bluuebunny/crossref_metadata_2025 huggingface dataset:
Series resistance effects in (GaAl)As/GaAs concentrator solar cells
Authors: Charan Shiv , Konagai Makoto , Takahashi Kiyoshi
Published: February 2003

Series resistance of Zn-doped p- (GaAl)As/p-GaAs/n-GaAs solar cells fabricated by liquid-phase epitaxy has been theoretically calculated as a function of sheet resistance of p- (GaAl)As and p-GaAs, and also measured experimentally. The series resistance is strongly affected by the p-layer sheet resistance. From the resistivity measurement, it was found that the resistivity of Zn-doped p-Ga0.3Al0.7As is about 10 times higher than that of the Zn-diffused p-GaAs layer. The high resistivity of Zn-doped p-Ga0.3Al0.7As is caused by the deeper acceptor level (Ea=90 meV) than that for Zn-doped p-GaAs (Ea=20 meV). Fabricated p-p-n solar cells have been operated under a concentration of 700 suns. The cells showed nearly constant efficiency at a concentration lower than 100 suns, but the efficiency decreased monotonically above 500 suns because of the series resistance effect. The additional Zn diffusion into p- (GaAl)As has also been performed after the LPE growth in a closed tube by using ZnAs2. The reduction of p- (GaAl)As resistivity was confirmed; the resistivity decreased from 0.4 Ω cm (without additional Zn diffusion) to 0.03 Ω cm (Zn diffusion).
Static compression of Al2O3 to 1.2 Mbars (120 GPa)
Authors: Gupta Mool C. , Ruoff Arthur L.
Published: February 2003

Pressures up to 120 GPa were generated when a diamond indentor of radius 10.0 μm was pressed against a very thin sample of Al2O3 on a diamond flat. The thin film of Al2O3 was prepared by sputtering of aluminum in an oxygen atmosphere. From the measurement of the electrical resistance of Al2O3 as a function of pressure it was found that Al2O3 remains an insulator at the highest pressure studied, namely, 120 GPa.
The effect of strain-induced band-gap narrowing on high concentration phosphorus diffusion in silicon
Authors: Fair Richard B.
Published: February 2003

A strain effect has been found to explain the anomalous reduction in P diffusivity at surface concentrations greater than ∼4×1020 cm−3. It is shown that at diffusion temperatures, misfit-induced strain causes a reduction in the effective Si band gap up to ∼−130 meV at the solubility limit of P. This band-gap narrowing results in reduced P diffusivity through a relative reduction of P+V= pairs in the surface region. This complex is the dominant species for P transport at high P concentrations. The diffusion of P in the tail region is dominated by V− vacancies liberated during P+V= pair dissociation events. Thus, the tail diffusivity will likewise be reduced by band-gap narrowing in the surface region. These reductions in diffusivity can be by as much as a factor of 6 depending upon temperature and P doping.
Crystallography of CdTe layers on CdS grown by chemical vapor transport
Authors: Bettini M. , Brandt G.
Published: February 2003

The crystal quality of CdTe layers grown on single-crystalline CdS by chemical vapor deposition is evaluated. Different x-ray techniques have been applied to investigate the crystal perfection and defects. Good CdTe layers grow in the sphalerite phase with strong twinning about the [111̄] growth direction. No mixture of cubic and hexagonal phases, polytypes, stacking faults, and fiber texture are observed. Imperfect layers contain polycrystalline areas.
Substrate and doping effects upon laser-induced epitaxy of amorphous silicon
Authors: Bean J. C. , Leamy H. J. , Poate J. M. , Rozgonyi G. A. , van der Ziel J. P. , Williams J. S. , Celler G. K.
Published: February 2003

UHV-deposited amorphous silicon was recrystallized on (100) single-crystal substrates using pulsed Nd : YAG laser irradiation. Prior to deposition, substrates were prepared with either atomically clean surfaces, residual argon ion sputter damage, or from one to three monolayers of residual oxide. Epitaxial regrowth of bulk crystalline quality occurred regardless of substrate preparation. Annealing energy densities were significantly higher, however, for substrates retaining residual impurities. Certain layers were doped with Ga. At moderate doping levels recrystallization behavior was unaffected. At a 2% doping level, the annealing energy threshold dropped by one-half and Ga atoms were displaced toward the epitaxial surface. It is shown that the decrease in energy threshold is due to an impurity-induced increase in light absorption within the amorphous layer. Layers were crystallized with substitutional Ga concentrations of up to 10 times the equilibrium solid solubility limit.
A model for the on state of amorphous chalcogenide threshold switches
Authors: Petersen Kurt E. , Adler David
Published: February 2003

A detailed isothermal model of the on state of amorphous chalcogenide threshold switches is developed. Steady-state carrier generation and recombination processes are discussed and estimated, and the carrier distributions in the radial direction of the conducting filament are calculated under the assumption that there are no axial variations. Simulations of dynamic decay of the filament after the sustaining voltage is removed are used to calculate both the maximum interruption time before reswitching is necessary and the time dependence of the device resistance during decay as functions of the on-state operating point. Good agreement with experiment is obtained. The model predicts a rapid increase of device resistance in the vicinity of the maximum interruption time, and this has been confirmed by subsequent measurements. Since the rise time of the device resistance in this region is limited by the measuring circuitry and essentially independent of the on-state operating point up to at least 100 mA, the electronic nature of both the on-state and the recovery process is convincingly confirmed.
Photocurrent spectral distribution in some crystalline and amorphous materials
Authors: El-Gabaly M. , Wakim F. G. , Sawan Y.
Published: February 2003

The photocurrent spectral distribution in some crystalline and amorphous photoconductive materials has been theoretically investigated. The study is based on the bulk properties of the material and their effect on the bulk recombination lifetime of the photogenerated carriers. The lifetime is assumed to change with the density of the photogenerated free carriers. It is shown that the lifetime depends on the intensity as well as the wavelength of the incident light. The lifetime decreases with increase of light intensity and/or decrease of wavelength. The change of lifetime with wavelength can be used to explain the photocurrent peak which is observed at wavelengths corresponding to the band-gap energy. The explanation applies to crystalline and amorphous samples for which the photocurrent varies as the square root (or some other power smaller than unity) of the light intensity. Theoretical results are in good agreement with the experimental results of flux-grown crystalline TiO2, crystalline As2Se3, and some amorphous materials.
The kinetic behavior of mobile ions in the Al-SiO2-Si system
Authors: Boudry M. R. , Stagg J. P.
Published: February 2003

Thermally stimulated ionic current (TSIC) measurements have been used to study the kinetic behavior of mobile ions in Al-SiO2-Si structures formed by evaporation of Al electrodes onto thermally oxidized Si slices. It is shown that the ionic current under bias-temperature stress is limited primarily by release of ions from traps at the interfaces, and that traps with a range of detrapping energies are involved. A model is proposed which accurately predicts the detrapping rate for an arbitrary temperature-time profile. Its parameters are the initial distribution of ions among the trapping states, n0(E), and a quantity, β, characterizing the attempt-to-escape frequencies for the traps. n0(E) can be derived from analysis of a TSIC curve, given a value for β which can itself be determined by performing the detrapping in two stages. Escape frequencies are typically of the order 4×1011 s−1, in line with theoretical predictions. In the (111) samples studied, n0(E) at a detrapping field of 106 V cm−1 for Na+ ions at the Si-SiO2 interface is found to have a sharp maximum at about 0.75 eV, with a tail extending upwards in energy to at least 1.5 eV. The same distribution is found irrespective of the conditions under which the ions were trapped. At the Al-SiO2 interface, n0(E) is found to depend strongly on the maximum temperature at which the ions were trapped, higher temperatures causing the maximum in the distribution to be shifted to higher energies. This is explained in terms of thermal detrapping of ions initially captured in shallow traps followed by retrapping at the same interface in deeper traps. The total number of available trapping sites at the Si-SiO2 interface is greater than 5×1012 cm−2. It is inferred that the total density of traps at the Al-SiO2 interface is much greater still.
Contact reactions in Pd/GaAs junctions
Authors: Olowolafe J. O. , Ho P. S. , Hovel H. J. , Lewis J. E. , Woodall J. M.
Published: February 2003

The solid-state reaction of thin Pd films with GaAs substrates has been investigated using Auger sputter profiling, x-ray diffraction, He-ion backscattering, and sheet-resistivity measurements. Fast diffusion and dissolution were observed for both As and Ga into Pd, which slowed down after distinct compound layers were formed. The kinetics of Pd penetration into GaAs was found to be controlled by diffusion with an activation energy of 1.4 eV. The As and Ga compounds formed as a result of contact reactions were identified to be PdAs2 and PdGa at 250 °C; PdAs2, PdGa, and Pd2Ga at 350 °C; and PdGa at 500 °C. For each annealing temperature a ’’steady-state’’ time is reached when there is no measurable change in the backscattering spectra. The sheet resistivity of the contact was found to increase with time under isothermal annealing and eventually reached a saturation value. The saturation time of resistivity change is well correlated to the steady-state time. To determine the effect of the contact reaction on device performance, p-n junction solar cells fabricated by diffusing Zn into an n-type GaAs wafer with Pd and Ag contact layers have been tested. An onset of shunting was observed on the solar devices after heat treatments above 200 °C. Results indicated that shunting is most probably due to Pd penetration through localized defects in the p layer of GaAs.
A simplified approach to the current-voltage characteristics of the p+n
p+ diode below reach-through
Authors: Yu S-Y. , Thomas G.
Published: February 2003

The current-voltage characteristics of the p+np+ diode are derived for bias voltages below reach-through condition. The electron current continuity equation is used to find the relationship between the voltage across the forward-biased junction and the total applied voltage. For a narrow central neutral region a joint probability is defined so as to give the probability that a carrier has a velocity above some minimum value and travels across the neutral region without being scattered. The thermionic emission current is then obtained, the J-V characteristics is plotted, and the singularity from the conventional theory at the reach-through is then removed.
Xerographic characteristics of doped and undoped ZnCdS binder layers
Authors: Pillai P. K. C. , Pillai C. K. , Mendiratta R. G.
Published: February 2003

A study of the xerographic characteristics of ZnCdS both undoped and doped with Cu and Ag (separately as well as simultaneously) is reported in this paper. The maximum surface potential and the contrast potential of all the samples studied were observed to be more than 800 and 600 V, respectively. Comparative evaluation shows that the characteristics of Cu-doped ZnCdS are well suited for xerographic purposes. The position of the acceptor energy levels in the forbidden gap are proposed. energy levels in the forbidden gap are proposed.
Oscillator strengths and laser effect in Na2Nd2Pb6(PO4)6Cl2 (chloroapatite), a new high-Nd-concentration laser material
Authors: Budin J-P. , Michel J-C. , Auzel F.
Published: February 2003

Chloroapatite (Na2Nd2Pb6(PO4)6Cl2), a Nd3+ compound with 3.4×1021 ions cm−3 has been shown recently to possess a high fluorescence efficiency. Measurements on single-crystal samples show that the oscillator strengths and the fluorescence quenching are both slightly smaller than in Nd pentaphosphate (NPP). Laser effect with longitudinal Ar* laser excitation is reported for the first time in this material on two lines at 1.0585 and 1.0675 μm, which have orthogonal polarizations and equal thresholds, in agreement with fluorescence spectra. The laser threshold (absorbed power for a given total cavity loss) is nearly equal to that of a NPP crystal in the same cavity.
Single-transverse-mode LiNdP4O12 slab waveguide laser
Authors: Kubodera Ken’ichi , Otsuka Kenju
Published: February 2003

Argon-laser-pumped single-transverse-mode laser operation was obtained with a three-dimensionally confined LiNdP4O12 slab waveguide laser, in which one endface was cylindrically polished and directly coated with a laser mirror. The threshold, the output power, and the oscillating transverse modes were theoretically analyzed, both for transverse pumping and for longitudinal pumping, considering the spatial distribution of the pump beam and the laser beam. The necessary conditions for the pump sources to obtain a TE00 single-transverse-mode oscillation were determined on the supposition of the diode pumping.
Acoustic emission in liquid crystals
Authors: Scudieri F. , Papa T. , Sette D. , Bertolotti M.
Published: February 2003

Acoustic emission in liquid crystals has been experimentally assessed. The emission has been studied as a function of temperature for different mesophases. The effect is attributed to the release of elastic energy involved in the defect dynamics inside the material.
Effects of free-stream velocity and pressure gradients on MHD boundary-layer control
Authors: Chuang Hsing
Published: February 2003

A steady two-dimensional MHD boundary-layer flow on a flat plate with varying hydrostatic pressure and free-stream velocity along the plate and a uniform transpiration through the plate is considered. The momentum boundary-layer thickness is found to increase substantially with injection and negative flow-shape factors. However, it decreases with increasing magnetic interaction numbers. Transpiration, flow-shape factor, as well as magnetic interaction number strongly affect the shearing stress at the wall. Injection and retarding free-stream velocity will enhance the chances of a flow separation, while the magnetic interation number will do just the opposite.
Pressure dependence of gas breakdown by combined laser and microwave fields
Authors: Schmieder Robert W.
Published: February 2003

The effective-field concept is used to derive a breakdown criterion for a model gas subjected to strong laser and microwave fields. This classical model includes diffusion, collisions, and the finite pulse length. The pressure dependence of this criterion is explored, and it is found that, under the proper conditions, it is possible to produce one or two narrow pressure regions in which breakdown will occur, or two broad breakdown regions separated by an extremely narrow nonbreakdown region. The criterion is extended to account for time-dependent field intensities and frequencies.
Excitation of a plasma wave by a right-handed Gaussian EM beam
Authors: Sodha M. S. , Patheja B. L. , Sharma R. P.
Published: February 2003

This paper presents an investigation of the excitation of an electron plasma wave in a hot collisionless magnetoplasma by a right-handed Gaussian EM beam (pump wave) when the plasma wave and the pump wave are propagating along the static magnetic field. On account of the Gaussian intensity distribution of the pump wave, pondermotive force becomes finite and the electrons are redistributed. This redistribution is highly dependent on whether ωc≳2ω0 or ωc<2ω0, where ωc is the electron cyclotron frequency and ω0 is the pump-wave frequency. The modified background electron density leads to coupling between the plasma wave and the pump wave. When the initial power of the pump wave is greater than the critical power for self-focusing, oscillatory self-focusing of the pump wave occurs and the coupling of the two waves are modified. Moreover, the effect of changing the intensity of the magnetic field affects the self-focusing of the pump wave, and the plasma-wave excitation is accordingly affected.
Short-time-scale self-focusing of electromagnetic beams in a magnetoplasma
Authors: Tewari D. P. , Sharma R. R.
Published: February 2003

A Gaussian electromagnetic beam propagating in a plasma in the direction of the static magnetic field gives rise to (i) a ponderomotive force transverse to the magnetic field and (ii) nonuniform heating of electrons. These effects eventually modify the local magnetic field and thus produce a nonlinearity relevant to self-focusing. The critical power for self-focusing on a time scale shorter than the diffusion time (τD≳t) is vth/c times shorter than that on the longer time scale (t≳τD), where vth is the thermal speed of electrons.
Gamma-ray-induced conduction in polyethylene-terephthalate under high electric fields
Authors: Maeda H. , Kurashige M. , Nakakita T.
Published: February 2003

Radiation-induced conduction in polyethylene-terephthalate under high electric field (1×106 to 1.6×108 V/m) has been studied. At field strengths below 1×108 V/m, the induced current reaches its initial steady-state value (primary component) soon after irradiation is initiated, then monotonically decreases with time thereafter. This decrease of current is due to a ’’polarization’’ effect. Above 1×108 V/m, the induced current decreases for a while then increases again to reach the equilibrium value (secondary component). This secondary component is due to the electron injection, enhanced by the fixed positive space-charge accumulation near the cathode. The radiation-induced conductivity of the primary component increases with electric field strength between 1×106 and 1×108 V/m and then shows a saturation tendency above 1×108 V/m. This may be due to geminate recombination in the carrier generation process. The primary component in the 50-μm-thick specimen is deduced to be dominated by a deep-trapping-limited process. The primary component of the induced current in a 6-μm-thick specimen is demonstrated to attain saturation above 1.2×108 V/m.
Defect structure of degraded Ga1−xAlxAs double-heterostructure light-emitting diodes
Authors: Ueda Osamu , Isozumi Shoji , Yamakoshi Shigenobu , Kotani Tsuyoshi
Published: February 2003

The defect structure of degraded Ga1−xAlxAs double-heterostructure (DH) light-emitting diodes (LED’s) was investigated by electroluminescence (EL) topography and transmission electron microscopy (TEM). Two types of dark-line defects (DLD’s), 〈100〉 DLD’s and 〈110〉 DLD’s, and dark-spot defects (DSD’s) were observed in EL patterns of degraded LED’s. Dislocation dipoles or large zigzag-shaped dislocation loops were associated with DSD’s and 〈100〉 DLD’s. The dipoles had Burgers vectors of the type (a/2) 〈011〉 inclined at 45° to the (001) junction plane or (a/2) 〈110〉 parallel to the junction plane and were extrinsic in character. The zigzag-shaped dislocation loops had Burgers vectors of the type (a/2) 〈011〉 and were extrinsic in character. On the other hand, multiple stacking faults which lay in 〈110〉 directions or half dislocation loops which also lay in 〈110〉 directions and had Burgers vectors of the type (a/2) 〈011〉 inclined at 45° to the junction plane or (a/2) 〈110〉 parallel to the junction plane were associated with 〈110〉 DLD’s.
The 〈111〉 line force in a cubic crystal
Authors: Yang H. C. , Chou Y. T.
Published: February 2003

The elastic field of a line force oriented in the 〈111〉 direction in a cubic crystal is analyzed, based on anisotropic elasticity theory. Closed-form expressions for the stress components are presented. The characteristics of the stress field are strongly affected by elastic anisotropy. In the case where the line force is parallel to the singular line, a dilatation field exists but it vanishes when isotropy is approached.
Radiation characteristics of planar channeled positrons
Authors: Pantell R. H. , Alguard M. J.
Published: February 2003

An analysis is presented to determine the characteristics of the radiation from planar channeled positrons. This radiation has interesting properties as a source for the keV photon energy range, and may also be used to investigate the behavior of channeled particles and to characterize the channeling crystal. Several important aspects of this problem are considered, such as line-broadening mechanisms, dependence of the radiation on the properties of the incident particle beam, and effects of anharmonicity in the crystal field potential. The emission has a full width at half-maximum (FWHM) ?13%, is an order of magnitude brighter than bremsstrahlung, is tunable, is linearly polarized, and is highly directional.
The determination of sulfur-ion-implantation profiles in GaAs using Auger electron spectroscopy
Authors: Park Y. S. , Grant J. T. , Haas T. W.
Published: February 2003

Profiles of S+ and S+2 ions implanted at 60 and 120 keV were studied using Auger electron spectroscopy. The maximum sulfur concentration of unannealed samples was found to be 86 nm below the GaAs surface for the 120-keV S+ with a total dose of 2×1016 cm−2, whereas it was 40 nm for the 120-keV S+2 with a dose of 1016 cm−2. These depths compare favorably with the calculated LSS ranges of 89 and 45 nm, respectively. Outdiffusion of sulfur has been observed in sulfur-implanted Cr-doped GaAs following annealing. The absolute sulfur concentrations were obtained by comparing the relative heights of Auger peaks between the implanted sulfur and the sulfur in ZnS and CdS crystals. Limits of detectability for the implanted sulfur were measured to be ∼1019 cm−3.
Shock-induced cracks in molybdenum sheet
Authors: Wongwiwat K. , Murr L. E.
Published: February 2003

Intergranular cracks occurred in shock-loaded molybdenum for specimens of grain size 17 μm and larger; for smaller grain size specimens (<17 μm) there was almost no crack initiation except in very thin specimens with shock loading of high pressure and long pulse duration. Cracks were not nucleated by twin barriers, and grain-boundary ledges appear to be responsible for initiating and propagating the cracks. The crack density was observed to decrease with increasing grain size for both constant peak pressure and pulse duration. In addition, crack density, as measured by the crack length intersecting the unit area of surface, generally increased with increasing shock pressure at constant pulse duration and with increasing pulse duration, at constant shock pressure.
Microdefects in small-diameter silicon crystals grown by the pedestal technique
Authors: Kim K. M.
Published: February 2003

The formation of microdefects in pedestal-grown silicon crystals was investigated by using x-ray topography. Small-diameter (4–5 mm) crystals were grown without crystal rotation, whereby all potential fluid flow instabilities in the melt were significantly reduced. Microdefects (most likely B-type defects) of a uniform distribution with a density of 3×106 cm−3 were still formed in the crystal. No microdefects were present, however, in regions close to the crystal rim, apparently due to the out-diffusion of point defects responsible for the formation of the microdefects; the estimated diffusion coefficient is about 1×10−5 cm2/sec in the temperature range ∼1000–1400 °C.
Acoustoelectric absorption in semiconductors with energy-dependent relaxation time
Authors: Sharma S. K. , Kaw P. K.
Published: February 2003

It is shown in this paper that one can use the Cohen-Harrison-Harrison model of the collision term of the Boltzmann equation (in the presence of an acoustic wave) provided that the CHH model is applied to calculate the current density associated with acoustic wave because of its interaction with electrons in the velocity range v to v+dv. The expression for the total current density is then obtained by performing summation over the entire velocity range. In the absence of any dc electric field, our expression for the conductivity reduces to that obtained by us earlier.
Argon-implanted semi-insulating layer GaAs capacitors
Authors: Meiners L. G.
Published: February 2003

Capacitance-voltage and current-voltage measurements have been performed on metal-semiconductor structures in which the n-GaAs semiconductor was bombarded with 1014 cm−2 30-keV Ar+ ions prior to the gate metalization. The data indicate that the Fermi level is pinned with a resultant barrier height of 0.75 eV. The capacitance measurements have been interpreted by assuming an intermediate dielectric layer between the metal gate and semiconductor, and the surface-state charge density is estimated to be 1012 cm−2 eV−1.
Reply to ’Comment on ’’A systematic experimental and theoretical investigation of the grain-boundary resistivities of n-doped BaTiO3 ceramics’’ ’
Authors: Ihrig Holger
Published: February 2003

The recently published conclusion that Heywang’s model sufficiently describes the electrical resistivities and current-voltage characteristics of a set of equally prepared PTC-type BaTiO3 ceramics was called in question by Hoffmann. In his criticism, Hoffmann also discussed why he considers his PTC model, which includes intergranular second-phase layers, to be the more adequate interpretation. In the following, we answer his objections and strengthen our own conclusions. Furthermore, the reasons for our disagreement with the experimental interpretations and the theoretical assumptions underlying the intergranular second-phase layer model are briefly discussed.
A modified expression of the flat-band voltage due to the fixed surface charge density of a MOS configuration
Authors: Yu S-Y.
Published: February 2003

By considering the finite distance of the semiconductor space-charge center away from the Si-SiO2 interface, a modified expression of the flat-band voltage (VFB) due to the surface charge density (Qss) is derived. For the accumulation and strong inversion cases, the conventional expression Qss/Co, is valid, however, under the depletion condition the modified expression will be used. The VFB is found to be nonlinearly related to Qss, and the expression may be deduced to the conventional form only in the limit that the Qss is low, the semiconductor is heavily doped, and the oxide thickness is large.
Thermodynamic limits to nonlinearity: Lossless energy-storing systems
Authors: Gupta Madhu S.
Published: February 2003

The nonlinearity of the relationship between the extensive and the intensive variables of an ideal energy-storing thermodynamic system in equilibrium is expressed in terms of the higher-order moments of the extensive variable, and is thus shown to have both an upper and a lower bound. The bounds are proportional to the size of the system and for most practical systems the upper bound is more restrictive. As an illustration, the bound is applied to the nonlinearity of varactor diode capacitors, and the lower bound is shown to be far from the presently achieved nonlinearity.
Radio transmission in an elliptical tunnel with a contained axial conductor
Authors: Seidel David B. , Wait James R.
Published: February 2003

Electromagnetic transmission in a straight cylindrical tunnel with imperfectly conducting walls is considered when the cross section is in elliptical form. The presence of a thin axial conductor is also allowed for in the boundary-value formulation. The general matrix solution is simplified by invoking the quasistatic approximation which is shown, at least for circular tunnel geometry, to be valid for frequencies up to 20 MHz. The results of the quasistatic calculations indicated that the attenuation rate of the dominant mode is relatively insensitive to the ellipticity if the cross-section area and the cable-to-wall separation is kept constant.
Computer simulation of exposure and development of a positive photoresist
Authors: Fujimori Susumu
Published: February 2003

This paper applies a theoretical process model developed by Dill et al. to the polychromatic exposure systems. Exposure and development of a positive photoresist are treated with computer simulation for both contact printing and projection printing. Optical interference within resist film and the effect of it on the development condition are investigated theoretically. The results for the two printing systems are compared in order to clarify the differences between contact exposure and projection exposure. It was made clear that (1) the optical interference still has a considerable influence on the condition imposed on the photolithographic process even in the polychromatic exposure environment and (2) the projection exposure with two spectral lines is more sensitive to such parameters as the thicknesses of resist film and the underlying oxide layer than the contact exposure with three spectral lines.
uv preionized thallium-mercury discharge
Authors: Hamil R. A. , Drummond D. L. , Schlie L. A. , Benedict R. P.
Published: February 2003

Stable glow discharges have been demonstrated in thallium-mercury gas mixtures at mercury densities of 3×1019 and temperatures of 500–900 °C. These discharges have shown themselves to be highly efficient in producing excited Tl (72S1/2) atoms and Tl-Hg B2𝒥1/2 excimer molecules. Discharge efficiency as high as 30±10% in producing Tl (72S1/2) and Tl-Hg B2𝒥1/2 points to the possibility of the creation of a Tl-Hg excimer laser operating at similar efficiencies. These highly efficient discharges are thought to be due to very fast transfer of energy from mercury excimers into Tl-Hg. The transfer cross section from excited molecular mercury to Tl (72S1/2) and Tl-Hg excimers is found to be approximately 1.2×10−14 cm2.
On the stress-induced electrical properties of point defects in the sphalerite structure. I. The piezoelectric effect
Authors: Booyens H. , Vermaak J. S.
Published: February 2003

It is shown that the stress fields associated with point defects in crystals with the sphalerite structure lead to piezoelectrically induced polarization charge distributions that are symmetric with respect to the {110} planes and antisymmetric with respect to the {001} planes. The electrical contributions to point-defect–point-defect and dislocation–point-defect interactions are discussed.
The infrared optical properties of SiO2 and SiO2 layers on silicon
Authors: Philipp Herbert R.
Published: February 2003

The complex index of refraction N=n−ik for amorphous SiO2 is derived in the energy range 0.03–1.0 eV by Kramers-Kronig analysis of reflectance data. The results are used to compute the transmission, reflectance, and absorptivity of thin layers of SiO2 on Si substrates in the vicinity of the 0.14-eV (9 μ) lattice absorption band of SiO2. The dependence of these quantities on the layer thickness and angle of incidence is discussed.
Saturation of Zn2SiO4 : Mn luminescence under intense vuv excitation
Authors: Mikoshiba Shigeo , Shirai Shoji , Shinada Shinichi , Fukushima Masakazu
Published: February 2003

Output luminescence of Zn2SiO4 : Mn phosphor saturates under intense vacuum ultraviolet radiation having a relatively high excitation duty ratio. The saturation is attributed to the depletion of activators at the ground level. This depletion originates from the long decay time constant of the phosphor. The saturation mechanism is explained analytically using a simple model, and the conditions for efficient phosphor excitation are derived.
On the relationship of light-output nonlinearities and light-output spikes in proton-bombarded stripe-geometry double-heterostructure (Al,Ga)As lasers
Authors: Dixon R. W. , Joyce W. B. , Miller R. C.
Published: February 2003

By using a fast photodetector and a simple spatial filtering technique, the relationship between the optical spike which frequently appears at the leading edge of a pulsed-GaAs-laser response and the optical nonlinearities called kinks has been investigated. It is suggested that the spike can be viewed consistently as a transition period during which the lasing mode distortion, which has been previously associated with kinks, occurs. It is the time taken for the kink to become established. During the spike, light emisson occurs with a spatial and angular intensity distribution consistent with the lasing which would be appropriate if the kink did not exist. It is shown that the experimental technique can also be used to investigate sustained laser optical-intensity oscillations (pulsations).
Overlap-integral analysis of surface-acoustic-wave harmonic generation
Authors: Normandin R. , Fukui M. , Stegeman G. I.
Published: February 2003

It is verified that the overlap-integral and total-field approaches to the analysis of harmonic generation of surface acoustic waves produce identical results.
Perpendicular magnetic anisotropy in sputtered GdCo films
Authors: Esho Sotaro
Published: February 2003

Strong perpendicular magnetic anisotropy has been observed in GdCo films deposited by zero-bias sputtering with an Ar-N2 gas. As the nitrogen partial pressure of the sputtering gas increases, the perpendicular anisotropy constant increases and the Co sublattice moment of the films becomes large. The saturation magnetization of the films shows a steep temperature dependence near the magnetic compensation temperature. A molecular field theory indicates that the steep temperature dependence arises from the change in the exchange constant for the Gd-Co interaction. The perpendicular anisotropy may result from the exchange constant change.
Wall oscillations in the presence of in-plane fields in magnetic bubble materials
Authors: MacNeal B. E. , Humphrey F. B.
Published: February 2003

Wall oscillations after an abrupt change in bias field are observed in parallel-stripe domains as a function of both the magnitude and direction of an external in-plane field. Two distinctly different types of oscillations are found. For small values of in-plane field (Hip<10 Oe) nonlinear oscillations are observed. The wall velocity is saturated, resulting in oscillations with a characteristic triangular shape. The saturation velocity varies from 6.8 m/sec with Hip=0 to 12 m/sec with Hip=10 Oe. The half-period of the oscillations, τ/2, increases with increasing bias pulse amplitude Ha from τ/2=50 nsec with Ha=2.0 Oe, to τ/2=140 nsec with Ha=6.0 Oe. Increases in the angle β between the in-plane field and the domain walls cause increases in τ/2. For larger values of the in-plane field (Hip≳30 Oe) linear oscillations are observed, in which the wall velocity changes with the instantaneous drive field Hextz, resulting in sinusoidal oscillations. The frequency of the oscillations, ν, increases with increasing Hip, typically over the range 18<ν<35 MHz for 40<Hip<160 Oe. For a fixed value of Hip, ν decreases with increasing β typically over the range 23≳ν≳16 MHz for 0°<β<80°. The frequency is independent of Ha over the range investigated (2<Ha<6 Oe). In the transition region between linear and nonlinear oscillations (10<Hip<30 Oe) τ/2 gradually decreases and becomes less dependent on Ha. Linear wall oscillations are successfully modeled by assuming a one-dimensional dynamic wall structure. Through comparisons with experimental results, it is shown that (1) the instantaneous wall velocity ? obeys the classic mobility relationship ?=γΔ0Hextz/α; (2) the intrinsic wall mass density is given by the Döring mass, (2πγ2Δ0)−1; and (3) the losses associated with wall motion are consistent with the FMR loss parameter.
Azimuthal angular rotation (ψ̄̇) in domain walls during radial motion of bubble domains
Authors: MacNeal B. E. , Humphrey F. B.
Published: February 2003

Changes in bubble chirality are investigated using transient photography in order to determine the rotation of the azimuthal angle, either ψ or ψ̄̇, during radial motion. The critical rotation required to change chirality is determined experimentally to be near ψ̄̇=π. The Walker model, which predicts a critical rotation of π/2, cannot be used to describe radial motion. Instead, the horizontal Bloch line model, in which chirality changes occur during HBL punch-through when ψ̄̇ reaches nπ, must be used. The first seven values of the minimum step amplitude, Hn, required to produce exactly n chirality changes during a single bias step are given, within ±0.2 Oe, by Hn=[2vsH′ (γ)−1]1/2(nπ)1/2+Hs, where vs is the constant wall velocity, H′, is an effective field gradient, and Hs is an effective drag field. A 30-nsec pause in the wall motion, observed when ψ̄̇ reaches π, is thought to be due to the large effective gyrotropic field produced during punch-through. Contrary to the HBL stacking mechanism, punch-through occurs each time the HBL reaches the film surfaces, so that the low-frequency oscillations and heavy wall masses observed during radial motion result from the presence of a single HBL. If the effective drive field is small when the HBL reaches the film surface, punch-through can occur nonuniformly around the bubble perimeter, resulting in a 0.8-μm random translation of the bubble.
XPS and Mössbauer studies of amorphous FeGe
Authors: Terzieff Peter , Lee Kenneth , Heiman Neil
Published: February 2003

Photoemission spectra of amorphous FexGe1−x thin films prepared by thermal evaporation have been studied in situ with a XPS/Auger spectrometer. The composition varied within the range of 0⩽x⩽0.76 and the degree of surface contamination was monitored by Auger spectroscopy. The binding energies of Ge 3p and 3d as well as the Fe 3p transitions were found to be essentially independent of the alloy composition. Furthermore, no significant difference between the spectra of the alloys and the pure metallic elements could be detected. The results on a crystalline β-FeGe film (∼Fe3Ge2) were close to the data obtained on amorphous films. Mössbauer spectroscopy measurements down to 4.2 K performed on Fe0.53Ge0.47 indicated a mixed magnetic state composed of a nonmagnetically ordered doublet and a magnetically ordered broad six-line contribution, whereas the spectra of Fe0.30Ge0.70 showed only a nonmagnetically ordered doublet. By combining our results with published data, we are lead to the conclusion that a charge transfer model is not applicable to these alloys.
Domain-wall transitions in magnetic bubble garnet films
Authors: Maartense I. , Searle C. W.
Published: February 2003

In-plane ac susceptibility measurements on bubble film garnets containing stripe domains reveal sharp events which are interpreted as the formation and annihilation of horizontal Bloch lines. By etching the film it is found that the critical field for these events varies inversely with film thickness, as expected. Metastable wall structure changes are caused by in-plane fields above (6–8) Ms.
Comparative study of chemical and polarization characteristics of Pd/Si and Pd/SiOx/Si Schottky-barrier-type devices
Authors: Tongson L. L. , Knox B. E. , Sullivan T. E. , Fonash S. J.
Published: February 2003

The chemical nature of semitransparent (∼125 Å) palladium on silicon Schottky-barrier-type devices was determined by complementary AES and ISS techniques. Postdeposition analyses of metal-semiconductor (MS) and metal–thin-insulator–semiconductor (MIS) devices prepared without heat treatment showed that palladium silicide is formed in the MS structures, while the presence of an ultrathin (∼30 Å) purposefully grown semiconductor oxide film inhibits the chemical reaction between Pd and Si in the metal overlayer. Chemical bonding information extracted from the AES data was correlated with barrier-height measurements obtained from capacitance-vs-voltage (C-V) and current-vs-voltage (I-V) electrical characteristics of these devices.
Negative surface ionization hysteresis phenomena
Authors: Pelletier J. , Pomot C.
Published: February 2003

For negative surface ionization, expressions similar to those for positive ions are obtained for the relationship between the ionic current and the input flux, and the temperature and the electric accelerating field, assuming a linear variation of the desorption heats for negative ions and atoms with the degree of coverage of the ionizer surface. The theoretical study of hysteresis phenomena is qualitatively confirmed by experiments involving surface ionization of iodine atoms on polycrystalline lanthanum hexaboride. An estimate is given for iodine negative-ion desorption heat on lanthanum hexaboride.
Electron transport and breakdown in SiO2
Authors: Ferry D. K.
Published: February 2003

The transport of electrons at high electric fields in SiO2 has been calculated using an iterative solution of the path-variable formulation of the Boltzmann transport equation. Scattering due to the polar-optical modes and acoustic modes of the lattice are included. It is found that both the 0.153- and 0.063-eV polar-optical modes are important for scattering electrons. The electron velocity ’’saturates’’ near 1.9×107 V/cm for fields below 5×106 V/cm. The calculated curves are in excellent agreement with experimental data and indicate a best estimate of the polaron-corrected conductivity mass of 1.3m0. Above 5×106 V/cm, the electric field induced modifications of the carrier scattering rates cause the velocity to rise sharply. Time-resolved polar runaway is observed with an absolute threshold in the field range of (7–8) ×106 V/cm, with the runaway field increasing for short times, as may be appropriate for transport through thin oxides. Impact ionization is governed by the polar runaway, and carrier generation is observed at fields corresponding to the threshold for polar runaway.
Energy loss and escape depth of hot electrons from shallow p-n junctions in silicon
Authors: Shahriary I. , Schwank J. R. , Allen F. G.
Published: February 2003

The emission of electrons from a reverse-biassed p-n located below and parallel to an n-type emitting surface has been investigated experimentally. By sputter thinning the n layer, followed by annealing and CS-O treatments all in vacuum, we have been able to measure the energy distributions of emitted electrons at several different n-layer thicknesses, allowing direct application of a theoretical treatment due to Baraff. The surface barrier of ∼1.1 eV enables us to sample electrons having an average energy of about 3.0 eV above the conduction-band minimum. At these energies, considerably below those studied by most others, we find the mean free path for optical phonon emission, Lp, to be 141 Å, for ionization, Li, to be 8526 Å, and the total attenuation length, Lo, to be 359 Å.
Behavior of Au/InP Schottky diodes under heat treatment
Authors: Szydlo N. , Olivier J.
Published: February 2003

Variations of barrier heights with heat treatment are observed on Au/(n-type) InP Schottky diodes. The n-type InP wafers used are vapor epitaxially grown ({100} face oriented) and have carrier concentrations in the range 4×1015 to 2×1016 cm−3. Before the deposition of the metal, the surfaces are chemically etched in a bromine-methanol mixture. Electrical characteristics are reported as a function of isochronous heating cycles from 120 to 340 °C, using conventional Schottky barrier I-V and C-V analysis. The barrier heights are in the range 0.42–0.49 eV. Degradation characteristics and decreased barrier heights are observed after a 340 °C heat treatment in N2 with a residual O2 atmosphere. Distribution profiles of elemental species obtained by Auger electron spectroscopy associated with an Ar+-ion-beam sputtering show the interdiffusion between the metal and InP as a function of the heat treatment: out-diffusion of In and O as a solid solution of In2O3 in the Au film and Au and O diffusion through the Au/InP interface at 340 °C.
Laser generation of high-amplitude stress waves in materials
Authors: Fairand B. P. , Clauer A. H.
Published: February 2003

Stress-wave environments generated at a confined surface by a pulsed laser were investigated. Experimental measurements and theoretical calculations demonstrated that confinement of the surface with a transparent overlay provided an effective method of generating high-amplitude laser-induced stress waves in the target material. Peak pressures aproaching 10 GPa were possible at laser power densities of several times 109 W/cm2 for laser pulse durations ranging from several nanoseconds to several tens of nanoseconds. These pressures were generated in an air environment at standard conditions, thus enhancing their practical utilization for processing of materials and measurments of material properties. At laser power densities greater than 109 W/cm2, the laser-induced stress-wave environment was controlled by properties of the ionized plasma created near the metal surface. Some enhancement in the amplitude and duration of laser-induced stress-wave environments was observed at laser power densities less than 109 W/cm2 if low thermal conductivity and low heat of vaporization materials were used. Calculations show that peak pressures greater than 10 GPa were possible by superimposing stress waves either through reflection off a high acoustic impedance barrier or through the interaction of stress waves which were generated at different surfaces of a material.
Analytic solution for radiation-induced charging and discharging of dielectrics
Authors: Gross Bernhard , Leal Ferreira G. F.
Published: February 2003

Irradiation of a solid dielectric by ionizing radiation generates a radiation-induced conductivity. It allows one to remove or neutralize an macroscopic space-charge distribution that might have existed in the dielectric prior to the onset of irradiation. If irradiation is performed with charged particles, in particular electrons, transient charging currents are observed. The differential equation describing these effects is linear if the macroscopic space-charge drift term is neglected. This paper gives an analytic solution of this equation based on the general theory of linear passive relaxation systems. General aspects of the current observed during irradiation with partially penetrating electrons are discussed for different conductivity-depth profiles.
Calculation of short-pulse propagation in a large CO2-laser amplifier
Authors: Volkin Howard C.
Published: February 2003

Calculations are compared with measurements of nanosecond pulses propagating through a large CO2-laser amplifier system. Both coherence of medium polarization and rotational relaxation are included in the traveling-wave equations describing pulse propagation in an amplifying or absorbing medium. The basic formalism is derived and adapted to a model of the LASL two-beam system. Excellent agreement between the calculated and the measured output pulse shape and energy extraction is found. No adjustable parameters influence these calculations since all physical parameters used, as well as the input pulse itself, are derived from measured quantities.
Performance and diagnostic measurements of a supersonic HCl chemical laser
Authors: Arnold S. J. , Foster K. D. , Snelling D. R.
Published: February 2003

A supersonic purely chemical continuous-wave HCl laser is described in which nonequilibrium concentrations of atomic chlorine are generated by the branch-chain reaction of NO with ClO2. The ClO2 is injected into a stream of NO in helium immediately upstream of the throat of a slit nozzle. The reacting gases then expand as a free jet into a low-pressure region where HI is added to rapidly form vibrationally excited HCl. A maximum HCl multiline output power of 35 W is obtained, which represents a chemical efficiency of ∼4.5% based on the total exothermicity of the pumping reaction and the limiting flow rate of HI. An efficient technique for visualizing the flow in the expanded region is described. This technique is based on the visible chemiluminescence resulting from the addition of H2S to the NO/ClO2 reaction system.