bluuebunny/crossref_metadata_2025_split huggingface dataset:
Propagation of Piezoelectric and Elastic Surface Waves on the Basal Plane of Hexagonal Piezoelectric Crystals
Authors: Tseng Chin-Chong , White R. M. 
Published: January 2005

Propagation of piezoelectric and elastic surface waves on the basal plane of hexagonal piezoelectric crystals has been investigated theoretically. Variations of the piezoelectric field and the particle displacement with the distance from the surface have been derived and compared with Stoneley's result for nonpiezoelectric crystals.
The results are applied to hexagonal CdSe, CdS, and ZnO. For CdSe and CdS, the surface waves are pure Rayleigh modes. However, for ZnO which has relatively large piezoelectric coupling coefficients, the surface waves are found to have the form of a general surface wave defined by Synge. Velocities of surface waves propagating on the basal plane of CdSe, CdS, and ZnO are computed to be 1.470×105, 1.7306×105, and 2.70×105 cm/sec, respectively, which are in good agreement with measured values.
Effect of Hydrostatic Pressure on Dislocation Mobility in Lithium Fluoride
Authors: Hanafee J. E. , Radcliffe S. V. 
Published: January 2005

The effects of hydrostatic pressures up to 13 kbar on the stress dependence of the velocity of screw dislocations in single crystals of lithium fluoride at room temperature have been determined. The shear stresses to move the dislocations were introduced by means of a three-point bending device incorporating a load-cell and operated entirely within a fluid medium at constant pressure and temperature. The range of velocities observed was from 10−5 to 10−2 cm/sec. Both high-purity and impurity-doped crystals were studied.
At all the pressures examined, the dislocation velocity was found to vary with the applied shear stress τ in accordance with the empirical relationship v = v*·e−A/τ (where v* is a terminal velocity and A is a drag stress) suggested by Gilman for one-atmosphere behavior. However, the stress required to move a dislocation at a given velocity in increases rapidly with pressure, by a factor of approximately 3 at 10 kbar. Correspondingly, the dislocation velocity at constant applied shear stress decreases by several orders of magnitude. Based on the magnitudes of the activation volume measured for the high-purity and doped crystals, the effects are interpreted in terms o the mobility of jogs as the mechanism controlling dislocation velocity at pressure.
The measured decrease in dislocation mobility has been used to compute the expected change in stress—strain behavior in LiF as a function of pressure.
Secondary-Electron Emission from Glycerol-Coated Copper Surfaces
Authors: Gill J. J. , Hendricks C. D. 
Published: January 2005

This paper reports the results of an experimental determination of the secondary-emission characteristics of glycerol layers on copper surfaces. This work has as its motivation the use of glycerol as a working fluid in electric thrustors for spacecraft.
Secondary-emission coefficients for glycerol are reported as a function of incident primary-electron energy. Primary-electron energy was varied from 200–900 eV and glycerol secondary-emission coefficients were found to vary from 2.5 to about 1.0. These results are compared with values for clean copper surfaces found by using the same apparatus.
Phase-Matched Second-Harmonic Generation in Biaxial Crystals
Authors: Hobden M. V. 
Published: January 2005

The allowed directions for phase-matched second-harmonic generation in acentric biaxial crystals are obtained by considering the intersections of the index surfaces at the fundamental and harmonic frequencies; the topology of these intersections is determined by the principal refractive indices. There are thirteen distinguishable cases for optically well-behaved biaxial crystals and the phase-matching directions for them are shown as loci on the stereographic projection. Phase-matching that is insensitive to small changes in the direction of propagation is possible when some principal refractive indices are equal; the mismatch of the wave vectors is given for deviations from the phase-matching direction in such cases. The disposition of the principal axes of the optical indicatrix and the symmetry of the point groups C2v, D2, Cs, C2, and C1 are examined to find those situations which have a nonzero element in the second-order polarizability tensor that will give second-harmonic generation.
Phase-matched second-harmonic generation experiments in the biaxial crystals dipotassium tartrate, lithium sulfate and ammonium oxalate demonstrate some of the possible phase-matching situations.
Effect of Hydrostatic Pressure on p-n Junction Characteristics and the Pressure Variation of the Band Gap
Authors: Jayaraman A. , Sikorski M. E. , Irvin J. C. , Yates G. H. 
Published: January 2005

The effect of hydrostatic pressure on p-n junctions of Si and GaAs in which both ideal and generation-recombination currents were present has been investigated. It is shown that the pressure coefficients of the energy gap can be obtained directly from the pressure-induced shifts in the forward-bias voltage, measured at a constant total junction current. Presently determined pressure coefficients of −1.5±0.005×10−3 eV/kbar for Si and 10.9±0.1×103 eV/kbar for GaAs are in good agreement with values obtained for Si and GaAs by other methods. In the case of GaAs, the pressure-induced shift in the forward-bias voltage reverses sign when the conduction-band minimum shifts (to the [100] valleys) at high pressure.
The effect of pressure on the reverse breakdown voltage for Si junctions has also been determined. The results seem to offer some support to the theory of Hauser and Wortman.
Comparison of Langmuir Probe and Microwave Diagnostic Techniques
Authors: Graf K. A. , De Leeuw J. H. 
Published: January 2005

Electron densities have been measured in the subsonic portion of a free-expansion argon jet by microwave and Langmuir-probe methods. Microwave phase-shift measurements were made with an interferometer in such a way that the spatial variation of electron density could be determined. The data were analyzed with a ray-tracing technique.
Langmuir-probe measurements were made with cylindrical and flat probes under essentially collision-free conditions, and over a range of probe radius to Debye length ratios of about 10–50. Both electron and ion collection were measured and analyzed. Three methods of analyzing the electron-current part of the characteristic were compared. It was found that one method gave values two or three times higher than another method. The discrepancy was due to the failure of the experimental Langmuir-probe characteristic to follow the theoretical one in the vicinity of plasma potential: the so-called ``knee'' of the curve. This difficulty has been overcome by analyzing the data with the aid of theoretical particle-collection curves.
Single-Crystal Elastic Properties of Tungsten from 24° to 1800°C
Authors: Lowrie Robert , Gonas A. M. 
Published: January 2005

The velocities of ultrasonic shear and compressional waves in tungsten crystals have been measured in several directions and as functions of temperature to 1800°C. Adiabatic crystal elastic stiffnesses have been calculated from these velocities as follows: C11=5.2349×1012−4.5967×108T−5.467×104T2±0.25% dyn·cm−2C44=1.6028×1012−1.0320×108T−2.054×104T2±0.25% dyn·cm−2CN=5.2480×1012−3.5005×108T−3.163×104T2±0.25% dyn·cm−2C12=2.0445×1012−0.3403×108T+3.249×104T2±2.3% dyn·cm−2C′=1.5952×102 −2.1282×108T−4.358×104T2±1.8% dyn·cm−2.
Values for the elastic constants of random, polycrystalline tungsten were calculated from these crystal stiffnesses. They agree well with values determined on polycrystalline tungsten as functions of temperature.
Controlled Crystalline Orientation of Sputtered Ferromagnetic Films on Amorphous Substrates
Authors: Larson H. W. , Walker G. A. 
Published: January 2005

The effects of thermionic sputtering parameters on crystalline orientation and coercive force of magnetic films are discussed in this paper. By controlling the crystalline orientation within the film it is possible to produce films with a coercive-force range from 0.9 Oe to 35.8 Oe. The crystalline orientation is controlled by the magnetic field, the electric field, and the substrate position within the apparatus. All of the films were prepared on substrates which were not exposed to the sputtered material until the target had the adsorbed gases removed.
The texture of the films is described by means of several x-ray photographs taken on a specially designed Laue camera, capable of giving a pattern from films as thin as 100 Å.
Studies of Cataphoresis and Electrophoresis—Some New Effects
Authors: Kenty Carl 
Published: January 2005

A study is made of the rate of transport of Hg in a uniform positive column in a mixture of a rare gas and Hg vapor. In one case, the phenomenon of retrograde cataphoresis is encountered, that of Xe+Hg at currents above 1 A, in which the Hg is carried to the anode end of the tube. In all other cases, the Hg is transported to the cathode end.
A pulsating discharge is described in which the color changes from the red of Ne to the blue-white of Hg and back again within a period of 1–2 sec. The boundary between the two colors travels along as a wave motion. This phenomenon is related to the properties of the tube walls and the nature of the ions striking them.
When an ac discharge is passed through a cataphoretic mixture, the trace gas of lower ionizing potential is urged from the ends toward the center of the tube, e.g., Hg in Ar, Ne and Kr, but from the center to the ends in He+Hg. With a trace of Ar in He, the Ar is urged toward the center of the lamp. With Xe+Hg, the Hg may go either to the center or to the ends, depending upon conditions. The phenomenon is believed to be due to traveling striations which start out from the anode and progress only part way toward the cathode. Such a striated discharge pumps Hg faster than a steady discharge in the case of Ar, Kr, and Ne, but apparently slower in the case of He.
Attempts to demonstrate electrophoretic effects in a straight sealed-off tube failed. However, the positive pressure effects are quite striking in a tube with an external return path.
Inertial-Electrostatic Confinement of Ionized Fusion Gases
Authors: Hirsch Robert L. 
Published: January 2005

The nonmagnetic, inertial-electrostatic confinement of ionized gases in spherical geometry is discussed theoretically, and associated experiments are described. Assuming monoenergetic ion and electron distribution functions, the Poisson equation for bipolar currents is solved numerically. The results indicate spatially periodic solutions which respresent the alternate formation of virtual anodes and virtual cathodes. Particle pressures are found to vary approximately as the inverse square of the radius and extremely high electric fields are indicated. Near the center of the spherical cavity, there exists a high-density, high-energy region, which may be of controlled fusion interest.
The experimental apparatus consists of a hollow spherical cathode concentrically placed within a spherical anode on which six ion guns are located. Steady, reproducible operation up to −150 kV and 60 mA yields a copious neutron emission, a part of which originates from a luminous spherical region within the cathode. After crowbar of the main power supply, approximately 1016 particles are released from within the cathode. This number is significantly greater than the 1012−1014 ions/cm−3 calculated from the fusion rate. The difference is attributed to the formation of two or more virtual anodes. A bremsstrahlung collimation study indicates a spatially periodic emission pattern, suggesting the formation of at least two virtual anodes, the outer of which is about 2.5 cm in diameter. No instabilities have been observed.
Electronic Theory of Adhesion
Authors: Derjaguin B. V. , Smilga V. P. 
Published: January 2005

A consistent electronic theory of adhesion is developed relating to the contact of bodies of different nature.
The strength (as well as energy) of adhesion is calculated for the contact of crystal bodies (semiconductors, metals) as well as for the contact of amorphous bodies whose surface is saturated by donor and acceptor functional groups. The theory developed allows us to calculate the electrostatic component, when certain (experimentally determined) physiochemical characteristics of studied objects are known. The theory also determines the temperature dependence of the adhesion strength. The main inference is that cases of electrostatic component reading values of the order of 108−109 (dyn/cm2) are fairly realistic. There follows from the theory the role of surface conditions as the chief factor of high adhesion. The theory suggests the ways for conditioning the adhesion via chemical modification of the surfaces (sometimes also of the bulk) of contacting bodies, and indicates which characteristics of solid bodies are to be studied when investigating the adhesion.
Wave Excitation in Compressible Plasma and Equivalence Relations
Authors: Wu Yung-Kuang , Chu Chiao-Min 
Published: January 2005

A general, unified solution of the wave excitation due to electric-current sources, magnetic-current sources, fluid-flux sources, and mechanical-body sources in a compressible plasma which may be anisotropic and inhomogeneous is presented. The Maxwell—Euler equations are reformulated through linear operator and generalized transform techniques into an equivalent matrix integral equation. The dispersion relation can be obtained from the kernel of the integral equation. When the medium is homogeneous, this integral equation has an ideal kernel and the explicit solution can be easily obtained. Equivalence relations between different types of sources are obtained from the forcing function of the integral equation, which can be employed to express the field excited by one type of source in terms of the field excited by another type of source. Generalized telegraphist's equations are also derived in due course.
Some dispersion curves, and asymptotic solutions for the radiation field from a point current source oriented in the direction of a constant magnetic field, are presented in graphical form. A proper ionospheric plasma is assumed for this calculation, which combines some of the results obtained for anisotropic cold-plasma problems on the one hand and some of the results obtained for isotropic warm-plasma problems on the other hand.
Electrical Properties of Niobium-Doped Ferroelectric Pb(Zr, Sn, Ti)O3 Ceramics
Authors: Taylor G. W. 
Published: January 2005

Hysteresis loop, pulse switching, and aging measurements have been made as a function of composition, sample preparation and thickness, electrode material and size, on 24 rhombohedral ferroelectrics from the Pb0.99[(ZrxSny)1−z Tiz]0.98Nb0.02O3 ceramic family to determine their properties and usefulness for device applications.
Results show that many of these ceramics have extremely high remanent polarization, saturation polarization, loop squareness, tolerance-to-matrix-type disturb pulses, switching speed, and minimal excitation aging. The polarizations, squareness, apparent coercive field, disturb-pulse tolerance, and aging of the apparent coerive field all increase with increasing x/y. The definite dependence of the properties on z is, in general, random. Samples prepared with smooth surfaces, such as by polishing or doctor-blading, had properties approaching those of a single crystal. The observed electrode-edge effects can be explained in ceramic terms.
These materials, while retaining all the conventional advantages of ceramics, have electrical properties equal to, and in some cases, such as polarizations and disturb-pulse tolerance, superior to single-crystal ferroelectrics. These ceramics are thus very suitable for ferroelectric memory and display devices.
Electrical Properties of the Interface Region of the Ge-Si Alloyed Heterojunction
Authors: Thompson H. W. , Reenstra A. L. 
Published: January 2005

The interface transition region of the n-n germanium-silicon heterojunction is studied to determine its electrical properties and its width as a function of fabrication process variations. Ohmic contacts are made to the p-type transition region while p-n junction isolation is maintained to the n-type bulk materials.
Electrical measurements of the transition region determine conductivity and Hall coefficient over the temperature range from 77° to 273°K. Capacitance data are obtained between the transition p-layer and the n-type germanium over the same temperature range. These measurements permit determination of activation energies of the interface states within the transition region, the carrier concentration, and the carrier Hall mobility. Transition widths are shown to be of the order of microns, are shown to increase with increased interdiffusion times, and decrease with slower recrystallization rates. Data suggest a nonabrupt transition from germanium to silicon in the alloyed heterojunction.
Annealing of Hall-Mobility Changes in Electron-Irradiated Germanium
Authors: Jaworowski A. , Merski K. , Rzewuski H. , Werner Z. 
Published: January 2005

Annealing of Hall-mobility changes in n-type germanium irradiated with 1 MeV electrons at 85°K was investigated using an isochronal technique. Two annealing stages which have been reported earlier were confirmed and separated.
One stage at above 100°K is connected with ``contact'' annealing, and a second one close to 140°K is caused by bulk annealing. The latter stage corresponds to the stage found already by J. C. Pigg for gamma irradiation.
Mössbauer-Effect Study of Solid-Solution and Precipitated Fe-Rich Fe-Mo Alloys
Authors: Marcus H. L. , Fine M. E. , Schwartz L. H. 
Published: January 2005

A detailed study of the precipitation reaction in an Fe-6 at.% Mo alloy at 550° and 650°C was made using the Mössbauer effect and Young's modulus. Mössbauer spectra of Fe2Mo, Fe3Mo2, and alloys of 2.5 and 20 at.% Mo were also obtained.
The Mössbauer spectra of the Fe-base Mo solid solution were analyzed on the basis of a 14 near-neighbor model. The six peaks of the Fe spectrum in the alloy were broadened into six envelopes. These were analyzed as a superposition of three sets of peaks, one set each for Fe atoms with 0, 1, and 2 Mo atoms among the 14 near-neighbors giving in the as-quenched Fe-6 at.% Mo alloy hyperfine fields of −335±1, −296±1, and −255±2 kOe and the isomer shifts relative to pure Fe of +0.01±0.005, −0.02±0.01 and −0.05± 0.02 mm/sec, respectively.
The precipitation in the Fe-6 at.% Mo alloy at 650°C occurred by a one-step process while the 550°C aging sequence occurred by a two-stage reaction, first clustering of Mo and then precipitation. An activation of 59 kcal/mole and a rate exponent of 1.2 were determined from modulus and Mössbauer data suggesting diffusion-controlled growth of thin long platelets.
The solvus composition Cs in the temperature range 650°–870°C was found by quantitative analysis of the Mössbauer spectra to follow the empirical relation Cs = exp − (7400/RT) at.% Mo assuming the precipitate to be Fe2Mo. A mass balance ruled out Fe3Mo2 (or Fe7Mo6). The Fe2Mo precipitate was confirmed in the Fe-20 at.% Mo alloy by x-ray diffraction.
Ionic Conduction and Diffusion in Single Crystals of SrCl2
Authors: Hood G. M. , Morrison J. A. 
Published: January 2005

This paper reports the results of measurements of electrical conductivity and tracer (90Sr and 36Cl) diffusion in single crystals of SrCl2, both nominally pure and doped with the aliovalent ions Y3+ and Na+, in the temperature region 20° &lt; T &lt; 780°C. The conductivities for nominally pure crystals agree well (within a factor of 1.5) with some for a more limited range (150° to 650°C) recently published by Barsis and Taylor. Moreover, the observed effects of the addition of aliovalent impurities are similar. Some of the detailed conclusions reached are different, however.
Insofar as it can be pressed, the analysis of the data leads to the following conclusions. (i) The predominant imperfections are anionic Frenkel defects. (ii) The ionic transport is overwhelmingly anionic under all conditions. (iii) The experimental correlation factors cannot distinguish between an interstitialcy and a vacancy-transport mechanism but general considerations favor the latter. (iv) The behavior of the diffusion and conductivity at lower temperatures (T &lt; 500°C) indicates that complexes of defects form, but no detailed information is derivable.
Relaxation Phenomena in High-Resistivity Ge:Hg
Authors: Williams R. L. 
Published: January 2005

Under reduced background conditions a mercury-doped germanium photoconductor has a slow component of the response time given by the dielectric relaxation time ερ/4π. It has been shown that this is valid for small or very large signals. Further, the dielectric relaxation effects are the same whether the resistance is determined through photo-generation by background radiation or by thermal generation of holes.
The capacitance calculated from the ratio of response time to element resistance is the element capacitance for low-dislocation material. For germanium with significant lineage this parameter has a value an order of magnitude larger than theory. This indicates rather gross inhomogeneities in lifetime within the crystals. Even for the best crystals 50% of the signal has the long dielectric relaxation response time.
Trapping Effects in Drift Mobility Experiments
Authors: Tefft Wayne E. 
Published: January 2005

Theoretical expressions have been derived for the charge-distribution function and resultant voltage-decay curve applicable to drift mobility experiments in the presence of traps. The charge-distribution function was obtained under the assumption of constant electric field and the neglect of recombination and diffusion. The results are, therefore, limited to the case of low carrier densities.
The general expression for the voltage-decay curve is quite complicated, but useful approximations are made for various time regions. In addition, it is shown how the theory may be applied to the xerographic discharge mode under certain limited conditions.
Correction for Finite-Pulse-Time Effects in Very Thin Samples using the Flash Method of Measuring Thermal Diffusivity
Authors: Larson K. B. , Koyama Karl 
Published: January 2005

A method is described for eliminating errors due to the finite-pulse-time effect in the flash technique for measuring thermal diffusivity. The method depends on the employment of a mathematical model which incorporates an empirical function closely describing the actual waveform of the heat pulse produced by a flash lamp. The analytical solution obtained forms the basis of a digital computer data-reduction procedure devised for calculating the thermal diffusivity from the experimental measurements. The method of data reduction employed leads to an improvement in the precision of measurement heretofore unattainable by the flash technique. This is accomplished, in effect, by replication of the experiment through utilization of the information contained over a wide range of the temperature transient, in addition to that provided by the usual measurement of the time at which the transient reaches half-maximum.
The analysis described makes it possible to use the flash technique with samples having very small thickness-to-diameter ratios. This has the advantage of widening the range of temperatures within which heat losses may be neglected without the introduction of serious error. Experimentally, the method has been successfully tested for some very thin disk-shaped samples having axial dimensions of the order of (ατ)1/2, where α is the thermal diffusivity and τ is the duration of the pulse.