solid and liquid gallium

    International Nuclear Information System (INIS)

    Greuter, F.; Oelhafen, P.

    1979-01-01

    We have studied the photoemission properties of liquid, supercooled and crystalline gallium with photon energies up to 6.5 eV. The spectra of the liquid phase are well described by the free electron model, whereas in the solid the density of states is reduced near the Fermi level. The observed changes in the electronic structure at the melting point are explained by the essential change in the ionic short range order. (orig.)

  2. A Gallium multiphase equation of state

    Energy Technology Data Exchange (ETDEWEB)

    Crockett, Scott D [Los Alamos National Laboratory; Greeff, Carl [Los Alamos National Laboratory

    2009-01-01

    A new SESAME multiphase Gallium equation of state (EOS) has been developed. The equation of state includes three of the solid phases (Ga I, Ga II, Ga III) and a fluid phase (liquid/gas). The EOS includes consistent latent heat between the phases. We compare the results to the liquid Hugoniol data. We also explore the possibility of re-freezing via dynamic means such as isentropic and shock compression.

  3. Synthesis of double condensed cesium gallium phosphates

    Energy Technology Data Exchange (ETDEWEB)

    Chudinova, N.N.; Grunze, I.; Guzeeva, L.S.; Avaliani, M.A.

    1987-09-01

    By crystallization from melts of polyphosphoric acids there are obtained double condensed phosphates of cesium and gallium of the following compositions: Cs/sub 2/GaH/sub 3/(P/sub 2/O/sub 7/)/sub 2/, CsGaHP/sub 3/O/sub 10/, Cs/sub 3/Ga/sub 3/P/sub 12/O/sub 36/. Their x-ray characteristics are given.

  4. Anomalous microstructural changes in III-nitrides under ion bombardment

    International Nuclear Information System (INIS)

    Kucheyev, S.O.; Williams, J.S.; Jagadish, C.

    2002-01-01

    Full text: Group-III nitrides (GaN, AlGaN, and InGaN) are currently a 'hot topic' in the physics and material research community due to very important technological applications of these materials in (opto)electronics. In the fabrication of III-nitride-based devices, ion bombardment represents a very attractive processing tool. However, ion-beam-produced lattice disorder and its undesirable consequences limit technological applications of ion implantation. Hence, studies of ion-beam-damage processes in Ill-nitrides are not only physically interesting but also technologically important. In this study, wurtzite GaN, AlGaN, and InGaN films exposed to ion bombardment under a wide range of irradiation conditions are studied by a combination of transmission electron microscopy (TEM), environmental scanning electron microscopy (ESEM), energy dispersive x-ray spectrometry (EDS), atomic force microscopy (AFM), cathodoluminescence (CL), and Rutherford backscattering/channeling (RBS/C) spectrometry. Results show that, unlike the situation for mature semiconductors such as Si and GaAs, Ill-nitrides exhibit a range of intriguing behavior involving extreme microstructural changes under ion bombardment. In this presentation, the following aspects are discussed: (i) formation of lattice defects during ion bombardment, (ii) ion-beam-induced phase transformations, (iii) ion-beam-produced stoichiometric imbalance and associated material decomposition, and (iv) an application of charging phenomena during ESEM imaging for studies of electrical isolation in GaN by MeV light ion irradiation. Emphasis is given to the (powerful) application of electron microscopy techniques for the understanding of physical processes occurring in Ill-nitrides under ion bombardment. Copyright (2002) Australian Society for Electron Microscopy Inc

  5. Nitride image intensifiers

    Science.gov (United States)

    Glesener, J. W.; Dabiran, A. M.; Estrera, J. P.

    2009-05-01

    Nitride based photocathodes for image intensifiers are of interest because of the wide span of wavelengths covered by the bandgap of the AlGaInN alloy system. The potential bandgap range for this alloy system is from 6.2 eV for AlN to 0.7 eV for InN. Coupled with microchannel plate technology, this alloy system potentially offers low noise and high gain image intensifiers over a wide wavelength range. Results from L-3 EOS work in this area are presented beginning with a brief summary of unpublished early work carried out from 1992 - 1997 on AlGaN image intensifiers. The early work wrestled with the dual issues of sealing image intensifiers along with improving the quality of the AlGaN epitaxy layer. This is followed by our current results on a GaN image intensifier sealed with a photocathode from SVTA. Imagery using 375nm LED illumination is shown. The quantum efficiency at 300nm was estimated to be 16% measured in transmission mode. This QE was achieved with a 0.15μm thick Mg doped GaN active layer.

  6. Performance of a Medipix3RX spectroscopic pixel detector with a high resistivity gallium arsenide sensor.

    Science.gov (United States)

    Hamann, Elias; Koenig, Thomas; Zuber, Marcus; Cecilia, Angelica; Tyazhev, Anton; Tolbanov, Oleg; Procz, Simon; Fauler, Alex; Baumbach, Tilo; Fiederle, Michael

    2015-03-01

    High resistivity gallium arsenide is considered a suitable sensor material for spectroscopic X-ray imaging detectors. These sensors typically have thicknesses between a few hundred μm and 1 mm to ensure a high photon detection efficiency. However, for small pixel sizes down to several tens of μm, an effect called charge sharing reduces a detector's spectroscopic performance. The recently developed Medipix3RX readout chip overcomes this limitation by implementing a charge summing circuit, which allows the reconstruction of the full energy information of a photon interaction in a single pixel. In this work, we present the characterization of the first Medipix3RX detector assembly with a 500 μm thick high resistivity, chromium compensated gallium arsenide sensor. We analyze its properties and demonstrate the functionality of the charge summing mode by means of energy response functions recorded at a synchrotron. Furthermore, the imaging properties of the detector, in terms of its modulation transfer functions and signal-to-noise ratios, are investigated. After more than one decade of attempts to establish gallium arsenide as a sensor material for photon counting detectors, our results represent a breakthrough in obtaining detector-grade material. The sensor we introduce is therefore suitable for high resolution X-ray imaging applications.

  7. Boron, phosphorus, and gallium determination in silicon crystals doped with gallium

    International Nuclear Information System (INIS)

    Shklyar, B.L.; Dankovskij, Yu.V.; Trubitsyn, Yu.V.

    1989-01-01

    When studying IR transmission spectra of silicon doped with gallium in the range of concentrations 1 x 10 14 - 5 x 10 16 cm -3 , the possibility to quantity at low (∼ 20 K) temperatures residual impurities of boron and phosphorus is ascertained. The lower determination limit of boron is 1 x 10 12 cm -3 for a sample of 10 nm thick. The level of the impurities in silicon crystals, grown by the Czochralski method and method of crucible-free zone melting, is measured. Values of boron and phosphorus concentrations prior to and after their alloying with gallium are compared

  8. Optical frequency comb generation from aluminum nitride micro-ring resonator

    OpenAIRE

    Jung, Hojoong; Xiong, Chi; Fong, King Y.; Zhang, Xufeng; Tang, Hong X.

    2013-01-01

    Aluminum nitride is an appealing nonlinear optical material for on-chip wavelength conversion. Here we report optical frequency comb generation from high quality factor aluminum nitride micro-ring resonators integrated on silicon substrates. By engineering the waveguide structure to achieve near-zero dispersion at telecommunication wavelengths and optimizing the phase matching for four-wave mixing, frequency combs are generated with a single wavelength continuous-wave pump laser. The Kerr coe...

  9. Structure and properties of the Stainless steel AISI 316 nitrided with microwave plasma

    International Nuclear Information System (INIS)

    Becerril R, F.

    1999-01-01

    In this work were presented the results obtained by nitridation on stainless steel AISI 316 using a plasma generated through a microwave discharge with an external magnetic field using several moistures hydrogen / nitrogen to form a plasma. The purpose of nitridation was to increase the surface hardness of stainless steel through a phase formation knew as γN which has been reported that produces such effect without affect the corrosion resistance proper of this material. (Author)

  10. Synthesis and characterization of group V metal carbide and nitride catalysts

    Science.gov (United States)

    Kwon, Heock-Hoi

    1998-11-01

    Group V transition metal carbides and nitrides were prepared via the temperature programmed reaction (TPR) of corresponding oxides with NHsb3 or a CHsb4/Hsb2 mixture. Except for the tantalum compounds, phase-pure carbides and nitrides were prepared. The vanadium carbides and nitrides were the most active and selective catalysts. Therefore the principal focus of the research was the preparation, characterization, and evaluation of high surface area vanadium nitride catalysts. A series of vanadium nitrides with surface areas up to 60 msp2/g was prepared. Thermal gravimetric analysis coupled with x-ray diffraction and scanning electron microscopy indicated that the solid-state reaction proceeded by the sequential reduction of Vsb2Osb5 to VOsb{0.9} and concluded with the topotactic substitution of nitrogen for oxygen in VOsb{0.9}. The transformation of Vsb2Osb5 to VN was pseudomorphic. An experimental design was executed to determine effects of the heating rates and space velocities on the VN microstructures. The heating rates had minor effects on the surface areas and pore size distributions; however, increasing the space velocity significantly increased the surface area. The materials were mostly mesoporous. Oxygen chemisorption on the vanadium nitrides scaled linearly with the surface area. The corresponding O/Vsbsurface ratio was ≈0.6. The vanadium nitrides were active for butane activation and pyridine hydrodenitrogenation. During butane activation, their selectivities towards dehydrogenation products were as high as 98%. The major product in pyridine hydrodenitrogenation was pentane. The reaction rates increased almost linearly with the surface area suggesting that these reactions were structure insensitive. The vanadium nitrides were not active for crotonaldehyde hydrogenation; however, they catalyzed an interesting ring formation reaction that produced methylbenzaldehyde and xylene from crotonaldehyde. A new method was demonstrated for the production of very

  11. Electric Field Stiffening Effect in c-Oriented Aluminum Nitride Piezoelectric Thin Films.

    Science.gov (United States)

    Chen, Cong; Shang, Zhengguo; Gong, Jia; Zhang, Feng; Zhou, Hong; Tang, Bin; Xu, Yi; Zhang, Chi; Yang, Ya; Mu, Xiaojing

    2018-01-17

    Aluminum nitride offers unique material advantages for the realization of ultrahigh-frequency acoustic devices attributed to its high ratio of stiffness to density, compatibility with harsh environments, and superior thermal properties. Although, to date, aluminum nitride thin films have been widely investigated regarding their electrical and mechanical characteristics under alternating small signal excitation, their ultrathin nature under large bias may also provide novel and useful properties. Here, we present a comprehensive investigation of electric field stiffening effect in c-oriented aluminum nitride piezoelectric thin films. By analyzing resonance characteristics in a 2.5 GHz aluminum nitride-based film bulk acoustic resonator, we demonstrate an up to 10% linear variation in the equivalent stiffness of aluminum nitride piezoelectric thin films when an electric field was applied from -150 to 150 MV/m along the c-axis. Moreover, for the first time, an atomic interaction mechanism is proposed to reveal the nature of electric field stiffening effect, suggesting that the nonlinear variation of the interatomic force induced by electric field modulation is the intrinsic reason for this phenomenon in aluminum nitride piezoelectric thin films. Our work provides vital experimental data and effective theoretical foundation for electric field stiffening effect in aluminum nitride piezoelectric thin films, indicating the huge potential in tunable ultrahigh-frequency microwave devices.

  12. Low-temperature direct synthesis of mesoporous vanadium nitrides for electrochemical capacitors

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hae-Min [Institute of NT-IT Fusion Technology, Ajou University, 206 Worldcup-ro, Yeongtong-gu, Suwon 16499 (Korea, Republic of); Jeong, Gyoung Hwa [Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), Banyeon 100, Ulsan 44919 (Korea, Republic of); Kim, Sang-Wook [Department of Molecular Science and Technology, Ajou University, 206 Worldcup-ro, Yeongtong-gu, Suwon 16499 (Korea, Republic of); Kim, Chang-Koo, E-mail: changkoo@ajou.ac.kr [Department of Chemical Engineering and Department of Energy Systems Research, Ajou University, 206 Worldcup-ro, Yeongtong-gu, Suwon 16499 (Korea, Republic of)

    2017-04-01

    Highlights: • Vanadium nitrides were directly synthesized by a one-step chemical precipitation method. • This method was carried out at a low temperature of 70 °C. • Vanadium nitrides had a specific capacitance of 598 F/g. • The equivalent series resistance of the vanadium nitride electrode was 1.42 Ω after 5000 cycles. - Abstract: Mesoporous vanadium nitrides are directly synthesized by a one-step chemical precipitation method at a low temperature (70 °C). Structural and morphological analyses reveal that vanadium nitride consist of long and slender nanowhiskers, and mesopores with diameters of 2–5 nm. Compositional analysis confirms the presence of vanadium in the VN structure, along with oxidized vanadium. The cyclic voltammetry and charge-discharge tests indicate that the obtained material stores charges via a combination of electric double-layer capacitance and pseudocapacitance mechanisms. The vanadium nitride electrode exhibits a specific capacitance of 598 F/g at a current density of 4 A/g. After 5000 charge-discharge cycles, the electrode has an equivalent series resistance of 1.42 Ω and retains 83% of its initial specific capacitance. This direct low-temperature synthesis of mesoporous vanadium nitrides is a simple and promising method to achieve high specific capacitance and low equivalent series resistance for electrochemical capacitor applications.

  13. Uranium sesqui nitride synthesis and its use as catalyst for the thermo decomposition of ammonia

    International Nuclear Information System (INIS)

    Rocha, Soraya Maria Rizzo da

    1996-01-01

    The preoccupation to have a secure destination for metallic uranium scraps and wastes and to search new non-nuclear uses for the huge amount of depleted metal uranium accumulated at the nuclear industry encouraged the study of the uranium sesqui nitride synthesis and its use. The use of uranium sesqui nitride as a catalyst for the thermo decomposition of ammonia for the hydrogen production has enormous significance. One of the most important nuclear cycle step is the reduction of the higher uranium oxides for the production of uranium dioxide and its conversion to uranium tetrafluoride. The reduction of the UO 3 and U 3 O 8 oxides is accomplished by the gas-solid reaction with elementary hydrogen. For economical purposes and for the safety concern the nuclear industry prefers to manufacture the hydrogen gas at the local and at the moment of use, exploring the catalytic decomposition of ammonia vapor. Using metallic uranium scraps as the raw material the obtention of its nitride was achieved by the reaction with ammonia. The results of the chemical and physical characterization of the prepared uranium sesqui nitride and its behavior as a catalyst for the cracking of ammonia are commented. A lower ammonia cracking temperature (550 deg C) using the uranium sesqui nitride compared with recommended industrial catalysts iron nitride (650 deg C) and manganese nitride (700 deg C) sounds reliable and economically advantageous. (author)

  14. Metallurgical response of an AISI 4140 steel to different plasma nitriding gas mixtures

    Directory of Open Access Journals (Sweden)

    Adão Felipe Oliveira Skonieski

    2013-01-01

    Full Text Available Plasma nitriding is a surface modification process that uses glow discharge to diffuse nitrogen atoms into the metallic matrix of different materials. Among the many possible parameters of the process, the gas mixture composition plays an important role, as it impacts directly the formed layer's microstructure. In this work an AISI 4140 steel was plasma nitrided under five different gas compositions. The plasma nitriding samples were characterized using optical and scanning electron microscopy, microhardness test, X-ray diffraction and GDOES. The results showed that there are significant microstructural and morphological differences on the formed layers depending on the quantity of nitrogen and methane added to the plasma nitriding atmosphere. Thicknesses of 10, 5 and 2.5 µm were obtained when the nitrogen content of the gas mixtures were varied. The possibility to obtain a compound layer formed mainly by γ'-Fe4N nitrides was also shown. For all studied plasma nitriding conditions, the presence of a compound layer was recognized as being the responsible to hinder the decarburization on the steel surface. The highest value of surface hardness - 1277HV - were measured in the sample which were nitrided with 3vol.% of CH4.

  15. Let there be light--with gallium nitride: the 2014 Nobel Prize in Physics.

    Science.gov (United States)

    Von Dollen, Paul; Pimputkar, Siddha; Speck, James S

    2014-12-15

    Significant gains in energy savings now underway can be traced to a single invention--the blue light-emitting diode. GaN-based blue LED technology not only resulted in efficient white light sources, but continues to enable a host of applications and scientific inquiries. The researchers primarily responsible for the development of the blue LED were awarded the 2014 Nobel Prize in Physics. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Growth kinetics and characterizations of gallium nitride thin films by remote PECVD

    Science.gov (United States)

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

    1993-01-01

    Thin films of GaN have been deposited at relatively low growth temperatures by remote plasma-enhanced chemical-vapor deposition (RPECVD), using a plasma excited NH3, and trimethylgallium (TMG), injected downstream from the plasma. The activation energy for GaN growth has been tentatively assigned to the dissociation of NH groups as the primary N-atom precursors in the surface reaction with adsorbed TMG, or TMG fragments. At high He flow rates, an abrupt increase in the growth rate is observed and corresponds to a change in the reaction mechanism attributed to the formation of atomic N. XRD reveals an increased tendency to ordered growth in the (0001) direction with increasing growth temperature, He flow rate, and RF plasma power. IR spectra show the fundamental lattice mode of GaN at 530 cm without evidence for vibrational modes of hydrocarbon groups.

  17. Electrochemical deposition of copper on single-crystal gallium nitride(0001) electrode: nucleation and growth mechanism

    International Nuclear Information System (INIS)

    Zhao, Yu; Deng, Feng-Xiang; Hu, Li-Feng; Liu, Yong-Qiang; Pan, Ge-Bo

    2014-01-01

    Highlights: • The nucleation and growth of Cu electrodeposition on n-GaN was explored. • The Cu deposition commenced at a large negative potential of −840 mV vs. Pt/Pt 2+ . • The deposition process was quasi-reversible and mass transfer limited. • The deposition occurred on the conduction band of n-GaN. - Abstract: The electrodeposition of Cu on n-type single-crystal GaN(0001) electrode from sulfate solution was investigated by electrochemical techniques and scanning electron microscopy. It was found that Cu deposition on GaN(0001) commenced at a large negative potential of −840 mV vs. Pt/Pt 2+ and was quasi-reversible and mass transfer limited. On the basis of Tafel plot, a low exchange current density of ∼ 2.3 × 10 −6 mA cm −2 was calculated. This was mainly due to the limited free electrons in the conduction band of GaN. In addition, the current transient measurements revealed that the deposition process followed the progressive nucleation in 0.5 M H 2 SO 4 + 5 mM CuSO 4 . The instantaneous nucleation was observed only at the large applied potential of −1.1 V

  18. Analysis of Proton Radiation Effects on Gallium Nitride High Electron Mobility Transistors

    Science.gov (United States)

    2017-03-01

    revealed diffusion of Nickel into the Gold layer [11]. This diffusion at layer boundaries was also evident at the AlGaN/GaN interface. Fast neutron...carried out at NRL. The device gatestack consists of a 30.0-nm thick Ni gate, followed by a gold overlay of 300.0-nm. The device is passivated with a...Varying Proton Energies 46 CHAPTER 5: Conclusions In this study, we have successfully created a TCAD model that utilizes Monte Carlo sim - ulated proton

  19. Properties of RF magnetron sputtered gallium nitride semiconductors doped with erbium

    Czech Academy of Sciences Publication Activity Database

    Peřina, Vratislav; Macková, Anna; Hnatowicz, Vladimír; Prajzler, V.; Machovič, V.; Matějka, P.; Schröfel, J.

    2004-01-01

    Roč. 36, č. 8 (2004), s. 952-954 ISSN 0142-2421 R&D Projects: GA ČR GA104/03/0387 Institutional research plan: CEZ:AV0Z1048901 Keywords : Er-doped GaN * luminescence * magnetron sputtering Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 1.209, year: 2004

  20. Channeling Study of Lattice Disorder and Gold Implants in Gallium Nitride

    International Nuclear Information System (INIS)

    Jiang, Weilin; Weber, William J.; Thevuthasan, Suntharampillai; Shutthanandan, Vaithiyalingam

    2001-01-01

    Irradiation experiments have been performed 60? off normal for a GaN single crystal film at 300 K using 3 MeV Au3+ ions over fluences ranging from 0.88 to 86.2 ions/nm2. The accumulation of disorder on both the Ga and N sublattices has been simultaneously investigated using 3.8 MeV He+ non-Rutherford backscattering spectrometry along the and axial channeling directions. The accumulated disorder at the damage peak increases with dose below 10 dpa, and saturates at a relative level of ∼0.7 between 10 and 60 dpa. Complete amorphization starts at the surface and grows into the damage peak regime. A higher rate of disordering on the N sublattice is observed at low damage levels, which suggests a lower threshold displacement energy on the N sublattice in GaN. Isochronal annealing (20 min) at temperatures up to 1000 K has been used to follow the thermal response of the Ga disorder and Au implants. Some disorder recovery occurs at the intermediate dose s. A fraction of Au occupancy on the Ga lattice site is observed in the as-implanted GaN, and the substitutional fraction of the implanted Au increases with increasing temperature