bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonlinear analysis of the free-electron lasers utilizing a linear wiggler field
Authors: Tang Cha-Mei , Sprangle P.
Published: February 2003

A one-dimensional steady-state FEL amplifier, utilizing a linearly polarized magnetic wiggler field, is analyzed in the linear and nonlinear operating regimes. Our formulation of the FEL problem includes all the efficiency-enhancement schemes, electron-beam thermal effects and collective effects, i.e., space-charge waves. The axial electron velocity, due to a linearly polarized wiggler field, has a spatially oscillatory component. It is shown that this axial velocity jiggle does not result in phase incoherence between the electrons and the ponderomotive wave. The axial velocity jiggle is explicitly incorporated into our analytical model. The inclusion of the electron jiggle velocity is shown to have a quantitative effect on the nonlinear-wave-particle dynamics. The electron-trapping potential associated with the ponderomotive wave is also derived. Finally, a number of numerical examples pertinent to the design of a 10-μm FEL amplifier are presented.
Infrared absorption by molecular clusters in water vapor
Authors: Carlon Hugh R.
Published: February 2003

New findings concerning clusters of water molecules in water vapor and in moist air are combined with observations from classical cloud physics to show that many discrepancies can be reconciled by the existence of enormous equilibrium populations of large neutral water clusters in the vapor state. These water clusters are believed to be those ’’nuclei’’responsible for the ’’cloudlike’’ condensation first described by Wilson at supersaturations of 4–5. They absorb electromagnetic radiation at infrared and longer wavelengths, and are believed to be responsible for the atmospheric infrared continuum absorption.
Detection of vibrationally excited nitrogen by trapped electron and electron transmission methods
Authors: Michejda J. A. , Dubé L. J. , Burrow P. D.
Published: February 2003

Two techniques for detection of vibrationally excited nitrogen using low-energy electron scattering are described. The first technique uses the trapped electron method to observe excitation from Nv2 into the B3Πg state near threshold. From the known Franck-Condon factors, the contribution from excited vibrational levels may be unfolded. The second technique employs the electron transmission method to detect sharp structure in the total scattering cross section resulting from the formation of temporary negative ions. Because of uncertainties in the total scattering cross sections from each of the vibrational levels, the transmission method is less accurate than the trapped electron technique. As a consistency check, the vibrational temperature of N2 downstream from a microwave discharge is determined as a function of the discharge power. Within their respective error limits, the two methods are in good agreement.
Micromagnetics of periodic stripe domains
Authors: Tu Yih-O
Published: February 2003

The periodic stripe domains of magnetic material whose easy axis is perpendicular to the film thickness may have boundary layer behavior not only in the wall but also near the film surfaces. This behavior is especially pronounced when the material characteristic length is much less than the film thickness. By means of direct minimization from a variational principle, the magnetization in the periodic stripe domains is determined numerically using a mesh scheme, in which the boundary layer behaviors in the wall and near the film surfaces are adequately represented. The results confirmed the boundary layer behavior a posteriori. The stripe width is, in general, dependent upon Q = K/2πM2. However, the dependence is quite insensitive when the material characteristic length/film thickness ratio is less than 0.1. The results were compared with those of the theory based on the Landau-Lifshitz wall energy density concept due to Málek and Kambersky. The comparison shows that the magnetostatic energy density is substantially lower in contrast to the slight increase in the wall energy density defined as the sum of anisotropy and exchange energy densities.
Activation energy of degradation in GaAlAs double heterostructure laser diodes
Authors: Imai Hajime , Hori Ken-ichi , Takusagawa Masahito , Wakita Koichi
Published: February 2003

Aging test of GaAlAs double heterostructure (DH) laser diodes is performed in the temperature range of 50–180 °C. In samples for the aging test, AuSn-alloy bonding solder is used and the facet coating with Al2O3 film is performed. Samples are operated in the light emitting diode (LED) mode with the application of the constant current of 4 kA/cm2 and 6 kA/cm2 at temperatures above 80 °C and in the automatic power control (APC) lasing mode with the constant optical power of 5 mW/facet at 50 and 70 °C. The activation energy is 0.5 eV obtained from the results of the LED mode operation at 4 kA/cm2. The parameter to evaluate the degradation is the current at which the optical power at 25 °C is 5 mW/facet. This parameter includes the deterioration of the external differencial efficiency. It is shown that the increasing rates of this parameter are almost the same at the same temperature between the LED mode operation at 4 kA/cm2 and 6 kA/cm2. The increasing rate is almost the same when samples are operated in the APC lasing mode. Twenty-three samples operated at 70 °C maintain the optical power of 5 mW/facet set initially over 5000 h. The averaged increasing rate of that parameter in these samples is 7.1×10−6/h. The activation energy of 0.5 eV is almost the same as that of GaAlAs DH LED’s which is 0.56 eV. It is presumed that point defects which disperse homogeneously cause the degradation of laser diodes and this degradation mode seemed to be the same as LED owing to the improvements against the facet degradation and the contact degradation.
Analysis of threshold temperature characteristics for InGaAsP/InP double heterojunction lasers
Authors: Yano Mitsuhiro , Imai Hajime , Takusagawa Masahito
Published: February 2003

This paper presents a theoretical study of threshold temperature characteristics of InGaAsP/InP double heterojunction lasers, from the standpoint of carrier leakage from the quaternary active region into the InP confining layers. The leakage carrier concentration flowing beyond the heterobarrier of the InP confining layer is evaluated through an analysis of heterojunction energy-band structure. Analytical results indicate that, for an emission wavelength of 1.3 μm, the sharp increase in threshold current near room temperature is caused by carrier leakage. The contribution of carrier leakage is also discussed in relation to various wavelength InGaAsP lasers.
Numerical simulation of a system for ion temperature measurement by Thomson scattering in a tokamak
Authors: Watterson R. L. , Siegrist M. R. , Dupertuis M. A. , Morgan P. D. , Green M. R.
Published: February 2003

A numerical simulation of tokamak ion temperature measurement by collective laser Thomson scattering was performed including a Monte-Carlo technique to model the statistical properties of power spectrum estimation. The accuracy to which the ion temperature Ti, may be determined under the influence of a finite laser pulse length, a limited signal-to-noise ratio, unequal electron and ion temperatures, and the presence of heavy impurities was investigated. It is found that the effects of low-frequency plasma turbulence and heavy impurities on the scattered spectrum may be mitigated (and the required heterodyne receiver intermediate frequency bandwidth reduced) by considering only the high-frequency portion of the scattered spectrum. A ratio of total scattered power to total noise power of 1 to 2 is shown to be sufficient to determine Ti. A higher signal-to-noise ratio provides little enhancement in the accuracy of Ti determination. Improved values of Ti may be achieved by a longer laser pulse. A laser pulse at least 1 μsec long is required to measure Ti to within 10% with a signal-to-noise ratio of 2- and 2-GHz heterodyne receiver intermediate frequency bandwidth.
Method of indirect determination of the anodic and cathodic voltage drops in short high-current electric discharges in a dielectric liquid
Authors: Lhiaubet C. , Meyer R. M.
Published: February 2003

The removal of electrode material by electric discharges in a dielectric liquid is usually performed with a short interelectrode gap (about 50 μm) and short discharge durations (20–2000 μs). It is therefore virtually impossible to measure the anodic and cathodic voltage drops of such discharges. However, considering that there is a direct relation between the amount of electrode material removed and the electric energy provided in the anodic (or cathodic) region, an indirect determination of those voltage drops is obtained by comparison of experimental results concerning mass loss at the electrodes and the molten volume computed after a linearized heat-conduction model. The results obtained are in agreement with the measured value of the total interelectrode voltage drop.
Modelling strain distributions in ion-implanted magnetic bubble materials
Authors: MacNeal B. E. , Speriosu V. S.
Published: February 2003

The detailed properties of strain distributions in Ne+, B+, and He+ implanted magnetic bubble garnet materials are accounted for by calculating the nuclear energy loss as a function of depth. The calculation is based on stopped ion distributions for ZnS, with suitable corrections made for differences in material density. The constant of proportionality K between strain and nuclear energy loss, and the density ratio l are determined for each ion by comparing calculated strain distributions with experimental results obtained previously using an x-ray diffraction technique. It is found that K is roughly the same for all three ions, 0.016±0.003 (eV/Å3)−1, and that the average value l = 0.79±0.08 is consistent with the actual density ratio l = 0.72. Good agreement is found in additional examples of both single and multiple implants (±10% relative error). Finally, a procedure for selecting the incident energies and dosages required to produce a uniformly strained layer for bubble device applications is described, and then demonstrated by achieving a 0.4-um-thick layer with (1.07±0.09)% strain, using a double B+ implant.
Grain boundary recombination: Theory and experiment in silicon
Authors: Seager C. H.
Published: February 2003

Calculations have been made of the barrier heights and recombination velocities at semiconductor grain boundaries subject to uniform illumination with above-band-gap light. A detailed balance approach has been coupled with a solution of the current continuity equation to yield a full solution of the problem subject to the approximation that majority carrier currents can be properly described by thermionic emission expressions. Silicon bicrystal data are presented and shown to be in good agreement with the predictions of the theory.
Channeling of 20–800-keV arsenic ions in the 〈110〉 and the 〈100〉 directions of silicon, and the roles of electronic and nuclear stopping
Authors: Wilson R. G.
Published: February 2003

Atom- and carrier-depth distributions have been measured for As channeled in the 〈110〉 and the 〈100〉 directions of Si in the energy range from 20 to 800 keV by secondary ion-mass spectrometry and differential C-V techniques. Maximum channeled ranges in the 〈110〉 of Si are observed up to about 6 μm. The slopes p of selected range parameters plotted versus ion energy E1 are measured and used to discuss the relative roles of electronic and nuclear stopping for the channeled and random components of the depth distributions. Values of electronic stopping Se or total stopping (electronic plus nuclear) St are calculated for ion velocity v1 = 1.5×108 cm/s and values are given for k and p in the expression Se,t = kEp1 for the energy range studied. The values of p for the maximum ranges of As channeled in the 〈110〉 and 〈100〉 directions of Si are 0.50±0.03 and 0.54±0.04, respectively. The corresponding values of Se are 5.43×10−14 and 2.18×10−13 eV cm2/atom, respectively, at v1 = 1.5×108 cm/s.
Electron collision quenching of CO(v) chemiluminescence in CS2/O2 and CS2/O2/N2O flames
Authors: Kushner M. J. , Grossman W. M. , Culick F. E. C.
Published: February 2003

Chemiluminescence from vibrationally excited carbon monoxide formed by the reaction CS+O→CO(v)+S was observed in CS2/O2 and CS2/O2/N2O flames to which an electric discharge was applied. Although the total amount of chemiluminescence increased with increasing discharge current probably due to enhanced reaction rates as a result of radical formation, the vibrational distribution was quenched, becoming thermal in character. The thermalization is attributed to superelastic electron collisions [e+CO(v)→e+CO(v−1)]. The technique demonstrates a sensitive method for detecting collisional transfers between excited states by separating the perturbation (electron collisions) from the initial excitation mechanism (chemical reactions).
Ion beam extraction from a plasma with aberration reduction by method of mutual exclusion
Authors: Whealton J. H. , McGaffey R. W. , Stirling W. L.
Published: February 2003

Using an algorithm for solution of the Poisson-Vlasov equations for ions extracted from a plasma, an electrode shape is considered which has high optimum perveance and low beam divergence.
Laser cooling of heavy-ion beams
Authors: Channell Paul J.
Published: February 2003

We present a new technique for cooling heavy-ion beams. The discrete absorption spectrum of the ions and the transverse Doppler shift distinguish the transverse direction of velocity and cool the ions by photon absorption. We evaluate the total energy and time requirements for a particular example relevant to heavy-ion fusion.
An oxygen-sensitive electrode impedance in Sr-doped LaCrO3
Authors: Bethin J. , Chiang C. K. , Franklin A. D. , Snellgrove R. A.
Published: February 2003

Barrier layers are apparently formed on Sr-doped LaCrO3 that give rise to an appreciable electrode impedance with electrodes of Au or Pt. The corresponding electrode resistance is quite sensitive to the oxygen activity in the atmosphere, following atmospheric changes at temperatures near room temperature with time constants of the order of minutes or days. The electrical properties of these barrier layers at room temperature do not conform to the models of simple Schottky layers on semiconductors, but exhibit a pattern of changing oxidation states at the interface region.
Dynamic Bloch-line stacking—A new domain-wall structure at high drives
Authors: Żebrowski J. , Sukiennicki A.
Published: February 2003

The equations of motions of a flat twisted domain wall are solved numerically and the structure of the wall is investigated during motion in high-drive fields. A new domain-wall structure is obtained—dynamic Bloch-line stacking—i.e., Bloch lines are seen to nucleate faster than the ones generated earlier can punch through and so stack at both film surfaces. Thus in the moving wall more than one Bloch line is present at the same time. When dynamic Bloch-line stacking occurs in a material with high damping the velocity of the wall becomes only a weak funciton of the drive. Some supporting experimental data is discussed. In a low-damping material dynamic Bloch-line stacking is found to occur also at sufficiently high drives, but published corroborating experimental data seems to be lacking.
Electrothermal breakdown: Analytic solutions for currents and fields
Authors: Wintle H. J.
Published: February 2003

We give algebraic solutions for the voltage and temperature distributions in dielectrics under high applied voltage. The models show a restricted nonlinear steady-state current-voltage relation on approaching breakdown, and enable us to show that the usual point of collapse will be at the outside of the sample. Comparison with experimental data indicates that electrothermal breakdown is not the normal breakdown mechanism in polymeric insulators.
Internal breakdown in a dielectric target at high laser irradiance
Authors: Fedosejevs R. , Teng Yung-lu , Sigel R. , Eidmann K. , Petsch R.
Published: February 2003

Time-resolved shadowgrams of a massive plexiglass target, irradiated by a 300-ps iodine laser pulse at an intensity of 3×1015 W cm−2, show treelike structures underneath the irradiated area which extend up to a depth of ∼0.5 mm into the bulk of the plexiglass. The observed structures resemble very much the familiar discharge pattern of corona discharges. The phenomenon is attributed to internal breakdown of the plexiglass due to intense electric fields (108 V/m) which exist in the vicinity of the charged laser-produced plasma.
Dynamic computer simulation of viscous flow sintering kinetics
Authors: Ross J. W. , Miller W. A. , Weatherly G. C.
Published: February 2003

A dynamic model of sintering by viscous flow has been developed in which viscous flow is treated as an analogue of incompressible, solid elastic behavior, using finite element analysis to transform the equivalent elastic problem to one of slow viscous flow. The sintering of an infinite line of cylinders was considered with surface morphology and neck size being monitored as a function of time. In general the model yielded higher neck growth rates than those reported in the literature based on static geometric approximations to the real neck curvature. This difference is shown to be due to the relatively small radii of curvature at the neck roots found in the present study, leading naturally to a greater driving force for sintering.
Excitation mechanism of positive column He-Te laser transitions
Authors: Boyer P. K. , Collins G. J.
Published: February 2003

Using a pulsed afterglow technique, the excitation mechanism of the cw positive column He-Te laser was investigated and a velocity averaged total destruction cross section of He+ by tellurium was measured to be 1×10−15 cm2. The principle channel for excitation of upper laser levels was seen to be charge transfer collisions between He+ and Te atoms. These results are compared to similar measurements of upper laser levels of the positive column He-Se laser, and the previous hollow cathode discharge measurements of He-Te collisions as performed by Alienikov and Ushakov.
Effects of dispersion on the radiation of ion acoustic waves
Authors: Khazei Mehyar , Nelson Brian , Chan Chung , Lonngren Karl E.
Published: February 2003

The ion acoustic-wave response to an impulse excitation applied to an antenna is examined experimentally. Dispersion is found to determine the radiation characteristics.
H− ion formation from a surface conversion type ion source
Authors: Leung K. N. , Ehlers K. W.
Published: February 2003

Volume-produced H− ions have been extracted from a multicusp ion source. In addition, a molybdenum converter is installed in the source to generate surface-produced H− ions. Without cesium, the production of H− ions by the surface process is very small compared with those generated by volume production. However, the presence of cesium can greatly enhance the surface production yield. The energy spectrum shows that the surface-generated H− ions contain two distinct groups when cesium is added to the discharge. The energy of one group is essentially that of the sheath potential and appears to be produced by a desorption process. The second group of H− ions has a slightly higher energy and appears to be formed by a reflection process. Different types of converter materials have also been tested.
Misfit dislocations and the morphology of gallium aluminum arsenide epitaxial layers grown on gallium arsenide
Authors: Booyens H. , Small M. B. , Potemski R. M. , Basson J. H.
Published: February 2003

Linear morphological features which are readily revealed using Nomarski interference contrast microscopy have been observed on the surfaces of GaxAl1−xAs epitaxial layers grown by liquid phase epitaxy LPE on GaAs substrates at 950 °C. These features are introduced along one <110≳ direction in the (001) growth surface only. Annealing at the growth temperature produces a similar set of features in the perpendicular <110≳ direction. Photoluminescence topographs reveal dark lines in the substrates that are directed parallel to the sets of surface features in both annealed and unannealed crystals.
Comment on ’’The general critical state model in two dimensions and zero applied field: A uniqueness theorem and some consequences’’
Authors: Baixeras J. , Dubernet Ph. , Fournet G. , Pech T.
Published: February 2003

In an attempt to clarify the controversial views about the general validity of the rather frequently and successfully used critical state mode, we consider an explicit formulation of this model and present a careful analysis of the boundaries of the regions where the field B is zero. As a result, it seems that the arguments recently published that call into question the general validity of this mode are not acceptable.
Reply to ’’Comment on ’The general critical state model in two dimensions and zero applied field: A uniqueness theorem and some consequences’ ’’
Authors: Migliori A. , Beyer W. A. , Milton Wing G.
Published: February 2003

The comment by Baixeras et al. [J. Appl. Phys. 52, 4330 (1981)] on the recent paper by Migliori [J. Appl. Phys. 51, 3439 (1980)] utilizes counterexamples not consistent with Migliori’s premise. Baixeras et al. also fail to support their contention that in two dimensions it is possible, if more difficult, to solve a general critical state model with boundary conditions.
Comments on ’’Raman scattering from boron-implanted laser annealed silicon’’
Authors: Forman Richard A. , Bell Michael I. , Myers David R.
Published: February 2003

Measurements have been made of the Raman spectra of silicon implanted with either 11B or 10B and subsequently thermally annealed. These measurements, taken with an argon-ion laser operating at 514.5 nm and at room temperature, revealed the presence of an intrinsic two-phonon combination band underlying the 11B local mode. The coincidence of these two spectral features complicates the analysis of the annealing process as diagnosed on the basis of the Raman spectrum. The use of the 10B isotope, and its spectra, minimizes ambiguities in interpretation of the spectra of ion-implanted silicon. A reexamination of the earlier annealing studies of Engstrom and Bates is suggested on the basis of the present results.
A study of Ge/GaAs interfaces grown by molecular beam epitaxy
Authors: Stall R. A. , Wood C. E. C. , Board K. , Dandekar N. , Eastman L. F. , Devlin J.
Published: February 2003

Ohmic contacts to n-GaAs using a Ge/GaAs heterojunction have been developed. Ge layers with free-electron concentrations above 1×1020 cm−3 have been grown on GaAs by molecular beam epitaxy (MBE). Gold evaporated on such structures forms tunnel contacts through the Ge to the GaAs. The lower barrier height of metals on Ge compared to GaAs and the small barrier at the Ge/GaAs heterojunction facilitates the formation of contacts with specific contact resistances below 10−7 Ω cm2.
Characterization of electron traps in SiO2 as influenced by processing parameters
Authors: Young D. R.
Published: February 2003

Qualitative comparisons have been made of the effect of processing conditions on the electron trapping characteristics of SiO2 using Si-SiO2-Al capacitors. In the presentwork, we have characterized the traps involved and studied their relationship to the processing. Four different traps have been characterized and the results indicate the smallest trap (cross section of ∼9×10−20 cm2) is independent of the processing conditions. The larger traps are dependent on the processing used. The largest trap appears in the sample without the post metallization annealing treatment and has a cross section of 8×10−18 cm2. The trap with cross section of 2×10−18 cm2 appears after post metallization annealing. The importance of these treatments explains discrepancies in the results of earlier work.
Electron transport across the abrupt Ge-GaAs n-n heterojunction
Authors: Ballingall J. M. , Stall R. A. , Wood C. E. C. , Eastman L. F.
Published: February 2003

Low-temperature current-voltage data for a degenerate Ge/nondegenerate GaAs (100) n-n abrupt heterojunction grown by molecular beam epitaxy (MBE) is presented. For low reverse bias, the reverse current density J versus voltage V is fit empirically by the relation J = αV e−ΔE/kT with ΔE = 80 meV ±10 meV and α independent of T. A model is presented which indicates that the difference between the work function of degenerate Ge and the electron affinity of GaAs is ?80 meV.
Current instability phenomena in ZnO varistors under a continuous ac stress
Authors: Gupta T. K. , Carlson W. G. , Hower P. L.
Published: February 2003

A zinc oxide (ZnO) varistor subjected to a 60-Hz voltage below the characteristic turn-on voltage exhibits an increase in the resistive component of current with time. The rate of current increase with time can be increased with an increase in applied voltage and/or temperature. An analysis of current rise with an applied 60-Hz voltage stress and current decay with no voltage stress data obtained for ZnO varistors indicates that the current instability phenomena is associated with the diffusion of interstitial zinc in the depletion layer regions adjacent to the ZnO-ZnO grain boundary.
The behavior of dislocations in GaAs substrates during the growth of GaxAl1−xAs epitaxial layers
Authors: Booyens H. , Basson J. H. , Small M. B.
Published: February 2003

Infrared elastobirefringence is used to investigate the dislocation distribution in GaAs substrates on which Ga0.35Al0.65As epitaxial layers have been grown at 950 °C using liquid phase epitaxy. A marked asymmetry is observed in the dislocation distributions as regards the two nonequivalent 〈110〉 directions in the (001) plane. The dislocation distributions consist mainly of 60° dislocations and a small number of pure edge dislocations. Almost all the dislocations are of the α type. The dislocation distributions observed are discussed with reference to the properties of the dislocations involved and the temperature dependences of the lattice parameters of the epitaxial layer and the substrate.
Cathodoluminescence from defects in indented MgO
Authors: Piqueras J. , Llopis J. , Delgado L.
Published: February 2003

Transmission electron microscopy and the cathodoluminescence mode in the scanning electron microscope have been used to study indented MgO single crystals and to relate luminescence emission and defect structure. Color images of cathodoluminescence indentation rosette have been also obtained. Marked differences in the emission and the defect structure in different areas of indentation have been found and in particular a high density of defects have been observed in the center of indentation including some defects which seem to be characteristic of this region.
A new characterization parameter for hydrogenated amorphous silicon: B (the square of the gradient of the (αh/ω)1/2 versus h/ω plot)
Authors: Sakata I. , Hayashi Y. , Yamanaka M. , Karasawa H.
Published: February 2003

We have found that B (the square of the gradient of (αh/ω)1/2 versus h/ω plot) is dependent on the preparation conditions of a-Si:H films and has a distinct correlation with photoconductivity. B includes information on the tail states and the band edge of extended states of a-Si:H. B is proposed as one of important characterization parameters for a-Si:H as well as photoconductivity.
Radiative cooling to low temperatures: General considerations and application to selectively emitting SiO films
Authors: Granqvist C. G. , Hjortsberg A.
Published: February 2003

Radiative cooling occurs because the atmospheric emittance is low in the wavelength interval 8–13 μm particularly if the air is dry. We derive expressions which specify the optical properties demanded for a surface capable of being cooled to low temperatures. The key factor is infrared selectivity with low reflectance in the 8–13 μm ’’window’’ but high reflectance elsewhere. Considering only radiation balance, ideal surfaces of this type can yield temperature differences of ∼50 °C while the cooling power at near-ambient temperatures is ∼100 W/m2. However, nonradiative exchange limits the practically achievable temperature difference. SiO films on Al were investigated as an example of an infrared-selective surface. The infrared optical properties of SiO were determined by a novel and accurate technique. These data were used to compute the spectral radiative properties of Al coated with SiO films of different thicknesses. The spectral selectivity was largest for 1.0-μm-thick films. This kind of surface was produced by evaporation of SiO onto smooth Al. The measured reflectance agreed with computations. Practical tests of radiative cooling were performed using a SiO-coated Al plate placed under transparent polyethylene films in a polystyrene box. An identical panel containing a blackbody radiator was used for comparison. The performance of the panels was tested during clear nights. It was in good qualitative agreement with theoretical expectations.
Absorption of high-intensity CO2 laser light in p-type semiconductors with small spin-orbit splittings
Authors: James R. B. , Smith D. L.
Published: February 2003

We present the results of a theory describing the saturation behavior of p-type semiconductors, such as Si, with small spin-orbit splittings by high intensity light with a wavelength near 10 μm. We consider absorption due to direct intervalence-band transitions between the heavy-hole and light-hole, heavy-hole and split-off, and light-hole and split-off bands. The functional form for the saturation of each transition is given and values for the saturation intensity as a function of photon energy and temperature are reported.
The dynamic effects of a thin metal plate during pulse heating and expansion into the liquid-vapor region
Authors: Baxter Richard C. , Giedt Warren H. , Woodruff Lawrence W.
Published: February 2003

The dynamic response of lead targets 0.025 mm and 0.05 mm thick to heating by a 1.0 MeV electron beam for about 50 ns is described. The lead targets were contained between a thin titanium tamping layer and a thick layer of fused quartz. Measured and predicted peak stresses in the quartz for no gap between the lead and the confining surfaces were approximately 12 kbar and agreed within 1 kbar. Peak stresses decreased rapidly with gap size to values, at 0.025-mm gaps, of about 1 kbar for the 0.025-mm lead targets and 5 kbar for the 0.05-mm targets. Predicted and measured values of tamper velocity (momentum) were within 10% only when the lead and confining walls were in close contact. The observed velocities for even very small gaps were substantially below predictions.
Optical damage resistance of monovalent ion diffused LiNbO3 and LiTaO3 waveguides
Authors: Jackel J. L. , Olson D. H. , Glass A. M.
Published: February 2003

We report measurements of the zero field photorefractive sensitivity (optical damage) of waveguides fabricated by silver ion exchange in both LiNbO3 and LiTaO3 and of LiNbO3 :Ti guides diffused in the presence of H20. Marked differences in the photorefractive sensitivity are found for the different fabrication proceseses. In particular, LiNbO3 :Ti guides diffused in the presence of H20 were significantly less susceptible to optical damage than those diffused in a dry atmosphere, and no index changes were observed in LiTaO3 :Ag waveguides for exposures up to 105 J/cm2 at 4579 Å.
An improved model for electrical conduction in thin films
Authors: Ghodgaonkar A. M. , Ramani K.
Published: February 2003

An improved model for electrical conduction in thin films has been worked out within the frame-work of the Fuchs-Sondheimer formalism, replacing the artificial specularity parameter P by a memory indicator γ which describes the intermediate cases between bulk material and perfectly diffusing thin film. The ratio of the bulk conductivity σ0 to thin-film conductivity σ is computed for various values of thickness a to mean free path l for a fixed value of memory indicator γ. The predicted results are in good agreement with the experimental data of Larson and Boiko as compared with those of Fuchs-Sondheimer, yielding confidence in the equations developed.
Comment on ’’I-V and C-V characteristics of Cr∥H-Pc∥Cr organic sandwich cell’’
Authors: Popovic Zoran D.
Published: February 2003

It has recently been suggested that the capacitor discharge measurement on an organic Schottky diode determines the injected space charge rather than the barrier charge. The observation of an integral capacitance exceeding the high-frequency capacitance is shown to imply that the barrier charge is in fact the measured quantity.
Metal-insulator-semiconductor capacitors with bismuth oxide as insulator
Authors: Raju T. A. , Talwai A. S.
Published: February 2003

Metal-insulator-semiconductor capacitors using aluminum Bi2O3 and silicon have been studied for varactor applications. Reactively sputtered Bi2O3 films which under suitable proportions of oxygen and argon and had high resistivity suitable for device applications showed a dielectric constant of 25.
Numerical solution of heat flow in the laser addressed liquid-crystal display
Authors: Armitage D.
Published: February 2003

A smectic liquid-crystal device is thermally addressed by means of a laser beam. The heat-flow problem is solved by a finite difference method. Computed results are presented for temperature distribution, pulse length dependence, substrate thermal parameters, and laser beam diameter.
Investigation of high-temperature annealing and quenching effects on Al-nSi diodes by C-V and I-V measurements
Authors: Wu C. M. , Yang E. S.
Published: February 2003

The behavior of Al-nSi diodes heat treatment above the eutectic temperature (600 °C) is studied by varying the annealing time and cooling rate. We have used the capacitance-voltage characteristic as a measure of the influence of the doping density and thickness of the recrystallized silicon layer at the interface. Poisson’s equation is solved to obtain the C-V characteristic and to relate it to the effective barrier height. We find that the barrier height is independent of the annealing time, but it is a function of the cooling rate. It appears that the diffusion of aluminum into silicon does not play a significant role, but fast quenching tends to prevent aluminum from precipitation, so that the recrystallized silicon layer is highly doped.
(YSmLuBiCa)3(FeGe)5O12 liquid phase epitaxial films: High Q and high μW small bubble materials with large Faraday rotation
Authors: Hibiya Taketoshi
Published: February 2003

Visual observation for smaller bubbles using conventional microscopes with small numerical aperture by the Faraday effect becomes more difficult, due to decrease in bubble layer thickness, as long as conventional (YSmLuCa)3(FeGe)5 films with Faraday rotation coefficient φF of 760 °/cm are used. In order to solve this problem from the view point of materials research, (YSmLuCa)3(FeGe)5 as films with φF of −1500∼−2000 °/cm were grown. Employing this material, bubble domain visual observation is 2∼3 times improved. (YSmLuCa)3(FeGe)5O12 films have higher Q factors (3.6∼4.5) and higher mobility μW (330∼1080 cm/s Oe) than conventional (YSmLuCa)3(FeGe)5O12 films. Since the Sm3+ content necessary to obtain the same anisotropy energy Ku is smaller for (YSmLuCa)3(FeGe)5O12 than for (YSmLuCa)3(FeGe)5O12, a smaller damping parameter α is obtained for substituted materials.
Electromagnetic-acoustic coupling in ferromagnetic metals at liquid-helium temperatures
Authors: Gordon R. A.
Published: February 2003

Electromagnetic-acoustic coupling at the surface and in the bulk of ferromagnetic metals at liquid-helium temperatures has been studied using electromagnetically excited acoustic standing-wave resonances at MHz frequencies in a number of ferromagnetic metals and alloys of commercial interest. The experimental results are compared with similar measurements at room temperature in the same and in different samples as well as with existing theoretical descriptions of the phenomenon.
Surface photovoltage in Ge-doped p-type AlxGa1−xAs
Authors: Kalnitsky A. , Zukotynski S. , Sumski S.
Published: February 2003

The surface photovoltage of Ge and Zn doped p-type AlxGa1−xAs has been measured in the temperature range 100–300 K. The results are interpreted to yield the ionization energy of the impurities and the energy gap of the material. The effect of impurity bands is discussed.
Nd:YAG laser annealing of arsenic-implanted silicon: Dependence upon scanning speed and power density
Authors: Tsien P. H. , Ryssel H. , Röschenthaler D. , Ruge I.
Published: February 2003

The annealing behavior of arsenic-implanted silicon using Nd:YAG laser irradiation was investigated. The annealing process depended upon the scanning speed and the power density. The carrier concentration at the surface was higher by factor of approx. 1.5 to 3 than in the bulk. Multiple irradiation resulted in a profile broadening and a reduced carrier concentration in the bulk. The dependence of the electron mobility upon the electron concentration up to 1.5×1021 cm−3 was measured. The experimental results show that the electron mobility depends only on the electron concentration, and is independent of the conditions of annealing.
I* (6s 4P) Collisional quenching: Application to the IF 491-nm laser
Authors: Hutchison S. B. , Verdeyen J. T. , Eden J. G.
Published: February 2003

The room-temperature rate constants for quenching of I* (4P) atoms in binary collisions with Ar, Xe, NF3, UF6, and CF3I have been measured to be ≲2×10−13, (8.3±0.5)×10−11, (2.6±0.5)×10−11, (5.8±0.4)×10−10, and (3.8±0.4)×10−10 cm3 sec−1, respectively. These constants were obtained by examining the exponential time decay of the IF (D′→A′) fluorescence in the afterglow of electron beam produced plasmas containing Ar, CF3I, NF3, and the desired quenching gas. Also, further experimental evidence in support of neutral channel formation of IF* via quenching of I* (4P) states by fluorine containing molecules in e-beam-pumped Ar/CF3I/NF3 mixtures is presented.
Characterization of negative electron beam resists based upon generalized gel formation theory
Authors: Kobayashi Toshio , Arai Eisuke
Published: February 2003

Contrast and sensitivity of negative electron beam resist have been studied, using the gel formation theory generalized for an arbitrary number of active bonds m created and retained at a reacting site in one irradiation-reaction process. For m = 1, such as in chloromethylated polystyrene (CMS), and m = 2, such as in polyesters and poly (glycidyl methacrylate) (PGMA), the dependence of contrast and sensitivity on inhibitor activity, molecular weight of polymer or copolymer, and polydispersivity is shown theoretically. The results obtained show that (i) the highest contrast is obtained for the negative resist in which m = 1 and the value of the contrast is 2.7 in the ordinarily used molecular size, and (ii) the sensitivity of the resist in which m = 2 is higher than that in which m = 1, provided other parameters are the same.
Metal-polymer interfaces: Adhesion and x-ray photoemission studies
Authors: Burkstrand James M.
Published: February 2003

The interfaces formed by evaporating copper, nickel, and chromium layers on polystyrene, polyvinyl alcohol, polyethylene oxide, polyvinyl methyl ether, polyvinyl acetate, and polymethyl methacrylate have been studied with x-ray photoemission spectroscopy (XPS). The adhesion strengths of the metal films to the polymers were measured by a tensile-pull test. At submonolayer coverages of the metals, the peak positions and widths of the metallic electron core levels measured with XPS vary significantly from one polymer substrate to another. Most of these variations can be accounted for in terms of changes in the atomic and extra-atomic relaxation energies during the photoemission process. Much of this change is brought about when the metal atom deposited on an oxygen-containing polymer interacts with the substrate oxygen and forms a metal-oxygen-polymer complex. The presence of this complex is verified by changes in the photoemission lineshapes of the substrate carbon and oxygen atoms. The XPS signatures of these various complexes are quite similar and suggest that they are chelate-like complexes. The adhesion strength of any metal on an oxygen-containing polymer is greater than on the oxygen-free polystyrene. In general, the increased adhesion strength correlates with the presence of the metal-oxygen chelate complexes.
The effect of chemical surface treatments on non-native (Bi2O3) GaAs metal-insulator-semiconductor solar cells
Authors: Wang Edward Y. , Pandelišev Kiril A.
Published: February 2003

GaAs metal-insulator-semiconductor solar cells with a physically deposited Bi2O3 interfacial layer have been investigated. The deposition techniques used in the study were electron beam and boat thermal evaporation. The cells fabricated with interfacial layers of Bi2O3 showed a substantial improvement in open-circuit voltage over cells made without the physically deposited oxide layer. An etch has been used which yields an irregular ’’textured’’ surface. Cells employing this surface had a higher short-circuit current than those made with smooth, polished surfaces. The open-circuit voltages of these textured cells were lower than those with smooth surfaces. Calculations of the dependence of open-circuit voltage on pinhole density are in agreement with these results since a rough surface has a greater probability of pinholes.
mm-wave mixer with Nb-Te-Nb Josephson junction
Authors: Nagata Koichi , Takayanagi Hideaki , Uehara Shingo
Published: February 2003

A mm-wave Josephson integrated mixing circuit has been fabricated. In the circuit, an Nb-Te-Nb sandwich Josephson junction was used as the active element. Both RF and IF circuitries were made in the form of superconducting microstriplines using Si wafer as the dielectric layer. The signal and local powers were fed through tapered ridge waveguides, which were coupled into the stripline with small loss. The circuit was tested at 50-GHz signal frequency and the conversion efficiency was measured at −7.4 dB, for a junction with 0.4-mV ICRN product. The measured efficiency showed good agreement with the theoretical prediction.
Breakdown and prebreakdown phenomena in liquids
Authors: Devins John C. , Rzad Stefan J. , Schwabe Robert J.
Published: February 2003

In this paper we present a comprehensive account of our results on streamer propagation in dielectric fluids in point-plane geometries. Propagation velocities for both positive and negative streamers have been determined as a function of the following parameters: temperature, pressure, density, viscosity, composition, and conductivity. Effects of voltage and interelectrode spacing were examined. Current and light emission during streamer growth were measured. The relation between shock wave and streamer velocities was investigated. Small concentrations of low-ionization potential additives markedly accelerated the positive streamers, while electron scavengers accelerated the negative streamers. Mechanisms to account for these observations are discussed.
Crystallographic polarity and chemical etching of CdxHg1−xTe
Authors: Fewster P. F. , Cole S. , Willoughby A. F. W. , Brown M.
Published: February 2003

The absolute crystallographic polarity of CdxHg1−xTe crystals (x?0.2) has been determined using the anomalous scattering of x rays and correlated with the chemical etching characteristics. It is shown that Cr Kα radiation adequately distinguishes 333 and 3̄3̄3̄ reflections, and that the reflected intensities agree closely with theoretical calculations. Using a range of chemical etchants it is reported that dislocation etch pits are revealed on the (111) or A face, i.e., the face terminating with triply bonded Cd (Hg) atoms or singly bonded Te atoms, and not on the (1̄1̄1̄) or B face.
Ion channeling and Auger electron spectroscopy study of Sb-diffused Pb1−xSnxTe crystals
Authors: Alexander R. B. , Dorenbusch W. E. , Lo W.
Published: February 2003

An experimental study has been made of the effect of Sb diffusion on the crystalline quality and surface composition of Pb1−xSnxTe single crystals (x≊0.13) used in fabricating homojunction diode lasers. Both ion backscattering-channeling and Auger electron spectroscopy have been employed. It is found that the crystalline quality in the bulk improves on diffusion, due to a decrease in dislocation density associated with the diffusion temperature. In the near-surface region the quality deteriorates, due to the production of defects which are probably small clusters associated with Sb. The most pronounced effect is a partial or total loss of Te (and probably Sn) from the native oxide, accompanied by other changes in the oxide composition. A long term growth of a very thick oxide also occurs following diffusion. The changes in the oxide can be related to the formation of a p-type surface layer on diffused crystals exposed to air, through oxygen adsorption.
Silver recoil yield resulting from krypton implantation
Authors: Christel L. A. , Gibbons J. F.
Published: February 2003

The number of silver atoms which is recoil implanted into silicon during implantation of 255-keV krypton is investigated as a function of silver film thickness and krypton dose using helium Rutherford backscattering. Results are in good agreement with calculations based on a Boltzmann transport equation approach. These calculations verify that the secondary and higher-order recoils play a significant role in determining the total yield.
Effect of oxygen on the diffusion of Al in Pt films
Authors: Chang Chin-An
Published: February 2003

Diffusion of Al in Pt films over the temperature range of 200°–600 °C has been studied in different ambients. A single phase of Pt5Al3 is observed in forming gas at 200 °C, which starts to transform into Pt3Al above 400 °C. In the presence of oxygen, however, the formation of Pt5Al3 is completely suppressed at 200 °C and greatly reduced at 300 °C. It also slows down the transformation into Pt3Al at higher temperatures. These are in agreement with the predicted effect of oxygen on the diffusion of Al in Pt films.
Hillock-free integrated-circuit metallizations by Al/Al-O layering
Authors: Faith T. J.
Published: February 2003

Hillocks which grow on aluminum integrated-circuit films during the contact alloying process present processing and reliablity problems. Layered Al/Al-O films, deposited by periodically introducing controlled amounts of oxygen into the aluminum-deposition chamber, are shown to provide dramatic improvements in post-anneal film-surface topography. Aluminum films, unlayered Al-O films, and layered Al/Al-O films were deposited on thermally-oxidized silicon wafers in an e-beam system to thicknesses of approximately 1 μm at a rate of 25 Å/s. The films were photolithographically patterned into arrays of 100×100-μm bond pads and 7-μm lines, and annealed in forming gas for 20 min at 530 °C. After these anneals, both aluminum films and unlayered Al-O films with oxygen concentrations less than approximately 6 at.% had surface protrusions (hillocks and/or whiskers) approximately 1 μm in height. Protrusion density was on the order of 105 cm−2. Al-O films with oxygen concentrations greater than 6 at.% displayed blistering and had resistivities greater than twice those of aluminum films. Layered Al/Al-O films with a structure consisting of four layers of 1000-Å Al/1000-Å Al-O topped with 2000 Å of Al had no protrusions with heights greater than 0.5 μm for oxygen concentrations in Al-O layers ranging from 1.5 to 6 at. %. Overall composite-film resistivities ranged from approximately 15–45% higher than aluminum films over this oxygen-concentration range. Both film surface roughness and the density of hillocks with heights less than 0.5 μm decreased with increasing oxygen concentrations. The thickness of the top Al layer was an important layering parameter; 1-μm hillocks appearing on bond pads of films with top Al layers either less than approximately 1500 Å or greater than approximately 3000 Å thick. However, the 7-μm lines were hillock free even for such non-optimum layering structures. Al/Al-O layering also yielded dramatic improvement in post-530 °C-anneal topography for films deposited at 4 Å/s in an S-Gun® magnetron sputtering system. The S-Gun layered films had a generally higher density of short ( ⩽ 0.5 μm) hillocks than the e-beam layered films.