bluuebunny/crossref_metadata_2025 huggingface dataset:
Recrystallized Al-nSi Schottky barriers with a barrier height of 0.93 eV
Authors: Wu Chii-ming M. , Yang Edward S.
Published: February 2003

Using a silicon-aluminum-silicon sandwich structure obtained by evaporating thin aluminum and silicon films on a single-crystal silicon substrate, we have fabricated Al-nSi Schottky barriers with a maximum barrier height of 0.93 eV. The formation of the rectifying contact and its dependence on the Al-film thickness were studied by means of I-V and C-V measurements. It is found that the as-deposited films form an Ohmic contact with a n/n+ silicon substrate. However, we have obtained rectification characteristics by heat treatment at 600 °C (slightly above the Al-Si eutectic temperature) in a nitrogen or hydrogen environment. The barrier height increases with aluminum thickness (l) from 0.79 eV for l=500 Å and it saturates at 0.93 eV for l≳1500 Å. The uppermost silicon film (300 Å) is needed to prevent the formation of aluminum clusters under heat treatment. In completed diodes the surface silicon film is recrystallized and large polycrystalline-Si grains are seen under an optical microscope.
Magnetostatic energy of a ferromagnetic sphere
Authors: Aharoni Amikam
Published: February 2003

A general expression is given for the magnetostatic self-energy of a spherical particle, magnetized in any (nonhomogeneous) fashion. It can be used for any micromagnetic study with spherical symmetry, saving the tedious calculations that start from the potential of the particular problem. The expression includes, as particular cases, studies which can be found in the literature.
Arc augmented laser processing of materials
Authors: Steen William M.
Published: February 2003

It has recently been found that an electric arc can be added to the interaction between a laser beam and a material surface in such a way that in welding and cutting it produces an effect similar to that from a more powerful laser. The experimental results are discussed together with an analysis of the process mechanism. In particular it appears that the arc strikes the work piece at the same interaction zone as the laser, and in so doing undergoes a contraction in width to near the same size as the laser beam. It also seems probable that some of the arc energy penetrates the laser generated keyhole. So far the experimental results have shown that arc augmentation of the laser by some 2 kW of arc power in the work piece can be achieved without unduly spoiling the high quality of the cut or weld that would be made by a laser alone of similar total power.
Pulse shape effects in Raman compressors
Authors: Eimerl D.
Published: February 2003

The effects of the Stokes pulse shape, the finite Stokes pulse width, and the timing of the pump and Stokes pulses are examined in detail with regard to the performance limitation on Raman compressors arising from second Stokes production. It is shown that there is an optimal pulse shape for which the second Stokes gain is minimized. The end corrections, where the Stokes wave passes through the Raman medium but does not overlap the pump, are found to have a significant effect on performance. The compression achievable with optimal pulses, timing, and cell length appears to be up to twice that attainable with the Gaussian Stokes pulses considered previously.
Experimental verification of a Hertz vector model of light scattering by surface acoustic waves on LiNbO3
Authors: Lee J. , Wesolaski E. , Singh M. P. , Zucker J.
Published: February 2003

The experimental verifications of a Hertz vector model of light scattering by surface acoustic waves on Y-Z lithium niobate which was proposed by Stegeman are presented. The extension of the theory to a more general case in which the polarization state of the incident light is arbitrary is described and verified experimentally.
Highly temperature-dependent performance of a polyvinylidene fluoride Lamb wave device
Authors: Toda Kohji , Ikenohira Kazuo
Published: February 2003

A Lamb wave device using a polyvinylidene flouride film is described. The transducer of the device consists of interdigital electrodes and a uniform counter-electrode. The performance of the device is highly temperature dependent. The attenuation of the Lamb wave on the film increases with higher frequencies. The attenuation decreases with increasing temperature, while the conversion efficiency of the transducer is nearly constant for the temperature change. The output of the device changes significantly under the influence of irradiation from a black body, and the device is very sensitive in the infrared region.
Axial electron density and wave power distributions along a plasma column sustained by the propagation of a surface microwave
Authors: Glaude V. M. M. , Moisan M. , Pantel R. , Leprince P. , Marec J.
Published: February 2003

The propagation of electron surface waves can be used to sustain long plasma columns. The relation between the axial distribution of the electron density observed along the plasma column and the corresponding power distribution of the surface wave that produces it is investigated. It is found that the electron density decreases almost linearly along the plasma column in the direction of the wave propagation. This is explained by assuming that the number of electrons produced over a given axial length is proportional to the wave power absorbed over that same length.
Laser-target interaction near the plasma-formation threshold
Authors: Holmes Bayard S. , Maher W. E. , Hall R. B.
Published: February 2003

Surface pressures were measured on targets that were directly behind a laser-supported absorption wave. These waves occur at laser fluxes near the threshold flux for plasma formation and are associated with enhanced thermal and mechanical coupling to the target. The surface pressures within the laser spot were measured with carbon piezoresistive gauges while blast wave pressures away from the laser spot were measured with a quartz piezoelectric gauge. Comparison of the experimental data with current theories shows that peak pressures in the laser spot are significantly lower than predicted by the theories.
Phase transition waves: Solitons versus shock waves
Authors: Landauer Rolf
Published: February 2003

Multistable systems, extended in one spatial dimension, can make transitions from one state of local stability to another local state of stability, in a spatially uniform way, or by motion of an interface. The literature on Sine-Gordon and φ4 solitons, in nonlinear dipersive systems, emphasizes their role as phase boundaries of this sort. We emphasize that shock waves can also act as moving phase boundaries in multistable systems. Our analysis invokes ferroelectric transmission lines as the principal model, but also treats linear arrays of coupled bistable springs. The soliton causes a transition in a given local volume, passed by the disturbance, by directly controlling the multistable degree of freedom, whereas the shock wave controls the corresponding force.
Formation and destruction of molecular ions in a Townsend discharge in neon
Authors: Dielis J. W. H. , de Hoog F. J. , Schram D. C.
Published: February 2003

Production of molecular ions by termolecular association and by associative ionization as well as the destruction of these ions by collisional dissociation has been investigated experimentally in a low-current-density discharge in neon. Space-charge effects and all cumulative processes can be neglected so that a simple model of the discharge can be used. Measurements have been carried out by mass discriminated ion sampling through the cathode. The results show values of the product kr τ of the associative ionization rate and the unproductive lifetime ranging from (0.6 up to 1.9)×10−23 m3 at values of the reduced electric field strength E/N from 45 up to 245 Townsend. In the same range of E/N, values for the termolecular association rate kc appear to be in good agreement with previous studies and show a T−.05 temperature dependence. Finally in the same E/N range dissociation rates kd of Ne2+ ions increase from 3×10−19 to 3.5×10−17 m3s−1. These values are in excellent agreement with values calculated with a detailed balance argument from values for the termolecular association rate.
Dopant segregation in polycrystalline silicon
Authors: Mandurah Mohammad M. , Saraswat Krishna C. , Helms C. Robert , Kamins Theodore I.
Published: February 2003

Dopant segregation at grain boundaries in polycrystalline silicon has been investigated. Arsenic, phosphorus, and boron were ion implanted into low-pressure, chemically-vapor-deposited polycrystalline-silicon films. All films were then annealed at 1000 °C for 1 h, and some were subsequently further annealed at 800, 850, or 900 °C for 64, 24, or 12 h, respectively. For phosphorus and arsenic the room-temperature resistivity of the films was found to be higher after annealing at lower temperatures. By successively annealing the same sample at lower and higher temperatures, the resistivity would repeatedly increase and decrease, indicating reversible dopant segregation at the grain boundaries. Hall measurements were used to estimate the number of active dopant atoms within the grains and the number of atoms segregated at the grain boundaries as a function of annealing temperature. A theory of segregation in systems of small particles has been developed. Using this theory, the heat of segregation of arsenic and phosphorus in polycrystalline silicon was calculated. For boron no appreciable segregation was observed.
Cathodoluminescence studies of anomalous ion implantation defect introduction in lightly and heavily doped liquid phase epitaxial GaAs:Sn
Authors: Norris C. B. , Barnes C. E.
Published: February 2003

The anomalous postrange defect introduction produced by shallow ion implantation in GaAs has been investigated in Sn-doped liquid phase epitaxial (LPE) material using depth-resolved cathodoluminescence in conjunction with layer removal by chemical etching. 100-keV Ne+ or 200-keV Zn+ ions were implanted into lightly or heavily Sn-doped LPE layers at temperatures between 80 and 300 K. All implantations were subsequently annealed at 300 K. Although the projected ion ranges for the implants were on the order of 1000 Å, significant postrange damage was observed at far greater depths. At depths up to several microns, the damage introduction produced severe nonradiative recombination but simultaneously caused an apparent increase in the concentration of incumbent luminescence centers responsible for an extrinsic band near 1.39 eV. A weak damage-related band near 1.2 eV could also be seen in one instance. At depths of 5–30 μm, the postrange damage had the opposite effect of annihilating incumbent 1.39-eV luminescence centers. The efficiency of the damage introduction has a complicated temperature dependence which is significantly different for the ion/substrate combinations investigated. However, no conditions were found for which the damage introduction could be inhibited. While our measurements are the most extensive to date concerning the anomalous ion implant damage introduction in GaAs, the detailed mechanisms responsible for this effect still remain obscure owing in part to the limited understanding of defects in GaAs.
The operation of the semiconductor-insulator-semiconductor solar cell: Barrier height lowering through interface states
Authors: Spitzer M. , Shewchun J. , Burk D.
Published: February 2003

Previous studies have shown that the characteristics of the semiconductor-insulator-semiconductor (SIS) solar cell can be controlled by the thin interfacial layer. In this paper, we present the results of a theoretical investigation of the role of interface states at the SiO2-Si interface in the ITO-SiO2-Si SIS solar cell. A numerical solution of the governing transport equations yields the dependence of efficiency, short-circuit current, and open-circuit voltage on interface state density. It is shown theoretically that occupied acceptorlike interface state lower the barrier height and thus raise the dark saturation current while lowering the open-circuit voltage. Experimental results are presented which relate the saturation current to the process step which forms the interfacial layer and which support the model.
Vidicon target of a p-i-n structure using a-Si:H
Authors: Shimizu Isamu , Oda Shunri , Saito Keishi , Inoue Eiichi
Published: February 2003

A vidicon target of a p-i-n structure has been fabricated using amorphous silicon prepared by a rf glow discharge of silane (SiH4). A thin layer of n-type a-silicon doped with phosphorus was provided between a photosensitive layer and a substrate coated with a transparent electrode (SnO2:Sb) to prohibit injection of holes. An excellent photoresponse was attained for visible light.
Bias-dependent photoluminescence intensities in n-InP Schottky diodes
Authors: Ando Koushi , Yamamoto Akio , Yamaguchi Masafumi
Published: February 2003

A remarkable change of the photoluminescence (PL) intensity with the variation of the dc bias voltage is observed in Au/n-InP Schottky surface. It is found from the observation of the surface band bending that the PL intensity is dominantly affected by the surface space-charge layer. The maximum PL intensity is found to be attained at the flat-band bias condition.
Polar and nonpolar contributions to liquid-crystal orientations on substrates
Authors: Naemura Shohei
Published: February 2003

Both experimental and theoretical evidences are presented for polar and nonpolar contributions to liquid-crystal orientations on surface-treated substrates. Polar and nonpolar components of substrate surface energies are determined from contact angle measurements using polar liquids. Liquid-crystal orientations are characterized using orientation angles and anchoring strength coefficients at substrate surfaces, both of which are measured by the magneto-capacitance method. Numerical calculations give correlations between liquid-crystal orientation and substrate surface energy components, which are in good agreement with experimental results. These calculated correlations involve the critical surface tension hypothesis as a limited case when polar interfacial interactions are negligible.
Observation of the tin whisker by micro-Auger electron spectroscopy
Authors: Fujiwara Kenzo , Kawanaka Ryusuke
Published: February 2003

An observation by micro-Auger electron spectroscopy has been made of the tin whisker grown on electroplated tin films. Direct experimental evidence has been obtained for the existence of zinc and oxygen impurities on tin whiskers as well as on the electroplated film surfaces when a brass or zinc-coated metal is used as a substrate. The localization of these impurities on these surfaces may be related to the growth mechanism of tin whiskers or to the driving force by lowering the surface energy.
Chemical identification of deep energy levels in Si:Se
Authors: Grimmeiss H. G. , Janzén E. , Skarstam B. , Lodding A.
Published: February 2003

Profiles of deep energy states in selenium diffused silicon p+n junctions have been studied by junction capacitance techniques and secondary ion mass spectroscopy (SIMS). In both cases similar profiles are obtained. Since the profiles measured by SIMS are due to selenium atoms, it is concluded that selenium is responsible for the two dominant energy levels previously investigated in Si:Se by junction space-charge techniques.
Electrical and optical properties of undoped and antimony-doped tin oxide films
Authors: Shanthi E. , Dutta V. , Banerjee A. , Chopra K. L.
Published: February 2003

Tin oxide films have been prepared on glass substrates by spray pyrolysis technique. The electrical and optical properties of undoped and antimony-doped tin oxide films have been studied. The temperature dependence of electron mobility has been analyzed to establish the electron conduction mechanism. Optical properties near the plasma edge have been analyzed using Drude’s theory. The dependence of effective mass on carrier concentration has been explained on the basis of nonparabolicity of the conduction band. The shift in the Fermi energy, calculated on the basis of energy dependent effective mass, is consistent with the measured shift in the absorption edge.
Thermal generation of carriers in gold-doped silicon
Authors: Richou F. , Pelous G. , Lecrosnier D.
Published: February 2003

There is still considerable disagreement in the published values for the energy position and capture cross section of the gold-acceptor level in silicon. We have measured in a rather direct way the thermal emission rate en for electrons and ep for holes in the 240–360 °K temperature range on gold-contaminated MOS and Schottky structures. The results can be well explained by the single-level Shockley-Read-Hall model when pinning the gold level either to the conduction band or to the valence band. That is the reason why there are various interpretations while crude results for en and ep are in good agreement. For instance, depending on the case, the gold energy level is found to be 0.553 or 0.476 eV below the conduction band at 300 °K: these are the extreme published values. From a practical point of view, we show that at concentrations as low as 1010 cm−3, gold is the major impurity controlling the generation lifetime in silicon devices.
An alternative approach to charge transport in semiconducting electrodes
Authors: Thomchick John , Buoncristiani A. M.
Published: February 2003

We analyze the excess-carrier charge transport through the space-charge region of a semiconducting electrode using a technique known as the flux method. In this approach reflection and transmission coefficients appropriate for a sheet of uniform semiconducting material are used to describe the transport properties of that material. We give a brief review of the flux method and show that the results obtained using this approach for a semiconductor electrode reduce in a limiting case to those previously found by Gärtner if the depletion layer is treated as a perfectly transmitting medium in which scattering and recombination are ignored. Then, in the framework of the flux method we treat the depletion layer more realistically by explicitly taking into account scattering and recombination processes which occur in this region.
A study of oxide traps and interface states of the silicon-silicon dioxide interface
Authors: Stivers A. R. , Sah C. T.
Published: February 2003

Vacuum-ultraviolet light (10.2 eV) generated electrons or holes are injected into the oxide by dc biasing metal-oxide-semiconductor Al-SiO2 capacitors with 2800-Å (1000 and 1100 °C) dry oxides annealed in dry oxygen at 600 or 800 °C. The injected charges are trapped in the oxide. The trapped charge density is determined by the capacitance-voltage method and its location by the photocurrent-voltage method. The trapped-hole charge injected under positive dc bias was found to be within 100 Å of the oxide-silicon interface. Trapping kinetic data revealed two donorlike neutral hole traps with hole capture cross sections of 6×10−14 and 1×10−15 cm2. Both of these traps, after being positively charged by hole capture, were efficient electron traps with an electron-capture cross section of 3×10−13 cm2. An acceptorlike electron trap with an electron-capture cross section of 1×10−15 cm2 was also detected which anneals out during 800 °C anneal in dry oxygen. Little increase in the interface-state density was observed during the charge-injection and trapping experiments. Analyses of the annealing kinetics of these oxide traps suggest that the larger hole trap is an excess silicon center (trivalent silicon) and the smaller hole trap is an excess oxygen center (nonbridging oxygen).
Photoluminescence of Ge-doped AlxGa1−xAs grown by liquid phase epitaxy
Authors: Kaneko Kunio , Ayabe Masaaki
Published: February 2003

The photoluminescence of Ge-doped AlxGa1−xAs grown by liquid phase epitaxy (LPE) was investigated. The ionization energy of Ge, determined from the photoluminescence spectra, has a strong relation to the Al composition. This cannot be explained by a simple effective mass-like expression. The broad emission band with a peak at about 1.5 eV, which has been observed by several investigators, was studied further. The intensity of the emission band increased as Ge or as implanted O concentration increased. The peak energy shifted toward higher energy as excitation intensity increased. The paper suggests that this emission band is caused by O donor-Ge acceptor pair recombination.
Further investigation of the 1.4-eV luminescence in solution-grown CdTe:In
Authors: Norris C. B.
Published: February 2003

Previous attempts to understand the mechanism responsible for the 1.4-eV luminescence in solution-grown CdTe:In were inconclusive because the measured combinations of injection level dependence, frequency response, and temperature dependence did not clearly indicate whether the transition originated from a band state or from a localized level associated with a compact complex. This paper reports the discovery of CdTe:In material in which temperature-dependence data show that the 1.4-eV luminescence transition cannot originate at a band edge. However, the spectrum, injection level dependence, and frequency response of the 1.4-eV luminescence in the present material do not differ greatly from corresponding measurements on previous materials. The new data are presented in detail and include the first extensive measurements of the thermal broadening of the 1.4-eV luminescence.
Electromigration of liquid gallium inclusions in silicon
Authors: Anthony T. R.
Published: February 2003

The electromigration velocities of a liquid gallium inclusion in single-crystal silicon follow an Arrhenius relationship with temperature. The activation energy is 14.5 kcal/mol and the preexponential factor is 2.1×10−5 cm3/C. Electromigration velocities are linearly proportional to the applied electric current density. Ga inclusions electromigrate towards the cathode at all temperatures. The electron-atom momentum exhange is the principal electromigration driving force. Peltier-induced temperature-gradient zone melting contributes less than 1% of the observed electromigration velocity. Current funneling into the gallium-doped redeposited-silicon train behind the electromigrating inclusion can increase the current density passing through the inclusion by up to a factor of 10. At temperatures below 500 °C, current diversion by rectification by the p-I junction between the doped inclusion trail and the parent silicon crystal inhibits gallium-inclusion electromigration.
The electromigration of liquid metal inclusions in Si
Authors: Anthony T. R.
Published: February 2003

The electromigration velocities of liquid metal inclusions in single-crystal Si were found to follow an Arrhenius relationship with temperature. The activation energies and preexponential factors of liquid metal inclusions of Pd, Au, Cu, Al, Ag, Ga, In, and Sn were measured. Liquid Sb inclusions did not electromigrate. Electromigration velocities were linearly proportional to the applied electric current. Inclusions of Pd, Au, and Cu which have relatively high work functions electromigrate towards the anode while inclusions of Al, Ag, Ga, In, and Sn which have relatively low work functions electromigrate toward the cathode. The relative order of electromigration velocities within the anode-directed group and within the cathode-directed group can be accounted for by setting the electromigration force proportional to the difference between the work function of the metal of the inclusions and an experimentally determined null-point work function and by considering the solubility of silicon in the inclusion.
Physical structure of Al-pSi metal-insulator semiconductor solar cells
Authors: Olsen L. C. , Barton D. L. , Miller W. , Garnier J. E. , Turcotte R. P.
Published: February 2003

Investigations have been made of Al-pSi metal-insulator semiconductor (MIS) cells fabricated by depositing Al films onto silicon substrates with thermally grown SiO2 surface films on the order of 18 Å thick. These studies have involved depth concentration profiling and ellipsometric measurements to understand the physical structure, electrical and optical characterization of aluminum films, and efforts to optimize an Al-Si cell with a SiO antireflection (AR) coating. Depth concentration profiles show that the correct physical model is not Al/SiO2/Si, but Al/Al2O3(Si)/Si with the Al2O3 interfacial layer being 15 Å thick. The Al film reduces the SiO2 to yield Al2O3+Si for an interfacial film. Investigations to optimize the Al-Si cell structure involved using optical constants measured for Al films to determine AR layer thicknesses, which maximize cell photocurrent for each Al film thickness. Analytical studies were also conducted concerning sheet resistance effects to determine the required grid design to maximize the fill factor. These analytical and experimental studies are used to project an ultimate, practical AM1 efficiency of 11–12% for Al-pSi MIS cells based on a continuous metal front layer and a silicon resistivity of 2–5 Ω cm.
Polarization characteristics of dye-laser amplifiers II. Isotropic molecular distributions
Authors: Reyzer Kendall C. , Casperson Lee W.
Published: February 2003

In a previous study a general semiclassical formalism has been developed for lasers with arbitrary orientational distributions of the active molecules. Here that formalism is applied to the important case of an isotropic distribution of molecules, and this limit is especially relevant to liquid dye lasers. Extensive analytical and numerical results are presented for the polarization properties of such dye lasers. It is found that in general the polarization states of the pump and signal fields are coupled together and both change with distance in a laser amplifier.
Analysis of the pressure, density, and velocity distributions in a spectroscopic heat-pipe oven and the resulting limitations on device performance
Authors: Boyd Robert W. , Dodd Jack G.
Published: February 2003

The pressure, density, and velocity distributions within a cylindrical heat-pipe oven are analyzed for inviscid, compressible flow in either the radial or axial direction. For sufficiently large but readily attainable heat flows, density variations within the heat pipe as large as 50% which can lead to inaccuracies in quantitative spectroscopic investigations are predicted.
Determination of fuel density-radius product of inertial confinement fusion targets by neutron activation
Authors: Campbell E. M. , Lane S. M. , Pan Y. L. , Larsen J. T. , Wahl R. J. , Price R. H.
Published: February 2003

The quality of the confinement and thermonuclear burn of inertial confinement fusion targets scales as the density-radius product ρR of the fuel. Neutron activation of trace elements placed in the fuel can be used to directly measure ρR. This concept and several candidate tracers, 14N, 40Ar, and 79Br, are discussed.
Polarization characteristics of dye-laser amplifiers I. Unidirectional molecular distributions
Authors: Reyzer Kendall C. , Casperson Lee W.
Published: February 2003

Many practical laser amplifiers exhibit anisotropic gain due to polarization of the pumping fields or to a fixed preferential alignment of the active dipoles. Several specific causes and consequences of gain anisotropy are discussed in detail. In the analysis, the emphasis is placed on dye-laser systems including arbitrary amplitudes, phases, and polarizations of the pump and signal fields. Analytical results are presented for a unidrectional molecular distribution, and it is found that the polarization states of the pump and signal fields change with distance in the amplifier.
Low-current electric discharges in H2-He mixtures
Authors: Muller C. H. , Phelps A. V.
Published: February 2003

Tests are made of the ability of currently available theory to predict experimental ratios of the electric field to gas density E/N required for the steady-state operation of low-current, moderate-pressure discharges in hydrogen-helium mixtures. In the experiments the fractional concentration of H2 in He was varied from 1% to 4% and the discharge current, i.e., 40±10 μA, and total gas density, i.e., 1023–1025 atoms/m3, were chosen to avoid gas heating and striations. The experimental E/N values for the 4-mm-diam tube varied from 6×10−21 V m2 for 1% H2 in He at a gas density of 7×1024 m−3 to about 4×10−20 V m2 for 4% H2 in He at 1.5×1023 m−3. Theoretical steady-state E/N values versus gas density were calculated using (a) solutions of the Boltzmann equation for He metastable excitation, He ionization, and H2 ionization rate coefficients; (b) published theoretical calculations of the effects of a finite Debye length and a finite ion mean free path on the electron loss rate; and (c) models for the ion-molecule conversion and Penning ionization processes. The differences between theoretical and experimental values of E/N are less than 10% for total gas densities above 6×1023 m−3, but are 20–30% for a gas density of 1.6×1023 m−3. We conclude that except at low gas densities the simple theory gives a good description of low-current discharges in this gas mixture.
The mechanism of growth of quartz crystals into fused silica
Authors: Fratello V. J. , Hays J. F. , Spaepen F. , Turnbull D.
Published: February 2003

It is proposed that the growth of quartz crystals into fused silica is effected by a mechanism involving the breaking of an Si-O bond and its association with an OH group, followed by cooperative motion of the nonbridging oxygen and the hydroxyl group which results in the crystallization of a row of several molecules along a crystalline-amorphous interfacial ledge. This mechanism explains, at least qualitatively, all the results of our earlier experimental study of the dependence of quartz crystal growth upon applied pressure: large negative activation volume; single activation enthalpy below Si-O bond energy; growth velocity constant in time, proportional to the hydroxyl and chlorine content, decreasing with increasing degree of reduction, and enhanced by nonhydrostatic stresses; lower preexponential for the synthetic than for the natural silica.
Low-flux radiation-induced precipitation
Authors: Barbu A. , Martin G. , Chamberod A.
Published: February 2003

Precipitation of Ni3Si in undersaturated NiSi solid solutions is shown to be triggered by high-energy electron irradiations at very low displacement rates. The results are compared to those previously obtained under high-flux irradiations. A simple interpretation is proposed for the temperature shift of the dose rate threshold for radiation-induced precipitation in this system.
’’Charge transfer in metal/polymer contacts and the validity of contact charge spectroscopy’’
Authors: Fabish T. J. , Duke C. B. , Hair M. L. , Saltsburg H. M.
Published: February 2003

A comparison is made between two recently obtained independent sets of contact charge exchange data taken by Cottrell, Lowell and Rose-Innes, and by Fabish and Duke, respectively. Discrepancies between the two sets of data are ascribed to the utilization of different polymer preparation and processing procedures. Both sets of data are consistent with the model of contact charge exchange via localized states in the polymer proposed by Duke and Fabish. The origin of the localized electronic states in the polymers is different in the two data sets, however, because the polymer processing introduces extrinsic states in one case but not the other.
The velocity of sound for a generalized p-α model porous solid
Authors: Harris Paul
Published: February 2003

A generalized form of the Herrmann p-α model equation of state is analyzed with respect to the question of predicted sound velocity. It is shown that only for a porosity factor of α−n, with n≳1, does the predicated sound velocity decrease with increasing porosity as observed ultrasonically. The Mazzella et al. relationship between the Grüneisen parameter and the sound velocity is shown to be satisfied with any exponent n in the porosity factor.
Coherence lengths and phase conjugation by degenerate four-wave mixing
Authors: Grossman W. M. , Shemwell D. M.
Published: February 2003

The effect of coherence between pump and signal beams on phase conjugation by degenerate four-wave mixing is analyzed using a simple classical model. The influence this may have on practical applications is discussed.
Infrared-visible (0.89–0.72 μm) AlxGa1−xAs/AlyGa1−yAs double-heterostructure lasers grown by molecular beam epitaxy
Authors: Tsang W. T.
Published: February 2003

Room-temperature low-current-threshold broad-area Fabry-Perot AlxGa1−xAs/AlyGa1−y As double-heterostructure (DH) lasers have been prepared by molecular-beam epitaxy (MBE) covering the lasing emission wavelength from 8900 to 7200 Å (infrared to visible). In this emission range, the averaged pulsed current threshold densities Jth are as low as those obtained by liquid-phase epitaxy (LPE). At ∼8200 Å, the wavelength at which DH lasers have also been prepared by metalorganic chemical-vapor deposition (MO-CVD), the Jth ’s of the MBE grown lasers are lower.
Scattering of elastic waves by thin inclusions
Authors: Simons D. A.
Published: February 2003

A solution is derived for the elastic waves scattered by a thin inclusion. The solution is asymptotically valid as inclusion thickness tends to zero with the other dimensions and the frequency fixed. The method entails first approximating the total field in the inclusion in terms of the incident wave by enforcing the appropriate continuity conditions on traction and displacement across the interface, then using these displacements and strains in the volume integral that gives the scattered field. Expressions are derived for the far-field angular distributions of P and S waves due to an incident plane P wave, and plots are given for normalized differential cross sections of an oblate spheroidal tungsten carbide inclusion in a titanium matrix.
Excitation of resonant oscillations in a solid bar by 30-MeV protons
Authors: Strini A. M. Grassi , Strini G. , Tagliaferri G.
Published: February 2003

The mechanical response of a metallic bar to pulses of 30-MeV protons has been investigated. It was found that by making the pulse duration short in comparison with the periods of the low-order harmonics of the bar resonant oscillations, vibration amplitudes of the order of 10−11 cm could be measured. The required energy loss by the beam pulses amounted to about 10−5 J, and very simple theoretical considerations suffice to relate quantitatively the deposition of energy in the bar with the amplitudes of its natural vibrational modes.
Elongation upon torsion in a theory for the inelastic behavior of metals
Authors: Van Arsdale W. E. , Hart E. W. , Jenkins J. T.
Published: February 2003

The torsion of a thin-walled cylinder is studied using the low-temperature or visco-plastic limit of Hart’s state variable theory for the inelastic behavior of metals. For values of the shear stress lower than the ’’hardness’’ of the material, reversible elongation is found to accompany the recoverable twist. For shear stress exceeding the hardness there are, in addition, a permanent twist and elongation. These predictions agree qualitatively with existing experiments. Detailed quantitative results, for several loading histories, are obtained for nickel.
Beat heating of a magnetoplasma by two Gaussian beams in extraordinary mode
Authors: Thakur A. K. S. , Sharma R. P.
Published: February 2003

This paper presents an investigation of cross focusing of two Gaussian EM beams (of frequencies ω1 and ω2) propagating in the extraordinary mode in a collisionless magnetoplasma and the excitation of an upper hybrid beam at the difference frequency Δω=ω1–ω2. The effect of changing the strength of the static magnetic field on cross-focusing of the two pump waves is significant; the power of the upper hybrid beam also depends on the magnetic field.
Low work function and surface structure of the LaB6(210) surface studied by angle-resolved x-ray spectroscopy, ultraviolet spectroscopy, and low-energy electron diffraction
Authors: Oshima C. , Aono M. , Tanaka T. , Nishitani R. , Kawai S.
Published: February 2003

A clean surface of LaB6(210) exhibits the low work function of 2.2±0.1 eV at room temperature. This is lower than those of the (100), (110), and (111) surfaces. Similarly to the (100) surface, La atoms exist in a (1×1) ordered structure at the outermost layer of the (210) clean surface. The value of the low work function of LaB6 has been discussed on the basis of those data together with the Lang-Kohn theory. The changes of the (210) surface with oxygen chemisorption are more analogous to those of the (110) surface than the (100) and (111) surface. Work function changes from 2.2 to 3.1 eV with oxygen exposure and saturates above ∼15 L; the periodicity of the surface-atomic lattice disappears almost completely.
Domain electroluminescence in ac thin-film devices
Authors: Rüfer H. , Marrello V. , Onton A.
Published: February 2003

The ac thin-film electroluminescence devices employing ZnS : Mn as the active medium exhibit a ’’memory effect’’ which in turn is related to filamentary luminescence. Under certain film preparation and device excitation conditions, it is found that the filaments exhibit a large scale cooperative motion. Spontaneously moving spirals and stripes have been observed under steady-state conditions. This paper describes the phenomena, and a thermal model for the observations is proposed.
Computer simulation of the backscattering and implantation of hydrogen and helium
Authors: Eckstein W. , Verbeek H. , Biersack J. P.
Published: February 2003

The backscattering from and the implantation of 0.5–10-keV hydrogen and helium in Au is investigated with the MARLOWE and TRIM computer codes. The following are found in this paper: (1) The results of the MARLOWE and the much faster TRIM codes are in satisfactory agreement. (2) The influence of potential parameters and energy loss models (LSS and Oen-Robinson) is mainly on the heights and to less extent on the shapes of the energy distributions of backscattered particles. (3) The experimental data from the preceding paper favor the use of a potential for the calculation, which is weaker than the Molière potential. This can be simulated by using a screening length smaller than the Firsov value.
Joining and recrystallization of Si using the thermomigration process
Authors: Mizrah T.
Published: February 2003

Thermomigration of Al-rich liquid zones through Si is used to join single-crystalline Si wafers and also to recrystallize polycrystalline Si into single-crystalline material. Several possible applications of this technique are discussed.
Comment on ’’Fluorescence decay measurement via modulated gain spectroscopy’’
Authors: Lessing H. E.
Published: February 2003

It is shown that photoselection and rotational diffusion should be considered in transient-gain experiments. Modified theoretical expressions are given which describe the time dependence of gain signals for polarized beams.
Contactless monitoring of impurity activation in ion-implanted silicon by surface acoustic wave techniques
Authors: Varahramyan K. , Webster R. T. , Das P. , Bharat R.
Published: February 2003

The interaction between an implanted layer in silicon and a surface acoustic wave (SAW) traveling on a neighboring piezoelectric was studied, and the resulting transverse acoustoelectric voltage has been found to be an effective indicator of the activation of the implanted species in the silicon lattice obtained during annealing treatments following ion implantation. The method can be used to monitor an entire wafer and is nondestructive.
Diamond surface as revealed by RHEED
Authors: Yamaguchi S.
Published: February 2003

A mechanically polished brilliant surface of diamond differed from the amorphous Beilby layer as formed at solid surfaces in general. A RHEED pattern observed from the former surface was characteristic enough to demonstrate that RHEED served as a nondestructive testing means for identifying diamond.
Characterization of defects in nickel-doped MgO crystals
Authors: Narayan J. , Chen Y.
Published: February 2003

Heavily Ni-doped magnesium oxide crystals, grown by the arc-fusion technique, have been investigated using optical and transmission electron microscopy to examine the dislocation content, sub-boundaries, and impurity precipitates. Yield stress measurements were also made. Dislocation structures and impurity precipitates at the sub-boundaries are described, and their implications concerning the use of these crystals as laser materials are discussed.
Addendum: Dislocations and the piezoelectric effect in III–V crystals
Authors: Booyens H. , Vermaak J. S. , Proto G. R.
Published: February 2003

The erroneous assumption that for an insulating crystal the electrical displacement field (?) is zero in the absence of an applied electrical field has led to wrong values for the line charges associated with dislocations as well as for the electric fields and core charges associated with point defects in III-V crystals. The values for the charge distribution associated with these two types of defects are, however, not affected.
Hypothetical mechanism of operation of the Ag-O-Cs (S-1) photocathode involving the peroxide Cs2O2
Authors: Sommer A. H.
Published: February 2003

Experimental evidence is presented to support the suggestion by Gugel et al. that the low work function of the Ag-O-Cs photocathode may be attributed to small amounts of cesium peroxide (Cs2O2) which form a donor level close to the conduction band of the semiconductor Cs2O.
High precision depth profiling of light isotopes in low-atomic-mass solids
Authors: Ross G. , Terreault B.
Published: February 2003

An elastic recoil detection technique has been developed to depth profile light isotopes (A≲35) in low-atomic-mass solids (A≲16). It utilizes the maximum-scattering-angle property rather than an absorber to reduce background, with resultant depth precision of about ±2 μg/cm2 (100 Å). The sensitivity is ?5×1016 atoms/cm2 for isotopes lighter than the substrate and ?1015 atoms/cm2 for heavier ones.
Thickness measurement of gold contact layers in Si(Li) and Ge x-ray detectors
Authors: Shima K. , Umetani K. , Mikumo T.
Published: February 2003

Four kinds of Si(Li) and a high-purity Ge x-ray detectors have been tested to measure the thicknesses of gold contact layers by comparing the response of the primary Rb-Kα x-rays with that of the induced Au-Lα x rays. Observed thicknesses ranged from 140 to 260 Å. Near the x-ray energies of Au-M subshell absorption edges, the contribution of x-ray transmission through the observed gold layers to the detection efficiency is greater than or equivalent to that of the inherently attached 7.6-μm beryllium window. Hence, one must be careful in the determination of the detection efficiency in x-ray semiconductor detector when low-energy x rays of less than about 4 keV are measured.
Annealing behavior of evaporated Mo films—Direct observations by SEM
Authors: Uda Keiichiroh , Matsushita Yoshiaki , Takasu Shin-ichiro
Published: February 2003

Annealing behavior of molybdenum films 320–4900 Å thick deposited by the e-gun evaporation method on a silicon dioxide layer has been investigated directly by means of a high-resolution scanning electron microscope (SEM). The grain growth of Mo films occurs drastically at 900 °C annealing or higher. The structures of Mo films annealed higher than 900 °C exhibit film thickness dependency. At 1000 °C annealing, 1200 Å or thinner samples show columnarlike monolayer structure. In the case of the 4900-Å-thick sample, it reveals a faceted multilayer structure, and its grain size is about 1700 Å. Grain size annealing temperature dependency is well correlated to electrical resistivity dependency. In addition, it is also found that, at 900 °C annealing or lower, no interfacial reaction occurs.
Energy distribution of trapping states in polycrystalline silicon
Authors: Hirae S. , Hirose M. , Osaka Y.
Published: February 2003

The electronic density of states in the forbidden gap of polycrystalline silicon has been determined from an analysis of capacitance and conductance of a Metal/SiO2 (∼60 Å)/polycrystalline silicon(∼250 Å)/Si(111) (MOSS) structure. In this structure the thickness of the polycrystalline silicon is comparable to its grain size. Net density of trapped charges in the polycrystalline silicon is enough to terminate the electric field penetrating from the oxide layer. Then, two-terminal admittance of the MOSS structure is dominated by charging or discharging of the trapping states in a wide range of applied gate bias. The U-shaped distribution of trapping state density has been found for thin polycrystalline silicon films.
Diffusion and the power spectral density and correlation function of velocity fluctuation for electrons in Si and GaAs by Monte Carlo methods
Authors: Fauquembergue R. , Zimmermann J. , Kaszynski A. , Constant E. , Microondes Greco
Published: February 2003

In Sec. II of this work, we briefly recall the various ways of defining the diffusion coefficient D and discuss their identity in high-field conditions and in very high frequency operations. In Sec. III, theoretical values obtained by the Monte Carlo method for high static field operations in Si and GaAs are reported and discussed. In Sec. IV, the variations of diffusion values with the operational frequency or with the ’’observation’’ or sample time are studied and tentatively explained.
Silicon molecular beam epitaxy with simultaneous ion implant doping
Authors: Ota Yusuke
Published: February 2003

Silicon epitaxial layers have been made with virtually any doping profile by combining molecular beam epitaxial growth with simultaneous ion implant doping. Arsenic ions (As+) accelerated to energies between 400 and 800 eV have shown a high sticking coefficient on the heated silicon surface. Growth conditions have been defined at which epitaxial films with bulk characteristics are obtained.
An electron-microscopy study of the A15 Nb3Ge substrate interface
Authors: Antonovsky Ari , Toth Louis E. , Bradford Bradley , Goldman Allen M.
Published: February 2003

Electron microscopy has been used to study very thin Nb-Ge films sputtered-deposited onto copper substrates. Micrographs and selected-area electron-diffraction patterns reveal an interface region between the substrate and the first A15 Nb3Ge to form. This interface consists of microcrystalline Nb-N-O and a two-phase region consisting of Nb-N-O grains and an unidentifiable tetragonal Nb-Ge phase. The A15 Nb3Ge grains which form later in the growth of the film exhibit the same grain size and shape as the Nb-N-O grains. From the results a model for the role of the interface in the initial formation of A15 Nb3Ge is proposed.
Hysteresis phenomena in polyvinylidene fluoride under high electric field
Authors: Furukawa T. , Date M. , Fukada E.
Published: February 2003

Dielectric and piezoelectric responses caused by a high electric field and a 10-Hz small strain have been simultaneously measured for stretched polyvinylidene fluoride using a minicomputer system. The electric field was applied up to 240 MV/m in a sinusoidal or triangular wave form in the frequency range 10−4–10−2 Hz at temperatures between −100 and 100 °C. Ferroelectric hysteresis loops were observed even below the glass-transition temperature of −60 °C. At 20 °C the 120-MV/m electric field gave the remanent polarization Pr of 50 mC/m2 which resulted in the piezoelectric activities e31 and e32 of 70 and 7.5 mC/m2, respectively. The origin of Pr was confirmed to be the molecular dipole orientation because the value of Pr was independent of the frequency of applied field. The coercive field Ec significantly decreased with increasing temperature from 180 MV/m (−100 °C) to 25 MV/m (100 °C), while Pr showed only a slight temperature dependence.