bluuebunny/crossref_metadata_2025 huggingface dataset:
Fermi surface study of CeSb
Authors: Aoki H. , Crabtree G.W. , Joss W. , Hulliger F.
Published: July 2002

A Fermi surface study of the ferromagnetic phase of CeSb is presented. The γ frequency branches arising from the electron surfaces at the X points, three separate frequency branches from the hole surfaces at the Γ point, and the low-frequency branch α have been observed. The effective mass ratios are low and range from ∼0.2 for the α branch to ∼1.0 for the high-frequency branch of γ. The low effective mass ratios suggest that the admixture of the conduction states with the f state is small. We have observed a drastic change in the appearance of the de Haas–van Alpen signal at the phase transition between the ferromagnetic and lower field antiferromagnetic phases: the low-frequency α oscillation suddenly disappears as the crystal enters the antiferromagnetic phase. By utilizing the change in the signal appearance, the transition field strength has been measured as a function of the field direction. The present experimental results particularly the origin of the α oscillation, are discussed in the light of the p-f mixing theory and recent band-structure calculations based on localized f orbitals.
Numerical simulation of positive-potential conductors in the presence of a plasma and a secondary-emitting dielectric
Authors: Kessel R. L. , Murray R. A. , Hetzel R. , Armstrong T. P.
Published: July 2002

A 2 (1)/(2) -dimensional, cylindrically symmetric particle in cell program is used to simulate the interaction of a plasma with a positively biased disk covered by a dielectric material (Kapton). Several runs using different combinations of bias voltages and secondary electron yields are discussed. Special attention is paid to the role of the secondaries as the dielectric surface changes from a negative potential to become increasingly positive. This is termed the ‘‘snapover’’ process. The contribution due to secondaries is examined by plotting the distribution (number versus position) of the particles emitted by the impacting on the dielectric. These plots show that secondaries are drawn back into the dielectric as well as the conductor in the case of snapover. Mechanisms and experimental implications for these particular distributions are discussed.
Properties of Al/p-CdTe Schottky barriers
Authors: Chu T. L. , Chu Shirley S. , Ang S. T.
Published: July 2002

Al/p-CdTe Schottky barriers diodes were prepared from the Te (1̄1̄1̄) face of lightly doped p-type CdTe single crystals. The characteristics of the diodes have been found to depend strongly on the surface preparation of CdTe. The current-voltage characteristics of diodes prepared from Br2-CH3OH etched surfaces are dominated by the tunneling mechanism with high saturation current densities. The use of Br2-CH3OH etch followed by heating in hydrogen has pronounced effects on the diode quality factor and saturation current densities due to the restoration of the surface stoichiometry. The C-V measurements at 1 and 10 MHz indicate that Schottky diodes prepared from Br2-CH3OH etched and 450 °C hydrogen-annealed CdTe have a barrier height of 0.76 V and that diodes prepared from Br2-CH3OH etched or lower-temperature hydrogen-annealed CdTe show larger barrier heights. In latter cases, the barrier height appears to be controlled by the metal-semiconductor interface states. In Al/p-CdTe Schottky barriers with low interface state density, the temperature dependence of the saturation current density suggests that diffusion is the dominant mechanism of current transport, due presumably to the low carrier density in CdTe.
Unloading behavior of dislocations emitted from a crack
Authors: Zhao Rui-Huan , Li J. C. M.
Published: July 2002

Upon unloading, dislocations emitted from a crack can be retracted partially (stationary crack with lattice friction for dislocation motion) or completely (moving crack or zero friction for dislocation motion). The behavior of the plastic zone, the dislocation distribution, and the dislocation-free zone during the retraction process are studied by computer simulation. A propagating crack always moves forward upon unloading until all the dislocations are retracted. Its speed could be much faster during retraction than during the emission of dislocations. The rate of dislocation retraction or crack motion is slow in the beginning but then suddenly the crack jumps forward to retract all the rest of dislocations. This incubation period before the sudden crack surge seems to depend on the size of the dislocation-free zone.
A comparison between thermal annealing and ion mixing of alloyed Ni-W films on Si. I
Authors: Pai C. S. , Lau S. S. , Poker D. B. , Hung L. S.
Published: July 2002

The reactions between Ni-W alloys and Si〈100〉 substrates induced by thermal annealing and ion mixing were investigated and compared. Samples were prepared by sputtering of Ni-W alloys, both Ni-rich and W-rich, onto the Si〈100〉 substrates, and followed by either furnace annealing (200–900 °C) or ion mixing (2×1015– 4×1016 86Kr+ ions/cm2). The reactions were analyzed by Rutherford backscattering and x-ray diffraction (Read camera). In general, thermal annealing and ion mixing lead to similar reactions. Phase separation between Ni and W with Ni silicides formed next to the Si substrate and W silicide formed on the surface was observed for both Ni-rich and W-rich samples under thermal annealing. Phase separation was also observed for Ni-rich samples under ion mixing; however, a Ni-W-Si ternary compound was possibly formed for ion-mixed W-rich samples. These reactions were rationalized in terms of the mobilities of various atoms and the energetics of the systems.
Comparison of high-field stress effects in metal-oxide-semiconductor structures with aluminum and polycrystalline silicon gates using internal photoemission measurements
Authors: Heyns M. M. , De Keersmaecker R. F.
Published: July 2002

The effects of high-field stressing (9–10 MV/cm) with positive gate voltage on charges and defects in the SiO2 layer of metal-oxide-semiconductor structures are reported. In Al-gate devices negative charge builds up near the Si-SiO2 interface whereas positive charge is generated near the Al-SiO2 interface. Subsequent avalanche injection of electrons into the oxide does not annihilate the positive charge but the negative charge disappears. Similar studies were performed on polycrystalline silicon gate devices for which internal photoemission (photo I-V) measurements are reported for the first time. In this case a negative charge distribution is observed near both SiO2 interfaces after a positive stress and additional electron traps are created near the noninjecting polycrystalline silicon/SiO2 interface. Similarly, a negative stress for a polycrystalline silicon gate device creates electron traps near the substrate Si-SiO2 interface, as reported previously for Al-gate devices.
Precipitate morphologies in heat-treated Czochralski silicon crystals
Authors: Tsai H. L.
Published: July 2002

Three types of oxygen precipitate morphologies at 1050 °C have been identified to be plate-type, pyramidal, and polyhedral. This study was carried out using a set of slices with the same initial oxygen concentration but varying carbon concentrations. The morphology is shown to depend on carbon concentration and heat treatment. It is demonstrated that increasing carbon concentration tends to change the morphology from the plate to polyhedra and enhance the nucleation rate at low temperatures.
A calibration curve for room-temperature resistivity versus donor atom concentration in Si:As
Authors: Newman P. F. , Hirsch M. J. , Holcomb D. F.
Published: July 2002

Neutron activation measurements of arsenic concentration have been made on a set of samples cut from melt-grown crystals of Si:As in the concentration range from 7.8×1018 cm−3 to 1.1×1019 cm−3. Measurements of electrical resistivity at room temperature on the same samples provide information for a calibration curve of resistivity ρ versus the donor concentration nD. The data are combined with earlier measurements of ρ and nD made by Backenstoss using radioactive tracer techniques at lower As concentration to yield a calibration curve covering the donor concentration range from 1.0×1018 cm−3 to 1.1×1019 cm−3. A fourth-order polynomial expression for the function ρ vs nD is compared with data derived from Hall constant determinations of donor concentration. Using the expression relating the Hall constant to the electron density, RH=A(nD)/ne, we are able to obtain values of the function A(nD) for arsenic concentrations in the range 3.0×1018 cm−3 to 8.6×1018 cm−3. These values for Si:As are compared to the A(nD) values for Si:P.
The doping concentration dependence of the zinc acceptor ionization energy in In0.49Ga0.51P
Authors: Chang C. Y. , Wu M. C. , Su Y. K. , Nee C. Y. , Cheng K. Y.
Published: July 2002

The doping concentration dependence of the zinc acceptor energy level in In0.49Ga0.51P has been studied and can be expressed as EA=45.75−8.20×10−6 P1/3 meV, where P is the zinc acceptor concentration in cm−3. The zinc-doped In0.49Ga0.51P epitaxial layers were grown on 〈100〉 oriented semi-insulating GaAs substrates which are in very good crystallinity with a lattice mismatch of only 0.26%.
Measurement of the amplified spontaneous emission loss in an iodine photodissociation laser amplifier
Authors: Hahn Jae Won , Lee Sang Soo
Published: July 2002

The directional amplified spontaneous emission (ASE) along the laser tube of an iodine photodissociation laser (IPL) amplifier is measured and the experimental results are compared with the one-dimensional ASE theory. Also, we have measured the loss of the stored energy in the IPL amplifier due to the omnidirectional ASE. The loss is found to be 13.5% for the present amplifier when the laser medium i-C3F7I is 72 Torr and no argon buffer gas is added. But by adding the argon buffer gas to 210 Torr, it is reduced to 4.2%.
Statistical procedure for deconvoluting experimental data
Authors: Hiragi Yuzuru , Urakawa Hiroshi , Tanabe Kunio
Published: July 2002

A general procedure of the deconvolution of noisy experimental data is proposed. The deconvoluted solution is represented in terms of a cubic spline function f(x) with variable knots. The value of parameters and the location of knot points in the spline are determined by solving the nonlinear least-squares problem of fitting g(x)=∫κ(τ)f(s(τ,x))dτ to the data, where experimental data g(x) represent the convolution of f[s(τ,x)] with an apparatus weighting function k(τ) and s(τ,x) is a function related to the configuration of the experimental system. The profile of the fitted solution varies widely with different choices of the number and position of knots in the spline. To obtain a good solution, the optimum number of knots is determined based on the data by applying minimum Akaike’s Information Criterion procedure. Practical application of the variable-knot spline is generally considered to be rather intricate. However, by taking advantage of an advanced technique of a quasi-Newton method, the nonlinear least-squares problem becomes tractable, and excellent smoothing in the deconvoluted solution can be achieved.
On the nonequilibrium capacitance of the Schottky diode
Authors: Gildenblat Gennady , Cohen Simon S.
Published: July 2002

A general type of the boundary condition given by Simmons and Taylor is used to derive the expression for the nonequilibrium capacitance of the Schottky diode. It is shown that the deviation of the capacitance from its quasi-equilibrium value is larger than has been previously reported. Except for the extremely strong forward biases the quasi-equilibrium capacitance remains a valid approximation.
Diffusion theory of the low-pressure positive column with two-step ionization from a metastable state. II. Approximate analytical solutions for planar geometry
Authors: Romeiras F. J. , Ferreira C. M.
Published: July 2002

We present two approximate analytical solutions of the boundary value problem that models the low-pressure positive column with two-step ionization from a metastable state in the case of planar geometry and compare them with the numerical results of Part I.
Cavity supermodes for gain-saturated diode laser arrays
Authors: Hadley G. Ronald
Published: July 2002

We present a numerical method for the solution of the cavity modes of a multichannel array of laser diodes. The analysis is based on coupled-mode theory and includes the appropriate boundary conditions for the electric field at each reflecting facet. Saturable gain is also included, with saturation arising from both the forward-going and reflected waves. We present results which differ from a recent analytic analysis for the case of two channels with different gains and propagation constants. The present work predicts ‘‘cavity supermodes’’ which are similar to the ‘‘symmetric’’ and ‘‘antisymmetric’’ waveguide supermodes previously described in the literature. These cavity modes are characterized by equal intensities in both channels even when the channel gains are grossly different.
Computer simulation of electron beams. I. Space-charge algorithm for asymmetric beams
Authors: de Wolf D. A.
Published: July 2002

Longitudinal space-charge forces can be neglected in computer simulations of slowly curving quasilaminar electron beams. A particle-mesh-type algorithm for transverse space-charge forces is developed, and great simplification in numerical calculation of asymmetric electron beams is demonstrated. Some typical examples for kinescope beams are discussed.
X-ray study of low-temperature annealed arsenic-implanted silicon
Authors: Nemiroff M. , Speriosu V. S.
Published: July 2002

Low-temperature anneals (500–650 °C) of 2, 4, and 8×1015 cm−2 As+ implanted in 〈100〉 silicon at 50 keV were studied by x-ray double crystal diffraction. The rocking curves were analyzed by a kinematical model. Two regions of strain were found in the solid-phase epitaxially regrown layer. One layer was uniform and positively strained. The other was nonuniform and negatively strained. By comparing rocking curves of repeatedly etched layers it was found that the surface layer is negatively strained, corresponding largely to the substitutional As in the regrown layer. The positively strained region lies at the interface between the implanted layer and the undamaged silicon substrate.
Thermal annealing study on GaAs encapsulated by plasma-enhanced chemical-vapor-deposited SiOxNy
Authors: Chan Y. J. , Lin M. S. , Chen T. P.
Published: July 2002

To avoid the thermal decomposition of the GaAs surface during the postimplanted annealing, a silicon oxynitride (SiOxNy) encapsulate layer grown by plasma-enhanced chemical vapor deposition has been systematically studied. SiOxNy with the refraction index of 1.7–1.8 exhibited the best encapsulated performance after high-temperature annealing. Using Raman spectroscopy, etch-pit densities, photoluminescence, and Hall-effect measurements, this composition of the encapsulate layer on GaAs possessed the lowest surface defect, the best thermal stability, and the highest electrical activity of the implanted dopant. Thermal conversion is present when SiO- and SiN- rich films are used and is tentatively attributed to the generation of Ga vacancies during the annealing process.
Kinetics of interfacial motion and bubble movement by vapor transport for a two-component solid solution
Authors: Nichols F. A.
Published: July 2002

The movement of solid-vapor interfaces through transport in the vapor phase has been analyzed by various authors for the case of a single component. When two components exist, the vapor contains more than one species. Such a case has often been analyzed using the total vapor pressure for such systems. We present here an analysis, allowing for preferential evaporation of one species and consequent surface enrichment of the less-volatile species. This leads to a velocity of motion of the form 1/V=1/VA+1/VB, where VA and VB represent fictional velocities obtaining if only one species is rate controlling. Comparisons are made with some available data on congruently vaporizing compositions of mixed oxides and on the movement of lenticular voids in mixed oxides along thermal gradients, with very reasonable agreements obtained.
Transmission electron microscopy of electron-beam-evaporated arsenic trisulfide films
Authors: Singh Amarjit
Published: July 2002

Transmission electron microscopy in conjunction with x-ray photoelectron spectroscopy (XPS) was used to study the possible microstructural changes occurring in electron-beam-evaporated arsenic trisulfide thin films, when deposited on a sodium chloride substrate from room temperature to 250 °C. These films were found to be amorphous up to 150 °C, while a transition from the amorphous to the polycrystalline phase was observed to take place at 200 °C. The electron-diffraction results showed that the crystallized sulfur-rich phase was predominantly As2S5, along with As2S3. The XPS spectrum showed shifts in binding energy values for As towards higher energies. A shift of 0.9 eV for the As (3d) spectrum was attributed to the transition from the As2S3 to the As2S5 phase occurring at ∼200 °C.
Low threshold current density of GaInAsP visible injection laser diodes lattice matched with (100) GaAs emitting at 705 nm
Authors: Kawanishi Hideo , Tsuchiya Naofumi
Published: July 2002

The shortest possible lasing wavelength and the lowest threshold current density of the GaInAsP visible injection laser diodes grown on (100) GaAs substrate by the liquid phase epitaxy using a two-phase solution growth technique are discussed. The lasing wavelength and threshold current density at room temperature under pulsed conditions are 705 nm and 9.4 kA/cm2, respectively. Light output power of 5–6 mW from one facet and maximum differential quantum efficiency of 38% are realized under the condition of fundamental lateral and transverse mode operation.
Effect of image charges on impurity scattering of two-dimensional electron gas in AlGaAs/GaAs
Authors: Grinberg A. A. , Shur M. S.
Published: July 2002

The theory of impurity scattering of electrons in the two-dimensional electron gas in (Al,Ga) As-GaAs modulation doped structures is modified to include the effects of image charges in the neutral doped AlGaAs layer. The effect of the finite width of the electron wave function in the two-dimensional gas is also included. Our model calculation shows that impurity scattering is substantially diminished by the image charges in the doped AlGaAs layer. In samples with large thicknesses of an undoped AlGaAs spacer layer, the mobility of the two-dimensional gas at low temperatures may be limited by compensated ionized impurities in the undoped spacer layer.
Optical measurement of the photorefractive parameters of Bi12SiO20
Authors: Mullen R. A. , Hellwarth R. W.
Published: July 2002

We employ an optical technique requiring no electrodes to measure three parameters characterizing photorefractive traps in nominally undoped n-type bismuth silicate at 515- and 488-nm wavelengths. These parameters are (1) an effective density of active electron trap sites (∼1016 cm−3), (2) the contribution αpcm−1 of the photorefractive excitations to the total absorption coefficient (∼3.8 cm−1 or 54% at 488 nm and 1.4 cm−1 or 86% at 515 nm), and (3) the average distance over which an optically excited electron moves in the absence of electric fields before being retrapped (∼4 μm). With these parameters (and the crystal properties) standard models give predictions for all photorefractive effects, with or without applied electric fields and crystal motion, provided that there is negligible change in the density of occupied traps during an electron recombination time (∼microseconds). Our technique employs measurement of the light-induced exponential decays of spatial ‘‘gratings’’ of trapped charges as a function of the grating period. The expected three-parameter function is observed from which we determine the above three parameters.
Indirect heating of solid hydrogen with a moderately powered laser
Authors: Guttman J. L. , Turnbull R. J.
Published: July 2002

In this paper we describe experiments in which solid hydrogen is heated by laser-produced plasma. Motivation for this experiment is the possibility of producing large quantities of vibrationally excited hydrogen. (Vibrationally excited hydrogen is desirable for the production of H− ions by dissociative attachment.) A possible technique for formation of vibrationally excited hydrogen is heating it to 3000–5000 K in a dense enough state so that little dissociation takes place. The heated hydrogen is then allowed to expand and cool but because of a long relaxation time for deexcitation the vibrational excitation persists. A thin slab of solid hydrogen was mounted on a metal substrate, and laser light with power density 108–109 W/cm2 was used to heat the target. Because of the desired temperature the hydrogen could not be heated directly. (This would require much larger laser power which, in turn, would heat the hydrogen to much too high a temperature.) The laser light was absorbed by the metal substrate, and the resulting plasma transferred its energy to the solid hydrogen. Experimental results to determine resulting hydrogen temperatures are presented for different slab thicknesses. Diagnostics used included fast-framing and streak photography, Faraday cups, and a piezoelectric probe. A model is developed which allows the results to be explained. Hydrogen is ablated off the slab at the metal plasma surface, and the gas is heated by heat transfer. A shock wave is driven into the hydrogen. Then depending on the slab thickness one of two things occurs. For thin slabs we propose a Rayleigh-Taylor instability which causes the hydrogen to blow a hole in the solid (or liquid) and expand into vacuum. Under the right condition the expanded gas can then be used for H− production. If the slab is too thick, the shock wave becomes strong enough to produce vaporization. The resulting gas mixes with the heated gas, cooling it and preventing any large amount of vibrational excitation.
Energy and density measurements of sloshing ions in tandem-mirror-experiment upgrade using solid-state probe techniques
Authors: Hsu W. L. , Bastasz R. , Wampler W. R. , Rensink M. E. , Allen S. L. , Grubb D. P. , Simonen T. C.
Published: July 2002

The energy and flux of charge-exchange neutrals from the sloshing ions in the endplug of tandem-mirror-experiment upgrade were measured using solid-state probes. An average energy of the sloshing ions of 6 keV was inferred from the depth profile of deuterium implanted in a silicon sample exposed to the charge-exchange neutrals. A bounce-averaged Fokker–Planck code was used to calculate the sloshing-ion energy distribution. The calculated depth profile of deuterium in the silicon sample resulting from this energy distribution is in good agreement with the measured profile. Carbon resistance probes were used to measure the charge-exchange flux from which the central chord sloshing-ion line density was inferred. The line density of particles with energies>2 keV was deduced to account for 60% of the total plasma line density in the endplug. By folding the sloshing-ion line density into the diamagnetic loop data, it was shown that the 1/e radial extent of the sloshing ions remained relatively constant from shot to shot at 14 cm.
The far field in terms of the spatial Fourier transform of the sources and its implications on the inverse problem
Authors: Bojarski Norbert N.
Published: July 2002

It has been known for some time that the range and phase normalized far field is proportional to the three-dimensional spatial Fourier transform of the source distribution, taken on the surface of the Ewald sphere at a fixed frequency. Unfortunately, however, this very useful relationship is neither widely known, nor does there even exist for it a good, short, simple, and direct derivation in the open literature (thus making references to the relationship difficult). The purpose of this paper is to alleviate these difficulties by presenting a brief derivation of the relationship for both the scalar acoustic as well as the vector electromagnetic cases. A brief discussion of the implications of this relationship on the inverse source and inverse scattering problem is also presented.
Static stability of mercury mirror light modulators
Authors: Lea Michael C.
Published: July 2002

This paper analyzes the static stability of a mercury droplet held in a geometry consisting of two parallel gaps connected by a short tube. This arrangement finds application as a high-efficiency optical modulator which works in reflection, with the mercury surface acting as a mirror. Theoretical calculations of the pressure balance and the system energy are presented which lead to conclusions concerning the design of these devices.
Process-induced defects in solar cell silicon
Authors: Gleichmann R. , Cunningham B. , Ast D. G.
Published: July 2002

The microstructure of as-grown and processed, edge-defined film-fed grown, silicon ribbons was studied in order to identify the basic mechanisms responsible for the change of the as-grown defect structure during processing at elevated temperatures. The short heat treatment required to diffuse the p-n junction was sufficient to cause heterogeneous precipitation of impurity atoms, particularly transition metals. In addition, an elastic recovery of the ribbon occurred by dislocation glide, resulting in the formation of a polygonizationlike structure of sub boundaries in the base. Mechanism are suggested by which twin boundaries, acting as dislocation obstacles, can concentrate the relatively low average dislocation densities typical of edge-defined film-fed grown ribbons (104 cm−2 to 108 cm−2) to values which are sufficient to induce the formation of subgrainlike boundary structures.
Excimer laser-induced chemical vapor deposition of titanium silicide
Authors: Gupta A. , West G. A. , Beeson K. W.
Published: July 2002

A pulsed ArF excimer laser has been used to deposit thin conductive films of titanium silicide on silicon and silicon oxide substrates. The films are deposited from a gas mixture of titanium tetrachloride and silane by initiating photochemical reactions near the heated substrate. The resistivity, composition, crystal structure, and morphology of the films vary as a function of gas composition and substrate temperature. Films deposited at 400 °C, with SiH4/TiCl4 mole ratios of ∼2, have resistivities of 300 μΩ cm, which drop to 20–30 μΩ cm on annealing at 650–700 °C. At higher deposition temperatures (450–550 °C) the films have resistivities of ∼110 μΩ cm and show similar annealing behavior. The as-deposited films are a mixture of amorphous and a metastable Ti-Si crystalline phase. On annealing they convert to polycrystalline TiSi2. Films deposited at 400–450 °C are smooth and show conformal step coverage. The film roughness increases at higher deposition temperatures.
Comparison of the structure and electrical properties of thin tungsten films deposited by radio frequency sputtering and ion beam sputtering
Authors: Murray R.
Published: July 2002

Thin films of tungsten have been prepared by radio frequency (rf) diode sputtering and a saddle field ion beam source. The microstructure and electrical properties of the ion-beam sputtered films are comparable to those of rf sputtered films deposited at low-deposition rates. rf sputtered films deposited at high rates have larger grains and consist of β-W. They also have lower sheet resistances. An x-ray photoelectron spectroscopy analysis revealed that all of these films contained a considerable proportion of oxygen, the ion beam sputtered films containing more. Ion beam sputtering offers no advantages over low-rate rf sputtering of tungsten.
Efficiency of passive magnetic-confinement methods for rapidly rotating rings
Authors: Hull John R.
Published: July 2002

Rapidly rotating, large-diameter rings have potential for use as low-cost electrical-energy storage devices. The efficiency of passive electromagnetic and electrodynamic methods to confine the rotating rings is investigated. Confinement methods examined include repulsive image force, repulsive null flux, attractive image force, and radially stable attractive. For each method the decay time is given in terms of the ring material properties and design parameters. The repulsive techniques are shown to have decay times of less than a day when optimized within a set of practical design constraints. The two attractive levitation methods result in the largest decay times, but are inherently unstable. When null-flux stabilizers are used with attractive levitation, the decay time is shown to depend on magnetic field inhomogeneity. Finally, an inherently stable and very efficient attractive levitation method is proposed. The new method is based on an analogy with alternating-gradient synchrotrons and should have application in high-speed ground transportation.
Analysis of leakage current in silicon photoconductive switches
Authors: Koo Jackson C. , Pocha Michael D.
Published: July 2002

High-voltage silicon photoconductive switches require pulse bias in order to prevent thermal runaway. The behavior of these devices during pulse bias cannot be modeled by standard steady-state current equations (Ohm’s law). This paper shows that the observed nonlinear behavior is due to plasma injection, describes an analysis of this transient current flow during pulse bias, and shows it to be in good agreement with our experimental results. This paper further verifies the charge injection by showing that the leakage current can be reduced by thin trap layers directly underneath the metal contacts.
Evaluation of silicon films as a diffusion mask and encapsulant for InP and GaAs
Authors: Chin A. K. , Camlibel I. , Marchut L. , Singh S. , Van Uitert L. G. , Zydzik G. J.
Published: July 2002

We have determined that silicon films have nearly ideal properties for use as a diffusion mask and encapsulation coating for InP and GaAs. The Si films, composed of a single element, are easily and reproducibly deposited by electron beam evaporation at low temperatures. Sharp features can be defined by standard photolithography and freon-plasma etching. The thermal coefficient of expansion of silicon nearly matches that of InP and GaAs so that problems due to film stress are avoided. Additionally, the interaction of Si with InP and GaAs crystals, under severe thermal treatments often used in device fabrication, was found to be negligible. Finally, we found that the Si film acts as a good diffusion mask for Zn which is a common p-type impurity for forming p-n junctions in III-V compounds.
Interaction of relativistic electron beam with large-amplitude electromagnetic wave in a uniform magnetic field
Authors: Kuo S. P. , Schmidt G.
Published: July 2002

Resonant interaction of an electron beam with a relativistically strong electromagnetic wave of right-hand circular polarization propagating collinearly along a dc magnetic field B0 has been studied analytically. The analysis has taken the full nonlinearity of the relativistic effect into account. The result of the relativistic effect on the resonant interaction is to cause the wave intensity to oscillate at a frequency near (Ω0/2ω)1/2ωp/γ0. It is found that there is an upper bound on the transverse velocity of the electron achievable through the interaction.
Submicrometer-resolution etching of integrated circuit materials with laser-generated atomic fluorine
Authors: Loper G. L. , Tabat M. D.
Published: July 2002

We have demonstrated submicrometer-resolution lithography by ultraviolet laser-induced radical etching. We previously showed that this method can provide highly specific and efficient etching of various refractory metal/insulator and semiconductor/insulator substrate combinations.
Unreacted Hugoniot of Composition B-3 for stresses of 0–16 kbar
Authors: Lemar E. R. , Forbes J. W. , Watt J. W. , Elban W. L.
Published: July 2002

A light gas gun has been used to measure the unreacted Hugoniot of both pressed and cast Composition B-3. Transmitted stress and wave speeds were determined from quartz gauges placed on the rear surface of explosive disks. Both pressed and cast Composition B-3 exhibited elastic–plastic behavior. Good agreement was found between the elastic and plastic shock wave speeds and those determined ultrasonically. The elastic constants for pressed Composition B-3 were evaluated ultrasonically. Apparently, reaction in Composition B-3 has not occurred in the Hugoniot measurements described in this work.
Mobility and diffusivity for vacancy-solute diffusion in a simple cubic edge dislocation
Authors: Stark J. P.
Published: July 2002

An edge dislocation in a simple cubic crystal is considered as the basis for a model for vacancy-induced transport. The Burgers vector for the dislocation is [01̄0], and a solute atom moves along the compressed region of the core by vacancy exchanges along the edge of the extra half plane of atoms. The length of the dislocation is carried to the limit of an infinite number of lattice sites. Consequently, when the vacancy is tightly bound to the dislocation, that limit of tight binding becomes exact. In the tight binding limit, the correlation factor goes to zero for self-diffusion as expected. With vacancy solute tight binding, this result is not altered. Vacancy-solute repulsion can override vacancy-dislocation attraction and change the limit. In the case of dislocation and solute binding to the vacancy, the diffusivity becomes indefinitely large due to the abundance of defects increasing the jump frequency at a rate faster than the correlation factor decreases it. The mobility for electromigration also shows unusual limits. When the solute and dislocation both bind the vacancy, the ratio of the mobility to diffusivity becomes indefinitely large. So long as there is large dislocation vacancy binding, the ratio remains large even with solute vacancy repulsion.
Molecular beam epitaxy of InSb (110)
Authors: Bosch A. J. , van Welzenis R. G. , Schannen O. F. Z.
Published: July 2002

Molecular beam homoepitaxy of InSb on the nonpolar (110) face is reported for the first time. Growth conditions and substrate preparation techniques are discussed. With an In beam flux of 3×1014 at./cm2 s a growth rate of 0.72 μm/h is obtained, hence the sticking coefficient of In on InSb (110) is one. Layers of good crystalline quality and of stoichiometric composition were grown at a substrate temperature of 380 °C and a flux ratio ΦSb/ΦIn=3. The ΦSb/ΦIn vs Ts diagram is given. Two surface reconstructions are reported: the well-known (1×1) at high Ts and a new reconstruction with (1×4) symmetry at lower Ts. The latter may be connected with InSb bond breaking or an In overlayer. The epilayers with thicknesses from 1 to 7.7 μm all show n-type conductance with mobilities from 1.2 to 7.5 m2/V s at 77 K. By optimizing the growth conditions with respect to the electrical transport properties much higher values should be attainable.
Transmission electron microscope observation of lattice image of AlxGa1−xAs-AlyGa1−yAs superlattices with high contrast
Authors: Suzuki Yoshifumi , Okamoto Hiroshi
Published: July 2002

High-resolution transmission electron microscope (TEM) observation is made on cross sections including the growth direction of MBE-grown AlxGa1−xAs-AlyGa1−yAs superlattice samples. Lattice images with contrast high enough to distinguish each of the constituent layers in superlattices are important for the study of heterointerfaces on an atomic scale, and two methods are developed in order to obtain them. One is to use superlattices with large difference Δx=y−x in Al composition. It is found that the degree of abruptness at the heterointerface is one or two monolayers and that the heterointerface of the ternary AlGaAs grown on the binary AlAs is smoother than that of the binary grown on the ternary. The other is to observe superlattices by using an electron beam incident along a [100] crystal axis. A theoretical consideration based on both kinematical and dynamical theory of diffraction is given, which suggests that, in obtaining lattice images with high contrast, an electron beam along a [100] crystal axis is more favorable than one incident along the [110] axis which is conventionally used. This is confirmed experimentally by using a GaAs-AlGaAs superlattice sample.
Slow-relaxation phenomena in photoconductivity for semi-insulating GaAs
Authors: Nojima S.
Published: July 2002

A new type of slow-relaxation phenomena is reported together with the conventional fatigue phenomenon in photoconductivity for undoped semi-insulating liquid-encapsulated Czochralski GaAs. First, conventional fatigue is induced by the ∼1.1-eV light irradiation (primary light). Secondary-light irradiation (∼0.8 eV) subsequently carried out is found to generate a rapid increase followed by a gradual exponential decrease in photoconductivity. The latter phenomenon shows very different characteristics from those of conventional fatigue, though the two phenomena are similar to each other. Through the detailed experimental studies, a configuration-coordinate model is presented, involving a main deep level X and its metastable excited state X* with large lattice relaxation. This phenomenon is explained by the transition of electrons which occurs in part from level X* excited by the preceding primary-light irradiation, via level X, to the conduction band as a result of secondary-light irradiation.
A study of hydrogenated amorphous silicon deposited by hot-wall glow discharge
Authors: Boulitrop F. , Proust N. , Magariño J. , Criton E. , Peray J. F. , Dupre M.
Published: July 2002

We report a study of a-Si:H films deposited in a hot-wall glow-discharge machine. Optical and transport properties were studied as a function of frequency (400 kHz and 13.56 MHz) and power of the radio frequency (rf), temperature and pressure during deposition, and they were found very similar to those of films deposited by other glow-discharge techniques. Thin films (<1 μm) have a higher defect density than thicker films. The lowest defect density and disorder are achieved in the 200–250 °C temperature range. Pressure and rf frequency have no effect on defect density and disorder but control the position of the Fermi level. Reversible defect creation is induced by long and intense light irradiation but this induces no shift of the Fermi level.
Two-dimensional continuum percolation and conduction. II
Authors: Nakamura Mitsunobu
Published: July 2002

By computer simulation we have been studying the relation between the effective conductivity and the geometrical configuration of two-dimensional composite or inhomogeneous materials consisting of a metal and an insulator, considering the problem as a continuum percolation problem. Following our previous paper [J. Appl. Phys. 56, 806 (1984)], we further simulate two new types of continuum percolation models, and compute the effective conductivities by the finite element method. We compare the calculated conductivities with previous results, theoretical formulas, and experimental data. We clearly show that the critical volume fractions for the metal-insulator transition and the conductivities of the continuum percolation problem greatly depend on the geometrical configuration of the metal areas of the formed patterns. The extended Watson–Leath equation is a good approximation to the conductivity of the two-dimensional continuum percolation problem.
Influence of rf power on the properties of hydrogenated amorphous silicon carbon alloy films prepared by magnetron sputtering of silicon in methane-argon gas mixtures
Authors: Saito Nobuo
Published: July 2002

The rf power dependence of structural, optical, electrical, and optoelectronic properties of hydrogenated amorphous silicon carbon alloy films prepared by magnetron sputtering of silicon in methane-argon gas mixtures has been investigated. With increasing rf power, the optical band gap and the activation energy of dark conductivity decrease, accompanied by a decrease in the concentration of Si-C bonds. The dark conductivity and the photoconductivity increase with increasing rf power. These results are discussed in terms of the compositional and structural change of the films with rf power, such as the factor of preferential attachment of hydrogen to carbon deduced from IR measurements, and the conduction-band tail width deduced from optical absorption spectra or from temperature dependence of photoconductivity.
Nonequilibrium thermostatics
Authors: Cory J. S. , McNichols J. L.
Published: July 2002

A self-consistent thermodynamics is developed for nonrelaxation hysteretic processes. This theory, nonequilibrium thermostatics, is based upon macroscopic empirical descriptions of hysteretic behavior and the laws of thermodynamics. It is shown that the empirical behavior of hysteretic systems does not satisfy the conditions required for application of either equilibrium or relaxation nonequilibrium thermodynamics. Therefore, modified thermodynamic assumptions are proposed which are consistent with empirical hysteretic behavior. The principal new assumptions are (1) that processes (energy dissipation permitted) consists of a differential sequence of nonequilibrium states; (2) that three new ‘‘state variables’’ describe all of the ‘‘history dependence of a state;’’ (3) that at least some ‘‘reversible’’ processes exist; (4) that the time-independent ‘‘modified Gibbs relation’’ can be used to describe the Second Law constraints. With these assumptions, it is shown that the thermodynamic relationships derived from the First Law are identical to those for standard equilibrium thermodynamics, but Second Law implications are significantly different, e.g., a new ‘‘dissipation’’ state function is derived; it is proven that hysteretic behavior is a positive indication of a dissipative process and that dissipation always causes hysteresis. It is concluded that nonequilibrium thermostatics provides a self-consistent theory which extends the useful domain of thermodynamics to include nonrelaxation, hysteretic (dissipative)processes. A comparison of detailed predictions and experimental measurements of heat capacities, adiabatic paths, etc., for a hysteretic system is provided in a separate paper.
Vacuum surface flashover from bipolar stress
Authors: Anderson R. A. , Tucker W. K.
Published: July 2002

A simple model is employed to explain the anomalous surface-flashover characteristics observed when insulators in vacuum are stressed with bipolar voltage waveforms. Under unipolar stress, the flashover field is found to vary as the inverse square root of the prebreakdown time delay over the first few tens of nanoseconds, thereafter becoming less dependent on delay. The short-delay behavior, according to our model, results from the accumulation of ionic charge adjacent to the insulator-vacuum interface. At longer delays ions are swept away nearly as rapidly as they are created. Flashover data from conventional insulator assemblies subjected to unipolar stress is consistent with ions being swept away. With the application of a roughly 10 MHz, bipolar voltage waveform a different behavior is observed. The holdoff is unexpectedly low and an anomalous inverse-square-root dependence on delay persists over hundreds of nanoseconds. Analysis of ion motion indicates that some fraction of the ions follow small-amplitude oscillatory trajectories and continue to accumulate for relatively long periods of time. An insulator has been modified to enhance ion removal by decreasing the thickness of polystyrene segments fourfold to 4.7 mm. A 50% improvement in performance is found, although the holdoff remains below standards applicable to unipolar stress.
Thermally activated peroxy radical dissociation and annealing in vitreous SiO2
Authors: Devine R. A. B. , Fiori C.
Published: July 2002

Isochronal and isothermal annealing results for peroxy radical defects induced in Suprasil W1 by γ irradiation are reported. The activation energy for annealing is estimated to be ∼2 eV and argued to be due to OO bond dissociation rather than gaseous interstitial or network diffusion. The results are shown to be consistent with those obtained from annealing/reactivation studies on oxygen vacancy defect centers.
Scattering matrix representation for the microwave Hall effect in the depolarization regime
Authors: Caverly Robert H.
Published: July 2002

Microwave Hall-effect measurements have proven invaluable for determining the Hall mobility in a wide variety of both organic and inorganic materials. Since some of these materials crystallize into needle shapes, the question of depolarization effects and the measurement and interpretation of the cavity-scattering parameters describing the microwave Hall effect have yet to be addressed. It will be shown in this paper that the microwave Hall mobility can be found under any polarization conditions by direct measurement of the cavity input and output reflection coefficients, as well as the cavity transmission factor. Experimental results supporting this premise are presented. In addition, the sign of the microwave Hall mobility is shown to be a function of the degree of sample polarization.
A study of the photovoltaic effect of a semiconductor grain boundary by a scanning laser beam
Authors: Song J. S. , Yang E. S.
Published: July 2002

Experimental observation of the photovoltaic effect of a semiconductor grain boundary with a scanning laser spot is analyzed assuming a single trap energy level. The current is calculated from the recombination velocity and the concentration of the minority carriers at the grain boundary which was derived from the continuity equation. The open-circuit voltage across the sample is obtained from equating this recombination current to the compensating current using the thermionic emission model. Using the recombination velocity and the diffusion length as variables, the calculated open-circuit voltage is compared with the experimental data.
Compensation in heavily doped n-type InP and GaAs
Authors: Anderson D. A. , Apsley N. , Davies P. , Giles P. L.
Published: July 2002

Hall data on vapor-phase-epitaxial InP doped with Si, S, Sn, and Se and liquid-encapsulated-Czochralski InP doped with Ge are presented for doping levels between 1015 and 1019 cm−3. The results show nearly identical electrical behavior for all n-type dopants but a consistent discrepancy with theoretical mobility calculations, particularly in the doping range 1017–1019 cm−3. A chemical analysis of the sulphur content in layers doped with sulphur shows that all the dopant is electrically active. The reason for the discrepancy with the calculation is discussed in terms of the description of ionized impurity scattering in the presence of a high density of ionized centers. We also emphasize the similarity with GaAs and suggest that our conclusions apply equally to both materials.
Spot reduction in electron guns using a selective prefocusing lens
Authors: van Gorkum Aart A. , van den Broek Maarten H. L. M.
Published: July 2002

In electron guns, three lenses are present: the cathode lens, projecting a crossover in front of it, the main lens that images the crossover on the target, and the prefocusing lens situated in between, adapting the aperture angle to the main lens. The spot size at the target is calculated for different positions and strengths of the prefocusing lens. The analysis is based on a phase space representation of the rotationally symmetric beam. It is shown that by proper choice of the position and strength of the prefocusing lens, the resulting selective prefocusing lens (SPL) reduces the combined spherical aberration of the cathode lens and main lens by 45%. The intensity distributions in the spot with and without the SPL differ greatly and a more uniform spot intensity is obtained.
Intense diffraction of a laser beam due to self-focusing in underdense plasma
Authors: Giulietti D. , Giulietti A. , Lucchesi M. , Vaselli M.
Published: July 2002

Intense laser light diffraction is observed from a low-density spark (ne≲nc/100) outside the focal cone up to an angle of 14°. About 10% of the laser pulse energy is spread by diffraction. Temporal and spatial features of this effect are discussed in terms of self-focusing and hydrodynamics plasma motion.