bluuebunny/crossref_metadata_2025 huggingface dataset:
Model for solute redistribution during rapid solidification
Authors: Aziz M. J.
Published: February 2003

A microscopic model for impurity uptake at a sharp crystal-liquid interface during alloy solidification is presented in terms of the bulk properties of the liquid and solid phases. The results for stepwise growth and continuous growth at the same interface velocity differ quantitatively but exhibit the same qualitative features. A transition from equilibrium segregation to complete solute trapping occurs as the velocity surpasses the diffusive speed of solute in the liquid. The location of the transition varies little with equilibrium segregation coefficient, and a kinetic limit to solute trapping is found to be quite unlikely. Comparison is made with other models; critical differences are pointed out. Coupled with a growth velocity equation and with macroscopic heat- and solute-diffusion equations, the model forms a complete description of one-dimensional crystal growth. The steady-state solution to this system is indicated for the case of a planar interface. The results are applied to describe regrowth from laser-induced melting. Preliminary comparison with experiment is made. The steady-state solution for thermal and impurity transport is suggested for use whenever detailed computer calculations are unavailable or are unnecessarily involved.
Optical time domain reflectometry at a wavelength of 1.5 μm using stimulated Raman scattering in multimode, graded-index optical fiber
Authors: Nakazawa Masataka , Tokuda Masamitsu , Washio Kunihiko
Published: February 2003

Utilizing the second Stokes line of the stimulated Raman scattering in a multimode, graded-index optical fiber pumped by a 1.32-μm Nd:YAG laser, we have first demonstrated an optical time domain reflectometry at a wavelength of 1.5 μm for a multimode fiber. As a result, the maximum detectable fault location length of 28 km was successfully obtained. The present technique is applicable to the fault location in ultralong length.
Normal elastic wave propagation through a stratified medium
Authors: Morris J. R. , Sisson K. J.
Published: February 2003

The problem of normal wave propagation through an unbounded material which is mildly stratified or periodic is investigated. Rather than applying a standard approach, the problem is treated in the context of scattering theory. A first Born perturbative approximation is employed to calculate reflection and transmission amplitudes and transmission power flux losses due to reflections. A couple of sample calculations are performed.
Detection of secondary electrons in a multidipole plasma
Authors: Hershkowitz Noah , Goettsch R. L. , Chan Chung , Hendricks Kyle , Carpenter R. T.
Published: February 2003

Secondary electrons are identified as a separate component within a plasma in a specifically modified multidipole device. It is shown that secondary electron emission at walls can be comparable to electron production by ionization. It is also shown that secondary electron emission can significantly change Langmuir probe characteristics.
Strain in the GaxIn1−xAsyP1−y quaternary compound
Authors: Sonomura H. , Sunatori G. , Miyauchi T.
Published: February 2003

Internal strain in the GaxIn1−xAsyP1−y quaternary compound, which results from differences in the lattice constants of the binary compounds, GaAs, GaP, InAs, and InP, is estimated assuming Vegard’s law. Compositional variation of the strain depends on the value of a parameter kα which represents the ratio of actual Ga–As bonds to the maximum number of those possible in the compound. The calculated strain in the compound lattice matched to InP takes the maximum value at the composition corresponding to the band gap of 1.4 μm, when kα is smaller than 0.5. The strain in the alloy compound lattice matched to GaAs is also calculated, and our results predict that the strain increases as the band gap increases.
Low-resistivity ohmic contacts on p-type CdTe by pulsed laser heating
Authors: Tews H. , An C.
Published: February 2003

We report the formation of stable and reproducible ohmic contacts on p-type CdTe by pulsed laser heating. Metal pads of Au or Cd3P2 are deposited on the surface of weakly doped CdTe crystals, and are heated with millisecond light pulses from a krypton laser. Good ohmic contacts are obtained between room temperature and 77 K. The contact resistivities at room temperature are 0.5 Ω cm2 for gold contacts, and 0.15 Ω cm2 for Cd3P2 contacts.
Oxidation of tantalum disilicide/polycrystalline silicon structures in dry O2
Authors: Razouk Reda R. , Thomas Michael E. , Pressacco Sylvia L.
Published: February 2003

The oxidation kinetics of tantalum disilicide/polycrystalline silicon composite structures in a dry O2 ambient have been investigated. The formation of silicon dioxide films on the tantalum disilicide was observed for all temperatures evaluated in the range of 800–1000 °C. The oxidation is postulated to occur as a result of the diffusion of silicon from the underlying polycrystalline silicon film through the TaSi2 film. The linear oxidation rate constant is substantially higher than that for the oxidation of single crystal silicon. The oxidation rate was found to be primarily controlled by the diffusion of the oxidant species through the forming oxide resulting in parabolic growth. The parabolic rate constant determined is similar to that obtained in the oxidation of single-crystal silicon with an activation energy of approximately 28 kcal/mol. This value has been previously related to the diffusivity of oxygen through fused silica.
Comment on ’’Reassessment of space-change and central-cell scattering contributions to GaAs electron mobility’’
Authors: Stringfellow G. B.
Published: February 2003

Walukiewicz et al.1 have recently stated that previously reported contributions to the electron mobility of GaAs from space-charge and/or central-cell scattering are in fact insignificant, and that reports of a T−1/2 term in the mobility2,3 are artifacts due to the assumption of Mathiessen’s rule. This conclusion is an overstatement of their results and in fact demonstrably incorrect. First, an analysis of the data reported by Stringfellow2 and Stringfellow and Kuenzel3 as well as others has already been performed by Chattopadhyay et al.4 without assuming Mathiessen’s rule. Their conclusion is that central-cell scattering is indeed significant. Second, the particular data analyzed by Walukiewicz et al. are in fact acknowledged in Ref. 2 to have very little T−1/2 scattering. The magnitude of the scattering cross section for T−1/2 scattering, SCA, for other samples is more than an order of magnitude larger, too large to be ascribed to errors inherent in using Mathiessen’s rule. Experimental data convincingly demonstrate this. The mobility versus temperature curves are lower, especially at higher temperatures, for C as opposed to Zn- or Ge-doped samples where all have the same values of ND+NA (see Fig. 2 of Ref. 3). In addition, recently published data5 for MBE GaAs grown with different C doping levels show that for constant ND+NA, SCA is three times larger for the more highly C doped samples. This could not be due to errors inherent in the use of Mathiessen’s rule. For these samples C clearly introduces an increase in the T−1/2 scattering which is not observed for other acceptors. ufc15xr 1W. Walukiewicz, J. Lagowski, and H. C. Gatos, J. Appl. Phys. 52, 5853 (1981). 2G. B. Stringfellow, J. Appl. Phys. 50, 4178 (1979). 3G. B. Stringfellow and H. Kuenzel, J. Appl. Phys. 51, 3254 (1980). 4D. Chattopadhyay, H. J. Queisser, and G. B. Stringfellow, J. Phys. Soc. Jpn. 49, Suppl. A, 293 (1980). 5G. B. Stringfellow, R. Stall, and W. Koschel, Appl. Phys. Lett. 38, 156 (1981). UFTELTAL G. B. Stringfellow G. B. Stringfellow G. B. Stringfellow The T−1/2 term in electron mobility for GaAs and AlxGa1−xAs is shown not to be solely due to errors inherent in the use of Mathiessen’s rule.
Reply to ’Comment on ’’Reassessment of space-charge and central-cell scattering contributions to GaAs electron mobility’’ ’
Authors: Walukiewicz W. , Lagowski J. , Gatos H. C.
Published: February 2003

Upon considering all aspects of the comment by Stringfellow, the conclusion of Walukiewicz et al. that the data reported by Stringfellow et al. can be explained without invoking the presence of central-cell scattering remains valid.
Enhanced electron injection into SiO2 layers using granular metal films
Authors: Falcony C. , DiMaria D. J. , Guarnieri C. R.
Published: February 2003

The enhancement of electron injection into silicon dioxide layers using a metal-granular metal film-SiO2-silicon structure is reported for Al, Ni, and Mo-SiO2 cermets. This enhancement was found to be stronger for higher metal to oxide ratios. The I-V characteristic curves for these structures follow the Fowler-Nordheim tunneling mechanism behavior, indicating that the dominant effect is an enhancement of the electric field near the granular film-SiO2 interface.
Variation of the elastic constants of 2024-T351 Al under dynamic pressures
Authors: Yaziv D. , Rosenberg Z. , Partom Y.
Published: February 2003

Commercial Manganin gauges were used as in-material gauges in planar shock experiments. The Hugoniot curve for 2024-T351 Al was determined in the 0–10 GPa range and was found to coincide with that of 2024-T4 Al given in the literature and measured by other techniques. The longitudinal sound speed was determined as a function of stress and it was found that Poisson’s ratio decreases while shear modulus increases in this stress range.
Characteristics of plastic deformation and microstructure in copper rods striking a rigid target
Authors: Gerlach U. , Paulus G.
Published: February 2003

The validity of a deformation model proposed by M. L. Wilkins and M. W. Guinan is tested at a microscopic scale for copper projectiles. In particular metallographic investigations confirm the curved plastic front built up during the first microseconds of impact. At higher velocities the material present in the peripheral region of the impact end is recrystallized by thermal effects caused by strong plastic deformation work. The influence of thermal softening on the position of the plastic front is discussed.
Thermal stability of Pd2Si and PdSi in thin film and in bulk diffusion couples
Authors: Tu K. N.
Published: February 2003

Thermal stability of films of Pd2Si and PdSi formed on 〈111〉 Si wafers has been studied by x-ray diffraction. We observed that Pd2Si transformed to PdSi at temperatures around 810±10 °C and PdSi transformed back to Pd2Si when annealed below that temperature. We conclude that Pd2Si rather than PdSi is the thermodynamically stable phase on Si at low temperatures, contrary to the existing Pd-Si phase diagram. The conclusion has been confirmed by annealing bulk Pd-Si diffusion couples at 750 °C to form Pd2Si, then at 850 °C to transform part of the Pd2Si to PdSi, and then returning to 750 °C to convert the PdSi back to Pd2Si and Si. The bulk transformations were measured by x-ray diffraction and electron microprobe.
Density of states in amorphous silicon produced by microwave glow discharge
Authors: Aktik M. , Currie J. F. , Yelon A.
Published: February 2003

Capacitance-voltage characteristics of a metal-oxide-amorphous silicon structure are analyzed in order to obtain the density of states N(E) in microwave glow discharge amorphous silicon films. Our measurement and deconvolution techniques reveal some structure in the density of states profile. At the midgap N(E) is found to be lower than 1017 cm−3eV−1.
Study of charge trapping as a degradation mechanism in electrically alterable read-only memories
Authors: Falcony C. , DiMaria D. J. , Dong D. W. , DeMeyer K. M.
Published: February 2003

Charge trapping in the intervening oxide layers of electrically-alterable read-only memories has been studied for different device configurations incorporating a dual electron injector structure (DEIS). The degradation of the write/erase capability of these devices is associated with electron capture in neutral trapping centers present in both chemical-vapor-deposited and thermal oxides. Annealing the exposed DEIS stack at 1000 °C in N2 results in better cycling capability. The dominant traps in unannealed samples were found to have capture cross sections of σc0x ≊10−16−10−17 cm2, while those in annealed samples have σc0x ≊10−17−10−18 cm2.
Effects of the propagation of transverse ultrasounds on magnetoacoustic phenomena in degenerate piezoelectric semiconductors
Authors: Wu Chhi-Chong
Published: February 2003

Effects of ultrasounds propagating perpendicular to the direction of a uniform dc magnetic field in degenerate semiconductors such as n-type InSb have been studied by using a quantum treatment which is valid at high frequencies and in strong magnetic fields. It is found that the absorption coefficient and change in sound velocity oscillate with the dc magnetic field for the nonparabolic band structure. However, the absorption coefficient vanishes and no oscillations can be observed in the magnetic-field dependence of the change in sound velocity for the parabolic band structure. The discontinuity in the frequency dependence of the change in sound velocity can only be observed in the nonparabolic band structure.
Laser stimulated emission cross sections of Nd glasses
Authors: Tucker Armin W. , Birnbaum Milton , Fincher Curtis L.
Published: February 2003

A laser-comparison method was used to determine the emission cross sections at 1060 nm of Nd glasses used in laser fusion systems. The values obtained for two phosphate glasses (LHG-8) and (Q-88) were 4.0±0.8×10−20 cm2 and 1.7±0.5×10−20 cm2 for a silicate glass (LG-650).
Design studies of volume-pumped photolytic systems using a photon transport code
Authors: Prelas M. A. , Jones G. L.
Published: February 2003

The use of volume sources, such as nuclear pumping, presents some unique features in the design of photolytically driven systems (e.g., lasers). In systems such as these, for example, a large power deposition is not necessary. However, certain restrictions, such as self-absorption, limit the ability of photolytically driven systems to scale by volume. A photon transport computer program was developed at the University of Missouri-Columbia to study these limitations. The development of this code is important, perhaps necessary, for the design of photolytically driven systems. With the aid of this code, a photolytically driven iodine laser was designed for utilization with a 3He nuclear-pumped system with a TRIGA reactor as the neutron source. Calculations predict a peak power output of 0.37 kW. Using the same design, it is also anticipated that the system can achieve a 14-kW output using a fast burst-type reactor neutron source, and a 0.65-kW peak output using 0.1 Torr of the alpha emitter radon-220 as part of the fill. The latter would represent a truly portable laser system.
Leaky Rayleigh waves on a layered halfspace
Authors: Chimenti D. E. , Nayfeh A. H. , Butler D. L.
Published: February 2003

Experimental and theoretical results on the nonspecular reflection of finite acoustic beams incident at and near the Rayleigh angle onto a fluid-solid interface loaded by an elastic layer are presented. Measurements with Gaussian-shaped acoustic beams have been performed on the reflected field amplitude distribution and surface wave speed dispersion in copper-loaded stainless-steel specimens where the fluid medium is water. It is shown that existing theory can be utilized to explain the results by constructing and solving boundary condition equations for the Rayleigh wave pole appropriate for the lossless layered halfspace with the fluid. Excellent agreement with the exact treatment is observed in most aspects of the measurements. In the model calculation the imaginary part of the Rayleigh wave pole is found to display an unexpected maximum at a value of layer thickness over wavelength where the real part corresponds nearly to the transverse wave speed in the layer.
The effects of annealing metal-insulator-semiconductor diodes employing a thermal nitride-InP interface
Authors: Hirota Yukihiro , Okamura Masamichi , Kobayashi Takeshi
Published: February 2003

The interface properties of the thermal nitride film-InP system and its annealing were investigated. To obtain a uniform thermal nitride on a InP crystal, an improved thermal nitriding technique was developed by introducing in situ HCl vapor etching prior to the thermal nitriding. Two devices [MANS (metal-alumina-nitride-semiconductor) diode and FET (field-effect-transistor)] containing a composite gate insulator of a thin nitride film (∼100 Å) and CVD (chemical-vapor-deposition)-Al2O3 film (∼1000 Å) were compared with conventional MAS devices in view of the surface state density (NSS) in the MANS interface at energies near the conduction band edge decreased from 1×1013 to 1×1012/cm2 eV after annealing at 550 °C. A considerable increase in the effective mobility of the MANS-FET was also seen after annealing. However, further annealing at a temperature higher than 600 °C resulted in a gradual degradation in the interface quality. In contrast, only the MAS interface showed degradation. Discussions are given on the effects of annealing on interface properties of MANS and MAS devices, from the view point of surface passivation.
Time-resolved charge injection: Effect of interfacial ambients upon contact performance
Authors: Slowik John H. , Brillson L. J. , Brucker C. F.
Published: February 2003

A new technique has been developed which directly measures carrier transport through the interfacial region at metal-semiconductor (M-S) contacts. The injection current is determined by measuring with fast time resolution the initial rate of decay of surface potential as charge at the surface is injected. Contact performance can be studied in situ using model M-S systems constructed in ultrahigh vacuum, on single crystals cleaved in ultrahigh vacuum. The effect of foreign atoms adsorbed at the Al-CdS interface is presented as an illustration of the technique. For the first time, injected dark currents through the clean interface are found which approximate trap-free space-charge-limited values. Injection is continuously reduced by orders of magnitude as air exposure of the interface is increased during the formation of the M-S contact. Steady-state techniques are insensitive to this contact performance, due to bulk phenomena. The experimental design and performance of the time-resolved charge injection technique are described in detail. Features of time resolution and initial-field uniformity make this a particularly useful probe of complex M-S interfaces.
Electric conduction in nitrogen-rich silicon nitride films produced by SiH2Cl2 and NH3
Authors: Watanabe Kenjirou , Wakayama Shouji
Published: February 2003

The composition and conduction of silicon nitride film formed by the reaction of SiH2Cl2 and NH3 at a low pressure were studied. In the range investigated, this film is amorphous N-rich silicon nitride no matter what the growth conditions. Conduction at room temperature in a steady state was investigated by analyzing the charge distribution without using an average field approximation. Probable charge distribution in the nitride was derived from the thickness dependence of the applied voltage at a constant current and from the flat-band voltage shift giving the interface fields. When current density J = 10−5 A/cm−2, we obtained nt(0) = 3×1018 cm−3, interface fields Es = 4.0×106 V/cm, and the charge centroid ω = 210 Å. The dynamic dielectric constant is calculated as εd = 3.9 from the temperature dependence of conduction, using the average field approximation. The average field approximation is valid only at high temperatures.
Vortex penetration and self-resonant effects in large Josephson tunnel junction
Authors: Jung G.
Published: February 2003

Discontinuity in the resonant voltage (traveling wave resonance) as a function of applied magnetic field has been observed in large Josephson tunnel junctions. It is believed that our results can be explained in terms of peculiar magnetic properties of large junctions of finite length L≫λJ, i.e., the quantization of internal fields and magnetic hysteresis. The discontinuity corresponds to the change of number of vortices penetrating the junction barrier. The experimental voltage jumps are in fairly good agreement with these calculated from the theory.
Magnetocrystalline anisotropy of Fe2+ ion in silicon- or germanium-substituted yttrium iron garnet at zero temperature
Authors: Rudowicz Czeslaw
Published: February 2003

The present work reports the theoretical considerations of the magnetocrystalline anisotropy of ferrous ions induced by tetravalent dopants in yttrium iron garnet. Using the spin Hamiltonian developed earlier by us and the molecular field (h) approximation we derive the cubic anisotropy constants K1 and K2 at zero temperature. We adopt the Alben’s et al. model of twelve inequivalent Fe2+ sites in silicon-substituted yttrium iron garnet. Results are given for h = 400, 300, 200 and the spin Hamiltonian parameters with the trigonal Δ = 300, 400, 500, 600, 700 and the nontrigonal crystal field parameter Γ = 200, 300 cm−1. The agreement with the experimental K1 and K2 is quite good. The discussion reveals that the properties of the far and near sites in the two-center model can now be theoretically explained. The theoretical ratios of K1(far) to K1(near) agree well with experiment. Thus our results speak in favor of the orbital singlet rather than the doublet model assumed previously for Fe2+ in silicon- or germanium-substituted yttrium iron garnets.
Measurements of magnetostriction constants of epitaxial garnet films by double-crystal x-ray diffraction
Authors: Mada Junji , Yamaguchi Kazuyuki
Published: February 2003

Magnetostriction constants λ111 have been determined at room temperature with the double-crystal x-ray diffraction technique by measuring a small change in the lattice parameter. Measurements were carried out for epitaxial garnet films of Y3Fe5O12 and Sm0.85Tm2.15Fe5O12 grown on [111] oriented Gd3Ga5O12 substrates; and also for flux-grown bulk single crystal of Y3Fe5O12. Values of λ111 obtained were −1.7×10−6 for film and −3.0×10−6 for bulk crystal. λ111 of Sm0.85Tm2.15Fe5O12 was −5.0×10−6. The discrepancy in λ111 values between film and bulk Y3Fe5O12 is almost accounted for by the fact that the film can deform only perpendicular to the film plane due to the shear force of the substrate. It has been experimentally demonstrated that λ111 does not depend on film thickness or lattice mismatch, which is consistent with the present analysis.
Conduction mechanism in low-resistivity n-type ZnSe prepared by organometallic chemical vapor deposition
Authors: Stutius W.
Published: February 2003

n-type ZnSe layers with a room-temperature resistivity of less than 0.05 Ω cm and mobilities of ∼400 cm2/(V sec) have been grown on (100) GaAs by organometallic chemical vapor deposition (OM-CVD), using triethylaluminum as a dopant. No further treatment after the layer growth is necessary in order to achieve the high electrical conductivity. An analysis of the low-temperature electrical transport data and of the photoluminescence data, however, suggests that the physical properties of the layers differ from those of ZnSe prepared by other methods. Charge transport occurs via impurity-band conduction in the more heavily doped layers and via thermally activated hopping in the more lightly doped layers rather than via thermally activated extrinsic conductivity. The degree of compensation of donors is larger than 0.5. The exact nature of the compensating centers in the material prepared by OM-CVD is uncertain at this point, although the photoluminescence data suggest the presence of Al-VZn complexes.
Elastic constants of tantalum-tungsten alloys
Authors: Anderson C. E. , Brotzen F. R.
Published: February 2003

The elastic constants of the Ta-W system were determined between 4.2 and 300 K. Anomalous behavior was detected in the temperature dependence of the shear constant c44 near the critical composition of about 50% W. This anomaly is attributed to certain topoligical changes in the Fermi surface of the alloys near the critical composition. The Debye temperature for the alloys was calculated from the elastic constants.
The response of solids to elastic/plastic indentation. II. Fracture initiation
Authors: Chiang S. S. , Marshall D. B. , Evans A. G.
Published: February 2003

The problem of fracture initiation within the vicinity of elastic/plastic indentations is examined. The fractures are considered to originate from one of two sources: preexistent flaws (such as surface cracks formed during mechanical finishing) or stress singularities created by shear bands. The initiation of radial cracks from preexistent flaws has been predicted and shown to correlate quite successfully with threshold data obtained using a range of brittle solids. The trends in fracture initiation associated with the existence of a nucleation step (as appropriate for many median and lateral cracks) are also discussed.
Thermal stability of Pb-alloy Josephson junction electrode materials. IV. Effects of crystal structure of Pb-Bi counter electrodes
Authors: Basson J. H. , Murakami Masanori , Booyens H.
Published: February 2003

Previous investigations have shown that the stability of Pb-alloy Josephson junction devices during repeated thermal cycling between 298 and 4.2 K can be improved by using ε-phase Pb-Bi films as the counter electrode. The improvement was attributed to the hcp structure that has more resistance to strain relaxation by dislocation glide than fcc materials. In the present paper the strain behavior and microstructure changes of α(fcc) and ε(hcp)-phase Pb-Bi films, which were prepared by co-deposition of Pb and Bi onto Si substrates from a single source at 273 K and then cooled to as low as 4.2 K or heated to 350 K, have been studied by using x-ray diffraction and transmission electron microscopy (TEM). Most of the strain introduced into the films upon cooling to 4.2 K due to the thermal expansion coefficient mismatch between the films and the substrate was found to be supported elastically by ε-phase Pb-Bi films thinner than 0.8 μm, and no change in microstructure was observed by TEM upon cooling 0.2-μm-thick films to 100 K. However, significant strain relaxation was observed in α-phase Pb-Bi films as thin as 0.2 μm. The dominant strain relaxation mechanism in the α-phase film at low temperatures was very similar to that observed in Pb films: Dislocations glided across the grains to relax the strain, and the glide motion was impeded by the grain boundaries, the native oxide on the film surface, the substrate and twins. Upon warming the film to room temperature, a large number of dislocations remained, and did not slip out as in the case of the Pb films. In addition to strong resistance to strain relaxation of the ε-phase films due to the hcp structure, the fiber structure of the films was found to be unfavorable for dislocation glide. Grain growth in the α-phase films commenced upon heating to 340 K, while in the ε-phase films grain growth was first observed at the higher temperature of 350 K, despite the fact that the ε-phase film has a lower melting temperature. From the present results it is clear that the thermal stability of the ε-phase Pb-Bi films is superior to that of the α-phase films.
The electrical and photovoltaic properties of tunnel metal-oxide-semiconductor devices built on n-InP substrates
Authors: Pande Krishna P. , Shen Chin C.
Published: February 2003

Pd-(n-type) InP Schottky barrier devices have been fabricated on unoxidized and oxidized surfaces and their electrical as well as photovoltaic characteristics have been evaluated. Devices built on the oxidized surfaces show considerably improved characteristics compared with those built on unoxidized surfaces. A saturation current density of 9×10−9 A cm−2 and barrier height of 0.85 eV have been observed for tunnel Metal-Oxide-Semiconductor (MOS) devices compared with 1.1×10−6 A cm−2 and 0.62 eV for Metal-Semiconductor (MS) devices. Effective Richardson constants, obtained from activation energy plot of saturation current density, have been found to be 0.66 and 1.9 A cm−2 K−2 for MOS and MS devices, respectively. Such low values of the Richardson constant, when compared with the theoretical value, provide clear evidence of the modification of current transport mechanism in the presence of an interfacial layer. Photovoltaic cells with an efficiency of 7% have been built on oxidized surfaces without the use of a grid structure or antireflection coatings. Under AMl illumination, the oxidized devices show the following parameters: open circuit voltage = 575 mV, short circuit current = 16.8 mA/cm2, and fill factor = 0.73. Using photoresponse techniques, the diffusion length has been calculated to be 1.78 μm for MOS devices, a value similar to that obtained for MS devices.
Effects of the phase error on the autoregressive spectral estimate in Fourier transform spectroscopy
Authors: Iwama N. , Inoue A. , Tsukishima T. , Sato M. , Kawahata K. , Sakai K.
Published: February 2003

The autoregressive spectral estimation in Fourier transform spectroscopy is examined experimentally in terms of the phase error due to mislocating the zero path difference. Through the nonlinear processing of interferogram, the phase error results in a spectral distortion which somewhat differs from that in the conventional Fourier analysis. A way to reduce the distortion is presented.
Cataphoresis in Ne-O2 mixtures
Authors: Kuehn D. G. , Chanin L. M.
Published: February 2003

Based upon light intensity measurements, cataphoretic segregation was apparent in dc glow discharges in Ne-O2 mixtures. That this was due to a Penning ionization process which would result in an axial variation in electron energy was apparent from the dependence of the Ne light intensity. The use of gold-surfaced electrodes greatly reduced—but did not totally eliminate—O2 loss processes in the cathode region.
Dielectric constants and bond parameters of LiInSe2 and LiGaSe2
Authors: Kamijoh T. , Nozaki T. , Kuriyama K.
Published: February 2003

The dielectric constants of two lithium ternary chalcogenides, LiInSe2 and LiGaSe2, are obtained to be 8.45 and 8.75, respectively, by capacitance measurements at room temperature. The temperature dependence of dielectric constants of both crystals show linear increase with temperature over the range 77–300 K. The temperature coefficients for LiInSe2 and LiGaSe2 are 2.90×10−4 and 3.80×10−4 K−1, respectively. The bond parameters of LiInSe2 and LiGaSe2 are obtained using the Phillips-Vechten’s and Levine’s dielectric model. The bond characteristics are discussed within the concepts of ionicity and transverse effective charge.
Chirped optical heterodyne: A method for real time Fourier processing by coherent detection
Authors: Salzman J. , Schoenberg A. , Katzir A.
Published: February 2003

A scheme is proposed for coherent detection and real time Fourier processing of optical signals. In this scheme an input signal is photomixed at one photodetector with a variable (chirped) frequency output of a tunable diode last (TDL). Part of the TDL radiation is photomixed at a second photodetector with a fixed frequency output of a stable laser. The electrical signals from the two detectors are convolved by a surface scoustic wave convolver. After proper filtering and envelope detection, the convolver output can be shown to give the power spectrum of the input signal. This scheme may be used for spectroscopy in the infrared.
Size effect on the galvanomagnetic properties of a semiconductor
Authors: Smith V. Devon , Deering W. D.
Published: February 2003

Electrical transport coefficients were calculated for a thin, flat-banded, nondegenerate semiconductor having spherical energy surfaces and a scalar isotropic effective mass. The conductivity, Hall coefficient, Hall mobility, and magnetoresistance were evaluated for a thin slab in terms of parametric integrals which were calculated numerically. The relaxation time of the bulk scattering mechanism was assumed to have a power law dependence on the carrier velocity. The surface scattering was assumed to be completely diffuse. The dependence of the transport coefficients on the thickness and magnetic field for a power index of one are displayed in graphical form.
Josephson heterodyne detection at high thermal background levels
Authors: Poorter Tim
Published: February 2003

Point-contact Josephson junctions with a submicron contact diameter have been used as high-frequency mixers (170–220 GHz) under high thermal background conditions. The junction is formed across a full height (0.56×1.06 mm2) waveguide between a 3–5-μm thick Nb whisker and a 0.2-mm diam Nb center conductor of a coaxial line. The best single-side band mixer-noise temperature that was measured is 165 K (± 25%) with a corresponding single-side band conversion efficiency of 0.36±0.03 (a loss of 4.5 ±0.4 dB) at a signal frequency of 185 GHz, including losses in the coupling horn and the waveguide. The performance was measured with the hot-cold source technique. The effects of nonheterodyne response in that situation were investigated in detail. The junctions have been operated in a coherent receiver that can be used on a telescope with only small adaptations. The instantaneous bandwidth of the receiver is about 20 GHz.
Computer model of amorphous silicon solar cell
Authors: Swartz G. A.
Published: February 2003

A computer model to simulate a n+ip+ amorphous silicon solar cell was developed. This model is based on the computer simulations of solar cells by T. Chappell and the Read diode by Scharfetter and Gummel. The model is used to generate field plots, band diagrams, quantum efficiency curves, I-V characteristics, carrier density distribution plots, carrier generation, and carrier recombination plots. The simulated values of short circuit current density, open circuit voltage, fill factor, efficiency, junction quality factor, quantum efficiency, junction quality factor, quantum efficiency, slope of I-V curves at V = 0 and V = Voc are in good agreement with the measured cell values. Computer simulation shows that a major loss mechanism is the back diffusion of holes into the n+ layer which is diminished by a strong electric field provided by a high concentration of ionized donors in the n+ layer. Projection of cell performance based on the production of n+ and p+ contact layers with ionized donor and ionized acceptor concentrations in the 2×1020 cm−3 range indicates cell efficiencies greater than 10%.
Atomic data and level populations of highly ionized manganese
Authors: Bhatia A. K.
Published: February 2003

Electron impact collision strengths and transition rates for manganese ions of the Li I through F I isoelectronic sequence are calculated for transitions between levels of the configurations 2s22pk, 2s2pk+1, and 2pk+2. The excitation rate coefficients and transition rates obtained from these data are used to calculate level populations at temperatures of maximum abundance of the ions. The proton excitation rates for fine structure levels are also included in the level population calculations. The relative intensities of allowed lines are calculated and the calculated wavelengths are compared with the recent observations of the TFR group. The wavelengths of the forbidden and intersystem lines are also given and compared with the observations where available.
Brillouin-scattering measurements of single-crystal forsterite to 40 kbar at room temperature
Authors: Shimizu H. , Bassett W. A. , Brody E. M.
Published: February 2003

The first Brillouin-scattering measurements of single-crystal Mg2SiO4 have been made at 1 atm and pressures up to 40 kbar in a diamond-anvil cell at room temperature. The elastic moduli C11,C22,C33,C44,C55, and C66, and their pressure derivatives were obtained. These results were compared with those obtained by ultrasonic measurements up to 10 kbar. The observation of low dCij/dP slopes for the transverse moduli. C44, C55, and C66, and the evidence for negative second derivatives as well, support Poirier’s proposed mechanism for the olivine→spinel transition due to gliding of close-packed oxygen layers. Moreover, the numerical relationships among photoelastic constants were determined by studying the intensity ratio of LA to TA modes.
Photoluminescence spectrum of p-type AlxGa1−xAs:Ge
Authors: Waters R. G.
Published: February 2003

The results of photoluminescence measurements of p-type AlxGa1−xAs:Ge (with 0.03<x<0.39) grown by liquid phase epitaxy are presented. An investigation of the composition and temperature dependencies of the acceptor-related peak in this range shows that Ge behaves as a shallow effective mass-like center. The discontinuity in the variation in peak energy versus composition that occurs at x = 0.30 is explained rather in terms of a crossing of donor levels associated with the direct and indirect band gaps. It is also shown that the luminescence is characteristic of donor-acceptor recombination involving shallow donors for x<0.30, whereas a deep donor or a vacancy complex is indicated for x≳0.30. The broad emission band at ∼1.5 eV has also been investigated but its source has not been identified. The presence of this band in the room temperature spectrum and the implications for characterization of light-emitting devices are discussed.
Distribution of cation vacancies in copper ferrites with a stoichiometric excess of oxygen
Authors: Nanba N.
Published: February 2003

An expression for the distribution over tetrahedral and octahedral sites of constituent cations and cation vacancies has been derived in copper ferrites Cu1−δFe2+δO4+γ, where δ?0.5 and γ≳0. According to the derived distribution, the calculated saturation magnetization and Seebeck coefficient are in satisfactory agreement with the observed values in copper ferrites Cu0.52Fe2.48O4+γ quenched from 1250 °C under various oxygen partial pressures. These results indicate that no cation vacancy is generated in tetrahedral site but only in octahedral site even at high temperatures.
Improved efficiency of n-CdSe thin-film photoelectrodes by zinc surface treatment
Authors: Reichman J. , Russak M. A.
Published: February 2003

The open circuit voltage, fill factor, and power conversion efficiency of n-CdSe thin-film electrodes for photoelectrochemical solar cells have been improved by treating the surface with Zn++ ions. The overall efficiency of these electrodes was increased from ∼5% to as high as 6.5% with a soaking treatment in 1 M ZnC12. Photoelectrochemical measurement and Auger spectroscopy indicated the observed improvements were the result of a shift in the flat-band potential to more negative values due to the incorporation of zinc into the surface region of the CdSe thin film.
A combination of third-order elastic constants of aluminum
Authors: Powell B. E. , Skove M. J.
Published: February 2003

Finite deformations lead to a stress (σ)-strain (ε) relation of the form ε = s′11σ+δ(s′11σ)2, where s′11 is an elastic compliance, and δ is a linear combination of second-order and third-order elastic constants. Tensile tests performed on Al whiskers oriented in the 〈110〉 direction give δ = 3.8±0.5. This experimental value disagrees with the value of δ = 7.6 computed from third-order elastic constants measured by Thomas.
Zn diffusion and disordering of an AlAs-GaAs superlattice along its layers
Authors: Kirchoefer S. W. , Holonyak N. , Coleman J. J. , Dapkus P. D.
Published: February 2003

Diffusion and disordering experiments have been conducted on an AlAs-GaAs superlattice with the impurity (Zn) diffusion-disordering directed along the layers. Diffusion constants (Zn) and ratios at the low temperature of 575 °C have been determined for the as-grown AlAs (LB ∼140 Å), GaAs (Lz ∼140 Å), and for the resulting impurity-induced disordered AlxGa1−xAs (x∼0.5). These results confirm the work of earlier experiments, with normal or perpendicular impurity diffusion into an AlAs-GaAs superlattice, and for Zn diffusion at 575 °C give D(AlAs)/D(GaAs)∼350.
Exchange constants in ferrimagnetic garnets
Authors: Srivastava C. M. , Srinivasan C. , Aiyar R.
Published: February 2003

The exchange constants JTT JTR, and JRR in the garnet series R3Fe5O12 (R = Y3+, Gd3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+, or Yb3+) have been obtained using the molecular field approximation. The low-temperature magnetization data for all the garnets except Y and Gd garnets have been fitted assuming a temperature-dependent canting on the rare-earth sublattice. These exchange constants are found to be comparable to those obtained for the rare-earth intermetallic RFe4Al8.
Measurement of rear surface temperatures of laser-irradiated thin transparent targets
Authors: Gold S. H. , McLean E. A.
Published: February 2003

Visible emission measurements from the rear surface of laser-irradiated thin transparent target foils show a transient light flash followed by secondary light emission due to rear surface heating. This temporal signature is different from that reported in shock experiments in transparent solids. Rear surface temperature determinations versus time on laser-accelerated CH targets are presented.
Effect of light absorption on the determination of the spin-mixing parameter in F centers
Authors: Baldacchini G. , Gallerano G. , Grassano U. M. , Sergio A.
Published: February 2003

We present a simple way to evaluate the spin-mixing parameter, ε, of the optical cycle of the F center in alkali halides in the case of strong optical absorption. Usually a small optical absorption is required in the commonly used method, based on the monitoring of the magnetic circular dichroism, to determine the value of ε.
The metallization of silicone polymers in the rubbery and the glassy state
Authors: Martin G. C. , Su T. T. , Loh I. H. , Balizer E. , Kowel S. T. , Kornreich P.
Published: February 2003

The vacuum deposition of metals onto poly (dimethylsiloxane) (PDMS) gels was studied as a function of the crosslink density and the polymer substrate temperature during the deposition. Reflectance and conductance measurements were used to characterize the quality of the resulting metal films. Variations in the measurements were found to depend on the substrate temperature during metallization and on the particular metal used. For most cases, the variations of conductance and reflectance can be accounted for by cracks in the metal film and the coarseness of the surface texture.
Anomalous inversion channel formation in enhancement-mode InP metal-insulator-semiconductor field effect transistors
Authors: Shinoda Yukinobu , Kobayashi Takeshi
Published: February 2003

An anomalous inversion channel was formed in the enhancement-mode InP metal-Al2O3-semiconductor field effect transistor (MISFET) after the gate voltage VG returned from a negative to zero voltages. The channel formation was checked by the drain current measurement and electron beam induced current image pattern observation. The anomalous inversion channel current ID strongly depended on the preceding gate bias amplitude (VG<0) and the biasing time. The current ID then gradually decreased down to zero. Contrasting to this, InP MISFET fabricated by using in situ HCl vapor etching technique for surface cleaning never showed such an inversion formation. The observed anomalous inversion formation in the conventional InP MISFET was consistently explained by a trap model that a number of donor-type traps locate inside the InP native oxide layer with the energy below the Fermi level EF and ionization of them via electron detrapping during a negative VG application induces the inversion channel electrons when VG returns to zero. Based on the simple analysis, the trap concentration and the energy were estimated to be 1.3×1019 cm−3 and 0.42 eV below EF, respectively.
Competing ambient effects on the interdiffusion in Pt/Ni/Al films
Authors: Chang Chin-An
Published: February 2003

The ambient effects on the interactions at the Ni/Al and Pt/Ni interfaces have been studied using the Pt/Ni/Al/SiO2/Si structure. A suppressed diffusion of Al in Ni by oxygen is predicted by our surface potential model and confirmed in this study. For the Pt/Ni interface, on the other hand, oxygen is expected to enhance the diffusion of Pt in Ni but suppress that of Ni in Pt. The observed reduction in interdiffusion between Ni and Pt by oxygen indicates a dominant role of the more electronegative metal Pt in determining the ambient effects observed. Such a dominance of the more electronegative metal is consistent with all the earlier observations where the overcoating metal is the more electronegative and only its surface potential change induced by the ambient is considered in explaining and predicting the ambient effects for various systems.
Diffusion of oxygen in silicon
Authors: Watkins G. D. , Corbett J. W. , McDonald R. S.
Published: February 2003

Recently reported measurements of oxygen diffusion in silicon agree within experimental accuracy with a previous estimate D=0.23 exp(−2.561±0.005 eV/kT) cm2 s−1, determined from a direct measurement at lower temperatures of the one-jump process for interstitial oxygen from one Si-Si bond to an adjacent one. The diffusion constant is therefore known over 11 decades and results from a single microscopically identified process. There are few such model textbook examples for diffusion in solids.
Germanium arsenide iodide: A clathrate semiconductor
Authors: Chu T. L. , Chu Shirley S. , Ray R. L.
Published: February 2003

Germanium forms two semiconducting arsenides: the monoclinic germanium monoarsenide, GeAs, and the orthorhombic germanium diarsenide, GeAs2. When the reaction of germanium, arsenic, and iodine in a sealed tube was used for the crystal growth of GeAs and GeAs2, cubic crystals were also obtained. These crystals have been identified by electron microprobe analysis and x-ray and neutron diffraction studies to be germanium arsenide iodide, (Ge38As8)+8⋅8 I−, a clathrate semiconductor. The germanium arsenide iodide cyrstals are n type with a room temperature resistivity of about 1 ohm-cm and carrier concentration of about 5×1017 cm−3. The Hall mobilities are 10–20 cm2/V-sec, relatively independent of temperature. The energy gap estimated from the resistivity-temperature relation is approximately 0.9 eV.
Temperature dependence of the Hall factor and the conductivity mobility in p-type silicon
Authors: Mitchel W. C. , Hemenger P. M.
Published: February 2003

We have measured the Hall coefficient of ultra pure p-type silicon as a function of both magnetic field and temperature in the range 20–50 K, where acoustic phonon scattering dominates. The temperature dependences of the Hall factor and both the Hall and the conductivity mobilities have been determined. The Hall factor was found to have a small deviation from the generally accepted value of 3π/8 and to be slightly temperature dependent. The temperature dependence of the conductivity mobility was found to be T−1.75±0.05.