bluuebunny/crossref_metadata_2025 huggingface dataset:
Resonance Tunneling Through Impurity States in Metal-Insulator-Metal Junctions
Authors: Gadzuk J. W.
Published: February 2004

Motivated by the recent work of Parker and Mead on the effects of impurity trapping states in Schottky barriers, a theory of resonance tunneling through adsorbed atoms in field emission is modified to treat resonance tunneling through isolated and uniformly distributed impurities in the insulating layer of a metal-insulator-metal tunnel junction. In analogy with the magnetic impurity tunneling theory of Appelbaum, the effects of resonant tunneling through impurity states open up new tunneling channels with a concomitant change of slope in the current-voltage characteristics. These changes should be apparent as definite structure in curves of dσ/dV versus voltage although depending upon the impurity concentrations and impurity level positions relative to the Fermi levels of the two metals, the height of the structure reflecting the impurity energy level spectrum may not rise above the noise level. In addition it is seen that the presence of impurities can alter the total conductance of a M-I-M tunnel junction. The new conductance versus voltage characteristics are calculated.
Relaxation of a Surface Scratch by Viscous Flow
Authors: Cosgrove G. J. , Seigle L. L.
Published: February 2004

The Fourier-Moment method developed by King and Mullins has been applied to the case of an isolated scratch decaying by viscous flow in an amorphous material such as a simple glass. Using the Stokes-Einstein equation to relate the diffusivity and viscosity coefficients, a comparison of rates suggests that viscous flow would predominate over volume or surface diffusion as the mechanism of scratch healing in simple amorphous materials for scratch widths above approximately 0.1 μ.
Threshold Requirements and Carrier Interaction Effects in GaAs Platelet Lasers (77°K)
Authors: Rossi J. A. , Keune D. L. , Holonyak N. , Dapkus P. D. , Burnham R. D.
Published: February 2004

The experimentally observed thresholds for laser operation of optically pumped GaAs platelets are presented. The measurements were performed on uniformly doped samples of p-type, n-type, and compensated crystal (doping range 1014/cm3≤n, p≤1020/cm3). The observed thresholds are considerably lower than previously measured or predicted and exhibit no essential dependence upon impurity concentration. The 16-meV shift of laser photon energy from bandgap in lightly doped GaAs is ascribed, as before, to electron-hole-lattice (EHL) interactions. Based upon the results of platelet laser threshold data and photon energy data, a comparison is made of the relative strength of the various EHL interaction mechanisms. If Coulomb interaction and dielectric screening can be ignored, over a certain doping range a remarkable fit of the photon energy data is afforded by the electron-electron interaction mechanism.
Effect of the Donor Concentration on the Green Electroluminescence from Gallium Phosphide Diodes
Authors: Dierschke E. G. , Pearson G. L.
Published: February 2004

The optical properties of gallium phosphide green electroluminescent diodes formed by the in-diffusion of zinc or beryllium into sulfur-doped vapor-phase epitaxial gallium phosphide have been studied as a function of donor concentration at temperatures between 77° to 350°K. At 77°K shallow-donor-shallow-acceptor pair emission dominated for all diodes at high currents. At room temperature, bound exciton emission involving residual nitrogen impurities was dominant for lightly doped samples, while shallow-donor-valence-band emission was dominant for samples with a donor concentration greater than 8×1017 cm−3. For both types of emission, the intensity at 300°K varied as exp (qV/kT). Relatively low efficiencies appeared to be a result of short nonradiative lifetimes in the vapor-grown GaP. Electron microprobe measurements verified that variations in the positions of the emission lines from crystal to crystal were due to As contamination. An acceptor ionization energy of 56 meV was deduced for beryllium from a study of the low-temperature emission spectra.
Forward and Reverse Tunnel Currents in Gallium Phosphide Diffused p-n Junctions
Authors: Dierschke E. G. , Pearson G. L.
Published: February 2004

The current-voltage characteristics of zinc-diffused and beryllium-diffused p-n junctions in gallium phosphide have been studied at temperatures between 77° and 300°K. The dominant forward current over most of the bias range for the zinc-diffused diodes varied as exp (βV+γT), where β and γ are relatively independent of temperature and voltage. This current was shown to be qualitatively consistent with a simple tunneling model involving states in the forbidden gap. For high bias in the zinc-diffused diodes and for most of the bias range in the beryllium-diffused diodes, the dominant forward current was due to thermal recombination in the space-charge region via deep traps. The reverse current in the pre-avalanche breakdown region for all diodes appeared to be dominated by internal field emission, or Zener tunneling.
ESR Determination of Electron Effective Masses in GaxIn1−xSb Alloys
Authors: Title R. S. , Plaskett T. S.
Published: February 2004

Electron spin resonance and bandgap measurements have been used to derive the effective masses of GaxIn1−xSb alloys in the range 0<x<0.54. The effective masses are found to vary smoothly with composition and their values are found to be in good agreement with the masses calculated from Kane's theory of a k=0 conduction band.
Plane Stress Wave Propagation in Solids
Authors: Fowles Richard , Williams Roger F.
Published: February 2004

This paper shows that in general, plane stress waves in solids or fluids exhibit two phase velocities. One of these is associated with the stress profile of the wave and the other with the mass-velocity profile. These velocities are distinct except for isentropic simple waves, steady flow, or discontinuous fronts, As a result, the determination of time-dependent constitutive relations from shock-wave experiments requires more measurements than has heretofore been recognized.
Energy Transfer and Fluorescence Quenching in Eu- and Nd-Doped Silicate Glasses
Authors: Sharp Edward J. , Weber Marvin J. , Cleek Given
Published: February 2004

Radiative and nonradiative energy transfer and decay processes have been investigated in high silicate glasses co-doped with Eu and Nd. Energy transfer from Eu to Nd was established from an examination of the excitation spectra and the increased Eu decay rates in the presence of Nd. Measurements of the concentration dependences of the Eu3+ and Nd3+ fluorescence lifetimes reveal the presence of four distinct processes arising from various ion-ion interactions: (1) self-quenching of the Nd3+ fluorescence, (2) self-quenching of the Eu3+ fluorescence, (3) nonradiative energy transfer from Eu3+ to Nd3+, and (4) Eu quenching of the Nd3+ fluorescence. This last process decreases the radiative quantum efficiency of the 4F3/2 state of Nd3+, thus limiting the attractiveness of Eu sensitization for Nd laser action.
Optical Constants of YVO4 Between 2 and 25 eV
Authors: Kingsley J. D. , Ludwig G. W.
Published: February 2004

The optical constants of YVO4 have been determined from 1.96 to 25 eV. In the region of high transparency, from 1.76 to 3.7 eV, the refractive index was determined from prism refraction measurement. Near-normal-incidence reflectivity measurements were made from the absorption threshold to 25 eV. These data were extrapolated to zero and to infinite frequency and the optical constants were obtained from a Kramers-Kronig inversion. Our spectra are in good agreement with the predictions of Walter and Butler. The complex dielectric function, ε1+iε2, was approximated by a simple Lorentzian oscillator model and it was found that the optical spectra from 2 to 25 eV can be attributed to only 24 electrons per YVO4 molecule. The same result is obtained from sum rule computations on ε2 and −Im 1/ε out to 200 eV, using the extrapolated results. The maximum in the loss function, −Im 1/ε occurs at 23 eV.
Dependence of Mass-Spectrum Line Shape on the Energy Spread of the Ion Beam in a Radio-Frequency Mass Spectrometer
Authors: Lall H. B.
Published: February 2004

This paper discusses the dependence of performance of an aperiodic rf mass spectrometer on various factors. The influence of (a) initial energy spread from the ion source itself, (b) thermal energy spread of the ion beam, (c) space-charge effect in the analyzer as well as in the ion source, (d) microoptics of the analyzer grids, (e) inaccurate alignment of the analyzer configuration, and (f) shape, strength, and stability of the modulating signal upon the mass-spectrum line shape and hence the resolving power of the Bennett type rf mass spectrometer has been investigated. The solution of the energy modulating function has been determined using an I.B.M. computer 1620 and the maximum permissible inaccuracies in the stage separations are determined.
FMR Study of Surface-Tension-Related Stress Effects in Ultraclean Ni Thin Films
Authors: Janssen M. M. P.
Published: February 2004

Ni thin films, ranging in thickness from 19 to 837 Å, were deposited under ultrahigh vacuum conditions (10−9 to 10−10 Torr) onto extremely well degassed substrates. Intrinsic isotropic stress values in the films were determined by ferromagnetic resonance; these measurements were carried out while the films were in the vacuum system in which they had been prepared. Films deposited onto substrates at 25°–35°C were in a state of compressive stress when measured in UHV. The surface tension provides an explanation for these stresses; the stress levels are shown to obey a simple model. After adsorption of O2, N2O, or air, the stress levels in the films dropped to very low values, while adsorption of H2, H2O, CO, and pyridine resulted in slightly smaller effects. Admission of N2 to the films caused no stress release. A small degree of reversibility of the latter effect was found for H2 and H2O. Adsorption of gases had a marked effect on the ferromagnetic resonance linewidths. Films thinner than 100 Å showed deviations from the surface tension model and the possible discontinuity of such films is indicated as the reason. Experiments on annealed films and experiments with films deposited onto substrates at elevated temperatures were performed. The influence of vacuum conditions other than UHV during film deposition was investigated. The relevance of this study to the solution of the problems of stress corrosion cracking and hydrogen embrittlement is pointed out.
Observation of Spin Wave Resonance in Ni Thin Films after Adsorption of Oxygen
Authors: Janssen M. M. P.
Published: February 2004

Ni thin films were deposited in ultrahigh vacuum (UHV) onto soft glass substrates. Film thicknesses ranged from 74 to 837 Å. On films in UHV, only the uniform precession mode was observed during the microwave experiments. Admission of gases such as H2, H2O, O2, N2O, and air caused a lowering of the resonance field of the uniform precession mode. This effect was interpreted earlier as a relief of compressive stress related to surface tension. After adsorption of gases the films were virtually stress free. In the case of O2, N2O, and air admission a standing spin wave resonance (SWR) mode (p=1) slowly developed in films thicker than 400 Å after the lowering of the resonance field of the uniform precession mode was observed. From the fact that in UHV and in the presence of H2 and H2O no SWR was found, while development of the first mode was slow in oxygen-containing atmosphere and was thought to be related to the growth of a NiO layer, it may be concluded that spin wave excitation is made possible in this case as a result of surface spin pinning due to ferromagnetic-antiferromagnetic exchange coupling (Meiklejohn and Bean) rather than surface anisotropy (Néel). The surface spin pinning was found to be weak but the intensity of the first mode increased rapidly with film thicknesses above 400 Å. On the basis of the surface spin pinning model proposed by Kittel the exchange constant A was assigned an average value of 0.74×10−6 erg/cm.
Mechanical Properties of Copper Films
Authors: Leidheiser H. , Sloope Billy W.
Published: February 2004

The mechanical properties of polycrystalline copper films, 700–5000-Å thick, were measured using the bulge technique. The breaking strength increased with decreasing film thickness, the greatest increase occurring below 1000 Å. The equivalent bulk breaking strength was found to be 61 000 lb/in2. Young's modulus was independent of film thickness and had the normal value 18×106 lb/in2.
Observation of Flat Counting Distribution for Poisson Process with Linearly Swept Mean
Authors: Teich M. C. , Diament Paul
Published: February 2004

Gamma-ray counting experiments performed with a gated counting time which increases linearly are reported. The resultant counting distribution is flat over a large bandpass of counts as predicted earlier for photocounting experiments, or for any Poisson process, when the mean is linearly swept.
Motion of Inclusion Induced by a Direct Current and a Temperature Gradient
Authors: Ho Paul S.
Published: February 2004

We have analyzed the migration of spherical and cylindrical inclusions under a direct current and a thermal gradient in an infinite medium and near a planar boundary. Our study of inclusion motion in an infinite medium is concerned primarily with the application of the marker-motion technique to measure mass transport in the lattice. It is shown that, in addition to the lattice motion, there are contributions to marker movement coming from mass transport by surface and volume diffusion, which is induced by the change of potential gradient on the marker surface. To measure the true lattice velocity, the marker used must be a good insulator compared to the matrix material, and its size should exceed a few microns. The study of inclusion motion near a boundary is for analyzing pore migration by electromigration in thin films. Three cases have been considered, which include a spherical pore near a plane and between two planes and a cylindrical pore connected to two planes. We concluded that the pore migration in the lattice is due to surface electromigration and the planar boundary generally increases pore velocity and distorts its shape during migration.
X-Ray Diffraction from a Binary Diffusion Zone
Authors: Houska C. R.
Published: February 2004

Prior treatments of the scattered x-ray intensity from diffusion zones in two component crystalline systems lack a formal basis and tend to be intuitive in approach. Relatively simple and useful results can be obtained if the continuous composition changes are approximated by either a series of steps or by a system of linear segments. This paper develops equations for the coherent scattering from both approximations. Summing the scattering from all segments leads to the formation of intensity bands. Equations, containing an absorption correction, are given for planar diffusion zones in the micron and submicron range.
Detection of Electrode Vapor Between Plane Parallel Copper Electrodes Prior to Current Amplification and Breakdown in Vacuum
Authors: Davies D. Kenneth , Biondi Manfred A.
Published: February 2004

Simultaneous, time-resolved measurements of current growth and resonance line absorption have been made for the time intervals 0.2 and 0.8 μsec, respectively, preceding breakdown between plane-parallel copper electrodes in vacuum. These measurements have been carried out for an electrode separation of 0.1 cm and residual pressures in the low 10−9-Torr range. The experimental data show that neutral copper vapor is present in the interelectrode volume before the current increases sufficiently to produce breakdown. It is found that the vapor is generated during times of the order of some microseconds prior to breakdown, and is highly localized to the region of the subsequent spark channel. Further, the vapor density decreases from cathode to anode along the path of the subsequent spark channel. The results are consistent with a model for vacuum breakdown proposed recently in which the transient production of vapor immediately prior to breakdown occurs by the evaporation of an anode macroparticle during its transit to the cathode; amplification of the prebreakdown current in this vapor then leads to breakdown. From the data obtained in the present experiment, it appears that breakdown occurs primarily while the macroparticle is located between mid-gap and the cathode.
Imprisonment of Resonance Radiation in a Planar Gas Discharge with Reflecting Walls
Authors: Ingold J. H.
Published: February 2004

The imprisonment time of Doppler-broadened resonance radiation in a planar gas discharge is calculated numerically and compared with the analytic approximation of Walsh. This comparison shows that Walsh's results are higher than the numerical results by as much as 17% for no electronic collisional deexcitation, and by as much as 63% for copious electronic collisional deexcitation (at an optical thickness of 10). In addition, the effect of diffusely reflecting walls on the imprisonment time is calculated numerically and compared with the analytic approximation of Weinstein where possible. The numerical results are rigorously valid in the optically thick limit and approximately valid in the optically thin limit.
Electronic Band Structure and the K and L X-Ray Spectra from TiO, TiN, and TiC
Authors: Fischer David W.
Published: February 2004

The x-ray K and LIII emission bands and absorption spectra from TiO, TiN, and TiC are superimposed and compared with the calculated density-of-states histograms. For TiO the agreement is remarkably good. It is a little less good for TiC and still less for TiN, the disagreements probably being due in part to the presence of more ionicity in the bonding than was considered in the calculations. Results of the comparisons point up the importance of the transition probabilities in contributing to the x-ray spectra and can help indicate needed refinements in the calculated electronic structure.
Thermal Expansion of AlAs
Authors: Ettenberg M. , Paff R. J.
Published: February 2004

The lattice parameter of AlAs has been very accurately measured as a function of temperature between 15° and 840°C, and the coefficient of thermal expansion has been determined. The lattice parameter at 0°C is 5.6605±0.0005 Å and the coefficient of thermal expansion is (5.20±0.05) ×10−6/°C. A comparison is made to GaAs which indicates that there is a perfect lattice match at about 900°C and 0.14% lattice mismatch at room temperature.
Effects of Porosity in Powder Diffraction
Authors: Trucano P. , Batterman B. W.
Published: February 2004

A direct measure of the effect of porosity on powder diffraction intensities can be obtained by measuring the ratio of the x-ray scattering from a porous, amorphous material vs its nonporous counterpart. The amorphous specimen eliminates the effects of extinction and preferred orientation inherent in diffraction from crystalline samples. Measurements on glass powders of controlled particle size vs solid specimens were used to obtain porosity corrections for scattering angles 10°<θ<80° and for particle sizes in the range μt=1.0 to μt=3.2. With particles of the largest values of μt the error can be as great as 30% for θ≈30°. For a given specimen the correction approaches zero as θ→90° and also gets smaller as θ→0°. For specimens of about 50% relative density the maximum correction is approximately (10×μt)%. Extrapolating to particles with attenuation factors of only 10% (μt=0.1) corrections as large as 1% in a powder integrated intensity measurement may be necessary.
Calculation of Activation Volumes for Self-Diffusion and Creep at High Temperature
Authors: Sherby O. D. , Robbins J. L. , Goldberg A.
Published: February 2004

It is shown that the activation volume for diffusion or steady-state creep at high temperature (>0.5Tm) can be estimated for all crystalline solids if the crystal structure, valence, entropy of melting, and volume change on melting are known. The calculated results agree well with the available experimental data for metals and compounds. Calculations performed for a number of crystalline materials show that the activation volume is a function of the crystal structure and that negative activation volumes are obtained for those materials that contract on melting. These results suggest that diffusion in the solid state occurs by a mechanism similar to the ``relaxion'' mechanism as originally proposed by Nachtrieb and Handler. In our proposed model the thermally activated process in diffusion involves the cooperative formation of a liquid-like cluster of atoms surrounding a vacant lattice site. Such a model predicts negative activation volumes and satisfactorily explains the influence of different crystal structures on the magnitude of the activation volume obtained.
Segregation of Zinc to Vacancy Sinks in Aluminum
Authors: Anthony T. R.
Published: February 2004

During air cooling from a high-temperature anneal, vacancy currents were observed to cause zinc to segregate around vacancy precipitate cavities in aluminum. From the vacancy and zinc impurity currents directly measured in this experiment, a maximum value of the ratio of vacancy jump frequencies away from and around a zinc impurity atom in aluminum is determined. This limiting ratio suggests a small attractive interaction between a vacancy and a zinc impurity and/or an increase in the jump frequency of aluminum atoms around the undersized zinc atom. The segregation that would be produced around grain-boundary vacancy sinks during quenching and irradiation was computed from the experimental values of the ratio of the vacancy current and the vacancy-generated impurity current measured in this and other experiments. It was found that moderate and very large changes in grain-boundary solute concentration could be expected during quenching and irradiation, respectively.
Axially Symmetric Eddy Currents in a Spherical Conductor
Authors: Luquire J. W. , Deeds W. E. , Dodd C. V.
Published: February 2004

The general theory for the vector potential produced by a sinusoidal current of finite cross section is developed and applied to a coil encircling two concentric, spherical shells of finite electrical conductivities and permeabilities. Linear, isotropic, and homogeneous media are assumed throughout the analysis. First, the Green's function solution is obtained, and then the principle of superposition is used to effect the desired result. A number of physically observable phenomena—such as the impedance, the power loss due to the presence of the conductors, and the time-averaged electromagnetic force on the conductors—are subsequently calculated from the vector potential. The treatment is sufficiently general to allow the solution of a number of difficult problems of electromagnetic induction, while each of the expressions obtained for the physically observable phenomena is in terms of an infinite sum that may be readily evaluated on a computer.
Trichel Streamers and Their Transition into the Pulseless Glow Discharge
Authors: Giao Trinh N. , Jordan J. B.
Published: February 2004

Trichel streamers and their transition into a negative pulseless glow were investigated by simultaneous recordings of the discharge current and light emission. Both the streamer and the glow modes of discharges have been found to develop in parallel at low cathode potentials. The transition to a pulseless glow mode depends upon the quenching effect of the ion space charge in particular field conditions. Critical values of the repetition rate of Trichel streamers were found to depend on the electrode slenderness and also on the resistance of the cathode to ion bombardment. Practically, a repetition rate exceeding 10 MHz is difficult to obtain under normal atmospheric conditions because of the rapid cathode deterioration.
Elasticoviscous Boundary Layer Flows with Suction
Authors: Shrestha G. M.
Published: February 2004

The classical boundary layer theory is extended for an elasticoviscous fluid flow over porous boundary. A method is developed from which the results for the stagnation flow, the flow along a flat plate, etc. can be derived as special cases. The flow near a stagnation point is considered in detail. It is found that the main effect of suction is to increase the velocity in the elasticoviscous boundary layer and to decrease the stress on the boundary.
Decay of Static Electrification by Conduction Processes in Polyethylene
Authors: Wintle H. J.
Published: February 2004

The theory of the transfer of charge from an electrified surface layer through the bulk of a dielectric is developed for transient space-charge-limited current conditions. The modifications required when conduction is included and when diffusion is included are indicated. Comparison with published data for polyethylene indicates carrier mobilities of the order of 10−11 cm2 V−1 sec−1 at room temperature.
Approximate Lasing Condition
Authors: Marlow W. C.
Published: February 2004

The system of coupled kinetic rate equations and radiative transfer equations governing an optically active medium is considered, and an approximate lasing condition is established. The lasing condition and the rate equations then form a complete set of equations from which the population densities and radiation energy density can be determined without recourse to the more complicated radiation transfer equations. In this approximation the final expression for the laser power output is found to be identical with the exact solution.
HCl, HF, and DF Partially Inverted cw Chemical Lasers
Authors: Cool Terrill A. , Stephens Ronald R. , Shirley John A.
Published: February 2004

Continuous-wave chemical-laser operation has been achieved at wavelengths from 2.7 to 4.0 μ from partially inverted P-branch transitions of HCl, HF, and DF product molecules in a subsonic flow system. Several simple three-body atom-exchange reactions of the type extensively studied by Polanyi and co-workers have been employed here. Selective laser oscillation on individual vibration-rotation transitions was accomplished by means of a tunable cavity with a diffraction grating as a dispersing element. Performance comparisons are made between the present partially inverted lasers and the totally inverted HF–CO2, DF–CO2, HCl–CO2, and HBr–CO2 cw chemical lasers we have previously studied using the same chemical reactions.
Thin-Film Superconductors as Sensitive Thermometers
Authors: Liebenberg D. H. , Allen L. D. F.
Published: February 2004

Thin films of granular aluminum operated in the resistive transition region to the superconducting state have been used to measure temperatures to an accuracy of ±3 m°K and to a sensitivity of better than 10−5 °K. The stability of the film has been determined and the film has been calibrated on the 1958 T scale. A film of ``staircase'' construction has been used to extend the temperature range of these films without loss of sensitivity.
Absorption of Electron Kinetic Energy by Inorganic Phosphors
Authors: Meyer Vincent D.
Published: February 2004

The fraction of the incident energy not absorbed by a phosphor has been determined by measuring the rediffusion coefficient and the energy distribution of backscattered electrons. Measurements for single crystals and powder samples have shown that a large fraction of the electrons scattered back from powder samples have undergone multiple backscattering, resulting in a reduction in the rediffusion coefficient. New estimates of the maximum attainable cathodoluminescence efficiency of ZnS:Ag have been made.
Acoustic and Electromagnetic Double Resonance in Iron-Doped Corundum
Authors: Lewiner J. , Meijer P. H. E. , Lally J. F. , Meister R.
Published: February 2004

A systematical investigation of the possibilities for a combined electron paramagnetic resonance (EPR) and acoustical paramagnetic resonance (APR) experiment was undertaken. The working substance was Fe3+-doped Al2O3. The EPR frequency was 12 140 MHz and the APR frequency was 9366 MHz. From experimental data and theoretical prediction we established the values of the parameters (field strength and direction) for which double resonance should be possible. The two most important configurations were investigated. The angle between the c axis of the crystal and the magnetic field was called θ. For θ=41° and H=485 Oe a normal saturation effect was observed by pumping the 1–3 EPR transition and looking at the 2–3 ultrasonic transition. The relative change in the measured attenuation of the sound is about 30% and is explained by an approximate solution of the rate equations. In the other possible configurations (θ=47° and H=495 Oe) we were not able to observe an expected amplification because of the extreme sensitivity needed for this experiment. The ``antisaturation'' effect reported by Kagan et al. was not observed.
Magnetism in Austenitic Stainless Steels
Authors: Flansburg L. D. , Hershkowitz N.
Published: February 2004

Mössbauer-effect measurements of the temperature dependence of the hyperfine field for several austentic stainless steels are reported. Antiferromagnetic transitions were observed for all specimens in the temperature range below 56°K. In addition, a broadening of the single linewidth occurred for each specimen at a temperature near its transition temperature. The transition temperature is interpreted to be a measure of the Néel temperature of antiferromagnetic γ-phase iron.
Spin-Wave Relaxation in High-Magnetization Materials
Authors: Bartkowski R. R.
Published: February 2004

In materials with a high magnetization, spin-wave-relaxation processes associated with the dipolar interactions will be very strong. The general features of these interactions are discussed in relation to various parameters of the problem. In particular the three-spin-wave splitting process is treated in the long-wave-length or low-wave-vector k limit, and results are presented for this case. Because of the complexity of the final expression the results are presented as an integral which is easily evaluated numerically. This expression gives a value for the linewidth contribution of this process in the low-k portion of the spin-wave spectrum.
Magnetic Properties of Amorphous Pd–Si Alloys Containing Iron
Authors: Hasegawa Ryusuke
Published: February 2004

Magnetic properties of amorphous FexPd80−xSi20 alloys (x=0.5–7) obtained by rapid quenching from the liquid state are studied between 1.5° and 300°K and in fields up to 8.40 kOe. The amorphous alloys are paramagnetic above the characteristic temperature Td. The observed magnetic moments can be explained by postulating a simple magnetic domain consisting of one Fe atom and its Pd nearest neighbors. This is consistent with the magnetic moments assigned to each Fe atom (μFe=3.0μB) and to each Pd atom (μPd=0.20μB). Below Td superparamagnetic clusters exist in the amorphous alloys. Ferromagnetism is found in amorphous Fe7Pd73Si20 alloys with a Curie temperature of 28°K. Evidence is discussed which demonstrates that the d-d spin exchange interaction is weaker in the amorphous alloys than in the corresponding crystalline alloys.
Linear Compressibilities of II-VI Compound Single Crystals
Authors: Montalvo R. A. , Langer D. W.
Published: February 2004

The isothermal linear compressibilities of the II-VI compound single crystals, CdS, CdSe, CdTe, ZnO, ZnS, ZnSe, and ZnTe were measured by an optical interferometer. The change in length of the crystals was obtained relative to iron under hydrostatic pressures between 1 and 10 kbar. A method was devised to measure small gaps to a fraction of a micron at room pressure to obtain the initial parameters of the interferometer.
Repetitively Q-Switched Nd:YAlG–LiIO3 0.53-μ Harmonic Source
Authors: Chesler R. B. , Karr M. A. , Geusic J. E.
Published: February 2004

LiIO3 placed inside the cavity of an acousto-optically Q-switched, tungsten-pumped Nd:YAlG laser has been employed to generate kilohertz repetition rate pulses at 0.532 μ. The peak output power of 855 W obtained in the TEM00 mode at a repetition rate of 1 kHz was about 1.5 times greater than that available from the same laser at the fundamental laser wavelength, 1.064 μ. Volume damage occurred in the LiIO3 typically after several hours of operation at 1 kHz, an improvement over Ba2NaNb5O15.
Ellipsometric Technique for Obtaining Substrate Optical Constants
Authors: Shewchun J. , Rowe E. C.
Published: February 2004

A method for determining substrate optical constants, surface film thickness, and surface film optical constants has been devised by measuring the ellipsometer angles Δ and ψ at several angles of incidence. This method, previously reported as impossible, solves in a simple fashion the ellipsometry equations for one consistent values of surface film thickness in association with compatible values of substrate optical constants. The technique is advantageous in that vacuum ellipsometry is eliminated and previously unmeasured materials such as alloy structures may be studied readily. Data on aluminum, molybdenum, and silicon are presented illustrating the technique.
Elastic Anomaly of Ba2NaNb5O15
Authors: Yamada Tomoaki , Iwasaki Hiroshi , Niizeki Nobukazu
Published: February 2004

The temperature characteristics of elastic, piezoelectric, dielectric, and optical constants of Ba2NaNb5O15 have been measured from room temperature up to the Curie point. The shear elastic compliance related to the tetragonal principal axes (TS66) is found to become large near the transition point from tetragonal to orthorhombic phase. A phenomenological approach is tried, in which the free energy is expanded in power series of the polarization and strain, and it becomes clear that this tetragonal-orthorhombic transition is little dependent of the behavior of spontaneous polarization but that elastic instability is the main cause of this phase transition. The elastic, piezoelectric, dielectric, and optical constants in the orthorhombic phase are derived from the constants in the tetragonal phase by the biased effect of the spontaneous shear strain to the elastic higher-order terms in the free energy.
Quantum Efficiency and Photoconductivity in Dye-Sensitized ZnO-Resin Binder Layers
Authors: Comizzoli Robert B.
Published: February 2004

Measurements of quantum efficiency and photoconductivity on dye-sensitized ZnO powder-organic-resin binder layers as used in electrophotography show that the carrier range for dye-sensitized photocurrents is 10 to 100 times lower than that for the intrinsic ZnO photocurrent at 3800 Å. The dye-sensitized photocurrent depends on the square root of light intensity while the photocurrent at 3800 Å is linear with intensity. These observations are interpreted in terms of a bimolecular recombination process for the dye-sensitized photocurrent in which a photoexcited dye molecule injects an electron into the ZnO conduction band and then recaptures ZnO conduction electrons to return to the ground state.
Planar Resonance Probe in a Free Molecular Arc-Heated Flowing Plasma
Authors: Bunyan James L.
Published: February 2004

A shift in the measured frequency position of the current minimum drawn by a resonance probe near the plasma frequency is shown to be caused by a difference in ion and electron directed velocities in a low-density arc-heated wind tunnel.
High-Speed (4–6 cm/ μsec) Gas-Jet Propagation
Authors: Glenn H. David , Crowley Barbara K.
Published: February 2004

A gas-jet experiment was conducted using a Voitenko compressor to deposit approximately 7×1013 erg of energy into 27.5 g of air. This high-energy gas or plasma jetted down a 2-cm-i.d. 350-cm-long steel exit pipe containing air initially at a pressure of 20 μ of mercury. The jet structure was composed of a 5.5-cm/μsec low-density (<5×10−5 g/cm3) peak followed by a ∼4-cm/μsec higher-density (∼3×10−3 g/cm3) peak. Both peaks appear to attenuate to a terminal or steady-state velocity of 2.4 cm/μsec near the end of the pipe. Brightness temperature and pressure profiles are obtained at specific locations over the first 100 cm. To correlate the pressure-temperature results, a two-dimensional jet configuration is suggested. A maximum brightness temperature of 93 000°K was measured for the plasma jet as it started down the exit pipe.
Tables of Interaction Parameters for Computation of Ohm's Law Coefficients in Various Gases
Authors: Argyropoulos G. S. , Casteel M. A.
Published: February 2004

The coefficients of Ohm's law in multicomponent, nonisothermal phasmas can be computed accurately and with minimum complication if three electron-neutral interaction parameters are known as functions of the electron temperature: the ``effective'' collision cross section for momentum transfer Qek, and the weighting factors Aek(2) and Aek(5). Tables of these parameters are given here in the range 1000≤Te≤ 18 000°K for A, Xe, He, CO2, CO, N2, O2, H2O, NO, and Kr.
Enhanced Diffusion and Out-Diffusion in Ion-Implanted Silicon
Authors: Meyer O. , Mayer J. W.
Published: February 2004

Backscattering and channeling-effect measurements were used to determine the lattice disorder and distribution, lattice location, and diffusion of species (Rb, Cs, Zn, Cd, Hg, Se, I, and Sb) implanted in Si. During anneal sequences we observed (1) enhanced diffusion towards the surface (Sb, Se, and Cd), (2) retardation or precipitation at the surface (Sb, Se, and Cd), and (3) a connection between out-diffusion and reordering of the amorphous layer (Zn, Cd, Hg, and I). The data also suggest that release of atoms from trapping (precipitation) sites in the implanted layer can be the rate-limiting process in some cases. These results indicate that out-diffusion studies such as gas release, may not represent bulk diffusion properties in crystals.
Measurements of the Thermal-Emission Rates of Electrons and Holes at the Gold Centers in Silicon Using the Small-Signal-Pulsed Field Effect
Authors: Sato S. , Sah C. T.
Published: February 2004

The small-signal-pulsed field effect in the surface-space-charge region of a metal-oxide-semiconductor field-effect transistor structure is developed to investigate the properties of gold impurity in the surface region of silicon. Thermal-emission rates of electrons and holes and their thermal-activation energies at both the gold-donor and -acceptor states are obtained. At 300°K the low-field thermal-emission rates are ep0t+en1t=680/sec at the gold-acceptor center and ep−1t=1.2×107/sec at the gold-donor center. Thermal-activation energy of these emission rates was observed in the range of 216°–370°K for the acceptor center giving EC-EAu-=0.54 eV and in the range of 130°–235°K for the donor center giving EAu+-EV=0.34 eV. The field dependences of the thermal-emission rate and the spatial distribution of gold concentration in the surface-space-charge region of up to 1-μ wide are observed, indicating a pileup of gold at the interface in phosphorus-diffused n-channel devices.
Comparison of Theoretical with Experimental p-n Junction Recombination Effects
Authors: Wilson Charles L. , Brient S. John
Published: February 2004

The current-voltage characteristics of an inhomogeneously doped p-n junction have been calculated using full Shockley-Read statistics. The equations solved include calculation of the minimal lifetimes from an inhomogeneous flaw distribution and the appropriate capture cross sections. When Poisson's equation and the hole and electron continuity equations are solved numerically, the injection parameter for the junction is found to be current dependent. When flaw densities and capture cross sections are adjusted to fit experimental measurements, the resulting minimal lifetimes are much shorter than those usually considered in the literature. This discrepancy is explained by the restriction of the recombination process to the depletion regions and the absence of recombination in the quasineutral regions of the device.
Spontaneous and Stimulated Carrier Lifetime (77°K) in a High-Purity, Surface-Free GaAs Epitaxial Layer
Authors: Dapkus P. D. , Holonyak N. , Burnham R. D. , Keune D. L. , Burd J. W. , Lawley K. L. , Walline R. E.
Published: February 2004

A simple optical transmission and excitation technique is demonstrated for the measurement of extremely short excess carrier lifetimes in GaAs. The middle layer of an epitaxial n+/n/n+ sample, in which excess carriers tend to be confined to the center of the structure, is selectively excited optically and serves essentially as a surface-free sample that exhibits the recombination properties intrinsic to bulk material. Excited from lower to higher level (77°K), this layer (Nd∼2−3×1015/cm3, μ=6340 cm2/V sec) varies continuously in carrier lifetime from τ≈10−9 sec (spontaneous recombination) to τ≈2×10−10 sec (stimulated recombination), as determined by the measured change in sample absorption caused by Burstein shift of the carrier quasi-Fermi levels (carrier population). The carrier distribution and generation rate are shown to be quite uniform within the sample as a result of the inverse dependence of the absorption upon the carrier concentration.
Method for Determining Capture-Probability Temperature Dependences in Semiconductors
Authors: Srour J. R. , Curtis O. L.
Published: February 2004

A method is presented for determining recombination-center capture-probability temperature dependences in semiconductors. Simple relationships which yield these dependences without knowledge of the recombination-center energy-level position are obtained for the case of asymmetric electron and hole capture probabilities, a commonly encountered situation in practice. The method involves the measurement of both minority carrier lifetime versus excess carrier density (with temperature as a parameter) and minority carrier lifetime versus temperature at low excess density. The technique presented has proven useful in radiation effects studies, and examples are given to illustrate the method for this application.
Field-Effect Measurements on the HgCdTe Surface
Authors: Tasch A. F. , Chapman R. A. , Breazeale B. H.
Published: February 2004

Measurements of capacitance, dc surface conductance, and photoconductivity vs fieldplate voltage on metal-insulator-semiconductor (MIS) structures on 0.09-eV bandgap HgCdTe are reported. Surface-state density, effective surface charge, and field-effect mobilities for electrons and holes are obtained and discussed. Below 100°K the electron field-effect mobility is relatively high, and the field-effect mobility ratio is comparable to the mobility ratio in bulk material.
Shock-Wave Studies of PMMA, Fused Silica, and Sapphire
Authors: Barker L. M. , Hollenbach R. E.
Published: February 2004

The shock-wave propagation characteristics of polymethyl methacrylate (PMMA), fused silica, and sapphire were measured for both compressive and rarefaction waves using plate-impact experiments and interferometer instrumentation techniques. The peak stress levels in the experiments were 22, 65, and 120 kbar, respectively. The high-resolution measurements of the stress wave profiles showed the PMMA to be a complex material whose wave propagation is influenced by nonlinearity, strain-rate dependence, and elastic-plastic effects in which plastic working increases the zero-pressure volume of the material. The fused silica is very well characterized as a nonlinear elastic material having the interesting property of propagating stable rarefaction shock waves. The sapphire was nearly linear elastic to 120 kbar. The use of these three transparent materials as ``windows'' in laser interferometer instrumented shock-wave studies of other materials is discussed. The effect of the shock-induced variation of the index of refraction on the interferometer data was also measured and is presented.
Disclination Loops in Polymers
Authors: Li J. C. M. , Gilman J. J.
Published: February 2004

Similar to the dislocations in polymers caused by chain displacement, disclinations are caused by chain kinking and twisting. Two simple kinds are considered, a twist disclination loop (due to chain twisting) and a wedge disclination loop (due to chain kinking). Their elastic properties are given including displacements, strain and stress fields, and strain energies. Some of their features are compared with those of dislocation loops. The role of disclination loops in the mechanical behavior of polymers is discussed.
Light Scattering by Anisotropic Shells
Authors: Sundararajan P. R. , Marchessault R. H.
Published: February 2004

Solid-state light scattering using a red laser source has been applied to the study of spherulitic shells of polyethylene and gelatin. The Hv scattering patterns from a collection of shells are qualitatively similar to that of a spherulite. However a single shell gives a scattering pattern wherein several orders of maxima within the recordable range are visible. The relative intensity of the higher-order maxima depends on the thickness of the shell. Theoretical scattering patterns have been calculated and are in general agreement with the experimental observation.
Glass Transition of Atactic Polystyrene by Ortho-Positronium Decay
Authors: Stevens J. R. , Mao A. C.
Published: February 2004

In solid polymers the mean lifetime τ2 of ortho-positronium annihilating by pickoff depends upon the free volume. τ2 has been measured for five samples of relatively monodisperse atactic polystyrene over a temperature range from room temperature to 120°C. The number average molecular weight of the samples ranged from 50 100 to 640 000. For each sample the variation of τ2 with temperature indicated a glass transition about 13 deg below that measured on a differential scanning colorimeter. An increase in the glass transition temperature with molecular weight was observed. The τ2 lifetime, which depends upon the overlap of the positron component of the ortho-positronium atom with the lattice wavefunction, seems to be very sensitive to the cooperative motion about the chain axis which is associated with the glass transition.
Paracrystalline Structure of Polymer-Crystal Lattice Distortion Induced by Electron Irradiation
Authors: Nagasawa Toshio , Kobayashi Keinosuke
Published: February 2004

The melting temperature of polyethylene crystals decreases and the lattice constants (both a and b) and lattice distortion increase, but the macroscopic volume of the specimen does not change with electron irradiation. From these results a model of a deformed lattice structure with point defects produced by irradiation is proposed. Calculations indicate that the anisotropy of a polymer crystal (difference between the elastic modulus along the molecular axis and perpendicular to the axis) increases the range of the distortion in a crystal caused by a defect. The presence of lattice distortion in electron irradiated polymer single crystals produces observable features in the Moiré patterns obtained from the crystals.
Orientation and Structure of Polyethylene Crystallized under the Orientation and Pressure Effects of a Pressure Capillary Viscometer
Authors: Desper C. Richard , Southern John H. , Ulrich Robert D. , Porter Roger S.
Published: February 2004

A commercial high-density polyethylene has been crystallized in the Instron Capillary Rheometer under the combined influence of pressure and orientation. A transparent high-modulus, and highly oriented filament structure was produced. In order to determine quantitatively the degree of orientation, azimuthal x-ray scans of the 002 reflection plane were used to obtain the orientation function of the orthorhombic unit cell relative to the flow axis in the rheometer (identified with the filament axis). A value of +0.996±0.002 was measured for this orientation function indicating that the backbones of the crystalline polyethylene chains were virtually aligned perfectly parallel to the flow axis of the rheometer. This report is concerned with the high-resolution techniques required to measure such highly oriented samples. In conjunction with the x-ray study, birefringence measurements are included which permit the determination of the orientation of the amorphous component as well as the crystalline component.