bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of Emission Rate Measurements in a Material Showing a Meyer-Neldel- Rule
Authors: Crandall Richard S. 
Published: April 2011

ABSTRACTThis paper presents data showing a Meyer-Neldel rule (MNR) in InGaAsN alloys. It is shown that without this knowledge, significant errors can be made using Deep-Level Transient-Spectroscopy (DLTS) emission data to determine capture cross sections. The errors arise because of the neglect of significant transition entropy changes associated with multiphonon excitation of charge from deep traps. Ignoring the entropy change results in cross section values ranging over five orders-of-magnitude in InGaAsN alloys and 18 orders-of-magnitude in CuInGaSe alloys. Only by correctly accounting for the MNR and the accompanying entropy changes in analyzing the DLTS data will the correct value of the cross section be obtained.
HVPE-based orientation-patterned GaAs: added-value for non-linear applications.
Authors: D. Faye , E. Lallier , A. Grisard , B. Gérard , E. Gil-Lafon 
Published: April 2011

ABSTRACTA new route is presented for the development of Orientation-Patterned Gallium Arsenide (OP-GaAs) for both guided and non-guided optical applications. The method is based on the use of the near-equilibrium growth process HVPE (Hydride Vapour Phase Epitaxy) that enables thick, high quality and orientation-preserving regrowth over dimensions fully compatible with targeted applications. The control of the growth anisotropy permits to preserve the original periodic arrangement of the initial template so that OP-GaAs substrates can be fabricated with pattern width and structure thickness ranging respectively from 1.8 to 110μm and 20 to 500μm. Such a large scope of dimensions appears useful either for bulk structures such as Optical Parametric Oscillators (OPO) or telecommunication applications. As an example, we suggest that combining this growth method with mechano-chemical polishing process could decrease propagation losses on AlGaAs waveguide structures for frequency conversion in telecom bands.
Estimates of Impact Ionization Coefficients in Superlattice-Based Mid-Wavelength Infrared Avalanche Photodiodes
Authors: Grein C. H. , Abu El-Rub K. , Flatté M. E. , Ehrenreich H. 
Published: April 2011

ABSTRACTWe describe band engineering strategies to either enhance or suppress electron-initiated impact ionization relative to hole-initiated impact ionization in type II superlattice mid-wavelength infrared avalanche photodiodes. The strategy to enhance electron-initiated impact ionization involves placing a high density of states at approximately one energy gap above the bottom of the conduction band and simultaneously removing valence band states from the vicinity of one energy gap below the top of the valence band. This gives the electrons a low threshold energy and the holes a high one. The opposite strategy enhances hole-initiated impact ionization. Estimates of the electron (α) and hole (β) impact ionization coefficients predict that α/β>>1 in the first type of superlattice and α/β<<1 in the second type.
A New Class of Solar Cells: Isomeric Boron Carbide Semiconductors with Fourth Quadrant Conductivity
Authors: Billa Ravi B. , Caruso A. N. , Brand J. I. 
Published: April 2011

ABSTRACTPreviously, we have made diodes[1,2] and transistors [3] as well as very effective realtime solid state neutron detectors [4] out of semiconducting boron carbide deposited on silicon or silicon carbide‥In this work the recent fabrication of a new class of highly photosensitive boron carbide diodes is discussed. These diodes exploit the electronic behavior differences of the isomers of film precursors, the closo-dicarbododecaboranes. These differences were observed in photoemission and inverse photoemission studies where the HOMO-LUMO (highest occupied molecular orbital-lowest unoccupied molecular orbital) gap variations upon deposition varied strongly with the isomeric configuration. Based on these results, p-n junctions were formed by plasma enhanced chemical vapor of ortho and meta carborane, respectively, on both nickel and aluminum substrates. These diodes exhibit fourth-quadrant conductivity, making them exciting new photovoltaic conversion devices.
Non-Contact Determination of Free Carrier Concentration in n-GaInAsSb
Authors: Maslar James E. , Hurst Wilbur S. , Wang Christine A. , Shiau Daniel A. 
Published: April 2011

ABSTRACTGaSb-based semiconductors are of interest for mid-infrared optoelectronic and high-speed electronic devices. Accurate determination of electrical properties is essential for optimizing the performance of these devices. However, electrical characterization of these semiconductors is not straightforward since semi-insulating (SI) GaSb substrates for Hall measurements are not available. In this work, the capability of Raman spectroscopy for determination of the majority carrier concentration in n-GaInAsSb epilayers was investigated. Raman spectroscopy offers the advantage of being non-contact and spatially resolved. Furthermore, the type of substrate used for the epilayer does not affect the measurement. However, for antimonide-based materials, traditionally employed Raman laser sources and detectors are not optimized for the analysis wavelength range dictated by the narrow band gap of these materials. Therefore, a near-infrared Raman spectroscopic system, optimized for antimonide-based materials, was developed.Ga0.85In0.15As0.13Sb0.87 epilayers were grown by organometallic vapor phase epitaxy with doping levels in the range 2 to 80 × 1017 cm-3, as measured by secondary ion mass spectrometry. For a particular nominal doping level, epilayers were grown both lattice matched to n-GaSb substrates and lattice-mismatched to SI GaAs substrates under nominally identical conditions. Single magnetic field Hall measurements were performed on the epilayers grown on SI GaAs substrates, while Raman spectroscopy was used to measure the carrier concentration of epilayers grown on GaSb and the corresponding SI GaAs substrates. Contrary to Hall measurements, Raman spectra indicated that the GaInAsSb epilayers grown on GaSb substrates have higher free carrier concentrations than the corresponding epilayers grown on SI GaAs substrates under nominally identical conditions. This is contrary to the assumption that for nominally identical growth conditions, the resulting carrier concentration is independent of substrate, and possible mechanisms will be discussed.
Laser Power and Temperature Dependent Photoluminescence Characteristics of Annealed GaInNAs/GaAs Quantum Well
Authors: Khee Ng Tien , Fatt Yoon Soon , Weijun Fan 
Published: April 2011

ABSTRACTPhotoluminescence (PL) of annealed GaInNAs quantum well (QW) with varying temperature and laser excitation intensity is measured to understand the low temperature PL properties of annealed 6 nm GaInNAs QW. The measurements show that localization effect still exist in the QW even after annealing. This effect is characterized by an activation energy of 11 meV below the e1 state, which is obtained from fitting the integrated PL intensity vs. temperature curve with a single-activation-energy (SAE) model. This center is suggested to be related to the main localization center below the e1 state that could be resulted by N or In compositional fluctuation even after annealing.
Crystal Growth and Electrical Characterization of InSbN Grown by Metalorganic Vapor Phase Epitaxy
Authors: Ishiguro T. , Kobori Y. , Nagawa Y. , Iwamura Y. , Yamaguchi S. 
Published: April 2011

ABSTRACTInSb1-xNx was grown on GaAs substrate by low-pressure metalorganic vapor phase epitaxy. Carrier gases were hydrogen or the mix of hydrogen and nitrogen. In both cases, X-ray analysis demonstrated that nitrogen was incorporated into InSb1-xNx up to 0.24.
Electrical Properties of β -FeSi2/Si Hetero-Diode Improved by Pulsed Laser Annealing
Authors: Tsuchiya Keiichi , Miura Noboru , Matsumoto Hironaga , Nakano Ryotaro , Uekusa Shin-ichiro 
Published: April 2011

ABSTRACTβ-phase iron disilicide (β-FeSi2) was obtained on n-type silicon (111) substrate by using excimer laser annealing (ELA). β-phase crystal which have good electrical properties was grown within a narrow annealing condition such as energy density. All samples were annealed by excimer laser show n-type characteristic. Graded junction was formed in FeSi2/Si hetero diode.
Infrared Dielectric Properties of In1-xGaxAs Epilayers on InP (100)
Authors: Rowell N. L. , Yu G. , Lockwood D. J. , Poole P. J. 
Published: April 2011

ABSTRACTThe concentration dependence of optical phonons in strained In1-xGaxAs epilayers grown on InP (100) by chemical beam epitaxy has been characterized with oblique angle polarized far-infrared reflectivity measurements. In this powerful method, the reflectance spectra contain sharp Berreman peaks exactly at the optical phonon frequencies. For radiation polarized in the plane of incidence (p-polarized), peaks for both the TO and LO phonons were observed. For s-polarization only the TO modes were observed. For heavily doped substrates the TO film phonons were observed as reflectance minima, whereas for lightly doped substrates they were seen as maxima. The measured spectra were curve resolved to separate the effects of the various modes which included GaAs-like longitudinal and transverse optic (LO and TO), a disorder induced, and InAs-like LO and TO phonons. The dielectric response function and phonon frequency dependences for all modes were obtained versus Ga fraction for x from 0.25 to 0.75 and the latter showed a quadratic dependence on x over this range. The effects of strain on the phonon frequencies could then be evaluated.
Electronic Structure of Native Point Defects in Zngep2
Authors: Jiang Xiaoshu , Miao M. S. , Lambrecht Walter R. L. 
Published: April 2011

ABSTRACTFirst-principles calculations are presented for various native point defects in ZnGeP2 us-ing a full-potential linearized muffin-tin orbital method in the local density approximation to density functional theory. Under Zn-poor conditions, the lowest Gibbs energy defects are found to be the Gezn antisite and Vzn. The Vae is found to have high energy of formation under any chemical potential conditions and is unstable towards formation of a Vzn and ZnGe pair. It is shown that the V−Zn cannot account for the ALI EPR spectrum commonly associated with this vacancy and an alternative model consisting of a Vzn – GeZn – Vzn is tentatively proposed.
Room-Temperature Defect Tolerance of Shape Engineered Quantum Dot Structures
Authors: Lamberti Matthew , Katsnelson Alex , Yakimov Michael , Agnello Gabriel , Tokranov Vadim , Oktyabrsky Serge 
Published: April 2011

ABSTRACTA quantum dot (QD) medium is expected to demonstrate superior performance in various devices when compared with quantum wells (QWs). One area of interest has been the improved defect tolerance of QD media, though it was demonstrated at low temperatures so far. In this study, the defect tolerance of shape-engineered QD structures is compared with that of a QW structure at temperatures up to 300 K. To create high defect densities both QD and QW structures were irradiated with high energy (1.5 MeV) protons (with doses up to 3×1014 cm-2). Then, the relative luminescence efficiency was measured by variable temperature photoluminescence. The shape-engineered QD structure withstood two orders of magnitude higher defect density than the QWs at room temperature. This improvement is correlated with the activation energy for thermal evaporation of 390 meV, acquired through a kinetic model.
Synthesis of Aligned ZnO Hexagonal Nanorods and Its Application to ZnS Based DC Electroluminescent Devices
Authors: Hirate Takashi , Tanaka Hironori , Sasaki Shinya , Ozawa Makoto , Li Weichi , Satoh Tomomasa 
Published: April 2011

ABSTRACTHighly oriented ZnO nanorods have been grown on p--Si(111) wafers using a low-pressure thermal CVD method. X-ray diffraction shows that the nanorods are grown with the c-axis normal to the substrate. An electroluminescent device with ITO/ZnS:Mn/nanorod-ZnO/p--Si structure where the ZnS:Mn and ITO layers are deposited by the electron beam deposition method on the ZnO nanorods layer operates stably in DC mode with high luminance.
Wide Bandgap Materials for Semiconductor Spintronics
Authors: Pearton S. J. , Abernathy C. R. , Thaler G. T. , Frazier R. , Norton D. P. , Kelly J. , Rairigh R. , Hebard A. F. , Park Y. D. , Zavada J. M. 
Published: April 2011

ABSTRACTExisting semiconductor electronic and photonic devices utilize the charge on electrons and holes in order to perform their specific functionality such as signal processing or light emission. The relatively new field of semiconductor spintronics seeks, in addition, to exploit the spin of charge carriers in new generations of transistors, lasers and integrated magnetic sensors. The ability to control of spin injection, transport and detection leads to the potential for new classes of ultra-low power, high speed memory, logic and photonic devices. The utility of such devices depends on the availability of materials with practical (>300K) magnetic ordering temperatures. In this paper, we summarize recent progress in dilute magnetic semiconductors such as (Ga,Mn)N, (Ga,Mn)P and (Zn,Mn)O exhibiting room temperature ferromagnetism, the origins of the magnetism and its potential applications in novel devices such as spin-polarized light emitters and spin field effect transistors.
The dispersion and polymer coating of ultrafine aluminum powders by the Ziegler Natta reaction
Authors: Roy Cédric , Dubois Charles , Lafleur Pierre , Brousseau Patrick 
Published: April 2011

ABSTRACTUltrafine aluminum powders have been identified as very promising fuels as part of energetic materials formulations. However, the large specific surface area that gives these powders a high reactivity also makes them particularly difficult to maintain in an unoxidized state. They also agglomerate easily during compounding processes. The coating of the particles by a polymer could offer a solution to these problems. We carried out the in-situ synthesis of high density polyethylene on the surface of aluminum nanoparticles by the Ziegler-Natta process. The process was found to be flexible enough to control the amount of polyethylene grafted on the powders. Ultrasounds were applied during the polymerization process to enhance the dispersion of the particles in the solvent. The resulting characteristics of the coated powders are discussed by means of thermogravimetric characterizations and electronic microscopy.
Combustion Synthesis of Nanoscale Oxide Powders: Mechanism, Characterization and Properties
Authors: Varma Arvind , Mukasyan Alexander S. , Deshpande Kishori T. , Pranda Pavol , Erri Peter R. 
Published: April 2011

ABSTRACTBased on the analysis of extensive experimental data, we have formulated basic criteria necessary for the synthesis of a variety of oxides in the combustion mode, and defined optimum conditions for the production of high-surface area, well-crystalline nano-powders of desired phase composition and purity. Also, for the first time, detailed chemical mechanisms of interaction for various systems are identified, outlining specific roles of different fuels, oxidizers and thermal conditions
Nickel Aluminide Superalloys Created by SHS of Nano-Particle Reactants
Authors: Hunt Emily M. , Granier John J. , Plantier Keith B. , Pantoya Michelle L. 
Published: April 2011

ABSTRACTAdvancements in nanotechnology for material processing have spurred the development of superalloys that provide improved protection against corrosion and wear. Nano-scale reactant particles offer unique thermal properties and increased homogeneity that may improve the microstructural features and macroscopic properties of the final product. In this study up to 10-wt% nano-scale molybdenum tri-oxide (MoO3) particles were added to micron scale nickel (Ni) and aluminum (Al). The goal was to produce a superalloy by generating excessively high heating rates and adding an oxidizer that would produce small quantities of Al2O3 (a strengthening agent) within the microstructure of the alloy. Experiments were performed on pellets pressed to 60% theoretical maximum density. Ignition and flame propagation were examined using a CO2 laser and imaging diagnostics that include a copper-vapor laser coupled with a high-speed camera. Product microstructure was examined using scanning electron microscopy. Abrasion testing was performed to evaluate the wear resistance properties of the superalloy. Results show that adding MoO3 increases the flame temperature and produces greater ignition sensitivity. Also, small quantities of MoO3 produce a more homogeneous microstructure and increase the overall wear resistance of the product.
Characterization of Nano-Sized Particles for Propulsion Applications
Authors: Risha Grant A. , Boyer Eric , Evans Brian , Kuo Kenneth K. , Malek Rafaat 
Published: April 2011

ABSTRACTEnergetic nano-sized particles have been shown to have a great potential for use in the aerospace propulsion applications. Some of the unique combustion properties of nano-particles such as very rapid ignition and short combustion times make them particularly valuable for propulsion systems; they can be included in solid fuels, solid propellants, or even as energetic gellant in liquid systems. However, due to the novelty of the application and rapid development of production techniques, there is no comprehensive understanding of what characteristics of a nano-sized particle are important in contributing to desirable performance and ease of processing into a final usable form. Previous studies have shown that HTPB-based solid fuels containing various types of nano-sized particles showed differing performance results when tested in the same hybrid rocket motor under identical conditions. Many of these particles have data available only on the basic composition (aluminum, boron, boron carbide, etc.), average diameter, and/or BET surface area. In order to better understand and correlate observed combustion behavior with intrinsic material properties, the particles of interest need to be better characterized. A variety of standard particle characterization techniques were applied to the fifteen types of particles examined in this study and the results tabulated. Some of the parameters measured were average particle diameter, specific surface area, amount of active content, and oxide layer thickness. Trends in propulsion performance measured using a parameter of great interest to the hybrid rocket community (fuel mass burning rate) in general matched trends in particle characteristics (i.e. active content, surface area), but there were some noticeable exceptions. This study indicates that there is still much more to learn about the correlation between physical and chemical properties and measured combustion performance. Other parameters that should be examined in the future include particle size distribution, degree of agglomeration, reactivity and thermal effects (oxidation rate, onset temperature for oxidation exotherm, heat release associated with any excess stored energy), etc.
Formation of Nanostructured Energetic Materials via Modified Sol-Gel Synthesis
Authors: Walker Jeremy , Tannenbaum Rina 
Published: April 2011

ABSTRACTThis study is concerned with the development of a modified sol-gel synthesis of Fe2O3 xerogels that would allow the design and control of the interfacial area between the oxidant iron oxide matrix and the metal reducing agent, thus optimizing the energetic yield of these highly energetic reactions. The modification consisted in the addition of a new class of di-functional template molecules, such as diamines or di-acids, as gelation agents. pH profile measurements indicated that the mechanism of reaction of propylene oxide and of succinic acid as the gelation agents was fundamentally different. Propylene oxide acts as a proton scavenger, reducing the hydrated iron species to Fe2O3, thus reducing the concentration of protons in the reaction mixture leading to an increase in pH. When succinic acid is used as the gelation agent, a decrease in pH versus time during the reaction indicates the formation of carboxylate ions, thus creating reactive molecules that are capable of stabilizing the Fe2O3 clusters during the growth process. Infrared spectra of the products in both reactions support presence of carboxylate groups in the Fe2O3 xerogels. X-ray diffraction analyses revealed low levels of crystallinity in both products, and the presence of different phases of Fe2O3.
First-Principles Equation of State for an Energetic Intermetallic Mixture
Authors: Lu X. , Hanagud S. 
Published: April 2011

AbstractThe thermodynamically complete equation of state P=P(ρ,T) for a intermetallic mixture of nickel and aluminum is obtained via first principle calculations for pressures up to 300GPa and temperatures up to 1000K. The calculations for the static-lattice EOS are carried out in the framework of the density functional theory (DFT), using generalized gradient approximations and ultrasoft psuedopotentials. The phonon modes are calculated by using the density functional perturbation theory (DFPT). First, the EOS for each species is obtained based on ab initio prediction of the electron ground state and thermal excitations. Then, the mixture theories are utilized to obtain the EOS for the mixture. Two mixture theories are proposed, which correspond to the two limiting cases. The nature of the real mixture is intermediate to those of the two idealized mixtures and hence can be modeled as a weighted combination of the two cases. The Comparisons of the EOS for nickel and aluminum obtained from existing shock Hugoniot data show good agreement with the theoretical results.
Nanoscale Energetics with Carbon Nanotubes
Authors: Wang Yubing , Malhotra Sanjay , Iqbal Zafar 
Published: April 2011

AbstractSingle wall carbon nanotubes (SWNTs) with diameters below 1 nm prepared by chemical vapor deposition (CVD), and with diameters of 1.3 nm and higher prepared by laser ablation and carbon-arc techniques, were electrochemically functionalized with hydrogen and nitro groups, and chemically derivatized with 4-nitroaniline. Hydrogen adsorption on SWNTs was carried out in the presence or absence of electrodeposited catalytic nanoparticles of magnesium. SWNTs deposited on Teflon-coated membranes by vacuum filtration and lifted off as free-standing nanopaper, were used as the electrodes for electrochemical functionalization reactions. Hydrogen uptake on the nanotubes was characterized by micro-Raman spectroscopy, thermogravimetry and thermopower measurements. Electrochemically-induced functionalization with −NO2 groups on metallic, laser-synthesized SWNTs was clearly detected by Raman spectroscopy. Chemical functionalization was achieved on CVD-produced SWNTs by acidification to form −COOH groups followed by reaction with thionyl chloride and then with 4-nitroaniline. Photoacoustic effects that are likely to be precursors of photo-induced initiation of energetic reactions, were observed to occur at varying laser intensities for these materials in experiments using a pulsed Nd-YAG laser emitting at 532 nm.