bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure and Origin of Stacking Faults in Epitaxial Silicon
Authors: Finch R. H. , Queisser H. J. , Thomas G. , Washburn J.
Published: April 2005

Light optical and transmission electron microscopy on epitaxially deposited silicon crystals in [100], [110], and [111] orientation show that growth stacking faults are formed regardless of orientation. These faults occur in bundles of usually tetrahedral figures with the apices at the substrate-film interface, and some faults may exist as closed intrinsic-extrinsic pairs. The results suggest that faults are nucleated by oxygen contamination. Some evidence for impurity segregation to faults is also presented.
A Method for Shadowing Electron-Microscopic Specimens with Tungsten
Authors: Hart Roger G.
Published: April 2005

A method is described for the controlled sublimation of tungsten wire at a temperature just below the melting point. Emission of electrons from the wire provides a sensitive indicator, which enables the operator to regulate the filament temperature by manual or automatic adjustment of the heating current.

The wire is volatilized primarily by sublimation of metallic tungsten, not by oxidation.

Some advantages of tungsten shadowing are considered.
Avalanche Effects in Silicon p—n Junctions. II. Structurally Perfect Junctions
Authors: Goetzberger A. , McDonald B. , Haitz R. H. , Scarlett R. M.
Published: April 2005

The fabrication of a planar guard ring diode which exhibits uniform microplasma-free breakdown is described. Discrepancies are discussed between the behavior of these junctions and those reported by Batdorf et al. and Chynoweth, including results showing extremely hard V-I characteristics associated with uniform avalanche breakdown. Experimental evidence is presented which confirms Shockley's theory in which the breakdown behavior is predicted from the Poisson distribution of impurities within the space-charge layer. The photomultiplication technique as described in Paper I is applied to uniform p—n junctions. The linearity of 1/M vs V, as predicted by theory, was verified for values of M between 1.6 and 500. For higher values, the multiplication curves deviate from a straight line. In this higher range they are in good agreement with the pulse-multiplication model developed in Paper I. Light emission patterns from these junctions are shown and a correlation between these patterns and crystal properties is discussed. The effects of resistivity striations in the silicon single crystals is shown to have a strong effect on breakdown areas and no effects of dislocations and oxygen on uniformity are found. From capacity and multiplication measurements a value for the breakdown field of EB=445±25 kV/cm was obtained for a 32-V junction.
Theory of Laser Regeneration Switching
Authors: Vuylsteke Arthur A.
Published: April 2005

The theory of laser regeneration switching is developed. The rate equations are derived and, using ruby as an example, the material-cavity parameters are evaluated for a 1-cm3 rod. Steady-state solutions for t<0 are given, and the equations formally integrated for t>0. Using approximate solutions, three modes of laser operation, other than the normal mode, are discussed. With the first mode: the pulsed reflection mode (PRM) switched to minimum coupling, output pulses with peak powers of 17 MW and 10 nsec duration are predicted, with 2% of the initially stored energy emitted. With the second mode: the PRM switched to critical coupling, peak powers of 170 MW with pulse durations of about 8 nsec, and with about 50% of the stored energy emitted, are predicted. In the third mode: the pulsed transmission mode (PTM), peak powers of about 900 MW, pulse durations around one nsec, with 52% of the stored energy emitted, are predicted. Experimental approaches to PTM operation are briefly discussed.
Interaction between a Dielectric (or Cold Plasma) and a Cavity
Authors: Thomassen K. I.
Published: April 2005

This paper treats the interaction between a cylindrical plasma column (or dielectric material) and a resonant cavity from which it protrudes. From the results, one may determine the dielectric constant and loss, or in the case of a plasma, the plasma frequency and collision frequency, given measured values of the resonant frequency shift and change in the cavity Q. This theory differs from earlier theory on cylindrical cavities in that it treats a cavity of more general shape, although restricted to TM modes, and takes into account the subtle boundary effects at the openings through which the plasma is admitted. These effects may be calculated by estimating the field variation over the part of the cylindrical plasma surface that lies inside the cavity.
An Anomalous Dissipation Factor Maximum in Sapphire
Authors: Tallan N. M. , Detwiler D. P.
Published: April 2005

The temperature and frequency dependencies of the dielectric properties of sapphire were determined by guarded measurements within the ranges −160° to 400°C and 102 to 104 cps. A broad dissipation factor maximum, exhibiting apparently anomalous behavior, was observed. Although the frequency at which the maximum occurred was exponentially temperature-dependent, activation energy values calculated on the basis of a dipolar relaxation model varied reversibly between 0.2 and 0.5 eV as a function of vacuum heat treatment at 400°C and of exposure to dry hydrogen, dry oxygen, or moist air. The dissipation factor behavior which would result from two alternative mechanisms, interfacial polarization and resonance, is discussed briefly on the basis of the possible existence of variable conductivity surface layers and the possible presence of hydrogen in the vicinity of dislocations.
Injection Electroluminescence in Gallium Antimonide
Authors: Calawa A. R.
Published: April 2005

Emission of high-intensity infrared radiation at 1.6 μ has been observed from forward-biased GaSb p-n junctions. Visual inspection indicates that the radiation is coming from the junction or close proximity to it. Optical pumping of the base material produces the same spectrum of radiation as p-n junction injection. Lack of significant line shift in both absorption measurements and measurements in magnetic fields up to 90 000 G indicates that the radiation is not produced by band-to-band transitions, but is probably connected with impurities. Further evidence that the transitions are via an impurity level is obtained from the fact that the radiation spectrum is changed by the addition of a different impurity.
Boron-Induced Microstrains in Dislocation-Free Silicon Crystals
Authors: Schwuttke G. H.
Published: April 2005

Dislocation-free silicon crystals, Czochralski-grown and solution-doped with boron, have been investigated by x-ray diffraction microscopy. The x-ray measurements indicate that the perfection of dislocation-free crystals can be less than that of crystals of finite dislocation density. Microstrains were found to be the dominating imperfection. Large-area topographs show diffraction contrast which is strongly reflection dependent. The topographs clearly show the presence of inhomogeneous strains confined to localized lines and planes but extending over the whole crystal cross section. The x-ray measurements suggest that boron-doped silicon contains numerous precipitates which act as strain centers. The precipitates lie on {111} planes and produce a strong warping and bending of the lattice planes.
A Model for Boundary Diffusion Controlled Creep in Polycrystalline Materials
Authors: Coble R. L.
Published: April 2005

The creep rate (ė) predicted by the boundary diffusion (Db) model is ė≃150σDbWΩ/(GS)3kT, where σ is the stress, W is the boundary width, (GS) is the average grain size, and Ω is vacancy volume. The stress dependence is the same as the lattice diffusion model, given by C. Herring, while the grain size dependence and the numerical constant are greater for boundary diffusion. Discussion of the mechanism of creep in polycrystalline alumina is based on the differences between the lattice and boundary diffusion models.
A Criterion for Exciton Binding in Dense Electron—Hole Systems—Application to Line Narrowing Observed in GaAs
Authors: Casella R. C.
Published: April 2005

When classical statistics apply, exciton binding is expected to cease when the concentration increases to the point that the Debye shielding length becomes less than the exciton radius which obtains in the absence of shielding. The statement is made more accurate by employment of Hulthén and Laurikainen's variational solutions of the Schrödinger equation for a particle acted on by an attractive central potential of the form, const×exp(−r)/r. The result is applied to recent experiments with GaAs injection lasers. It is concluded that excitons (either free or bound to impurities) do not play a role in the recombination process at high current levels. A similar criterion for binding is derived for low temperatures and applied to proposed experiments to observe line narrowing due to a Bose—Einstein condensation of excitons in CdS and CdSe. Finally, it is concluded that heavy holes do not contribute effectively to the shielding when their thermal (or Fermi) velocity is considerably less than the orbital velocity of the bound electron which obtains in the absence of shielding.
Theory of the Longitudinally Isothermal Ettingshausen Cooler
Authors: Kooi C. F. , Horst R. B. , Cuff K. F. , Hawkins S. R.
Published: April 2005

The temperature distribution T(x), maximum temperature difference ΔTmax, and coefficient of performance ε are determined for an Ettingshausen cooler of rectangular cross section when the temperature is constant in the direction of current flow (longitudinal isothermal condition). The calculation is carried out for the two cases (1) temperature-independent transport coefficients and (2) the Nernst and resistivity coefficients proportional to T−1. In both cases the expressions for ΔTmax and ε correspond closely to those for the transversely isothermal Peltier cooler while the temperature distribution differs considerably. In the longitudinally isothermal Ettingshausen cooler the electric field is constant, in the contrast to the transversely isothermal Peltier cooler, in which the current density is constant. Recognition of this fact allows the validity of the results to be established for all possible values of the figure of merit. A value of ΔTmax measured on a Bi(97)Sb(3) cooler is compared with the value determined by substitution of independently measured values of the transport coefficients into the theoretical expression for ΔTmax. Although the temperature dependence of the transport coefficients is not taken into account exactly, the agreement is good. The effect of shaping the cooler (in effect, cascading) is discussed and experimental evidence for enhancement of cooler performance due to shaping is presented.
Solubility of Zinc in Gallium Arsenide
Authors: McCaldin J. O.
Published: April 2005

The distribution of tracer zinc-65 between the vapor and solid GaAs was studied. For dilute concentrations [Zns] of zinc in the solid, the distribution coefficient K is a constant (Henry's law); at higher zinc concentrations, K falls off inversely with [Zns]. These observations can be interpreted simply in terms of an ionization equilibrium Zns → Zns−+e+. Based on this interpretation, the present measurements indicate an intrinsic carrier concentration ni of about 4×1018 cm−3 for GaAs at 1000°C. This value is roughly six times larger than ni estimated by extrapolation of Hall measurements; the latter, it is suggested, may reflect the presence of only the more mobile carriers.

The solubility of zinc was also studied as the arsenic pressure in the system was changed from the dissociation pressure (estimated 10−3 atm) to one atmosphere. The zinc solubility was observed to increase three-to fourfold with the increase in arsenic pressure. This result is in semiquantitive agreement with calculations for the mass action equilibrium of simple stoichiometric defects in GaAs.
Experiments on Mercury-Silicon Surface Barriers
Authors: Donald D. K.
Published: April 2005

Barrier heights of Si-Hg surface barriers were examined experimentally as a function of the resistivity of the silicon. The saturation reverse current and the resistance at zero bias for the diodes were measured. The simplest Schottky metal-semiconductor theory reasonably explains the resistivity-dependent behavior of ``n''-type Si. However, for ``p''-type Si a surface inversion layer is predicted if the published work functions are superposed on the simplest model. Here the resistivity dependence for the thicker barriers is less strong and the measurements more variable. The results are summarized in terms of the flat band condition (uB=uS) in units of kT/q from midband: Calculated 3±3.5. The experiments are consistent with 3±5, using no surface states to improve the fit. A Shockley surface-charge distribution ±nss≲1012/cm2 is sufficient to suit the experimental data to uB=3.

Sample treatments were ion bombardment with Hg ions, followed by submersion in Hg. Field enhanced desorption in liquid Hg was also used. Cleaved samples produced what seemed to be patchy surfaces with small regions degenerate ``p'' type.
Improved Techniques for Studying the Growth of CdS Crystals
Authors: Fochs P. D. , Lunn B.
Published: April 2005

Techniques have been developed for studying the nucleation and growth of CdS crystals on silica fibers and quartz crystals. Results show that at least one type of growth, namely a relatively fast growing (112̄0) plate habit, can be nucleated on crystalline quartz, although the actual mechanism is still in doubt. This growth habit has not so far been observed on silica fibers.
Hardening of Potassium Chloride Single Crystals by Quenching and Irradiation
Authors: Akimoto Kazou , Sibley W. A.
Published: April 2005

The effect of heat treatment and irradiation on the hardening properties of potassium chloride single crystals of varying impurity concentrations is investigated. Some specimens were quenched in cold acetone (0°C) from temperatures over the range of 100° to 650°C, and other samples were irradiated with cobalt60 photons or with 1.5-MeV electrons to doses of 1019 photons or about 3.8×1015 electrons, respectively. The quenching results are most easily explained in terms of the dissociation of vacancy-impurity complexes for temperatures to 375°C. It was not possible at the quenching rate utilized, to quench thermal vacancies in the lattice. Also, even for quench temperatures below 375°C, there is evidence that some annealing out of the defects occurred. The irradiation results show that relatively impure samples have quite different hardening properties for a given dose of irradiation, electron or gamma, than do the purer specimens.
Tensile Properties of NaCl-BaNr Solid Solution Single Crystals
Authors: Wimmer F. T. , Kobes W. , Fine M. E.
Published: April 2005

Single crystals of NaCl-NaBr alloys to 10-mole % NaBr were tested in tension. Crystals to 1-mole % NaBr were ductile but no ductility was observed with 5- and 10-mole % NaBr crystals. Addition of 0.5-mole % NaBr appeared to cause softening, perhaps due to a scavenging effect. Microhardness showed a continuous increase with NaBr to 10 mole %, perhaps due to clustering of the solute atoms. Crystals tested in methyl alcohol had lower yield stresses and were more ductile.
Generalized Formula for the Electric Tunnel Effect between Similar Electrodes Separated by a Thin Insulating Film
Authors: Simmons John G.
Published: April 2005

A formula is derived for the electric tunnel effect through a potential barrier of arbitrary shape existing in a thin insulating film. The formula is applied to a rectangular barrier with and without image forces. In the image force problem, the true image potential is considered and compared to the approximate parabolic solution derived by Holm and Kirschstein. The anomalies associated with Holm's expression for the intermediate voltage characteristic are resolved. The effect of the dielectric constant of the insulating film is discussed in detail, and it is shown that this constant affects the temperature dependence of the J-V characteristic of a tunnel junction.
Chemical Sputtering of Tungsten at Elevated Temperatures
Authors: Winters H. F. , Denison D. R. , Bills D. G. , Donaldson E. E.
Published: April 2005

Positive ions emitted from heated tungsten filaments operating in various gas environments and in residual gases remaining at 10−11 Torr have been investigated. The ions appear both as a continuous current and in the form of ion bursts. The pressure and temperature dependence of the ion current is given; the properties of the bursts are investigated; and a model for the mechanism of burst production is proposed. It is shown that the ion current can be used as a sensitive indicator of surface reactions.
Distribution of Electron-Bombardment-Induced Radiation Defects with Depth in Silicon
Authors: Flicker H. , Loferski J. J.
Published: April 2005

The electron-voltaic effect in commercial silicon p-n junctions is used to determine the distribution of radiation defects with penetration distance for a 500-keV electron beam in n-type silicon. It is shown that the concentration of radiation defects falls off far more rapidly than previously reported by Vavilov et al., who used changes in resistivity to determine the distribution. Their experimental data are reinterpreted and found to be in reasonable agreement with the electron-voltaic data. Attempts are made to explain the experimental data by constructing radiation defect vs depth curves using various relations for the probability of defect formation as a function of electron energy, and for electron energy as a function of penetration distance. Reasonable agreement exists between such theoretical curves and the experimental data.
Electrical-Charge Study in Sodium Chloride during Plastic Deformation
Authors: Hikata A. , Elbaum C. , Chick B. , Truell R.
Published: April 2005

Electrical charges developed during plastic deformation of sodium chloride were investigated. Experiments are chosen (orientation and shape of the crystals; direction of applied stress) to enable the edge and screw components of dislocation loops to emerge separately on two different pairs of the external surfaces of the specimen. The experimental results indicate that an electrical charge is associated only with the edge components of dislocation loops. It is also found that in tensile experiments of a bent specimen (accidentally or intentionally) negative charge appears on the concave side and positive charge appears on the convex side, and the negative charge is larger, in absolute value, than the positive charge, in the early stages of deformation. A model is proposed to explain these results.
Ultrasonic Internal Conical Refraction in Rocksalt and Calcite
Authors: Papadakis Emmanuel P.
Published: April 2005

Evidence for the existence of ultrasonic internal conical refraction in rocksalt and calcite single crystals was obtained by observing the behavior of shear waves along one of the axes of threefold symmetry in each crystal. A method of selective absorption was used in conjunction with pulse-echo ultrasonic attenuation measurements. Absorbing material was pasted at various spots on the bottom of the specimen opposite the transducer to map the energy density in the wave. Positions of maximum flux coincided with predictions when the shear wave was not perturbed by misorientation-induced ultrasonic double refraction.
Internal Friction in the Vanadium-Hydrogen System
Authors: Butera Richard A. , Kofstad Per
Published: April 2005

Internal friction in a series of V-H alloys has been measured over the temperature range −190° to +210°C. The hydrogen compositions varied from 1.2 to 14.5 at.% and two frequencies, 75 and 270 cps, were used. For each frequency a single peak was observed having an amplitude which increased essentially linearly with hydrogen concentration. This is suggestive of stress-induced ordering of the hydrogen atoms in the vanadium-hydride lattice. Comparison of the activation energy and temperature of this peak with that reported by the authors for the tantalum-hydrogen system indicates that the hydrogen atoms are located in the tetrahedral interstices.
Kinetics of Melting and Crystallization of Phosphorus Pentoxide
Authors: Cormia R. L. , Mackenzie J. D. , Turnbull D.
Published: April 2005

The melting and crystallization of tetragonal phosphorus pentoxide has been investigated by the use of a microscopic technique. Superheating of about 50° above the melting temperature was possible. Melting was heterogeneous and began only at free surfaces or grain boundaries but never within a crystal. At a supercool or superheat of 10°, the respective rates were approximately 5 and 10 A/sec. The dependency of melting and crystallization on temperature, time, crystal direction, morphology, and preparation history was studied. Under ideal conditions, the observed rates were in almost quantitative agreement with those calculated from a simple model based primarily on viscosity considerations.
Viscous Flow and Melt Allotropy of Phosphorus Pentoxide
Authors: Cormia R. L. , Mackenzie J. D. , Turnbull D.
Published: April 2005

The viscosity of liquid phosphorus pentoxide at temperatures both above and below the melting point of the tetragonal crystal has been determined by the falling sphere method. At the melting temperature of 580°, the viscosity is 5.15×106 P and the activation energy for viscous flow is 41.5 kcal/mole. These values suggest that similar to liquid B2O3 or SiO2, the melt of tetragonal P2O5 can be classified as a network liquid. From qualitative observations on melting behavior and a consideration of the refractive indices of the crystalline and glassy phases, hexagonal P2O5, on the other hand, gives a molecular liquid on fusion. The ``hexagonal'' liquid, however, is unstable and undergoes rapid polymerization to give the network liquid.
Hardening of Potassium Chloride by Color Centers
Authors: Nadeau John S.
Published: April 2005

The flow stress of KCl crystals containing color centers was studied in a systematic way to determine which color centers produced significant hardening. The color centers were introduced both by additive coloring and by gamma irradiation. Annealing and optical bleaching techniques were used to alter the relative concentrations of defects.

For a given concentration of electron excess centers (F, M, R, N, etc.), the irradiated crystals were about ten times harder than the additively colored ones. Possible models for the halogen defect responsible for this high hardness were considered and it was concluded that it must be an interstitial ion or atom.

Annealing of additively colored crystals indicated that the ``colloid band was actually two overlapping bands centered at about 735 and 760 mμ. Prior to formation of these bands the crystals became about 40% harder than in the as-colored state indicating the presence of a coherent cluster of elementary defects. The flow stress decreased sharply upon appearance of the colloid bands. A similarly located though broader band was formed after prolonged optical bleaching.
Tear Marks on Cleaved Germanium Surfaces
Authors: Haneman D. , Pugh E. N.
Published: April 2005

A microscopic study has been made of the origin and nature of tear marks in germanium. The observations suggest that the tear marks can originate in two different ways. The majority are thought to occur when the crack attains a critical velocity, the lattice disturbances set up ahead of the advancing crack deflecting the crack onto different levels. The second type is formed when the curvature of the fracture surface changes abruptly. Taper sections show that the steps at both types of tear mark are identical in profile; they are generally perpendicular to the cleavage surface but frequently contain curved segments.
Applicability of the Band Model to Metal-Free Phthalocyanine Single Crystals
Authors: Heilmeier George H. , Warfield George , Harrison Sol E.
Published: April 2005

The applicability of the band model to explain conduction in metal-free phthalocyanine is suggested by the equality of the thermal acrivation energy for electrical conduction, the energy for first optical absorption, and the energy for the initiation of photoconductivity. Further support for the band model is furnished by the similarities between phthalocyanine and anthracene since evidence has been advanced for the band-model approach in anthracene. The existence of tightly bound excitons is shown to be an unimportant consideration in conduction processes where the band model is applicable and the same equality among the aforementioned experimental data is obtained. Still further evidence for the band approach comes from Hall measurements. If the Hall data are interrpeted assuming the band approach is feasible, the calculated free-carrier concentration agrees quite well with that found from bulk current measurements.
Spectral Output and Spiking Behavior of Solid-State Lasers
Authors: Tang C. L. , Statz H. , deMars G.
Published: April 2005

Experiments show that conventional solid-state lasers can go into oscillation simultaneously in many modes. This is somewhat surprising since it appears impossible to ``eat holes'' in temperature-broadened lines and thus only one or, at most, a few modes should be able to oscillate. However, the spatial variation in the field intensity of the various modes produces nonuniform distributions in the inverted population and one can show that there is little tendency for these distributions to smooth out due to spatial cross relaxation. Such nonuniform distributions could lead to simultaneous oscillation in many modes. Formulas which relate the number of unstable modes to the pump power and various other maser parameters are obtained. The results show that it is exceedingly difficult to obtain single mode operation in conventional masers at high pumping levels. Ways to avoid a nonuniform distribution density and methods to achieve high-power single-mode operation in practice are discussed. It is also possible to show the effect of slow spatial cross relaxation on the spiking behavior.
Analysis of Thin-Film Germanium Epitaxially Deposited onto Calcium Fluoride
Authors: Pundsack Arnold L.
Published: April 2005

An experimental investigation of the formation conditions of thin-film Ge epitaxially deposited onto (111) surfaces of CaF2 and the resultant physical and electrical character is presented. The amorphous to crystalline transition region was found to be between 320° and 400°C, and the best single-crystal orientation was found between 550° and 575°C. Average values of the mobility, conductivity, and the hole concentrations are also reported with an explanation of the problems encountered in their determination.
New Type of Thermoplastic Deformation
Authors: Cressman P. J.
Published: April 2005

When certain thermoplastics are coated on a conducting substrate and uniformly charged and softened by heat, a wrinkling type of deformation occurs. It is found that the deformation will not occur below a critical value of the surface charge density. A mechanism is proposed in which the surface tension of the thermoplastic is reduced by the presence of the surface charge. Experimental results indicate that the surface potential at threshold varies as the one-half power of the film thickness, which is predicted by the mechanism proposed. A one-dimensional model is presented which predicts that a deformation will occur; however, quantitative agreement of the model with experimental data is not obtained.
Compressibility of Solids and Liquids at High Pressures
Authors: Cook Melvin A. , Rogers Leo A.
Published: April 2005

An equation for compressibility (identical in form to the Tait equation) derived previously from the virial theorem and the Fermi—Thomas atomic model is modified on the assumption that one of its parameters (αβ0) is reciprocally related to the internal pressure when the cohesive energy density is assumed to be an essential part of the internal pressure. Pressure—volume data for about fifty homonuclear solids, two alloy systems, twenty ionic compounds, and five secondary bonded liquids are analyzed and the model found to fit with surprising accuracy when due consideration is given to pressure-induced phase or polymorphic changes and thermodynamic ``holes'' (most important near, and above, the melting point) that may contribute appreciably to specific volume. Data from static and shock methods of compression are considered and the differences noted. The model is apparently applicable to the compression of homonuclear solids and liquids, if indeed not all condensed materials in general.
Elastic Stress Field of an Angular Dislocation
Authors: Hokanson J. L.
Published: April 2005

An angular dislocation lies along a continuous curve which is the union of two semiinfinite straight lines. The isotropic elastic stress components are derived for three angular dislocations which are distinguished by having orthogonal Burgers' vectors. The stress field of an angular dislocation with an arbitrary Burgers' vector can be found by superposition of these results.
Physical Properties of Titanium. III. The Specific Heat
Authors: Holland Lawrence Rozier
Published: April 2005

The specific heat of titanium has been measured over a temperature range from 600° to 1345°K. The specific heat at 600°K is 0.72 J/g°K ±2.5%, and increases to 0.93 J/g°K ±6% just below the transition, which takes place at 1155°K. Above this point the specific heat drops to 0.75 J/g°K ±4%, where it appears to remain fairly constant. The increase of the specific heat to 1.7 times the Dulong and Petit value is interpreted as an effect of anharmonic terms in the potential of the atomic oscillators, as proposed by Born and Brody.

The samples were heated by alternating current, varying in frequency from 8.63 to 14.35 cps, causing a temperature fluctuation at twice the heating current frequency, and a resultant resistance fluctuation. The resistance fluctuation was observed electrically, and from it, through the measured temperature coefficient of resistance, the temperature fluctuations and specific heat were calculated.
Hardening of KCl by Electron and Gamma Irradiation
Authors: Sibley W. A. , Sonder E.
Published: April 2005

Measurements of the flow stress and F-band coloration have been made at room temperature on a number of different samples of KCl as a function of gamma and electron irradiation. The rate of increase of flow stress with irradiation is found to be greater (or smaller) in those samples and for those irradiation conditions for which the coloring rate is greater (or smaller). Moreover, the flow stress increase in any set of samples is proportional to the square root of the F-band absorption. The implication is that hardening is caused either by F centers or other defects whose production is related to the production of F centers. Since bleaching of F centers does not produce any softening, and since the magnitude of the hardening is of the order of magnitude to be expected for interstitial type defects, the conclusion is drawn that the increase of flow stress due to irradiation of KCl is caused by interstitial Cl atoms or interstitial clusters.
Determination of Néel Temperatures in fcc Iron
Authors: Gonser U. , Meechan C. J. , Muir A. H. , Wiedersich H.
Published: April 2005

The Néel temperatures of 304 stainless steel and γ-Fe precipitates stabilized in the copper lattice have been determined by making use of the Mössbauer effect. The Néel temperature for the stainless steel is 38°±2°K and for two different sizes of γ-Fe precipitates, the Néel temperatures are 55°±3°K and 67°±2°K. The measured Néel temperatures are compared with previous determinations by other methods and the variation of the Néel temperature of precipitates in the Cu—Fe system is discussed. Estimates are made of the magnetic field at the iron nucleus for each case.
Electron Scattering at Small Angles by Carbon
Authors: Sarkar N. H.
Published: April 2005

The differential and total elastic and inelastic scattering cross sections of the carbon atom have been estimated theoretically with a more realistic charge distribution for the electrons in the K and L shells. The agreement of the several experimental results with the present theoretical calculation is much better than with the existing theories of Lenz and Leisegang. For scattering by polystyrene latex particles, addition of the contribution of the hydrogen atoms in these particles results in an improvement of the agreement between theory and experiment.
Behavior of Gold Blocking Contacts to CdS at High Impressed Fields
Authors: Muller Richard S.
Published: April 2005

Experiments performed on gold-to-CdS rectifying contacts under breakdown conditions indicate that the barrier formed at the metal-insulator interface is analogous to the barrier at an emitting surface in a vacuum tube. Breakdown of the junction appears to take place by Schottky-type high-field emission over the potential step at the barrier. Measured values for the barrier potential step are between 0.8 and 1.0 eV.
Energy Band Parameters of Germanium Indicated by Tunnel Diode Reverse Characteristics
Authors: Carr William N.
Published: April 2005

A precise method for analyzing the current—voltage characteristic of the reverse biased junction has permitted a direct observation of the voltage levels corresponding to the onset of tunneling into several energy subbands of germanium. The experimental technique involves fitting the experimental data to an equation of the form J = αV exp (−βV) derived from the calculations of Price, Radcliffe, and Kane. The onset of the tunneling interaction with each subband is noted as structure in the plots covering the reverse bias range. The values for EΓ2 − RL1 and EΔ1 − EL1, corresponding to the energy separations of the band minima, are found to be 0.152±0.005 and 0.208±0.008 eV, respectively, for slightly degenerate n-type material at 4.2°K.

The conduction energy bands are each found to move closer to the valence band level for increasing degeneracy by comparing the present data with the optical data of Pankove and Aigrain for the direct band gap. Energy spacing of the various conduction band minima is found to remain constant with increased electron concentration. Evidence for a ``tailing'' of the principal conduction band edge into low mass states is discussed for heavily doped n-type material.
Line Strengths for Noble-Gas Maser Transitions; Calculations of Gain/Inversion at Various Wavelengths
Authors: Faust W. L. , McFarlane R. A.
Published: April 2005

Relative line strengths for s-p, p-d, and d-f transitions of Ne, A, Kr, and Xe are derived by the method of Koster and Statz, under the assumption of the j-l coupling scheme of Racah. When the relative strengths are given a common denominator, a set of rules for strong lines becomes apparent, similar to rules which have been noted for L-S coupling. For comparison with experiment, we consider several sets of Ne lines, each set having one specific initial, and one final configuration. For the higher l values (p-d and d-f) the lines found to give oscillation are almost exclusively the lines with large relative strengths. The absolute line strengths S are then calculated in the Coulomb approximation of Bates and Damgaard; we consider only transitions between two excited states. There is the following simple relation between (gain constant/volume density of inversion) and S:α/(N2/g2−N1/ g1)=1.76×10−13 (mass number)1/2S. The units of α are cm−1. N1 and N2 are in cm−3. S is in atomic units, a02e2. The linewidth is taken to be determined by Doppler broadening at 400°K. For several lines upon which measurements of α have been made, we give the corresponding values of (N2/g2−N1/g1). This inversion quantity is a population difference between elementary quantum states.
Focused Microwave Technique for Measurement of the Ionization Rate and Collision Frequency
Authors: Scharfman W. , Morita T.
Published: April 2005

A technique for the measurement of ionization rate and collision frequency in gases uses high-powered focused microwaves. By using short pulses and focusing the energy into a small spot within a large vacuum chamber, diffusion losses are made negligible. Under these conditions the breakdown equation can be simply solved for the ionization rate in terms of easily measured parameters—the pressure, pulse width, and electric field. Experimental results with this technique are compared with published results. The agreement between the two is sufficiently good to confirm the usefulness of this technique.

Due to the focusing of energy into a spot remote from walls, the walls do not enter into the ionization process. In this way a possible source of error in the measurement of ionization rate is avoided.

Since the technique arranges conditions so that diffusion losses are negligible, it is not necessary to know the diffusion coefficient in order to determine the ionization rate.
Elimination of the Edge Effect in Superconducting Indium and Tin Films
Authors: Ames I. , Seki H.
Published: April 2005

Superconducting thin film strips of indium and tin from 3000 to 10 000 Å thick, having sharp, magnetically induced resistive transitions between their superconducting and normal states, have been produced. Usually, the width of such transitions may be as much as 50% to 100% of the critical field because of the relatively high fields required to switch the thinner, tapered edges of the films. This tendency has been counteracted by preferentially depressing the critical temperature near the film edges through the use of an overlapping film of copper or gold, up to several hundred angstroms thick. Transition sharpening equivalent to that observed when the edges of the superconducting films are mechanically removed has thus been achieved. Behavior predicted by analyses of a simplified model has been found to be consistent with experimental observations.
Effective Thermal Conductance from a Thin Film into Liquid Helium
Authors: Seki H. , Ames I.
Published: April 2005

The steady-state thermal dissipation from heat-generating thin-film strips, immersed in liquid helium, has been examined by measuring the thermal hysteresis of the magnetically induced resistive transition of superconducting thin films of tin, deposited onto glass and aluminum substrates. The dissipated heat was found to depend linearly on the temperature difference between the film strip and the helium bath. It was thus possible to characterize the heat transfer by an effective coefficient of heat transfer that was approximately ten times as great for films on aluminum substrates as for films on glass substrates. For a 0.12-×2.3- mm2 film strip, its value was approximately 8×10−3 W/°K for the aluminum substrate, approximately 9×10−4 W/°K for the glass substrate. The coefficient was also dependent on the nature of other thin films deposited beneath or above the film strip. Analysis of the data indicated that the thermal conductance between the film strip and the helium bath was about 0.1 W/cm2 °K, and the thermal conductance between the film strip and the aluminum about 1.7 W/cm2 °K.
Determination of Unloading Behavior of Uniaxially Strained 6061-T6 Aluminum from Residual Strain Measurements
Authors: Hartman W. F.
Published: April 2005

The zero stress point on the one-dimensional strain, dynamic stress—strain unloading curve of shock loaded 6061-T6 aluminum has been determined by measuring the residual strain in the material after shock loading. As any postulated release path from a given stress should pass through this point, it is possible to deduce certain aspects of the manner in which the material unloads from a shocked state. A comparison of the results of these experiments with the strains predicted on the basis of the simplified elastic—plastic theory establishes the inability of the simplified theory to accurately predict the release path of 6061-T6 aluminum from a stressed state. Two major additions to the simple theory are required to explain the permanent strain data. These are a consideration of the Bauschinger effect, and the incorporation of an increased flow stress greater than that predicted from quasistatic data; the latter effect especially is quite possibly strain-rate dependent. Another somewhat surprising result of the permanent strain experiment is the demonstration of the large variations in permanent strain resulting from seemingly minor changes in material composition.
Quasistatic Properties of RIS Films of Oxidized Permalloy
Authors: Wilts C. H.
Published: April 2005

Some properties of oxidized Permalloy films with well defined rotatable initial susceptibility (RIS) have been measured throughout the composition range 70% to 90% nickel and over the thickness range 500 to 7000 Å. These properties include initial suceptibility, coercive force, saturation magnetization, rotational hysteresis and the rotational hysteresis integral. Interesting correlations were found between these properties and the thickness and composition. In particular, the rotational hysteresis integral has the characteristic value 1.5 for type 1 RIS and a different value 3.5 for type 2 RIS, independent of thickness or composition in the range studied. It was concluded that there is no significant correlation between the RIS property and macroscopic magnetostriction of the Permalloy used.
Piezoelectric Sensitivity and Reproducibility of Z-Cut Tourmaline to 7 kbar
Authors: Hearst J. R. , Geesaman L. B. , Power D. V.
Published: April 2005

The piezoelectric sensitivities of 20 z-cut tourmaline crystals have been compared up to 7 kbar. Deviations from a mean of up to 15% have been found. The mean was 1.69×10−8 C/cm2·kbar for uniaxial and 2.39×10−8 C/cm2·kbar for triaxial tests to 3.5 kbar. A quadratic was fitted to sensitivities obtained from shocking the crystals to 7 kbar. Another set of crystals of different size was compared to the first. Fair agreement was found at high pressures, poor agreement at low. Hysteresis was not observed, nor was directional dependence.
Experimental Determination of the Shape of Metal—Insulator—Metal Potential Barriers
Authors: Geppert D. V.
Published: April 2005

The method presented for determining metal—insulator—metal potential barrier shapes from experimental data should be useful in research on metal—insulator—metal sandwich film structures, particularly as related to the influence of deposition parameters on the electronic properties of the structures.
Optical Second-Harmonic Generation in ZnS—CdS and CdS—CdSe Alloys
Authors: Soref R. A. , Moos H. W.
Published: April 2005

Optical second-harmonic generation has been measured as a function of alloy composition in wurtzite ZnS—CdS and CdS—CdSe monocrystals. The relative values of the nonlinear susceptibilities were determined; χ33 increased by nearly one order of magnitude as the band gap was decreased from 1.52(2h/ω) to 0.73 (2h/ω). (Because of this strong increase in χ33, appreciable second-harmonic signals were detected in the crystals of the series which were highly absorbing at the harmonic frequency.) This agreed with the predictions of a quantum-mechanical analysis. Studies of other II-VI and III-V compounds indicated a strong dependence of the second-order susceptibilities upon the band gap.
Elastic Moduli of Silicon vs Hydrostatic Pressure at 25.0°C and − 195.8°C
Authors: McSkimin H. J. , Andreatch P.
Published: April 2005

Ultrasonic wave velocities and elastic moduli for high purity silicon (resistivity ∼400 Ω-cm) have been measured as a function of hydrostatic pressure and temperature in the ranges 0–30 000 psi (0–2100 kg/cm2) and − 195.8° to 25°C. Variations of moduli with pressure are found to be nearly independent of temperature in the range listed. For 25°C(Δc11/Δp)=4.33, (Δc12/Δp)=4.19, (Δc44/Δp)=0.80, (ΔK/Δp)=4.24. For − 195.8°C(Δc11/Δp)=4.29, (Δc12/Δp)=4.20, (Δc44/Δp)=0.75, (ΔK/Δp)=4.23.
Decay of Elastic Waves in Solids with Dislocations
Authors: Harris Paul , Greene Richard F.
Published: April 2005

A nonlinear, time-dependent, integral stress—strain relationship is formulated. Response functions for various powers of the retarded stress have transforms which satisfy dispersion relations. Characteristics and characteristic equations for one-dimensional elastic—plastic wave propagation are developed.

We assume that the mechanism for the decay of elastic waves is the same as the mechanism of ultrasonic internal friction. This permits us to evaluate the linear response function by comparison with frequency-dependent internal friction theory and experiment. The functional form of the nonlinear response function is found.
Electrical Properties of Thin Polymer Films. Part II. Thickness 50–150 Å
Authors: Christy R. W.
Published: April 2005

The current I through silicone polymer films formed by electron-beam bombardment in the thickness range 50–150 Å has been measured as a function of voltage V and temperature between 77° and 300°K. The electrodes were evaporated silver films. The behavior is Ohmic at low voltage, and log I varies as V½ at higher voltages up to about 1 V. The voltage dependence is insensitive to temperature, although the total current depends rather strongly on temperature. The current decreases with time, as a result of the diffusion of oxygen into the dielectric film. Changes in the current are closely correlated with capacity changes. Simple tunneling theory, including the effects of image force and dielectric constant, fails to account for all the data.
Preparation and Properties of Thin-Film Hard Superconductors
Authors: Edgecumbe J. , Rosner L. G. , Anderson D. E.
Published: April 2005

Films of thickness the order of 1000 Å of Nb-Zr, Nb-Ti, Ti-V, V-Si, Nb-Sn, and Nb have been prepared by dc sputtering and by electron bombardment evaporation. Measurement of the critical current Jc as a function of external magnetic field H was carried out at 4.2°K by using pulsed magnetic fields and pulsed currents. The films have Jc vs H characteristics and transition temperatures very similar to those reported for bulk hard superconductors. An exception was the sputter-deposited Nb, Tc≈9°K, which was superconducting at 70 kOe and 103 A/cm2. More structure was observed in the Jc vs H characteristic for longitudinal configuration than previously reported.
Structural and Optical Characteristics of Thin GaAs Films
Authors: Davey John E. , Pankey Titus
Published: April 2005

Structural, electrical, and optical measurements have been carried out on over 85 GaAs films deposited under high vacuum in a thickness range between a few hundred to 70 000 Å, and for substrate temperatures between 175° and 450°C. The films were textured when deposited above 220°C, exhibiting [110] textures below 280°C and [111] textures above 320°C. The films were always p type and the lowest resistivity measured was 20 Ω·cm. Films deposited below 280°C exhibit a fundamental absorption edge shift to lower energies; this shift is correlated with x-ray line shift and annealing-out measurements of conductivity. The absorption edge shift is attributed to a high concentration of vacancies trapped in the film during growth at low temperatures. An acceptor level 0.18 eV above the valence band is associated with these vacancies. The films exhibiting the anomalous shift can yield bulk optical properties by prolonged heating at 380°C. Films deposited above 320°C always exhibit properties characteristic of high-resistivity bulk GaAs.
X-Ray Diffractometry of Low-Temperature Phase Transformations in Strontium Titanate
Authors: Lytle Farrel W.
Published: April 2005

The lattice parameters of single-crystal SrTiO3 were determined by x-ray diffraction as a function of temperature from 4.2° to 300°K. In addition to the normal cubic structure three significant regions were found. From 65° to 100°K a tetragonal modification exists (c/a=1.00056), from 35° to 55°K line splitting consistent with orthorhombic symmetry was observed, and at 10°K an anomalous maximum in the lattice parameter vs temperature curve was found which suggested a third structure transformation. In the tetragonal region (at 78°K) various domain configurations were photographed with a polarizing microscope.