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Sample records for gallium nitride nanowires

  1. Selective growth of gallium nitride nanowires by femtosecond laser patterning

    Energy Technology Data Exchange (ETDEWEB)

    Ng, D.K.T. [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore); Data Storage Institute, Agency for Science, Technology and Research, DSI Building, 5 Engineering Drive 1, Singapore 117608 (Singapore); Hong, M.H. [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore); Data Storage Institute, Agency for Science, Technology and Research, DSI Building, 5 Engineering Drive 1, Singapore 117608 (Singapore)], E-mail: HONG_Minghui@dsi.a-star.edu.sg; Tan, L.S. [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore); Zhou, Y. [Data Storage Institute, Agency for Science, Technology and Research, DSI Building, 5 Engineering Drive 1, Singapore 117608 (Singapore); Department of Mechanical Engineering, National University of Singapore, 2 Engineering Drive 3, Singapore 117576 (Singapore); Chen, G.X. [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore)

    2008-01-31

    We report on gallium nitride (GaN) nanowires grown using pulsed laser ablation, adopting the vapor-liquid-solid (VLS) growth mechanism. The GaN nanowires are obtained based on the principle that a catalyst is required to initiate the nanowires growth. Locations of the GaN nanowires are patterned using femtosecond laser and focused ion beam. Scanning electron microscopy (SEM) is used to characterize the nanowires. This patterning of GaN nanowires will enable selective growth of nanowires and bottom-up assembly of integrated electronic and photonic devices.

  2. Selective growth of gallium nitride nanowires by femtosecond laser patterning

    International Nuclear Information System (INIS)

    Ng, D.K.T.; Hong, M.H.; Tan, L.S.; Zhou, Y.; Chen, G.X.

    2008-01-01

    We report on gallium nitride (GaN) nanowires grown using pulsed laser ablation, adopting the vapor-liquid-solid (VLS) growth mechanism. The GaN nanowires are obtained based on the principle that a catalyst is required to initiate the nanowires growth. Locations of the GaN nanowires are patterned using femtosecond laser and focused ion beam. Scanning electron microscopy (SEM) is used to characterize the nanowires. This patterning of GaN nanowires will enable selective growth of nanowires and bottom-up assembly of integrated electronic and photonic devices

  3. As-Grown Gallium Nitride Nanowire Electromechanical Resonators

    Science.gov (United States)

    Montague, Joshua R.

    Technological development in recent years has led to a ubiquity of micro- and nano-scale electromechanical devices. Sensors for monitoring temperature, pressure, mass, etc., are now found in nearly all electronic devices at both the industrial and consumer levels. As has been true for integrated circuit electronics, these electromechanical devices have continued to be scaled down in size. For many nanometer-scale structures with large surface-to-volume ratio, dissipation (energy loss) becomes prohibitively large causing a decreasing sensitivity with decreasing sensor size. In this work, gallium nitride (GaN) nanowires are investigated as singly-clamped (cantilever) mechanical resonators with typical mechanical quality factors, Q (equal to the ratio of resonance frequency to peak full-width-at-half-maximum-power) and resonance frequencies, respectively, at or above 30,000, and near 1 MHz. These Q values---in vacuum at room temperature---indicate very low levels of dissipation; they are essentially the same as those for bulk quartz crystal resonators that form the basis of simple clocks and mass sensors. The GaN nanowires have lengths and diameters, respectively, of approximately 15 micrometers and hundreds of nanometers. As-grown GaN nanowire Q values are larger than other similarly-sized, bottom-up, cantilever resonators and this property makes them very attractive for use as resonant sensors. We demonstrate the capability of detecting sub-monolayer levels of atomic layer deposited (ALD) films, and the robust nature of the GaN nanowires structure that allows for their 'reuse' after removal of such layers. In addition to electron microscope-based measurement techniques, we demonstrate the successful capacitive detection of a single nanowire using microwave homodyne reflectometry. This technique is then extended to allow for simultaneous measurements of large ensembles of GaN nanowires on a single sample, providing statistical information about the distribution of

  4. Performance analysis and simulation of vertical gallium nitride nanowire transistors

    Science.gov (United States)

    Witzigmann, Bernd; Yu, Feng; Frank, Kristian; Strempel, Klaas; Fatahilah, Muhammad Fahlesa; Schumacher, Hans Werner; Wasisto, Hutomo Suryo; Römer, Friedhard; Waag, Andreas

    2018-06-01

    Gallium nitride (GaN) nanowire transistors are analyzed using hydrodynamic simulation. Both p-body and n-body devices are compared in terms of threshold voltage, saturation behavior and transconductance. The calculations are calibrated using experimental data. The threshold voltage can be tuned from enhancement to depletion mode with wire doping. Surface states cause a shift of threshold voltage and saturation current. The saturation current depends on the gate design, with a composite gate acting as field plate in the p-body device. He joined Bell Laboratories, Murray Hill, NJ, as a Technical Staff Member. In October 2001, he joined the Optical Access and Transport Division, Agere Systems, Alhambra, CA. In 2004, he was appointed an Assistant Professor at ETH Zurich,. Since 2008, at the University of Kassel, Kassel, Germany, and he has been a Professor the Head of the Computational Electronics and Photonics Group, and co-director of CINSaT since 2010. His research interests include computational optoelectronics, process and device design of semiconductor photonic devices, microwave components, and electromagnetics modeling for nanophotonics. Dr. Witzigmann is a senior member of the SPIE and IEEE.

  5. 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.

  6. Fabrication and PL of Al-doped gallium nitride nanowires

    International Nuclear Information System (INIS)

    Zhou Shaomin

    2006-01-01

    Mass Al-doped GaN nanowires with an average diameter of about 50 nm and lengths up to several millimeters are fabricated by a CVD approach. The as-fabricated products have a single crystal phase and grow along the direction. The growth of Al-doped GaN nanowires is suggested for quasi-vapor-solid mechanism (QVSM). In particular, for as large-scale GaN nanowires, a novel strong ultraviolet PL spectrum (from 3.3 to 3.7 eV) appears with a doping Al where the Al-doped GaN nanowires are found to be responsible for the different characteristics; the PL mechanism is explained in detail

  7. 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.

  8. 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.

  9. 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...

  10. Indium gallium nitride/gallium nitride quantum wells grown on polar and nonpolar gallium nitride substrates

    Science.gov (United States)

    Lai, Kun-Yu

    Nonpolar (m-plane or a-plane) gallium nitride (GaN) is predicted to be a potential substrate material to improve luminous efficiencies of nitride-based quantum wells (QWs). Numerical calculations indicated that the spontaneous emission rate in a single In0.15Ga0.85N/GaN QW could be improved by ˜2.2 times if the polarization-induced internal field was avoided by epitaxial deposition on nonpolar substrates. A challenge for nonpolar GaN is the limited size (less than 10x10 mm2) of substrates, which was addressed by expansion during the regrowth by Hydride Vapor Phase Epitaxy (HVPE). Subsurface damage in GaN substrates were reduced by annealing with NH3 and N2 at 950°C for 60 minutes. It was additionally found that the variation of m-plane QWs' emission properties was significantly increased when the substrate miscut toward a-axis was increased from 0° to 0.1°. InGaN/GaN QWs were grown by Metalorganic Chemical Vapor Deposition (MOCVD) on c-plane and m-plane GaN substrates. The QWs were studied by cathodoluminescence spectroscopy with different incident electron beam probe currents (0.1 nA ˜ 1000 nA). Lower emission intensities and longer peak wavelengths from c-plane QWs were attributed to the Quantum-confined Stark Effect (QCSE). The emission intensity ratios of m-plane QWs to c-plane QWs decreased from 3.04 at 1 nA to 1.53 at 1000 nA. This was identified as the stronger screening effects of QCSE at higher current densities in c-plane QWs. To further investigate these effects in a fabricated structure, biased photoluminescence measurements were performed on m-plane InGaN/GaN QWs. The purpose was to detect the possible internal fields induced by the dot-like structure in the InGaN layer through the response of these internal fields under externally applied fields. No energy shifts of the QWs were observed, which was attributed to strong surface leakage currents.

  11. 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

  12. Gallium Nitride Crystals: Novel Supercapacitor Electrode Materials.

    Science.gov (United States)

    Wang, Shouzhi; Zhang, Lei; Sun, Changlong; Shao, Yongliang; Wu, Yongzhong; Lv, Jiaxin; Hao, Xiaopeng

    2016-05-01

    A type of single-crystal gallium nitride mesoporous membrane is fabricated and its supercapacitor properties are demonstrated for the first time. The supercapacitors exhibit high-rate capability, stable cycling life at high rates, and ultrahigh power density. This study may expand the range of crystals as high-performance electrode materials in the field of energy storage. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

    KAUST Repository

    Awan, Kashif M.; Dolgaleva, Ksenia; Mumthaz Muhammed, Mufasila; Roqan, Iman S.

    2017-01-01

    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).

  14. 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).

  15. 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.

  16. 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.

  17. Sodium Flux Growth of Bulk Gallium Nitride

    Science.gov (United States)

    Von Dollen, Paul Martin

    This dissertation focused on development of a novel apparatus and techniques for crystal growth of bulk gallium nitride (GaN) using the sodium flux method. Though several methods exist to produce bulk GaN, none have been commercialized on an industrial scale. The sodium flux method offers potentially lower cost production due to relatively mild process conditions while maintaining high crystal quality. But the current equipment and methods for sodium flux growth of bulk GaN are generally not amenable to large-scale crystal growth or in situ investigation of growth processes, which has hampered progress. A key task was to prevent sodium loss or migration from the sodium-gallium growth melt while permitting N2 gas to access the growing crystal, which was accomplished by implementing a reflux condensing stem along with a reusable sealed capsule. The reflux condensing stem also enabled direct monitoring and control of the melt temperature, which has not been previously reported for the sodium flux method. Molybdenum-based materials were identified from a corrosion study as candidates for direct containment of the corrosive sodium-gallium melt. Successful introduction of these materials allowed implementation of a crucible-free containment system, which improved process control and can potentially reduce crystal impurity levels. Using the new growth system, the (0001) Ga face (+c plane) growth rate was >50 mum/hr, which is the highest bulk GaN growth rate reported for the sodium flux method. Omega X-ray rocking curve (?-XRC) measurements indicated the presence of multiple grains, though full width at half maximum (FWHM) values for individual peaks were 1020 atoms/cm3, possibly due to reactor cleaning and handling procedures. This dissertation also introduced an in situ technique to correlate changes in N2 pressure with dissolution of nitrogen and precipitation of GaN from the sodium-gallium melt. Different stages of N2 pressure decay were identified and linked to

  18. 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.)

  19. Gallium Nitride MMICs for mm-Wave Power Operation

    NARCIS (Netherlands)

    Quay, R.; Maroldt, S.; Haupt, C.; Heijningen, M. van; Tessmann, A.

    2009-01-01

    In this paper a Gallium Nitride MMIC technology for high-power amplifiers between 27 GHz and 101 GHz based on 150 nm- and 100 nm-gate technologies is presented. The GaN HEMT MMICs are designed using coplanar waveguide transmission-line-technology on 3-inch semi-insulating SiC substrates. The

  20. Ultra-low threshold gallium nitride photonic crystal nanobeam laser

    Energy Technology Data Exchange (ETDEWEB)

    Niu, Nan, E-mail: nanniu@fas.harvard.edu; Woolf, Alexander; Wang, Danqing; Hu, Evelyn L. [School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138 (United States); Zhu, Tongtong; Oliver, Rachel A. [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom); Quan, Qimin [Rowland Institute at Harvard University, Cambridge, Massachusetts 02142 (United States)

    2015-06-08

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

  1. Ultra-low threshold gallium nitride photonic crystal nanobeam laser

    International Nuclear Information System (INIS)

    Niu, Nan; Woolf, Alexander; Wang, Danqing; Hu, Evelyn L.; Zhu, Tongtong; Oliver, Rachel A.; Quan, Qimin

    2015-01-01

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

  2. Neutron detection using boron gallium nitride semiconductor material

    Directory of Open Access Journals (Sweden)

    Katsuhiro Atsumi

    2014-03-01

    Full Text Available In this study, we developed a new neutron-detection device using a boron gallium nitride (BGaN semiconductor in which the B atom acts as a neutron converter. BGaN and gallium nitride (GaN samples were grown by metal organic vapor phase epitaxy, and their radiation detection properties were evaluated. GaN exhibited good sensitivity to α-rays but poor sensitivity to γ-rays. Moreover, we confirmed that electrons were generated in the depletion layer under neutron irradiation. This resulted in a neutron-detection signal after α-rays were generated by the capture of neutrons by the B atoms. These results prove that BGaN is useful as a neutron-detecting semiconductor material.

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

    KAUST Repository

    El Afandy, Rami

    2011-01-01

    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

  4. Superconductive silicon nanowires using gallium beam lithography.

    Energy Technology Data Exchange (ETDEWEB)

    Henry, Michael David; Jarecki, Robert Leo,

    2014-01-01

    This work was an early career LDRD investigating the idea of using a focused ion beam (FIB) to implant Ga into silicon to create embedded nanowires and/or fully suspended nanowires. The embedded Ga nanowires demonstrated electrical resistivity of 5 m-cm, conductivity down to 4 K, and acts as an Ohmic silicon contact. The suspended nanowires achieved dimensions down to 20 nm x 30 nm x 10 m with large sensitivity to pressure. These structures then performed well as Pirani gauges. Sputtered niobium was also developed in this research for use as a superconductive coating on the nanowire. Oxidation characteristics of Nb were detailed and a technique to place the Nb under tensile stress resulted in the Nb resisting bulk atmospheric oxidation for up to years.

  5. 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.

  6. Gallium nitride-based micro-opto-electro-mechanical systems

    Science.gov (United States)

    Stonas, Andreas Robert

    Gallium Nitride and its associated alloys InGaN and AlGaN have many material properties that are highly desirable for micro-electro-mechanical systems (MEMS), and more specifically micro-opto-electro-mechanical systems (MOEMS). The group III-nitrides are tough, stiff, optically transparent, direct bandgap, chemically inert, highly piezoelectric, and capable of functioning at high temperatures. There is currently no other semiconductor system that possesses all of these properties. Taken together, these attributes make the nitrides prime candidates not only for creating new versions of existing device structures, but also for creating entirely unique devices which combine these properties in novel ways. Unfortunately, their chemical resiliency also makes the group III-nitrides extraordinarily difficult to shape into devices. In particular, until this research, no undercut etch technology existed that could controllably separate a selected part of a MEMS device from its sapphire or silicon carbide substrate. This has effectively prevented GaN-based MEMS from being developed. This dissertation describes how this fabrication obstacle was overcome by a novel etching geometry (bandgap-selective backside-illuminated photoelectochemical (BS-BIPEC) etching) and its resulting morphologies. Several gallium-nitride based MEMS devices were created, actuated, and modelled, including cantilevers and membranes. We describe in particular our pursuit of one of the many novel device elements that is possible only in this material system: a transducer that uses an externally applied strain to dynamically change the optical transition energy of a quantum well. While the device objective of a dynamically tunable quantum well was not achieved, we have demonstrated sufficient progress to believe that such a device will be possible soon. We have observed a shift (5.5meV) of quantum well transition energies in released structures, and we have created structures that can apply large biaxial

  7. 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

  8. 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.

  9. Micro and nano-structured green gallium indium nitride/gallium nitride light-emitting diodes

    Science.gov (United States)

    Stark, Christoph J. M.

    Light-emitting diodes (LEDs) are commonly designed and studied based on bulk material properties. In this thesis different approaches based on patterns in the nano and micrometer length scale range are used to tackle low efficiency in the green spectral region, which is known as “green gap”. Since light generation and extraction are governed by microscopic processes, it is instructive to study LEDs with lateral mesa sizes scaled to the nanometer range. Besides the well-known case of the quantum size effect along the growth direction, a continuous lateral scaling could reveal the mechanisms behind the purported absence of a green gap in nanowire LEDs and the role of their extraction enhancement. Furthermore the possibility to modulate strain and piezoelectric polarization by post growth patterning is of practical interest, because the internal electric fields in conventional wurtzite GaN LEDs cause performance problems. A possible alternative is cubic phase GaN, which is free of built-in polarization fields. LEDs on cubic GaN could show the link between strong polarization fields and efficiency roll-off at high current densities, also known as droop. An additional problem for all nitride-based LEDs is efficient light extraction. For a planar GaN LED only roughly 8% of the generated light can be extracted. Novel lightextraction structures with extraction-favoring geometry can yield significant increase in light output power. To investigate the effect of scaling the mesa dimension, micro and nano-sized LED arrays of variable structure size were fabricated. The nano-LEDs were patterned by electron beam lithography and dry etching. They contained up to 100 parallel nano-stripe LEDs connected to one common contact area. The mesa width was varied over 1 μm, 200 nm, and 50 nm. These LEDs were characterized electrically and optically, and the peak emission wavelength was found to depend on the lateral structure size. An electroluminescence (EL) wavelength shift of 3 nm

  10. LETTER TO THE EDITOR: Fabrication and structure of an opal-gallium nitride nanocomposite

    Science.gov (United States)

    Davydov, V. Yu; Dunin-Borkovski, R. E.; Golubev, V. G.; Hutchison, J. L.; Kartenko, N. F.; Kurdyukov, D. A.; Pevtsov, A. B.; Sharenkova, N. V.; Sloan, J.; Sorokin, L. M.

    2001-02-01

    A three-dimensional gallium nitride lattice has been synthesized within the void sublattice of an artificial opal. The composite structure has been characterized using X-ray diffraction, Raman spectroscopy and transmission electron microscopy.

  11. 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...

  12. Localized surface phonon polariton resonances in polar gallium nitride

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Kaijun, E-mail: kfeng@nd.edu; Islam, S. M.; Verma, Jai; Hoffman, Anthony J. [Department of Electrical Engineering, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Streyer, William; Wasserman, Daniel [Department of Electrical and Computer Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois 61801 (United States); Jena, Debdeep [Department of Electrical Engineering, University of Notre Dame, Notre Dame, Indiana 46556 (United States); School of Electrical and Computer Engineering, Cornell University, Ithaca, New York 14850 (United States)

    2015-08-24

    We demonstrate the excitation of localized surface phonon polaritons in an array of sub-diffraction pucks fabricated in an epitaxial layer of gallium nitride (GaN) on a silicon carbide (SiC) substrate. The array is characterized via polarization- and angle-dependent reflection spectroscopy in the mid-infrared, and coupling to several localized modes is observed in the GaN Reststrahlen band (13.4–18.0 μm). The same structure is simulated using finite element methods and the charge density of the modes are studied; transverse dipole modes are identified for the transverse electric and magnetic polarizations and a quadrupole mode is identified for the transverse magnetic polarization. The measured mid-infrared spectrum agrees well with numerically simulated spectra. This work could enable optoelectronic structures and devices that support surface modes at mid- and far-infrared wavelengths.

  13. Development of microwave amplifier based on gallium nitride semiconductor structures

    International Nuclear Information System (INIS)

    Pavlov, D.Yi.; Prokopenko, O.V.; Tsvyirko, Yu.A.; Pavlov, Yi.L.

    2014-01-01

    Microwave properties of microwave amplifier based on gallium nitride (GN) semiconductor structures has been calculated numerically. We proposed the method of numerical calculation of device. This method is accurately sets the value of its characteristics depending on the elements that are used in design of amplifier. It is shown that the device based on GN HEMT-transistors could have amplification factor about 50 dB, while its sizes are 27x18x5.5 mm 3 . Also was provided the absolute stability an amplifier in the whole operating frequency range. It is quite important when using this type of amplifiers in different conditions of exploitation and various fields of use the radioelectronic equipment

  14. A high open-circuit voltage gallium nitride betavoltaic microbattery

    International Nuclear Information System (INIS)

    Cheng, Zaijun; Chen, Xuyuan; San, Haisheng; Feng, Zhihong; Liu, Bo

    2012-01-01

    A high open-circuit voltage betavoltaic microbattery based on a gallium nitride (GaN) p–i–n homojunction is demonstrated. As a beta-absorbing layer, the low electron concentration of the n-type GaN layer is achieved by the process of Fe compensation doping. Under the irradiation of a planar solid 63 Ni source with activity of 0.5 mCi, the open-circuit voltage of the fabricated microbattery with 2 × 2 mm 2 area reaches as much as 1.64 V, which is the record value reported for betavoltaic batteries with 63 Ni source, the short-circuit current was measured as 568 pA and the conversion effective of 0.98% was obtained. The experimental results suggest that GaN is a high-potential candidate for developing the betavoltaic microbattery. (paper)

  15. Fabrication and Characterization of Vertical Gallium Nitride Power Schottky Diodes on Bulk GaN Substrates FY2016

    Science.gov (United States)

    2016-12-01

    ARL-TR-7913 ● DEC 2016 US Army Research Laboratory Fabrication and Characterization of Vertical Gallium Nitride Power Schottky...TR-7913 ● DEC 2016 US Army Research Laboratory Fabrication and Characterization of Vertical Gallium Nitride Power Schottky Diodes on Bulk...Fabrication and Characterization of Vertical Gallium Nitride Power Schottky Diodes on Bulk GaN Substrates FY2016 5a. CONTRACT NUMBER 5b. GRANT NUMBER

  16. 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

  17. 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.

  18. Proton irradiation effects on gallium nitride-based devices

    Science.gov (United States)

    Karmarkar, Aditya P.

    Proton radiation effects on state-of-the-art gallium nitride-based devices were studied using Schottky diodes and high electron-mobility transistors. The device degradation was studied over a wide range of proton fluences. This study allowed for a correlation between proton irradiation effects between different types of devices and enhanced the understanding of the mechanisms responsible for radiation damage in GaN-based devices. Proton irradiation causes reduced carrier concentration and increased series resistance and ideality factor in Schottky diodes. 1.0-MeV protons cause greater degradation than 1.8-MeV protons because of their higher non-ionizing energy loss. The displacement damage in Schottky diodes recovers during annealing. High electron-mobility transistors exhibit extremely high radiation tolerance, continuing to perform up to a fluence of ˜1014 cm-2 of 1.8-MeV protons. Proton irradiation creates defect complexes in the thin-film structure. Decreased sheet carrier mobility due to increased carrier scattering and decreased sheet carrier density due to carrier removal by the defect centers are the primary damage mechanisms. Interface disorder at either the Schottky or the Ohmic contact plays a relatively unimportant part in overall device degradation in both Schottky diodes and high electron-mobility transistors.

  19. Growth of Gold-assisted Gallium Arsenide Nanowires on Silicon Substrates via Molecular Beam Epitaxy

    Directory of Open Access Journals (Sweden)

    Ramon M. delos Santos

    2008-06-01

    Full Text Available Gallium arsenide nanowires were grown on silicon (100 substrates by what is called the vapor-liquid-solid (VLS growth mechanism using a molecular beam epitaxy (MBE system. Good quality nanowires with surface density of approximately 108 nanowires per square centimeter were produced by utilizing gold nanoparticles, with density of 1011 nanoparticles per square centimeter, as catalysts for nanowire growth. X-ray diffraction measurements, scanning electron microscopy, transmission electron microscopy and Raman spectroscopy revealed that the nanowires are epitaxially grown on the silicon substrates, are oriented along the [111] direction and have cubic zincblende structure.

  20. 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.

  1. 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.

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

    International Nuclear Information System (INIS)

    Seleznev, B. I.; Moskalev, G. Ya.; Fedorov, D. G.

    2016-01-01

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

  3. 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.

  4. Optical Properties of Strained Wurtzite Gallium Phosphide Nanowires

    KAUST Repository

    Greil, J.

    2016-06-08

    Wurtzite gallium phosphide (WZ GaP) has been predicted to exhibit a direct bandgap in the green spectral range. Optical transitions, however, are only weakly allowed by the symmetry of the bands. While efficient luminescence has been experimentally shown, the nature of the transitions is not yet clear. Here we apply tensile strain up to 6% and investigate the evolution of the photoluminescence (PL) spectrum of WZ GaP nanowires (NWs). The pressure and polarization dependence of the emission together with a theoretical analysis of strain effects is employed to establish the nature and symmetry of the transitions. We identify the emission lines to be related to localized states with significant admixture of Γ7c symmetry and not exclusively related to the Γ8c conduction band minimum (CBM). The results emphasize the importance of strongly bound state-related emission in the pseudodirect semiconductor WZ GaP and contribute significantly to the understanding of the optoelectronic properties of this novel material.

  5. Indium Gallium Nitride Multijunction Solar Cell Simulation Using Silvaco Atlas

    Science.gov (United States)

    2007-06-01

    models is of great interest in space applications. By increasing the efficiency of photovoltaics, the number of solar panels is decreased. Therefore...obtained in single-junction solar cells by using Gallium Arsenide. Monocrystalline Gallium Arsenide has a maximum efficiency of approximately 25.1% [10

  6. Ingestion of gallium phosphide nanowires has no adverse effect on Drosophila tissue function

    International Nuclear Information System (INIS)

    Adolfsson, Karl; Hammarin, Greger; Prinz, Christelle N; Schneider, Martina; Häcker, Udo

    2013-01-01

    Engineered nanoparticles have been under increasing scrutiny in recent years. High aspect ratio nanoparticles such as carbon nanotubes and nanowires have raised safety concerns due to their geometrical similarity to asbestos fibers. III–V epitaxial semiconductor nanowires are expected to be utilized in devices such as LEDs and solar cells and will thus be available to the public. In addition, clean-room staff fabricating and characterizing the nanowires are at risk of exposure, emphasizing the importance of investigating their possible toxicity. Here we investigated the effects of gallium phosphide nanowires on the fruit fly Drosophila melanogaster. Drosophila larvae and/or adults were exposed to gallium phosphide nanowires by ingestion with food. The toxicity and tissue interaction of the nanowires was evaluated by investigating tissue distribution, activation of immune response, genome-wide gene expression, life span, fecundity and somatic mutation rates. Our results show that gallium phosphide nanowires applied through the diet are not taken up into Drosophila tissues, do not elicit a measurable immune response or changes in genome-wide gene expression and do not significantly affect life span or somatic mutation rate. (paper)

  7. GaN Nanowires Synthesized by Electroless Etching Method

    KAUST Repository

    Najar, Adel; Anjum, Dalaver H.; Ng, Tien Khee; Ooi, Boon S.; Ben Slimane, Ahmed

    2012-01-01

    Ultra-long Gallium Nitride Nanowires is synthesized via metal-electroless etching method. The morphologies and optical properties of GaN NWs show a single crystal GaN with hexagonal Wurtzite structure and high luminescence properties.

  8. 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

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

    KAUST Repository

    Awan, Kashif M.; Dolgaleva, Ksenia; Mumthaz Muhammed, Mufasila; Roqan, Iman S.

    2016-01-01

    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.

  10. 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.

  11. Characterization of silver-gallium nanowires for force and mass sensing applications

    International Nuclear Information System (INIS)

    Biedermann, Laura B; Reifenberger, Ronald G; Tung, Ryan C; Raman, Arvind; Yazdanpanah, Mehdi M; Cohn, Robert W

    2010-01-01

    We investigate the mechanical properties of cantilevered silver-gallium (Ag 2 Ga) nanowires using laser Doppler vibrometry. From measurements of the resonant frequencies and associated operating deflection shapes, we demonstrate that these Ag 2 Ga nanowires behave as ideal Euler-Bernoulli beams. Furthermore, radial asymmetries in these nanowires are detected through high resolution measurements of the vibration spectra. These crystalline nanowires possess many ideal characteristics for nanoscale force and mass sensing, including small spring constants (as low as 10 -4 N m -1 ), high frequency bandwidth with resonance frequencies in the 0.02-10 MHz range, small suspended mass (picograms), and relatively high Q-factors (∼2-50) under ambient conditions. We evaluate the utility of Ag 2 Ga nanowires for nanocantilever applications, including ultrasmall mass and high frequency bandwidth piconewton force detection.

  12. 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.

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

    Science.gov (United States)

    2015-09-01

    ABBREVIATIONS 2DEG two-dimensional electron gas AlGaN aluminum gallium nitride AlOx aluminum oxide CCD charged coupled device CTE coefficient of...frequency of FETs. Such a device may also be known as a heterojunction field-effect transistor (HFET), modulation-doped field-effect transistor (MODFET...electrons. This charge attracts electrons to the interface, forming the 2DEG channel. The HEMT includes a heterojunction of two semiconducting

  14. Impurity decoration of native vacancies in Ga and N sublattices of gallium nitride

    OpenAIRE

    Hautakangas, Sami

    2005-01-01

    The effects of impurity atoms as well as various growth methods to the formation of vacancy type defects in gallium nitride (GaN) have been studied by positron annihilation spectroscopy. It is shown that vacancy defects are formed in Ga or N sublattices depending on the doping of the material. Vacancies are decorated with impurity atoms leading to the compensation of the free carriers of the samples. In addition, the vacancy clusters are found to be present in significant concentrations in n-...

  15. 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

  16. 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.

  17. Ab initio design of nanostructures for solar energy conversion: a case study on silicon nitride nanowire.

    Science.gov (United States)

    Pan, Hui

    2014-01-01

    Design of novel materials for efficient solar energy conversion is critical to the development of green energy technology. In this work, we present a first-principles study on the design of nanostructures for solar energy harvesting on the basis of the density functional theory. We show that the indirect band structure of bulk silicon nitride is transferred to direct bandgap in nanowire. We find that intermediate bands can be created by doping, leading to enhancement of sunlight absorption. We further show that codoping not only reduces the bandgap and introduces intermediate bands but also enhances the solubility of dopants in silicon nitride nanowires due to reduced formation energy of substitution. Importantly, the codoped nanowire is ferromagnetic, leading to the improvement of carrier mobility. The silicon nitride nanowires with direct bandgap, intermediate bands, and ferromagnetism may be applicable to solar energy harvesting.

  18. Nitride surface passivation of GaAs nanowires: impact on surface state density.

    Science.gov (United States)

    Alekseev, Prokhor A; Dunaevskiy, Mikhail S; Ulin, Vladimir P; Lvova, Tatiana V; Filatov, Dmitriy O; Nezhdanov, Alexey V; Mashin, Aleksander I; Berkovits, Vladimir L

    2015-01-14

    Surface nitridation by hydrazine-sulfide solution, which is known to produce surface passivation of GaAs crystals, was applied to GaAs nanowires (NWs). We studied the effect of nitridation on conductivity and microphotoluminescence (μ-PL) of individual GaAs NWs using conductive atomic force microscopy (CAFM) and confocal luminescent microscopy (CLM), respectively. Nitridation is found to produce an essential increase in the NW conductivity and the μ-PL intensity as well evidence of surface passivation. Estimations show that the nitride passivation reduces the surface state density by a factor of 6, which is of the same order as that found for GaAs/AlGaAs nanowires. The effects of the nitride passivation are also stable under atmospheric ambient conditions for six months.

  19. Optical polarization based logic functions (XOR or XNOR) with nonlinear Gallium nitride nanoslab.

    Science.gov (United States)

    Bovino, F A; Larciprete, M C; Giardina, M; Belardini, A; Centini, M; Sibilia, C; Bertolotti, M; Passaseo, A; Tasco, V

    2009-10-26

    We present a scheme of XOR/XNOR logic gate, based on non phase-matched noncollinear second harmonic generation from a medium of suitable crystalline symmetry, Gallium nitride. The polarization of the noncollinear generated beam is a function of the polarization of both pump beams, thus we experimentally investigated all possible polarization combinations, evidencing that only some of them are allowed and that the nonlinear interaction of optical signals behaves as a polarization based XOR. The experimental results show the peculiarity of the nonlinear optical response associated with noncollinear excitation, and are explained using the expression for the effective second order optical nonlinearity in noncollinear scheme.

  20. 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

  1. 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

  2. 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

  3. 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

  4. An electron beam induced current study of gallium nitride and diamond materials

    International Nuclear Information System (INIS)

    Cropper, A.D.; Moore, D.J.; Scott, C.S.; Green, R.

    1995-01-01

    The continual need for microelectronic devices that operate under severe electronic and environmental conditions (high temperature, high frequency, high power, and radiation tolerance) has sustained research in wide bandgap semiconductor materials. The properties suggest these wide-bandgap semiconductor materials have tremendous potential for military and commercial applications. High frequency bipolar transistors and field effect transistors, diodes, and short wavelength optical devices have been proposed using these materials. Although research efforts involving the study of transport properties in Gallium Nitride (GaN) and Diamond have made significant advances, much work is still needed to improve the material quality so that the electrophysical behavior of device structures can be further understood and exploited. Electron beam induced current (EBIC) measurements can provide a method of understanding the transport properties in Gallium Nitride (GaN) and Diamond. This technique basically consists of measuring the current or voltage transient response to the drift and diffusion of carriers created by a short-duration pulse of radiation. This method differs from other experimental techniques because it is based on a fast transient electron beam probe created from a high speed, laser pulsed photoemission system

  5. High-fluence hyperthermal ion irradiation of gallium nitride surfaces at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Finzel, A.; Gerlach, J.W., E-mail: juergen.gerlach@iom-leipzig.de; Lorbeer, J.; Frost, F.; Rauschenbach, B.

    2014-10-30

    Highlights: • Irradiation of gallium nitride films with hyperthermal nitrogen ions. • Surface roughening at elevated sample temperatures was observed. • No thermal decomposition of gallium nitride films during irradiation. • Asymmetric surface diffusion processes cause local roughening. - Abstract: Wurtzitic GaN films deposited on 6H-SiC(0001) substrates by ion-beam assisted molecular-beam epitaxy were irradiated with hyperthermal nitrogen ions with different fluences at different substrate temperatures. In situ observations with reflection high energy electron diffraction showed that during the irradiation process the surface structure of the GaN films changed from two dimensional to three dimensional at elevated temperatures, but not at room temperature. Atomic force microscopy revealed an enhancement of nanometric holes and canyons upon the ion irradiation at higher temperatures. The roughness of the irradiated and heated GaN films was clearly increased by the ion irradiation in accordance with x-ray reflectivity measurements. A sole thermal decomposition of the films at the chosen temperatures could be excluded. The results are discussed taking into account temperature dependent sputtering and surface uphill adatom diffusion as a function of temperature.

  6. Synthesis of boron nitride nanotubes with SiC nanowire as template

    International Nuclear Information System (INIS)

    Zhong, B.; Song, L.; Huang, X.X.; Wen, G.W.; Xia, L.

    2011-01-01

    Highlights: → Boron nitride nanotubes (BNNTs) have been fabricated using SiC nanowires as template. → SiC nanowires could be effectively etched out by the vapors decomposed from ammonia borane, leading to the formation of BNNTs. → A template self-sacrificing mechanism is responsible for the formation of BNNTs. -- Abstract: A novel template method for the preparation of boron nitride nanotubes (BNNTs) using SiC nanowire as template and ammonia borane as precursor is reported. We find out that the SiC nanowires could be effectively etched out by the vapors decomposed from ammonia borane, leading to the formation of BNNTs. The as-prepared products are well characterized by means of complementary analytical techniques. A possible formation mechanism is disclosed. The method developed here paves the way for large scale production of BNNTs.

  7. Failure mechanisms and electromechanical coupling in semiconducting nanowires

    Directory of Open Access Journals (Sweden)

    Peng B.

    2010-06-01

    Full Text Available One dimensional nanostructures, like nanowires and nanotubes, are increasingly being researched for the development of next generation devices like logic gates, transistors, and solar cells. In particular, semiconducting nanowires with a nonsymmetric wurtzitic crystal structure, such as zinc oxide (ZnO and gallium nitride (GaN, have drawn immense research interests due to their electromechanical coupling. The designing of the future nanowire-based devices requires component-level characterization of individual nanowires. In this paper, we present a unique experimental set-up to characterize the mechanical and electromechanical behaviour of individual nanowires. Using this set-up and complementary atomistic simulations, mechanical properties of ZnO nanowires and electromechanical properties of GaN nanowires were investigated. In ZnO nanowires, elastic modulus was found to depend on nanowire diameter decreasing from 190 GPa to 140 GPa as the wire diameter increased from 5 nm to 80 nm. Inconsistent failure mechanisms were observed in ZnO nanowires. Experiments revealed a brittle fracture, whereas simulations using a pairwise potential predicted a phase transformation prior to failure. This inconsistency is addressed in detail from an experimental as well as computational perspective. Lastly, in addition to mechanical properties, preliminary results on the electromechanical properties of gallium nitride nanowires are also reported. Initial investigations reveal that the piezoresistive and piezoelectric behaviour of nanowires is different from bulk gallium nitride.

  8. Urea route to coat inorganic nanowires, carbon fibers and nanotubes by boron nitride

    International Nuclear Information System (INIS)

    Gomathi, A.; Ramya Harika, M.; Rao, C.N.R.

    2008-01-01

    A simple route involving urea as the nitrogen source has been employed to carry out boron nitride coating on carbon fibers, multi-walled carbon nanotubes and inorganic nanowires. The process involves heating the carbon fibers and nanotubes or inorganic nanowires in a mixture of H 3 BO 3 and urea, followed by a heat treatment at 1000 deg. C in a N 2 atmosphere. We have been able to characterize the BN coating by transmission electron microscopy as well as X-ray photoelectron spectroscopy. The urea decomposition route affords a simple method to coat boron nitride on one-dimensional nanostructures

  9. Amber light-emitting diode comprising a group III-nitride nanowire active region

    Science.gov (United States)

    Wang, George T.; Li, Qiming; Wierer, Jr., Jonathan J.; Koleske, Daniel

    2014-07-22

    A temperature stable (color and efficiency) III-nitride based amber (585 nm) light-emitting diode is based on a novel hybrid nanowire-planar structure. The arrays of GaN nanowires enable radial InGaN/GaN quantum well LED structures with high indium content and high material quality. The high efficiency and temperature stable direct yellow and red phosphor-free emitters enable high efficiency white LEDs based on the RGYB color-mixing approach.

  10. Metalorganic chemical vapor deposition of gallium nitride on sacrificial substrates

    Science.gov (United States)

    Fenwick, William Edward

    GaN-based light emitting diodes (LEDs) face several challenges if the technology is to continue to make a significant impact in general illumination, and on technology that has become known as solid state lighting (SSL). Two of the most pressing challenges for the continued penetration of SSL into traditional lighting applications are efficacy and total lumens from the device, and their related cost. The development of alternative substrate technologies is a promising avenue toward addressing both of these challenges, as both GaN-based device technology and the associated metalorganic chemical vapor deposition (MOCVD) technology are already relatively mature technologies with a well-understood cost base. Zinc oxide (ZnO) and silicon (Si) are among the most promising alternative substrates for GaN epitaxy. These substrates offer the ability to access both higher efficacy and lumen devices (ZnO) at a much reduced cost. This work focuses on the development of MOCVD growth processes to yield high quality GaN-based materials and devices on both ZnO and Si. ZnO is a promising substrate for growth of low defect-density GaN because of its similar lattice constant and thermal expansion coefficient. The major hurdles for GaN growth on ZnO are the instability of the substrate in a hydrogen atmosphere, which is typical of nitride growth conditions, and the inter-diffusion of zinc and oxygen from the substrate into the GaN-based epitaxial layer. A process was developed for the MOCVD growth of GaN and InxGa 1-xN on ZnO that attempted to address these issues. The structural and optical properties of these films were studied using various techniques. X-ray diffraction (XRD) showed the growth of wurtzite GaN on ZnO, and room-temperature photoluminescence (RT-PL) showed near band-edge luminescence from the GaN and InxGa1-xN layers. However, high zinc and oxygen concentrations due to interdiffusion near the ZnO substrate remained an issue; therefore, the diffusion of zinc and oxygen

  11. Spin polarized first principles study of Mn doped gallium nitride monolayer nanosheet

    Science.gov (United States)

    Sharma, Venus; Kaur, Sumandeep; Srivastava, Sunita; Kumar, Tankeshwar

    2017-05-01

    The structural, electronic and magnetic properties of gallium nitride nanosheet (GaNs) doped with Mn atoms have been studied using spin polarized density functional theory. The binding energy per atom, Energy Band gap, Fermi energy, magnetic moment, electric dipole moment have been found. The doped nanosheet is found to be more stable than pure GaN monolayer nanosheet. Adsorption of Mn atom has been done at four different sites on GaNs which affects the fermi level position. It is found that depending on the doping site, Mn can behave both like p-type semiconductor and also as n-type semiconductor. Also, it is ascertained that Mn doped GaNs (GaNs-Mn) exhibits ferromagnetic behavior.

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

    Science.gov (United States)

    Lamhamdi, M.; Cayrel, F.; Frayssinet, E.; Bazin, A. E.; Yvon, A.; Collard, E.; Cordier, Y.; Alquier, D.

    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.

  13. 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.

  14. 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)

  15. 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.

  16. 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.

  17. Gallium nitride based thin films for photon and particle radiation dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Hofstetter, Markus

    2012-07-23

    Ionization chambers have been used since the beginning of the 20th century for measuring ionizing radiation and still represent the ''gold standard'' in dosimetry. However, since the sensitivity of the devices is proportional to the detection volume, ionization chambers are not common in numerous medical applications, such as imaging. In these fields, spatially resolved dose information is, beside film-systems, usually measured with scintillators and photo-multipliers, which is a relatively complex and expensive technique. For thus much effort has been focused on the development of novel detection systems in the last decades and especially in the last few years. Examples include germanium or silicon photoconductive detectors, MOSFETs, and PIN-diodes. Although for these systems, miniaturization for spatially resolved detection is possible, they suffer from a range of disadvantages. Characteristics such as poor measurement stability, material degradation, and/or a limited measurement range prevent routine application of these techniques in medical diagnostic devices. This work presents the development and evaluation of gallium nitride (GaN) thin films and heterostructures to validate their application in x-ray detection in the medical regime. Furthermore, the impact of particle radiation on device response was investigated. Although previous publications revealed relatively low energy absorption of GaN, it is possible to achieve very high signal amplification factors inside the material due to an appropriate sensor configuration, which, in turn, compensates the low energy absorption. Thus, gallium nitride can be used as a photo-conductor with ohmic contacts. The conductive volume of the sensor changes in the presence of external radiation, which results in an amplified measurement signal after applying a bias voltage to the device. Experiments revealed a sensitivity of the device between air kerma rates of 1 {mu}Gy/s and 20 mGy/s. In this range

  18. 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.

  19. Gallium ion implantation greatly reduces thermal conductivity and enhances electronic one of ZnO nanowires

    Directory of Open Access Journals (Sweden)

    Minggang Xia

    2014-05-01

    Full Text Available The electrical and thermal conductivities are measured for individual zinc oxide (ZnO nanowires with and without gallium ion (Ga+ implantation at room temperature. Our results show that Ga+ implantation enhances electrical conductivity by one order of magnitude from 1.01 × 103 Ω−1m−1 to 1.46 × 104 Ω−1m−1 and reduces its thermal conductivity by one order of magnitude from 12.7 Wm−1K−1 to 1.22 Wm−1K−1 for ZnO nanowires of 100 nm in diameter. The measured thermal conductivities are in good agreement with those in theoretical simulation. The increase of electrical conductivity origins in electron donor doping by Ga+ implantation and the decrease of thermal conductivity is due to the longitudinal and transverse acoustic phonons scattering by Ga+ point scattering. For pristine ZnO nanowires, the thermal conductivity decreases only two times when its diameter reduces from 100 nm to 46 nm. Therefore, Ga+-implantation may be a more effective method than diameter reduction in improving thermoelectric performance.

  20. Recent Advances on p-Type III-Nitride Nanowires by Molecular Beam Epitaxy

    Directory of Open Access Journals (Sweden)

    Songrui Zhao

    2017-09-01

    Full Text Available p-Type doping represents a key step towards III-nitride (InN, GaN, AlN optoelectronic devices. In the past, tremendous efforts have been devoted to obtaining high quality p-type III-nitrides, and extraordinary progress has been made in both materials and device aspects. In this article, we intend to discuss a small portion of these processes, focusing on the molecular beam epitaxy (MBE-grown p-type InN and AlN—two bottleneck material systems that limit the development of III-nitride near-infrared and deep ultraviolet (UV optoelectronic devices. We will show that by using MBE-grown nanowire structures, the long-lasting p-type doping challenges of InN and AlN can be largely addressed. New aspects of MBE growth of III-nitride nanostructures are also discussed.

  1. Efficient continuous-wave nonlinear frequency conversion in high-Q gallium nitride photonic crystal cavities on silicon

    Directory of Open Access Journals (Sweden)

    Mohamed Sabry Mohamed

    2017-03-01

    Full Text Available We report on nonlinear frequency conversion from the telecom range via second harmonic generation (SHG and third harmonic generation (THG in suspended gallium nitride slab photonic crystal (PhC cavities on silicon, under continuous-wave resonant excitation. Optimized two-dimensional PhC cavities with augmented far-field coupling have been characterized with quality factors as high as 4.4 × 104, approaching the computed theoretical values. The strong enhancement in light confinement has enabled efficient SHG, achieving a normalized conversion efficiency of 2.4 × 10−3 W−1, as well as simultaneous THG. SHG emission power of up to 0.74 nW has been detected without saturation. The results herein validate the suitability of gallium nitride for integrated nonlinear optical processing.

  2. 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.

  3. 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

  4. 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.

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

    Directory of Open Access Journals (Sweden)

    Paul C. McIntyre

    2012-07-01

    Full Text Available 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.

  6. Surface cleaning procedures for thin films of indium gallium nitride grown on sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Douglass, K.; Hunt, S. [Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716 (United States); Teplyakov, A., E-mail: andrewt@udel.edu [Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716 (United States); Opila, R.L. [Department of Material Science and Engineering, University of Delaware, Newark, DE 19716 (United States)

    2010-12-15

    Surface preparation procedures for indium gallium nitride (InGaN) thin films were analyzed for their effectiveness for carbon and oxide removal as well as for the resulting surface roughness. Aqua regia (3:1 mixture of concentrated hydrochloric acid and concentrated nitric acid, AR), hydrofluoric acid (HF), hydrochloric acid (HCl), piranha solution (1:1 mixture of sulfuric acid and 30% H{sub 2}O{sub 2}) and 1:9 ammonium sulfide:tert-butanol were all used along with high temperature anneals to remove surface contamination. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were utilized to study the extent of surface contamination and surface roughness, respectively. The ammonium sulfide treatment provided the best overall removal of oxygen and carbon. Annealing over 700 deg. C after a treatment showed an even further improvement in surface contamination removal. The piranha treatment resulted in the lowest residual carbon, while the ammonium sulfide treatment leads to the lowest residual oxygen. AFM data showed that all the treatments decreased the surface roughness (with respect to as-grown specimens) with HCl, HF, (NH{sub 4}){sub 2}S and RCA procedures giving the best RMS values ({approx}0.5-0.8 nm).

  7. Platinum nanoparticles on gallium nitride surfaces: effect of semiconductor doping on nanoparticle reactivity.

    Science.gov (United States)

    Schäfer, Susanne; Wyrzgol, Sonja A; Caterino, Roberta; Jentys, Andreas; Schoell, Sebastian J; Hävecker, Michael; Knop-Gericke, Axel; Lercher, Johannes A; Sharp, Ian D; Stutzmann, Martin

    2012-08-01

    Platinum nanoparticles supported on n- and p-type gallium nitride (GaN) are investigated as novel hybrid systems for the electronic control of catalytic activity via electronic interactions with the semiconductor support. In situ oxidation and reduction were studied with high pressure photoemission spectroscopy. The experiments revealed that the underlying wide-band-gap semiconductor has a large influence on the chemical composition and oxygen affinity of supported nanoparticles under X-ray irradiation. For as-deposited Pt cuboctahedra supported on n-type GaN, a higher fraction of oxidized surface atoms was observed compared to cuboctahedral particles supported on p-type GaN. Under an oxygen atmosphere, immediate oxidation was recorded for nanoparticles on n-type GaN, whereas little oxidation was observed for nanoparticles on p-type GaN. Together, these results indicate that changes in the Pt chemical state under X-ray irradiation depend on the type of GaN doping. The strong interaction between the nanoparticles and the support is consistent with charge transfer of X-ray photogenerated free carriers at the semiconductor-nanoparticle interface and suggests that GaN is a promising wide-band-gap support material for photocatalysis and electronic control of catalysis.

  8. Gallium nitride vertical power devices on foreign substrates: a review and outlook

    Science.gov (United States)

    Zhang, Yuhao; Dadgar, Armin; Palacios, Tomás

    2018-07-01

    Vertical gallium nitride (GaN) power devices have attracted increased attention due to their superior high-voltage and high-current capacity as well as easier thermal management than lateral GaN high electron mobility transistors. Vertical GaN devices are promising candidates for next-generation power electronics in electric vehicles, data centers, smart grids and renewable energy process. The use of low-cost foreign substrates such as silicon (Si) substrates, instead of the expensive free-standing GaN substrates, could greatly trim material cost and enable large-diameter wafer processing while maintaining high device performance. This review illustrates recent progress in material epitaxy, device design, device physics and processing technologies for the development of vertical GaN power devices on low-cost foreign substrates. Although the device technologies are still at the early stage of development, state-of-the-art vertical GaN-on-Si power diodes have already shown superior Baliga’s figure of merit than commercial SiC and Si power devices at the voltage classes beyond 600 V. Furthermore, we unveil the design space of vertical GaN power devices on native and different foreign substrates, from the analysis of the impact of dislocation and defects on device performance. We conclude by identifying the application space, current challenges and exciting research opportunities in this very dynamic research field.

  9. High-efficiency and low-loss gallium nitride dielectric metasurfaces for nanophotonics at visible wavelengths

    Science.gov (United States)

    Emani, Naresh Kumar; Khaidarov, Egor; Paniagua-Domínguez, Ramón; Fu, Yuan Hsing; Valuckas, Vytautas; Lu, Shunpeng; Zhang, Xueliang; Tan, Swee Tiam; Demir, Hilmi Volkan; Kuznetsov, Arseniy I.

    2017-11-01

    The dielectric nanophotonics research community is currently exploring transparent material platforms (e.g., TiO2, Si3N4, and GaP) to realize compact high efficiency optical devices at visible wavelengths. Efficient visible-light operation is key to integrating atomic quantum systems for future quantum computing. Gallium nitride (GaN), a III-V semiconductor which is highly transparent at visible wavelengths, is a promising material choice for active, nonlinear, and quantum nanophotonic applications. Here, we present the design and experimental realization of high efficiency beam deflecting and polarization beam splitting metasurfaces consisting of GaN nanostructures etched on the GaN epitaxial substrate itself. We demonstrate a polarization insensitive beam deflecting metasurface with 64% and 90% absolute and relative efficiencies. Further, a polarization beam splitter with an extinction ratio of 8.6/1 (6.2/1) and a transmission of 73% (67%) for p-polarization (s-polarization) is implemented to demonstrate the broad functionality that can be realized on this platform. The metasurfaces in our work exhibit a broadband response in the blue wavelength range of 430-470 nm. This nanophotonic platform of GaN shows the way to off- and on-chip nonlinear and quantum photonic devices working efficiently at blue emission wavelengths common to many atomic quantum emitters such as Ca+ and Sr+ ions.

  10. Possibility of the use of intermediate carbidsiliconoxide nanolayers on polydiamond substrates for gallium nitride layers epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Averichkin, P. A., E-mail: P-Yugov@mail.ru; Donskov, A. A. [State Research and Design Institute of Rare-Metal Industry Giredmet AO (Russian Federation); Dukhnovsky, M. P. [R & D Enterprise Istok (Russian Federation); Knyazev, S. N. [State Research and Design Institute of Rare-Metal Industry Giredmet AO (Russian Federation); Kozlova, Yu. P. [Russian Academy of Sciences, Institute for Nuclear Research (Russian Federation); Yugova, T. G.; Belogorokhov, I. A. [State Research and Design Institute of Rare-Metal Industry Giredmet AO (Russian Federation)

    2016-04-15

    The results of using carbidsiliconoxide (a-C:SiO1{sub .5}) films with a thickness of 30–60 nm, produced by the pyrolysis annealing of oligomethylsilseskvioksana (CH{sub 3}–SiO{sub 1.5}){sub n} with cyclolinear (staircased) molecular structure, as intermediate films in the hydride vapor phase epitaxy of gallium nitride on polycrystalline CVD-diamond substrates are presented. In the pyrolysis annealing of (CH{sub 3}–SiO{sub 1.5}){sub n} films in an atmosphere of nitrogen at a temperature of 1060°C, methyl radicals are carbonized to yield carbon atoms chemically bound to silicon. In turn, these atoms form a SiC monolayer on the surface of a-C:SiO{sub 1.5} films via covalent bonding with silicon. It is shown that GaN islands grow on such an intermediate layer on CVD-polydiamond substrates in the process of hydride vapor phase epitaxy in a vertical reactor from the GaCl–NH{sub 3}–N{sub 2} gas mixture.

  11. Low temperature metalorganic chemical vapor deposition of gallium nitride using dimethylhydrazine as nitrogen source

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, Y.J.; Hong, L.S.; Huang, K.F.; Tsay, J.E

    2002-11-01

    Gallium nitride (GaN) films have been homoepitaxially grown by low pressure metalorganic chemical vapor deposition technique using dimethylhydrazine (DMHy) and trimethylgallium (TMG) as the reactants at low temperatures ranging from 873 to 923 K and a constant pressure of 10 Torr. The potential of utilizing DMHy as a nitrogen source is evaluated through understanding the kinetics of GaN film growth. A growth rate dependency study with respect to DMHy and TMG concentrations indicates that Langmuir-Hinshelwood typed reaction dominates the film growth. From a model fitting to the experimental film growth rate, the adsorption equilibrium constant of DMHy is found to be approximately 1/20 that of TMG, indicating that V/III feed ratio can be reduced down to 20 to obtain a stoichiometric GaN film. Based on X-ray photoelectron spectroscope measurement, the films formed by DMHy, however, accompany significant carbon contamination due to the strong C-N bonding in DMHy. The contamination can be relieved effectively by introducing H{sub 2} into the reaction.

  12. Low temperature metalorganic chemical vapor deposition of gallium nitride using dimethylhydrazine as nitrogen source

    International Nuclear Information System (INIS)

    Hsu, Y.J.; Hong, L.S.; Huang, K.F.; Tsay, J.E.

    2002-01-01

    Gallium nitride (GaN) films have been homoepitaxially grown by low pressure metalorganic chemical vapor deposition technique using dimethylhydrazine (DMHy) and trimethylgallium (TMG) as the reactants at low temperatures ranging from 873 to 923 K and a constant pressure of 10 Torr. The potential of utilizing DMHy as a nitrogen source is evaluated through understanding the kinetics of GaN film growth. A growth rate dependency study with respect to DMHy and TMG concentrations indicates that Langmuir-Hinshelwood typed reaction dominates the film growth. From a model fitting to the experimental film growth rate, the adsorption equilibrium constant of DMHy is found to be approximately 1/20 that of TMG, indicating that V/III feed ratio can be reduced down to 20 to obtain a stoichiometric GaN film. Based on X-ray photoelectron spectroscope measurement, the films formed by DMHy, however, accompany significant carbon contamination due to the strong C-N bonding in DMHy. The contamination can be relieved effectively by introducing H 2 into the reaction

  13. 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.

  14. 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).

  15. Growth and characterisation of group-III nitride-based nanowires for devices

    Energy Technology Data Exchange (ETDEWEB)

    Meijers, R J

    2007-08-30

    One of the main goals of this thesis was to get more insight into the mechanisms driving the growth of nitride nanowires by plasma-assisted molecular beam epitaxy (PA-MBE). The influence of the group-III and group-V flux as well as the substrate temperature T{sub sub} has been studied leading to the conclusion that the III-V ratio determines the growth mode. Ga desorption limits the temperature range to grow GaN nanowires and dissociation of InN is the limiting factor for InN nanowire growth. A reduction of the surface diffusivity on polar surfaces under N-rich conditions explains the anisotropic growth. Growth kinetics of the nanowires show that there are two important contributions to the growth. The first is growth by direct impingement and its contribution is independent of the nanowire diameter. The second contribution comes from atoms, which absorb on the substrate or wire sidewalls and diffuse along the sidewalls to the top of the wire, which acts as an effective sink for the adatoms due to a reduced surface mobility on the polar top of the wires. This diffusion channel, which is enhanced at higher T{sub sub}, becomes more significant for smaller wire diameters, because its contribution scales like 1/d. Experiments with an interruption of the growth and sharp interfaces in TEM images of heterostructures show that the suggestion in literature of a droplet-mediated PA-MBE nitride growth has to be discarded. Despite a thin amorphous silicon nitride wetting layer on the substrate surface, both GaN and InN nanowires grow in the wurtzite structure and epitaxially in a one-to-one relation to the Si(111) substrate surface. There is no evidence for cubic phases. TEM images and optical studies display a high crystalline and optical quality of GaN and InN nanowires. The substrate induces some strain in the bottom part of the nanowires, especially in InN due to the lower T{sub sub} than for GaN, which is released without the formation of dislocations. Only some stacking

  16. Nanowires and nanotubes of BN, GaN and Si3N4

    International Nuclear Information System (INIS)

    Deepak, F.L.; Gundiah, G.; Govindaraj, A.; Rao, C.N.

    2002-01-01

    Simple methods of synthesizing nanotubes and nanowires of boron nitride, gallium nitride and silicon nitride have been investigated. The nanotubes and nanowires have been examined by electron microscopy and other techniques. In the case of BN, activated carbon or multi-walled carbon nanotubes (MWNTs) was heated with boric acid in the presence of NH 3 . With activated carbon, BN nanowires constitute the primary products, but good yields of BN nanotubes are obtained with MWNTs. Aligned BN nanotubes are obtained when aligned MWNTs are employed as the starting material suggesting templating role of carbon nanotubes. Single crystal gallium nitride nanowires have been obtained by heating carbon nanotubes coated with gallium acetylacetonate in NH 3 vapor at 910 o C. Single walled carbon nanotubes were used as templated to reduce the diameter of the GaN nanowires. The growth direction of the GaN nanowires is nearly perpendicular to the [100] planes and the nanowires exhibit satisfactory photoluminescence spectra. Si 3 N 4 nanowires have been synthesized by heating multi-walled carbon nanotubes with silica gel at 1360 o C in an atmosphere of NH 3 . Si 3 N 4 nanotubes are found occasionally when aligned multi-walled nanotubes are employed as templates. (author)

  17. 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.

  18. 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.

  19. Design and Characterization of p-i-n Devices for Betavoltaic Microbatteries on Gallium Nitride

    Science.gov (United States)

    Khan, Muhammad Raziuddin A.

    Betavoltaic microbatteries convert nuclear energy released as beta particles directly into electrical energy. These batteries are well suited for electrical applications such as micro-electro-mechanical systems (MEMS), implantable medical devices and sensors. Such devices are often located in hard to access places where long life, micro-size and lightweight are required. The working principle of a betavoltaic device is similar to a photovoltaic device; they differ only in that the electron hole pairs (EHPs) are generated in the device by electrons instead of photons. In this study, the performance of a betavoltaic device fabricated from gallium nitride (GaN) is investigated for beta particle energies equivalent to Tritium (3H) and Nickel-63 (N63) beta sources. GaN is an attractive choice for fabricating betavoltaic devices due to its wide band gap and radiation resistance. Another advantage GaN has is that it can be alloyed with aluminum (Al) to further increase the bandgap, resulting in a higher output power and increased efficiency. Betavoltaic devices were fabricated on p-i-n GaN structures grown by metalorganic chemical vapor deposition (MOCVD). The devices were characterized using current - voltage (IV) measurements without illumination (light or beta), using a laser driven light source, and under an electron beam. Dark IV measurements showed a turn on-voltage of ~ 3.4 V, specific-on-resistance of 15.1 m O-cm2, and a leakage current of 0.5 mA at -- 10 V. A clear photo-response was observed when IV curves were measured for these devices under a light source at a wavelength of 310 nm (4.0 eV). These devices were tested under an electron beam in order to evaluate their behavior as betavoltaic microbatteries without using radioactive materials. Output power of 70 nW and 640 nW with overall efficiencies of 1.2% and 4.0% were determined at the average energy emission of 3H (5.6 keV) and 63N (17 keV) respectively.

  20. PLD synthesis of GaN nanowires and nanodots on patterned catalyst surface for field emission study

    Energy Technology Data Exchange (ETDEWEB)

    Ng, D.K.T.; Hong, M.H. [National University of Singapore (Singapore). Department of Electrical and Computer Engineering; Data Storage Institute, Singapore (Singapore); Tan, L.S. [National University of Singapore (Singapore). Department of Electrical and Computer Engineering; Zhu, Y.W.; Sow, C.H. [National University of Singapore (Singapore). Nanoscience and Nanotechnology Initiative; National University of Singapore (Singapore). Department of Physics

    2008-11-15

    Patterned gallium nitride nanowires and nanodots have been grown on n-Si(100) substrates by pulsed laser deposition. The nanostructures are patterned using a physical mask, resulting in regions of nanowire growth of different densities. The field emission (FE) characteristics of the patterned gallium nitride nanowires show a turn-on field of 9.06 V/{mu}m to achieve a current density of 0.01 mA/cm{sup 2} and an enhanced field emission current density as high as 0.156 mA/cm{sup 2} at an applied field of 11 V/{mu}m. Comparing the peak FE current densities of both the nanowires and nanodots, the peak FE current density of nanowires is around 700 times higher than that of the peak FE current density of nanodots since nanodots have a lower aspect ratio compared to nanowires. The field emission results indicate that, besides density difference, crystalline quality as well as the low electron affinity of gallium nitride, high aspect ratio of gallium nitride nanostructures will greatly enhance their field emission properties. (orig.)

  1. 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

  2. Urchin-like artificial gallium oxide nanowires grown by a novel MOCVD/CVD-based route for random laser application

    Energy Technology Data Exchange (ETDEWEB)

    Melo, Ronaldo P. de [Programa de Pós-Graduação em Ciências de Materiais, Universidade Federal de Pernambuco, Recife (Brazil); Colégio Militar do Recife, Exército Brasileiro, Recife PE 50730-120 (Brazil); Oliveira, Nathalia Talita C. [Programa de Pós-Graduação em Ciências de Materiais, Universidade Federal de Pernambuco, Recife (Brazil); Dominguez, Christian Tolentino; Gomes, Anderson S. L.; Araújo, Cid B. de [Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife (Brazil); Falcão, Eduardo H. L.; Alves, Severino; Luz, Leonis L. da [Departamento de Química Fundamental, Universidade Federal de Pernambuco, 50670-901 Recife (Brazil); Chassagnon, Remi [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS-Université de Bourgogne, 9 Av. A. Savary, BP 47870, 21078 Dijon Cedex (France); Sacilotti, Marco [Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife (Brazil); Nanoform Group, Laboratoire Interdisciplinaire Carnot de Bourgogne, Université de Bourgogne, Dijon (France)

    2016-04-28

    A novel procedure based on a two-step method was developed to obtain β-Ga{sub 2}O{sub 3} nanowires by the chemical vapor deposition (CVD) method. The first step consists in the gallium micro-spheres growth inside a metal-organic chemical vapor deposition environment, using an organometallic precursor. Nanoscale spheres covering the microspheres were obtained. The second step involves the CVD oxidization of the gallium micro-spheres, which allow the formation of β-Ga{sub 2}O{sub 3} nanowires on the micro-sphere surface, with the final result being a nanostructure mimicking nature's sea urchin morphology. The grown nanomaterial is characterized by several techniques, including X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray, transmission electron microscopy, and photoluminescence. A discussion about the growth mechanism and the optical properties of the β-Ga{sub 2}O{sub 3} material is presented considering its unknown true bandgap value (extending from 4.4 to 5.68 eV). As an application, the scattering properties of the nanomaterial are exploited to demonstrate random laser emission (around 570 nm) when it is permeated with a laser dye liquid solution.

  3. 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.

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

    Science.gov (United States)

    Malka, Dror; Danan, Yossef; Ramon, Yehonatan; Zalevsky, Zeev

    2016-01-01

    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). PMID:28773638

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

    Science.gov (United States)

    Malka, Dror; Danan, Yossef; Ramon, Yehonatan; Zalevsky, Zeev

    2016-06-25

    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).

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

    Science.gov (United States)

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

    2014-06-01

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

  7. Gallium nitride based transistors for high-efficiency microwave switch-mode amplifiers

    Energy Technology Data Exchange (ETDEWEB)

    Maroldt, Stephan

    2012-07-01

    Highly-efficient switch-mode power amplifiers form key elements in future fully-digital base stations for mobile communication. This novel digital base station concept reduces system energy consumption, complexity, size and costs, while the flexibility in terms of multi-band operation and signal modulation improves. In this work, innovative core circuits for digital high-efficiency class-D and class-S power amplifiers based on gallium nitride (GaN) technology were developed for the application in digital base stations. A combination of optimized GaN devices and improvements in circuit design allow a highly-efficient switch-mode operation at mobile communication frequencies between 0.45 GHz and 2 GHz. Transistor device modeling for switch-mode operation, the simulation environment, and a broadband measurement system were established for the design and evaluation of digital switchmode power amplifiers. The design of broadband core circuits for switch-mode amplifier concepts was analyzed for dual-stage amplifier circuits, using an initial GaN technology with a gate length of 0.25 {mu}m. A speed-enhanced driver stage improved the circuit switching speed sufficiently above 1 GHz. Speed and efficiency of the amplifier core circuits were studied related to transistor parameters like cut-off frequency or gate capacitance. A reduced gate length was found to improve the switching speed, while a lower on-resistance allows the reduction of the inherent static losses of the GaN-based switches. Apart from this, the restriction of a 50 Ohm environment was found to be a major output power and switching speed limitation, due to a poor switching drive capability of the input capacitance of the GaN circuit. Finally, the optimized transistor and circuit design with an output gate width of 1.2 mm were effectively implemented in the given environment for an operation up to 2 GHz with a high drain efficiency of >65% and a digital output power of 5 W. A maximum output power of 9.7 W and a

  8. Effect of substrate temperature on the microstructural properties of titanium nitride nanowires grown by pulsed laser deposition

    International Nuclear Information System (INIS)

    Gbordzoe, S.; Kotoka, R.; Craven, Eric; Kumar, D.; Wu, F.; Narayan, J.

    2014-01-01

    The current work reports on the growth and microstructural characterization of titanium nitride (TiN) nanowires on single crystal silicon substrates using a pulsed laser deposition method. The physical and microstructural properties of the nanowires were characterized using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The corrosion properties of the TiN nanowires compared to TiN thin film were evaluated using Direct Current potentiodynamic and electrochemical impedance spectroscopy. The nanowires corroded faster than the TiN thin film, because the nanowires have a larger surface area which makes them more reactive in a corrosive environment. It was observed from the FESEM image analyses that as the substrate temperature increases from 600 °C to 800 °C, there was an increase in both diameter (25 nm–50 nm) and length (150 nm–250 nm) of the nanowire growth. There was also an increase in spatial density with an increase of substrate temperature. The TEM results showed that the TiN nanowires grow epitaxially with the silicon substrate via domain matching epitaxy paradigm, despite a large misfit

  9. Structural, electronic and magnetic properties of carbon doped boron nitride nanowire: Ab initio study

    Energy Technology Data Exchange (ETDEWEB)

    Jalilian, Jaafar, E-mail: JaafarJalilian@gmail.com [Young Researchers and Elite Club, Kermanshah Br anch, Islamic Azad University, P.O. Box: 6718997551, Kermanshah (Iran, Islamic Republic of); Kanjouri, Faramarz, E-mail: kanjouri@khu.ac.ir [Physics Department, Faculty of Science, Kharazmi University, University Square, P.O. Box: 3197937551, Karaj (Iran, Islamic Republic of)

    2016-11-15

    Using spin-polarized density functional theory calculations, we demonstrated that carbon doped boron nitride nanowire (C-doped BNNW) has diverse electronic and magnetic properties depending on position of carbon atoms and their percentages. Our results show that only when one carbon atom is situated on the edge of the nanowire, C-doped BNNW is transformed into half-metal. The calculated electronic structure of the C-doped BNNW suggests that doping carbon can induce localized edge states around the Fermi level, and the interaction among localized edge states leads to semiconductor to half-metal transition. Overall, the bond reconstruction causes of appearance of different electronic behavior such as semiconducting, half-metallicity, nonmagnetic metallic, and ferromagnetic metallic characters. The formation energy of the system shows that when a C atom is doped on surface boron site, system is more stable than the other positions of carbon impurity. Our calculations show that C-doped BNNW may offer unique opportunities for developing nanoscale spintronic materials.

  10. 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

  11. Self-catalyzed growth of dilute nitride GaAs/GaAsSbN/GaAs core-shell nanowires by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Kasanaboina, Pavan Kumar [Department of Electrical and Computer Engineering, North Carolina A& T State University, Greensboro, North Carolina 27411 (United States); Ahmad, Estiak [Nanoengineering, Joint School of Nanoscience and Nanoengineering, NCA& T State University, Greensboro, North Carolina 27401 (United States); Li, Jia; Iyer, Shanthi [Department of Electrical and Computer Engineering, North Carolina A& T State University, Greensboro, North Carolina 27411 (United States); Nanoengineering, Joint School of Nanoscience and Nanoengineering, NCA& T State University, Greensboro, North Carolina 27401 (United States); Reynolds, C. Lewis; Liu, Yang [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States)

    2015-09-07

    Bandgap tuning up to 1.3 μm in GaAsSb based nanowires by incorporation of dilute amount of N is reported. Highly vertical GaAs/GaAsSbN/GaAs core-shell configured nanowires were grown for different N contents on Si (111) substrates using plasma assisted molecular beam epitaxy. X-ray diffraction analysis revealed close lattice matching of GaAsSbN with GaAs. Micro-photoluminescence (μ-PL) revealed red shift as well as broadening of the spectra attesting to N incorporation in the nanowires. Replication of the 4K PL spectra for several different single nanowires compared to the corresponding nanowire array suggests good compositional homogeneity amongst the nanowires. A large red shift of the Raman spectrum and associated symmetric line shape in these nanowires have been attributed to phonon localization at point defects. Transmission electron microscopy reveals the dominance of stacking faults and twins in these nanowires. The lower strain present in these dilute nitride nanowires, as opposed to GaAsSb nanowires having the same PL emission wavelength, and the observation of room temperature PL demonstrate the advantage of the dilute nitride system offers in the nanowire configuration, providing a pathway for realizing nanoscale optoelectronic devices in the telecommunication wavelength region.

  12. Design and Implementation of a High-Flux Photoneutron Converter for Analysis of Fast Neutron Radiation Damage on Gallium Nitride Transistors

    Science.gov (United States)

    2017-06-01

    as the polarization and 2DEG control between aluminum gallium nitride (AlGaN) and GaN layers. Third, the physical and electrical properties of...electron gases induced by spontaneous and piezoelectric polarization in undoped and doped AlGaN/GaN heterostructures,” Journal of Applied Physics , vol...relationship of the electrical and physical characteristics of the devices with respect to the fast neutron fluence. The damage was also analyzed using

  13. 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

  14. Horizontal Assembly of Single Nanowire Diode Fabricated by p-n Junction GaN NW Grown by MOCVD

    Directory of Open Access Journals (Sweden)

    Ji-Hyeon Park

    2014-01-01

    Full Text Available Uniaxially p-n junction gallium nitride nanowires have been synthesized via metal-organic chemical vapor deposition method. Nanowires prepared on Si(111 substrates were found to grow perpendicular to the substrate, and the transmission electron microscopy studies demonstrated that the nanowires had singlecrystalline structures with a growth axis. The parallel assembly of the p-n junction nanowire was prepared on a Si substrate with a thermally grown SiO2 layer. The transport studies of horizontal gallium nitride nanowire structures assembled from p- and n-type materials show that these junctions correspond to well-defined p-n junction diodes. The p-n junction devices based on GaN nanowires suspended over the electrodes were fabricated and their electrical properties were investigated. The horizontally assembled gallium nitride nanowire diodes suspended over the electrodes exhibited a substantial increase in conductance under UV light exposure. Apart from the selectivity to different light wavelengths, high responsivity and extremely short response time have also been obtained.

  15. Ternary nanocomposite of polyaniline/manganese dioxide/titanium nitride nanowire array for supercapacitor electrode

    International Nuclear Information System (INIS)

    Xia, Chi; Xie, Yibing; Du, Hongxiu; Wang, Wei

    2015-01-01

    The electroactive polyaniline (PANI) and manganese oxide (MnO 2 ) were integrated with titanium nitride (TiN) nanowire array (NWA) to form PANI/MnO 2 /TiN ternary nanocomposite for supercapacitor application. TiN NWA was prepared via a seed-assisted hydrothermal synthesis and ammonia nitridization process. The electroactive MnO 2 and PANI was layer-by-layer coated on TiN NWA to form heterogeneous coaxial structure through a stepwise electrodeposition process. Scanning electron micrographs revealed that the well-separated TiN NWA was composed of well-distributed nanowires with diameters in the range of 10–30 nm and a total length of 1.5 μm. A villiform MnO 2 layer with a thickness of 10–20 nm covered on TiN NWA to form MnO 2 /TiN NWA composite. The coral-like PANI layer with thicknesses in the range of 20–50 nm covered on the above MnO 2 /TiN NWA to form PANI/MnO 2 /TiN NWA. Electrochemical measurements showed that a high specific capacitance of 674 F g −1 at a current density of 1 A g −1 (based on total mass of PANI/MnO 2 ) was obtained for PANI/MnO 2 /TiN NWA ternary nanocomposite, which was much higher than that of PANI/MnO 2 /carbon-cloth composites reported previously. This ternary nanocomposite also showed a good rate and cycling stability. Moreover, in comparison with PANI/TiN NWA or MnO 2 /TiN NWA, the specific capacitance of PANI/MnO 2 /TiN NWA was obviously enhanced due to the extra pseudocapacitance contribution and the effective surface area of coral-like PANI layer, showing the advantage of manipulating the heterogeneous coaxial configuration between PANI and MnO 2 for fundamentally improved capacitive performance. These results demonstrated that PANI/MnO 2 /TiN NWA ternary nanocomposite was a promising candidate electrode material for supercapacitor application

  16. Ternary nanocomposite of polyaniline/manganese dioxide/titanium nitride nanowire array for supercapacitor electrode

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Chi; Xie, Yibing, E-mail: ybxie@seu.edu.cn; Du, Hongxiu; Wang, Wei [Southeast University, School of Chemistry and Chemical Engineering (China)

    2015-01-15

    The electroactive polyaniline (PANI) and manganese oxide (MnO{sub 2}) were integrated with titanium nitride (TiN) nanowire array (NWA) to form PANI/MnO{sub 2}/TiN ternary nanocomposite for supercapacitor application. TiN NWA was prepared via a seed-assisted hydrothermal synthesis and ammonia nitridization process. The electroactive MnO{sub 2} and PANI was layer-by-layer coated on TiN NWA to form heterogeneous coaxial structure through a stepwise electrodeposition process. Scanning electron micrographs revealed that the well-separated TiN NWA was composed of well-distributed nanowires with diameters in the range of 10–30 nm and a total length of 1.5 μm. A villiform MnO{sub 2} layer with a thickness of 10–20 nm covered on TiN NWA to form MnO{sub 2}/TiN NWA composite. The coral-like PANI layer with thicknesses in the range of 20–50 nm covered on the above MnO{sub 2}/TiN NWA to form PANI/MnO{sub 2}/TiN NWA. Electrochemical measurements showed that a high specific capacitance of 674 F g{sup −1} at a current density of 1 A g{sup −1} (based on total mass of PANI/MnO{sub 2}) was obtained for PANI/MnO{sub 2}/TiN NWA ternary nanocomposite, which was much higher than that of PANI/MnO{sub 2}/carbon-cloth composites reported previously. This ternary nanocomposite also showed a good rate and cycling stability. Moreover, in comparison with PANI/TiN NWA or MnO{sub 2}/TiN NWA, the specific capacitance of PANI/MnO{sub 2}/TiN NWA was obviously enhanced due to the extra pseudocapacitance contribution and the effective surface area of coral-like PANI layer, showing the advantage of manipulating the heterogeneous coaxial configuration between PANI and MnO{sub 2} for fundamentally improved capacitive performance. These results demonstrated that PANI/MnO{sub 2}/TiN NWA ternary nanocomposite was a promising candidate electrode material for supercapacitor application.

  17. Formation of gallium nitride templates and freestanding substrates by hydride vapor phase epitaxy for homoepitaxial growth of III-nitride devices

    Science.gov (United States)

    Williams, Adrian Daniel

    Gallium nitride (GaN) is a direct wide band gap semiconductor currently under heavy development worldwide due to interest in its applications in ultra-violet optoelectronics, power electronics, devices operating in harsh environments (high temperature or corrorsive), etc. While a number of devices have been demonstrated with this material and its related alloys, the unavailability of GaN substrates is seen as one of the current major bottlenecks to both material quality and device performance. This dissertation is concerned with the synthesis of high quality GaN substrates by the hydride vapor phase epitaxy method (HVPE). In this work, the flow of growth precursors in a home-built HVPE reactor was modeled by the Navier-Stokes equation and solved by finite element analysis to promote uniformity of GaN on 2'' sapphire substrates. Kinetics of growth was studied and various regimes of growth were identified to establish a methodology for HVPE GaN growth, independent of reactor geometry. GaN templates as well as bulk substrates were fabricated in this work. Realization of freestanding GaN substrates was achieved through discovery of a natural stress-induced method of separating bulk GaN from sapphire via mechanical failure of a low-temperature GaN buffer layer. Such a process eliminates the need for pre- or post-processing of sapphire substrates, as is currently the standard. Stress in GaN-on-sapphire is discussed, with the dominant contributor identified as thermal stress due to thermal expansion coefficient mismatch between the two materials. This thermal stress is analyzed using Stoney's equation and conditions for crack-free growth of thick GaN substrates were identified. An etch-back process for planarizing GaN templates was also developed and successfully applied to rough GaN templates. The planarization of GaN has been mainly addressed by chemo-mechanical polishing (CMP) methods in the literature, with notable shortcomings including the inability to effectively

  18. 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

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

    Science.gov (United States)

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

    2018-06-01

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

  20. 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.

  1. 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.

  2. 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.

  3. Highly catalytic and stabilized titanium nitride nanowire array-decorated graphite felt electrodes for all vanadium redox flow batteries

    Science.gov (United States)

    Wei, L.; Zhao, T. S.; Zeng, L.; Zeng, Y. K.; Jiang, H. R.

    2017-02-01

    In this work, we prepare a highly catalytic and stabilized titanium nitride (TiN) nanowire array-decorated graphite felt electrode for all vanadium redox flow batteries (VRFBs). Free-standing TiN nanowires are synthesized by a two-step process, in which TiO2 nanowires are first grown onto the surface of graphite felt via a seed-assisted hydrothermal method and then converted to TiN through nitridation reaction. When applied to VRFBs, the prepared electrode enables the electrolyte utilization and energy efficiency to be 73.9% and 77.4% at a high current density of 300 mA cm-2, which are correspondingly 43.3% and 15.4% higher than that of battery assembled with a pristine electrode. More impressively, the present battery exhibits good stability and high capacity retention during the cycle test. The superior performance is ascribed to the significant improvement in the electrochemical kinetics and enlarged active sites toward V3+/V2+ redox reaction.

  4. 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

  5. Magnesium acceptor in gallium nitride. II. Koopmans-tuned Heyd-Scuseria-Ernzerhof hybrid functional calculations of its dual nature and optical properties

    Science.gov (United States)

    Demchenko, D. O.; Diallo, I. C.; Reshchikov, M. A.

    2018-05-01

    The problem of magnesium acceptor in gallium nitride is that experimental photoluminescence measurements clearly reveal a shallow defect state, while most theoretical predictions favor a localized polaronic defect state. To resolve this contradiction, we calculate properties of magnesium acceptor using the Heyd-Scuseria-Ernzerhof (HSE) hybrid functional, tuned to fulfill the generalized Koopmans condition. We test Koopmans tuning of HSE for defect calculations in GaN using two contrasting test cases: a deep state of gallium vacancy and a shallow state of magnesium acceptor. The obtained parametrization of HSE allows calculations of optical properties of acceptors using neutral defect-state eigenvalues, without relying on corrections due to charged defects in periodic supercells. Optical transitions and vibrational properties of M gGa defect are analyzed to bring the dual (shallow and deep) nature of this defect into accord with experimental photoluminescence measurements of the ultraviolet band in Mg-doped GaN samples.

  6. High-luminosity blue and blue-green gallium nitride light-emitting diodes.

    Science.gov (United States)

    Morkoç, H; Mohammad, S N

    1995-01-06

    Compact and efficient sources of blue light for full color display applications and lighting eluded and tantalized researchers for many years. Semiconductor light sources are attractive owing to their reliability and amenability to mass manufacture. However, large band gaps are required to achieve blue color. A class of compound semiconductors formed by metal nitrides, GaN and its allied compounds AIGaN and InGaN, exhibits properties well suited for not only blue and blue-green emitters, but also for ultraviolet emitters and detectors. What thwarted engineers and scientists from fabricating useful devices from these materials in the past was the poor quality of material and lack of p-type doping. Both of these obstacles have recently been overcome to the point where highluminosity blue and blue-green light-emitting diodes are now available in the marketplace.

  7. 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)

  8. III-nitride disk-in-nanowire 1.2 μm monolithic diode laser on (001)silicon

    KAUST Repository

    Hazari, Arnab

    2015-11-12

    III-nitride nanowirediodeheterostructures with multiple In0.85Ga0.15N disks and graded InGaN mode confining regions were grown by molecular beam epitaxy on (001)Si substrates. The aerial density of the 60 nm nanowires is ∼3 × 1010 cm−2. A radiative recombination lifetime of 1.84 ns in the disks is measured by time-resolved luminescence measurements. Edge-emitting nanowire lasers have been fabricated and characterized. Measured values of Jth, T0, and dg/dn in these devices are 1.24 kA/cm2, 242 K, and 5.6 × 10−17 cm2, respectively. The peak emission is observed at ∼1.2 μm.

  9. 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

  10. The role of titanium aluminide in n-gallium nitride ohmic contact technology

    Science.gov (United States)

    Pelto, Christopher M.

    Ohmic contacts are essential to the realization of efficient and affordable nitride-based electronic and optoelectronic devices. Currently, the most successful ohmic contact schemes to n-GaN are based on the Al/Ti bilayer structure, although the mechanism responsible for the low resistance in these contacts is not sufficiently understood. In this work, the intermetallic TiAl3 has been employed both as a model ohmic contact system to help understand the essential features of the Al/Ti standard contact, as well as a thermally stable oxidation cap for the bilayer structure. A quaternary isotherm of the Al-Ti-Ga-N system was calculated at 600°C, which showed that a sufficient phase topology was present to apply the exchange mechanism to the TiAl 3/GaN couple. The exchange mechanism rationalized the selection of the TiAl3 intermetallic by predicting that an Al-rich AlGaN layer will form at the metal/semiconductor interface. As part of the investigation of these novel contact systems, a thorough characterization was undertaken on both a standard Al/Ti and Au/Ni/Al/Ti contact to n-GaN in which the essential processing parameters and metallurgical properties were identified. The TiAl 3 contact was found to exhibit inferior electrical behavior compared to the Al/Ti bilayer, requiring significantly higher annealing temperatures to achieve comparable specific contact resistance. It is conjectured that this is due to the early formation of a TiN layer at the metal/semiconductor interface of the bilayer contact, even though both contacts are suspected to form the Al-rich nitride layer at higher temperature. As an oxidation cap, the TiAl3 metallization was found to provide much improved performance characteristics compared to the four-layer Au/Al/Ni/Ti standard. The TiAl 3/Al/Ti contact proved to achieve optimal performance at a much lower temperature than the standard, and furthermore showed complete insensitivity to the oxidation content of the annealing ambient. Reaction

  11. 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.

  12. Size-effects in indium gallium arsenide nanowire field-effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Zota, Cezar B., E-mail: cezar.zota@eit.lth.se; Lind, E. [Department of Electrical and Information Technology, Lund University, Lund 22101 (Sweden)

    2016-08-08

    We fabricate and analyze InGaAs nanowire MOSFETs with channel widths down to 18 nm. Low-temperature measurements reveal quantized conductance due to subband splitting, a characteristic of 1D systems. We relate these features to device performance at room-temperature. In particular, the threshold voltage versus nanowire width is explained by direct observation of quantization of the first sub-band, i.e., band gap widening. An analytical effective mass quantum well model is able to describe the observed band structure. The results reveal a compromise between reliability, i.e., V{sub T} variability, and on-current, through the mean free path, in the choice of the channel material.

  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. Development of aluminum gallium nitride based optoelectronic devices operating in deep UV and terahertz spectrum ranges

    Science.gov (United States)

    Zhang, Wei

    In this research project I have investigated AlGaN alloys and their quantum structures for applications in deep UV and terahertz optoelectronic devices. For the deep UV emitter applications the materials and devices were grown by rf plasma-assisted molecular beam epitaxy on 4H-SiC, 6H-SiC and c-plane sapphire substrates. In the growth of AlGaN/AlN multiple quantum wells on SiC substrates, the AlGaN wells were grown under excess Ga, far beyond than what is required for the growth of stoichiometric AlGaN films, which resulted in liquid phase epitaxy growth mode. Due to the statistical variations of the excess Ga on the growth front we found that this growth mode leads to films with lateral variations in the composition and thus, band structure potential fluctuations. Transmission electron microscopy shows that the wells in such structures are not homogeneous but have the appearance of quantum dots. We find by temperature dependent photoluminescence measurements that the multiple quantum wells with band structure potential fluctuations emit at 240 nm and have room temperature internal quantum efficiency as high as 68%. Furthermore, they were found to have a maximum net modal optical gain of 118 cm-1 at a transparency threshold corresponding to 1.4 x 1017 cm-3 excited carriers. We attribute this low transparency threshold to population inversion of only the regions of the potential fluctuations rather than of the entire matrix. Some prototype deep UV emitting LED structures were also grown by the same method on sapphire substrates. Optoelectronic devices for terahertz light emission and detection, based on intersubband transitions in III-nitride semiconductor quantum wells, were grown on single crystal c-plane GaN substrates. Growth conditions such the ratio of group III to active nitrogen fluxes, which determines the appropriate Ga-coverage for atomically smooth growth without requiring growth interruptions were employed. Emitters designed in the quantum cascade

  15. III-nitride disk-in-nanowire 1.2 μm monolithic diode laser on (001)silicon

    Energy Technology Data Exchange (ETDEWEB)

    Hazari, Arnab; Aiello, Anthony; Bhattacharya, Pallab [Center for Photonics and Multiscale Nanomaterials, Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109 (United States); Ng, Tien-Khee; Ooi, Boon S. [Division of Computer, Electrical and Mathematical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900 (Saudi Arabia)

    2015-11-09

    III-nitride nanowire diode heterostructures with multiple In{sub 0.85}Ga{sub 0.15}N disks and graded InGaN mode confining regions were grown by molecular beam epitaxy on (001)Si substrates. The aerial density of the 60 nm nanowires is ∼3 × 10{sup 10} cm{sup −2}. A radiative recombination lifetime of 1.84 ns in the disks is measured by time-resolved luminescence measurements. Edge-emitting nanowire lasers have been fabricated and characterized. Measured values of J{sub th}, T{sub 0}, and dg/dn in these devices are 1.24 kA/cm{sup 2}, 242 K, and 5.6 × 10{sup −17} cm{sup 2}, respectively. The peak emission is observed at ∼1.2 μm.

  16. The growth of axially modulated p–n GaN nanowires by plasma-enhanced chemical vapor deposition

    International Nuclear Information System (INIS)

    Wu, Tung-Hsien; Hong, Franklin Chau-Nan

    2013-01-01

    Due to the n-type characteristics of intrinsic gallium nitride, p-type gallium nitride (GaN) is more difficult to synthesize than n-type gallium nitride in forming the p–n junctions for optoelectronic applications. For the growth of the p-type gallium nitride, magnesium is used as the dopant. The Mg-doped GaN nanowires (NWs) have been synthesized on (111)-oriented n + -silicon substrates by plasma-enhanced chemical vapor deposition. The scanning electron microscope images showed that the GaN NWs were bent at high Mg doping levels, and the transmission electron microscope characterization indicated that single-crystalline GaN NWs grew along < 0001 > orientation. As shown by energy dispersive spectroscopy, the Mg doping levels in GaN NWs increased with increasing partial pressure of magnesium nitride, which was employed as the dopant precursor for p-GaN NW growth. Photoluminescence measurements suggested the presence of both p- and n‐type GaN NWs. Furthermore, the GaN NWs with axial p–n junctions were aligned between either two-Ni or two-Al electrodes by applying alternating current voltages. The current–voltage characteristics have confirmed the formation of axial p–n junctions in GaN nanowires. - Highlights: ► Grow axially modulated GaN nanowires by plasma-enhanced chemical vapor deposition ► Control the Mg concentration of GaN nanowires by tuning Mg 3 N 2 temperature ► Align the GaN nanowires by applying alternating current voltages between electrodes

  17. Electroluminescence from single nanowires by tunnel injection: an experimental study

    International Nuclear Information System (INIS)

    Zimmler, Mariano A; Bao Jiming; Shalish, Ilan; Yi, Wei; Yoon, Joonah; Narayanamurti, Venkatesh; Capasso, Federico

    2007-01-01

    We present a hybrid light-emitting diode structure composed of an n-type gallium nitride nanowire on a p-type silicon substrate in which current is injected along the length of the nanowire. The device emits ultraviolet light under both bias polarities. Tunnel injection of holes from the p-type substrate (under forward bias) and from the metal (under reverse bias) through thin native oxide barriers consistently explains the observed electroluminescence behaviour. This work shows that the standard p-n junction model is generally not applicable to this kind of device structure

  18. A facile route to porous beta-gallium oxide nanowires-reduced graphene oxide hybrids with enhanced photocatalytic efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Xu, X. [State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing 100876 (China); School of Science, Beijing University of Posts and Telecommunications, Beijing 100876 (China); Lei, M., E-mail: minglei@bupt.edu.cn [State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing 100876 (China); School of Science, Beijing University of Posts and Telecommunications, Beijing 100876 (China); Huang, K.; Liang, C.; Xu, J.C.; Shangguan, Z.C. [School of Science, Beijing University of Posts and Telecommunications, Beijing 100876 (China); Yuan, Q.X. [Department of Mathematics and Physics, Zhengzhou Institute of Aeronautical Industry Management, Zhengzhou 450015 (China); Ma, L.H. [School of Science, Beijing University of Posts and Telecommunications, Beijing 100876 (China); Du, Y.X., E-mail: duyinxiao@zzia.edu.cn [Department of Mathematics and Physics, Zhengzhou Institute of Aeronautical Industry Management, Zhengzhou 450015 (China); Fan, D.Y.; Yang, H.J.; Wang, Y.G.; Tang, W.H. [School of Science, Beijing University of Posts and Telecommunications, Beijing 100876 (China)

    2015-02-25

    Highlights: • A facile route was developed to fabricate porous β-Ga{sub 2}O{sub 3} NWs-rGO hybrids. • Supercritical water can act as an efficient reductant to situ-reduce GO into RGO. • The Ga{sub 2}O{sub 3} NWs attach on the surface of RGO through a strong coupling forces. • The photocatalytic performance of the hybrids can be obviously improved. - Abstract: A facile route was developed to fabricate porous beta-gallium oxide nanowires (β-Ga{sub 2}O{sub 3} NWs)-reduced graphene oxide (rGO) hybrids using β-Ga{sub 2}O{sub 3} NWs and graphene oxide (GO) as raw materials. The characterization results indicate that supercritical water can act as an efficient reductant to situ-reduce GO into rGO, and porous β-Ga{sub 2}O{sub 3} NWs can further attach on the surface of as-reduced rGO through a strong coupling forces between the β-Ga{sub 2}O{sub 3} NWs and rGO. The photocatalytic performance of the hybrids can be obviously improved (about 74%) for the decomposition of methylene blue (MB) solution after coupling with 1 wt% rGO compared with the pure β-Ga{sub 2}O{sub 3} NWs. The enhanced photocatalytic activity can be attributed to the synergistic effect of extended optical absorption band, the enrichment of MB molecular on the rGO and the valid inhibition of recombination of photo-generated electron–hole pairs induced by the strong coupling interaction between rGO nanosheets and porous β-Ga{sub 2}O{sub 3} NWs.

  19. A facile route to porous beta-gallium oxide nanowires-reduced graphene oxide hybrids with enhanced photocatalytic efficiency

    International Nuclear Information System (INIS)

    Xu, X.; Lei, M.; Huang, K.; Liang, C.; Xu, J.C.; Shangguan, Z.C.; Yuan, Q.X.; Ma, L.H.; Du, Y.X.; Fan, D.Y.; Yang, H.J.; Wang, Y.G.; Tang, W.H.

    2015-01-01

    Highlights: • A facile route was developed to fabricate porous β-Ga 2 O 3 NWs-rGO hybrids. • Supercritical water can act as an efficient reductant to situ-reduce GO into RGO. • The Ga 2 O 3 NWs attach on the surface of RGO through a strong coupling forces. • The photocatalytic performance of the hybrids can be obviously improved. - Abstract: A facile route was developed to fabricate porous beta-gallium oxide nanowires (β-Ga 2 O 3 NWs)-reduced graphene oxide (rGO) hybrids using β-Ga 2 O 3 NWs and graphene oxide (GO) as raw materials. The characterization results indicate that supercritical water can act as an efficient reductant to situ-reduce GO into rGO, and porous β-Ga 2 O 3 NWs can further attach on the surface of as-reduced rGO through a strong coupling forces between the β-Ga 2 O 3 NWs and rGO. The photocatalytic performance of the hybrids can be obviously improved (about 74%) for the decomposition of methylene blue (MB) solution after coupling with 1 wt% rGO compared with the pure β-Ga 2 O 3 NWs. The enhanced photocatalytic activity can be attributed to the synergistic effect of extended optical absorption band, the enrichment of MB molecular on the rGO and the valid inhibition of recombination of photo-generated electron–hole pairs induced by the strong coupling interaction between rGO nanosheets and porous β-Ga 2 O 3 NWs

  20. Auger Recombination in III-Nitride Nanowires and Its Effect on Nanowire Light-Emitting Diode Characteristics

    KAUST Repository

    Guo, Wei; Zhang, Meng; Bhattacharya, Pallab; Heo, Junseok

    2011-01-01

    We have measured the Auger recombination coefficients in defect-free InGaN nanowires (NW) and InGaN/GaN dot-in-nanowire (DNW) samples grown on (001) silicon by plasma-assisted molecular beam epitaxy. The nanowires have a density of ∼1×1011 cm-2 and exhibit photoluminescence emission peak at λ ∼ 500 nm. The Auger coefficients as a function of excitation power have been derived from excitation dependent and time-resolved photoluminescence measurements over a wide range of optical excitation power density. The values of C0, defined as the Auger coefficient at low excitation, are 6.1 × 10-32 and 4.1×10-33 cm6·s-1 in the NW and DNW samples, respectively, which are in reasonably good agreement with theoretical predictions for InGaN alloy semiconductors. Light-emitting diodes made with the NW and DNW samples exhibit no efficiency droop up to an injection current density of 400 A/cm 2. © 2011 American Chemical Society.

  1. Auger Recombination in III-Nitride Nanowires and Its Effect on Nanowire Light-Emitting Diode Characteristics

    KAUST Repository

    Guo, Wei

    2011-04-13

    We have measured the Auger recombination coefficients in defect-free InGaN nanowires (NW) and InGaN/GaN dot-in-nanowire (DNW) samples grown on (001) silicon by plasma-assisted molecular beam epitaxy. The nanowires have a density of ∼1×1011 cm-2 and exhibit photoluminescence emission peak at λ ∼ 500 nm. The Auger coefficients as a function of excitation power have been derived from excitation dependent and time-resolved photoluminescence measurements over a wide range of optical excitation power density. The values of C0, defined as the Auger coefficient at low excitation, are 6.1 × 10-32 and 4.1×10-33 cm6·s-1 in the NW and DNW samples, respectively, which are in reasonably good agreement with theoretical predictions for InGaN alloy semiconductors. Light-emitting diodes made with the NW and DNW samples exhibit no efficiency droop up to an injection current density of 400 A/cm 2. © 2011 American Chemical Society.

  2. Formation of stacking faults and the screw dislocation-driven growth: a case study of aluminum nitride nanowires.

    Science.gov (United States)

    Meng, Fei; Estruga, Marc; Forticaux, Audrey; Morin, Stephen A; Wu, Qiang; Hu, Zheng; Jin, Song

    2013-12-23

    Stacking faults are an important class of crystal defects commonly observed in nanostructures of close packed crystal structures. They can bridge the transition between hexagonal wurtzite (WZ) and cubic zinc blende (ZB) phases, with the most known example represented by the "nanowire (NW) twinning superlattice". Understanding the formation mechanisms of stacking faults is crucial to better control them and thus enhance the capability of tailoring physical properties of nanomaterials through defect engineering. Here we provide a different perspective to the formation of stacking faults associated with the screw dislocation-driven growth mechanism of nanomaterials. With the use of NWs of WZ aluminum nitride (AlN) grown by a high-temperature nitridation method as the model system, dislocation-driven growth was first confirmed by transmission electron microscopy (TEM). Meanwhile numerous stacking faults and associated partial dislocations were also observed and identified to be the Type I stacking faults and the Frank partial dislocations, respectively, using high-resolution TEM. In contrast, AlN NWs obtained by rapid quenching after growth displayed no stacking faults or partial dislocations; instead many of them had voids that were associated with the dislocation-driven growth. On the basis of these observations, we suggest a formation mechanism of stacking faults that originate from dislocation voids during the cooling process in the syntheses. Similar stacking fault features were also observed in other NWs with WZ structure, such as cadmium sulfide (CdS) and zinc oxide (ZnO).

  3. Photoelectrochemical reduction of carbon dioxide using Ge doped GaN nanowire photoanodes

    Directory of Open Access Journals (Sweden)

    Yichen Wang

    2015-11-01

    Full Text Available We report on the direct conversion of carbon dioxide (CO2 in a photoelectrochemical cell consisting of germanium doped gallium nitride nanowire anode and copper (Cu cathode. Various products including methane (CH4, carbon monoxide (CO, and formic acid (HCOOH were observed under light illumination. A Faradaic efficiency of ∼10% was measured for HCOOH. Furthermore, this photoelectrochemical system showed enhanced stability for 6 h CO2 reduction reaction on low cost, large area Si substrates.

  4. The electronic properties of phosphorus-doped GaN nanowires from first-principle calculations

    International Nuclear Information System (INIS)

    Fu, Nannan; Li, Enling; Cui, Zhen; Ma, Deming; Wang, Wei; Zhang, Yulong; Song, Sha; Lin, Jie

    2014-01-01

    Highlights: • The P impurities tend to enrich at the surface of GaN nanowires. • The lattice parameters of GaN nanowires are changed by the P impurity. • Donor impurity level appears when the P impurity substitutes for the Ga atom. • The band gap decreases slightly when the P impurity substitutes for the N atom. - Abstract: The electronic properties of phosphorus-doped unsaturated and saturated gallium nitride (GaN) nanowires have been investigated from first-principles using the ultrasoft pseudopotential method. The results of these calculations indicate that the P impurities are enriched at the surface of gallium nitride nanowires, and that the structural symmetry of GaN nanowires is broken due to changes in the lattice parameters. When the P impurity substitutes for the Ga atom, the width of band gap increases at the Γ point, a donor impurity level appears in the band gap, and the P impurity and adjacent N atoms exists covalent interaction. Moreover, when the P impurity substitutes for the N atom, the width of the band gap decreases slightly at the Γ point, there is no obvious impurity level in the band gap, and P–Ga covalent bonds are formed, including those composed of ionic bonds. These conclusions indicate that the incorporation of P impurities can improve the field emission performance of GaN nanowires, which is consistent with the experimental results

  5. The electronic properties of phosphorus-doped GaN nanowires from first-principle calculations

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Nannan; Li, Enling, E-mail: Lienling@xaut.edu.cn; Cui, Zhen; Ma, Deming; Wang, Wei; Zhang, Yulong; Song, Sha; Lin, Jie

    2014-05-01

    Highlights: • The P impurities tend to enrich at the surface of GaN nanowires. • The lattice parameters of GaN nanowires are changed by the P impurity. • Donor impurity level appears when the P impurity substitutes for the Ga atom. • The band gap decreases slightly when the P impurity substitutes for the N atom. - Abstract: The electronic properties of phosphorus-doped unsaturated and saturated gallium nitride (GaN) nanowires have been investigated from first-principles using the ultrasoft pseudopotential method. The results of these calculations indicate that the P impurities are enriched at the surface of gallium nitride nanowires, and that the structural symmetry of GaN nanowires is broken due to changes in the lattice parameters. When the P impurity substitutes for the Ga atom, the width of band gap increases at the Γ point, a donor impurity level appears in the band gap, and the P impurity and adjacent N atoms exists covalent interaction. Moreover, when the P impurity substitutes for the N atom, the width of the band gap decreases slightly at the Γ point, there is no obvious impurity level in the band gap, and P–Ga covalent bonds are formed, including those composed of ionic bonds. These conclusions indicate that the incorporation of P impurities can improve the field emission performance of GaN nanowires, which is consistent with the experimental results.

  6. Focused ion beam patterning to dielectrophoretically assemble single nanowire based devices

    International Nuclear Information System (INIS)

    La Ferrara, V; Massera, E; Francia, G Di; Alfano, B

    2010-01-01

    Direct-write processing is increasingly taking place in nanodevice fabrication. In this work, Focused Ion Beam (FIB), a powerful tool in maskless micromachining, is used for electrode patterning onto a silicon/silicon nitride substrate. Then a single palladium nanowire is assembled between electrodes by means of dielectrophoresis (DEP). The nanowire morphology depends on the electrode pattern when DEP conditions are fixed. FIB/DEP combination overcomes the problem of nanowire electrical contamination due to gallium ion bombardment and the as-grown nanowire retains its basic electrical properties. Single nanowire based devices have been fabricated with this novel approach and have been tested as hydrogen sensors, confirming the reliability of this technology.

  7. Direct Growth of III-Nitride Nanowire-Based Yellow Light-Emitting Diode on Amorphous Quartz Using Thin Ti Interlayer

    KAUST Repository

    Prabaswara, Aditya

    2018-02-06

    Consumer electronics have increasingly relied on ultra-thin glass screen due to its transparency, scalability, and cost. In particular, display technology relies on integrating light-emitting diodes with display panel as a source for backlighting. In this study, we undertook the challenge of integrating light emitters onto amorphous quartz by demonstrating the direct growth and fabrication of a III-nitride nanowire-based light-emitting diode. The proof-of-concept device exhibits a low turn-on voltage of 2.6 V, on an amorphous quartz substrate. We achieved ~ 40% transparency across the visible wavelength while maintaining electrical conductivity by employing a TiN/Ti interlayer on quartz as a translucent conducting layer. The nanowire-on-quartz LED emits a broad linewidth spectrum of light centered at true yellow color (~ 590 nm), an important wavelength bridging the green-gap in solid-state lighting technology, with significantly less strain and dislocations compared to conventional planar quantum well nitride structures. Our endeavor highlighted the feasibility of fabricating III-nitride optoelectronic device on a scalable amorphous substrate through facile growth and fabrication steps. For practical demonstration, we demonstrated tunable correlated color temperature white light, leveraging on the broadly tunable nanowire spectral characteristics across red-amber-yellow color regime.

  8. 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.

  9. 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.

  10. Plasma nitriding induced growth of Pt-nanowire arrays as high performance electrocatalysts for fuel cells

    NARCIS (Netherlands)

    Du, S.; Lin, K.; Malladi, S.R.K.; Lu, Y.; Sun, S.; Xu, Q.; Steinberger-Wilckens, R.; Dong, H.

    2014-01-01

    In this work, we demonstrate an innovative approach, combing a novel active screen plasma (ASP) technique with green chemical synthesis, for a direct fabrication of uniform Pt nanowire arrays on large-area supports. The ASP treatment enables in-situ N-doping and surface modification to the support

  11. Plasma nitriding induced growth of Pt-nanowire arrays as high performance electrocatalysts for fuel cells

    Science.gov (United States)

    Du, Shangfeng; Lin, Kaijie; Malladi, Sairam K.; Lu, Yaxiang; Sun, Shuhui; Xu, Qiang; Steinberger-Wilckens, Robert; Dong, Hanshan

    2014-09-01

    In this work, we demonstrate an innovative approach, combing a novel active screen plasma (ASP) technique with green chemical synthesis, for a direct fabrication of uniform Pt nanowire arrays on large-area supports. The ASP treatment enables in-situ N-doping and surface modification to the support surface, significantly promoting the uniform growth of tiny Pt nuclei which directs the growth of ultrathin single-crystal Pt nanowire (2.5-3 nm in diameter) arrays, forming a three-dimensional (3D) nano-architecture. Pt nanowire arrays in-situ grown on the large-area gas diffusion layer (GDL) (5 cm2) can be directly used as the catalyst electrode in fuel cells. The unique design brings in an extremely thin electrocatalyst layer, facilitating the charge transfer and mass transfer properties, leading to over two times higher power density than the conventional Pt nanoparticle catalyst electrode in real fuel cell environment. Due to the similar challenges faced with other nanostructures and the high availability of ASP for other material surfaces, this work will provide valuable insights and guidance towards the development of other new nano-architectures for various practical applications.

  12. Investigation into the use of molecular hydrogen on the growth of gallium nitride via metal-organic molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Billingsley, Daniel; Pritchett, David; Henderson, Walter; Carver, Alexander G.; Burnham, Shawn D.; Doolittle, W.A. [Georgia Institute of Technology, School of Electrical and Computer Engineering, 777 Atlantic Dr., Atlanta, GA 30332 (United States)

    2008-07-01

    Molecular hydrogen (H{sub 2}) has been investigated as a means to improve ammonia nitridation efficiency and attempts to reduce carbon contamination in ammonia-based metal-organic molecular beam epitaxy (MOMBE). A 30% improvement in crystalline quality, inferred from XRD, as well as an increase in subsequent GaN bulk growth rate was observed when bare sapphire was subject to H{sub 2} annealing before nitridation. However, the use of H{sub 2} during GaN homoepitaxy on GaN templates resulted in increased carbon contamination and decreased growth rate of GaN. The results demonstrate promise and proper uses of H{sub 2} during GaN growth under certain conditions. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. 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.

  14. Performance analysis of nanodisk and core/shell/shell-nanowire type III-Nitride heterojunction solar cell for efficient energy harvesting

    Science.gov (United States)

    Routray, S. R.; Lenka, T. R.

    2017-11-01

    Now-a-days III-Nitride nanowires with axial (nanodisk) and radial (core/shell/shell-nanowire) junctions are two unique and potential methods for solar energy harvesting adopted by worldwide researchers. In this paper, polarization behavior of GaN/InGaN/GaN junction and its effect on carrier dynamics of nanodisk and CSS-nanowire type solar cells are intensively studied and compared with its planar counterpart by numerical simulations using commercially available Victory TCAD. It is observed that CSS-NW with hexagonal geometrical shapes are robust to detrimental impact of polarization charges and could be good enough to accelerate carrier collection efficiency as compared to nanodisk and planar solar cells. This numerical study provides an innovative aspect of fundamental device physics with respect to polarization charges in CSS-NW and nanodisk type junction towards photovoltaic applications. The internal quantum efficiencies (IQE) are also discussed to evaluate carrier collection mechanisms and recombination losses in each type of junctions of solar cell. Finally, it is interesting to observe a maximum conversion efficiency of 6.46% with 91.6% fill factor from n-GaN/i-In0.1Ga0.9N/p-GaN CSS-nanowire solar cell with an optimized thickness of 180 nm InGaN layer under one Sun AM1.5 illumination.

  15. The sensitivity of the electron transport within bulk zinc-blende gallium nitride to variations in the crystal temperature, the doping concentration, and the non-parabolicity coefficient associated with the lowest energy conduction band valley

    Energy Technology Data Exchange (ETDEWEB)

    Siddiqua, Poppy; O' Leary, Stephen K., E-mail: stephen.oleary@ubc.ca [School of Engineering, The University of British Columbia, 3333 University Way, Kelowna, British Columbia V1V 1V7 (Canada)

    2016-09-07

    Within the framework of a semi-classical three-valley Monte Carlo simulation approach, we analyze the steady-state and transient electron transport that occurs within bulk zinc-blende gallium nitride. In particular, we examine how the steady-state and transient electron transport that occurs within this material changes in response to variations in the crystal temperature, the doping concentration, and the non-parabolicity coefficient associated with the lowest energy conduction band valley. These results are then contrasted with those corresponding to a number of other compound semiconductors of interest.

  16. Nondestructive mapping of chemical composition and structural qualities of group III-nitride nanowires using submicron beam synchrotron-based X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Bonanno, P.L., E-mail: plb2@njit.edu [Georgia Institute of Technology/GTL, UMI 2958 Georgia Tech-CNRS, 57070 Metz (France); Gautier, S. [LMOPS + UMI: Laboratoire Matériaux Optiques, Photonique et micro-nano Systèmes, UMR CNRS 7132, Université de Metz et SUPELEC, 2 rue E. Belin, 57070 Metz, France, UMI 2958 Georgia Tech-CNRS, 57070 Metz (France); Gmili, Y.El.; Moudakir, T. [UMI 2958 Georgia Tech-CNRS, 57070 Metz (France); Sirenko, A.A. [Department of Physics, New Jersey Institute of Technology, Newark, NJ 07102 (United States); Kazimirov, A. [Cornell High Energy Synchrotron Source (CHESS), Cornell University, Ithaca, NY 14853 (United States); Cai, Z.-H. [Advanced Photon Source, 9700 S. Cass Avenue, Argonne, IL 60439 (United States); Martin, J. [LMOPS + UMI: Laboratoire Matériaux Optiques, Photonique et micro-nano Systèmes, UMR CNRS 7132, Université de Metz et SUPELEC, 2 rue E. Belin, 57070 Metz, France, UMI 2958 Georgia Tech-CNRS, 57070 Metz (France); Goh, W.H. [Georgia Institute of Technology/GTL, UMI 2958 Georgia Tech-CNRS, 57070 Metz (France); Martinez, A.; Ramdane, A.; Le Gratiet, L. [Laboratoire de Photonique et de Nanostructures, UPR CNRS 20, Route de Nozay, 91460 Marcoussis (France); Maloufi, N. [Laboratoire d' Etude des Textures et Application aux Matériaux UMR CNRS 7078 Ile du Saulcy 57045 METZ cedex 1 (France); Assouar, M.B. [Laboratoire de Physique des Milieux Ionisés et Applications, Nancy University, CNRS, BP 239, F-54506 Vandoeuvre-lès-Nancy Cédex (France); Ougazzaden, A. [Georgia Institute of Technology/GTL, UMI 2958 Georgia Tech-CNRS, 57070 Metz (France)

    2013-08-31

    Submicron beam synchrotron-based X-ray diffraction (XRD) techniques have been developed and used to accurately and nondestructively map chemical composition and material quality of selectively grown group III-nitride nanowires. GaN, AlGaN, and InGaN multi-quantum-well nanowires have been selectively grown on lattice matched and mismatched substrates, and the challenges associated with obtaining and interpreting submicron beam XRD results are addressed and solved. Nanoscale cathodoluminescence is used to examine exciton behavior, and energy-dispersive X-ray spectroscopy is used to verify chemical composition. Scanning transmission electron microscopy is later used to paint a more complete picture. The advantages of submicron beam XRD over other techniques are discussed in the context of this challenging material system. - Highlights: ► We used nano selective area growth to create nanowires of GaN, AlGaN and InGaN/GaN. ► We characterized them by synchrotron-based submicron beam X-ray diffraction (XRD). ► This technique accurately determined chemical and crystallographic properties. ► Challenges of XRD are addressed in the context of this challenging material system. ► Advantages of XRD over other characterization methods are discussed.

  17. Optical and field emission properties of layer-structure GaN nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Zhen [Science School, Xi’an University of Technology, Xi’an 710048 (China); School of automation and Information Engineering, Xi’an University of Technology, Xi’an 710048 (China); Li, Enling, E-mail: Lienling@xaut.edu.cn [Science School, Xi’an University of Technology, Xi’an 710048 (China); Shi, Wei; Ma, Deming [Science School, Xi’an University of Technology, Xi’an 710048 (China)

    2014-08-15

    Highlights: • The layer-structure GaN nanowires with hexagonal-shaped cross-sections are produced via a process based on the CVD method. • The diameter of the layer-structure GaN nanowire gradually decreases from ∼500 nm to ∼200 nm along the wire axis. • The layer-structure GaN nanowire film possesses good field emission property. - Abstract: A layer-structure gallium nitride (GaN) nanowires, grown on Pt-coated n-type Si (1 1 1) substrate, have been synthesized using chemical vapor deposition (CVD). The results show: (1) SEM indicates that the geometry structure is layer-structure. HRTEM indicates that GaN nanowire’s preferential growth direction is along [0 0 1] direction. (2) The room temperature PL emission spectrum of the layer-structure GaN nanowires has a peak at 375 nm, which proves that GaN nanowires have potential application in light-emitting nano-devices. (3) Field-emission measurements show that the layer-structure GaN nanowires film has a low turn-on field of 4.39 V/μm (at room temperature), which is sufficient for electron emission devices, field emission displays and vacuum nano-electronic devices. The growth mechanism for GaN nanowires has also been discussed briefly.

  18. 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

  19. Enhancing the Light-Extraction Efficiency of AlGaN Nanowires Ultraviolet Light-Emitting Diode by using Nitride/Air Distributed Bragg Reflector Nanogratings

    KAUST Repository

    Alias, Mohd Sharizal; Janjua, Bilal; Zhao, Chao; Priante, Davide; Alhamoud, Abdullah A.; Tangi, Malleswararao; Alanazi, Lafi M.; Alatawi, Abdullah A.; Albadri, Abdulrahman M.; Alyamani, Ahmed Y.; Ng, Tien Khee; Ooi, Boon S.

    2017-01-01

    The performance and efficiency of AlGaN ultraviolet light-emitting diodes have been limited by the extremely low light-extraction efficiency (LEE) due to the intrinsic material properties of AlGaN. Here, to enhance the LEE of the device, we demonstrate an AlGaN nanowires light-emitting diode (NWs-LED) integrated with nitride/air Distributed Bragg Reflector (DBR) nanogratings. Compared to a control device (only mesa), the AlGaN NWs-LED with the nitride/air DBR nanogratings exhibit enhancement in the light output power and external quantum efficiency (EQE) by a factor of ∼1.67. The higher light output power and EQE are attributed mainly to the multiple reflectances laterally for the transverse magnetic (TM)-polarized light and scattering introduced by the nanogratings. To further understand the LEE enhancement, the electrical field distribution, extraction ratio and polar pattern of the AlGaN NWs-LED with and without the nitride/air DBR nanogratings were analyzed using the finite-difference-time-domain method. It was observed that the TM-field emission was confined and scattered upward whereas the polar pattern was intensified for the AlGaN NWs-LED with the nanogratings. Our approach to enhance the LEE via the nitride/air DBR nanogratings can provide a promising route for increasing the efficiency of AlGaN-based LEDs, also, to functioning as facet mirror for AlGaN-based laser diodes.

  20. Enhancing the Light-Extraction Efficiency of AlGaN Nanowires Ultraviolet Light-Emitting Diode by using Nitride/Air Distributed Bragg Reflector Nanogratings

    KAUST Repository

    Alias, Mohd Sharizal

    2017-09-11

    The performance and efficiency of AlGaN ultraviolet light-emitting diodes have been limited by the extremely low light-extraction efficiency (LEE) due to the intrinsic material properties of AlGaN. Here, to enhance the LEE of the device, we demonstrate an AlGaN nanowires light-emitting diode (NWs-LED) integrated with nitride/air Distributed Bragg Reflector (DBR) nanogratings. Compared to a control device (only mesa), the AlGaN NWs-LED with the nitride/air DBR nanogratings exhibit enhancement in the light output power and external quantum efficiency (EQE) by a factor of ∼1.67. The higher light output power and EQE are attributed mainly to the multiple reflectances laterally for the transverse magnetic (TM)-polarized light and scattering introduced by the nanogratings. To further understand the LEE enhancement, the electrical field distribution, extraction ratio and polar pattern of the AlGaN NWs-LED with and without the nitride/air DBR nanogratings were analyzed using the finite-difference-time-domain method. It was observed that the TM-field emission was confined and scattered upward whereas the polar pattern was intensified for the AlGaN NWs-LED with the nanogratings. Our approach to enhance the LEE via the nitride/air DBR nanogratings can provide a promising route for increasing the efficiency of AlGaN-based LEDs, also, to functioning as facet mirror for AlGaN-based laser diodes.

  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. Controlled dielectrophoretic nanowire self-assembly using atomic layer deposition and suspended microfabricated electrodes

    International Nuclear Information System (INIS)

    Baca, Alicia I; Brown, Joseph J; Bright, Victor M; Bertness, Kris A

    2012-01-01

    Effects of design and materials on the dielectrophoretic self-assembly of individual gallium nitride nanowires (GaN NWs) onto microfabricated electrodes have been experimentally investigated. The use of TiO 2 surface coating generated by atomic layer deposition (ALD) improves dielectrophoretic assembly yield of individual GaN nanowires on microfabricated structures by as much as 67%. With a titanium dioxide coating, individual nanowires were placed across suspended electrode pairs in 46% of tests (147 out of 320 total), versus 28% of tests (88 out of 320 total tests) that used uncoated GaN NWs. An additional result from these tests was that suspending the electrodes 2.75 μm above the substrate corresponded with up to 15.8% improvement in overall assembly yield over that of electrodes fabricated directly on the substrate. (paper)

  3. Synthesis and cathodoluminescence of Sb/P co-doped GaN nanowires

    International Nuclear Information System (INIS)

    Wang, Zaien; Liu, Baodan; Yuan, Fang; Hu, Tao; Zhang, Guifeng; Dierre, Benjamin; Hirosaki, Naoto; Sekiguchi, Takashi; Jiang, Xin

    2014-01-01

    Sb/P co-doped Gallium Nitride (GaN) nanowires were synthesized via a simple chemical vapor deposition (CVD) process by heating Ga 2 O 3 and Sb powders in NH 3 atmosphere. Scanning electron microscope (SEM), X-ray diffraction (XRD), transmission electron microscope (TEM) and energy dispersive X-ray spectroscopy (EDS) measurements confirmed the as-synthesized products were Sb/P co-doped GaN nanowires with rough morphology and hexagonal wurtzite structure. Room temperature cathodoluminescence (CL) demonstrated that an obvious band shift of GaN nanowires can be observed due to Sb/P co-doping. Possible explanation for the growth and luminescence mechanism of Sb/P co-doped GaN nanowires was discussed. Highlight: • Sb/P co-doped GaN nanowires were synthesized through a well-designed multi-channel chemical vapor deposition (CVD) process. • Sb/P co-doping leads to the crystallinity deterioration of GaN nanowires. • Sb/P co-doping caused the red-shift of GaN nanowires band-gap in UV range. • Compared with Sb doping, P atoms are more easy to incorporate into the GaN lattice

  4. III-nitride disk-in-nanowire 1.2 μm monolithic diode laser on (001)silicon

    KAUST Repository

    Hazari, Arnab; Aiello, Anthony; Ng, Tien Khee; Ooi, Boon S.; Bhattacharya, Pallab

    2015-01-01

    recombination lifetime of 1.84 ns in the disks is measured by time-resolved luminescence measurements. Edge-emitting nanowire lasers have been fabricated and characterized. Measured values of Jth, T0, and dg/dn in these devices are 1.24 kA/cm2, 242 K, and 5

  5. Heteroepitaxial Patterned Growth of Vertically Aligned and Periodically Distributed ZnO Nanowires on GaN Using Laser Interference Ablation

    KAUST Repository

    Yuan, Dajun

    2010-08-23

    A simple two-step method of fabricating vertically aligned and periodically distributed ZnO nanowires on gallium nitride (GaN) substrates is described. The method combines laser interference ablation (LIA) and low temperature hydrothermal decomposition. The ZnO nanowires grow heteroepitaxially on unablated regions of GaN over areas spanning 1 cm2, with a high degree of control over size, orientation, uniformity, and periodicity. High resolution transmission electron microscopy and scanning electron microscopy are utilized to study the structural characteristics of the LIA-patterned GaN substrate in detail. These studies reveal the possible mechanism for the preferential, site-selective growth of the ZnO nanowires. The method demonstrates high application potential for wafer-scale integration into sensor arrays, piezoelectric devices, and optoelectronic devices. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Title: Using Alignment and 2D Network Simulations to Study Charge Transport Through Doped ZnO Nanowire Thin Film Electrodes

    KAUST Repository

    Phadke, Sujay; Lee, Jung-Yong; West, Jack; Peumans, Peter; Salleo, Alberto

    2011-01-01

    of magnitude lower than the single nanowire resistance. Simulations suggest that the conductivity of such thin film devices could be further enhanced by using longer nanowires. Solution processed Gallium doped ZnO nanowires are aligned on substrates using

  7. Preferential adsorption of gallium on GaAs(111)B surfaces during the initial growth of Au-assisted GaAs nanowires

    International Nuclear Information System (INIS)

    Shu Haibo; Chen Xiaoshuang; Ding Zongling; Dong Ruibin; Lu Wei

    2010-01-01

    The mechanism of the preferential adsorption of Ga on GaAs(111)B surfaces during the initial growth of Au-assisted GaAs nanowires is studied by using first-principles calculations within density functional theory. The calculated results show that Au preadsorption on GaAs(111)B surface significantly enhances the stability of the Ga adatom in comparison with the adsorption of Ga on clean GaAs(111)B surface. The stabilization of the Ga adatom is due to charge transfers from the Ga 4p and 4s states to the Au 6s and As 4p states. The number of Ga adatoms stabilized on GaAs(111)B surfaces depends on the size of surface Au cluster. The reason is that Au acted as an electron acceptor on GaAs(111)B surface assists the charge transfer of Ga adatoms for filling the partial unoccupied bands of GaAs(111)B surface. Our results are helpful to understand the growth of Au-assisted GaAs nanowires.

  8. Highly aligned vertical GaN nanowires using submonolayer metal catalysts

    Science.gov (United States)

    Wang, George T [Albuquerque, NM; Li, Qiming [Albuquerque, NM; Creighton, J Randall [Albuquerque, NM

    2010-06-29

    A method for forming vertically oriented, crystallographically aligned nanowires (nanocolumns) using monolayer or submonolayer quantities of metal atoms to form uniformly sized metal islands that serve as catalysts for MOCVD growth of Group III nitride nanowires.

  9. Controlled growth of single nanowires within a supported alumina template

    DEFF Research Database (Denmark)

    Vlad, A.; Mátéfi-Tempfli, M.; Faniel, S.

    2006-01-01

    A simple technique for fabricating single nanowires with well-defined position is presented. The process implies the use of a silicon nitride mask for selective electrochemical growth of the nanowires in a porous alumina template. We show that this method allows the realization of complex nanowire...

  10. 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 materials – gallium 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

  11. Small signal modulation characteristics of red-emitting (λ = 610 nm) III-nitride nanowire array lasers on (001) silicon

    KAUST Repository

    Jahangir, Shafat; Frost, Thomas; Hazari, Arnab; Yan, Lifan; Stark, Ethan; LaMountain, Trevor; Millunchick, Joanna M.; Ooi, Boon S.; Bhattacharya, Pallab

    2015-01-01

    The small signal modulation characteristics of an InGaN/GaN nanowire array edge- emitting laser on (001) silicon are reported. The emission wavelength is 610 nm. Lattice matched InAlN cladding layers were incorporated in the laser heterostructure for better mode confinement. The suitability of the nanowire lasers for use in plastic fiber communication systems with direct modulation is demonstrated through their modulation bandwidth of f-3dB,max = 3.1 GHz, very low values of chirp (0.8 Å) and α-parameter, and large differential gain (3.1 × 10-17 cm2).

  12. Small signal modulation characteristics of red-emitting (λ = 610 nm) III-nitride nanowire array lasers on (001) silicon

    KAUST Repository

    Jahangir, Shafat

    2015-02-16

    The small signal modulation characteristics of an InGaN/GaN nanowire array edge- emitting laser on (001) silicon are reported. The emission wavelength is 610 nm. Lattice matched InAlN cladding layers were incorporated in the laser heterostructure for better mode confinement. The suitability of the nanowire lasers for use in plastic fiber communication systems with direct modulation is demonstrated through their modulation bandwidth of f-3dB,max = 3.1 GHz, very low values of chirp (0.8 Å) and α-parameter, and large differential gain (3.1 × 10-17 cm2).

  13. Direct Growth of III-Nitride Nanowire-Based Yellow Light-Emitting Diode on Amorphous Quartz Using Thin Ti Interlayer

    KAUST Repository

    Prabaswara, Aditya; Min, Jung-Wook; Zhao, Chao; Janjua, Bilal; Zhang, Daliang; Albadri, Abdulrahman M.; Alyamani, Ahmed Y.; Ng, Tien Khee; Ooi, Boon S.

    2018-01-01

    .6 V, on an amorphous quartz substrate. We achieved ~ 40% transparency across the visible wavelength while maintaining electrical conductivity by employing a TiN/Ti interlayer on quartz as a translucent conducting layer. The nanowire-on-quartz LED emits

  14. Microbridge tests on gallium nitride thin films

    International Nuclear Information System (INIS)

    Huang, Hai-You; Li, Zhi-Ying; Lu, Jun-Yong; Wang, Zhi-Jia; Zhang, Tong-Yi; Wang, Chong-Shun; Lau, Kei-May; Chen, Kevin Jing

    2009-01-01

    In this work, we develop further the microbridge testing method by deriving a closed formula of deflection versus load, which is applied at an arbitrary position on the microbridge beam. Testing a single beam at various positions allows us to characterize simultaneouslyYoung's modulus and residual stress of the beam. The developed method was then used to characterize the mechanical properties of GaN thin films on patterned-Si (1 1 1) substrates grown by metal organic chemical vapor deposition (MOCVD). The microbridge samples were fabricated by using the microelectromechanical fabrication technique and tested with a nanoindentation system. Young's modulus and residual stress of the GaN films were determined to be 287 ± 190 GPa and 851 ± 155 MPa, respectively. In addition, alternative measurements of the residual stress, Young's modulus and hardness of the GaN films, were conducted with micro-Raman spectroscopy and the nanoindentation test, yielding the corresponding values of 847 ± 46 MPa, 269.0 ± 7.0 GPa and 17.8 ± 1.1 GPa

  15. Electrical and optoelectronic properties of gallium nitride

    International Nuclear Information System (INIS)

    Flannery, Lorraine Barbara

    2002-01-01

    This thesis describes novel research carried out on two related topics, the electrical properties of n and p-type GaN and the use of GaN in the fabrication of UV photodetectors. The electrical properties of GaN were assessed mainly by Hall effect measurements, which play a crucial role in the determination of the concentration of shallow electrically active impurities and defects. Most of the Hall effect measurements were carried out on Si and unintentionally doped GaN layers grown on sapphire substrates using a Varian Modular Gen II MBE machine equipped with an Oxford Applied Research CARS25 RF or HD25 RF nitrogen source to supply the active nitrogen. It was necessary to consider parallel conduction in two channels to interpret the temperature dependent Hall effect characteristics of the highest purity layers. Parallel conduction was found to influence the transport properties of these layers even at room temperature and give rise to an increased compensation ratio. The impurity band was found to be located at 23 ± 7 meV below the conduction band in layers containing impurity densities less than 3.8 x 10 18 cm -3 but was found to broaden with increasing impurity content, reducing the activation energy to 5 ± 3 meV in layers containing impurity densities greater than ∼4.5 x 10 18 cm -3 . Doping studies were conducted on Mg doped GaN layers grown on sapphire substrates using the MBE and MOVPE growth techniques. The effect of the growth parameters on Mg incorporation was determined using SIMS and Hall effect measurements for the MBE samples sets. P-type conductivity was successfully demonstrated in Mg doped layers grown under nitrogen rich conditions with layer thickness greater than 0.9 μm using the CARS25 RF source. The highest hole density, p H and mobility, μ H of 9.6 x 10 17 cm -3 and 5.4 cm 2 V -1 s -1 respectively were recorded in the thickest layer grown (1.56 μm). P-type doping studies were also carried out on Mg doped GaN layers grown on GaAs (111)B 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)

  16. Growth process for gallium nitride porous nanorods

    Science.gov (United States)

    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.

  17. Selective-area growth of GaN nanowires on SiO{sub 2}-masked Si (111) substrates by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Kruse, J. E.; Doundoulakis, G. [Department of Physics, University of Crete, P. O. Box 2208, 71003 Heraklion (Greece); Institute of Electronic Structure and Laser, Foundation for Research and Technology–Hellas, N. Plastira 100, 70013 Heraklion (Greece); Lymperakis, L. [Max-Planck-Institut für Eisenforschung, Max-Planck-Straße 1, 40237 Düsseldorf (Germany); Eftychis, S.; Georgakilas, A., E-mail: alexandr@physics.uoc.gr [Department of Physics, University of Crete, P. O. Box 2208, 71003 Heraklion (Greece); Adikimenakis, A.; Tsagaraki, K.; Androulidaki, M.; Konstantinidis, G. [Institute of Electronic Structure and Laser, Foundation for Research and Technology–Hellas, N. Plastira 100, 70013 Heraklion (Greece); Olziersky, A.; Dimitrakis, P.; Ioannou-Sougleridis, V.; Normand, P. [Institute of Nanoscience and Nanotechnology, NCSR Demokritos, Patriarchou Grigoriou and Neapoleos 27, 15310 Aghia Paraskevi, Athens (Greece); Koukoula, T.; Kehagias, Th.; Komninou, Ph. [Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece)

    2016-06-14

    We analyze a method to selectively grow straight, vertical gallium nitride nanowires by plasma-assisted molecular beam epitaxy (MBE) at sites specified by a silicon oxide mask, which is thermally grown on silicon (111) substrates and patterned by electron-beam lithography and reactive-ion etching. The investigated method requires only one single molecular beam epitaxy MBE growth process, i.e., the SiO{sub 2} mask is formed on silicon instead of on a previously grown GaN or AlN buffer layer. We present a systematic and analytical study involving various mask patterns, characterization by scanning electron microscopy, transmission electron microscopy, and photoluminescence spectroscopy, as well as numerical simulations, to evaluate how the dimensions (window diameter and spacing) of the mask affect the distribution of the nanowires, their morphology, and alignment, as well as their photonic properties. Capabilities and limitations for this method of selective-area growth of nanowires have been identified. A window diameter less than 50 nm and a window spacing larger than 500 nm can provide single nanowire nucleation in nearly all mask windows. The results are consistent with a Ga diffusion length on the silicon dioxide surface in the order of approximately 1 μm.

  18. Electrically Injected UV-Visible Nanowire Lasers

    Energy Technology Data Exchange (ETDEWEB)

    Wang, George T.; Li, Changyi; Li, Qiming; Liu, Sheng; Wright, Jeremy Benjamin; Brener, Igal; Luk, Ting -Shan; Chow, Weng W.; Leung, Benjamin; Figiel, Jeffrey J.; Koleske, Daniel D.; Lu, Tzu-Ming

    2015-09-01

    There is strong interest in minimizing the volume of lasers to enable ultracompact, low-power, coherent light sources. Nanowires represent an ideal candidate for such nanolasers as stand-alone optical cavities and gain media, and optically pumped nanowire lasing has been demonstrated in several semiconductor systems. Electrically injected nanowire lasers are needed to realize actual working devices but have been elusive due to limitations of current methods to address the requirement for nanowire device heterostructures with high material quality, controlled doping and geometry, low optical loss, and efficient carrier injection. In this project we proposed to demonstrate electrically injected single nanowire lasers emitting in the important UV to visible wavelengths. Our approach to simultaneously address these challenges is based on high quality III-nitride nanowire device heterostructures with precisely controlled geometries and strong gain and mode confinement to minimize lasing thresholds, enabled by a unique top-down nanowire fabrication technique.

  19. Wurtzite gallium phosphide has a direct-band gap

    NARCIS (Netherlands)

    Assali, S.; Zardo, I.; Plissard, S.; Verheijen, M.A.; Haverkort, J.E.M.; Bakkers, E.P.A.M.

    2013-01-01

    Gallium Phosphide (GaP) with the normal cubic crystal structure has an indirect band gap, which severely limits the emission efficiency. We report the fabrication of GaP nanowires with pure hexagonal crystal structure and demonstrate the direct nature of the band gap. We observe strong

  20. Highly selective GaN-nanowire/TiO2-nanocluster hybrid sensors for detection of benzene and related environment pollutants

    International Nuclear Information System (INIS)

    Aluri, Geetha S; Motayed, Abhishek; Davydov, Albert V; Oleshko, Vladimir P; Bertness, Kris A; Sanford, Norman A; Rao, Mulpuri V

    2011-01-01

    Nanowire-nanocluster hybrid chemical sensors were realized by functionalizing gallium nitride (GaN) nanowires (NWs) with titanium dioxide (TiO 2 ) nanoclusters for selectively sensing benzene and other related aromatic compounds. Hybrid sensor devices were developed by fabricating two-terminal devices using individual GaN NWs followed by the deposition of TiO 2 nanoclusters using RF magnetron sputtering. The sensor fabrication process employed standard microfabrication techniques. X-ray diffraction and high-resolution analytical transmission electron microscopy using energy-dispersive x-ray and electron energy-loss spectroscopies confirmed the presence of the anatase phase in TiO 2 clusters after post-deposition anneal at 700 deg. C. A change of current was observed for these hybrid sensors when exposed to the vapors of aromatic compounds (benzene, toluene, ethylbenzene, xylene and chlorobenzene mixed with air) under UV excitation, while they had no response to non-aromatic organic compounds such as methanol, ethanol, isopropanol, chloroform, acetone and 1,3-hexadiene. The sensitivity range for the noted aromatic compounds except chlorobenzene were from 1% down to 50 parts per billion (ppb) at room temperature. By combining the enhanced catalytic properties of the TiO 2 nanoclusters with the sensitive transduction capability of the nanowires, an ultra-sensitive and selective chemical sensing architecture is demonstrated. We have proposed a mechanism that could qualitatively explain the observed sensing behavior.

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

    KAUST Repository

    Ng, Tien Khee; Zhao, Chao; Priante, Davide; Ooi, Boon S.; Hussein, Mohamed Ebaid Abdrabou

    2018-01-01

    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.

  2. 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.

  3. Integration, gap formation, and sharpening of III-V heterostructure nanowires by selective etching

    DEFF Research Database (Denmark)

    Kallesoe, C.; Mølhave, Kristian; Larsen, K. F.

    2010-01-01

    Epitaxial growth of heterostructure nanowires allows for the definition of narrow sections with specific semiconductor composition. The authors demonstrate how postgrowth engineering of III-V heterostructure nanowires using selective etching can form gaps, sharpening of tips, and thin sections...... lithography is used for deposition of catalyst particles on trench sidewalls and the lateral growth of III-V nanowires is achieved from such catalysts. The selectivity of a bromine-based etch on gallium arsenide segments in gallium phosphide nanowires is examined, using a hydrochloride etch to remove the III...

  4. Technical assistance for development of thermally conductive nitride filler for epoxy molding compounds

    Energy Technology Data Exchange (ETDEWEB)

    Ryu, Ho Jin; Song, Kee Chan; Jung, In Ha

    2005-07-15

    Technical assistance was carried out to develop nitride filler for thermally conductive epoxy molding compounds. Carbothermal reduction method was used to fabricate silicon nitride powder from mixtures of silica and graphite powders. Microstructure and crystal structure were observed by using scanning electron microscopy and x-ray diffraction technique. Thermal properties of epoxy molding compounds containing silicon nitride were measured by using laser flash method. Fabrication process of silicon nitride nanowire was developed and was applied to a patent.

  5. Multi-spectral optical absorption in substrate-free nanowire arrays

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Junpeng; Chia, Andrew; Boulanger, Jonathan; LaPierre, Ray, E-mail: lapierr@mcmaster.ca [Department of Engineering Physics, McMaster University, 1280 Main St. West, Hamilton, Ontario L8S 4L7 (Canada); Dhindsa, Navneet; Khodadad, Iman; Saini, Simarjeet [Department of Electrical and Computer Engineering, University of Waterloo, 200 University Ave West, Waterloo, Ontario N2L 3G1 (Canada); Waterloo Institute of Nanotechnology, University of Waterloo, 200 University Ave West, Waterloo, Ontario N2L 3G1 (Canada)

    2014-09-22

    A method is presented of fabricating gallium arsenide (GaAs) nanowire arrays of controlled diameter and period by reactive ion etching of a GaAs substrate containing an indium gallium arsenide (InGaP) etch stop layer, allowing the precise nanowire length to be controlled. The substrate is subsequently removed by selective etching, using the same InGaP etch stop layer, to create a substrate-free GaAs nanowire array. The optical absorptance of the nanowire array was then directly measured without absorption from a substrate. We directly observe absorptance spectra that can be tuned by the nanowire diameter, as explained with rigorous coupled wave analysis. These results illustrate strong optical absorption suitable for nanowire-based solar cells and multi-spectral absorption for wavelength discriminating photodetectors. The solar-weighted absorptance above the bandgap of GaAs was 94% for a nanowire surface coverage of only 15%.

  6. 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.

  7. 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

  8. Luminescence Studies of Ion-Implanted Gallium Nitride and Aluminum Gallium Nitride

    Science.gov (United States)

    2003-03-01

    58: 1306 (1995). 15. Moxom, Jeremy. “Characterization of Mg doped GaN by positron annihilation spectroscopy .” Journal of Applied Physics, 92... semiconductors such as GaN and AlxGa1-xN became very popular for their applications on various devices. Therefore comprehensive and systematic luminescence...short wavelength optoelectronic applications that are beyond the range of present semiconductor devices. The AlGaN and GaN materials have these

  9. 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...

  10. 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...

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

    Science.gov (United States)

    2008-06-01

    potentials used in the discussion. ........... 41 15. Energy band diagram of an unpassivated HFET using Davinci showing the relative heights and...integration into a dose received in the material of interest. The tool used to perform these calculations is the TIGER Monte Carlo electron transport code [30...height and width of the second barrier a model of the HFETs was built in the Davinci modeling program [61]. The resulting energy band diagram is shown in

  12. Synthesis and characterization of straight and stacked-sheet AlN nanowires with high purity

    International Nuclear Information System (INIS)

    Lei, M.; Yang, H.; Li, P.G.; Tang, W.H.

    2008-01-01

    Large-scale AlN nanowires with hexagonal crystal structure were synthesized by the direct nitridation method at high temperatures. The experimental results indicate that these single-crystalline AlN nanowires have high purity and consist of straight and stacked-sheet nanowires. It is found that straight AlN nanowire grows along [1, 1, -2, 0] direction, whereas the stacked-sheet nanowire with hexagonal cross section is along [0 0 0 1] direction. It is thought that vapor-solid (VS) mechanism should be responsible for the growth of AlN nanowires

  13. Low Temperature Reactions for the Preparation of Group 13-15 Materials from Organo-gallium(I) and -indium(I) Compounds

    National Research Council Canada - National Science Library

    Beachley, O

    1997-01-01

    ...) at 175 deg C and of neopentylgallium(I) Ga(CH2CMe3)n with P4 at 350- 400 deg C and with NH3 at 460-480 deg C in sealed tubes provide routes to indium phosphide, gallium phosphide and hexagonal gallium nitride, respectively...

  14. Controlled surface diffusion in plasma-enhanced chemical vapor deposition of GaN nanowires

    International Nuclear Information System (INIS)

    Hou, W C; Hong, Franklin Chau-Nan

    2009-01-01

    This study investigates the growth of GaN nanowires by controlling the surface diffusion of Ga species on sapphire in a plasma-enhanced chemical vapor deposition (CVD) system. Under nitrogen-rich growth conditions, Ga has a tendency to adsorb on the substrate surface diffusing to nanowires to contribute to their growth. The significance of surface diffusion on the growth of nanowires is dependent on the environment of the nanowire on the substrate surface as well as the gas phase species and compositions. Under nitrogen-rich growth conditions, the growth rate is strongly dependent on the surface diffusion of gallium, but the addition of 5% hydrogen in nitrogen plasma instantly diminishes the surface diffusion effect. Gallium desorbs easily from the surface by reaction with hydrogen. On the other hand, under gallium-rich growth conditions, nanowire growth is shown to be dominated by the gas phase deposition, with negligible contribution from surface diffusion. This is the first study reporting the inhibition of surface diffusion effects by hydrogen addition, which can be useful in tailoring the growth and characteristics of nanowires. Without any evidence of direct deposition on the nanowire surface, gallium and nitrogen are shown to dissolve into the catalyst for growing the nanowires at 900 deg. C.

  15. Optical properties of nanowire metamaterials with gain

    DEFF Research Database (Denmark)

    Isidio de Lima, Joaquim Junior; Adam, Jost; Rego, Davi

    2016-01-01

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

  16. Hydride vapor phase epitaxy growth of GaN, InGaN, ScN, and ScAIN

    NARCIS (Netherlands)

    Bohnen, T.

    2010-01-01

    Chemical vapor deposition (CVD); hydride vapor phase epitaxy (HVPE); gallium nitride (GaN); indium gallium nitride (InGaN); scandium nitride (ScN); scandium aluminum nitride (ScAlN); semiconductors; thin films; nanowires; III nitrides; crystal growth - We studied the HVPE growth of different III

  17. 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

    family have (0001) interfaces which bear a surface charge σ0 that results from the polarizations of the two alloys at the interface...function of the Al content of the AlGaN barrier, as well as its thickness (Kocan, 2003; Lenka and Panda , 2011). In my dissertation, the surface...incorporation.” Applied Physics Letters, 71 (1997): 1359. Lenka, T. R., and Panda , A. K.. “Effect of structural parameters of 2DEG and C~V

  18. Flexible InGaN nanowire membranes for enhanced solar water splitting

    KAUST Repository

    Elafandy, Rami T.; Elafandy, Rami T.; Min, Jung-Wook; Zhao, Chao; Ng, Tien Khee; Ooi, Boon S.

    2018-01-01

    III-Nitride nanowires (NWs) have recently emerged as potential photoelectrodes for efficient solar hydrogen generation. While InGaN NWs epitaxy over silicon is required for high crystalline quality and economic production, it leads to the formation

  19. Direct Evidence of Mg Incorporation Pathway in Vapor-Liquid-Solid Grown p-type Nonpolar GaN Nanowires

    OpenAIRE

    Patsha, Avinash; Amirthapandian, S.; Pandian, Ramanathaswamy; Bera, S.; Bhattacharya, Anirban; Dhara, Sandip

    2015-01-01

    Doping of III-nitride based compound semiconductor nanowires is still a challenging issue to have a control over the dopant distribution in precise locations of the nanowire optoelectronic devices. Knowledge of the dopant incorporation and its pathways in nanowires for such devices is limited by the growth methods. We report the direct evidence of incorporation pathway for Mg dopants in p-type nonpolar GaN nanowires grown via vapour-liquid-solid (VLS) method in a chemical vapour deposition te...

  20. Organic Nanowires

    DEFF Research Database (Denmark)

    Balzer, Frank; Schiek, Manuela; Al-Shamery, Katharina

    Single crystalline nanowires from fluorescing organic molecules like para-phenylenes or thiophenes are supposed to become key elements in future integrated optoelectronic devices [1]. For a sophisticated design of devices based on nanowires the basic principles of the nanowire formation have...... atomic force microscopy and from polarized far-field optical microscopy for various prototypical molecules are reproduced by electrostatic and Monte Carlo calculations. Based on the crystal structure, predictions on the growth habit from other conjugated molecules become in reach....

  1. 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

  2. Platinum boride nanowires: Synthesis and characterization

    International Nuclear Information System (INIS)

    Ding Zhanhui; Qiu Lixia; Zhang Jian; Yao Bin; Cui Tian; Guan Weiming; Zheng Weitao; Wang Wenquan; Zhao Xudong; Liu Xiaoyang

    2012-01-01

    Highlights: ► Platinum boride nanowires have been synthesized via the direct current arc discharge method. ► XRD, TEM and SAED indicate that the nanowires are single-crystal PtB. ► Two broad photoluminescence emission peaks at about 586 nm and 626 nm have been observed in the PL spectroscopy of PtB nanowires. - Abstract: Platinum boride (PtB) nanowires have been successfully fabricated with direct current arc discharge method using a milled mixture of platinum (Pt) and boron nitride (BN) powders. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the compositions, morphology, and structures of the samples. The results show that PtB nanowires are 30–50 nm thick and 20–30 μm long. TEM and selected area electron diffraction (SAED) patterns identify that the PtB nanowires are single-crystalline in nature. A growth mechanism based on vapor–liquid–solid (VLS) process is proposed for the formation of nanowires.

  3. Mechanical responses of a-axis GaN nanowires under axial loads

    Science.gov (United States)

    Wang, R. J.; Wang, C. Y.; Feng, Y. T.; Tang, Chun

    2018-03-01

    Gallium nitride (GaN) nanowires (NWs) hold technological significance as functional components in emergent nano-piezotronics. However, the examination of their mechanical responses, especially the mechanistic understanding of behavior beyond elasticity (at failure) remains limited due to the constraints of in situ experimentation. We therefore performed simulations of the molecular dynamics (MD) of the mechanical behavior of [1\\bar{2}10]-oriented GaN NWs subjected to tension or compression loading until failure. The mechanical properties and critical deformation processes are characterized in relation to NW sizes and loading conditions. Detailed examinations revealed that the failure mechanisms are size-dependent and controlled by the dislocation mobility on shuffle-set pyramidal planes. The size dependence of the elastic behavior is also examined in terms of the surface structure determined modification of Young’s modulus. In addition, a comparison with c-axis NWs is made to show how size-effect trends vary with the growth orientation of NWs.

  4. Title: Using Alignment and 2D Network Simulations to Study Charge Transport Through Doped ZnO Nanowire Thin Film Electrodes

    KAUST Repository

    Phadke, Sujay

    2011-09-30

    Factors affecting charge transport through ZnO nanowire mat films were studied by aligning ZnO nanowires on substrates and coupling experimental measurements with 2D nanowire network simulations. Gallium doped ZnO nanowires were aligned on thermally oxidized silicon wafer by shearing a nanowire dispersion in ethanol. Sheet resistances of nanowire thin films that had current flowing parallel to nanowire alignment direction were compared to thin films that had current flowing perpendicular to nanowire alignment direction. Perpendicular devices showed ∼5 fold greater sheet resistance than parallel devices supporting the hypothesis that aligning nanowires would increase conductivity of ZnO nanowire electrodes. 2-D nanowire network simulations of thin films showed that the device sheet resistance was dominated by inter-wire contact resistance. For a given resistivity of ZnO nanowires, the thin film electrodes would have the lowest possible sheet resistance if the inter-wire contact resistance was one order of magnitude lower than the single nanowire resistance. Simulations suggest that the conductivity of such thin film devices could be further enhanced by using longer nanowires. Solution processed Gallium doped ZnO nanowires are aligned on substrates using an innovative shear coating technique. Nanowire alignment has shown improvement in ZnO nanowire transparent electrode conductivity. 2D network simulations in conjunction with electrical measurements have revealed different regimes of operation of nanowire thin films and provided a guideline for improving electrical performance of nanowire electrodes. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Nanowire Lasers

    Directory of Open Access Journals (Sweden)

    Couteau C.

    2015-05-01

    Full Text Available We review principles and trends in the use of semiconductor nanowires as gain media for stimulated emission and lasing. Semiconductor nanowires have recently been widely studied for use in integrated optoelectronic devices, such as light-emitting diodes (LEDs, solar cells, and transistors. Intensive research has also been conducted in the use of nanowires for subwavelength laser systems that take advantage of their quasione- dimensional (1D nature, flexibility in material choice and combination, and intrinsic optoelectronic properties. First, we provide an overview on using quasi-1D nanowire systems to realize subwavelength lasers with efficient, directional, and low-threshold emission. We then describe the state of the art for nanowire lasers in terms of materials, geometry, andwavelength tunability.Next,we present the basics of lasing in semiconductor nanowires, define the key parameters for stimulated emission, and introduce the properties of nanowires. We then review advanced nanowire laser designs from the literature. Finally, we present interesting perspectives for low-threshold nanoscale light sources and optical interconnects. We intend to illustrate the potential of nanolasers inmany applications, such as nanophotonic devices that integrate electronics and photonics for next-generation optoelectronic devices. For instance, these building blocks for nanoscale photonics can be used for data storage and biomedical applications when coupled to on-chip characterization tools. These nanoscale monochromatic laser light sources promise breakthroughs in nanophotonics, as they can operate at room temperature, can potentially be electrically driven, and can yield a better understanding of intrinsic nanomaterial properties and surface-state effects in lowdimensional semiconductor systems.

  6. EDITORIAL: Nanowires for energy Nanowires for energy

    Science.gov (United States)

    LaPierre, Ray; Sunkara, Mahendra

    2012-05-01

    dominant lighting technology due to its superior electrical to optical conversion efficiency. A unique LED structure based on CdS is presented by Ye et al [8]. A detailed study by Nguyen et al [9] provides a fundamental understanding of the non-radiative recombination mechanisms in GaN-based white light emitting nanowire diodes grown on Si substrates. Another application of III-nitrides is in photovoltaic devices (solar cells) [10]. InGaN is the only semiconductor alloy whose energy bandgap can be continuously varied across nearly the entire solar spectrum, promising a new generation of solar cells. Another potentially important application for nanowires is the efficient production of H2 from the photocatalytic splitting of water, where the H2 can be used as an energy carrier. Water splitting based on unique nanostructures include Fe2O3 [11], CuS/ZnO [12], and ZnO/Si [13]. Another candidate for photocatalysis, among other applications, is copper oxide nanowires, reviewed by Gregor et al [14]. References [1] Hiralal P, Unalan H E and Amaratunga G A J 2012 Nanotechnology 23 194002 [2] Li J, Yu H and Li Y 2012 Nanotechnology 23 194010 [3] Wang B and Leu P W 2012 Nanotechnology 23 194003 [4] Yu L, O'Donnell B, Foldyna M, and Roca i Cabarrocas P 2012 Nanotechnology 23 194011 [5] Zhang F, Song T and Sun B 2012 Nanotechnology 23 194006 [6] Herman I, Yeo J, Hong S, Lee D, Nam K H, Choi J, Hong W, Lee D, Grigoropoulos C P and Ko S H 2012 Nanotechnology 23 194005 [7] Calestani D, Pattini F, Bissoli F, Gilioli E, Villani M and Zappettini A 2012 Nanotechnology 23 194008 [8] Ye Y, Yu B, Gao Z, Mang H, Zhang H, Dai L and Qin G 2012 Nanotechnology 23 194004 [9] Nguyen H P T, Djavid M, Cui K and Mi Z 2012 Nanotechnology 23 194012 [10] Wierer J J Jr, Li Q, Koleske D D, Lee S R L and Wang G T 2012 Nanotechnology 23 194007 [11] Chernomordik B D, Russell H B, Cvelbar U, Jasinski J B, Kumar V, Deutsch T and Sunkara M K 2012 Nanotechnology 23 194009 [12] Lee M and Yong K 2012 Nanotechnology 23

  7. 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. .

  8. Additional compound semiconductor nanowires for photonics

    Science.gov (United States)

    Ishikawa, F.

    2016-02-01

    GaAs related compound semiconductor heterostructures are one of the most developed materials for photonics. Those have realized various photonic devices with high efficiency, e. g., lasers, electro-optical modulators, and solar cells. To extend the functions of the materials system, diluted nitride and bismide has been paid attention over the past decade. They can largely decrease the band gap of the alloys, providing the greater tunability of band gap and strain status, eventually suppressing the non-radiative Auger recombinations. On the other hand, selective oxidation for AlGaAs is a vital technique for vertical surface emitting lasers. That enables precisely controlled oxides in the system, enabling the optical and electrical confinement, heat transfer, and mechanical robustness. We introduce the above functions into GaAs nanowires. GaAs/GaAsN core-shell nanowires showed clear redshift of the emitting wavelength toward infrared regime. Further, the introduction of N elongated the carrier lifetime at room temperature indicating the passivation of non-radiative surface recombinations. GaAs/GaAsBi nanowire shows the redshift with metamorphic surface morphology. Selective and whole oxidations of GaAs/AlGaAs core-shell nanowires produce semiconductor/oxide composite GaAs/AlGaOx and oxide GaOx/AlGaOx core-shell nanowires, respectively. Possibly sourced from nano-particle species, the oxide shell shows white luminescence. Those property should extend the functions of the nanowires for their application to photonics.

  9. Design and Characterisation of III-V Semiconductor Nanowire Lasers

    Science.gov (United States)

    Saxena, Dhruv

    The development of small, power-efficient lasers underpins many of the technologies that we utilise today. Semiconductor nanowires are promising for miniaturising lasers to even smaller dimensions. III-V semiconductors, such as Gallium Arsenide (GaAs) and Indium Phosphide (InP), are the most widely used materials for optoelectronic devices and so the development of nanowire lasers based on these materials is expected to have technologically significant outcomes. This PhD dissertation presents a comprehensive study of the design of III-V semiconductor nanowire lasers, with bulk and quantum confined active regions. Based on the design, various III-V semiconductor nanowire lasers are demonstrated, namely, GaAs nanowire lasers, GaAs/AlGaAs multi-quantum well (MQW) nanowire lasers and InP nanowire lasers. These nanowire lasers are shown to operate at room temperature, have low thresholds, and lase from different transverse modes. The structural and optoelectronic quality of nanowire lasers are characterised via electron microscopy and photoluminescence spectroscopic techniques. Lasing is characterised in all these devices by optical pumping. The lasing characteristics are analysed by rate equation modelling and the lasing mode(s) in these devices is characterised by threshold gain modelling, polarisation measurements and Fourier plane imaging. Firstly, GaAs nanowire lasers that operate at room temperature are demonstrated. This is achieved by determining the optimal nanowire diameter to reduce threshold gain and by passivating nanowires to improve their quantum efficiency (QE). High-quality surface passivated GaAs nanowires of suitable diameters are grown. The growth procedure is tailored to improve both QE and structural uniformity of nanowires. Room-temperature lasing is demonstrated from individual nanowires and lasing is characterised to be from TM01 mode by threshold gain modelling. To lower threshold even further, nanowire lasers with GaAs/AlGaAs coaxial multi

  10. Composition–dependent growth dynamics of selectively grown InGaAs nanowires

    International Nuclear Information System (INIS)

    Kohashi, Y; Hara, S; Motohisa, J

    2014-01-01

    We grew gallium-rich (x > 0.50) and indium-rich (x < 0.50) In 1 − x Ga x As nanowires by catalyst–free selective-area metal–organic vapor-phase epitaxy (SA-MOVPE), and compared their growth dynamics dependence on V/III ratio. It was found that the growth dynamics of In 1 − x Ga x As nanowires is clearly dependent on the alloy composition x. Specifically, for gallium–rich nanowire growth, the axial growth rate of nanowires initially increased with decreasing V/III ratio, and then started to decrease when the V/III ratio continued to decrease below a critical value. On the other hand, axial growth rate of indium-rich nanowires monotonically decreased with decreasing V/III ratio. In addition, the alloy composition was strongly dependent on the V/III ratio for gallium-rich nanowire growth, while it was relatively independent of the V/III ratio for indium-rich nanowire growth. We discuss the origin of dissimilarity in the growth dynamics dependence on V/III ratio between gallium-rich and indium-rich InGaAs nanowire growth, and conclude that it is due to the inherent dissimilarity between GaAs and InAs. Our finding provides important guidelines for achieving precise control of the diameter, height, and alloy composition of nanowires suitable for future nanowire-based electronics. (papers)

  11. Electrodeposition of Metal on GaAs Nanowires

    Science.gov (United States)

    Liu, Chao; Einabad, Omid; Watkins, Simon; Kavanagh, Karen

    2010-10-01

    Copper (Cu) electrical contacts to freestanding gallium arsenide (GaAs) nanowires have been fabricated via electrodeposition. The nanowires are zincblende (111) oriented grown epitaxially on n-type Si-doped GaAs (111)B substrates by gold-catalyzed Vapor Liquid Solid (VLS) growth in a metal organic vapour phase epitaxy (MOVPE) reactor. The epitaxial electrodeposition process, based on previous work with bulk GaAs substrates, consists of a substrate oxide pre-etch in dilute ammonium-hydroxide carried out prior to galvanostatic electrodeposition in a pure Cu sulphate aqueous electrolyte at 20-60^oC. For GaAs nanowires, we find that Cu or Fe has a preference for growth on the gold catalyst avoiding the sidewalls. After removing gold, both metals still prefer to grow only on top of the nanowire, which has the largest potential field.

  12. 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

  13. Toward optimized light utilization in nanowire arrays using scalable nanosphere lithography and selected area growth.

    Science.gov (United States)

    Madaria, Anuj R; Yao, Maoqing; Chi, Chunyung; Huang, Ningfeng; Lin, Chenxi; Li, Ruijuan; Povinelli, Michelle L; Dapkus, P Daniel; Zhou, Chongwu

    2012-06-13

    Vertically aligned, catalyst-free semiconducting nanowires hold great potential for photovoltaic applications, in which achieving scalable synthesis and optimized optical absorption simultaneously is critical. Here, we report combining nanosphere lithography (NSL) and selected area metal-organic chemical vapor deposition (SA-MOCVD) for the first time for scalable synthesis of vertically aligned gallium arsenide nanowire arrays, and surprisingly, we show that such nanowire arrays with patterning defects due to NSL can be as good as highly ordered nanowire arrays in terms of optical absorption and reflection. Wafer-scale patterning for nanowire synthesis was done using a polystyrene nanosphere template as a mask. Nanowires grown from substrates patterned by NSL show similar structural features to those patterned using electron beam lithography (EBL). Reflection of photons from the NSL-patterned nanowire array was used as a measure of the effect of defects present in the structure. Experimentally, we show that GaAs nanowires as short as 130 nm show reflection of <10% over the visible range of the solar spectrum. Our results indicate that a highly ordered nanowire structure is not necessary: despite the "defects" present in NSL-patterned nanowire arrays, their optical performance is similar to "defect-free" structures patterned by more costly, time-consuming EBL methods. Our scalable approach for synthesis of vertical semiconducting nanowires can have application in high-throughput and low-cost optoelectronic devices, including solar cells.

  14. Insufficiency of the Young’s modulus for illustrating the mechanical behavior of GaN nanowires

    Science.gov (United States)

    Zamani Kouhpanji, Mohammad Reza; Behzadirad, Mahmoud; Feezell, Daniel; Busani, Tito

    2018-05-01

    We use a non-classical modified couple stress theory including the acceleration gradients (MCST-AG), to precisely demonstrate the size dependency of the mechanical properties of gallium nitride (GaN) nanowires (NWs). The fundamental elastic constants, Young’s modulus and length scales of the GaN NWs were estimated both experimentally, using a novel experimental technique applied to atomic force microscopy, and theoretically, using atomic simulations. The Young’s modulus, static and the dynamic length scales, calculated with the MCST-AG, were found to be 323 GPa, 13 and 14.5 nm, respectively, for GaN NWs from a few nanometers radii to bulk radii. Analyzing the experimental data using the classical continuum theory shows an improvement in the experimental results by introducing smaller error. Using the length scales determined in MCST-AG, we explain the inconsistency of the Young’s moduli reported in recent literature, and we prove the insufficiency of the Young’s modulus for predicting the mechanical behavior of GaN NWs.

  15. An enhanced surface passivation effect in InGaN/GaN disk-in-nanowire light emitting diodes for mitigating Shockley–Read–Hall recombination

    KAUST Repository

    Zhao, Chao; Ng, Tien Khee; Prabaswara, Aditya; Conroy, Michele; Jahangir, Shafat; Frost, Thomas; O'Connell, John; Holmes, Justin D.; Parbrook, Peter; Bhattacharya, Pallab; Ooi, Boon S.

    2015-01-01

    demonstrated the first organic sulfide passivation process for nitride nanowires (NWs). The results from Raman spectroscopy, photoluminescence (PL) measurements, and X-ray photoelectron spectroscopy (XPS) showed octadecylthiol (ODT) effectively passivated

  16. Packing C60 in Boron Nitride Nanotubes

    Science.gov (United States)

    Mickelson, W.; Aloni, S.; Han, Wei-Qiang; Cumings, John; Zettl, A.

    2003-04-01

    We have created insulated C60 nanowire by packing C60 molecules into the interior of insulating boron nitride nanotubes (BNNTs). For small-diameter BNNTs, the wire consists of a linear chain of C60 molecules. With increasing BNNT inner diameter, unusual C60 stacking configurations are obtained (including helical, hollow core, and incommensurate) that are unknown for bulk or thin-film forms of C60. C60 in BNNTs thus presents a model system for studying the properties of dimensionally constrained ``silo'' crystal structures. For the linear-chain case, we have fused the C60 molecules to form a single-walled carbon nanotube inside the insulating BNNT.

  17. 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.

  18. Gallium Nitride Direct Energy Conversion Betavoltaic Modeling and Optimization

    Science.gov (United States)

    2017-03-01

    power source. Autonomous systems such as space satellites require power sources that have strict size , weight, and power (SWaP) limitations, which...conversion process, called beta- photovoltaics , has a system efficiency that is dependent on both the conversion efficiency of the phosphor and the...effectively providing 9 J per day for autonomous systems . However, the volume for beta- photovoltaics is larger due to the need for phosphors to

  19. Polarity Control and Doping in Aluminum Gallium Nitride

    Science.gov (United States)

    2013-06-01

    Ladungsträger. Diese hohen Konzentrationen werden dadurch erklärt, dass im Bereich hoher Dotierungen die Formierungsenergien dieser Störstellen...elektrischen Widerstand führt. Des Weiteren wird im Rahmen dieser Arbeit gezeigt, dass das hier vorgestellte Modell zur Kontrolle des Einbaus von Defekten

  20. Gallium-Nitride-Based Light-Emitting Diodes

    Indian Academy of Sciences (India)

    IAS Admin

    Lehovec and colleagues at the Signal Corps Engineering Labora- tory, in 1951 ... junction (Figure 3b), the potential barrier is reduced from V. 0 to. (V. 0. – V). .... A A Bright, The Electric-Lamp Industry: Technological Change and. Economic ...

  1. Gallium nitride heterostructures on 3D structured silicon.

    Science.gov (United States)

    Fündling, Sönke; Sökmen, Unsal; Peiner, Erwin; Weimann, Thomas; Hinze, Peter; Jahn, Uwe; Trampert, Achim; Riechert, Henning; Bakin, Andrey; Wehmann, Hergo-Heinrich; Waag, Andreas

    2008-10-08

    We investigated GaN-based heterostructures grown on three-dimensionally patterned Si(111) substrates by metal organic vapour phase epitaxy, with the goal of fabricating well controlled high quality, defect reduced GaN-based nanoLEDs. The high aspect ratios of such pillars minimize the influence of the lattice mismatched substrate and improve the material quality. In contrast to other approaches, we employed deep etched silicon substrates to achieve a controlled pillar growth. For that a special low temperature inductively coupled plasma etching process has been developed. InGaN/GaN multi-quantum-well structures have been incorporated into the pillars. We found a pronounced dependence of the morphology of the GaN structures on the size and pitch of the pillars. Spatially resolved optical properties of the structures are analysed by cathodoluminescence.

  2. Gallium nitride heterostructures on 3D structured silicon

    Energy Technology Data Exchange (ETDEWEB)

    Fuendling, Soenke; Soekmen, Uensal; Peiner, Erwin; Bakin, Andrey; Wehmann, Hergo-Heinrich; Waag, Andreas [Institut fuer Halbleitertechnik, Hans-Sommer-Strasse 66, 38106 Braunschweig (Germany); Weimann, Thomas; Hinze, Peter [Physikalisch Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig (Germany); Jahn, Uwe; Trampert, Achim; Riechert, Henning [Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)], E-mail: s.fuendling@tu-bs.de

    2008-10-08

    We investigated GaN-based heterostructures grown on three-dimensionally patterned Si(111) substrates by metal organic vapour phase epitaxy, with the goal of fabricating well controlled high quality, defect reduced GaN-based nanoLEDs. The high aspect ratios of such pillars minimize the influence of the lattice mismatched substrate and improve the material quality. In contrast to other approaches, we employed deep etched silicon substrates to achieve a controlled pillar growth. For that a special low temperature inductively coupled plasma etching process has been developed. InGaN/GaN multi-quantum-well structures have been incorporated into the pillars. We found a pronounced dependence of the morphology of the GaN structures on the size and pitch of the pillars. Spatially resolved optical properties of the structures are analysed by cathodoluminescence.

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

    Indian Academy of Sciences (India)

    Si-doped GaN films in polycrystalline form were deposited on quartz substrates at deposition temperatures ranging from 300–623 K using r.f. sputtering technique. Electrical, optical and microstructural properties were studied for these films. It was observed that films deposited at room temperature contained mainly ...

  4. Kinase detection with gallium nitride based high electron mobility transistors.

    Science.gov (United States)

    Makowski, Matthew S; Bryan, Isaac; Sitar, Zlatko; Arellano, Consuelo; Xie, Jinqiao; Collazo, Ramon; Ivanisevic, Albena

    2013-07-01

    A label-free kinase detection system was fabricated by the adsorption of gold nanoparticles functionalized with kinase inhibitor onto AlGaN/GaN high electron mobility transistors (HEMTs). The HEMTs were operated near threshold voltage due to the greatest sensitivity in this operational region. The Au NP/HEMT biosensor system electrically detected 1 pM SRC kinase in ionic solutions. These results are pertinent to drug development applications associated with kinase sensing.

  5. Gallium nitride nanoparticles for solar-blind detectors

    Indian Academy of Sciences (India)

    Unknown

    potential candidate for photodetection in the solar-blind region. ... engine monitoring, water purification, UV radiation dosimetry, pollution monitoring, .... rated current in the bulk and depletion region, surface leakage currents and the space-.

  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. Advanced processing of gallium nitride and gallium nitride-based devices: Ultra-high temperature annealing and implantation incorporation

    Science.gov (United States)

    Yu, Haijiang

    This dissertation is focused on three fields: ultra-high temperature annealing of GaN, activation of implanted GaN and the implantation incorporation into AlGaN/GaN HEMT processing, with an aim to increase the performance, manufacturability and reliability of AlGaN/GaN HEMTs. First, the ultra high temperature (around 1500°C) annealing of MOCVD grown GaN on sapphire has been studied, and a thermally induced threading dislocation (TD) motion and reaction are reported. Using a rapid thermal annealing (RTA) approach capable of heating 2 inch wafers to around 1500°C with 100 bar N2 over-pressure, evidence of dislocation motion was first observed in transmission electron microscopy (TEM) micrographs of both planar and patterned GaN films protected by an AIN capping layer. An associated decrease in x-ray rocking curve (XRC) full-width-half-maximum (FWHM) was also observed for both the symmetric and asymmetric scans. After annealing, the AIN capping layer remained intact, and optical measurements showed no degradation of the opto-electronic properties of the films. Then activation annealing of Si implants in MOCVD grown GaN has been studied for use in ohmic contacts. Si was implanted in semi-insulating GaN at 100 keV with doses from 5 x 1014 cm-2 to 1.5 x 1016 cm-2. Rapid thermal annealing at 1500°C with 100 bar N2 over-pressure was used for dopant activation, resulting in a minimum sheet resistance of 13.9 O/square for a dose of 7 x 1015 cm-2. Secondary ion mass spectroscopy measurements showed a post-activation broadening of the dopant concentration peak by 20 nm (at half the maximum), while X-Ray triple axis o-2theta scans indicated nearly complete implant damage recovery. Transfer length method measurements of the resistance of Ti/Al/Ni/Au contacts to activated GaN:Si (5 x 1015 cm-2 at 100 keV) indicated lowest contact resistances of 0.07 Omm and 0.02 Omm for as-deposited and subsequently annealed contacts, respectively. Finally, the incorporation of Si implantation into AlGaN/GaN high electron mobility transistor processing has been first demonstrated. An ultra-high temperature (1500°C) rapid thermal annealing technique was developed for the activation of Si dopants implanted in the source and drain. In comparison to control devices processed by conventional fabrication, the implanted device with nonalloyed ohmic contact showed comparable device performance with a contact resistance of 0.4 Omm Imax 730 mA/mm ft/f max; 26/62 GHz and power 3.4 W/mm on sapphire. These early results demonstrate the feasibility of implantation incorporation into GaN based device processing as well as the potential to increase yield, reproducibility and reliability in AlGaN/GaN HEMTs.

  8. Lattice Dynamics of Gallium Phosphide

    International Nuclear Information System (INIS)

    Yarnell, J.L.; Warren, J.L.; Wenzel, R.G.; Dean, P.J.

    1968-01-01

    Dispersion curves for phonons propagating in the [100], [110], and [111] directions in gallium phosphide have been measured using a triple-axis neutron diffraction spectrometer operating in the constant-Q mode. The sample was a pseudo-single crystal which was prepared by gluing together 36 single crystal plates of gallium phosphide 1 to 2.5 cm in diameter and ∼0.07 cm thick. The plates were grown epitaxially on substrates of gallium arsenide or gallium phosphide, and aligned individually by neutron diffraction. Rocking curves for eight reflections symmetrically distributed in the plane of the experiment had full widths at half maximum in the range 0.52° - 0.58° and were approximately Gaussian in shape. Gallium phosphide crystallizes in the zinc blende structure. A group theoretic analysis of the lattice dynamics of this structure and a shell model fit to the measured dispersion curves are presented. Various optical properties of gallium phosphide are discussed in terms of the phonon dispersion curves. In particular, the phonons which assist indirect electronic transitions are identified as those at the zone boundary in the [100] direction (symmetry point X) in agreement with theoretical and experimental indications that the extrema of the conduction and valence bands are at X and Γ (center of the zone), respectively. The LO branches lie above the TO branches throughout the Brillouin zone in contradiction to the predictions of Keyes and Mitra. The shell model fit indicates that the charge on the gallium atom is negative. (author)

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

    Science.gov (United States)

    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-unreported CaZn2N2 that has earth-abundant components, smaller carrier effective masses than gallium nitride and a tunable direct bandgap suited for light emission and harvesting. High-pressure synthesis realizes this phase, verifying the predicted crystal structure and band-edge red photoluminescence. In total, we propose 21 promising systems, including Ca2ZnN2, Ba2ZnN2 and Zn2PN3, which have not been reported as semiconductors previously. Given the variety in bandgaps of the identified compounds, the present study expands the potential suitability of nitride semiconductors for a broader range of electronic, optoelectronic and photovoltaic applications. PMID:27325228

  10. 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

  11. Nanoscale Electronic Conditioning for Improvement of Nanowire Light-Emitting-Diode Efficiency.

    Science.gov (United States)

    May, Brelon J; Belz, Matthew R; Ahamed, Arshad; Sarwar, A T M G; Selcu, Camelia M; Myers, Roberto C

    2018-04-24

    Commercial III-Nitride LEDs and lasers spanning visible and ultraviolet wavelengths are based on epitaxial films. Alternatively, nanowire-based III-Nitride optoelectronics offer the advantage of strain compliance and high crystalline quality growth on a variety of inexpensive substrates. However, nanowire LEDs exhibit an inherent property distribution, resulting in uneven current spreading through macroscopic devices that consist of millions of individual nanowire diodes connected in parallel. Despite being electrically connected, only a small fraction of nanowires, sometimes current in the ensemble devices. Burn-in electronic conditioning is performed by applying a short-term overload voltage; the nanoshorts experience very high current density, sufficient to render them open circuits, thereby forcing a new current path through more nanowire LEDs in an ensemble device. Current-voltage measurements of individual nanowires are acquired using conductive atomic force microscopy to observe the removal of nanoshorts using burn-in. In macroscopic devices, this results in a 33× increase in peak EL and reduced leakage current. Burn-in conditioning of nanowire ensembles therefore provides a straightforward method to mitigate nonuniformities inherent to nanowire devices.

  12. Prospects for recovering gallium from extracted coal

    Energy Technology Data Exchange (ETDEWEB)

    Ratynskiy, V M; Reznik, A M; Zekel, L A; Zharov, Yu N

    1979-01-01

    The authors conducted research in order to establish the physical-chemical mechanisms governing the behavior of rare and dispersed elements within the thermal treatment processes used to treat coal and enrichment waste. New means are proposed for obtaining concentrations of gallium. These methods are under consideration primarily for the isolation of gallium as a by-product during the production of aggloporite from coal waste. The authors examine in detail the results of research dealing with the transfer of gallium compounds in a solution, the extraction of gallium from solutions, the separation of impurities from gallium, and the isolation of gallium from extract. Utilizing research results, the authors determine the expenditure coefficient and costs for additives used to extract gallium from waste by-products. The realization of this gallium extraction process from those products having the best prospects for gallium content resulted in economic savings.

  13. Investigation on gallium ions impacting monolayer graphene

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Xin; Zhao, Haiyan, E-mail: hyzhao@tsinghua.edu.cn; Yan, Dong; Pei, Jiayun [State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, P. R. Chinaand Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China)

    2015-06-15

    In this paper, the physical phenomena of gallium (Ga{sup +}) ion impacting monolayer graphene in the nanosculpting process are investigated experimentally, and the mechanisms are explained by using Monte Carlo (MC) and molecular dynamics (MD) simulations. Firstly, the MC method is employed to clarify the phenomena happened to the monolayer graphene target under Ga{sup +} ion irradiation. It is found that substrate has strong influence on the damage mode of graphene. The mean sputtering yield of graphene under 30 keV Ga{sup +} ion irradiation is 1.77 and the least ion dose to completely remove carbon atoms in graphene is 21.6 ion/nm{sup 2}. Afterwards, the focused ion beam over 21.6 ion/nm{sup 2} is used for the irradiation on a monolayer graphene supported by SiO2 experimentally, resulting in the nanostructures, i.e., nanodot and nanowire array on the graphene. The performances of the nanostructures are characterized by atomic force microscopy and Raman spectrum. A plasma plume shielding model is put forward to explain the nanosculpting results of graphene under different irradiation parameters. In addition, two damage mechanisms are found existing in the fabrication process of the nanostructures by using empirical MD simulations. The results can help us open the possibilities for better control of nanocarbon devices.

  14. Polarity Control of Heteroepitaxial GaN Nanowires on Diamond.

    Science.gov (United States)

    Hetzl, Martin; Kraut, Max; Hoffmann, Theresa; Stutzmann, Martin

    2017-06-14

    Group III-nitride materials such as GaN nanowires are characterized by a spontaneous polarization within the crystal. The sign of the resulting sheet charge at the top and bottom facet of a GaN nanowire is determined by the orientation of the wurtzite bilayer of the different atomic species, called N and Ga polarity. We investigate the polarity distribution of heteroepitaxial GaN nanowires on different substrates and demonstrate polarity control of GaN nanowires on diamond. Kelvin Probe Force Microscopy is used to determine the polarity of individual selective area-grown and self-assembled nanowires over a large scale. At standard growth conditions, mixed polarity occurs for selective GaN nanowires on various substrates, namely on silicon, on sapphire and on diamond. To obtain control over the growth orientation on diamond, the substrate surface is modified by nitrogen and oxygen plasma exposure prior to growth, and the growth parameters are adjusted simultaneously. We find that the surface chemistry and the substrate temperature are the decisive factors for obtaining control of up to 93% for both polarity types, whereas the growth mode, namely selective area or self-assembled growth, does not influence the polarity distribution significantly. The experimental results are discussed by a model based on the interfacial bonds between the GaN nanowires, the termination layer, and the substrate.

  15. 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

  16. ASSESSMENT OF GALLIUM OXIDE TECHNOLOGY

    Science.gov (United States)

    2017-08-01

    AFRL-RY-WP-TR-2017-0167 ASSESSMENT OF GALLIUM OXIDE TECHNOLOGY Burhan Bayraktaroglu Devices for Sensing Branch Aerospace...TITLE AND SUBTITLE ASSESSMENT OF GALLIUM OXIDE TECHNOLOGY 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER N/A 6...report summarizes the current status of the Ga2O3 technology based on published results on theoretical electronic structure, materials growth, and

  17. Gallium and imaging studies

    International Nuclear Information System (INIS)

    Vogel, H.C.

    1982-01-01

    The indications for the use of 67 Gallium imaging studies of the lungs are discussed. In spite of localization of 67 Ga in a large variety of neoplastic and inflammatory tissues, there is only limited application of the lung study in the differential diagnosis of pulmonary diseases. The chest radiograph will continue to be the principal tool for evaluation of pulmonary diseases. The 67 Ga-citrate scan serves as a study complementary to the chest radiograph, as it indicates the localization, extent and degree of activity of lung disease with greater accuracy than radiography. Gallium-67 scanning may be used in the evaluation of patients with lymphoreticular neoplasms, especially Hodgkin-disease and malignant lymphoma both during initial staging and in evaluation of the response to therapy. The 67 Ga-citrate scan is useful in the pre-operative evaluation of patients with lung cancer. Hilar and mediastinal lymphadenopathy are accurately revealed. The lung study is non-invasive and complementary to mediastinoscopy by showing from which glands a biopsy might be taken. Unsuspected extrathoracic secondaries may be shown up, as well as pulmonary metastases from malignancies elsewhere, although the metastases must be at least 1,5 cm in size. The 67 Ga lung scan is valuable in the evaluation of pulmonary infiltrates of suspicious infective etiology, the differentiation between pulmonary infection and pneumonia in selected cases, follow-up of sarcoid patients on corticosteroid therapy, evaluation of inflammatory activity of idiopathic pulmonary fibrosis and the early detection of neo-plastic or inflammatory diseases before the chest radiograph reveals abnormality, e.g. in diffuse carcinomatosis or Pneumocystis carinii-infection. The sensitivity of tumors to radiation or chemotherapy may be shown

  18. Structural variations in nanosized confined gallium

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Min Kai [Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan (China); Tien Cheng [Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan (China)] [Center for Micro/Nano Science of Technology, National Cheng Kung University, Tainan 70101, Taiwan, ROC (China); Charnaya, E.V., E-mail: charnaya@live.co [Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan (China)] [Institute of Physics, St. Petersburg State University, St. Petersburg, Petrodvorets 198504 (Russian Federation); Sheu, Hwo-Shuenn [National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan (China); Kumzerov, Yu.A. [A.F. Ioffe Physico-Technical Institute RAS, St. Petersburg, 194021 (Russian Federation)

    2010-03-29

    The complex crystalline structure of gallium under nanoconfinement was revealed by synchrotron radiation x-ray powder diffraction. Nanoconfinement was shown to stabilize delta-Ga which is metastable in bulk. Two new gallium phases named iota- and kappa-Ga were found upon cooling below room temperature. These crystalline modifications were stable and coexisted with known gallium phases. Correlations between confined gallium particle shapes and emergence of particular crystalline phases were observed. Melting and freezing temperatures for different gallium phases were obtained. Remarkable supercooling of liquid gallium was seen in 3.5 nm pores.

  19. Photoconduction efficiencies and dynamics in GaN nanowires grown by chemical vapor deposition and molecular beam epitaxy: A comparison study

    International Nuclear Information System (INIS)

    Chen, R. S.; Tsai, H. Y.; Huang, Y. S.; Chen, Y. T.; Chen, L. C.; Chen, K. H.

    2012-01-01

    The normalized gains, which determines the intrinsic photoconduction (PC) efficiencies, have been defined and compared for the gallium nitride (GaN) nanowires (NWs) grown by chemical vapor deposition (CVD) and molecular beam epitaxy (MBE). By excluding the contributions of experimental parameters and under the same light intensity, the CVD-grown GaN NWs exhibit the normalized gain which is near two orders of magnitude higher than that of the MBE-ones. The temperature-dependent time-resolved photocurrent measurement further indicates that the higher photoconduction efficiency in the CVD-GaN NWs is originated from the longer carrier lifetime induced by the higher barrier height (φ B = 160 ± 30 mV) of surface band bending. In addition, the experimentally estimated barrier height at 20 ± 2 mV for the MBE-GaN NWs, which is much lower than the theoretical value, is inferred to be resulted from the lower density of charged surface states on the non-polar side walls.

  20. Optical Properties of Strained Wurtzite Gallium Phosphide Nanowires

    KAUST Repository

    Greil, J.; Assali, S.; Isono, Y.; Belabbes, Abderrezak; Bechstedt, F.; Valega Mackenzie, F. O.; Silov, A. Yu.; Bakkers, E. P. A. M.; Haverkort, J. E. M.

    2016-01-01

    with a theoretical analysis of strain effects is employed to establish the nature and symmetry of the transitions. We identify the emission lines to be related to localized states with significant admixture of Γ7c symmetry and not exclusively related

  1. Methanol, ethanol and hydrogen sensing using metal oxide and metal (TiO(2)-Pt) composite nanoclusters on GaN nanowires: a new route towards tailoring the selectivity of nanowire/nanocluster chemical sensors.

    Science.gov (United States)

    Aluri, Geetha S; Motayed, Abhishek; Davydov, Albert V; Oleshko, Vladimir P; Bertness, Kris A; Sanford, Norman A; Mulpuri, Rao V

    2012-05-04

    We demonstrate a new method for tailoring the selectivity of chemical sensors using semiconductor nanowires (NWs) decorated with metal and metal oxide multicomponent nanoclusters (NCs). Here we present the change of selectivity of titanium dioxide (TiO(2)) nanocluster-coated gallium nitride (GaN) nanowire sensor devices on the addition of platinum (Pt) nanoclusters. The hybrid sensor devices were developed by fabricating two-terminal devices using individual GaN NWs followed by the deposition of TiO(2) and/or Pt nanoclusters (NCs) using the sputtering technique. This paper present the sensing characteristics of GaN/(TiO(2)-Pt) nanowire-nanocluster (NWNC) hybrids and GaN/(Pt) NWNC hybrids, and compare their selectivity with that of the previously reported GaN/TiO(2) sensors. The GaN/TiO(2) NWNC hybrids showed remarkable selectivity to benzene and related aromatic compounds, with no measurable response for other analytes. Addition of Pt NCs to GaN/TiO(2) sensors dramatically altered their sensing behavior, making them sensitive only to methanol, ethanol and hydrogen, but not to any other chemicals we tested. The GaN/(TiO(2)-Pt) hybrids were able to detect ethanol and methanol concentrations as low as 100 nmol mol(-1) (ppb) in air in approximately 100 s, and hydrogen concentrations from 1 µmol mol(-1) (ppm) to 1% in nitrogen in less than 60 s. However, GaN/Pt NWNC hybrids showed limited sensitivity only towards hydrogen and not towards any alcohols. All these hybrid sensors worked at room temperature and are photomodulated, i.e. they responded to analytes only in the presence of ultraviolet (UV) light. We propose a qualitative explanation based on the heat of adsorption, ionization energy and solvent polarity to explain the observed selectivity of the different hybrids. These results are significant from the standpoint of applications requiring room-temperature hydrogen sensing and sensitive alcohol monitoring. These results demonstrate the tremendous potential for

  2. Novel Crystal Structure C60 Nanowire

    Science.gov (United States)

    Mickelson, William; Aloni, Shaul; Han, Weiqiang; Cumings, John; Zettl, Alex

    2003-03-01

    We have created insulated C60 nanowire by packing C60 molecules into the interior of insulating boron nitride (BN) nanotubes. For small-diameter BN tubes, the wire consists of a linear chain of C60's. With increasing BN tube inner diameter, novel C60 stacking configurations are obtained (including helical, hollow core, and incommensurate) which are unknown for bulk or thin film forms of C60. C60 in BN nanotubes presents a model system for studying the properties of new dimensionally-constrained "silo" crystal structures.

  3. Waveguide-integrated single- and multi-photon detection at telecom wavelengths using superconducting nanowires

    International Nuclear Information System (INIS)

    Ferrari, Simone; Kahl, Oliver; Kovalyuk, Vadim; Goltsman, Gregory N.; Korneev, Alexander; Pernice, Wolfram H. P.

    2015-01-01

    We investigate single- and multi-photon detection regimes of superconducting nanowire detectors embedded in silicon nitride nanophotonic circuits. At near-infrared wavelengths, simultaneous detection of up to three photons is observed for 120 nm wide nanowires biased far from the critical current, while narrow nanowires below 100 nm provide efficient single photon detection. A theoretical model is proposed to determine the different detection regimes and to calculate the corresponding internal quantum efficiency. The predicted saturation of the internal quantum efficiency in the single photon regime agrees well with plateau behavior observed at high bias currents

  4. Waveguide-integrated single- and multi-photon detection at telecom wavelengths using superconducting nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Ferrari, Simone; Kahl, Oliver [Institute of Nanotechnology, Karlsruhe Institute of Technology, Karlsruhe 76132 (Germany); Kovalyuk, Vadim [Institute of Nanotechnology, Karlsruhe Institute of Technology, Karlsruhe 76132 (Germany); Department of Physics, Moscow State Pedagogical University, Moscow 119992 (Russian Federation); Goltsman, Gregory N. [Department of Physics, Moscow State Pedagogical University, Moscow 119992 (Russian Federation); National Research University Higher School of Economics, 20 Myasnitskaya Ulitsa, Moscow 101000 (Russian Federation); Korneev, Alexander [Department of Physics, Moscow State Pedagogical University, Moscow 119992 (Russian Federation); Moscow Institute of Physics and Technology (State University), Moscow 141700 (Russian Federation); Pernice, Wolfram H. P., E-mail: wolfram.pernice@kit.edu [Institute of Nanotechnology, Karlsruhe Institute of Technology, Karlsruhe 76132 (Germany); Department of Physics, University of Münster, 48149 Münster (Germany)

    2015-04-13

    We investigate single- and multi-photon detection regimes of superconducting nanowire detectors embedded in silicon nitride nanophotonic circuits. At near-infrared wavelengths, simultaneous detection of up to three photons is observed for 120 nm wide nanowires biased far from the critical current, while narrow nanowires below 100 nm provide efficient single photon detection. A theoretical model is proposed to determine the different detection regimes and to calculate the corresponding internal quantum efficiency. The predicted saturation of the internal quantum efficiency in the single photon regime agrees well with plateau behavior observed at high bias currents.

  5. Superconductivity and structure of gallium under nanoconfinement

    Energy Technology Data Exchange (ETDEWEB)

    Charnaya, E V; Tien, Cheng; Lee, Min Kai [Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan (China); Kumzerov, Yu A [A F Ioffe Physico-Technical Institute RAS, St Petersburg, 194021 (Russian Federation)

    2009-11-11

    Superconductivity and crystalline structure were studied for two nanocomposites consisting of gallium loaded porous glasses with different pore sizes. The superconducting transition temperatures were found to differ from those in known bulk gallium modifications. The transition temperatures 7.1 and 6.7 K were ascribed to two new confined gallium structures, iota- and kappa-Ga, observed by synchrotron radiation x-ray powder diffraction. The evolution of superconductivity on decreasing the pore filling with gallium was also studied.

  6. 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 fundamental native defect is responsible for the recombination. Those with lifetimes above the predicted values have anomalous temperature dependences when measured, and often a non-exponential photoconductive decay characteristic of minority carrier traps. Deep level trap concentrations in GaN can harm performance in many desired applications. Deep Level Transient Spectroscopy (DLTS) measurement on MBE GaN suggest that the trapping center concentration drops with temperature below 770°C.

  7. Hydrogen inventory in gallium

    International Nuclear Information System (INIS)

    Mazayev, S.N.; Prokofiev, Yu.G.

    1994-01-01

    Investigations of hydrogen inventory in gallium (99.9%) were carried out after saturation both from molecular phase and from glow discharge plasma at room temperature, 370 and 520 K. Saturation took place during 3000 s under hydrogen pressure of 20 Pa, and ion flux was about 1x10 15 ions/cm 2 s with an energy about 400 eV during discharge. Hydrogen concentration in Ga at room temperature and that for 370 K by the saturation from gaseous phase was (2-3)x10 14 cm -3 Pa -1/2 . Hydrogen concentration at temperature 520 K increased by five times. Inventory at room temperature for irradiation from discharge was 7x10 16 cm -3 at the dose about 3x10 18 ions/cm 2 . It was more than inventory at temperature 520 K by four times and more than maximum inventory from gaseous phase at 520 K by a factor of 10. Inventory increased when temperature decreased. Diffusion coefficient D=0.003 exp(-2300/RT) cm 2 /s, was estimated from temperature dependence. ((orig.))

  8. Electrochemical properties of lanthanum nitride with calcium nitride additions

    International Nuclear Information System (INIS)

    Lesunova, R.P.; Fishman, L.S.

    1986-01-01

    This paper reports on the electrochemical properties of lanthanum nitride with calcium nitride added. The lanthanum nitride was obtained by nitriding metallic lanthanum at 870 K in an ammonia stream. The product contained Cl, Pr, Nd, Sm, Fe, Ca, Cu, Mo, Mg, Al, Si, and Be. The calcium nitride was obtained by nitriding metallic calcium in a nitrogen stream. The conductivity on the LaN/C 3 N 2 system components are shown as a function of temperature. A table shows the solid solutions to be virtually electronic conductors and the lanthanum nitride a mixed conductor

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

    International Nuclear Information System (INIS)

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

    1989-01-01

    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

  10. Gallium scintigraphy in Hansen's disease

    International Nuclear Information System (INIS)

    Braga, F.J.H.N.; Sao Paulo Univ., SP; Araejo, E.B.; Camargo, E.E.; Tedesco-Marchesi, L.C.M.; Rivitti, M.C.M.; Bouladour, H.; Galle, P.

    1991-01-01

    Gallium 67 imaging was used in 12 patients with documented Hansen's disease undergoing treatment or not in an attempt to determine the pattern of the disease. Diagnosis was confirmed by histopathology in all patients. The Mitsuda reaction was seen in all patients. Specific nuclear studies were performed when needed to evaluate particular organs better. Gallium 67 images show homogeneous, diffuse and moderate accumulation over the entire skin surface (except for the face) of untreated patients with multibacillary disease. The face skin in these cases presented homogeneous, diffuse but very marked uptake of gallium. Internal organ involvement was variable. There was a very good correlation among clinical, scintigraphical, immunological and histopathological data. The pattern of the body skin ('skin outlining') and face skin ('beard distribution') may be distinct for untreated patients with multibacillary leprosy. (orig.)

  11. 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.

  12. Magnetic and superconducting nanowires

    DEFF Research Database (Denmark)

    Piraux, L.; Encinas, A.; Vila, L.

    2005-01-01

    magnetic and superconducting nanowires. Using different approaches entailing measurements on both single wires and arrays, numerous interesting physical properties have been identified in relation to the nanoscopic dimensions of these materials. Finally, various novel applications of the nanowires are also...

  13. Vertical nanowire architectures

    DEFF Research Database (Denmark)

    Vlad, A.; Mátéfl-Tempfli, M.; Piraux, L.

    2010-01-01

    Nanowires and statistics: A statistical process for reading ultradense arrays of nanostructured materials is presented (see image). The experimental realization is achieved through selective nanowire growth using porous alumina templates. The statistical patterning approach is found to provide ri...

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

    International Nuclear Information System (INIS)

    Tanaka, Akiyo

    2004-01-01

    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

  15. 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

  16. Transport and structural characterization of solution-processable doped ZnO nanowires

    KAUST Repository

    Noriega, Rodrigo

    2009-08-18

    The use of ZnO nanowires has become a widespread topic of interest in optoelectronics. In order to correctly assess the quality, functionality, and possible applications of such nanostructures it is important to accurately understand their electrical and optical properties. Aluminum- and gallium-doped crystalline ZnO nanowires were synthesized using a low-temperature solution-based process, achieving dopant densities of the order of 1020 cm-3. A non-contact optical technique, photothermal deflection spectroscopy, is used to characterize ensembles of ZnO nanowires. By modeling the free charge carrier absorption as a Drude metal, we are able to calculate the free carrier density and mobility. Determining the location of the dopant atoms in the ZnO lattice is important to determine the doping mechanisms of the ZnO nanowires. Solid-state NMR is used to distinguish between coordination environments of the dopant atoms.

  17. 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.)

  18. InGaN/GaN core/shell nanowires for visible to ultraviolet range photodetection

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hezhi; Lavenus, Pierre; Julien, Francois H.; Tchernycheva, Maria [Institut d' Electronique Fondamentale, UMR CNRS 8622, Universite Paris Sud 11, 91405, Orsay (France); Messanvi, Agnes [Institut d' Electronique Fondamentale, UMR CNRS 8622, Universite Paris Sud 11, 91405, Orsay (France); Universite Grenoble Alpes, 38000, Grenoble (France); CEA, INAC-SP2M, ' ' Nanophysique et semiconducteurs' ' Group, 38000, Grenoble (France); Durand, Christophe; Eymery, Joel [Universite Grenoble Alpes, 38000, Grenoble (France); CEA, INAC-SP2M, ' ' Nanophysique et semiconducteurs' ' Group, 38000, Grenoble (France); Babichev, Andrey [ITMO University, 197101, St. Petersburg (Russian Federation); Ioffe Institute, Polytekhnicheskaya 26, 194021, St. Petersburg (Russian Federation)

    2016-04-15

    We report on the fabrication and characterization of single nitride nanowire visible-to-ultraviolet p-n photodetectors. Nitride nanowires containing 30 InGaN/GaN radial quantum wells with 18% indium fraction were grown by catalyst-free metal-organic vapour phase epitaxy. Single nanowires were contacted using optical lithography. As expected for a radial p-n junction, the current-voltage (I-V) curves of single wire detectors show a rectifying behavior in the dark and a photocurrent under illumination. The detectors present a response in the visible to UV spectral range starting from 2.8 eV. The peak responsivity is 0.17 A/W at 3.36 eV. The on-off switching time under square light pulses is found to be below 0.1 s. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Fabrication of multilayer nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Jasveer, E-mail: kaurjasveer89@gmail.com; Singh, Avtar; Kumar, Davinder [Department of Physics, Punjabi University Patiala, 147002, Punjab (India); Thakur, Anup; Kaur, Raminder, E-mail: raminder-k-saini@yahoo.com [Department of Basic and Applied Sciences, Punjabi University Patiala, 147002, Punjab (India)

    2016-05-06

    Multilayer nanowires were fabricated by potentiostate ectrodeposition template synthesis method into the pores of polycarbonate membrane. In present work layer by layer deposition of two different metals Ni and Cu in polycarbonate membrane having pore size of 600 nm were carried out. It is found that the growth of nanowires is not constant, it varies with deposition time. Scanning electron microscopy (SEM) is used to study the morphology of fabricated multilayer nanowires. An energy dispersive X-ray spectroscopy (EDS) results confirm the composition of multilayer nanowires. The result shows that multilayer nanowires formed is dense.

  20. Fabrication of multilayer nanowires

    International Nuclear Information System (INIS)

    Kaur, Jasveer; Singh, Avtar; Kumar, Davinder; Thakur, Anup; Kaur, Raminder

    2016-01-01

    Multilayer nanowires were fabricated by potentiostate ectrodeposition template synthesis method into the pores of polycarbonate membrane. In present work layer by layer deposition of two different metals Ni and Cu in polycarbonate membrane having pore size of 600 nm were carried out. It is found that the growth of nanowires is not constant, it varies with deposition time. Scanning electron microscopy (SEM) is used to study the morphology of fabricated multilayer nanowires. An energy dispersive X-ray spectroscopy (EDS) results confirm the composition of multilayer nanowires. The result shows that multilayer nanowires formed is dense.

  1. Nanowire Growth for Photovoltaics

    DEFF Research Database (Denmark)

    Holm, Jeppe Vilstrup

    Solar cells commercial success is based on an efficiency/cost calculation. Nanowire solar cells is one of the foremost candidates to implement third generation photo voltaics, which are both very efficient and cheap to produce. This thesis is about our progress towards commercial nanowire solar...... cells. Resonance effects between the light and nanowire causes an inherent concentration of the sunlight into the nanowires, and means that a sparse array of nanowires (less than 5% of the area) can absorb all the incoming light. The resonance effects, as well as a graded index of refraction, also traps...... the light. The concentration and light trapping means that single junction nanowire solar cells have a higher theoretical maximum efficiency than equivalent planar solar cells. We have demonstrated the built-in light concentration of nanowires, by growing, contacting and characterizing a solar cell...

  2. Dimensional effects in semiconductor nanowires; Dimensionseffekte in Halbleiternanodraehten

    Energy Technology Data Exchange (ETDEWEB)

    Stichtenoth, Daniel

    2008-06-23

    Nanomaterials show new physical properties, which are determined by their size and morphology. These new properties can be ascribed to the higher surface to volume ratio, to quantum size effects or to a form anisotropy. They may enable new technologies. The nanowires studied in this work have a diameter of 4 to 400 nm and a length up to 100 {mu}m. The semiconductor material used is mainly zinc oxide (ZnO), zinc sulfide (ZnS) and gallium arsenide (GaAs). All nanowires were synthesized according to the vapor liquid solid mechanism, which was originally postulated for the growth of silicon whiskers. Respective modifications for the growth of compound semiconductor nanowires are discussed. Detailed luminescence studies on ZnO nanowires with different diameters show pronounced size effects which can be attributed to the origins given above. Similar to bulk material, a tuning of the material properties is often essential for a further functionalization of the nanowires. This is typical realized by doping the source material. It becomes apparent, that a controlled doping of nanowires during the growth process is not successful. Here an alternative method is chosen: the doping after the growth by ion implantation. However, the doping by ion implantation goes always along with the creation of crystal defects. The defects have to be annihilated in order to reach an activation of th introduced dopants. At high ion fluences and ion masses the sputtering of surface atoms becomes more important. This results in a characteristic change in the morphology of the nanowires. In detail, the doping of ZnO and ZnS nanowires with color centers (manganese and rare earth elements) is demonstrated. Especially, the intra 3d luminescence of manganese implanted ZnS nanostructures shows a strong dependence of the nanowire diameter and morphology. This dependence can be described by expanding Foersters model (which describes an energy transfer to the color centers) by a dimensional parameter

  3. Physical origin of the incubation time of self-induced GaN nanowires

    International Nuclear Information System (INIS)

    Consonni, V.; Trampert, A.; Geelhaar, L.; Riechert, H.

    2011-01-01

    The nucleation process of self-induced GaN nanowires grown by molecular beam epitaxy has been investigated by reflection high-energy electron diffraction measurements. It is found that stable nuclei in the form of spherical cap-shaped islands develop only after an incubation time that is strongly dependent upon the growth conditions. Its evolution with the growth temperature and gallium rate has been described within standard island nucleation theory, revealing a nucleation energy of 4.9 ± 0.1 eV and a very small nucleus critical size. The consideration of the incubation time is critical for the control of the nanowire morphology.

  4. Surface-Passivated AlGaN Nanowires for Enhanced Luminescence of Ultraviolet Light Emitting Diodes

    KAUST Repository

    Sun, Haiding

    2017-12-19

    Spontaneously-grown, self-aligned AlGaN nanowire ultraviolet light emitting diodes still suffer from low efficiency partially because of the strong surface recombination caused by surface states, i.e., oxidized surface and high density surface states. Several surface passivation methods have been introduced to reduce surface non-radiative recombination by using complex and toxic chemicals. Here, we present an effective method to suppress such undesirable surface recombination of the AlGaN nanowires via diluted potassium hydroxide (KOH) solution; a commonly used chemical process in semiconductor fabrication which is barely used as surface passivation solution in self-assembled nitride-based nanowires. The transmission electron microscopy investigation on the samples reveals almost intact nanowire structures after the passivation process. We demonstrated an approximately 49.7% enhancement in the ultraviolet light output power after 30-s KOH treatment on AlGaN nanowires grown on titanium-coated silicon substrates. We attribute such a remarkable enhancement to the removal of the surface dangling bonds and oxidized nitrides (Ga-O or Al-O bonds) at the surface as we observe the change of the carrier lifetime before and after the passivation. Thus, our results highlight the possibility of employing this process for the realization of high performance nanowire UV emitters.

  5. 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

  6. A first principle study of band structure of III-nitride compounds

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, Rashid [Centre for High Energy Physics University of the Punjab, Lahore-54590 (Pakistan)]. E-mail: rasofi@hotmail.com; Akbarzadeh, H. [Department of Physics, Isfahan University of Technology, 841546 Isfahan (Iran, Islamic Republic of); Fazal-e-Aleem [Centre for High Energy Physics University of the Punjab, Lahore-54590 (Pakistan)

    2005-12-15

    The band structure of both phases, zinc-blende and wurtzite, of aluminum nitride, indium nitride and gallium nitride has been studied using computational methods. The study has been done using first principle full-potential linearized augmented plane wave (FP-LAPW) method, within the framework of density functional theory (DFT). For the exchange correlation potential, generalized gradient approximation (GGA) and an alternative form of GGA proposed by Engel and Vosko (GGA-EV) have been used. Results obtained for band structure of these compounds have been compared with experimental results as well as other first principle computations. Our results show a significant improvement over other theoretical work and are closer to the experimental data.

  7. Aluminium, gallium, indium and thallium

    International Nuclear Information System (INIS)

    Brown, Paul L.; Ekberg, Christian

    2016-01-01

    Aluminium can exist in a number of oxyhydroxide mineral phases including corundum, diaspore, boehmite and gibbsite. The stability constants at zero ionic strength reported for Al(OH) 3 (aq) vary linearly with respect to the inverse of absolute temperature. A full suite of thermodynamic parameters is available for all aluminium phases and hydrolysis species. Gallium hydrolyses to a greater extent than aluminium, with the onset of hydrolysis reactions occurring just above a pHof 1. In fact, even though aluminium has the smallest ionic radius of this series of metals, it has the weakest hydrolysis species and oxide/hydroxide phases.This is due to the presence of stabilising d-orbitals in the heavier metals, gallium, indium and thallium(III). There are few available data for the stability constants of indium(III) hydrolysis species. Of those that are available, the range in the proposed stability constants covers many orders of magnitude.

  8. Collector for recovering gallium from weapons plutonium

    International Nuclear Information System (INIS)

    Philip, C.V.; Anthony, R.G.; Chokkaram, S.

    1998-09-01

    Currently, the separation of gallium from weapons plutonium involves the use of aqueous processing using either solvent extraction of ion exchange. However, this process generates significant quantities of liquid radioactive wastes. A Thermally Induced Gallium Removal process, or TIGR, developed by researchers at Los Alamos National Laboratories, is a simpler alternative to aqueous processing. This research examined this process, and the behavior of gallium suboxide, a vapor that is swept away by passing hydrogen/argon over gallium trioxide/plutonium oxide heated at 1100 C during the TIGR process. Through experimental procedures, efforts were made to prevent the deposition of corrosive gallium onto furnace and vent surfaces. Experimental procedures included three options for gallium removal and collection: (1) collection of gallium suboxide through use of a cold finger; (2) collection by in situ air oxidation; and (3) collection of gallium on copper. Results conclude all three collection mechanisms are feasible. In addition, gallium trioxide exists in three crystalline forms, and each form was encountered during each experiment, and that each form will have a different reactivity

  9. Gallium and copper radiopharmaceutical chemistry

    International Nuclear Information System (INIS)

    Green, M.A.; John, E.K.; Barnhart, A.J.

    1990-01-01

    Several isotopes of gallium and copper exhibit nuclear properties that make them attractive for applications in nuclear medicine, most notably Ga-67, Ga-68, Cu-67 and Cu-62. Of these, gamma-emitting Ga-67 has historically found the greatest clinical use, based on the observation that tracer gallium(III) citrate rapidly produces Ga-67 transferrin upon intravenous injection and then slowly affords selective Ga-67 localization in sites of abscess and certain tumors. Copper-67 has received attention as a potential label for tissue-selective monoclonal antibodies, since its associated γ-photons can be used for external imaging and its β - -emissions could be used for radiation therapy. Positron-emitting gallium-68 and copper-62, being available from parent/daughter generator systems, have attracted interest as potential labels for radiopharmaceuticals used in positron emission tomography (PET) because they could reduce the dependence of this imaging technology on hospital-based cyclotrons. The 10 min. half-life of Cu-62 is particularly well-suited to the time frame of PET studies of tissue perfusion, an application for which Cu(II)-bis(thiosemicarbazone) derivatives appear promising. The 68 min. half-life of Ga-68 makes it appropriate for PET studies over longer imaging time spans

  10. From nanodiamond to nanowires.

    Energy Technology Data Exchange (ETDEWEB)

    Barnard, A.; Materials Science Division

    2005-01-01

    Recent advances in the fabrication and characterization of semiconductor and metallic nanowires are proving very successful in meeting the high expectations of nanotechnologists. Although the nanoscience surrounding sp{sup 3} bonded carbon nanotubes has continued to flourish over recent years the successful synthesis of the sp{sup 3} analogue, diamond nanowires, has been limited. This prompts questions as to whether diamond nanowires are fundamentally unstable. By applying knowledge obtained from examining the structural transformations in nanodiamond, a framework for analyzing the structure and stability of diamond nanowires may be established. One possible framework will be discussed here, supported by results of ab initio density functional theory calculations used to study the structural relaxation of nanodiamond and diamond nanowires. The results show that the structural stability and electronic properties of diamond nanowires are dependent on the surface morphology, crystallographic direction of the principal axis, and the degree of surface hydrogenation.

  11. 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....

  12. 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)

  13. Methanol, ethanol and hydrogen sensing using metal oxide and metal (TiO2–Pt) composite nanoclusters on GaN nanowires: a new route towards tailoring the selectivity of nanowire/nanocluster chemical sensors

    International Nuclear Information System (INIS)

    Aluri, Geetha S; Motayed, Abhishek; Davydov, Albert V; Oleshko, Vladimir P; Bertness, Kris A; Sanford, Norman A; Mulpuri, Rao V

    2012-01-01

    We demonstrate a new method for tailoring the selectivity of chemical sensors using semiconductor nanowires (NWs) decorated with metal and metal oxide multicomponent nanoclusters (NCs). Here we present the change of selectivity of titanium dioxide (TiO 2 ) nanocluster-coated gallium nitride (GaN) nanowire sensor devices on the addition of platinum (Pt) nanoclusters. The hybrid sensor devices were developed by fabricating two-terminal devices using individual GaN NWs followed by the deposition of TiO 2 and/or Pt nanoclusters (NCs) using the sputtering technique. This paper present the sensing characteristics of GaN/(TiO 2 –Pt) nanowire–nanocluster (NWNC) hybrids and GaN/(Pt) NWNC hybrids, and compare their selectivity with that of the previously reported GaN/TiO 2 sensors. The GaN/TiO 2 NWNC hybrids showed remarkable selectivity to benzene and related aromatic compounds, with no measurable response for other analytes. Addition of Pt NCs to GaN/TiO 2 sensors dramatically altered their sensing behavior, making them sensitive only to methanol, ethanol and hydrogen, but not to any other chemicals we tested. The GaN/(TiO 2 –Pt) hybrids were able to detect ethanol and methanol concentrations as low as 100 nmol mol −1 (ppb) in air in approximately 100 s, and hydrogen concentrations from 1 µmol mol −1 (ppm) to 1% in nitrogen in less than 60 s. However, GaN/Pt NWNC hybrids showed limited sensitivity only towards hydrogen and not towards any alcohols. All these hybrid sensors worked at room temperature and are photomodulated, i.e. they responded to analytes only in the presence of ultraviolet (UV) light. We propose a qualitative explanation based on the heat of adsorption, ionization energy and solvent polarity to explain the observed selectivity of the different hybrids. These results are significant from the standpoint of applications requiring room-temperature hydrogen sensing and sensitive alcohol monitoring. These results demonstrate the tremendous potential

  14. Ultrafast photocurrents and terahertz radiation in gallium arsenide and carbon based nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Prechtel, Hans Leonhard

    2011-08-15

    In this thesis we developed a measurement technique based on a common pump-probe scheme and coplanar stripline circuits that enables time-resolved photocurrent measurements of contacted nanosystems with a micrometer spatial and a picosecond time resolution. The measurement technique was applied to lowtemperature grown gallium arsenide (LT-GaAs), carbon nanotubes (CNTs), graphene, and p-doped gallium arsenide (GaAs) nanowires. The various mechanisms responsible for the generation of current pulses by pulsed laser excitation were reviewed. Furthermore the propagation of the resulting electromagnetic radiation along a coplanar stripline circuit was theoretically and numerically treated. The ultrafast photocurrent response of low-temperature grown GaAs was investigated. We found two photocurrent pulses in the time-resolved response. We showed that the first pulse is consistent with a displacement current pulse. We interpreted the second pulse to result from a transport current process. We further determined the velocity of the photo-generated charge carriers to exceed the drift, thermal and quantum velocities of single charge carriers. Hereby, we interpreted the transport current pulse to stem from an electron-hole plasma excitation. We demonstrated that the photocurrent response of CNTs comprises an ultrafast displacement current and a transport current. The data suggested that the photocurrent is finally terminated by the recombination lifetime of the charge carriers. To the best of our knowledge, we presented in this thesis the first recombination lifetime measurements of contacted, suspended, CVD grown CNT networks. In addition, we studied the ultrafast photocurrent dynamics of freely suspended graphene contacted by metal electrodes. At the graphene-metal interface, we demonstrated that built-in electric fields give rise to a photocurrent with a full-width-half-maximum of a few picoseconds and that a photo-thermoelectric effect generates a current with a decay time

  15. Emergence of Quantum Phase-Slip Behaviour in Superconducting NbN Nanowires: DC Electrical Transport and Fabrication Technologies

    Directory of Open Access Journals (Sweden)

    Nicolas G. N. Constantino

    2018-06-01

    Full Text Available Superconducting nanowires undergoing quantum phase-slips have potential for impact in electronic devices, with a high-accuracy quantum current standard among a possible toolbox of novel components. A key element of developing such technologies is to understand the requirements for, and control the production of, superconducting nanowires that undergo coherent quantum phase-slips. We present three fabrication technologies, based on using electron-beam lithography or neon focussed ion-beam lithography, for defining narrow superconducting nanowires, and have used these to create nanowires in niobium nitride with widths in the range of 20–250 nm. We present characterisation of the nanowires using DC electrical transport at temperatures down to 300 mK. We demonstrate that a range of different behaviours may be obtained in different nanowires, including bulk-like superconducting properties with critical-current features, the observation of phase-slip centres and the observation of zero conductance below a critical voltage, characteristic of coherent quantum phase-slips. We observe critical voltages up to 5 mV, an order of magnitude larger than other reports to date. The different prominence of quantum phase-slip effects in the various nanowires may be understood as arising from the differing importance of quantum fluctuations. Control of the nanowire properties will pave the way for routine fabrication of coherent quantum phase-slip nanowire devices for technology applications.

  16. 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

  17. 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

  18. Gallium Electromagnetic (GEM) Thrustor Concept and Design

    Science.gov (United States)

    Polzin, Kurt A.; Markusic, Thomas E.

    2006-01-01

    We describe the design of a new type of two-stage pulsed electromagnetic accelerator, the gallium electromagnetic (GEM) thruster. A schematic illustration of the GEM thruster concept is given in Fig. 1. In this concept, liquid gallium propellant is pumped into the first stage through a porous metal electrode using an electromagneticpump[l]. At a designated time, a pulsed discharge (approx.10-50 J) is initiated in the first stage, ablating the liquid gallium from the porous electrode surface and ejecting a dense thermal gallium plasma into the second state. The presence of the gallium plasma in the second stage serves to trigger the high-energy (approx.500 I), send-stage puke which provides the primary electromagnetic (j x B) acceleration.

  19. Microwave dynamics of high aspect ratio superconducting nanowires studied using self-resonance

    Science.gov (United States)

    Santavicca, Daniel F.; Adams, Jesse K.; Grant, Lierd E.; McCaughan, Adam N.; Berggren, Karl K.

    2016-06-01

    We study the microwave impedance of extremely high aspect ratio (length/width ≈ 5000) superconducting niobium nitride nanowires. The nanowires are fabricated in a compact meander geometry that is in series with the center conductor of a 50 Ω coplanar waveguide transmission line. The transmission coefficient of the sample is measured up to 20 GHz. At high frequency, a peak in the transmission coefficient is seen. Numerical simulations show that this is a half-wave resonance along the length of the nanowire, where the nanowire acts as a high impedance, slow wave transmission line. This resonance sets the upper frequency limit for these nanowires as inductive elements. Fitting simulations to the measured resonance enables a precise determination of the nanowire's complex sheet impedance at the resonance frequency. The real part is a measure of dissipation, while the imaginary part is dominated by kinetic inductance. We characterize the dependence of the sheet resistance and sheet inductance on both temperature and current and compare the results to recent theoretical predictions for disordered superconductors. These results can aid in the understanding of high frequency devices based on superconducting nanowires. They may also lead to the development of novel superconducting devices such as ultra-compact resonators and slow-wave structures.

  20. Nanowire Photovoltaic Devices

    Science.gov (United States)

    Forbes, David

    2015-01-01

    Firefly Technologies, in collaboration with the Rochester Institute of Technology and the University of Wisconsin-Madison, developed synthesis methods for highly strained nanowires. Two synthesis routes resulted in successful nanowire epitaxy: direct nucleation and growth on the substrate and a novel selective-epitaxy route based on nanolithography using diblock copolymers. The indium-arsenide (InAs) nanowires are implemented in situ within the epitaxy environment-a significant innovation relative to conventional semiconductor nanowire generation using ex situ gold nanoparticles. The introduction of these nanoscale features may enable an intermediate band solar cell while simultaneously increasing the effective absorption volume that can otherwise limit short-circuit current generated by thin quantized layers. The use of nanowires for photovoltaics decouples the absorption process from the current extraction process by virtue of the high aspect ratio. While no functional solar cells resulted from this effort, considerable fundamental understanding of the nanowire epitaxy kinetics and nanopatterning process was developed. This approach could, in principle, be an enabling technology for heterointegration of dissimilar materials. The technology also is applicable to virtual substrates. Incorporating nanowires onto a recrystallized germanium/metal foil substrate would potentially solve the problem of grain boundary shunting of generated carriers by restricting the cross-sectional area of the nanowire (tens of nanometers in diameter) to sizes smaller than the recrystallized grains (0.5 to 1 micron(exp 2).

  1. Functionalised Silver Nanowire Structures

    International Nuclear Information System (INIS)

    Andrew, Piers; Ilie, Adelina

    2007-01-01

    Crystalline silver nanowires 60-100 nm in diameter and tens of micrometres in length have been fabricated using a low temperature, solution synthesis technique. We explore the potential of this method to produce functional nanowire structures using two different strategies to attach active molecules to the nanowires: adsorption and displacement. Initially, as-produced silver nanowires capped with a uniaxial-growth-inducing polymer layer were functionalised by solution adsorption of a semiconducting conjugated polymer to generate fluorescent nanowire structures. The influence of nanowire surface chemistry was investigated by displacing the capping polymer with an alkanethiol self-assembled monolayer, followed by solution adsorption functionalisation. The success of molecular attachment was monitored by electron microscopy, absorption and fluorescence spectroscopy and confocal fluorescence microscopy. We examined how the optical properties of such adsorbed molecules are affected by the metallic nanowires, and observed transfer of excitation energy between dye molecules mediated by surface plasmons propagating on the nanowires. Non-contact dynamic force microscopy measurements were used to map the work-function of individual wires, revealing inhomogeneity of the polymer surface coverage

  2. Stability of Organic Nanowires

    DEFF Research Database (Denmark)

    Balzer, F.; Schiek, M.; Wallmann, I.

    2011-01-01

    The morphological stability of organic nanowires over time and under thermal load is of major importance for their use in any device. In this study the growth and stability of organic nanowires from a naphthyl end-capped thiophene grown by organic molecular beam deposition is investigated via ato...

  3. 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)

  4. Thermodynamics of gallium arsenide electrodeposition

    International Nuclear Information System (INIS)

    Perrault, G.G.

    1986-01-01

    Gallium Arsenide is well known as a very interesting compound for photoelectrical devices. Up to now, it has been prepared mostly by high temperature technology, and the authors considered that it might be of interest to set up an electrodeposition technique suitable to prepare thin layers of this compound. A reaction sequence similar to the one observed for Cadmium Sulfide or Cadmium Telluride could be considered. In these cases, the metal chalcogenide is obtained from the precipitation of the metal ions dissolved in the solutions by the reduction product of the metalloidic compound

  5. Silicon nitride nanosieve membrane

    NARCIS (Netherlands)

    Tong, D.H.; Jansen, Henricus V.; Gadgil, V.J.; Bostan, C.G.; Berenschot, Johan W.; van Rijn, C.J.M.; Elwenspoek, Michael Curt

    2004-01-01

    An array of very uniform cylindrical nanopores with a pore diameter as small as 25 nm has been fabricated in an ultrathin micromachined silicon nitride membrane using focused ion beam (FIB) etching. The pore size of this nanosieve membrane was further reduced to below 10 nm by coating it with

  6. Resonant tunnelling features in a suspended silicon nanowire single-hole transistor

    Energy Technology Data Exchange (ETDEWEB)

    Llobet, Jordi; Pérez-Murano, Francesc, E-mail: francesc.perez@csic.es, E-mail: z.durrani@imperial.ac.uk [Institut de Microelectrònica de Barcelona (IMB-CNM CSIC), Campus UAB, E-08193 Bellaterra, Catalonia (Spain); Krali, Emiljana; Wang, Chen; Jones, Mervyn E.; Durrani, Zahid A. K., E-mail: francesc.perez@csic.es, E-mail: z.durrani@imperial.ac.uk [Department of Electrical and Electronic Engineering, Imperial College London, South Kensington, London SW7 2AZ (United Kingdom); Arbiol, Jordi [Institució Catalana de Recerca i Estudis Avançats (ICREA) and Institut Català de Nanociència i Nanotecnologia (ICN2), Campus UAB, 08193 Bellaterra, Catalonia (Spain); CELLS-ALBA Synchrotron Light Facility, 08290 Cerdanyola, Catalonia (Spain)

    2015-11-30

    Suspended silicon nanowires have significant potential for a broad spectrum of device applications. A suspended p-type Si nanowire incorporating Si nanocrystal quantum dots has been used to form a single-hole transistor. Transistor fabrication uses a novel and rapid process, based on focused gallium ion beam exposure and anisotropic wet etching, generating <10 nm nanocrystals inside suspended Si nanowires. Electrical characteristics at 10 K show Coulomb diamonds with charging energy ∼27 meV, associated with a single dominant nanocrystal. Resonant tunnelling features with energy spacing ∼10 meV are observed, parallel to both diamond edges. These may be associated either with excited states or hole–acoustic phonon interactions, in the nanocrystal. In the latter case, the energy spacing corresponds well with reported Raman spectroscopy results and phonon spectra calculations.

  7. Resonant tunnelling features in a suspended silicon nanowire single-hole transistor

    International Nuclear Information System (INIS)

    Llobet, Jordi; Pérez-Murano, Francesc; Krali, Emiljana; Wang, Chen; Jones, Mervyn E.; Durrani, Zahid A. K.; Arbiol, Jordi

    2015-01-01

    Suspended silicon nanowires have significant potential for a broad spectrum of device applications. A suspended p-type Si nanowire incorporating Si nanocrystal quantum dots has been used to form a single-hole transistor. Transistor fabrication uses a novel and rapid process, based on focused gallium ion beam exposure and anisotropic wet etching, generating <10 nm nanocrystals inside suspended Si nanowires. Electrical characteristics at 10 K show Coulomb diamonds with charging energy ∼27 meV, associated with a single dominant nanocrystal. Resonant tunnelling features with energy spacing ∼10 meV are observed, parallel to both diamond edges. These may be associated either with excited states or hole–acoustic phonon interactions, in the nanocrystal. In the latter case, the energy spacing corresponds well with reported Raman spectroscopy results and phonon spectra calculations

  8. 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

  9. 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.

  10. 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.

  11. Ga2O3 nanowires preparation at atmospheric pressure

    Directory of Open Access Journals (Sweden)

    Korbutowicz R.

    2017-07-01

    Full Text Available An attempt has been undertaken to produce gallium oxide nanowires by thermal synthesis from metallic gallium source at atmospheric pressure. Silicon substrates of (1 0 0 and (1 1 1 orientation with and without silicon oxide layers (0.5 μm were used as support. Evaporated thin gold films were deposited on the top of those silicon carriers as a catalytic agent. After thermal treatment by Rapid Thermal Processing RTP (at various temperatures and times, which was applied to make small Au islands with the diameters of about several tens of nanometers, the substrate surfaces were observed by SEM. The Ga2O3 syntheses were made at various conditions: time, temperature and gas mixture were changed. As a result, monoclinic gallium oxide β-Ga2O3 nanostructures with dominant [1 1 1] and [0 0 2] growth directions were grown. The obtained nanostructures of several tens micrometers length were studied by SEM, PL and X-ray methods.

  12. Gallium-67 scintigraphy in borderline lepromatous leprosy

    International Nuclear Information System (INIS)

    Mouratidis, B.; Lomas, F.E.

    1993-01-01

    A middle aged woman with a pyrexia of unknown origin was shown to have borderline lepromatous leprosy. Early gallium-67 scintigraphy demonstrated increased uptake in the subcutaneous tissues of the face and thighs. As a result of these findings skin biopsy was obtained from the right thigh which gave a diagnosis of borderline lepromatous leprosy. The authors have been unable to find other reports of gallium-67 scintigraphy in leprosy but the pattern of gallium-67 distribution should suggest the diagnosis. 5 refs., 1 fig

  13. Nitride-based quantum structures and devices on modified GaN substrates

    International Nuclear Information System (INIS)

    Perlin, Piotr; Leszczynski, Mike; Grzegory, Izabella; Franssen, Gijs; Targowski, Grzegorz; Krysko, Marcin; Nowak, Grzegorz; Litwin-Staszewska, Elzbieta; Piotrzkowski, Ryszard; Lucznik, Bolek; Suski, Tadek; Szeszko, Justyna; Czernecki, R.; Grzanka, Szymon; Jakiela, Rafal; Albrecht, Martin

    2009-01-01

    We have studied the properties of InGaN layers and quantum wells grown on gallium nitride substrates with intentional surface misorientation with respect to its crystalline c-axis. Misorientation varied in the range from 0 up to 2 degree. The indium content was changed by using the different growth temperature (between 750 C and 820 C) during metalorganic vapor phase epitaxy. With increasing misorientation angle the average indium content decreased significantly. This effect was accompanied by the strong increase of the emission line bandwidth suggesting more pronounced indium segregation. The results of cathodoluminescence measurements show that these effects correspond to different number of atomic steps/terraces existing on the surface of gallium nitride substrate. Very interesting result is also demonstrated concerning p-type GaN layers. With increasing misorientation, the free hole density drastically increases above 10 18 cm -3 . This improvement in p-type doping is not related to the increased Mg concentration but to the reduction in the compensating donor density. Using this advantage we demonstrate nitride light emitters with improved electrical properties. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Improving emission uniformity and linearizing band dispersion in nanowire arrays using quasi-aperiodicity

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, P. Duke [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Univ. of Southern California, Los Angeles, CA (United States). Ming Hsieh Dept. of Electrical Engineering; Koleske, Daniel D. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Povinelli, Michelle L. [Univ. of Southern California, Los Angeles, CA (United States). Ming Hsieh Dept. of Electrical Engineering; Subramania, Ganapathi [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)

    2017-10-01

    For this study, we experimentally investigate a new class of quasi-aperiodic structures for improving the emission pattern in nanowire arrays. Efficient normal emission, as well as lasing, can be obtained from III-nitride photonic crystal (PhC) nanowire arrays that utilize slow group velocity modes near the Γ-point in reciprocal space. However, due to symmetry considerations, the emitted far-field pattern of such modes are often ‘donut’-like. Many applications, including lighting for displays or lasers, require a more uniform beam profile in the far-field. Previous work has improved far-field beam uniformity of uncoupled modes by changing the shape of the emitting structure. However, in nanowire systems, the shape of nanowires cannot always be arbitrarily changed due to growth or etch considerations. Here, we investigate breaking symmetry by instead changing the position of emitters. Using a quasi-aperiodic geometry, which changes the emitter position within a photonic crystal supercell (2x2), we are able to linearize the photonic bandstructure near the Γ-point and greatly improve emitted far-field uniformity. We realize the III-nitride nanowires structures using a top-down fabrication procedure that produces nanowires with smooth, vertical sidewalls. Comparison of room-temperature micro-photoluminescence (µ-PL) measurements between periodic and quasi-aperiodic nanowire arrays reveal resonances in each structure, with the simple periodic structure producing a donut beam in the emitted far-field and the quasi-aperiodic structure producing a uniform Gaussian-like beam. We investigate the input pump power vs. output intensity in both systems and observe the simple periodic array exhibiting a non-linear relationship, indicative of lasing. We believe that the quasi-aperiodic approach studied here provides an alternate and promising strategy for shaping the emission pattern of nanoemitter systems.

  15. Facile Formation of High-quality InGaN/GaN Quantum-disks-in-Nanowires on Bulk-Metal Substrates for High-power Light-emitters

    KAUST Repository

    Zhao, Chao; Ng, Tien Khee; Wei, Nini; Prabaswara, Aditya; Alias, Mohd Sharizal; Janjua, Bilal; Shen, Chao; Ooi, Boon S.

    2016-01-01

    High-quality nitride materials grown on scalable and low-cost metallic substrates are considerably attractive for high-power light emitters. We demonstrate here, for the first time, the high-power red (705 nm) InGaN/GaN quantum-disks (Qdisks)-in-nanowire light-emitting diodes (LEDs) self-assembled directly on metal-substrate. The LEDs exhibited a low turn-on voltage of ~2 V without efficiency droop up to injection current of 500 mA (1.6 kA/cm2) at ~5 V. This is achieved through the direct growth and optimization of high-quality nanowires on titanium (Ti) coated bulk polycrystalline-molybdenum (Mo) substrates. We performed extensive studies on the growth mechanisms, obtained high-crystal-quality nanowires, and confirmed the epitaxial relationship between the cubic titanium nitride (TiN) transition layer and the hexagonal nanowires. The growth of nanowires on all-metal stack of TiN/Ti/Mo enables simultaneous implementation of n-metal contact, reflector and heat-sink, which greatly simplifies the fabrication process of high-power light emitters. Our work ushers in a practical platform for high-power nanowires light emitters, providing versatile solutions for multiple cross-disciplinary applications that are greatly enhanced by leveraging on the chemical stability of nitride materials, large specific surface of nanowires, chemical lift-off ready layer structures, and reusable Mo substrates.

  16. Facile Formation of High-quality InGaN/GaN Quantum-disks-in-Nanowires on Bulk-Metal Substrates for High-power Light-emitters

    KAUST Repository

    Zhao, Chao

    2016-01-08

    High-quality nitride materials grown on scalable and low-cost metallic substrates are considerably attractive for high-power light emitters. We demonstrate here, for the first time, the high-power red (705 nm) InGaN/GaN quantum-disks (Qdisks)-in-nanowire light-emitting diodes (LEDs) self-assembled directly on metal-substrate. The LEDs exhibited a low turn-on voltage of ~2 V without efficiency droop up to injection current of 500 mA (1.6 kA/cm2) at ~5 V. This is achieved through the direct growth and optimization of high-quality nanowires on titanium (Ti) coated bulk polycrystalline-molybdenum (Mo) substrates. We performed extensive studies on the growth mechanisms, obtained high-crystal-quality nanowires, and confirmed the epitaxial relationship between the cubic titanium nitride (TiN) transition layer and the hexagonal nanowires. The growth of nanowires on all-metal stack of TiN/Ti/Mo enables simultaneous implementation of n-metal contact, reflector and heat-sink, which greatly simplifies the fabrication process of high-power light emitters. Our work ushers in a practical platform for high-power nanowires light emitters, providing versatile solutions for multiple cross-disciplinary applications that are greatly enhanced by leveraging on the chemical stability of nitride materials, large specific surface of nanowires, chemical lift-off ready layer structures, and reusable Mo substrates.

  17. Silicon nanowire hybrid photovoltaics

    KAUST Repository

    Garnett, Erik C.; Peters, Craig; Brongersma, Mark; Cui, Yi; McGehee, Mike

    2010-01-01

    Silicon nanowire Schottky junction solar cells have been fabricated using n-type silicon nanowire arrays and a spin-coated conductive polymer (PEDOT). The polymer Schottky junction cells show superior surface passivation and open-circuit voltages compared to standard diffused junction cells with native oxide surfaces. External quantum efficiencies up to 88% were measured for these silicon nanowire/PEDOT solar cells further demonstrating excellent surface passivation. This process avoids high temperature processes which allows for low-cost substrates to be used. © 2010 IEEE.

  18. Silicon nanowire hybrid photovoltaics

    KAUST Repository

    Garnett, Erik C.

    2010-06-01

    Silicon nanowire Schottky junction solar cells have been fabricated using n-type silicon nanowire arrays and a spin-coated conductive polymer (PEDOT). The polymer Schottky junction cells show superior surface passivation and open-circuit voltages compared to standard diffused junction cells with native oxide surfaces. External quantum efficiencies up to 88% were measured for these silicon nanowire/PEDOT solar cells further demonstrating excellent surface passivation. This process avoids high temperature processes which allows for low-cost substrates to be used. © 2010 IEEE.

  19. Nitriding of high speed steel

    International Nuclear Information System (INIS)

    Doyle, E.D.; Pagon, A.M.; Hubbard, P.; Dowey, S.J.; Pilkington, A.; McCulloch, D.G.; Latham, K.; DuPlessis, J.

    2010-01-01

    Current practice when nitriding HSS cutting tools is to avoid embrittlement of the cutting edge by limiting the depth of the diffusion zone. This is accomplished by reducing the nitriding time and temperature and eliminating any compound layer formation. However, in many applications there is an argument for generating a compound layer with beneficial tribological properties. In this investigation results are presented of a metallographic, XRD and XPS analysis of nitrided surface layers generated using active screen plasma nitriding and reactive vapour deposition using cathodic arc. These results are discussed in the context of built up edge formation observed while machining inside a scanning electron microscope. (author)

  20. Controlling the physical parameters of crystalline CIGS nanowires for use in superstrate configuration using vapor phase epitaxy

    Science.gov (United States)

    Lee, Dongjin; Jeon, H. C.; Kang, T. W.; Kumar, Sunil

    2018-03-01

    Indium tin oxide (ITO) is a suitable candidate for smart windows and bifacial semi-transparent solar cell applications. In this study, highly crystalline CuInGaSe2 (CIGS) nanowires were successfully grown by horizontal-type vapor phase epitaxy on an ITO substrate. Length, diameter, and density of the nanowires were studied by varying the growth temperature (500, 520, and 560 °C), time (3.5, 6.5, and 9.5 h), and type of catalyst (In, Au, and Ga). Length, diameter, and density of the nanowires were found to be highly dependent on the growth conditions. At an optimized growth period and temperature of 3.5 h and 520 °C, respectively, the length and diameter of the nanowires were found to increase when grown in a catalyst-free environment. However, the density of the nanowires was found to be higher while using a catalyst during growth. Even in a catalyst-free environment, an Indium cluster formed at the bottom of the nanowires. The source of these nanowires is believed to be Indium from the ITO substrate which was observed in the EDS measurement. TEM-based EDS and line EDS indicated that the nanowires are made up of CIGS material with a very low Gallium content. XRD measurements also show the appearance of wurtzite CIS nanowires grown on ITO in addition to the chalcopyrite phase. PL spectroscopy was done to see the near-band-edge emission for finding band-to-band optical transition in this material. Optical response of the CIGS nanowire network was also studied to see the photovoltaic effect. This work creates opportunities for making real solar cell devices in superstrate configuration.

  1. Defects in dilute nitrides

    International Nuclear Information System (INIS)

    Chen, W.M.; Buyanova, I.A.; Tu, C.W.; Yonezu, H.

    2005-01-01

    We provide a brief review our recent results from optically detected magnetic resonance studies of grown-in non-radiative defects in dilute nitrides, i.e. Ga(In)NAs and Ga(Al,In)NP. Defect complexes involving intrinsic defects such as As Ga antisites and Ga i self interstitials were positively identified.Effects of growth conditions, chemical compositions and post-growth treatments on formation of the defects are closely examined. These grown-in defects are shown to play an important role in non-radiative carrier recombination and thus in degrading optical quality of the alloys, harmful to performance of potential optoelectronic and photonic devices based on these dilute nitrides. (author)

  2. 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

  3. 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

  4. NIM Realization of the Gallium Triple Point

    Science.gov (United States)

    Xiaoke, Yan; Ping, Qiu; Yuning, Duan; Yongmei, Qu

    2003-09-01

    In the last three years (1999 to 2001), the gallium triple-point cell has been successfully developed, and much corresponding research has been carried out at the National Institute of Metrology (NIM), Beijing, China. This paper presents the cell design, apparatus and procedure for realizing the gallium triple point, and presents studies on the different freezing methods. The reproducibility is 0.03 mK, and the expanded uncertainty of realization of the gallium triple point is evaluated to be 0.17 mK (p=0.99, k=2.9). Also, the reproducibility of the gallium triple point was compared with that of the triple point of water.

  5. Glutathione role in gallium induced toxicity

    African Journals Online (AJOL)

    Asim

    2012-01-26

    Jan 26, 2012 ... 1Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Gomal University, D.I. Khan, ... Decrease in GSH level was dependant on gallium nitrate concentration. .... This 2 ml mixture sample was centrifuged at 1000.

  6. 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.

  7. 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 ...

  8. Molecular Beam Epitaxy-Grown InGaN Nanowires and Nanomushrooms for Solid State Lighting

    KAUST Repository

    Gasim, Anwar A.

    2012-05-01

    InGaN is a promising semiconductor for solid state lighting thanks to its bandgap which spans the entire visible regime of the electromagnetic spectrum. InGaN is grown heteroepitaxially due to the absence of a native substrate; however, this results in a strained film and a high dislocation density—two effects that have been associated with efficiency droop, which is the disastrous drop in efficiency of a light-emitting diode (LED) as the input current increases. Heteroepitaxially grown nanowires have recently attracted great interest due to their property of eliminating the detrimental effects of the lattice mismatch and the corollary efficiency droop. In this study, InGaN nanowires were grown on a low-cost Si (111) substrate via molecular beam epitaxy. Unique nanostructures, taking the form of mushrooms, have been observed in localized regions on the samples. These nanomushrooms consist of a nanowire body with a wide cap on top. Photoluminescence characterization revealed that the nanowires emit violet-blue, whilst the nanomushrooms emit a broad yellow-orange-red luminescence. The simultaneous emission from the nanowires and nanomushrooms forms white light. Structural characterization of a single nanomushroom via transmission electron microscopy revealed a simultaneous increase in indium and decrease in gallium at the interface between the body and the cap. Furthermore, the cap itself was found to be indium-rich, confirming it as the source of the longer wavelength yellow-orange-red luminescence. It is believed that the nanomushroom cap formed as a consequence of the saturation of growth on the c-plane of the nanowire. It is proposed that the formation of an indium droplet on the tip of the nanowire saturated growth on the c-plane, forcing the indium and gallium adatoms to incorporate on the sidewall m-planes instead, but only at the nanowire tip. This resulted in the formation of a mushroom-like cap on the tip. How and why the indium droplets formed is not

  9. 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

  10. Metal Contacts to Gallium Arsenide.

    Science.gov (United States)

    Ren, Fan

    1991-07-01

    While various high performance devices fabricated from the gallium arsenide (GaAs) and related materials have generated considerable interest, metallization are fundamental components to all semiconductor devices and integrated circuits. The essential roles of metallization systems are providing the desired electrical paths between the active region of the semiconductor and the external circuits through the metal interconnections and contacts. In this work, in-situ clean of native oxide, high temperature n-type, low temperature n-type and low temperature p-type ohmic metal systems have been studied. Argon ion mill was used to remove the native oxide prior to metal deposition. For high temperature process n-type GaAs ohmic contacts, Tungsten (W) and Tungsten Silicide (WSi) were used with an epitaxial grown graded Indium Gallium Arsenide (InGaAs) layer (0.2 eV) on GaAs. In addition, refractory metals, Molybdenum (Mo), was incorporated in the Gold-Germanium (AuGe) based on n-type GaAs ohmic contacts to replace conventional silver as barrier to prevent the reaction between ohmic metal and chlorine based plasma as well as the ohmic metallization intermixing which degrades the device performance. Finally, Indium/Gold-Beryllium (In/Au-Be) alloy has been developed as an ohmic contact for p-type GaAs to reduce the contact resistance. The Fermi-level pinning of GaAs has been dominated by the surface states. The Schottky barrier height of metal contacts are about 0.8 V regardless of the metal systems. By using p-n junction approach, barrier height of pulsed C-doped layers was achieved as high as 1.4 V. Arsenic implantation into GaAs method was also used to enhance the barrier height of 1.6 V.

  11. Nanotubes and nanowires

    Indian Academy of Sciences (India)

    Unknown

    junction nanotubes by the pyrolysis of appropriate organic precursors. ... By making use of carbon nanotubes, nanowires of metals, metal ..... The use of activated carbon in place of ..... required for the complete removal of the carbon template.

  12. Porous Silicon Nanowires

    Science.gov (United States)

    Qu, Yongquan; Zhou, Hailong; Duan, Xiangfeng

    2011-01-01

    In this minreview, we summarize recent progress in the synthesis, properties and applications of a new type of one-dimensional nanostructures — single crystalline porous silicon nanowires. The growth of porous silicon nanowires starting from both p- and n-type Si wafers with a variety of dopant concentrations can be achieved through either one-step or two-step reactions. The mechanistic studies indicate the dopant concentration of Si wafers, oxidizer concentration, etching time and temperature can affect the morphology of the as-etched silicon nanowires. The porous silicon nanowires are both optically and electronically active and have been explored for potential applications in diverse areas including photocatalysis, lithium ion battery, gas sensor and drug delivery. PMID:21869999

  13. 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...

  14. Biofunctionalized Magnetic Nanowires

    KAUST Repository

    Kosel, Jurgen

    2013-12-19

    Magnetic nanowires can be used as an alternative method overcoming the limitations of current cancer treatments that lack specificity and are highly cytotoxic. Nanowires are developed so that they selectively attach to cancer cells via antibodies, potentially destroying them when a magnetic field induces their vibration. This will transmit a mechanical force to the targeted cells, which is expected to induce apoptosis on the cancer cells.

  15. Biofunctionalized Magnetic Nanowires

    KAUST Repository

    Kosel, Jü rgen; Ravasi, Timothy; Contreras Gerenas, Maria Fernanda

    2013-01-01

    Magnetic nanowires can be used as an alternative method overcoming the limitations of current cancer treatments that lack specificity and are highly cytotoxic. Nanowires are developed so that they selectively attach to cancer cells via antibodies, potentially destroying them when a magnetic field induces their vibration. This will transmit a mechanical force to the targeted cells, which is expected to induce apoptosis on the cancer cells.

  16. Growth, structure and phase transitions of epitaxial nanowires of III-V semiconductors

    International Nuclear Information System (INIS)

    Glas, F; Patriarche, G; Harmand, J C

    2010-01-01

    We review and illustrate the impact of TEM on the study of nanowires of non-nitride III-V semiconductors, with particular emphasis on the understanding of the thermodynamics and kinetics of their formation assisted by nano-sized catalyst particles. Besides providing basic information about the morphology of the nanowires and their growth rate as a function of diameter, TEM offers insights into the peculiar crystalline structure that they adopt. We discuss the formation of the unusual wurtzite hexagonal crystalline phase and that of planar stacking defects in these nanowires and show that they are kinetically controlled. We also demonstrate the transformation of wurtzite into cubic sphalerite upon epitaxial burying of the nanowires. Nanowires are particularly interesting in that they allow the fabrication of precisely positioned quantum dots with well-defined geometries. In this respect, we discuss the formation of strained quantum-size inclusions in nanowires, their critical dimensions and the kinetic and thermodynamic factors governing the changes of the crystalline structure that sometimes occur around a hetero-interface.

  17. Nanowire structures and electrical devices

    Science.gov (United States)

    Bezryadin, Alexey; Remeika, Mikas

    2010-07-06

    The present invention provides structures and devices comprising conductive segments and conductance constricting segments of a nanowire, such as metallic, superconducting or semiconducting nanowire. The present invention provides structures and devices comprising conductive nanowire segments and conductance constricting nanowire segments having accurately selected phases including crystalline and amorphous states, compositions, morphologies and physical dimensions, including selected cross sectional dimensions, shapes and lengths along the length of a nanowire. Further, the present invention provides methods of processing nanowires capable of patterning a nanowire to form a plurality of conductance constricting segments having selected positions along the length of a nanowire, including conductance constricting segments having reduced cross sectional dimensions and conductance constricting segments comprising one or more insulating materials such as metal oxides.

  18. 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.

  19. LDA+U and tight-binding electronic structure of InN nanowires

    Science.gov (United States)

    Molina-Sánchez, A.; García-Cristóbal, A.; Cantarero, A.; Terentjevs, A.; Cicero, G.

    2010-10-01

    In this paper we employ a combined ab initio and tight-binding approach to obtain the electronic and optical properties of hydrogenated Indium nitride (InN) nanowires. We first discuss InN band structure for the wurtzite structure calculated at the LDA+U level and use this information to extract the parameters needed for an empirical tight-binging implementation. These parameters are then employed to calculate the electronic and optical properties of InN nanowires in a diameter range that would not be affordable by ab initio techniques. The reliability of the large nanowires results is assessed by explicitly comparing the electronic structure of a small diameter wire studied both at LDA+U and tight-binding level.

  20. Effects of Precursor-Substrate Distances on the Growth of GaN Nanowires

    Directory of Open Access Journals (Sweden)

    Hongbin Cheng

    2015-01-01

    Full Text Available GaN nanowires were synthesized through the Ni-catalyzed chemical vapor deposition (CVD method using Ga2O3/GaN mixtures as gallium sources, and precursor-substrate distances were investigated as the important factor for the growth of GaN nanowires. The microstructure, composition, and photoluminescence property were characterized by X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy, and photoluminescence spectra. The results showed that single crystalline GaN nanowires with the diameter of about 90 nm and the length up to tens of micrometers had been grown thickly across Si (100 substrates with uniform density. Moreover, the variations of the GaN nanowire morphology, density, and size were largely attributed to substrate positions which would influence Ga precursor density in the carrier gas, the saturation degree of gaseous reactants, and the catalyst activity, respectively, in the fabrication of GaN nanowires by the vapour liquid solid mechanism.

  1. Additive-assisted synthesis of boride, carbide, and nitride micro/nanocrystals

    International Nuclear Information System (INIS)

    Chen, Bo; Yang, Lishan; Heng, Hua; Chen, Jingzhong; Zhang, Linfei; Xu, Liqiang; Qian, Yitai; Yang, Jian

    2012-01-01

    General and simple methods for the syntheses of borides, carbides and nitrides are highly desirable, since those materials have unique physical properties and promising applications. Here, a series of boride (TiB 2 , ZrB 2 , NbB 2 , CeB 6 , PrB 6 , SmB 6 , EuB 6 , LaB 6 ), carbide (SiC, TiC, NbC, WC) and nitride (TiN, BN, AlN, MgSiN 2 , VN) micro/nanocrystals were prepared from related oxides and amorphous boron/active carbon/NaN 3 with the assistance of metallic Na and elemental S. In-situ temperature monitoring showed that the reaction temperature could increase quickly to ∼850 °C, once the autoclave was heated to 100 °C. Such a rapid temperature increase was attributed to the intense exothermic reaction between Na and S, which assisted the formation of borides, carbides and nitrides. The as-obtained products were characterized by XRD, SEM, TEM, and HRTEM techniques. Results in this report will greatly benefit the future extension of this approach to other compounds. - Graphical abstract: An additive-assisted approach is successfully developed for the syntheses of borides, carbides and nitrides micro/nanocrystals with the assistance of the exothermic reaction between Na and S. Highlights: ► An additive-assisted synthesis strategy is developed for a number of borides, carbides and nitrides. ► The reaction mechanism is demonstrated by the case of SiC nanowires. ► The formation of SiC nanowires is initiated by the exothermic reaction of Na and S.

  2. 67Gallium • the D,etection and Localization

    African Journals Online (AJOL)

    1971-12-11

    Dec 11, 1971 ... gallium and its compounds was first aroused when it was noted that this element is contained .... MATERIALS AND METHODS. ;;'Gallium citrate was .... another in a patient with a pathological fracture of the right humerus that ...

  3. 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.

  4. Normal vibrations in gallium arsenide

    International Nuclear Information System (INIS)

    Dolling, G.; Waugh, J.L.T.

    1964-01-01

    The triple axis crystal spectrometer at Chalk River has been used to observe coherent slow neutron scattering from a single crystal of pure gallium arsenide at 296 o K. The frequencies of normal modes of vibration propagating in the [ζ00], (ζζζ], and (0ζζ] crystal directions have been determined with a precision of between 1 and 2·5 per cent. A limited number of normal modes have also been studied at 95 and 184 o K. Considerable difficulty was experienced in obtaining welt resolved neutron peaks corresponding to the two non-degenerate optic modes for very small wave-vector, particularly at 296 o K. However, from a comparison of results obtained under various experimental conditions at several different points in reciprocal space, frequencies (units 10 12 c/s) for these modes (at 296 o K) have been assigned: T 8·02±0·08 and L 8·55±02. Other specific normal modes, with their measured frequencies are (a) (1,0,0): TO 7·56 ± 008, TA 2·36 ± 0·015, LO 7·22 ± 0·15, LA 6·80 ± 0·06; (b) (0·5, 0·5, 0·5): TO 7·84 ± 0·12, TA 1·86 ± 0·02, LO 7·15 ± 0·07, LA 6·26 ± 0·10; (c) (0, 0·65, 0·65): optic 8·08 ±0·13, 7·54 ± 0·12 and 6·57 ± 0·11, acoustic 5·58 ± 0·08, 3·42 · 0·06 and 2·36 ± 004. These results are generally slightly lower than the corresponding frequencies for germanium. An analysis in terms of various modifications of the dipole approximation model has been carried out. A feature of this analysis is that the charge on the gallium atom appears to be very small, about +0·04 e. The frequency distribution function has been derived from one of the force models. (author)

  5. Normal vibrations in gallium arsenide

    Energy Technology Data Exchange (ETDEWEB)

    Dolling, G; Waugh, J L T

    1964-07-01

    The triple axis crystal spectrometer at Chalk River has been used to observe coherent slow neutron scattering from a single crystal of pure gallium arsenide at 296{sup o}K. The frequencies of normal modes of vibration propagating in the [{zeta}00], ({zeta}{zeta}{zeta}], and (0{zeta}{zeta}] crystal directions have been determined with a precision of between 1 and 2{center_dot}5 per cent. A limited number of normal modes have also been studied at 95 and 184{sup o}K. Considerable difficulty was experienced in obtaining welt resolved neutron peaks corresponding to the two non-degenerate optic modes for very small wave-vector, particularly at 296{sup o}K. However, from a comparison of results obtained under various experimental conditions at several different points in reciprocal space, frequencies (units 10{sup 12} c/s) for these modes (at 296{sup o}K) have been assigned: T 8{center_dot}02{+-}0{center_dot}08 and L 8{center_dot}55{+-}02. Other specific normal modes, with their measured frequencies are (a) (1,0,0): TO 7{center_dot}56 {+-} 008, TA 2{center_dot}36 {+-} 0{center_dot}015, LO 7{center_dot}22 {+-} 0{center_dot}15, LA 6{center_dot}80 {+-} 0{center_dot}06; (b) (0{center_dot}5, 0{center_dot}5, 0{center_dot}5): TO 7{center_dot}84 {+-} 0{center_dot}12, TA 1{center_dot}86 {+-} 0{center_dot}02, LO 7{center_dot}15 {+-} 0{center_dot}07, LA 6{center_dot}26 {+-} 0{center_dot}10; (c) (0, 0{center_dot}65, 0{center_dot}65): optic 8{center_dot}08 {+-}0{center_dot}13, 7{center_dot}54 {+-} 0{center_dot}12 and 6{center_dot}57 {+-} 0{center_dot}11, acoustic 5{center_dot}58 {+-} 0{center_dot}08, 3{center_dot}42 {center_dot} 0{center_dot}06 and 2{center_dot}36 {+-} 004. These results are generally slightly lower than the corresponding frequencies for germanium. An analysis in terms of various modifications of the dipole approximation model has been carried out. A feature of this analysis is that the charge on the gallium atom appears to be very small, about +0{center_dot}04 e. The

  6. Hot pressing of uranium nitride and mixed uranium plutonium nitride

    International Nuclear Information System (INIS)

    Chang, J.Y.

    1975-01-01

    The hot pressing characteristics of uranium nitride and mixed uranium plutonium nitride were studied. The utilization of computer programs together with the experimental technique developed in the present study may serve as a useful purpose of prediction and fabrication of advanced reactor fuel and other high temperature ceramic materials for the future. The densification of nitrides follow closely with a plastic flow theory expressed as: d rho/ dt = A/T(t) (1-rho) [1/1-(1-rho)/sup 2/3/ + B1n (1-rho)] The coefficients, A and B, were obtained from experiment and computer curve fitting. (8 figures) (U.S.)

  7. Highly effective field-effect mobility amorphous InGaZnO TFT mediated by directional silver nanowire arrays.

    Science.gov (United States)

    Liu, Hung-Chuan; Lai, Yi-Chun; Lai, Chih-Chung; Wu, Bing-Shu; Zan, Hsiao-Wen; Yu, Peichen; Chueh, Yu-Lun; Tsai, Chuang-Chuang

    2015-01-14

    In this work, we demonstrate sputtered amorphous indium-gallium-zinc oxide thin-film transistors (a-IGZO TFTs) with a record high effective field-effect mobility of 174 cm(2)/V s by incorporating silver nanowire (AgNW) arrays to channel electron transport. Compared to the reference counterpart without nanowires, the over 5-fold enhancement in the effective field-effect mobility exhibits clear dependence on the orientation as well as the surface coverage ratio of silver nanowires. Detailed material and device analyses reveal that during the room-temperature IGZO sputtering indium and oxygen diffuse into the nanowire matrix while the nanowire morphology and good contact between IGZO and nanowires are maintained. The unchanged morphology and good interfacial contact lead to high mobility and air-ambient-stable characteristics up to 3 months. Neither hysteresis nor degraded bias stress reliability is observed. The proposed AgNW-mediated a-IGZO TFTs are promising for development of large-scale, flexible, transparent electronics.

  8. 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)

  9. Gallium uptake in myositis ossificans. Potential pitfalls in diagnosis

    International Nuclear Information System (INIS)

    Salzman, L.; Lee, V.W.; Grant, P.

    1987-01-01

    Seven cases of gallium uptake in myositis ossificans are described. Gallium scans are done frequently in paraplegics, quadriplegics, and comatose patients to look for occult infection. It is important to be aware of possible gallium uptake in myositis ossificans, particularly in the extremities, which is frequent in these patients. Gallium uptake may be present prior to any abnormalities seen on plain films or CT scans. It is important to correlate roentgenograms with abnormal gallium scans, particularly in the extremities, to avoid potential pitfalls in diagnosis and prevent unnecessary antibiotic treatment. A bone scan should be obtained whenever possible, particularly when roentgenograms are negative, to confirm the diagnosis

  10. 67Gallium lung scans in progressive systemic sclerosis

    International Nuclear Information System (INIS)

    Baron, M.; Feiglin, D.; Hyland, R.; Urowitz, M.B.; Shiff, B.

    1983-01-01

    67 Gallium lung scans were performed in 19 patients with progressive systemic sclerosis (scleroderma). Results were expressed quantitatively as the 67 Gallium Uptake Index. The mean total pulmonary 67 Gallium Uptake Index in patients was significantly higher than that in controls (41 versus 25), and 4 patients (21%) fell outside the normal range. There were no clinical or laboratory variables that correlated with the 56 Gallium uptake. Increased pulmonary 67 Gallium uptake in scleroderma may prove useful as an index of pulmonary disease activity

  11. Method for producing polycrystalline boron nitride

    International Nuclear Information System (INIS)

    Alexeevskii, V.P.; Bochko, A.V.; Dzhamarov, S.S.; Karpinos, D.M.; Karyuk, G.G.; Kolomiets, I.P.; Kurdyumov, A.V.; Pivovarov, M.S.; Frantsevich, I.N.; Yarosh, V.V.

    1975-01-01

    A mixture containing less than 50 percent of graphite-like boron nitride treated by a shock wave and highly defective wurtzite-like boron nitride obtained by a shock-wave method is compressed and heated at pressure and temperature values corresponding to the region of the phase diagram for boron nitride defined by the graphite-like compact modifications of boron nitride equilibrium line and the cubic wurtzite-like boron nitride equilibrium line. The resulting crystals of boron nitride exhibit a structure of wurtzite-like boron nitride or of both wurtzite-like and cubic boron nitride. The resulting material exhibits higher plasticity as compared with polycrystalline cubic boron nitride. Tools made of this compact polycrystalline material have a longer service life under impact loads in machining hardened steel and chilled iron. (U.S.)

  12. 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

  13. EDXRF and TXRF determination of gallium in gallium-uranium matrix

    International Nuclear Information System (INIS)

    Misra, N.L.; Sanjay Kumar, S.; Dhara, Sangita; Aggarwal, S.K.; Venugopal, V.

    2009-01-01

    Energy Dispersive X-Ray Fluorescence (EDXRF) and Total Reflection X-ray Fluorescence (TXRF) methods for determination of Gallium in Gallium-Uranium matrix have been developed. For EDXRF determinations, 200 μL of standards/samples mixed with internal standard copper were dispersed on 30 mm diameter absorbent sheet so that it behaves like a thin film of the sample. The Gallium amounts in samples were determined from their EDXRF spectra using a calibration plot. For TXRF determinations, samples were taken on flat polished quartz sample supports and Gallium was determined in conventional way. For EDXRF and TXRF determinations, the average precision and accuracy obtained for Ga determinations was better than 3% (1σ). (author)

  14. 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)

  15. Pyrochemical reprocessing of nitride fuel

    International Nuclear Information System (INIS)

    Nakazono, Yoshihisa; Iwai, Takashi; Arai, Yasuo

    2004-01-01

    Electrochemical behavior of actinide nitrides in LiCl-KCl eutectic melt was investigated in order to apply pyrochemical process to nitride fuel cycle. The electrode reaction of UN and (U, Nd)N was examined by cyclic voltammetry. The observed rest potential of (U, Nd)N depended on the equilibrium of U 3+ /UN and was not affected by the addition of NdN of 8 wt.%. (author)

  16. Superplastic forging nitride ceramics

    Science.gov (United States)

    Panda, P.C.; Seydel, E.R.; Raj, R.

    1988-03-22

    A process is disclosed for preparing silicon nitride ceramic parts which are relatively flaw free and which need little or no machining, said process comprising the steps of: (a) preparing a starting powder by wet or dry mixing ingredients comprising by weight from about 70% to about 99% silicon nitride, from about 1% to about 30% of liquid phase forming additive and from 1% to about 7% free silicon; (b) cold pressing to obtain a preform of green density ranging from about 30% to about 75% of theoretical density; (c) sintering at atmospheric pressure in a nitrogen atmosphere at a temperature ranging from about 1,400 C to about 2,200 C to obtain a density which ranges from about 50% to about 100% of theoretical density and which is higher than said preform green density, and (d) press forging workpiece resulting from step (c) by isothermally uniaxially pressing said workpiece in an open die without initial contact between said workpiece and die wall perpendicular to the direction of pressing and so that pressed workpiece does not contact die wall perpendicular to the direction of pressing, to substantially final shape in a nitrogen atmosphere utilizing a temperature within the range of from about 1,400 C to essentially 1,750 C and strain rate within the range of about 10[sup [minus]7] to about 10[sup [minus]1] seconds[sup [minus]1], the temperature and strain rate being such that surface cracks do not occur, said pressing being carried out to obtain a shear deformation greater than 30% whereby superplastic forging is effected.

  17. Application of extraction of gallium molybdotungstate HPA for their investigation in solutions and gallium determination

    International Nuclear Information System (INIS)

    Kol'tsova, E.G.; Vakulich, A.N.; Tsyganok, L.P.

    2001-01-01

    Extraction of gallium molybdotungstate heteropolyacids and their associates with a row of triphenylmethane dyes, use of extraction for study of complexing in Mo 6 -W 6 -Ga 3+ -H 3 O + system are investigated. Research of optimal analytical states and development of extraction spectrophotometric methods of gallium determination are done. It is shown that increase of Mo 6 part in heteropolyanion improves solvation interaction of heteropolyacids with organic solvents elevating extraction properties of polyanion [ru

  18. Synthesis and Raman scattering of GaN nanorings, nanoribbons and nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Li, Z.J. [Academia Sinica, Beijing, BJ (China). Inst. of Physics; Northwestern Polytechnical Univ., Xian, SN (China). Dept. of Materials Science and Engineering; Chen, X.L.; Tu, Q.Y.; Yang, Z.; Xu, Y.P.; Hu, B.Q. [Academia Sinica, Beijing, BJ (China). Inst. of Physics; Li, H.J. [Northwestern Polytechnical Univ., Xian, SN (China). Dept. of Materials Science and Engineering

    2001-05-01

    Low-dimensional GaN materials, including nanorings, nanoribbons and smooth nanowires have been synthesized by reacting gallium and ammonia using Ag particles as a catalyst on the substrate of MgO single crystals. They were characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). EDX, XRD indicated that the low-dimensional nanomaterials were wurtzite GaN. New features are found in Raman scatterings for these low-dimensional GaN materials, which are different from the previous observations of GaN materials. (orig.)

  19. Nitride stabilized core/shell nanoparticles

    Science.gov (United States)

    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.

  20. Optical characterisation of III-V nitride-based multiphase and diluted magnetic semiconductors

    International Nuclear Information System (INIS)

    Wegscheider, M.

    2009-01-01

    The present work is devoted to the investigation of the optical properties of transition metal doped Gallium nitride. The Gallium nitride layers are epitaxially grown in a full metalorganic chemical vapour deposition process whereas the transition metals iron or manganese as well as the n and p-type dopants silicon and magnesium are incorporated simultaneously. Background and driving force of the realization of such material systems is basically the evocation of ferromagnetic spin alignment where free carriers ensure the correspondence between the localized spin state provided by the metal ions. The production of completely new devices for semiconductor industries based on the possibility to switch on or off the ferrimagnetic alignment by changing the free carrier concentration can be expected in the near future. In this context photoluminescence studies in the ultraviolet and mid infrared spectral range at temperatures between the liquid helium point and room temperature at atmospheric pressure were made. These measurements basically provide information on optical transitions between the conduction and valence band and deep defects as well as on crystal field forced transitions within the d-orbitals of the metal ion involved. In this context valuable knowledge could have been gained on doping concentrations, growth fashions and parameters, formation of secondary phases as well as on the doping efficiency and incorporation sites of the metal atoms. (author) [de

  1. The role of gallium-67 in Hodgkin's disease

    International Nuclear Information System (INIS)

    Bogart, Jeffrey A.; Chung, T. Chung; Mariados, Neil F.

    1996-01-01

    Purpose/Objective: Although widely used, the value of gallium imaging in managing Hodgkin's lymphoma remains unclear. Methods: Retrospective review of gallium and treatment data in patients with Hodgkin's disease between January 1990 and July 1995. Results: Eighty-six of 101 patients had Ga-67 imaging. Stage was as follows: 1A-11 patients, 1B - 2, 2A - 27, 2B - 22, 3A - 10, 3B - 5, 4A - 3 and 4B - 6. Sixty-two patients had staging gallium scans and 15% of tumors were not gallium avid. Two patients were upstaged based on gallium scan. Five patients had positive laparotomy and all had negative abdominal gallium exams. Three studies had false positive lesions. Initial therapy was assessed with gallium in 61 patients and 45 had complete response. Tumor recurred in 36% ((10(28))) of patients gallium negative after 3-6 cycles of chemotherapy, with no recurrences in 17 patients gallium negative after radiotherapy or chemo radiation. Six of 7 patients with focal gallium uptake after chemotherapy received radiotherapy and all remain disease free. Seven patients had persistent or progressive gallium-avid tumor after chemotherapy correlating with clinical disease. Two patients had false positive exams after radiotherapy. Twenty-two patients had gallium scans at recurrence. One scan was (false) negative and in two cases, gallium imaging was the initial evidence of recurrent tumor. Conclusion: Ga-67 imaging may help confirm the presence of active Hodgkin's disease, but was unreliable in defining disease remission after chemotherapy in this study population. Prospective studies may help define the role of gallium scans

  2. Long-chain amine-templated synthesis of gallium sulfide and gallium selenide nanotubes

    Science.gov (United States)

    Seral-Ascaso, A.; Metel, S.; Pokle, A.; Backes, C.; Zhang, C. J.; Nerl, H. C.; Rode, K.; Berner, N. C.; Downing, C.; McEvoy, N.; Muñoz, E.; Harvey, A.; Gholamvand, Z.; Duesberg, G. S.; Coleman, J. N.; Nicolosi, V.

    2016-06-01

    We describe the soft chemistry synthesis of amine-templated gallium chalcogenide nanotubes through the reaction of gallium(iii) acetylacetonate and the chalcogen (sulfur, selenium) using a mixture of long-chain amines (hexadecylamine and dodecylamine) as a solvent. Beyond their role as solvent, the amines also act as a template, directing the growth of discrete units with a one-dimensional multilayer tubular nanostructure. These new materials, which broaden the family of amine-stabilized gallium chalcogenides, can be tentatively classified as direct large band gap semiconductors. Their preliminary performance as active material for electrodes in lithium ion batteries has also been tested, demonstrating great potential in energy storage field even without optimization.We describe the soft chemistry synthesis of amine-templated gallium chalcogenide nanotubes through the reaction of gallium(iii) acetylacetonate and the chalcogen (sulfur, selenium) using a mixture of long-chain amines (hexadecylamine and dodecylamine) as a solvent. Beyond their role as solvent, the amines also act as a template, directing the growth of discrete units with a one-dimensional multilayer tubular nanostructure. These new materials, which broaden the family of amine-stabilized gallium chalcogenides, can be tentatively classified as direct large band gap semiconductors. Their preliminary performance as active material for electrodes in lithium ion batteries has also been tested, demonstrating great potential in energy storage field even without optimization. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01663d

  3. Optical characteristics of a gallium laser plasma

    International Nuclear Information System (INIS)

    Shuaibov, A.K.; Shimon, L.L.; Dashchenko, A.I.; Shevera, I.V.; Chuchman, M.P.

    2001-01-01

    Results are presented from studies of the emission from an erosion gallium laser plasma at a moderate intensity (W = (1-5) x 10 8 W/cm 2 ) of a 1.06-μm laser radiation. It is shown that, under these conditions, the lower excited states of gallium atoms are populated most efficiently. Among the ions, only the most intense GaII lines are observed in the emission spectrum. The populations of GaI and GaII excited states are not related to direct electron excitation, but are determined by the recombination of gallium ions with slow electrons. The recombination times of GaIII and GaII ions in the core of the plasma jet are determined from the waveforms of emission in the GaII and GaI spectral lines and are equal to 10 and 140 ns, respectively. The results obtained are of interest for spectroscopic diagnostics of an erosion plasma produced from gallium-containing layered crystals during the laser deposition of thin films

  4. Gallium-positive Lyme disease myocarditis

    International Nuclear Information System (INIS)

    Alpert, L.I.; Welch, P.; Fisher, N.

    1985-01-01

    In the course of a work-up for fever of unknown origin associated with intermittent arrhythmias, a gallium scan was performed which revealed diffuse myocardial uptake. The diagnosis of Lyme disease myocarditis subsequently was confirmed by serologic titers. One month following recovery from the acute illness, the abnormal myocardial uptake completely resolved

  5. Simulation of STM technique for electron transport through boron-nitride nanotubes

    International Nuclear Information System (INIS)

    Ganji, M.D.; Mohammadi-nejad, A.

    2008-01-01

    We report first-principles calculations on the electrical transport properties of boron-nitrid nanotubes (BNNTs). We consider a single walled (5,0) boron-nitrid nanotube sandwiched between an Au(1 0 0) substrate and a monatomic Au scanning tunneling microscope (STM) tip. Lateral motion of the tip over the nanotube wall cause it to change from one conformation class to the others and to switch between a strongly and a weakly conducting state. Thus, surprisingly, despite their apparent simplicity these Au/BNNT/Au nanowires are shown to be a convenient switch. Experiments with a conventional STM are proposed to test these predictions. The projection of the density of states (PDOS) and the transmission coefficients T(E) of the two-probe systems at zero bias are analyzed, and it suggests that the variation of the coupling between the wire and the electrodes leads to switching behaviour

  6. A Preliminary Study on the Synthesis and Characterization of Multilayered Ag/Co Magnetic Nanowires Fabricated via the Electrodeposition Method

    Directory of Open Access Journals (Sweden)

    Cheng-Hsiung Peng

    2013-01-01

    Full Text Available A single-bath electrodeposition method was developed to integrate multilayer Ag/Co nanowires with a commercial anodic alumina oxide (AAO template with a pore diameter of 100–200 nm. An electrolyte system containing silver nitride and cobalt sulfide was studied using cyclic voltammetry, and the electrodeposition rate was varied to optimize the electrodeposition conditions. A constant stepwise potential and a variable cation ratio of [Co2+]/[Ag+] were used during electrodeposition. After the dissolution of the template in aqueous NaOH solution, multilayered Ag/Co nanowires were obtained with a composition of [Co]/[Ag80Co20], as identified by XRD and TEM, when [Co2+]/[Ag+] = 150. By annealing at 200°C for 1 h, uniformly structured (Co99.57/Ag100 nanowires were obtained. Compared with pure Co nanowires, the magnetic hysteresis loops showed a greater magnetic anisotropy for (Co99.57/Ag100 nanowires than for pure Co nanowires, corresponding to a change in the easy axis upon magnetization.

  7. Leachability of nitrided ilmenite in hydrochloric acid

    CSIR Research Space (South Africa)

    Swanepoel, JJ

    2010-10-01

    Full Text Available Titanium nitride in upgraded nitrided ilmenite (bulk of iron removed) can selectively be chlorinated to produce titanium tetrachloride. Except for iron, most other components present during this low temperature (ca. 200 °C) chlorination reaction...

  8. 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.

  9. Dose dependent disposition of gallium-67 in rats

    International Nuclear Information System (INIS)

    Gautam, S.R.

    1982-01-01

    Radioactive gallium-67 has been employed as a diagnostic and follow-up agent for cancer therapy. Currently gallium nitrate is undergoing Phase I clinical studies. A million fold increase in the concentration of the carrier gallium citrate over the range of carrier-free gallium-67 (pgm) to 1.0 μg caused no significant alteration in the disposition of gallium-67 in rats.Gallium-67 was eliminated from blood with a biological t1/2 of 4.1 days. A linear tissue binding profile was observed for gallium-67 over this concentration range. A multi-compartment pharmacokinetic model was developed in which all the tissues studied were treated as separate compartments. At 1.0 mg dose level, significant alteration in the disposition of gallium-67 was observed in rats, > 95% of the initial radioactivity was characteristic reappearance of the radioactivity in the blood approximately 4 hours after dosing leading to a ''hump'' in the blood concentration-time profiles. Following the 1.0 mg dose low tissue levels were observed, except for the kidneys, which contained about 8% of the administered dose per gram of the tissue one-half hour after dosing. A non-linear tissue binding profile was observed to be associated with gallium at high doses. It was hypothesized that the rapid loss of gallium-67 from the vascular system following the high doses of gallium citrate was due to the accumulation of the drug in the kidneys where it was eventually eliminated via urine. The kidneys thus would act as a temporary storage site for gallium. It was concluded that the dose-related renal toxicity associated with gallium therapy may be attributed to the kidney's role as a temporary storage site following high doses

  10. Leachability of nitrided ilmenite in hydrochloric acid

    OpenAIRE

    Swanepoel, J.J.; van Vuuren, D.S.; Heydenrych, M.

    2011-01-01

    Titanium nitride in upgraded nitrided ilmenite (bulk of iron removed) can selectively be chlorinated to produce titanium tetrachloride. Except for iron, most other components present during this low temperature (ca. 200°C) chlorination reaction will not react with chlorine. It is therefore necessary to remove as much iron as possible from the nitrided ilmenite. Hydrochloric acid leaching is a possible process route to remove metallic iron from nitrided ilmenite without excessive dissolution o...

  11. Fabrication of vanadium nitride by carbothermal nitridation reaction

    International Nuclear Information System (INIS)

    Wang Xitang; Wang Zhuofu; Zhang Baoguo; Deng Chengji

    2005-01-01

    Vanadium nitride is produced from V 2 O 5 by carbon-thermal reduction and nitridation. When the sintered temperature is above 1273 K, VN can be formed, and the nitrogen content of the products increased with the firing temperature raised, and then is the largest when the sintered temperature is 1573 K. The C/V 2 O 5 mass ratio of the green samples is the other key factor affecting on the nitrogen contents of the products. The nitrogen content of the products reaches the most when the C/V 2 O 5 mass ratio is 0.33, which is the theoretical ratio of the carbothermal nitridation of V 2 O 5 . (orig.)

  12. Long Silver Nanowires Synthesis by Pulsed Electrodeposition

    Directory of Open Access Journals (Sweden)

    M.R. Batevandi

    2015-09-01

    Full Text Available Silver nanowires were pulse electrodeposited into nanopore anodic alumina oxide templates. The effects of continuous and pulse electrodeposition waveform on the microstructure properties of the nanowire arrays were studied. It is seen that the microstructure of nanowire is depend to pulse condition. The off time duration of pulse waveform enables to control the growth direction of Ag nanowires.

  13. Aging of Organic Nanowires

    DEFF Research Database (Denmark)

    Balzer, Frank; Schiek, Manuela; Osadnik, Andreas

    2012-01-01

    Organic semiconductors formed by epitaxial growth from small molecules such as the para-phenylenes or squaraines promise a vast application potential as the active ingredient in electric and optoelectronic devices. Their self-organization into organic nanowires or "nanofibers" adds a peculiar...... attribute, making them especially interesting for light generation in OLEDs and for light-harvesting devices such as solar cells. Functionalization of the molecules allows the customization of optical and electrical properties. However, aging of the wires might lead to a considerable decrease in device...... performance over time. In this study the morphological stability of organic nanoclusters and nanowires from the methoxy functionalized quaterphenylene, 4,4'''dimethoxy-1,1':4',1''4'',1'''-quaterphenylene (MOP4), is investigated in detail. Aging experiments conducted by atomic force microscopy under ambient...

  14. Silicon nanowire transistors

    CERN Document Server

    Bindal, Ahmet

    2016-01-01

    This book describes the n and p-channel Silicon Nanowire Transistor (SNT) designs with single and dual-work functions, emphasizing low static and dynamic power consumption. The authors describe a process flow for fabrication and generate SPICE models for building various digital and analog circuits. These include an SRAM, a baseband spread spectrum transmitter, a neuron cell and a Field Programmable Gate Array (FPGA) platform in the digital domain, as well as high bandwidth single-stage and operational amplifiers, RF communication circuits in the analog domain, in order to show this technology’s true potential for the next generation VLSI. Describes Silicon Nanowire (SNW) Transistors, as vertically constructed MOS n and p-channel transistors, with low static and dynamic power consumption and small layout footprint; Targets System-on-Chip (SoC) design, supporting very high transistor count (ULSI), minimal power consumption requiring inexpensive substrates for packaging; Enables fabrication of different types...

  15. 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.)

  16. Characterization of Nanowire Photodetectors

    Science.gov (United States)

    2016-11-28

    characterization system and picosecond pulsed laser source will be used to provide deeper insight into the fast charge carrier dynamics in the GaAsSb and...value of the current fluctuations for a particular frequency, f is the effective measurement bandwidth at the discrete frequency point, and IDS is...GaAsSb CS nanowires. The best fit of the spectra with the simulation carried out using Matlab revealed flicker noise at lower frequency having 1/f

  17. 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.

  18. 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

  19. 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.)

  20. 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.

  1. Interactions of zircaloy cladding with gallium -- 1997 status

    International Nuclear Information System (INIS)

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

    1997-11-01

    A four phase 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 LWR. This graded, four phase experimental program will 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 an initial series of tests for phases 1 and 2. Three types of tests are being performed: (1) corrosion, (2) liquid metal embrittlement (LME), and (3) corrosion mechanical. These tests are designed to determine the corrosion mechanisms, thresholds for temperature and concentration of gallium that may delineate behavioral regimes, and changes in 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 (in parts per million) of gallium in the MOX fuel. While continued migration of gallium into the initially formed intermetallic compound results in large stresses that can lead to distortion, this is also highly 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

  2. 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

  3. Quantum transport in semiconductor nanowires

    NARCIS (Netherlands)

    Van Dam, J.

    2006-01-01

    This thesis describes a series of experiments aimed at understanding the low-temperature electrical transport properties of semiconductor nanowires. The semiconductor nanowires (1-100 nm in diameter) are grown from nanoscale gold particles via a chemical process called vapor-liquid-solid (VLS)

  4. Shape Engineering Driven by Selective Growth of SnO2 on Doped Ga2O3 Nanowires.

    Science.gov (United States)

    Alonso-Orts, Manuel; Sánchez, Ana M; Hindmarsh, Steven A; López, Iñaki; Nogales, Emilio; Piqueras, Javier; Méndez, Bianchi

    2017-01-11

    Tailoring the shape of complex nanostructures requires control of the growth process. In this work, we report on the selective growth of nanostructured tin oxide on gallium oxide nanowires leading to the formation of SnO 2 /Ga 2 O 3 complex nanostructures. Ga 2 O 3 nanowires decorated with either crossing SnO 2 nanowires or SnO 2 particles have been obtained in a single step treatment by thermal evaporation. The reason for this dual behavior is related to the growth direction of trunk Ga 2 O 3 nanowires. Ga 2 O 3 nanowires grown along the [001] direction favor the formation of crossing SnO 2 nanowires. Alternatively, SnO 2 forms rhombohedral particles on [110] Ga 2 O 3 nanowires leading to skewer-like structures. These complex oxide structures were grown by a catalyst-free vapor-solid process. When pure Ga and tin oxide were used as source materials and compacted powders of Ga 2 O 3 acted as substrates, [110] Ga 2 O 3 nanowires grow preferentially. High-resolution transmission electron microscopy analysis reveals epitaxial relationship lattice matching between the Ga 2 O 3 axis and SnO 2 particles, forming skewer-like structures. The addition of chromium oxide to the source materials modifies the growth direction of the trunk Ga 2 O 3 nanowires, growing along the [001], with crossing SnO 2 wires. The SnO 2 /Ga 2 O 3 junctions does not meet the lattice matching condition, forming a grain boundary. The electronic and optical properties have been studied by XPS and CL with high spatial resolution, enabling us to get both local chemical and electronic information on the surface in both type of structures. The results will allow tuning optical and electronic properties of oxide complex nanostructures locally as a function of the orientation. In particular, we report a dependence of the visible CL emission of SnO 2 on its particular shape. Orange emission dominates in SnO 2 /Ga 2 O 3 crossing wires while green-blue emission is observed in SnO 2 particles attached to Ga 2

  5. Epitaxial GaN films by hyperthermal ion-beam nitridation of Ga droplets

    Energy Technology Data Exchange (ETDEWEB)

    Gerlach, J. W.; Ivanov, T.; Neumann, L.; Hoeche, Th.; Hirsch, D.; Rauschenbach, B. [Leibniz-Institut fuer Oberflaechenmodifizierung (IOM), D-04318 Leipzig (Germany)

    2012-06-01

    Epitaxial GaN film formation on bare 6H-SiC(0001) substrates via the process of transformation of Ga droplets into a thin GaN film by applying hyperthermal nitrogen ions is investigated. Pre-deposited Ga atoms in well defined amounts form large droplets on the substrate surface which are subsequently nitridated at a substrate temperature of 630 Degree-Sign C by a low-energy nitrogen ion beam from a constricted glow-discharge ion source. The Ga deposition and ion-beam nitridation process steps are monitored in situ by reflection high-energy electron diffraction. Ex situ characterization by x-ray diffraction and reflectivity techniques, Rutherford backscattering spectrometry, and electron microscopy shows that the thickness of the resulting GaN films depends on the various amounts of pre-deposited gallium. The films are epitaxial to the substrate, exhibit a mosaic like, smooth surface topography and consist of coalesced large domains of low defect density. Possible transport mechanisms of reactive nitrogen species during hyperthermal nitridation are discussed and the formation of GaN films by an ion-beam assisted process is explained.

  6. Growth of 1.5 micron gallium indium nitrogen arsenic antimonide vertical cavity surface emitting lasers by molecular beam epitaxy

    Science.gov (United States)

    Wistey, Mark Allan

    Fiber optics has revolutionized long distance communication and long haul networks, allowing unimaginable data speeds and noise-free telephone calls around the world for mere pennies per hour at the trunk level. But the high speeds of optical fiber generally do not extend to individual workstations or to the home, in large part because it has been difficult and expensive to produce lasers which emitted light at wavelengths which could take advantage of optical fiber. One of the most promising solutions to this problem is the development of a new class of semiconductors known as dilute nitrides. Dilute nitrides such as GaInNAs can be grown directly on gallium arsenide, which allows well-established processing techniques. More important, gallium arsenide allows the growth of vertical-cavity surface-emitting lasers (VCSELs), which can be grown in dense, 2D arrays on each wafer, providing tremendous economies of scale for manufacturing, testing, and packaging. Unfortunately, GaInNAs lasers have suffered from what has been dubbed the "nitrogen penalty," with high thresholds and low efficiency as the fraction of nitrogen in the semiconductor was increased. This thesis describes the steps taken to identify and essentially eliminate the nitrogen penalty. Protecting the wafer surface from plasma ignition, using an arsenic cap, greatly improved material quality. Using a Langmuir probe, we further found that the nitrogen plasma source produced a large number of ions which damaged the wafer during growth. The ions were dramatically reduced using deflection plates. Low voltage deflection plates were found to be preferable to high voltages, and simulations showed low voltages to be adequate for ion removal. The long wavelengths from dilute nitrides can be partly explained by wafer damage during growth. As a result of these studies, we demonstrated the first CW, room temperature lasers at wavelengths beyond 1.5mum on gallium arsenide, and the first GaInNAs(Sb) VCSELs beyond 1

  7. 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

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

    KAUST Repository

    Elafandy, Rami T.; Cha, Dong Kyu; Majid, Mohammed Abdul; Ng, Tien Khee; Ooi, Boon S.; Zhao, Lan

    2014-01-01

    -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

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

    National Research Council Canada - National Science Library

    Moore, Elizabeth A

    2007-01-01

    ...) alloys, and represents a comprehensive analysis of the resulting material's electrical and optical properties as a function of Al mole fraction, anneal temperature, anneal time, and implantation dose...

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

    Science.gov (United States)

    2016-06-01

    surrounding semiconductor by the ionization trail of beta particles . Fig. 2 shows an illustration of the DEC isotope battery. The advantage of using the...battery is enhanced lifetime because of the absence of semiconductor degradations from isotope due to low-energy beta particles . The configuration...betavoltaic process of EHP generation through a high-energy beta particle . The creation of phonons within the semiconductor is shown. This is covered

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

    Science.gov (United States)

    2016-09-01

    ACKNOWLEDGMENTS Foremost, I would like to thank my wife, Melissa, with whom I have three wonderful children. Without her endless love , unwavering...conducting research in the lab and studying in the library, she cared for our children and created a loving home for our family. Her strength, passion...Online]. Available: http://ecee.colorado.edu/~bart/book/book/title.htm 78 [12] R. T. Tung, “The physics and chemistry of the Schottky barrier

  12. 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

    In this paper an outphasing modulation control method suitable for line regulation of very high frequency resonant converters is described. The pros and cons of several control methods suitable for very high frequency resonant converters are described and compared to outphasing modulation...

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

    KAUST Repository

    Ibrahim, Youssef H.

    2013-01-01

    . 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

  14. Implantation activation annealing of Si-implanted gallium nitride at temperatures > 1,100 C

    International Nuclear Information System (INIS)

    Zolper, J.C.; Han, J.; Biefeld, R.M.

    1997-01-01

    The activation annealing of Si-implanted GaN is reported for temperatures from 1,100 to 1,400 C. Although previous work has shown that Si-implanted GaN can be activated by a rapid thermal annealing at ∼1,100 C, it was also shown that significant damage remained in the crystal. Therefore, both AlN-encapsulated and uncapped Si-implanted GaN samples were annealed in a metal organic chemical vapor deposition system in a N 2 /NH 3 ambient to further assess the annealing process. Electrical Hall characterization shows increases in carrier density and mobility for annealing up to 1,300 C before degrading at 1,400 C due to decomposition of the GaN epilayer. Rutherford backscattering spectra show that the high annealing temperatures reduce the implantation induced damage profile but do not completely restore the as-grown crystallinity

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

    Science.gov (United States)

    2017-07-27

    and sensor systems of interest to US Defense Department applications, particularly for next-generation radar systems. Broadband, efficient, high...A simple GaN high-electron-mobility-transistor (HEMT) TR single-pull double- throw (SPDT) switch consists of at least 2 series- and 2 shunt... simple TR switch that works well up to 6 GHz is shown in Figs. 4 (layout) and 5 (simulation). Complementary DC-bias voltages are applied at inputs A

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

    Science.gov (United States)

    2017-08-14

    networking, and sensor systems of interest to Department of Defense applications, particularly for next-generation radar systems. Broadband, efficient, high...simulations of MMIC (3–6 GHz, 28 V/180 mA) 1.75-mm HEMT power amplifier ............................................... 13 Fig. 20 Simple schematic...design simple , a single 1.75-mm high-electron-mobility transistor (HEMT) was used for a preliminary ideal design of the broadband power amplifier

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

    Science.gov (United States)

    2011-09-01

    capture in a solid state device,” Journal of Physics D: Applied Physics, vol. 43, p. 075502, 2010. [28] D. S. McGregor, M. F. Ohmes , R. E. Ortiz, A. S...1044, 1964. [5] M. Cardona and L. Ley , Photoemission in Solids: General Principles. Springer- Verlag New York, 1978. [6] C. Cohen-Tannoudji, B. Diu...A, vol. 50, no. 6, pp. 449–450, 1975. [46] L. Ley , R. A. Pollak, F. R. McFeely, S. P. Kowalczyk, and D. A. Shirley, “Total valence-band densities of

  18. Selective excitation of the yellow and blue luminescence in n- and p-doped Gallium Nitride

    International Nuclear Information System (INIS)

    Colton, John S.

    2000-01-01

    GaN is an interesting material: technologically very useful, but still having many unexplained features. Two such features are the broad defect-related luminescence bands: the YL of n-type GaN and the BL of Mg-doped p-type GaN. We have employed selective excitation to investigate these bands. In the case of the YL, most of the previous evidence has supported a recombination model between distant donors and acceptors, most likely a transition involving a shallow donor to a deep acceptor. Our selective excitation experiments have resolved finer structures within the YL. Our results indicate that the YL in bulk samples is related to the YL in film samples. We suggest that selectively excited YL involves recombination at DAP complexes, rather than between spatially distant DAPs (however other recombination channels, including that of distant DAPs may become significant under other excitation conditions). Characteristics of the DAP complexes within our YL model include (a) an electron localization energy of around 60-70 meV, (b) a localized phonon energy of around 40 meV, and (c) excited states of the complex at 200 and 370 meV above the ground state. In the case of the BL, the deep defect responsible for the BL is unknown, and there may not even be a deep defect involved. Also in dispute is the role of potential fluctuations in the properties of the BL. Our results have been explain in a model whereby emission is from DAPs, and significant effects are produced by doping-related potential fluctuations and disorder. Characteristics of the our model for the BL include (a) an Urbach tail, having width E 0 = 33 meV, (b) a strong electron-LO phonon coupling occurring with a Frank-Condon shift of ∼ 180 meV between excitation and emission, (c) a mobility gap at 2.8 eV, separating highly mobile states and highly localized states, and (d) PL-like behavior for excitation energies larger than 2.8 eV, having a blue-shift with increasing excitation energy caused by the increased number of free carriers in the material

  19. 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...

  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

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

    Science.gov (United States)

    2007-12-01

    like to thank the many friends I have made along the way, Matt Lange, Catherine Taylor, Glen Kading, and Greg Pitz for helping me to remember that life...oxidation. The Ta wrapping wire survives the anneal intact, but becomes brittle enough to easily break off. The samples are taken to the clean room

  2. Cubic Gallium Nitride on Micropatterned Si (001) for Longer Wavelength LEDs

    Energy Technology Data Exchange (ETDEWEB)

    Durniak, Mark T. [Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Materials Science and Engineering; Chaudhuri, Anabil [Univ. of New Mexico, Albuquerque, NM (United States). Center for High Technology Materials; Smith, Michael L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Advanced Material Sciences; Allerman, Andrew A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Advanced Material Sciences; Lee, S. C. [Univ. of New Mexico, Albuquerque, NM (United States). Center for High Technology Materials; Brueck, S. R. J. [Univ. of New Mexico, Albuquerque, NM (United States). Center for High Technology Materials; Wetzel, Christian [Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Physics, Applied Physics, and Astronomy and Dept. of Materials Science and Engineering

    2016-03-01

    GaInN/GaN heterostructures of cubic phase have the potential to overcome the limitations of wurtzite structures commonly used for light emitting and laser diodes. Wurtzite GaInN suffers from large internal polarization fields, which force design compromises ( 0001 ) towards ultra-narrow quantum wells and reduce recombination volume and efficiency. Cubic GaInN microstripes grown at Rensselaer Polytechnic Institute by metal organic vapor phase epitaxy on micropatterned Si , with {111} v-grooves oriented along Si ( 001 ) , offer a system free of internal polarization fields, wider quantum wells, and smaller <00$\\bar1$> bandgap energy. We prepared 6 and 9 nm Ga x In 1-x N/GaN single quantum well structures with peak wavelength ranges from 520 to 570 nm with photons predominately polarized perpendicular to the grooves. We estimate a cubic InN composition range of 0 < x < 0.5 and an upper limit of the internal quantum efficiency of 50%. Stripe geometry and polarization may be suitable for mode confinement and reduced threshold stimulated emission.

  3. Hollow-anode plasma source for molecular beam epitaxy of gallium nitride

    International Nuclear Information System (INIS)

    Anders, A.; Newman, N.; Rubin, M.; Dickinson, M.; Jones, E.; Phatak, P.; Gassmann, A.

    1996-01-01

    GaN films have been grown by molecular beam epitaxy (MBE) using a hollow-anode nitrogen plasma source. The source was developed to minimize defect formation as a result of contamination and ion damage. The hollow-anode discharge is a special form of glow discharge with very small anode area. A positive anode voltage drop of 30 endash 40 V and an increased anode sheath thickness leads to ignition of a relatively dense plasma in front of the anode hole. Driven by the pressure gradient, the open-quote open-quote anode close-quote close-quote plasma forms a bright plasma jet streaming with supersonic velocity towards the substrate. Films of GaN have been grown on (0001) SiC and (0001) Al 2 O 3 at 600 endash 800 degree C. The films were investigated by photoluminescence, cathodoluminescence, x-ray diffraction, Rutherford backscattering, and particle-induced x-ray emission. The film with the highest structural quality had a rocking curve width of 5 arcmin, the lowest reported value for MBE growth to date. copyright 1996 American Institute of Physics

  4. Performance characterization of gallium nitride HEMT cascode switch for power conditioning applications

    International Nuclear Information System (INIS)

    Chou, Po-Chien; Cheng, Stone

    2015-01-01

    Highlights: • We develop TO-257 cascoded GaN switch configuration in power conversion applications. • The normally-off cascode circuit provides 14.6 A/600 V characteristics. • Analysis of resistive and inductive switching performances shown in loaded circuits. • A 48-to-96 V boost converter is used to evaluate the benefit of GaN cascode switches. - Abstract: A hybrid cascoded GaN switch configuration is demonstrated in power conversion applications. A novel metal package is proposed for the packaging of a D-mode GaN MIS-HEMT cascoded with an integrated power MOSFET and a SBD. The normally-off cascode circuit provides a maximum drain current of 14.6 A and a blocking capability of 600 V. Analysis of 200 V/1 A power conversion characteristics are discussed and show the excellent switching performance in load circuits. Switching characteristics of the integral SiC SBD are also demonstrated. Finally, a 48-to-96 V boost converter is used to evaluate the benefit of GaN cascode switches. These results show that high-voltage GaN-HEMTs can be switching devices for an ultralow-loss converter circuit

  5. Development and evaluation of gallium nitride-based thin films for x-ray dosimetry

    International Nuclear Information System (INIS)

    Hofstetter, Markus; Thalhammer, Stefan; Howgate, John; Sharp, Ian D; Stutzmann, Martin

    2011-01-01

    X-ray radiation plays an important role in medical procedures ranging from diagnostics to therapeutics. Due to the harm such ionizing radiation can cause, it has become common practice to closely monitor the dosages received by patients. To this end, precise online dosimeters have been developed with the dual objectives of monitoring radiation in the region of interest and improving therapeutic methods. In this work, we evaluate GaN thin film high electron mobility heterostructures with sub-mm 2 detection areas as x-ray radiation detectors. Devices were tested using 40-300 kV Bremsstrahlung x-ray sources. We find that the photoconductive device response exhibits a large gain, is almost independent of the angle of irradiation, and is constant to within 2% of the signal throughout this medical diagnostic x-ray range, indicating that these sensors do not require recalibration for geometry or energy. Furthermore, the devices show a high sensitivity to x-ray intensity and can measure in the air kerma rate (free-in-air) range of 1 μGy s -1 to 10 mGy s -1 with a signal stability of ±1% and a linear total dose response over time. Medical conditions were simulated by measurements of device responses to irradiation through human torso phantoms. Direct x-ray imaging is demonstrated using the index finger and wrist sections of a human phantom. The results presented here indicate that GaN-based thin film devices exhibit a wide range of properties, which make them promising candidates for dosimetry applications. In addition, with potential detection volumes smaller than 10 -6 cm 3 , they are well suited for high-resolution x-ray imaging. Moreover, with additional engineering steps, these devices can be adapted to potentially provide both in vivo biosensing and x-ray dosimetry.

  6. Investigation of Gallium Nitride Transistor Reliability through Accelerated Life Testing and Modeling

    Science.gov (United States)

    2011-12-01

    than my parents or I did, and recommended to my mother that I be advanced from his math class. I am grateful to my paternal grandmother who...without her. I thank her for her patience with me. My children are an inspiration to me. I thank them for their hugs, kisses , and sweet prayers

  7. Optical properties of aluminium-gallium-nitride semiconductors; Optische Eigenschaften von Aluminium-Galliumnitrid-Halbleitern

    Energy Technology Data Exchange (ETDEWEB)

    Roeppischer, Marcus

    2011-08-17

    In this work fundamental optical properties of AlN, GaN and their alloys are presented. Spectroscopic ellipsometry from the near infrared (NIR) to the vacuum-ultraviolet (VUV) spectral region was the main tool to investigate these properties. The complete dielectric function (DF) of cubic as well as hexagonal GaN and AlN in the range between 0.6 eV and 20 eV is shown here, for the first time. A layer model including surface roughness and buffer layers was used to separate the DF of the investigated layer from the measured pseudo-DF. Afterwards all absorption structures in the DF's are discussed in detail. Due to the comparison with calculated bandstructures these absorption structures could be connected to interband transitions at high symmetry points in the Brillouin zone (BZ). Within this analysis similarities and differences between GaN and AlN are discussed. For zincblende (zb) AlN a pronounced absorption tail below the direct band gap transition was detected. This behaviour is typical for a phonon-assisted indirect absorption. In contrast zb-GaN exhibits a clear direct absorption. Furthermore, a change in the energetic position of the two main interband absorptions E1 and E2 at the L- and X-point of the BZ was found. A detailed analysis of the anisotropic fundamental band gap of hexagonal AlN offers a interchange of the two topmost valance bands at the BZ center compared to GaN. Due to this permutation the fundamental band edge of wurtzit (wz) AlN is only visible for parallel polarized light, while for GaN it can be detect in the perpendicular configuration. By analysing the energetic position of the three excitonic transitions the crystal-field- and spin-orbit-splitting were defined to be {delta}{sub cr}=-226 meV and {delta}{sub so}=14 meV. In addition, the energetic positions for these transitions at T=15 K are 6.0465 eV, 6.2694 eV and 6.2775 eV. The comparison between measurements at room and low temperature shows an energetic shift for both absorption edges of about 80 meV. By comparing the energetic positions of the excitonic transitions with the lattice parameters of different samples on silicon, sapphire and SiC substrate the influence of strain on the optical properties of wz-AlN was investigated. Due to this analysis the deformation potentials within the cubic approximation were calculated. Finally the spectral region below the fundamental band gap absorption of cubic AlGaN layers were studied. Therefore an analytical model was developed to calculate the dispersion in the transparent range for an arbitrary Al-content.

  8. Performance characterization of gallium nitride HEMT cascode switch for power conditioning applications

    Energy Technology Data Exchange (ETDEWEB)

    Chou, Po-Chien; Cheng, Stone, E-mail: stonecheng@mail.nctu.edu.tw

    2015-08-15

    Highlights: • We develop TO-257 cascoded GaN switch configuration in power conversion applications. • The normally-off cascode circuit provides 14.6 A/600 V characteristics. • Analysis of resistive and inductive switching performances shown in loaded circuits. • A 48-to-96 V boost converter is used to evaluate the benefit of GaN cascode switches. - Abstract: A hybrid cascoded GaN switch configuration is demonstrated in power conversion applications. A novel metal package is proposed for the packaging of a D-mode GaN MIS-HEMT cascoded with an integrated power MOSFET and a SBD. The normally-off cascode circuit provides a maximum drain current of 14.6 A and a blocking capability of 600 V. Analysis of 200 V/1 A power conversion characteristics are discussed and show the excellent switching performance in load circuits. Switching characteristics of the integral SiC SBD are also demonstrated. Finally, a 48-to-96 V boost converter is used to evaluate the benefit of GaN cascode switches. These results show that high-voltage GaN-HEMTs can be switching devices for an ultralow-loss converter circuit.

  9. Electromagnetic Design of High Frequency PFC Boost Converters using Gallium Nitride Devices

    NARCIS (Netherlands)

    Wang, W.

    2017-01-01

    Throughout the history of power electronics, main driving force of developments is attribute to innovations in power semiconductor technology. With continuous technical improvements in the past 30 years, Si devices, being the most widely used power semiconductor technology, are approaching physical

  10. Elastic scattering by hot electrons and apparent lifetime of longitudinal optical phonons in gallium nitride

    Energy Technology Data Exchange (ETDEWEB)

    Khurgin, Jacob B., E-mail: jakek@jhu.edu [Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Bajaj, Sanyam; Rajan, Siddharth [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States)

    2015-12-28

    Longitudinal optical (LO) phonons in GaN generated in the channel of high electron mobility transistors (HEMT) are shown to undergo nearly elastic scattering via collisions with hot electrons. The net result of these collisions is the diffusion of LO phonons in the Brillouin zone causing reduction of phonon and electron temperatures. This previously unexplored diffusion mechanism explicates how an increase in electron density causes reduction of the apparent lifetime of LO phonons, obtained from the time resolved Raman studies and microwave noise measurements, while the actual decay rate of the LO phonons remains unaffected by the carrier density. Therefore, the saturation velocity in GaN HEMT steadily declines with increased carrier density, in a qualitative agreement with experimental results.

  11. Micro-Raman and photoluminescence studies of neutron-irradiated gallium nitride epilayers

    International Nuclear Information System (INIS)

    Wang, R.X.; Xu, S.J.; Fung, S.; Beling, C.D.; Wang, K.; Li, S.; Wei, Z.F.; Zhou, T.J.; Zhang, J.D.; Huang Ying; Gong, M.

    2005-01-01

    GaN epilayers grown on sapphire substrate were irradiated with various dosages of neutrons and were characterized using Micro-Raman and photoluminescence. It was found that the A 1 (LO) peak in the Raman spectra clearly shifted with neutron irradiation dosage. Careful curve fitting of the Raman data was carried out to obtain the carrier concentration which was found to vary with the neutron irradiation dosage. The variation of the full width at half maximum height of the photoluminescence was consistent with the Raman results. The neutron irradiation-induced structural defects (likely to be Ge Ga ) give rise to carrier trap centers which are responsible for the observed reduction in carrier concentration of the irradiated GaN

  12. Analysis of Proton Radiation Effects on Gallium Nitride High Electron Mobility Transistors

    Science.gov (United States)

    2017-03-01

    non - ionizing proton radiation damage effects at different energy levels on a GaN-on-silicon high electron mobility transistor...DISTRIBUTION CODE 13. ABSTRACT (maximum 200 words) In this work, a physics-based simulation of non - ionizing proton radiation damage effects at different...Polarization . . . . . . . . . . . . . . 6 2.3 Non - Ionizing Radiation Damage Effects . . . . . . . . . . . . . . . 10 2.4 Non - Ionizing Radiation Damage in

  13. Development of high temperature stable Ohmic and Schottky contacts on n-gallium nitride

    Science.gov (United States)

    Khanna, Rohit

    In this work the effort was made to towards develop and investigate high temperature stable Ohmic and Schottky contacts for n type GaN. Various borides and refractory materials were incorporated in metallization scheme to best attain the desired effect of minimal degradation of contacts when placed at high temperatures. This work focuses on achieving a contact scheme using different borides which include two Tungsten Borides (namely W2B, W2B 5), Titanium Boride (TiB2), Chromium Boride (CrB2) and Zirconium Boride (ZrB2). Further a high temperature metal namely Iridium (Ir) was evaluated as a potential contact to n-GaN, as part of continuing improved device technology development. The main goal of this project was to investigate the most promising boride-based contact metallurgies on GaN, and finally to fabricate a High Electron Mobility Transistor (HEMT) and compare its reliability to a HEMT using present technology contact. Ohmic contacts were fabricated on n GaN using borides in the metallization scheme of Ti/Al/boride/Ti/Au. The characterization of the contacts was done using current-voltage measurements, scanning electron microscopy (SEM) and Auger Electron Spectroscopy (AES) measurements. The contacts formed gave specific contact resistance of the order of 10-5 to 10-6 Ohm-cm2. A minimum contact resistance of 1.5x10-6 O.cm 2 was achieved for the TiB2 based scheme at an annealing temperature of 850-900°C, which was comparable to a regular ohmic contact of Ti/Al/Ni/Au on n GaN. When some of borides contacts were placed on a hot plate or in hot oven for temperature ranging from 200°C to 350°C, the regular metallization contacts degraded before than borides ones. Even with a certain amount of intermixing of the metallization scheme the boride contacts showed minimal roughening and smoother morphology, which, in terms of edge acuity, is crucial for very small gate devices. Schottky contacts were also fabricated and characterized using all the five boride compounds. The barrier height obtained on n GaN was ˜0-5-0.6 eV which was low compared to those obtained by Pt or Ni. This barrier height is too low for use as a gate contact and they can only have limited use, perhaps, in gas sensors where large leakage current can be tolerated in exchange for better thermal reliability. AlGaN/GaN High Electron Mobility Transistors (HEMTs) were fabricated with Ti/Al/TiB2/Ti/Au source/drain ohmic contacts and a variety of gate metal schemes (Pt/Au, Ni/Au, Pt/TiB2/Au or Ni/TiB 2/Au) and were subjected to long-term annealing at 350°C. By comparison with companion devices with conventional Ti/Al/Pt/Au ohmic contacts and Pt/Au gate contacts, the HEMTs with boride-based ohmic metal and either Pt/Au, Ni/Au or Ni/TiB2/Au gate metal showed superior stability of both source-drain current and transconductance after 25 days aging at 350°C. The need for sputter deposition of the borides causes' problem in achieving significantly lower specific contact resistance than with conventional schemes deposited using e-beam evaporation. The borides also seem to be, in general, good getters for oxygen leading to sheet resistivity issues. Ir/Au Schottky contacts and Ti/Al/Ir/Au ohmic contacts on n-type GaN were investigated as a function of annealing temperature and compared to their more common Ni-based counterparts. The Ir/Au ohmic contacts on n-type GaN with n˜1017 cm-3 exhibited barrier heights of 0.55 eV after annealing at 700°C and displayed less intermixing of the contact metals compared to Ni/Au. A minimum specific contact resistance of 1.6 x 10-6 O.cm2 was obtained for the ohmic contacts on n-type GaN with n˜1018 cm-3 after annealing at 900°C. The measurement temperature dependence of contact resistance was similar for both Ti/Al/Ir/Au and Ti/Al/Ni/Au, suggesting the same transport mechanism was present in both types of contacts. The Ir-based ohmic contacts displayed superior thermal aging characteristics at 350°C. Auger Electron Spectroscopy showed that Ir is a superior diffusion barrier at these moderate temperatures than Ni.

  14. Gallium Nitride: A Nano scale Study using Electron Microscopy and Associated Techniques

    International Nuclear Information System (INIS)

    Mohammed Benaissa; Vennegues, Philippe

    2008-01-01

    A complete nano scale study on GaN thin films doped with Mg. This study was carried out using TEM and associated techniques such as HREM, CBED, EDX and EELS. It was found that the presence of triangular defects (of few nanometers in size) within GaN:Mg films were at the origin of unexpected electrical and optical behaviors, such as a decrease in the free hole density at high Mg doping. It is shown that these defects are inversion domains limited with inversion-domains boundaries. (author)

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

    KAUST Repository

    Elafandy, Rami T.; Majid, Mohammed Abdul; Ng, Tien Khee; Zhao, Lan; Cha, Dong Kyu; Ooi, Boon S.

    2014-01-01

    , 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

  16. Optical and micro-structural characterizations of MBE grown indium gallium nitride polar quantum dots

    KAUST Repository

    Elafandy, Rami T.

    2011-12-01

    Comparison between indium rich (27%) InGaN/GaN quantum dots (QDs) and their underlying wetting layer (WL) is performed by means of optical and structural characterizations. With increasing temperature, micro-photoluminescence (μPL) study reveals the superior ability of QDs to prevent carrier thermalization to nearby traps compared to the two dimensional WL. Thus, explaining the higher internal quantum efficiency of the QD nanostructure compared to the higher dimensional WL. Structural characterization (X-ray diffraction (XRD)) and transmission electron microscopy (TEM)) reveal an increase in the QD indium content over the WL indium content which is due to strain induced drifts. © 2011 IEEE.

  17. Precipitation of metal nitrides from chloride melts

    International Nuclear Information System (INIS)

    Slater, S.A.; Miller, W.E.; Willit, J.L.

    1996-01-01

    Precipitation of actinides, lanthanides, and fission products as nitrides from molten chloride melts is being investigated for use as a final cleanup step in treating radioactive salt wastes generated by electrometallurgical processing of spent nuclear fuel. The radioactive components (eg, fission products) need to be removed to reduce the volume of high-level waste that requires disposal. To extract the fission products from the salt, a nitride precipitation process is being developed. The salt waste is first contacted with a molten metal; after equilibrium is reached, a nitride is added to the metal phase. The insoluble nitrides can be recovered and converted to a borosilicate glass after air oxidation. For a bench-scale experimental setup, a crucible was designed to contact the salt and metal phases. Solubility tests were performed with candidate nitrides and metal nitrides for which there are no solubility data. Experiments were performed to assess feasibility of precipitation of metal nitrides from chloride melts

  18. 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

  19. High-performance lithium battery anodes using silicon nanowires.

    Science.gov (United States)

    Chan, Candace K; Peng, Hailin; Liu, Gao; McIlwrath, Kevin; Zhang, Xiao Feng; Huggins, Robert A; Cui, Yi

    2008-01-01

    There is great interest in developing rechargeable lithium batteries with higher energy capacity and longer cycle life for applications in portable electronic devices, electric vehicles and implantable medical devices. Silicon is an attractive anode material for lithium batteries because it has a low discharge potential and the highest known theoretical charge capacity (4,200 mAh g(-1); ref. 2). Although this is more than ten times higher than existing graphite anodes and much larger than various nitride and oxide materials, silicon anodes have limited applications because silicon's volume changes by 400% upon insertion and extraction of lithium which results in pulverization and capacity fading. Here, we show that silicon nanowire battery electrodes circumvent these issues as they can accommodate large strain without pulverization, provide good electronic contact and conduction, and display short lithium insertion distances. We achieved the theoretical charge capacity for silicon anodes and maintained a discharge capacity close to 75% of this maximum, with little fading during cycling.

  20. 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

  1. GaN Nanowire Devices: Fabrication and Characterization

    Science.gov (United States)

    Scott, Reum

    The development of microelectronics in the last 25 years has been characterized by an exponential increase of the bit density in integrated circuits (ICs) with time. Scaling solid-state devices improves cost, performance, and power; as such, it is of particular interest for companies, who gain a market advantage with the latest technology. As a result, the microelectronics industry has driven transistor feature size scaling from 10 μm to ~30 nm during the past 40 years. This trend has persisted for 40 years due to optimization, new processing techniques, device structures, and materials. But when noting processor speeds from the 1970's to 2009 and then again in 2010, the implication would be that the trend has ceased. To address the challenge of shrinking the integrated circuit (IC), current research is centered on identifying new materials and devices that can supplement and/or potentially supplant it. Bottom-up methods tailor nanoscale building blocks---atoms, molecules, quantum dots, and nanowires (NWs)---to be used to overcome these limitations. The Group IIIA nitrides (InN, AlN, and GaN) possess appealing properties such as a direct band gap spanning the whole solar spectrum, high saturation velocity, and high breakdown electric field. As a result nanostructures and nanodevices made from GaN and related nitrides are suitable candidates for efficient nanoscale UV/ visible light emitters, detectors, and gas sensors. To produce devices with such small structures new fabrication methods must be implemented. Devices composed of GaN nanowires were fabricated using photolithography and electron beam lithography. The IV characteristics of these devices were noted under different illuminations and the current tripled from 4.8*10-7 A to 1.59*10 -6 A under UV light which persisted for at least 5hrs.

  2. Reaction-bonded silicon nitride

    International Nuclear Information System (INIS)

    Porz, F.

    1982-10-01

    Reaction-bonded silicon nitride (RBSN) has been characterized. The oxidation behaviour in air up to 1500 0 C and 3000 h and the effects of static and cyclic oxidation on room-temperature strength have been studied. (orig./IHOE) [de

  3. Superconducting nanowire single-photon detectors (SNSPDs) on SOI for near-infrared range

    Energy Technology Data Exchange (ETDEWEB)

    Trojan, Philipp; Il' in, Konstantin; Henrich, Dagmar; Hofherr, Matthias; Doerner, Steffen; Siegel, Michael [Institut fuer Mikro- und Nanoelektronische Systeme (IMS), Karlsruher Institut fuer Technologie (KIT) (Germany); Semenov, Alexey [Institut fuer Planetenforschung, DLR, Berlin-Adlershof (Germany); Huebers, Heinz-Wilhelm [Institut fuer Planetenforschung, DLR, Berlin-Adlershof (Germany); Institut fuer Optik und Atomare Physik, Technische Universitaet Berlin (Germany)

    2013-07-01

    Superconducting nanowire single-photon detectors are promising devices for photon detectors with high count rates, low dark count rates and low dead times. At wavelengths beyond the visible range, the detection efficiency of today's SNSPDs drops significantly. Moreover, the low absorption in ultra-thin detector films is a limiting factor over the entire spectral range. Solving this problem requires approaches for an enhancement of the absorption range in feeding the light to the detector element. A possibility to obtain a better absorption is the use of multilayer substrate materials for photonic waveguide structures. We present results on development of superconducting nanowire single-photon detectors made from niobium nitride on silicon-on-insulator (SOI) multilayer substrates. Optical and superconducting properties of SNSPDs on SOI will be discussed and compared with the characteristics of detectors on common substrates.

  4. Optical properties of photodetectors based on single GaN nanowires with a transparent graphene contact

    Energy Technology Data Exchange (ETDEWEB)

    Babichev, A. V., E-mail: A.Babichev@mail.ioffe.ru [Russian Academy of Sciences, Ioffe Institute (Russian Federation); Zhang, H.; Guan, N. [University Paris Saclay, Institut d’Electronique Fondamentale, UMR 8622 CNRS (France); Egorov, A. Yu. [ITMO University (Russian Federation); Julien, F. H.; Messanvi, A. [University Paris Saclay, Institut d’Electronique Fondamentale, UMR 8622 CNRS (France); Durand, C.; Eymery, J. [University Grenoble Alpes (France); Tchernycheva, M. [University Paris Saclay, Institut d’Electronique Fondamentale, UMR 8622 CNRS (France)

    2016-08-15

    We report the fabrication and optical and electrical characterization of photodetectors for the UV spectral range based on single p–n junction nanowires with a transparent contact of a new type. The contact is based on CVD-grown (chemical-vapor deposition) graphene. The active region of the nitride nanowires contains a set of 30 radial In{sub 0.18}Ga{sub 0.82}N/GaN quantum wells. The structure is grown by metal-organic vaporphase epitaxy. The photodetectors are fabricated using electron-beam lithography. The current–voltage characteristics exhibit a rectifying behavior. The spectral sensitivity of the photodetector is recorded starting from 3 eV and extending far in the UV range. The maximal photoresponse is observed at a wavelength of 367 nm (sensitivity 1.9 mA/W). The response switching time of the photodetector is less than 0.1 s.

  5. Hints of hybridizing Majorana fermions in a nanowire coupled to superconducting leads

    Science.gov (United States)

    Finck, A. D. K.; van Harlingen, D. J.; Mohseni, P. K.; Jung, K.; Li, X.

    2013-03-01

    It has been proposed that a nanowire with strong spin-orbit coupling that is contacted with a conventional superconductor and subjected to a large magnetic field can be driven through a topological phase transition. In this regime, the two ends of the nanowire together host a pair of quasi-particles known as Majorana fermions (MFs). A key feature of MFs is that they are pinned to zero energy when the topological nanowire is long enough such that the wave functions of the two MFs do not overlap significantly, resulting in a zero bias anomaly (ZBA). It has been recently predicted that changes in external parameters can vary the wave function overlap and cause the MFs to hybridize in an oscillatory fashion. This would lead to a non-monotonic splitting or broadening of the ZBA and help distinguish MF transport signatures from a Kondo effect. Here, we present transport studies of an InAs nanowire contacted with niobium nitride leads in high magnetic fields. We observe a number of robust ZBAs that can persist for a wide range of back gate bias and magnetic field strength. Under certain conditions, we find that the height and width of the ZBA can oscillate with back gate bias or magnetic field. This work was supported by Microsoft Project Q.

  6. Superconductivity in nanowires

    CERN Document Server

    Bezryadin, Alexey

    2012-01-01

    The importance and actuality of nanotechnology is unabated and will be for years to come. A main challenge is to understand the various properties of certain nanostructures, and how to generate structures with specific properties for use in actual applications in Electrical Engineering and Medicine.One of the most important structures are nanowires, in particular superconducting ones. They are highly promising for future electronics, transporting current without resistance and at scales of a few nanometers. To fabricate wires to certain defined standards however, is a major challenge, and so i

  7. Optical Binding of Nanowires

    Czech Academy of Sciences Publication Activity Database

    Simpson, Stephen Hugh; Zemánek, Pavel; Marago, O.M.; Jones, P.H.; Hanna, S.

    2017-01-01

    Roč. 17, č. 6 (2017), s. 3485-3492 ISSN 1530-6984 R&D Projects: GA ČR GB14-36681G Grant - others:AV ČR(CZ) CNR-16-12 Program:Bilaterální spolupráce Institutional support: RVO:68081731 Keywords : optical binding nanowires * Brownian motion * self-organization * non-equilibrium thermodynamics * non-equilibrium steady state * spin-orbit coupling * emergent phenomena Subject RIV: BH - Optics, Masers, Lasers OBOR OECD: Optics (including laser optics and quantum optics) Impact factor: 12.712, year: 2016

  8. Automated realization of the gallium melting and triple points

    Science.gov (United States)

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

    2013-09-01

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

  9. State of rare earth impurities in gallium and indium antimonides

    International Nuclear Information System (INIS)

    Evgen'ev, S.B.; Kuz'micheva, G.M.

    1990-01-01

    State of rare earth impurities in indium and gallium antimonides was studied. Results of measuring density and lattice parameter of samples in GaSb-rare earth and InSb-rare earth systems are presented. It is shown that during rare earth dissolution in indium and gallium antimonides rare earth atoms occupy interstitial positions or, at least, are displaced from lattice points

  10. Contact planarization of ensemble nanowires

    Science.gov (United States)

    Chia, A. C. E.; LaPierre, R. R.

    2011-06-01

    The viability of four organic polymers (S1808, SC200, SU8 and Cyclotene) as filling materials to achieve planarization of ensemble nanowire arrays is reported. Analysis of the porosity, surface roughness and thermal stability of each filling material was performed. Sonication was used as an effective method to remove the tops of the nanowires (NWs) to achieve complete planarization. Ensemble nanowire devices were fully fabricated and I-V measurements confirmed that Cyclotene effectively planarizes the NWs while still serving the role as an insulating layer between the top and bottom contacts. These processes and analysis can be easily implemented into future characterization and fabrication of ensemble NWs for optoelectronic device applications.

  11. Andreev molecules in semiconductor nanowire double quantum dots.

    Science.gov (United States)

    Su, Zhaoen; Tacla, Alexandre B; Hocevar, Moïra; Car, Diana; Plissard, Sébastien R; Bakkers, Erik P A M; Daley, Andrew J; Pekker, David; Frolov, Sergey M

    2017-09-19

    Chains of quantum dots coupled to superconductors are promising for the realization of the Kitaev model of a topological superconductor. While individual superconducting quantum dots have been explored, control of longer chains requires understanding of interdot coupling. Here, double quantum dots are defined by gate voltages in indium antimonide nanowires. High transparency superconducting niobium titanium nitride contacts are made to each of the dots in order to induce superconductivity, as well as probe electron transport. Andreev bound states induced on each of dots hybridize to define Andreev molecular states. The evolution of these states is studied as a function of charge parity on the dots, and in magnetic field. The experiments are found in agreement with a numerical model.Quantum dots in a nanowire are one possible approach to creating a solid-state quantum simulator. Here, the authors demonstrate the coupling of electronic states in a double quantum dot to form Andreev molecule states; a potential building block for longer chains suitable for quantum simulation.

  12. 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.

  13. Interactions between semiconductor nanowires and living cells.

    Science.gov (United States)

    Prinz, Christelle N

    2015-06-17

    Semiconductor nanowires are increasingly used for biological applications and their small dimensions make them a promising tool for sensing and manipulating cells with minimal perturbation. In order to interface cells with nanowires in a controlled fashion, it is essential to understand the interactions between nanowires and living cells. The present paper reviews current progress in the understanding of these interactions, with knowledge gathered from studies where living cells were interfaced with vertical nanowire arrays. The effect of nanowires on cells is reported in terms of viability, cell-nanowire interface morphology, cell behavior, changes in gene expression as well as cellular stress markers. Unexplored issues and unanswered questions are discussed.

  14. Gallium-containing hydroxyapatite for potential use in orthopedics

    International Nuclear Information System (INIS)

    Melnikov, P.; Teixeira, A.R.; Malzac, A.; Coelho, M. de B.

    2009-01-01

    A novel material that may be recommended for grafts and implants stimulating bone growth has been obtained by introducing gallium ions (up to 11.0 mass%) into crystalline lattice of hydroxyapatite. The doping was carried out using gallium nitrate and sodium gallate solutions. In both cases, lattice parameters of gallium-doped hydroxyapatite are identical to those of pure synthetic hydroxyapatite. Gallium does not replace calcium as a result of heterovalent substitution and consequently produces no distortions in the framework of hydroxyapatite matrix. It remains strongly fixed in the form of solid solution of intercalation. According to scanning electron microscopy images gallium insertion does not cause any morphological alterations in hydroxyapatite structure and the product developed meets physico-chemical criteria for biomaterial to be employed in orthopedic practice and local handling of traumatic injuries. Its future usage opens the opportunity to enhance osteosynthesis and calcium retention in loco.

  15. Nuclear microprobe imaging of gallium nitrate in cancer cells

    Science.gov (United States)

    Ortega, Richard; Suda, Asami; Devès, Guillaume

    2003-09-01

    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.

  16. 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

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

    International Nuclear Information System (INIS)

    Lin, Y. H.; Chou, J. C.

    2015-01-01

    We investigated amorphous indium gallium zinc oxide (a-IGZO) thin film transistors (TFT_s) using different high-Κ gate dielectric materials such as silicon nitride (Si_3N_4) and aluminum oxide (Al_2O_3) at low temperature process (<300 degree) and compared them with low temperature silicon dioxide (SiO_2). The IGZO device with high-Κ 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, post annealing treatment is an essential process for completing the process. The chemical reaction of the high-κ/IGZO interface due to heat formation in high-Κ/IGZO materials results in reliability issue. We also used the voltage stress for testing the reliability for the device with different high-Κ gate dielectric materials and explained the interface effect by charge band diagram.

  18. 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

  19. Nitridation of one-dimensional tungsten oxide nanostructures: Changes in structure and photoactivity

    KAUST Repository

    Varga, Tamás

    2017-10-12

    In the search for stable, visible light active photoelectrodes, hydrothermally synthesized tungsten oxide nanowires were modified via nitrogen incorporation into their structure. To this end, nanowires were heat-treated in ammonia/nitrogen atmosphere at different temperatures. This procedure caused transitions in their structure that were investigated along with the photoelectrochemical properties of the samples. Results were subsequently compared to the reference samples treated in inert nitrogen atmosphere. Morphological changes and structural transitions were followed by transmission and scanning electron microscopy and X-ray diffraction. Bandgap energies were determined from the UV–vis spectra of the materials, while photoelectrochemical properties were tested by linear sweep photovoltammetry and electrochemical impedance spectroscopy. Pristine tungsten oxide nanowires were first transformed into tungsten oxynitride and then tungsten nitride during high-temperature calcination in ammonia atmosphere. Electron microscopic investigation revealed that, along with phase transition, the initial fibrous morphology gradually converted into nanosheets. Simultaneously, bandgap energies significantly decreased in the calcination process, too. Photoelectrochemical measurements demonstrated that photoactivity in the treated samples was not improved by the decrease of the bandgap. This behavior might be explained with the deterioration of charge carrier transport properties of the materials due to the increased number of structural defects (acting as trap states), and current ongoing work aims to verify this notion.

  20. III-Nitride Membranes for Thermal Bio-Sensing and Solar Hydrogen Generation

    KAUST Repository

    Elafandy, Rami Tarek Mahmoud

    2017-09-01

    III-nitride nanostructures have generated tremendous scientific and technological interests in studying and engineering their low dimensional physics phenomena. Among these, 2D planar, free standing III-nitride nanomembranes are unrivalled in their scalability for high yield manufacture and can be mechanically manipulated. Due to the increase in their surface to volume ratio and the manifestation of quantum phenomena, these nanomembranes acquire unique physical properties. Furthermore, III-nitride membranes are chemically stable and biocompatible. Finally, nanomembranes are highly flexible and can follow curvilinear surfaces present in biological systems. However, being free-standing, requires especially new techniques for handling nanometers or micrometers thick membrane devices. Furthermore, effectively transferring these membrane devices to other substrates is not a direct process which requires the use of photoresists, solvents and/or elastomers. Finally, as the membranes are transferred, they need to be properly attached for subsequent device fabrications, which often includes spin coating and rinsing steps. These engineering complications have impeded the development of novel devices based on III-nitride membranes. In this thesis, we demonstrate the versatility of III-nitride membranes where we develop a thermal bio-sensor nanomembrane and solar energy photo-anode membrane. First, we present a novel preparation technique of nanomembranes with new characteristics; having no threading dislocation cores. We then perform optical characterization to reveal changes in their defect densities compared to the bulk crystal. We also study their mechanical properties where we successfully modulate their bandgap emission by 55 meV through various external compressive and tensile strain fields. Furthermore, we characterize the effect of phonon-boundary scattering on their thermal properties where we report a reduction of thermal conductivity from 130 to 9 W/mK. We employ

  1. Electric Conductivity of Phosphorus Nanowires

    International Nuclear Information System (INIS)

    Jing-Xiang, Zhang; Hui, Li; Xue-Qing, Zhang; Kim-Meow, Liew

    2009-01-01

    We present the structures and electrical transport properties of nanowires made from different strands of phosphorus chains encapsulated in carbon nanotubes. Optimized by density function theory, our results indicate that the conductance spectra reveal an oscillation dependence on the size of wires. It can be seen from the density of states and current-voltage curves that the structure of nanowires affects their properties greatly. Among them, the DNA-like double-helical phosphorus nanowire exhibits the distinct characteristic of an approximately linear I – V relationship and has a higher conductance than others. The transport properties of phosphorus nanowires are highly correlated with their microstructures. (condensed matter: structure, mechanical and thermal properties)

  2. Tunneling magnetoresistance in Si nanowires

    KAUST Repository

    Montes Muñ oz, Enrique; Rungger, I.; Sanvito, S.; Schwingenschlö gl, Udo

    2016-01-01

    for quantum transport. Silicon nanowires represent an interesting platform for spin devices. They are compatible with mature silicon technology and their intrinsic electronic properties can be controlled by modifying the diameter and length. Here we

  3. Patterned gallium surfaces as molecular mirrors.

    Science.gov (United States)

    Bossi, Alessandra; Rivetti, Claudio; Mangiarotti, Laura; Whitcombe, Michael J; Turner, Anthony P F; Piletsky, Sergey A

    2007-09-30

    An entirely new means of printing molecular information on a planar film, involving casting nanoscale impressions of the template protein molecules in molten gallium, is presented here for the first time. The metallic imprints not only replicate the shape and size of the proteins used as template. They also show specific binding for the template species. Such a simple approach to the creation of antibody-like properties in metallic mirrors can lead to applications in separations, microfluidic devices, and the development of new optical and electronic sensors, and will be of interest to chemists, materials scientists, analytical specialists, and electronic engineers.

  4. 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

  5. Silicon nitride-fabrication, forming and properties

    International Nuclear Information System (INIS)

    Yehezkel, O.

    1983-01-01

    This article, which is a literature survey of the recent years, includes description of several methods for the formation of silicone nitride, and five methods of forming: Reaction-bonded silicon nitride, sintering, hot pressing, hot isostatic pressing and chemical vapour deposition. Herein are also included data about mechanical and physical properties of silicon nitride and the relationship between the forming method and the properties. (author)

  6. Biotemplated Synthesis of PZT Nanowires

    Science.gov (United States)

    2013-11-25

    electromechanical coupling coefficient , Y is the Young’s modulus, and Ri is intrinsic resistance. The PZT nanowire- based film is taken to have negligible...robotic actuation, and bioMEMS. Lead zirconate titanate ( PZT ), in particular, has attracted significant attention, owing to its superior...electromechanical conversion performance. Yet, the ability to synthesize crystalline PZT nanowires with reproducible and well-controlled properties remains a

  7. Silicon nanowires: structure and properties

    International Nuclear Information System (INIS)

    Nezhdanov, A.V.; Mashin, A.I.; Razuvaev, A.G.; Ershov, A.V.; Ignatov, S.K.

    2006-01-01

    An attempt to grow silicon nanowires has been made by electron beam evaporation on highly oriented pyrolytic substrate. Needle-like objects are located along the normal to a substrate (density 2 x 10 11 cm -2 ). For modeling quasi-one-dimensional objects calculations of nuclear structure and energy spectra have been accomplished. A fullerene-like structure Si 24 is proposed as a basic atomic configuration of silicon nanowires [ru

  8. Topotactic synthesis of vanadium nitride solid foams

    International Nuclear Information System (INIS)

    Oyama, S.T.; Kapoor, R.; Oyama, H.T.; Hofmann, D.J.; Matijevic, E.

    1993-01-01

    Vanadium nitride has been synthesized with a surface area of 120 m 2 g -1 by temperature programmed nitridation of a foam-like vanadium oxide (35 m 2 g -1 ), precipitated from vanadate solutions. The nitridation reaction was established to be topotactic and pseudomorphous by x-ray powder diffraction and scanning electron microscopy. The crystallographic relationship between the nitride and oxide was {200}//{001}. The effect of precursor geometry on the product size and shape was investigated by employing vanadium oxide solids of different morphologies

  9. Microhardness and microplasticity of zirconium nitride

    International Nuclear Information System (INIS)

    Neshpor, V.S.; Eron'yan, M.A.; Petrov, A.N.; Kravchik, A.E.

    1978-01-01

    To experimentally check the concentration dependence of microhardness of 4 group nitrides, microhardness of zirconium nitride compact samples was measured. The samples were obtained either by bulk saturation of zirconium iodide plates or by chemical precipitation from gas. As nitrogen content decreased within the limits of homogeneity of zirconium nitride samples where the concentration of admixed oxygen was low, the microhardness grew from 1500+-100 kg/mm 2 for ZrNsub(1.0) to 27000+-100 kg/mm 2 for ZrNsub(0.78). Microplasticity of zirconium nitride (resistance to fracture) decreased, as the concentration of nitrogen vacancies was growing

  10. Electrochemically grown rough-textured nanowires

    International Nuclear Information System (INIS)

    Tyagi, Pawan; Postetter, David; Saragnese, Daniel; Papadakis, Stergios J.; Gracias, David H.

    2010-01-01

    Nanowires with a rough surface texture show unusual electronic, optical, and chemical properties; however, there are only a few existing methods for producing these nanowires. Here, we describe two methods for growing both free standing and lithographically patterned gold (Au) nanowires with a rough surface texture. The first strategy is based on the deposition of nanowires from a silver (Ag)-Au plating solution mixture that precipitates an Ag-Au cyanide complex during electrodeposition at low current densities. This complex disperses in the plating solution, thereby altering the nanowire growth to yield a rough surface texture. These nanowires are mass produced in alumina membranes. The second strategy produces long and rough Au nanowires on lithographically patternable nickel edge templates with corrugations formed by partial etching. These rough nanowires can be easily arrayed and integrated with microscale devices.

  11. Structural and tunneling properties of Si nanowires

    KAUST Repository

    Montes Muñoz, Enrique

    2013-12-06

    We investigate the electronic structure and electron transport properties of Si nanowires attached to Au electrodes from first principles using density functional theory and the nonequilibrium Green\\'s function method. We systematically study the dependence of the transport properties on the diameter of the nanowires, on the growth direction, and on the length. At the equilibrium Au-nanowire distance we find strong electronic coupling between the electrodes and nanowires, which results in a low contact resistance. With increasing nanowire length we study the transition from metallic to tunneling conductance for small applied bias. For the tunneling regime we investigate the decay of the conductance with the nanowire length and rationalize the results using the complex band structure of the pristine nanowires. The conductance is found to depend strongly on the growth direction, with nanowires grown along the ⟨110⟩ direction showing the smallest decay with length and the largest conductance and current.

  12. Structural and tunneling properties of Si nanowires

    KAUST Repository

    Montes Muñ oz, Enrique; Gkionis, Konstantinos; Rungger, Ivan; Sanvito, Stefano; Schwingenschlö gl, Udo

    2013-01-01

    We investigate the electronic structure and electron transport properties of Si nanowires attached to Au electrodes from first principles using density functional theory and the nonequilibrium Green's function method. We systematically study the dependence of the transport properties on the diameter of the nanowires, on the growth direction, and on the length. At the equilibrium Au-nanowire distance we find strong electronic coupling between the electrodes and nanowires, which results in a low contact resistance. With increasing nanowire length we study the transition from metallic to tunneling conductance for small applied bias. For the tunneling regime we investigate the decay of the conductance with the nanowire length and rationalize the results using the complex band structure of the pristine nanowires. The conductance is found to depend strongly on the growth direction, with nanowires grown along the ⟨110⟩ direction showing the smallest decay with length and the largest conductance and current.

  13. A silicon nanowire heater and thermometer

    Science.gov (United States)

    Zhao, Xingyan; Dan, Yaping

    2017-07-01

    In the thermal conductivity measurements of thermoelectric materials, heaters and thermometers made of the same semiconducting materials under test, forming a homogeneous system, will significantly simplify fabrication and integration. In this work, we demonstrate a high-performance heater and thermometer made of single silicon nanowires (SiNWs). The SiNWs are patterned out of a silicon-on-insulator wafer by CMOS-compatible fabrication processes. The electronic properties of the nanowires are characterized by four-probe and low temperature Hall effect measurements. The I-V curves of the nanowires are linear at small voltage bias. The temperature dependence of the nanowire resistance allows the nanowire to be used as a highly sensitive thermometer. At high voltage bias, the I-V curves of the nanowire become nonlinear due to the effect of Joule heating. The temperature of the nanowire heater can be accurately monitored by the nanowire itself as a thermometer.

  14. Controlling nanowire emission profile using conical taper

    DEFF Research Database (Denmark)

    Gregersen, Niels; Nielsen, Torben Roland; Mørk, Jesper

    2008-01-01

    The influence of a conical taper on nanowire light emission is studied. For nanowires with divergent output beams, the introduction of tapers improves the emission profile and increase the collection efficiency of the detection optics....

  15. The investigation of alloy formation during InAs nanowires growth on GaAs (111)B substrate

    Energy Technology Data Exchange (ETDEWEB)

    Saqib, Muhammad; Biermanns, Andreas; Davydok, Anton; Pietsch, Ullrich [Festkoerperphysik, Universitaet Siegen, Walter-Flex-Str. 3, Siegen 57072 (Germany); Rieger, Torsten; Grap, Thomas; Lepsa, Mihail [Peter Gruenberg Institute (PGI-9), Forschungzentrum Juelich, Juelich 52425 (Germany)

    2013-07-01

    A possible way to obtain nanowires is the growth in molecular beam epitaxy (MBE) on the (111) oriented surface of the desired substrate, covered by a thin oxide layer. A crucial parameter in this method is the initial thickness of the oxide layer, often determined by an etching procedure. In this contribution, we report on the structural investigation of two different series (etched and unetched) of NWs samples. Vertically aligned InAs nanowires (NWs) doped with Si were self-assisted grown by molecular beam epitaxy on GaAs [111]B substrates covered with a thin SiO{sub x} layer. Using a combination of symmetric and asymmetric X-ray diffraction we study the influence of Si supply on the growth process and nanostructure formation. We find that the number of parasitic crystallites grown between the NWs increases with increasing Si flux. In addition, we observe the formation of a Ga{sub 0.2}In{sub 0.8}As alloy if the growth is performed on samples covered by a defective (etched) oxide layer. This alloy formation is observed within the crystallites and not within the nanowires. The Gallium concentration is determined from the lattice mismatch of the crystallites relative to the InAs nanowires. No alloy formation is found for samples with faultless oxide layers.

  16. Semiconducting silicon nanowires for biomedical applications

    CERN Document Server

    Coffer, JL

    2014-01-01

    Biomedical applications have benefited greatly from the increasing interest and research into semiconducting silicon nanowires. Semiconducting Silicon Nanowires for Biomedical Applications reviews the fabrication, properties, and applications of this emerging material. The book begins by reviewing the basics, as well as the growth, characterization, biocompatibility, and surface modification, of semiconducting silicon nanowires. It goes on to focus on silicon nanowires for tissue engineering and delivery applications, including cellular binding and internalization, orthopedic tissue scaffol

  17. Electrochemical synthesis of highly crystalline copper nanowires

    International Nuclear Information System (INIS)

    Kaur, Amandeep; Gupta, Tanish; Kumar, Akshay; Kumar, Sanjeev; Singh, Karamjeet; Thakur, Anup

    2015-01-01

    Copper nanowires were fabricated within the pores of anodic alumina template (AAT) by template synthesis method at pH = 2.9. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to investigate the structure, morphology and composition of fabricated nanowires. These characterizations revealed that the deposited copper nanowires were highly crystalline in nature, dense and uniform. The crystalline copper nanowires are promising in application of future nanoelectronic devices and circuits

  18. 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

  19. Characterization of Bending Magnetostriction in Iron-Gallium Alloys for Nanowire Sensor Applications

    Science.gov (United States)

    2008-01-01

    10], hydrodynamic imaging via the lateral lines of fish [29, 28, 19, 162] for tracking obstacles and prey, and acoustic transduction in the cochlea...cleanliness of the chamber, the contamination of the surface, and the beam parameters, but typically within a few minutes a blob of glue will form at the...Enigmatic lateral line system. In A. N. Popper, editor, Comparative Hearing. Fish and Amphibians. Springer, New York, 1999. [30] J. R. Cullen, A. E. Clark, M

  20. From dopyballs to nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Smalley, R E [Rice Quantum Inst. and Depts. of Chemistry and Physics, Rice Univ., Houston, TX (United States)

    1993-04-19

    Consideration of the factors involved in the production of fullerene nanotubes in carbon arcs leads to the notion that a high electric field may be the critical factor that causes the tubes to grow. This thought then leads to a suggestion that it may be possible to grow continuous fullerene fibers many centimeters in length by an electric-field-and-laser induced pyrolysis of gas phase hydrocarbons of fullerenes on the tip of the growing fiber as it extends out from its place of attachment on a high voltage needle. Use of metal- or boron-doped fullerenes (dopyballs) in such an apparatus may lead to the production of doped fullerene fiber nanowires of high strength and conductivity. (orig.)

  1. Indium Arsenide Nanowires

    DEFF Research Database (Denmark)

    Madsen, Morten Hannibal

    -ray diffraction. InAs NWs can be used in a broad range of applications, including detectors, high speed electronics and low temperature transport measurements, but in this thesis focus will be put on biological experiments on living cells. Good control of Au-assisted InAs NW growth has been achieved......This thesis is about growth of Au-assisted and self-assisted InAs nanowires (NWs). The wires are synthesized using a solid source molecular beam epitaxy (MBE) system and characterized with several techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM) and x...... by a systematic study to optimize the growth conditions; first the Au deposition, then the growth temperature and finally the beam fluxes. For further control of the growth, Au droplets have been positioned with electron beam lithography and large scale arrays with a > 99 % yield have been made on 2 inch...

  2. Resonance of curved nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Calabri, L [CNR-INFM-National Research Center on nanoStructures and bioSystems at Surfaces (S3), Via Campi 213/a, 41100 Modena (Italy); Pugno, N [Department of Structural Engineering and Geotechnics, Politecnico di Torino, Turin (Italy); Ding, W [Department of Mechanical Engineering, Northwestern University, Evanston, IL 60208-3111 (United States); Ruoff, R S [Department of Mechanical Engineering, Northwestern University, Evanston, IL 60208-3111 (United States)

    2006-08-23

    The effects of non-ideal experimental configuration on the mechanical resonance of boron (B) nanowires (NWs) were studied to obtain the corrected value for the Young's modulus. The following effects have been theoretically considered: (i) the presence of intrinsic curvature (ii) non-ideal clamps (iii) spurious masses (iv) coating layer, and (v) large displacements. An energy-based analytical analysis was developed to treat such effects and their interactions. Here, we focus on treating the effect of the intrinsic curvature on the mechanical resonance. The analytical approach has been confirmed by numerical FEM analysis. A parallax method was used to obtain the three-dimensional geometry of the NW.

  3. 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.

  4. Corrosion detection of nanowires by magnetic sensors

    KAUST Repository

    Kosel, Jü rgen; Amara, Selma; Ivanov, Iurii; Blanco, Mario

    2017-01-01

    Disclosed are various embodiments related to a corrosion detection device for detecting corrosive environments. A corrosion detection device comprises a magnetic sensor and at least one magnetic nanowire disposed on the magnetic sensor. The magnetic sensor is configured to detect corrosion of the one or more magnetic nanowires based at least in part on a magnetic field of the one or more magnetic nanowires.

  5. Corrosion detection of nanowires by magnetic sensors

    KAUST Repository

    Kosel, Jürgen

    2017-10-05

    Disclosed are various embodiments related to a corrosion detection device for detecting corrosive environments. A corrosion detection device comprises a magnetic sensor and at least one magnetic nanowire disposed on the magnetic sensor. The magnetic sensor is configured to detect corrosion of the one or more magnetic nanowires based at least in part on a magnetic field of the one or more magnetic nanowires.

  6. Proportional counter response calculations for gallium solar neutrino detectors

    International Nuclear Information System (INIS)

    Kouzes, R.T.; Reynolds, D.

    1989-01-01

    Gallium bases solar neutrino detectors are sensitive to the primary pp reaction in the sun. Two experiments using gallium, SAGE in the Soviet Union and GALLEX in Europe, are under construction and will produce data by 1989. The radioactive /sup 71/Ge produced by neutrinos interacting with the gallium detector material, is chemically extracted and counted in miniature proportional counters. A number of calculations have been carried out to simulate the response of these counters to the decay of /sup 71/Ge and to background events

  7. Topological insulator nanowires and nanowire hetero-junctions

    Science.gov (United States)

    Deng, Haiming; Zhao, Lukas; Wade, Travis; Konczykowski, Marcin; Krusin-Elbaum, Lia

    2014-03-01

    The existing topological insulator materials (TIs) continue to present a number of challenges to complete understanding of the physics of topological spin-helical Dirac surface conduction channels, owing to a relatively large charge conduction in the bulk. One way to reduce the bulk contribution and to increase surface-to-volume ratio is by nanostructuring. Here we report on the synthesis and characterization of Sb2Te3, Bi2Te3 nanowires and nanotubes and Sb2Te3/Bi2Te3 heterojunctions electrochemically grown in porous anodic aluminum oxide (AAO) membranes with varied (from 50 to 150 nm) pore diameters. Stoichiometric rigid polycrystalline nanowires with controllable cross-sections were obtained using cell voltages in the 30 - 150 mV range. Transport measurements in up to 14 T magnetic fields applied along the nanowires show Aharonov-Bohm (A-B) quantum oscillations with periods corresponding to the nanowire diameters. All nanowires were found to exhibit sharp weak anti-localization (WAL) cusps, a characteristic signature of TIs. In addition to A-B oscillations, new quantization plateaus in magnetoresistance (MR) at low fields (< 0 . 7T) were observed. The analysis of MR as well as I - V characteristics of heterojunctions will be presented. Supported in part by NSF-DMR-1122594, NSF-DMR-1312483-MWN, and DOD-W911NF-13-1-0159.

  8. Photoelectrochemistry of III-V epitaxial layers and nanowires for solar energy conversion

    Science.gov (United States)

    Parameshwaran, Vijay; Enck, Ryan; Chung, Roy; Kelley, Stephen; Sampath, Anand; Reed, Meredith; Xu, Xiaoqing; Clemens, Bruce

    2017-05-01

    III-V materials, which exhibit high absorption coefficients and charge carrier mobility, are ideal templates for solar energy conversion applications. This work describes the photoelectrochemistry research in several IIIV/electrolyte junctions as an enabler for device design for solar chemical reactions. By designing lattice-matched epitaxial growth of InGaP and GaP on GaAs and Si, respectively, extended depletion region electrodes achieve photovoltages which provide an additional boost to the underlying substrate photovoltage. The InGaP/GaAs and GaP/Si electrodes drive hydrogen evolution currents under aqueous conditions. By using nanowires of InN and InP under carefully controlled growth conditions, current and capacitance measurements are obtained to reveal the nature of the nanowire-electrolyte interface and how light is translated into photocurrent for InP and a photovoltage in InN. The materials system is expanded into the III-V nitride semiconductors, in which it is shown that varying the morphology of GaN on silicon yields insights to how the interface and light conversion is modulated as a basis for future designs. Current extensions of this work address growth and tuning of the III-V nitride electrodes with doping and polarization engineering for efficient coupling to solar-driven chemical reactions, and rapid-throughput methods for III-V nanomaterials synthesis in this materials space.

  9. Method of preparation of uranium nitride

    Science.gov (United States)

    Kiplinger, Jaqueline Loetsch; Thomson, Robert Kenneth James

    2013-07-09

    Method for producing terminal uranium nitride complexes comprising providing a suitable starting material comprising uranium; oxidizing the starting material with a suitable oxidant to produce one or more uranium(IV)-azide complexes; and, sufficiently irradiating the uranium(IV)-azide complexes to produce the terminal uranium nitride complexes.

  10. Atomic Resolution Microscopy of Nitrides in Steel

    DEFF Research Database (Denmark)

    Danielsen, Hilmar Kjartansson

    2014-01-01

    MN and CrMN type nitride precipitates in 12%Cr steels have been investigated using atomic resolution microscopy. The MN type nitrides were observed to transform into CrMN both by composition and crystallography as Cr diffuses from the matrix into the MN precipitates. Thus a change from one...

  11. Low temperature anodic bonding to silicon nitride

    DEFF Research Database (Denmark)

    Weichel, Steen; Reus, Roger De; Bouaidat, Salim

    2000-01-01

    Low-temperature anodic bonding to stoichiometric silicon nitride surfaces has been performed in the temperature range from 3508C to 4008C. It is shown that the bonding is improved considerably if the nitride surfaces are either oxidized or exposed to an oxygen plasma prior to the bonding. Both bu...

  12. Fusion bonding of silicon nitride surfaces

    DEFF Research Database (Denmark)

    Reck, Kasper; Østergaard, Christian; Thomsen, Erik Vilain

    2011-01-01

    While silicon nitride surfaces are widely used in many micro electrical mechanical system devices, e.g. for chemical passivation, electrical isolation or environmental protection, studies on fusion bonding of two silicon nitride surfaces (Si3N4–Si3N4 bonding) are very few and highly application...

  13. Alloy Effects on the Gas Nitriding Process

    Science.gov (United States)

    Yang, M.; Sisson, R. D.

    2014-12-01

    Alloy elements, such as Al, Cr, V, and Mo, have been used to improve the nitriding performance of steels. In the present work, plain carbon steel AISI 1045 and alloy steel AISI 4140 were selected to compare the nitriding effects of the alloying elements in AISI 4140. Fundamental analysis is carried out by using the "Lehrer-like" diagrams (alloy specific Lehrer diagram and nitriding potential versus nitrogen concentration diagram) and the compound layer growth model to simulate the gas nitriding process. With this method, the fundamental understanding for the alloy effect based on the thermodynamics and kinetics becomes possible. This new method paves the way for the development of new alloy for nitriding.

  14. Gold nanowires and the effect of impurities

    Directory of Open Access Journals (Sweden)

    Novaes Frederico

    2006-01-01

    Full Text Available AbstractMetal nanowires and in particular gold nanowires have received a great deal of attention in the past few years. Experiments on gold nanowires have prompted theory and simulation to help answer questions posed by these studies. Here we present results of computer simulations for the formation, evolution and breaking of very thin Au nanowires. We also discuss the influence of contaminants, such as atoms and small molecules, and their effect on the structural and mechanical properties of these nanowires.

  15. Micromagnetic simulations of cylindrical magnetic nanowires

    KAUST Repository

    Ivanov, Yurii P.

    2015-05-27

    This chapter reviews micromagnetic simulations of cylindrical magnetic nanowires and their ordered arrays. It starts with a description of the theoretical background of micromagnetism. The chapter discusses main magnetization reversal modes, domain wall types, and state diagrams in cylindrical nanowires of different types and sizes. The results of the hysteresis process in individual nanowires and nanowire arrays also are presented. Modeling results are compared with experimental ones. The chapter also discusses future trends in nanowire applications in relation to simulations, such as current-driven dynamics, spintronics, and spincaloritronics. The main micromagnetic programs are presented and discussed, together with the corresponding links.

  16. Ballistic superconductivity in semiconductor nanowires

    Science.gov (United States)

    Zhang, Hao; Gül, Önder; Conesa-Boj, Sonia; Nowak, Michał P.; Wimmer, Michael; Zuo, Kun; Mourik, Vincent; de Vries, Folkert K.; van Veen, Jasper; de Moor, Michiel W. A.; Bommer, Jouri D. S.; van Woerkom, David J.; Car, Diana; Plissard, Sébastien R; Bakkers, Erik P.A.M.; Quintero-Pérez, Marina; Cassidy, Maja C.; Koelling, Sebastian; Goswami, Srijit; Watanabe, Kenji; Taniguchi, Takashi; Kouwenhoven, Leo P.

    2017-01-01

    Semiconductor nanowires have opened new research avenues in quantum transport owing to their confined geometry and electrostatic tunability. They have offered an exceptional testbed for superconductivity, leading to the realization of hybrid systems combining the macroscopic quantum properties of superconductors with the possibility to control charges down to a single electron. These advances brought semiconductor nanowires to the forefront of efforts to realize topological superconductivity and Majorana modes. A prime challenge to benefit from the topological properties of Majoranas is to reduce the disorder in hybrid nanowire devices. Here we show ballistic superconductivity in InSb semiconductor nanowires. Our structural and chemical analyses demonstrate a high-quality interface between the nanowire and a NbTiN superconductor that enables ballistic transport. This is manifested by a quantized conductance for normal carriers, a strongly enhanced conductance for Andreev-reflecting carriers, and an induced hard gap with a significantly reduced density of states. These results pave the way for disorder-free Majorana devices. PMID:28681843

  17. Vibrational spectra of nanowires measured using laser doppler vibrometry and STM studies of epitaxial graphene : an LDRD fellowship report.

    Energy Technology Data Exchange (ETDEWEB)

    Biedermann, Laura Butler

    2009-09-01

    A few of the many applications for nanowires are high-aspect ratio conductive atomic force microscope (AFM) cantilever tips, force and mass sensors, and high-frequency resonators. Reliable estimates for the elastic modulus of nanowires and the quality factor of their oscillations are of interest to help enable these applications. Furthermore, a real-time, non-destructive technique to measure the vibrational spectra of nanowires will help enable sensor applications based on nanowires and the use of nanowires as AFM cantilevers (rather than as tips for AFM cantilevers). Laser Doppler vibrometry is used to measure the vibration spectra of individual cantilevered nanowires, specifically multiwalled carbon nanotubes (MWNTs) and silver gallium nanoneedles. Since the entire vibration spectrum is measured with high frequency resolution (100 Hz for a 10 MHz frequency scan), the resonant frequencies and quality factors of the nanowires are accurately determined. Using Euler-Bernoulli beam theory, the elastic modulus and spring constant can be calculated from the resonance frequencies of the oscillation spectrum and the dimensions of the nanowires, which are obtained from parallel SEM studies. Because the diameters of the nanowires studied are smaller than the wavelength of the vibrometer's laser, Mie scattering is used to estimate the lower diameter limit for nanowires whose vibration can be measured in this way. The techniques developed in this thesis can be used to measure the vibrational spectra of any suspended nanowire with high frequency resolution Two different nanowires were measured - MWNTs and Ag{sub 2}Ga nanoneedles. Measurements of the thermal vibration spectra of MWNTs under ambient conditions showed that the elastic modulus, E, of plasma-enhanced chemical vapor deposition (PECVD) MWNTs is 37 {+-} 26 GPa, well within the range of E previously reported for CVD-grown MWNTs. Since the Ag{sub 2}Ga nanoneedles have a greater optical scattering efficiency than

  18. 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...

  19. Fabrication and properties of gallium metallic photonic crystals

    International Nuclear Information System (INIS)

    Kozhevnikov, V.F.; Diwekar, M.; Kamaev, V.P.; Shi, J.; Vardeny, Z.V.

    2003-01-01

    Gallium metallic photonic crystals with 100% filling factor have been fabricated via infiltration of liquid gallium into opals of 300-nm silica spheres using a novel high pressure-high temperature technique. The electrical resistance of the Ga-opal crystals was measured at temperatures from 10 to 280 K. The data obtained show that Ga-opal crystals are metallic network with slightly smaller temperature coefficient of resistivity than that for bulk gallium. Optical reflectivity of bulk gallium, plain opal and several Ga-opal crystals were measured at photon energies from 0.3 to 6 eV. A pronounced photonic stop band in the visible spectral range was found in both the plain and Ga infiltrated opals. The reflectivity spectra also show increase in reflectivity below 0.6 eV; which we interpret as a significantly lower effective plasma frequency of the metallic mesh in the infiltrated opal compare to the plasma frequency in the pure metal

  20. Single and double ionization of gallium by electron impact

    Indian Academy of Sciences (India)

    Electron impact single and double ionization cross sections of gallium have been calcu- ... The experimental data on single ionization have been compared with the empirical and ..... and multiplication sign curve (¢¢¢) represent present.

  1. Multiple scaling power in liquid gallium under pressure conditions

    Energy Technology Data Exchange (ETDEWEB)

    Li, Renfeng; Wang, Luhong; Li, Liangliang; Yu, Tony; Zhao, Haiyan; Chapman, Karena W.; Rivers, Mark L.; Chupas, Peter J.; Mao, Ho-kwang; Liu, Haozhe

    2017-06-01

    Generally, a single scaling exponent, Df, can characterize the fractal structures of metallic glasses according to the scaling power law. However, when the scaling power law is applied to liquid gallium upon compression, the results show multiple scaling exponents and the values are beyond 3 within the first four coordination spheres in real space, indicating that the power law fails to describe the fractal feature in liquid gallium. The increase in the first coordination number with pressure leads to the fact that first coordination spheres at different pressures are not similar to each other in a geometrical sense. This multiple scaling power behavior is confined within a correlation length of ξ ≈ 14–15 Å at applied pressure according to decay of G(r) in liquid gallium. Beyond this length the liquid gallium system could roughly be viewed as homogeneous, as indicated by the scaling exponent, Ds, which is close to 3 beyond the first four coordination spheres.

  2. 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

  3. Gallium accumulation in early pulmonary Pneumocystis carinii infection

    International Nuclear Information System (INIS)

    Stevens, D.A.; Allegra, J.C.

    1986-01-01

    The accumulation of gallium 67 citrate in pulmonary Pneumocystis carinii is well known. The sensitivity of gallium uptake in detecting early inflammatory processes, even when conventional roentgenograms are normal, would seem to make it possible in immunocompromised patients to make a presumptive diagnosis of this serious infection early in its course without using invasive techniques to demonstrate the organism. However, the presence of gallium uptake in radiation pneumonitis, pulmonary drug toxicity, and other processes that also occur in this group limit its usefulness. In our two patients--a young woman with Hodgkin's disease and an elderly woman with small cell lung cancer--this technique proved helpful. Although the latter patient was successfully treated empirically, such empiric treatment should be reserved for patients unable or unwilling to undergo invasive tests. Pulmonary gallium uptake in patients with respiratory symptoms, even with a normal chest film, should prompt attempts to directly demonstrate the organism

  4. Gallium 67 scintigraphic examination of dilated myocardiopathies

    International Nuclear Information System (INIS)

    Lanfranchi, J.; Sachs, R.N.; Beaudet, B.; Deblock, C.; Tellier, P.

    1989-01-01

    Twenty-seven patients were diagnosed as having dilated cardiomyopathies, based on increases in the cardiothoracic index > 0.50, in the diastolic and systolic diameters of the left ventricle, and in the telediastolic volume of the left ventricle, which was indexed by body surface determined by contrast ventriculography. They underwent gallium 67 scintigraphic examination of the myocardium, in order to non-invasively detect the presence of an inflammatory infiltrate. Fifteen of them also had endomyocardial biopsies and all had virology check-up. The results were disappointing. Only in one case was the scintigraphic image undeniably positive; in 20 other patients the findings were dubious or negative. This technique did not demonstrate the presence of an inflammatory infiltrate and thus an association between myocarditis and dilated cardiomyopathy, could not be established [fr

  5. 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

  6. Methods for synthesizing metal oxide nanowires

    Science.gov (United States)

    Sunkara, Mahendra Kumar; Kumar, Vivekanand; Kim, Jeong H.; Clark, Ezra Lee

    2016-08-09

    A method of synthesizing a metal oxide nanowire includes the steps of: combining an amount of a transition metal or a transition metal oxide with an amount of an alkali metal compound to produce a mixture; activating a plasma discharge reactor to create a plasma discharge; exposing the mixture to the plasma discharge for a first predetermined time period such that transition metal oxide nanowires are formed; contacting the transition metal oxide nanowires with an acid solution such that an alkali metal ion is exchanged for a hydrogen ion on each of the transition metal oxide nanowires; and exposing the transition metal oxide nanowires to the plasma discharge for a second predetermined time period to thermally anneal the transition metal oxide nanowires. Transition metal oxide nanowires produced using the synthesis methods described herein are also provided.

  7. Nanowire failure: long = brittle and short = ductile.

    Science.gov (United States)

    Wu, Zhaoxuan; Zhang, Yong-Wei; Jhon, Mark H; Gao, Huajian; Srolovitz, David J

    2012-02-08

    Experimental studies of the tensile behavior of metallic nanowires show a wide range of failure modes, ranging from ductile necking to brittle/localized shear failure-often in the same diameter wires. We performed large-scale molecular dynamics simulations of copper nanowires with a range of nanowire lengths and provide unequivocal evidence for a transition in nanowire failure mode with change in nanowire length. Short nanowires fail via a ductile mode with serrated stress-strain curves, while long wires exhibit extreme shear localization and abrupt failure. We developed a simple model for predicting the critical nanowire length for this failure mode transition and showed that it is in excellent agreement with both the simulation results and the extant experimental data. The present results provide a new paradigm for the design of nanoscale mechanical systems that demarcates graceful and catastrophic failure. © 2012 American Chemical Society

  8. Diameter-dependent coloration of silver nanowires

    International Nuclear Information System (INIS)

    Stewart, Mindy S; Qiu Chao; Jiang Chaoyang; Kattumenu, Ramesh; Singamaneni, Srikanth

    2011-01-01

    Silver nanowires were synthesized with a green method and characterized with microscopic and diffractometric methods. The correlation between the colors of the nanowires deposited on a solid substrate and their diameters was explored. Silver nanowires that appear similar in color in the optical micrographs have very similar diameters as determined by atomic force microscopy. We have summarized the diameter-dependent coloration for these silver nanowires. An optical interference model was applied to explain such correlation. In addition, microreflectance spectra were obtained from individual nanowires and the observed spectra can be explained with the optical interference theory. This work provides a cheap, quick and simple screening method for studying the diameter distribution of silver nanowires, as well as the diameter variations of individual silver nanowires, without complicated sample preparation.

  9. Cathodoluminescence of cubic boron nitride

    International Nuclear Information System (INIS)

    Tkachev, V.D.; Shipilo, V.B.; Zajtsev, A.M.

    1985-01-01

    Three optically active defects are detected in mono- and polycrystal cubic boron nitride (β-BN). Analysis of intensity of temperature dependences, halfwidth and energy shift of 1.76 eV narrow phononless line (center GC-1) makes it possible to interprete the observed cathodoluminescence spectra an optical analog of the Moessbaner effect. Comparison of the obtained results with the known data for diamond monocrystals makes it possible to suggest that the detected center GC-1 is a nitrogen vacancy . The conclusion, concerning the Moessbauer optical spectra application, is made to analyze structural perfection of β-BN crystal lattice

  10. Surface analysis in steel nitrides by using Moessbauer spectroscopy

    International Nuclear Information System (INIS)

    Figueiredo, R.S. de.

    1991-07-01

    The formation of iron nitride layer at low temperatures, 600-700 K, by Moessbauer spectroscopy is studied. These layers were obtained basically through two different processes: ion nitriding and ammonia gas nitriding. A preliminary study about post-discharge nitriding was made using discharge in hollow cathode as well as microwave excitation. The assembly of these chambers is also described. The analysis of the nitrided samples was done by CEMS and CXMS, aided by optical microscopy, and the CEMS and CXMS detectors were constructed by ourselves. We also made a brief study about these detectors, testing as acetone as the mixture 80% He+10% C H 4 as detection gases for the use of CEMS. The surface analysis of the samples showed that in the ammonia gas process nitriding the nitrided layer starts by the superficial formation of an iron nitride rich nitrogen. By thermal evolution this nitride promotes the diffusion of nitrogen and the formation of other more stable nitrides. (author)

  11. 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

  12. Tunneling magnetoresistance in Si nanowires

    KAUST Repository

    Montes Muñoz, Enrique

    2016-11-09

    We investigate the tunneling magnetoresistance of small diameter semiconducting Si nanowires attached to ferromagnetic Fe electrodes, using first principles density functional theory combined with the non-equilibrium Green\\'s functions method for quantum transport. Silicon nanowires represent an interesting platform for spin devices. They are compatible with mature silicon technology and their intrinsic electronic properties can be controlled by modifying the diameter and length. Here we systematically study the spin transport properties for neutral nanowires and both n and p doping conditions. We find a substantial low bias magnetoresistance for the neutral case, which halves for an applied voltage of about 0.35 V and persists up to 1 V. Doping in general decreases the magnetoresistance, as soon as the conductance is no longer dominated by tunneling.

  13. Inhalation developmental toxicology studies: Gallium arsenide in mice and rats

    Energy Technology Data Exchange (ETDEWEB)

    Mast, T.J.; Greenspan, B.J.; Dill, J.A.; Stoney, K.H.; Evanoff, J.J.; Rommereim, R.L.

    1990-12-01

    Gallium arsenide is a crystalline compound used extensively in the semiconductor industry. Workers preparing solar cells and gallium arsenide ingots and wafers are potentially at risk from the inhalation of gallium arsenide dust. The potential for gallium arsenide to cause developmental toxicity was assessed in Sprague- Dawley rats and CD-1 (Swiss) mice exposed to 0, 10, 37, or 75 mg/m{sup 3} gallium arsenide, 6 h/day, 7 days/week. Each of the four treatment groups consisted of 10 virgin females (for comparison), and {approx}30 positively mated rats or {approx}24 positively mated mice. Mice were exposed on 4--17 days of gestation (dg), and rats on 4--19 dg. The day of plug or sperm detection was designated as 0 dg. Body weights were obtained throughout the study period, and uterine and fetal body weights were obtained at sacrifice (rats, 20 dg; mice, 18 dg). Implants were enumerated and their status recorded. Live fetuses were sexed and examined for gross, visceral, skeletal, and soft-tissue craniofacial defects. Gallium and arsenic concentrations were determined in the maternal blood and uterine contents of the rats (3/group) at 7, 14, and 20 dg. 37 refs., 11 figs., 30 tabs.

  14. Semiconductor nanowires and templates for electronic applications

    Energy Technology Data Exchange (ETDEWEB)

    Ying, Xiang

    2009-07-15

    This thesis starts by developing a platform for the organized growth of nanowires directly on a planar substrate. For this, a method to fabricate horizontal porous alumina membranes is studied. The second part of the thesis focuses on the study of nanowires. It starts by the understanding of the growth mechanisms of germanium nanowires and follows by the structural and electrical properties at the single nanowire level. Horizontally aligned porous anodic alumina (PAA) was used as a template for the nanowire synthesis. Three PAA arrangements were studied: - high density membranes - micron-sized fingers - multi-contacts Membranes formed by a high density of nanopores were obtained by anodizing aluminum thin films. Metallic and semiconducting nanowires were synthesized into the PAA structures via DC deposition, pulsed electro-depostion and CVD growth. The presence of gold, copper, indium, nickel, tellurium, and silicon nanowires inside PAA templates was verified by SEM and EDX analysis. Further, room-temperature transport measurements showed that the pores are completely filled till the bottom of the pores. In this dissertation, single crystalline and core-shell germanium nanowires are synthesized using indium and bismuth as catalyst in a chemical vapor deposition procedure with germane (GeH{sub 4}) as growth precursor. A systematic growth study has been performed to obtain high aspect-ratio germanium nanowires. The influence of the growth conditions on the final morphology and the crystalline structure has been determined via scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). In the case of indium catalyzed germanium nanowires, two different structures were identified: single crystalline and crystalline core-amorphous shell. The preferential growth axis of both kinds of nanowires is along the [110] direction. The occurrence of the two morphologies was found to only depend on the nanowire dimension. In the case of bismuth

  15. Recovery of gallium from coal fly ash by a dual reactive extraction process

    Energy Technology Data Exchange (ETDEWEB)

    Gutierrez, B.; Pazos, C.; Coca, J. [University of Oviedo, Oviedo (Spain). Dept. of Chemical Engineering and Environmental Technology

    1997-08-01

    This paper describes the extraction of gallium from coal fly ash by leaching and extraction with commercial extractants Amerlite LA-2 and LIX-54N dissolved in kerosene. Leaching of gallium and other metals from the fly ash was carried out with 6 M hydrochloric acid. The leaching liquor is first contacted with Amerlite LA-2 which extracts the gallium and iron. The iron is then precipitated with sodium hydroxide, while gallium remains in solution. Gallium is extracted selectively from the base solution with LIX 54; the resulting stripped solution contains 83% of the gallium present in the leaching liquor.

  16. Microstructural Characterization of Low Temperature Gas Nitrided Martensitic Stainless Steel

    DEFF Research Database (Denmark)

    Fernandes, Frederico Augusto Pires; Christiansen, Thomas Lundin; Somers, Marcel A. J.

    2015-01-01

    The present work presents microstructural investigations of the surface zone of low temperature gas nitrided precipitation hardening martensitic stainless steel AISI 630. Grazing incidence X-ray diffraction was applied to investigate the present phases after successive removal of very thin sections...... of the sample surface. The development of epsilon nitride, expanded austenite and expanded martensite resulted from the low temperature nitriding treatments. The microstructural features, hardness and phase composition are discussed with emphasis on the influence of nitriding duration and nitriding potential....

  17. Process for the production of metal nitride sintered bodies and resultant silicon nitride and aluminum nitride sintered bodies

    Science.gov (United States)

    Yajima, S.; Omori, M.; Hayashi, J.; Kayano, H.; Hamano, M.

    1983-01-01

    A process for the manufacture of metal nitride sintered bodies, in particular, a process in which a mixture of metal nitrite powders is shaped and heated together with a binding agent is described. Of the metal nitrides Si3N4 and AIN were used especially frequently because of their excellent properties at high temperatures. The goal is to produce a process for metal nitride sintered bodies with high strength, high corrosion resistance, thermal shock resistance, thermal shock resistance, and avoidance of previously known faults.

  18. Predicting the growth of S i3N4 nanowires by phase-equilibrium-dominated vapor-liquid-solid mechanism

    Science.gov (United States)

    Zhang, Yongliang; Cai, Jing; Yang, Lijun; Wu, Qiang; Wang, Xizhang; Hu, Zheng

    2017-09-01

    Nanomaterial synthesis is experiencing a profound evolution from empirical science ("cook-and-look") to prediction and design, which depends on the deep insight into the growth mechanism. Herein, we report a generalized prediction of the growth of S i3N4 nanowires by nitriding F e28S i72 alloy particles across different phase regions based on our finding of the phase-equilibrium-dominated vapor-liquid-solid (PED-VLS) mechanism. All the predictions about the growth of S i3N4 nanowires, and the associated evolutions of lattice parameters and geometries of the coexisting Fe -Si alloy phases, are experimentally confirmed quantitatively. This progress corroborates the general validity of the PED-VLS mechanism, which could be applied to the design and controllable synthesis of various one-dimensional nanomaterials.

  19. Large-area NbN superconducting nanowire avalanche photon detectors with saturated detection efficiency

    Science.gov (United States)

    Murphy, Ryan P.; Grein, Matthew E.; Gudmundsen, Theodore J.; McCaughan, Adam; Najafi, Faraz; Berggren, Karl K.; Marsili, Francesco; Dauler, Eric A.

    2015-05-01

    Superconducting circuits comprising SNSPDs placed in parallel—superconducting nanowire avalanche photodetectors, or SNAPs—have previously been demonstrated to improve the output signal-to-noise ratio (SNR) by increasing the critical current. In this work, we employ a 2-SNAP superconducting circuit with narrow (40 nm) niobium nitride (NbN) nanowires to improve the system detection efficiency to near-IR photons while maintaining high SNR. Additionally, while previous 2-SNAP demonstrations have added external choke inductance to stabilize the avalanching photocurrent, we show that the external inductance can be entirely folded into the active area by cascading 2-SNAP devices in series to produce a greatly increased active area. We fabricated series-2-SNAP (s2-SNAP) circuits with a nanowire length of 20 μm with cascades of 2-SNAPs providing the choke inductance necessary for SNAP operation. We observed that (1) the detection efficiency saturated at high bias currents, and (2) the 40 nm 2-SNAP circuit critical current was approximately twice that for a 40 nm non-SNAP configuration.

  20. New Routes to Lanthanide and Actinide Nitrides

    Energy Technology Data Exchange (ETDEWEB)

    Butt, D.P.; Jaques, B.J.; Osterberg, D.D. [Boise State University, 1910 University Dr., Boise, Idaho 83725-2075 (United States); Marx, B.M. [Concurrent Technologies Corporation, Johnstown, PA (United States); Callahan, P.G. [Carnegie Mellon University, Pittsburgh, PA (United States); Hamdy, A.S. [Central Metallurgical R and D Institute, Helwan, Cairo (Egypt)

    2009-06-15

    The future of nuclear energy in the U.S. and its expansion worldwide depends greatly on our ability to reduce the levels of high level waste to minimal levels, while maintaining proliferation resistance. Implicit in the so-called advanced fuel cycle is the need for higher levels of fuel burn-up and consequential use of complex nuclear fuels comprised of fissile materials such as Pu, Am, Np, and Cm. Advanced nitride fuels comprised ternary and quaternary mixtures of uranium and these actinides have been considered for applications in advanced power plants, but there remain many processing challenges as well as necessary qualification testing. In this presentation, the advantages and disadvantages of nitride fuels are discussed. Methods of synthesizing the raw materials and sintering of fuels are described including a discussion of novel, low cost routes to nitrides that have the potential for reducing the cost and footprint of a fuel processing plant. Phase pure nitrides were synthesized via four primary methods; reactive milling metal flakes in nitrogen at room temperature, directly nitriding metal flakes in a pure nitrogen atmosphere, hydriding metal flakes prior to nitridation, and carbo-thermically reducing the metal oxide and carbon mixture prior to nitridation. In the present study, the sintering of UN, DyN, and their solid solutions (U{sub x}, Dy{sub 1-x}) (x = 1 to 0.7) were also studied. (authors)

  1. Flexible InGaN nanowire membranes for enhanced solar water splitting

    KAUST Repository

    Elafandy, Rami T.

    2018-05-30

    III-Nitride nanowires (NWs) have recently emerged as potential photoelectrodes for efficient solar hydrogen generation. While InGaN NWs epitaxy over silicon is required for high crystalline quality and economic production, it leads to the formation of the notorious silicon nitride insulating interface as well as low electrical conductivity which both impede excess charge carrier dynamics and overall device performance. We tackle this issue by developing, for the first time, a substrate-free InGaN NWs membrane photoanodes, through liftoff and transfer techniques, where excess charge carriers are efficiently extracted from the InGaN NWs through a proper ohmic contact formed with a high electrical conductivity metal stack membrane. As a result, compared to conventional InGaN NWs on silicon, the fabricated free-standing flexible membranes showed a 10-fold increase in the generated photocurrent as well as a 0.8 V cathodic shift in the onset potential. Through electrochemical impedance spectroscopy, accompanied with TEM-based analysis, we further demonstrated the detailed enhancement within excess charge carrier dynamics of the photoanode membranes. This novel configuration in photoelectrodes demonstrates a novel pathway for enhancing the performance of III-nitrides photoelectrodes to accelerate their commercialization for solar water splitting.

  2. 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.

  3. Preparation of aluminum nitride-silicon carbide nanocomposite powder by the nitridation of aluminum silicon carbide

    NARCIS (Netherlands)

    Itatani, K.; Tsukamoto, R.; Delsing, A.C.A.; Hintzen, H.T.J.M.; Okada, I.

    2002-01-01

    Aluminum nitride (AlN)-silicon carbide (SiC) nanocomposite powders were prepared by the nitridation of aluminum-silicon carbide (Al4SiC4) with the specific surface area of 15.5 m2·g-1. The powders nitrided at and above 1400°C for 3 h contained the 2H-phases which consisted of AlN-rich and SiC-rich

  4. Hilar accumulation of gallium-67 in patients with normal chest radiographs

    International Nuclear Information System (INIS)

    Hoshi, Hiroaki; Yamada, Hiroki; Kawahira, Kozaburo; Watanabe, Katsushi

    1982-01-01

    Gallium-67 scintigraphy is a useful screening test to detect malignant or inflammatory lesions. However, the accumulations of Gallium-67 in the normal pulmonary hilum are found in some cases. So, 277 cases with Gallium-67 scintigraphy were discussed. The hilar accumulation of Gallium-67 was classified into four grades, namely Grade 0: no Gallium-67 uptake, Grade I: low Gallium-67 uptake, Grade II: moderate Gallium-67 uptake, and Grade III: high Gallium-67 uptake. Gallium-67 uptake was found in 38 of 277 cases (14%). Thirty cases of these were estimated as Grade I (79%). Cases with Grade II were 20.3%, and only two cases were Grade III (0.7%). Gallium-67 accumulation, was bilateral in 28 cases out of 38 and cases with Gallium-67 accumulation increased with age. Twenty five of the 38 cases with Gallium-67 accumulation had such findings as suggesting old pulmonary inflammation though they had no symptoms of respiratory diseases. This study suggests that hilar Gallium-67 accumulation has no correlation with the active inflammation of the lymphnodes. (author)

  5. Residual Stress Induced by Nitriding and Nitrocarburizing

    DEFF Research Database (Denmark)

    Somers, Marcel A.J.

    2005-01-01

    The present chapter is devoted to the various mechanisms involved in the buildup and relief of residual stress in nitrided and nitrocarburized cases. The work presented is an overview of model studies on iron and iron-based alloys. Subdivision is made between the compound (or white) layer......, developing at the surfce and consisting of iron-based (carbo)nitrides, and the diffusion zone underneath, consisting of iron and alloying element nitrides dispersed in af ferritic matrix. Microstructural features are related directly to the origins of stress buildup and stres relief....

  6. Quantum optics with nanowires (Conference Presentation)

    Science.gov (United States)

    Zwiller, Val

    2017-02-01

    Nanowires offer new opportunities for nanoscale quantum optics; the quantum dot geometry in semiconducting nanowires as well as the material composition and environment can be engineered with unprecedented freedom to improve the light extraction efficiency. Quantum dots in nanowires are shown to be efficient single photon sources, in addition because of the very small fine structure splitting, we demonstrate the generation of entangled pairs of photons from a nanowire. By doping a nanowire and making ohmic contacts on both sides, a nanowire light emitting diode can be obtained with a single quantum dot as the active region. Under forward bias, this will act as an electrically pumped source of single photons. Under reverse bias, an avalanche effect can multiply photocurrent and enables the detection of single photons. Another type of nanowire under study in our group is superconducting nanowires for single photon detection, reaching efficiencies, time resolution and dark counts beyond currently available detectors. We will discuss our first attempts at combining semiconducting nanowire based single photon emitters and superconducting nanowire single photon detectors on a chip to realize integrated quantum circuits.

  7. Broadband enhancement of single photon emission and polarization dependent coupling in silicon nitride waveguides.

    Science.gov (United States)

    Bisschop, Suzanne; Guille, Antoine; Van Thourhout, Dries; Hens, Zeger; Brainis, Edouard

    2015-06-01

    Single-photon (SP) sources are important for a number of optical quantum information processing applications. We study the possibility to integrate triggered solid-state SP emitters directly on a photonic chip. A major challenge consists in efficiently extracting their emission into a single guided mode. Using 3D finite-difference time-domain simulations, we investigate the SP emission from dipole-like nanometer-sized inclusions embedded into different silicon nitride (SiNx) photonic nanowire waveguide designs. We elucidate the effect of the geometry on the emission lifetime and the polarization of the emitted SP. The results show that highly efficient and polarized SP sources can be realized using suspended SiNx slot-waveguides. Combining this with the well-established CMOS-compatible processing technology, fully integrated and complex optical circuits for quantum optics experiments can be developed.

  8. Growth and characterization of InGaAs based nanowire-heterostructures

    International Nuclear Information System (INIS)

    Treu, Julian Pascal

    2017-01-01

    In this thesis we investigate III-V semiconductor nanowires integrated on silicon. Focusing on InGaAs-based heterostructures, we use molecular beam epitaxy (MBE) to obtain high purity material without the use of foreign metal catalysts such as gold. Instead of catalystassisted growth we use selective-area growth using prepatterned SiO 2 /Si(111) substrates prepared by improved nanoimprint lithography, resulting in highly periodic large scale arrays (1 x 1 cm 2 ) of vertically aligned nanowires with hexagonal cross-section. Studying the influence of the main growth parameter substrate temperature, arsenic- and III-material flux we systematically optimize yield and aspect ratio of InAs nanowires for different spacings. Capitalizing on the superior morphological homogeneity of arrays with more than 90% yield, we study their use as efficient surface emitters in the Terahertz regime and find excellent performance, clearly outperforming state-of the art bulk material, when taking the surface coverage into account. Furthermore, we explore nanowires with strongly reduced diameter, where adapted growth conditions result in dimensions as small as 20 nm, well within a quantum confined regime. Starting from optimized high-temperature InAs growth, we further investigate incorporation of gallium for composition tuned ternary InGaAs structures. Delineating the optimized growth parameter space we are able to address nearly the entire compositional range up to more than 80% Ga. Correlating X-ray diffraction, transmission electron microscopy (TEM) and micro-photoluminescence spectroscopy, we find a characteristic transition in crystal structure from wurtzite to zincblende dominated phase for intermediate Ga-content, a regime with luminescence mainly limited by compositional inhomogeneities, while structural defects prevail according linewidths of In- and Ga-rich samples. Furthermore, this successfully demonstrates position-controlled integration of InGaAs nanowires with composition

  9. Role of Gallium and labeled leukocyte scintigraphy in AIDS patient

    International Nuclear Information System (INIS)

    Palestro, C.J.; Goldsmith, S.J.

    1995-01-01

    Because AIDS patients frequently present with minimal symptomatology, radionuclide imaging with its ability to survey the entire body, is especially valuable. Gallium-67 citrate, the most commonly performed radionuclide study for localizing infection in these patients, is most useful for detecting opportunistic infections, especially in the thorax. A negative gallium scan, particularly when the chest X-ray is unremarkable, rules strongly against pulmonary disease. A negative gallium scan in a patient with an abnormal chest X-ray and Kaposi's sarcoma, suggests that the patient's respiratory distress is related to the neoplasm. Diffuse pulmonary parenchymal uptake of gallium in the HIV (+) patient is most often associated with PCP. While there are other causes of diffuse pulmonary uptake, the more intense or heterogeneous the uptake, the more likely the patient is to have PCP. Focal pulmonary uptake is usually associated with bacterial pneumonia although PCP may occasionally present in this fashion. Lymph node uptake of gallium is usually associated with Mycob acterium avium complex, tuberculosis, or Iymphoma. When corresponding abnormalities are present on thallium scintigraphy lymphoma is likely. Gallium positive, thallium negative, studies suggest mycobacterial disease. Labeled leukocyte imaging is not useful for detecting opportunistic infections probably because of the inflammatory response incited by these organisms. Leukocyte imaging is, however, more sensitive for detecting bacterial pneumonia. In the abdomen, gallium imaging is most useful for identifying lymphadenopathy, while labeled leukocyte imaging is superior for detecting AlDS-associated colitides. In summary, radionuclide studies are valuable diagnostic modalities in AIDS. Their success can be maximized by tailoring the study to the individual's needs

  10. Photonic nanowires for quantum optics

    DEFF Research Database (Denmark)

    Munsch, M.; Claudon, J.; Bleuse, J.

    Photonic nanowires (PWs) are simple dielectric structures for which a very efficient and broadband spontaneous emission (SE) control has been predicted [1]. Recently, a single photon source featuring a record high efficiency was demonstrated using this geometry [2]. Using time-resolved micro-phot...

  11. Tunneling and Transport in Nanowires

    International Nuclear Information System (INIS)

    Goldman, Allen M.

    2016-01-01

    The goal of this program was to study new physical phenomena that might be relevant to the performance of conductive devices and circuits of the smallest realizable feature sizes possible using physical rather than biological techniques. Although the initial scientific work supported involved the use of scanning tunneling microscopy and spectroscopy to ascertain the statistics of the energy level distribution of randomly sized and randomly shaped quantum dots, or nano-crystals, the main focus was on the investigation of selected properties, including superconductivity, of conducting and superconducting nanowires prepared using electron-beam-lithography. We discovered a magnetic-field-restoration of superconductivity in out-of-equilibrium nanowires driven resistive by current. This phenomenon was explained by the existence of a state in which dissipation coexisted with nonvanishing superconducting order. We also produced ultra-small superconducting loops to study a predicted anomalous fluxoid quantization, but instead, found a magnetic-field-dependent, high-resistance state, rather than superconductivity. Finally, we developed a simple and controllable nanowire in an induced charged layer near the surface of a masked single-crystal insulator, SrTiO_3. The layer was induced using an electric double layer transistor employing an ionic liquid (IL). The transport properties of the induced nanowire resembled those of collective electronic transport through an array of quantum dots.

  12. Tunneling and Transport in Nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Goldman, Allen M. [Univ. of Minnesota, Minneapolis, MN (United States)

    2016-08-16

    The goal of this program was to study new physical phenomena that might be relevant to the performance of conductive devices and circuits of the smallest realizable feature sizes possible using physical rather than biological techniques. Although the initial scientific work supported involved the use of scanning tunneling microscopy and spectroscopy to ascertain the statistics of the energy level distribution of randomly sized and randomly shaped quantum dots, or nano-crystals, the main focus was on the investigation of selected properties, including superconductivity, of conducting and superconducting nanowires prepared using electron-beam-lithography. We discovered a magnetic-field-restoration of superconductivity in out-of-equilibrium nanowires driven resistive by current. This phenomenon was explained by the existence of a state in which dissipation coexisted with nonvanishing superconducting order. We also produced ultra-small superconducting loops to study a predicted anomalous fluxoid quantization, but instead, found a magnetic-field-dependent, high-resistance state, rather than superconductivity. Finally, we developed a simple and controllable nanowire in an induced charged layer near the surface of a masked single-crystal insulator, SrTiO3. The layer was induced using an electric double layer transistor employing an ionic liquid (IL). The transport properties of the induced nanowire resembled those of collective electronic transport through an array of quantum dots.

  13. Biotemplated synthesis of PZT nanowires.

    Science.gov (United States)

    Cung, Kellye; Han, Booyeon J; Nguyen, Thanh D; Mao, Sheng; Yeh, Yao-Wen; Xu, Shiyou; Naik, Rajesh R; Poirier, Gerald; Yao, Nan; Purohit, Prashant K; McAlpine, Michael C

    2013-01-01

    Piezoelectric nanowires are an important class of smart materials for next-generation applications including energy harvesting, robotic actuation, and bioMEMS. Lead zirconate titanate (PZT), in particular, has attracted significant attention, owing to its superior electromechanical conversion performance. Yet, the ability to synthesize crystalline PZT nanowires with well-controlled properties remains a challenge. Applications of common nanosynthesis methods to PZT are hampered by issues such as slow kinetics, lack of suitable catalysts, and harsh reaction conditions. Here we report a versatile biomimetic method, in which biotemplates are used to define PZT nanostructures, allowing for rational control over composition and crystallinity. Specifically, stoichiometric PZT nanowires were synthesized using both polysaccharide (alginate) and bacteriophage templates. The wires possessed measured piezoelectric constants of up to 132 pm/V after poling, among the highest reported for PZT nanomaterials. Further, integrated devices can generate up to 0.820 μW/cm(2) of power. These results suggest that biotemplated piezoelectric nanowires are attractive candidates for stimuli-responsive nanosensors, adaptive nanoactuators, and nanoscale energy harvesters.

  14. Nanowire-based gas sensors

    NARCIS (Netherlands)

    Chen, X.; Wong, C.K.Y.; Yuan, C.A.; Zhang, G.

    2013-01-01

    Gas sensors fabricated with nanowires as the detecting elements are powerful due to their many improved characteristics such as high surface-to-volume ratios, ultrasensitivity, higher selectivity, low power consumption, and fast response. This paper gives an overview on the recent process of the

  15. Surface modification of titanium by plasma nitriding

    Directory of Open Access Journals (Sweden)

    Kapczinski Myriam Pereira

    2003-01-01

    Full Text Available A systematic investigation was undertaken on commercially pure titanium submitted to plasma nitriding. Thirteen different sets of operational parameters (nitriding time, sample temperature and plasma atmosphere were used. Surface analyses were performed using X-ray diffraction, nuclear reaction and scanning electron microscopy. Wear tests were done with stainless steel Gracey scaler, sonic apparatus and pin-on-disc machine. The obtained results indicate that the tribological performance can be improved for samples treated with the following conditions: nitriding time of 3 h; plasma atmosphere consisting of 80%N2+20%H2 or 20%N2+80%H2; sample temperature during nitriding of 600 or 800 degreesC.

  16. Thermodynamics, kinetics and process control of nitriding

    DEFF Research Database (Denmark)

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

    1999-01-01

    As a prerequisite for 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 pure iron-nitrogen phases has not been achieved fully. It has been shown that taking into account ordering of nitrogen in the epsilon and gamma' iron-nitride phases, leads to an improved understanding of the Fe-N phase diagram. Although thermodynamics indicate the state the system strives for......, the nitriding result is determined largely by the kinetics of the process. The nitriding kinetics have been shown to be characterised by the occurring local near-equilibria and stationary states at surfaces and interfaces, and the diffusion coefficient of nitrogen in the various phases, for which new data have...

  17. Magnetostatic Interaction in Fe-Co Nanowires

    Directory of Open Access Journals (Sweden)

    Laura Elbaile

    2012-01-01

    Full Text Available Arrays of Fe-Co alloy nanowires with diameter around 35 nm and several micrometers in length have been synthesized by codepositing Fe and Co into porous anodic alumina. The morphology, structure, and magnetic properties of the nanowires (hysteresis loops and remanence curves were characterized by SEM, TEM, X-ray diffraction (XRD, and VSM, respectively. The XRD patterns indicate that the Fe-Co nanowires present a body-centered cubic (bcc structure and a preferred (110 orientation perpendicular to the template surface. From the hysteresis loops obtained with the magnetic field applied in the axis direction of the nanowires, we can observe that the coercive field slightly decreases when the nanowire length increases. This magnetic behaviour is analyzed considering the shape anisotropy and the dipolar interactions among nanowires.

  18. Gallium a unique anti-resorptive agent in bone: Preclinical studies on its mechanisms of action

    International Nuclear Information System (INIS)

    Bockman, R.; Adelman, R.; Donnelly, R.; Brody, L.; Warrell, R.; Jones, K.W.

    1990-01-01

    The discovery of gallium as a new and unique agent for the treatment of metabolic bone disorders was in part fortuitous. Gallium is an exciting new therapeutic agent for the treatment of pathologic states characterized by accelerated bone resorption. Compared to other therapeutic metal compounds containing platinum or germanium, gallium affects its antiresorptive action without any evidence of a cytotoxic effect on bone cells. Gallium is unique amongst all therapeutically available antiresorptive agents in that it favors bone formation. 18 refs., 1 fig

  19. 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

  20. Cathodoluminescence of cubic boron nitride

    International Nuclear Information System (INIS)

    Tkachev, V.D.; Shipilo, V.B.; Zaitsev, A.M.

    1985-01-01

    Three types of optically active defect were observed in single-crystal and polycrystalline cubic boron nitride (β-BN). An analysis of the temperature dependences of the intensity, half-width, and energy shift of a narrow zero-phonon line at 1.76 eV (GC-1 center) made it possible to interpret the observed cathodoluminescence spectra as an optical analog of the Moessbauer effect. A comparison of the results obtained in the present study with the available data on diamond single crystals made it possible to identify the observed GC-1 center as a nitrogen vacancy. It was concluded that optical Moessbauer-type spectra can be used to analyze structure defects in the crystal lattice of β-BN