bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spectroscopic Investigation of Li and P-Doped ZnSe Grown by Molecular Beam Epitaxy
Authors: Zhang Y. , Skromme B. J. , Cheng H. 
Published: March 2011

ABSTRACTA conduction band-to-acceptor (e-A°) peak at 2.7060 eV has been identified for the first time in 1.7 K PL spectra of Li-doped ZnSe/GaAs. Photoluminescence (PL) measurements as a function of temperature and excitation level have been employed to confirm the identification and to study the behavior of this peak. This peak was previously misidentified as the “R”-band characteristic of bulk material, which has been associated with transitions between preferentially paired interstitial Li donors and substitutional Li acceptors on Zn sites. We find no direct evidence of Li interstitials in the PL data. The splitting of the Li acceptor-bound exciton is dramatically reduced by removal of the GaAs substrate, which proves that the splitting is due to strain and not to the hole-hole exchange interaction. A P-doped ZnSe/GaAs sample exhibits a shallow P bound exciton peak nearly superimposed on the donor-bound excitons. It is distinguished by its strong LO phonon replica and low energy undulation wing, which are both unique characteristics of shallow acceptor-bound excitons. Transitions involving the conduction band to split P acceptor light and heavy hole levels have been detected for the first time in P-doped heteroepitaxial ZnSe. Using the temperature dependence of the (e-A°) peak positions, accurate binding energies of 89.1±0.6 and 114.4±0.4 meV have been obtained for shallow P and Li acceptor levels in unstrained ZnSe, respectively
Growth and Optical Characterization of ZnMnTe Grown by Molecular Beam Epitaxy
Authors: Reno John L. , Jones Eric D. , Venturini Eugene L. 
Published: March 2011

ABSTRACTWe have successfully grown ZnMnTe alloys by molecular beam epitaxy using GaAs as a substrate. Bulk MnTe has the wurtzite crystal structure but the structural phase of the material was confirmed to be zinc-blende by standard θ-2θ x-ray diffraction techniques. The composition was also determined using x-ray diffraction techniques. Manganese cancentration was also estimated from magnetization measurements taken as a function of temperature. Magneto-luminescence studies were performed at 1.4K on the acceptor-bound exciton in the semimagnetic semiconductor ZnMnTe alloys. As expected, the photoluminescence peak energy decreased with increasing magnetic field.
Interface Characterization of PbTe/BaSi/Si Heterostructures Grown Using MBE
Authors: Santiago F. , Woody D. , Chu T. K. , Huber C. A. 
Published: March 2011

ABSTRACTA new substrate material consisting of a buffer layer of a Ba-Si compound was developed by making use of the chemical reaction between BaF2 and Si. This substrate is very promising for the integration of IV-VI semiconductor materials with silicon. PbTe films of excellent quality, as determined by X-ray and Reflected High Energy Electron Diffraction spectra, have been deposited over (111)- and (100)-oriented silicon wafers of 3 inch diameter. These PbTe films are (100)-oriented irrespective of the Si orientation. X-ray photoelectron spectroscopy studies reveal very interesting chemistry at the interface between Ba-Si and Te. They suggest that BaTe may form between PbTe and Ba-Si at their interface. This interfacial region, which is of the order of only a few molecular layers, appears to be critical in the success of the deposition. Thermal cycling showed that the PbTe/BaSi/Si system is mechanically very stable. The possibility of a similar growth mechanism for the deposition of II-VI semiconductors such as CdTe is considered.
The Fabrication of NiSi2/Si(100) Interfaces with Controlled Morphologies
Authors: Sullivan J. P. , Tung R. T. , Schrey F. , Graham W. R. 
Published: March 2011

ABSTRACTThe morphology and defect structures associated with thin NiSi2 films prepared on Si(100) were investigated. Facets were found to be a common defect structure at the interface unless stoichiometric co-deposition of Ni and Si was performed. Annealing thin, uniform NiSi2 layers prepared by stoichiometric co-deposition to temperatures ≥ 700°C yielded epitaxial films of high crystalline perfection. Films in which the deposition was off-stoichiometric exhibited a variety of defect structures. In addition to facets at the interface, networks of meandering micro-twins or stacking faults were observed in highly Ni-rich films, while pinholes were observed in Si-rich films. Facets at the interface were found to be eliminated by annealing at temperatures ≥ - 750°C, indicating that the planar NiSi2/Si(100) interface is energetically stable with respect to the formation of NiSi2(111) facets. Through manipulation of the film growth kinetics, NiSi2/Si(100) interfaces with arbitrary facet densities were produced. Partially faceted NiSi2/Si(100) interfaces represent ideal experimental systems for revealing the effects of Schottky barrier inhomogeneity on the electrical measurements of metal/semiconductor contacts.
Electrical Contacts to Metastable GexSi1−x Using Pd2Si as a Transport Layer
Authors: Purser Richard G. , Strane Jay W. , Mayer James W. 
Published: March 2011

ABSTRACTThe transport of germanium through a co-deposited palladium-silicon layer on epitaxially grown GexSi1−x on Si(100) was studied. The Ge concentration in the UHV-CVD grown GexSi1−x film was x=.14 with a thickness of 155 nm. When the co-deposited layer is Pd rich with respect to Pd2Si, Ge was found to move through the Pd-Si layer and grow polycrystalline on the GexSi1−x. Ge transport and Pd2Si(111) grain growth ceased simultaneously. No transport was found for Si rich Pd-Si layers. Electrical characterization showed the contacts were ohmic with a specific contact resistivity between 6–12 μωQ-cm2 and an end resistance of.75 ω, resulting in a carrier concentration under the contact of 1.5×1014 cm−2. Hall effect measurements of the semiconductor gave n=5.77×1014 cm−2 and μ=36.96 cm−2/Vs. The sheet resistance of the contact layer was found to be 23.54 ω/square and the semiconductor was 237 ω/square.
Beem Investigation of Oxide and Sulfide Passivated GaAs
Authors: Alec Talin A. , Stanley Williams R. , Kavanagh Karen L. 
Published: March 2011

ABSTRACTBallistic Electron Emission Microscopy (BEEM) was used to investigate the effects of a sulfide interfacial layer on the electronic properties of the Au/n-GaAs interface. Two diodes were simultaneously prepared in UHV by evaporating Au onto (100)GaAs substrates which were either treated with (NH4)2S or NH4OH etching solutions prior to Au deposition. Auger electron spectroscopy was used in situ to monitor the surface chemical composition. The effective Schottky barrier (SB) height was measured with BEEM at 10 different locations on the surface of each diode. The (NH4)2S treatment increased the average barrier height and reduced the spread in the values, as compared to the contact formed on the NH4OH treated GaAs.
Formation and Electronic Structure of the Mn/GaAs(100) Interface
Authors: Jin X. , Zhang M. , Dong G. S. , Li Z. S. , Wang Xun , Zhu X. G. 
Published: March 2011

ABSTRACTFormation and electronic structure of the Mn/GaAs(100) interface grown at room temperature are studied by photoemission. The growth at early stage is identified to be in two-dimensional mode. The chemical reaction and the interface diffusion happened between Mn and GaAs are explored in some details. A ferromagnetic phase of Mn overlayer at early stage is deduced from the change of electron density of states near the Fermi edge.
Microstructure Analysis of Thermally Stable Ohmic Contact to Both n and p+-GaAs
Authors: Han W. Y. , Lee H. S. , Lu Y. , Cole M. W. , Casas L. M. , DeAnni A. , Jones K. A. , Yang L. W. 
Published: March 2011

ABSTRACTA thermally stable Pd/Ge/Ti/Pt/ ohmic contact with low specific contact resistance was formed on both n and p+-GaAs. The lowest specific contact resistances were 4.7×10−7 and 6.4×10−7 Ω.cm2 for the n and p+-GaAs, respectively, when the n-GaAs was doped with Si to 2×1018cm−3, and the p+-GaAs was doped with carbon to 5×1019 cm−3. Interfacial reactions and element diffusions of the contacts were investigated by using transmission electron microscopy, Auger electron spectrometry with depth profiles. All the contacts were thermally stable at 300 °C for 20 hours, and it appeared that the p-contacts were more stable than the n-contacts.
Growth and Doping of GaN Films by ECR-Assisted MBE
Authors: Moustakas T. D. , Molnar R. J. 
Published: March 2011

ABSTRACTWe report on growth, doping, and characterization studies of GaN films produced by the Electron Cyclotron Resonance microwave plasma assisted Molecular Beam Epitaxy. The films were grown heteroepitaxially on sapphire (0001), whose surface was converted into atomically smooth AIN by plasma nitridation. The GaN films were grown in two temperature steps, a process found to promote the layer-by-layer growth mode. ECR plasma conditions to grow either n-type autodoped or semi-insulating GaN film were identified. The structure and microstructure as well as the electrical properties of these two classes of films are discussed. A systematic dependence between electron mobility and net carrier concentration was found, which predicts that the mobility of GaN with a net carrier concentration of 1014cm−3 is about 104cm2 /V.s. The insulating films were intentionally doped either p-type or n-type by incorporation of Mg or Si during film growth. Hole or electron concentrations at 300K between 1018-1019cm−3 have been obtained without requiring any post-growth treatment.
High Mobility GaN films Produced by ECR-Assisted MBE
Authors: Molnar R. J. , Lei T. , Moustakas T. D. 
Published: March 2011

ABSTRACTHigh electron mobility autodoped GaN films were produced by the ECR assisted MBE method. The net electron concentration was varied systematically from 2×1019 to 2×1017cm−3 by controlling the active nitrogen overpressure. Correspondingly, the electron mobility increased from 20 to 210 cm2V−1sec−1. The line through the experimental data also predicts the electron mobilities of GaN films produced by the CVD methods.
GaN-AlxGa1−xN Heterostructures Deposition by Low Pressure Metalorganic Chemical Vapor Deposition for Metal Insulator Semiconductor Field Effect Transistor (Misfet) Devices
Authors: Asif Khan M. , Kuznia J. N. , Bhattarai A. R. , Olson D. T. 
Published: March 2011

ABSTRACTIn this paper we report the fabrication and characterization of a metal insulator semiconductor field effect transistor (MISFET) based on single crystal GaN-AlxGa1−xN heterostructures. The device structure layers were deposited over sapphire substrate using low pressure metalorganic chemical vapor deposition. We discuss the fabrication and characterization of MISFET devices using single crystal GaN as the insulator layer. These were fabricated on isolated mesas using TiAu for the source and drain ohmic contacts and silver for the gate Schottky. For devices with a gate length of 4 μm (channel opening i.e. source to drain separation of 10 μm), a transconductance of 20 mS/mm was obtained at -1 volt gate bias. Complete pinchoff was observed for a gate potential of -15 volts. Device performance is compared to that for a GaN MESFET of identical dimensions.Due to its direct bandgap tunable from 3.4 to 6.2 eV AlxGa1−xN is an important semiconductor for devices in the ultraviolet and visible parts of the spectrum. The large bandgap, potential of heterojunction formation and the insulating nature of AlN make AlxGa1−xN an ideal material system for high performance metal semiconductor field effect transistor (MESFET) devices requiring high operation temperatures. Availability of the insulator (single crystal AlN or GaN) also makes possible the fabrication of metal insulator field effect transistor (MISFET) devices which has been an elusive goal for the GaAs based III-V materials technology.High quality single crystal GaN films have been deposited on sapphire and several other semiconductor substrates using metalorganic chemical vapor deposition (MOCVD)1,2, molecular beam epitaxy (MBE)3 and vapor phase epitaxy (VPE)4. Recently we have reported on quantum confinement5, room temperature stimulated emission6, and 2-dimensional electron gas in GaN-AlxGa1−xN heterostructures7,8. We have also deposited single crystal insulating GaN and A1N over sapphire using atomic layer epitaxy9,10 and fabricated high responsivity photoconductors11. We now report on the fabrication and characterization of FET devices using single crystal GaN-AlxGa1−xN heterostructures. This forms the basis of high temperature transistor devices based on the AlxGa1−xN material system.
Electronic Structure of Wide-Band-Gap Chalcopyrites
Authors: Petukhov A. , Lambrecht W. R. L. , Segall B. 
Published: March 2011

ABSTRACTElectronic band structures, equilibrium lattice constants and structural parameters, cohesive energies, and bulk moduli calculated by means of the linear-muffin-tin orbital method are presented for BeSiN2, MgSiN2 and MgSiP2 chalcopyrites. The relationships of these compounds to the “parent” III-V compounds are clarified.
Growth and Characterization of Layered Structures of Silicon Carbide and Aluminum Nitride
Authors: Sywe B. S. , Yu Z. J. , Edgar J. H. , Chaudhuri J. 
Published: March 2011

ABSTRACTHeterostructures of SiC and AlN in either sequence, AlN on SiC or SiC on AlN, were grown on Si, Al2O3, and 6H-SiC substrates by (metalorganic) chemical vapor deposition (CVD). On Si substrates, a SiC layer was first grown by a two-step technique and an AlN layer was deposited subsequently. On other substrates, an AlN layer was first grown, followed by SiC deposition. Multi-layered structures (SiC/AlN/SiC) were also produced to demonstrate the ability of heteroepitaxy of SiC and AlN on each other.AlN grown on 3C-SiC were highly oriented polycrystalline films. AlN films on 6H-SiC, SiC films on A1N/Al2O3, and SiC films on AlN/6H-SiC were single crystal. In the latter two cases, the SiC films were in hexagonal structure. These SiC films were smooth and specular in appearance and showed n-type conductivity.
Optical Characterization of Amorphous SiNx:H Films Prepared by Plasma-Enhanced CVD
Authors: Tsai Rung-Ywan , Kuo L. C. , Ho F. C. 
Published: March 2011

ABSTRACTAmorphous SiNx:H thin films were prepared by plasma-enhanced CVD process. The effects of preparation conditions on the optical properties, compositions, and deposition rates of a-SiNx:H films were systematically studied by means of spectrophotometer, ellipsometer, and infrared spectroscopy measurements. It has been found that the refractive indices decrease with increasing the NH3 gas flow rate and the rf power, and increase with increasing the electrode spacing. Conversely, the deposition rates increase with increasing the NH3 gas flow rate and the rf power, and decrease with increasing the electrode spacing. There was no obvious effect of substrate temperatures ranging from 250 to 320°C on the optical properties and deposition rates of a-SiNx :H films. The decrease of the refractive index and the increase of the deposition rate were due to the increase of the nitrogen composition x occurring in the a-SiNx:H films. Refractive indices n and extinction coefficients k of a-SiNx:H films can be varied from n = 3.6 and k = 0.1 for x = 0 (pure a-Si:H) to n = 1.8 and k = 0 for x = 1.33 (pure a-Si3 N4:H) at the wavelength of 633 nm.
Chemically Modified Second Harmonic Generation at Surfaces on Vicinal Si(111) Wafers
Authors: Emmerichs U. , Meyer C. , Leo K. , Kurz H. , Bjorkman C. H. , Shearon C. E. , Ma Y. , Yasuda T. , Lucovsky G. 
Published: March 2011

ABSTRACTUsing surface second harmonic generation (SSHG) at 1053nm, we study the influence of off-axis orientation and surface structure of silicon (111) surfaces. We study wafers cut at angles between 0° and 5° in the [112] direction. The surface structure is varied by thermal oxidation at 850°C, annealing, and thinning the oxide in a HF solution. For comparison, nitride films are also investigated. The characteristic rotational symmetry of the SSHG-signal for (111) flat (non-vicinal) surfaces is enhanced by a Si/SiO2 interface. The oxide layer also influences the signals due to the steps on vicinal surfaces. The results are discussed in comparison with a microscopic model of the oxidized misoriented surface.
Blue Shifting the Excitonic Transition in Multiple Quantum Wells by Rapid Thermal Processing
Authors: Malin Jay I. , Hsieh K. C. 
Published: March 2011

ABSTRACTSilicon doped multiple quantum well (MQW) detector structures were rapid thermally processed (RTP) for the purpose of blue shifting the excitonic transition. Structures were encapsulated with Sio2 prior to the anneal as such enhanced the degree to which interdiffusion occurred within the structure. This further lead to a blue shift in the exciton energy corresponding to the n=l transition which was observed by photoluminescence (PL) measurements. Having examined the PL spectra of various SiO2 encapsulated samples and performing variable intensity PL measurements, a peak corresponding to a defect at ∼ 80meV above the valence band was further observed. In addition, a variation in the degree to which disordering occurs has been observed under various physical conditions including doping and GaAs capping.
Studies of Interface Formation and Its Influence on Optical Properties of GaInAs/InP QW Structures
Authors: Seifert W. , Liu X. , Samuelson L. 
Published: March 2011

ABSTRACTIt is a well-known phenomenon that the luminescence energies of nominally n monolayer (1 ML = 0.239 nm) thick QWs of GalnAs in InP are shifted to longer wavelengths in comparison to calculated values. The reason is seen in the formation of (Ga)InAs(P)-interfaces, one or a few ML thick, which contribute to the effective potential of the QW.Based on a comparison of MBE and MOVPE and on properties of QW structures grown by MOVPE under different conditions we conclude that high AsH3 pressures and low growth temperatures favour the formation of arsenic multilayers on the surface, which act as the main arsenic source for the formation of graded InAsxP1−x interface layers.
Interaction of Coal Particles Injected into Argon and Hydrogen Plasmas
Authors: Littlewood K. 
Published: March 2011

ABSTRACTRapid heating of coal to temperatures in excess of 1500 K yields lower hydrocarbons which, if conditions are correct, will consist mainly of acetylene. Such conditions involve reaction times of 0.1 to 10 ms, together with rapid rates of quenching. Appropriate conditions have been achieved on a laboratory scale using a d.c.-arc plasma jet.
Design and use of an Efficient Plasma Jet Reactor for High Temperature Gas/Solid Reactions
Authors: Giacobbe F. W. , Schmerling D. W. 
Published: March 2011

ABSTRACTA unique and efficient plasma jet reactor has been developed and used to study the high temperature production of carbon monoxide from a reaction between powdered carbon and a pure carbon dioxide plasma. The plasma jet reactor was designed to allow the injection of powdered carbon above the arc discharge region rather than into the plasma flame below the arc discharge region. High yields of carbon monoxide, produced at relatively high efficiencies, were a direct result of this technique. The plasma jet was also designed to enable rapid changing and testing of various anode insertsAverage yields of carbon monoxide in the product gases were as high as 80–87% in selected experimental trials. Carbon monoxide was produced at rates exceeding 15,000 1/hr (at STP) with a power expenditure of 52 Kw.
In-Flight Metal Extraction in a Novel Plasma Reactor
Authors: Reid K.J. , Moore J.J. , Tylko J.K. 
Published: March 2011

ABSTRACTA new plasma reactor system based on a stable expanded conical plasma reaction zone has been used to examine the in-flight extraction of metals from mineral concentrates. The basic principles of the plasma system and details of the equipment are described. Results obtained from the treatment of taconite concentrate, low grade chromite concentrate and a copper-nickel concentrate are presented and discussed.
Plasma-Melted and Rapidly-Solidified Powders
Authors: Cheney Richard F. 
Published: March 2011

ABSTRACTA novel process is described for making rapidly solidified powders. In its simplest form, powders are melted in a high-temperature plasma and the resulting high-velocity spray is quenched into a fluid medium. Rapid cooling rates are achieved by free fall in inert gases, by quenching into liquid argon or nitrogen, or by impacting against a chilled, moving substrate. Any composition can be processed as long as it or its constituents are available in powder form. When necessary, alloy or composite components are agglomerated to 15–45μm diameter prior to plasma synthesis. The agglomeration is typically achieved by spray drying. Powders with melting points up to and including tungsten have been melted.
Melting of Powder Particles in a Low Pressure Plasma Jet
Authors: Wei D. , Apelian D. , Correa S. M. , Paliwal M. 
Published: March 2011

ABSTRACTA numerical model has been developed to predict the temperature profile of particles injected in a D.C. plasma jet. The equations governing particle melting were applied to spherical powders of binary model alloys. Thermophysical properties of the gas and the powder material have been taken to be temperature dependent. In the proposed model, the latent heat of melting was taken into account by introducing apparent enthalpy as a function of the fraction of liquid formed which can be derived from equations describing non-equilibrium melting. The temperature and velocity profiles of the plasma jet used in this analysis are for a free jet (without target interference) and were calculated using the parabolic Navier-Stokes equation with a K-E turbulence model. Correction factors have been introduced to take into account non-continuum effects encountered in the low pressure environment and the results show that both heat and momentum transfer between the plasma gas and the injected particles are reduced.
Microprocessor Control of the Spraying of Graded Coatings
Authors: Kaczmarek R. , Robert W. , Jurewicz J. , Boulos M.I. , Dallaire S. 
Published: March 2011

ABSTRACTA systematic study was made of the characteristics of a microprocessor controlled powder feeder in view of its utilization for the deposition of graded coating. The unit tested had the capability of feeding three different powders at rates which could be continuously varied up to about 40 g/min. MgOZrO2. was deposited on a stainless steel substrate using a series of thin (Ni/Cr)-Zirconia coats as intermediate layers. The results showed that such a technique could provide a valuable means of achieving a precise and effective control on the composition of the intermediate layers which can have important effects on the final quality of the deposit.
On the Allowance for the Temperature Dependence of Plasma Properties for Selection of Dimensionless Numbers to Correlate Characteristics of Electric Arcs
Authors: Vashkevich V.A. , Kravchenko S.K. , Laktyushina T.V. , Yasko O.I. 
Published: March 2011

ABSTRACTPlasma properties as a function of heat conduction are approximated by the power-law relation, for instance, σ= σo (S*/So)nσ. Then, the temperature effect on the dimensionless number is allowed for by a factor, (S*/So)γ, the value of which is estimated by equating the dominant number or the whole set of numbers to unity. Substituting this value into the generalized equation gives the form of the correlation function. A relative contribution of each number, K1, is determined from the comparison of the exponents of the dimensionless numbers with the experimental ones.