bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sub-Micron Selective Photoluminescence in Porous Si by Focused Ion Beam Implantation
Authors: Steckl A. J. , Xu J. , Mogul H. C. , Mogren S. 
Published: March 2011

ABSTRACTThe effect of Si doping on the formation of stain-etched porous Si and its photoluminescent properties was studied. Porous Si is obtained by purely chemical etching of crystalline Si in a solution of HF:HNO3:H2O in the ratio of 1:3:5. We have observed that an incubation time (ti) exists between the insertion of Si into the solution and the onset of porous Si production. This incubation time was found to be a strong function of hole concentration in both n- and p-Si. In p-Si, the ti decreased rapidly with increasing conductivity, whereas for n-Si the opposite (but not as pronounced) trend was found to be the case. For example in (B-doped) p-Si, ti, is only ∼0.5 min for 250 (Ω-cm)−1 but increases to ∼ 5 min for 0.2 (Ω-cm)−1. In (P-doped) n-Si substrates ti was ∼ 8 min for 0.2 (Ω-cm)−1 increasing to ∼ 10 min for 7 (Ω-cm)−1. Photoluminescence (PL) measurements of the porous Si obtained on substrates of various conductivity (p and n) show similar spectra, namely a peak at around 1.94 eV with a full width at half-maximum (FWHM) of about 0.5 eV. Based on the ti difference, we have fabricated localized photoemitting porous Si patterns by Ga+ focused ion beam (FIB) implantation doping and B+ broad beam (BB) implantation doping of n-type Si. Using 30 kV FIB Ga+ implantation, sub-micron photoemitting patterns have been obtained for the first time.
Luminescent Porous Silicon Investigated by accelerator analytics
Authors: Steiner Peter , Weidhaas Jens , Lang Walter 
Published: March 2011

ABSTRACTElectroluminescent nanoporous silicon is investigated by accelerator techniques. Rutherford Backscattering Spectroscopy (RBS) and Nuclear Reaction Analysis (NRA) are used to measure the oxygen content. The stoichiometry is Si1O1.8 in the top layer and Si1O0.8 in 6 μm depth. Channeling experiments show that only very weak channels are present.
Integrated Heterostructure Devices (IHDS): A New Approach for the Fabrication of High-Efficiency Blue/Green Light Emitters Based on II-VI Materials
Authors: Lansari Y. , Yu Z. , Ren J. , Boney C. , Cook J. W. , Schetzina J. F. 
Published: March 2011

ABSTRACTIntegrated heterostructure devices (IHDs) comprised of II-VI materials in multi-layered structures for light emitting diode (LED) and laser diode (LD) applications are described. These IHDs combine a light emission multilayer structure (wide band gap II-VI layers) with an abrupt or graded heterostructure (comprised of narrow band gap II-VI layers) for improved ohmic contact to the upper p-type layer of the light emitting structure.
TEM Investigations of CdTe/GaAs(001) Interfaces
Authors: Angelo J. E. , Gerberich W. W. , Bratina G. , Sorba L. , Franciosi A. 
Published: March 2011

ABSTRACTIn this study, cross-sectional transmission electron microscopy (XTEM) was used to investigate the defect structure which occurs at the interface between CdTe(001) and GaAs(001). The heterostructures were fabricated by molecular beam epitaxy on chemically etched and thermally deoxidized GaAs(001) substrates as well as GaAs(001) buffer layers grown in-situ by molecular beam epitaxy. This allowed for investigation of the GaAs surface preparation on the subsequent interfacial structure. The as-etched substrate led to a microscopically rough interface with the CdTe depositing in etch pits on the GaAs surface, while growth on the buffer layer led to a macroscopically flat interface. Further, growth was accomplished on different Te-induced surface reconstructions ((6×1) vs (2×1)) in an effort to understand the role of the precursor surface treatment on the subsequent interfacial structure. In this case growth on the (6×1) reconstruction led to the introduction of (111)-oriented inclusions at the interface, while the (2×1) reconstruction led to pure (001)-oriented growth. A mechanism for the formation of planar defects at the CdTe/GaAs(001) interface is described which is based on local misorientations of the CdTe and GaAs. Finally, preliminary results of ex-situ annealing experiments on the interfacial defect structure will be discussed.
CW Nd:YAG Laser Deposition of CdS Thin Films
Authors: Wang X. W. , Finnigan D. J. , Noble R. , Mattocks P. 
Published: March 2011

ABSTRACTThere are two phases of CdS, wurtzite (hexagonal) and zincblende (cubic). To the best of our knowledge there is no report on the growth of large single crystal cubic CdS. Although there have been reports on the vapor deposition of cubic dominated CdS thin films, physical measurements were limited. Substrate material has been considered as the primary factor in attaining the cubic dominated CdS thin films. We report new results on CW Nd:YAG laser deposition of CdS thin films at various temperatures. X-ray diffraction patterns show that the films deposited at 200°C have a dominant cubic phase, those at 400°C being hexagonal. Optical transmission measurements reveal room temperature absorption edges of 515nm and 500nm for films deposited at 200°C and 400°C, respectively. Transmission electron microscopy further reveals differences in crystal structure of the two films. Raman spectra of the cubic film is similar to that of the hexagonal film.
Molecular Beam Epitaxy of PbTe/EuTe Superlattices
Authors: Springholz G. , Bauer G. 
Published: March 2011

ABSTRACTUsing reflection high energy electron diffraction (RHEED), the heteroepitaxy of EuTe on PbTe (111) by molecular beam epitaxy (MBE) was investigated. The resulting EuTe (111) surfaces exhibit different surface reconstructions corresponding to a Te-stabilized or a Eu-stabilized surface. We have observed perfect 2D layer-by-layer heteroepitaxial growth and RHEED intensity oscillations only for a small range of growth conditions. Using such optimum conditions, we have fabricated strained PbTe/EuTe superlattices with superior structural perfection, as shown by high resolution x-ray diffraction.
Increase in Schottky Barrier Height in the CoSi2/Si (100) Interface Caused by Hydrogen
Authors: Marwick A. D. , Aboelfotoh M. O. , Casparis R. 
Published: March 2011

ABSTRACTIt is shown that the presence of 8 × 1015 hydrogen atoms/cm2 in the CoSi2/Si (100) interface causes an increase in the Schottky barrier height of 120 meV, and that passivation of dopants in the substrate is not the cause of this change. The data is evidence that the position of the Fermi level in this interface is controlled by defect-related interface states. After hydrogenation the Schottky barrier height agrees with that predicted by theory for Fermi level pinning by virtual gap states of the silicon.
Passivation of Gaas by Novel P2S5/(NH4)2Sx Sulfurization Techniques
Authors: Hsieh J. T. , Sun C. Y. , Hwang H. L. 
Published: March 2011

ABSTRACTA new surface passivation technique using P2S5/(NH4)2S on GaAs was investigated, and the results are compared with those of the (NH4)2Sx treatment. With this new surface treatment, the effective barrier heights for both Al- and Au—GaAs Schottky diodes were found to vary with the metal work functions, which is a clear evidence of the lower surface state density. Results of I—V measurements show that P2S5/(NH4)2S—passivated diodes have lower reverse leakage current and higher effective barrier height than those of the (NH4)2Sx -treated ones. Auger Electron Spectroscopy, X—ray photoelectron spectroscopy and Raman scattering measurements were done to characterize the surfaces including their compositions and surface band bending. In this paper, interpretations on this novel passivation effect is also provided.
Optical Detection of Band Gap Variations Due to Ordering in Ga0.47In0.53As on InP
Authors: Arent D. J. , Bertness K. A. , Kurtz Sarah R. , Bode M. , Olson J. M. 
Published: March 2011

ABSTRACTA reduction in the optical energy gap of more than 65 meV has been observed in In0.53Ga0.47 As grown on (100) InP by atmospheric pressure metalorganic vapor phase epitaxy. The band gap energies were deduced from room temperature photocurrent spectroscopic measurements, accounting for differences in composition and strain. Spontaneous CuPt type ordering of In and Ga atoms on the (111) subplanes of the InGaAs2 was confirmed by transmission electron microscopy. Superlattice signatures in the transmission micrographs were observed only for samples with associated reduced band gap energies, and were confirmed by visible double periodicity in high resolution images. In0.53Ga0.47 As was grown under a variety of conditions, some which promoted ordering. In general, lower growth temperatures and moderate (∼4 μ/hr) growth rates promoted a greater degree of ordering and reduction of the band gap energy. The influence of growth conditions on the ordered structure is considered within the context of current theories.
A Tunable Schottky Barrier to n-GaAs Using Ni(Ga,Al) Contacts
Authors: Chen C-P. , Jan C-H. , Chang Y. A. , Kuech T. 
Published: March 2011

ABSTRACTThe Schottky barrier heights of Ni(GaxAl1−x)/n-GaAs contacts have been measured by the I-V and C-V techniques. Contacts with x = 0.0, 0.25, 0.5, 0.75, and 1.0 have been prepared, and a wide range of Schottky barrier heights, 0.66 to 0.96 eV, can be achieved by varying the composition of the alloy contacts. After annealing at 400 °C, the barrier heights increase continuously from 0.66 to 0.96 eV as x decreases. The interfacial stability between the Ni(Ga,Al) contacts and GaAs has been examined by SAM. The modulation of the Schottky barrier height and the interface stability are explained by a thermodynamic and kinetic analysis of the GaAs-NiGa-NiAl-AlAs system.
The Study on the Pt Barrier Effect in Al/Pt/Ti/n-GaAs
Authors: Kuragaki T. , Hattori R. , Yajima K. , Sato K. , Takano H. , Otsubo M. , Mitsui S. 
Published: March 2011

ABSTRACTThe degradation mechanism of the Schottky contact of Al/Ti/n-GaAs and Al/Pt/Ti/n-GaAs under the heat treatment of 300°C has been investigated. Barrier height of the Al/Ti/n-GaAs Schottky contact degrades drastically after the heat treatment, in which Ti-Al alloy and Ga out-diffusion have been observed. On the other hand, the barrier height of Al/Pt/Ti/n-GaAs contacts is stable under the heat treatment and, Al-Ti alloying as well as Ga out-diffusion in the metals could not be noticed. From these results, it is presumably concluded that the degradation of the Schottky contacts under the heat treatment is closely correlated with the Ga atom out-diffusion from GaAs surface into the metal films after Al-Ti alloy reach to the GaAs surface. The barrier height reduction after the heat treatment can be explained by the formation of the donor type level at the interface due to the Ga vacancy pile-up arose from the Ga out-diffusion. Pt layer was proved to be an effective barrier suppressing the intermetallic alloying and preventing out-diffusion of Ga.
The Effects of Growth Sequence on the Electronic Properties of Al-Ge-Ni Ohmic Contacts on (001) GaAs
Authors: Lampert W. V. , Haas T. W. , Lambers E. S. , Holloway Paul H. 
Published: March 2011

ABSTRACTThe growth sequence of Al, Ge, and Ni metals was shown to dramatically affect the amount of heat treatment time required to convert the electrical properties from Schottky to ohmic behavior. Differences in the heat treatment times required to convert from rectifying to ohmic contact were dependent on the doping concentration of the contact layer and on the heat treatment temperature. Interdiffusion of component elements and phase formation have been studied to determine the origin of these effects. Auger depth profiles and X-ray diffraction have been used to determine the interdiffusion and phase formation resulting from various types of thermal processing. Elemental profiles and identification of phases of Ni-Ga, Ni-As, and Ni-Ga-Ge will be used to explain the origin of ohmic behavior.
Schottky Barrier Formation and Long Term Stability of Metal/N-Lnp Interfaces
Authors: Shi Z. Q. , Anderson W. A. 
Published: March 2011

ABSTRACTThe formation of reliable high barrier height Schottky contacts to n-InP is essential for useful device fabrication. Fermi-level pinning traditionally has restricted the application of InP due to large reverse leakage current. Recently, we have proposed the enhancement of Schottky barrier heights (up to 0.98 eV) by deposition with the substrate cooled to low temperature (LT=77K) rather than at room temperature (RT=300K). Studies of the resistance of thin metal films during deposition reveals significant differences in metal nucleation for RT and LT diodes. For the long term stability study, a reverse bias of 2.0V was applied to both RT and LT diodes for more than 1500 hours. Then a constant forward current of 20 mA/cm2 was applied to the diode. The reverse current and forward voltage were recorded as a function of the testing time. After each step the saturation current density (Jo), barrier height (øB), and ideality factor (n) were measured using the current-voltage (I-V) technique. For a LT Au/n-InP diode, the Jo, øB, and n factor were found to be 3.4 × 10−11 A/cm2, 0.98 eV, and 1.31 before testing, and 4.8 × 10−10 A/cm2, 0.92 eV, and 1.31 after testing. The reverse leakage current was nearly constant during the testing. The forward voltage showed a little drop with time. The ultra-high øB and good stability of the LT diodes will be discussed in terms of the interface modification.
Study of Ohmic Contacts on P-Type ZnSe and ZnSe Epitaxial Layers Grown by Molecular Beam Epitaxy
Authors: Piskoti C. , Mykolajenko B. , Vaziri M. 
Published: March 2011

ABSTRACTTo study the formation of ohmic contacts, several metals have been deposited on p-types ZnTe and ZnSe epitaxial layers. The metals were deposited on the layers either by simple evaporation or by electroplating. The current-voltage characteristics associated with each metal contact were measured. The preliminary results of these measurements indicate that electroplating is a better technique for making ohmic contact to these layers.
Growth and Device Applications of Epitaxial Insulators on Semiconductors
Authors: Ishiwara Hiroshi 
Published: March 2011

ABSTRACTGrowth characteristics and device applications of heteroepitaxial insulator/semiconductor structures are reviewed. Discussions are made on both fluoride insulators such as CaF2, SrF2, BaF2, LaF3, CeF3, etc. and oxide insulators such as MgOAl2O3, CeO2, ZrO2, (Ba,Sr)O, SrTiO3, etc. First, the growth methods and typical results on the crystalline quality of the films are mainly discussed. In some cases, growth characteristics of semiconductor overlayers on the insulator / semiconductor structures are also discussed. Finally, applications of these structures to future electron devices are reviewed.
Growth and Characterization of Epitaxial BaF2 on InP
Authors: Jia Q. X. , Anderson W. A. 
Published: March 2011

ABSTRACTEpitaxial thin films of BaF2 were deposited for the first time onto (100) InP at a substrate temperature of around 450°C to 480°C by RF magnetron sputtering. The structural properties of the BaF2 film were a strong function of the substrate temperature during film deposition. X-ray diffraction analysis revealed a pure c-axis orientation perpendicular to the substrate surface. Scanning electron microscopy surface scan indicated a highly textured film with grid growth morphology. Ellipsometry measurement on the films gave a refractive index in the range of 1.4 to 1.6. The capacitance vs voltage analysis on a capacitor with a structure of Au/BaF3/InP demonstrated a dielectric constant of around 7.3 for the BaF2.
GaN/AlxGa1−xN Wurtzite Semiconductor Superlattices
Authors: Yuan Ren Shang , Dow John D. 
Published: March 2011

ABSTRACTA theory of electronic structures of NGaN×NAlGaN GaN/Alx Ga1−xN wurtzite semiconductor superlattices (grown in the direction of the c-axis) is developed and used to predict the superlattices' band structures, energy gaps, and the “deep” energy levels of substitutional s- and p-bonded defects in them. In addition, the valence band offset of GaN with respect to AlN, the one adjustable parameter of the theory, is determined to be about 0.4 times the total fundamental band-gap difference, by fitting the optical data for the superlattices' fundamental band gaps as a function of the layer thicknesses NGaN and NAlN, with the valence band edge of AlN being at lower energy.
Effects of Confinement on Shallow Impurities in GaAs-Ga 1−xA1xAs Quantum Dots
Authors: Osörio Francisco A. P. , HipöLito Oscar , Peeters Francois M. 
Published: March 2011

ABSTRACTThe ground state energy of a shallow impurity placed in the center of a circular quantum dot is studied. The effects of the strength of the confinement potential and a perpendicular magnetic field are investigated theoretically.
Effects of Gamma-Ray Irradiation and Thermal Annealing on Characteristics of 3C-SIC MOS Structure
Authors: Yoshikawa M. , Morita Y. , Itoh H. , Nashiyama I. , Okumura H. , Misawa S. , Yoshida S. 
Published: March 2011

ABSTRACTThermal annealing of interface traps introduced by 60Co gamma-ray irradiation in 3C-SiC metal-oxide-semiconductor (MOS) structures have been studied by high-frequency capacitance-voltage measurements. By isochronal annealing up to 400°C, two recovery stages were observed, which correspond to the annealing of two different types of the interface traps. It was found that introduction of the interface traps was suppressed by thermal annealing before irradiation. Radiation tolerance of 3C-SiC MOS structure is explained in terms of the room temperature annealing of the interface traps introduced by irradiation.
The Optical Properties of Plasma-Deposited SiO2 and Si3N4 Bragg Reflectors in the Spectral Range from 1.8 to 3.0 eV
Authors: Stephens D. J. , He S. S. , Lucovsky G. , Mkkelsen H. , Leo K. , Kurz H. 
Published: March 2011

ABSTRACTWe have prepared 19-layer Si3N4:SiO2/…‥Si3N4:SiO2/Si3N4 (HL/HL/…HL/H), Bragg reflectors by remote plasma-enhanced chemical-vapor deposition, and have adjusted the constituent layer thicknesses to generate highly reflecting films over the entire visible spectrum from approximately 1.8 eV (∼690 nm) to 3.0 eV (∼410 nm). Peak values of the reflectance, in spectral bands with half-widths of ∼0.4 to 0.5 eV, are in the range of 96 to 98 %. The spectral response functions of these stacks exhibit departures from the optical behavior as calculated for exactly periodic structures with λ/4 layer thicknesses, and can be accounted for by taking into account: i) dispersion and absorption in the optical properties of the constituent layers; and ii) departures from the idealized and constant layer thicknessses.
The Effect of Quantum Well Structures on the Thermoelectric Figure of Merit
Authors: Hicks L. D. , Dresselhaus M. S. 
Published: March 2011

ABSTRACTCurrently the materials with the highest thermoelectric figure of merit, Z, are Bi2Te3 alloys. Therefore these compounds are the best thermoelectric refrigeration elements. However, since the 1960's only slow progress has been made in enhancing Z, either in Bi2Te3 alloys or in other thermoelectric materials. So far, the materials used in applications have all been in bulk form. In this paper, it is proposed that it may be possible to increase Z of certain materials by preparing them in quantum well superlattice structures. Calculations have been done to investigate the potential for such an approach, and also to evaluate the effect of anisotropy on the figure of merit. The calculations show that layering has the potential to increase significantly the figure of merit of a highly anisotropic material like Bi2Te3, provided that the superlattice multilayers are made in a particular orientation. This result opens the possibility of using quantum well superlattice structures to enhance the performance of thermoelectric coolers.
Research needs in ARC Technology
Authors: Heberlein J. V. R. 
Published: March 2011

ABSTRACTThe state of the art and the research needs of selected applications of arc technology are described. The selected applications include plasma torch design, plasma synthesis of materials, plasma chemical synthesis and metallurgical processing. The research areas where results can have the broadest impact on the technology are electrode effects, plasma fluid dynamics and non-equilibrium effects.
The Production of Metastable Metallic Particles Directly from the Mineral Concentrate By In-Flight Plasma Reduction
Authors: Moore J.J. , Reid K.J. , Sivertsen J.M. 
Published: March 2011

ABSTRACTCombining the reduction of the mineral oxide to a liquid metal and its rapid solidification provides an energetically favorable route tod provide metastable metallic particles or powders. Such an option is available with the Sustained Shockwave Plasma (SSP) reactor in which the mineral oxide is reduced using a carbon-based reductant within the plasma medium and subsequently rapidly solidified. This paper examines the degree of metastability of these metal particles using optical, electron and Auger microscopy and discusses the potential of this processing route.
The Effect of Structure on the Thermal Conductivity of Plasma Sprayed Alumina
Authors: Fiedler H.C. 
Published: March 2011

ABSTRACTPlasma sprayed deposits of alumina are normally of the metastable gamma phase, which transforms to alpha upon heating to an elevated temperature. The poor thermal conductivity of gamma phase is improved by transforming to alpha, but the improvement is restricted by the fragmented nature of the structure, a consequence of alpha being a denser phase than gamma.Alpha phase has been reported to form when deposits are made on preheated substrates. It was found that reducing the distance between gun and deposition surface, thereby raising the temperature of the latter, resulted in transforming gamma to alpha, and as the temperature continued to rise, alpha formed directly from the liquid. The thermal conductivity of alpha formed directly from the liquid is 0.27 Watt/cm K at 323 K, which approaches the thermal conductivity given for 99.5% pure, 98% dense, polycrystalline alpha alumina.
An Experimental Study of Powder Melting During Low Pressure Plasma Deposition
Authors: Paliwal M. , Apelian D. 
Published: March 2011

ABSTRACTLow pressure plasma deposition (LPPD), a recent advancement in plasma spray metallizing, is currently being developed for high performance materials applications. An experimental study of particle melting within the plasma jet was pursued to identify the effect of the process variables and the material properties on the resultant deposit. In tandem the experimental results have been utilized in the development and verification of a mathematical model for the melting of powder particles during the process.Two binary iron based model alloys - Fe-20 wt% Mn and Fe-20 wt% Cu - were plasma sprayed using Ma 2.4 and Ma 3 guns. Two different methods were used to evaluate the degree of particle melting within the plasma jet. The first method intercepts the particle path in the plasma jet with a glass slide, whereas in the second method the powder particles are collected in free flight using a powder collector (resolidification of powder particles occurs before they impact the collector walls). The droplets which impacted on glass slides and the collected (using the powder collector) powder particles were studied for mode and degree of powder particle melting using scanning electron microscopy. “Sweet spot” deposits (with no relative motion between the plasma gun and the substrate) were also made for the two model alloys in different size ranges using the Ma 2.4 and Ma 3 guns. The resulting deposits were metallographically evaluated. Mode and degree of particle melting injected under different process variables as well as the resultant deposit structures are presented.