bluuebunny/crossref_metadata_2025 huggingface dataset:
Anomalous Mobility Effects in Some Semiconductors and Insulators
Authors: Weisberg Leonard R.
Published: April 2005

The Hall mobility in semiconductors and insulators can be greatly affected by inhomogeneous impurity distributions. This is due to the formation of large space-charge regions surrounding local inhomogeneities. The scattering cross section of Coulombic centers can be increased by over an order of magnitude when inhomogeneously distributed. The mobility resulting from scattering from inhomogeneities varies roughly as T−½ and decreases with decreasing carrier concentration. Assuming that inhomogeneities can occur frequently, various anomalous Hall mobility effects can be explained, such as mobility ``killers'' in GaAs, InAs, and InP; giant scattering cross sections in GaAs, InP, CdS, and CdSe; abnormally low mobilities in compensated InAs; and low mobilities in ZnO containing precipitates.
Significance of Crystallographic Polarity in the Fabrication of Junctions in InSb
Authors: Minamoto Miriam T.
Published: April 2005

The effect of {111} polarity in the fabrication of alloyed p-n junctions in InSb was investigated. The fabrication procedure also considers other polarity dependent effects found in III–V compounds. the results of this investigation suggest use of the {1̄1̄1̄} surface over the {111} for obtaining planar, lower reverse current, higher and sharper breakdown junctions. The implication of this study, using the exemplary III–V compound InSb, is that in the use of III–V compounds for the fabrication of p-n junction devices, one must regard a concept, polarity, heretofore not embraced in the manufacture of devices made of Ge and Si.
Sputtering Yields for Low Energy He+-, Kr+-, and Xe+-Ion Bombardment
Authors: Rosenberg D. , Wehner G. K.
Published: April 2005

Sputtering yields of various metals have been determined for He+-, Kr+-, and Xe+-ion bombardment in the energy range 100 to 600 ev. Yields at 400 ev show a periodic dependence on atomic number similar to that of the reciprocals of the heats of sublimation.
Magnetic Films: Nucleation, Wall Motion, and Domain Morphology
Authors: Schuler Frederic
Published: April 2005

Nucleation fields for the reversal of magnetization in thin iron-nickel films were experimentally measured. The reversal was observed by the Kerr magneto-optical effect. Different regions or types of imperfections were observed at which lower nucleation fields are required than for the more perfect regions. Small regions of study in the ``interior'' of the film were localized by using an inhomogeneous field a millimeter or less in extension. Nuclei formed reproducibly about a center, with a statistical probability of formation which depended on the pulse length and field strength. A mode value of nucleation can be associated with a given center. The average of the mode values for different centers increased somewhat with film thickness, and showed a marked dependence upon composition, with a minimum value for films containing 80–85% nickel.

Repeated pulsing with fields smaller than those required for nucleation increased the size of nuclei, while maintaining the same lenticular shape, to limiting dimensions which increased with film thickness. At higher fields, wall motion was observed in detail for two types of motion: (1) the tip of the domain was displaced along the easy axis with an axial or ``endwise'' extension; (2) the ``180° wall'' was displaced along the hard axis with a normal or ``sidewise'' extension. Endwise extension takes place at lower fields than sidewise extension. Evidence was obtained to indicate that an energy barrier exists for sidewise motion, e.g., repeated 1.5-μsec pulses caused no motion, whereas a single 20-μsec pulse did. With very narrow drive wires or with thick films, additional nucleation took place instead of ``sidewise'' motion of the wall; otherwise, domains could be enlarged at will. Some films were produced which required larger fields to ``erase'' or contract the domain lengthwise than for tip extension.

The instabilities and general morphology of the domains as they depend on composition, film thickness, distance of extension of the inhomogeneous field along the easy axis, and the magnitude of the drive field were studied. Certain configurations led to a morphology of many small nuclei, which eventually were dense enough to join into a single domain; other configurations showed domain growth by wall motion and a large domain formed from very few nuclei. Very small nuclei were generally unstable, disappearing in a short time after formation. The smallest stable nucleus observed was about 0.25 mm×0.04 mm. The transition in behavior between 1.0- and 0.5-μsec pulses stresses the importance of multiple-nucleation processes in the nonuniform rotation region. The finescale observations on fields for nucleation and wall motion make possible comparisons with the processes taking place when the complete specimen is switched in a B-H loop tester.
Electrode Design for Axially Symmetric Electron Guns
Authors: Harker Kenneth J.
Published: April 2005

In a previous article, a method for obtaining electrode shapes for axially symmetric electron guns was presented. In essence, this method depended upon reformulating the problem according to a method of Garabedian so that the solution can be obtained by finite-difference methods. This is accomplished by an analytic continuation which transforms the Laplace equation into a form which is hyperbolic. The purpose of this paper is to present improvements in the original formulation. By introducing time as the independent variable, the derivatives in the space-charge flow equations are made well-behaved at the cathode. A different set of dependent variables is introduced so that the matrix of the coefficients associated with the system of partial differential equations possesses simple elementary divisors. Finally, the difference equations have been modified to a form more suitable for numerical computation.
Čerenkov Radiation from an Electron Traveling in a Circle through a Dielectric Medium
Authors: Erteza Ahmed , Newman John J.
Published: April 2005

The theoretical problem of determining the Čerenkov radiation from an electron traveling in a circle through a medium has been advanced and the fields and resultant radiation from such a geometry have been determined. A solution is achieved by a transformation of the fields as determined by Frank and Tamm in their original article on Čerenkov radiation. This transformation results in a solution as a summation of eigenfrequencies each separated by the frequency of the periodic motion of the electron. The radiation expression derived by this transformation method approaches the Frank and Tamm radiation expression in the limit.
Radiation Effects in CaF2:Sm
Authors: O'Connor J. R. , Bostick H. A.
Published: April 2005

The absorption spectra of Sm3+ and Sm2+ in CaF2 have been measured from 200–800 mμ at room and liquid-nitrogen temperatures. A strong divalent absorption band at 620 mμ has an effective oscillator strength of 1.1×10−2. This band has been used to study the reduction of CaF2:Sm3+ by ionizing radiation. For some samples, the reduction is as large as 50%. The kinetics of the reduction is obscured due to the presence of oxygen and other crystal defects. The data do indicate that the charge compensator for Sm3+ in CaF2 is an interstitial F− ion.
Dependence of the Thermoelectric Figure of Merit on Energy Bandwidth
Authors: Miller R. C. , Heikes R. R. , Fein A. E.
Published: April 2005

The thermoelectric figure of merit Tz of a semiconductor is calculated as a function of the width of the conduction band. It is found that Tz approaches zero as the bandwidth goes to zero. The existence of an optimum bandwidth is established; however, the magnitude cannot be ascertained on the basis of the simple model used here.
Point Defect Trapping in Crystal Growth
Authors: Webb W. W.
Published: April 2005

The possibility of trapping significant quantities of point defects during growth of a crystal is considered. Calculations are based on the well-established theory of growth from the vapor on vicinal surfaces and the results are applied approximately to more complex cases. Concentrations of point defects, either above or below equilibrium, can be trapped under some conditions. In most cases the effect is insignificant. The crucial characteristic of a growth condition is defined by the dimensionless parameter Dv/Rd where Dv is the bulk diffusion coefficient for point defects (vacancies), R is the growth rate, and d is the ``effective thickness'' of the surface. The value of d is about 1 atom layer in most cases, but may be greater at solid-melt interfaces. Large supersaturations of point defects may be trapped if Dv/Rd is small. For very large values of Dv/Rd, subsaturation concentrations of vacancies may be trapped. Growth trapping accounts for the loss of dislocations from metal whisker crystals during growth and may support a simple explanation of some substructure formation during solidification of pure single crystals.
Plasma Waveguides as Low Loss Structures
Authors: Lichtenberg A. J. , Woodyard J. R.
Published: April 2005

The dispersion relation for propagation of an electromagnetic wave between two semi-infinite slabs of plasma is found under the assumption of infinite magnetic field along the slabs. Provided the plasma frequency is above the applied frequency, a fast wave solution exists, with a sinusoidal field distribution in the free-space region between the plasma slabs, and exponential decay into the slabs. A complex plasma frequency is introduced to account for collision losses in the plasma, and substituting this complex plasma frequency into the dispersion relationship, the attenuation constant of the wave is found. The imaginary part of the plasma frequency is computed from collision theory and found to give damping considerably smaller than that obtained with metal guides. An application to high-field linear accelerators is treated in detail.
Tunnel Emission into Vacuum
Authors: Cohen Julius
Published: April 2005

Tunnel emission into vacuum is obtained from thin-film sandwiches of (a) aluminum-alumina-aluminum and (b) aluminum-alumina-platinum. The alumina layer is made by oxidizing an evaporated film of aluminum in air. Cesium processing, to lower the work function, results in an increase of emission of five orders of magnitude.
Sputtering of Gold by Low Energy Inert Gas Ions
Authors: Scott H. G.
Published: April 2005

The sputtering yield of gold bombarded by low energy (20–100 ev) helium, neon, and argon ions has been measured by the increase in electrical resistance of a thin gold film. It has been shown that for neon and argon the yield decreases rapidly with decreasing ion energy from 100 to 40 ev; below 40 ev the decrease is less rapid and no definite threshold has been found. With 40-ev neon ions the yield is proportional to the ion current density, but with argon ions of this energy the yield is independent of the current: For currents greater than 100 μa/cm2 neon is more efficient than argon in sputtering gold. To explain the variation of yield with ion current for low energy neon ions it is suggested that the sputtering may take place by a two-stage process: the first stage being the creation of defects in the gold by the ions, and the second stage, ejection of gold atoms from the neighborhood of these defects.
A Technique for Pulling Single Crystals of Volatile Materials
Authors: Metz E. P. A. , Miller R. C. , Mazelsky R.
Published: April 2005

A technique has been developed to pull single crystals of volatile materials using standard pulling apparatus. This has been accomplished by covering the surface of the material to be pulled with a substance that is liquid at the pulling temperature. Crystals of PbTe and PbSe were pulled using molten B2O3 as the surface liquid.
Silicon Monoxide Undercoating for Improvement of Magnetic Film Memory Characteristics
Authors: Bertelsen B. I.
Published: April 2005

The results of two experiments are presented to illustrate the leveling effect of thick layers of SiO on rough substrate surfaces. This effect permits the use of metallic underlayers as substrates for films of NiFe.
Tube Target and Inherent Filtration as Factors in the Fluorescence Excitation of X Rays
Authors: Spielberg N.
Published: April 2005

Experimental studies have been made of the effect of x-ray tube target and inherent filtration on the fluorescence excitation of x rays in pure-element specimens and in multiple-element specimens, in particular for elements between potassium (19) and aluminum (13). Data are presented on the effect of W, Cu, Cr, Mo, and Ag targets with total filtration of 1050, 300, and 50 μ of beryllium on the excitation of K, Si, and Al Kα radiation. Data are also shown on the effect of tube voltage and of specimen surface roughness on fluorescence excitation. When filtration is light enough to permit full utilization of the Ag or Mo L series or of the W M series, an order of magnitude increase in fluorescence excitation intensity is obtained.
Effect of Impurities on the Flow Stress of LiF Crystals
Authors: Johnston W. G.
Published: April 2005

The mechanical properties of LiF single crystals with relatively low impurity content are compared with those containing ∼75 ppm of magnesium. These crystals represent the extremes of material that have been obtained from the Harshaw Chemical Company during the past six years.

The recently produced, ``pure'' crystals are very soft (80–100 g/mm2 critical resolved shear stress), and insensitive to heat treatments; and their flow stress varies slowly with test temperature. The impure crystals are much harder as received (∼1500 g/mm2) and respond to heat treatment in a manner that suggests precipitation hardening. The temperature dependence of the flow stress is much different in slowly cooled and rapidly cooled impure crystals. Whereas the slowly cooled crystals are much harder at room temperature, air-cooled crystals in which the magnesium is present in vacancy-impurity pairs are harder at low temperatures.

Two questions that must be answered are: (1) How does such a small amount of impurity present in aggregates produce a large hardening at room temperature? and (2), how do isolated vacancy-impurity pairs produce the large, temperature-sensitive hardening at low temperatures? The effects of impurities must be understood in terms of how they resist the motion of fresh dislocations.

One possibility that should be further explored is that impurities in these crystals affect the resistance to dislocation motion by altering the steady-state number of jogs on the screw dislocations. The existence of many jogs and the fact that they contribute to the flow stress have been previously established.
Nonlinear Viscoelastic Behavior of Glass at Its Transformation Range
Authors: Wang Franklin F. Y.
Published: April 2005

A mechanical model is employed to simulate the deformation behavior of glass rods subjected to tensile loads which varied linearly with time. Assumptions are made about the nonlinearity of viscosity and modulus, and about the distribution function of viscosity coefficients as a function of retardation time. A modification of the model is introduced to apply the fictive temperature concept to viscosity data and is also applied to the case of stress-release under constant strain.
Thermal Expansion of KCl at Elevated Temperatures
Authors: Enck Frank D. , Engle Daniel G. , Marks Kenneth I.
Published: April 2005

The linear thermal expansion of KCl has been measured from room temperature (26°C) to near the melting point (776°C), using the Fizeau interferometer technique. The results are compared with previous values quoted in the literature. It is believed, for reasons discussed in the paper, that the results obtained in this determination are the best values of the coefficient of linear thermal expansion of KCl at elevated temperatures that are available to date.
Thermionic Emission from Molybdenum in Vapors of Cesium and Cesium Fluoride
Authors: Aamodt R. L. , Brown L. J. , Nichols B. D.
Published: April 2005

``S curves,'' similar to those given by Langmuir for electron emission from tungsten in cesium vapor, are presented for electron emission from molybdenum in cesium vapor. It is shown that the addition of cesium fluoride greatly enhances the electron emission. The minimum effective work function of the Cs-CsF-Mo surface is 1.38±0.05 ev, while that of the Cs-Mo surface is 1.68±0.05 ev. The new cathode may be useful in thermionic converters.
Parametric Effects in a Two-Level Electric Dipole System
Authors: Fontana J. R. , Pantell R. H. , Smith R. G.
Published: April 2005

In a two-level system with induced electrical dipole properties, the relationship between an externally applied electric field and the expectation value of the dipole moment is expressed by a differential equation, in which one coefficient is proportional to the instantaneous system energy. The nonlinear properties arising from this relationship allow parametric amplification of signals by pumping at another frequency, in the presence of a material containing active systems of this type. No population inversion is necessary.

For optimum operation, both the pump and the signal should be within a few per cent of the natural frequency of the system. The electromagnetic Q required for parametric oscillations in a device of this sort is inversely proportional to the on-frequency absorption coefficient for the material. A numerical example shows that, at 1 mm wavelength, parametric oscillations will occur with a Q of 12 000 and a pump field of 10 kv/cm in a gas with an absorption coefficient of 0.1 cm−1.
Theory of Minority Carrier Thermoelectric Cooling
Authors: Melehy M. A.
Published: April 2005

The possibility of backward injection of minority carriers in p-n junctions is shown. It is predicted that in a forward-biased p-n junction where this type of injection occurs, heat energy is pumped out of the junction causing it to cool off. Some conditions which lead to backward injection of minority carriers are described. Theory is presented for a particular p-n junction model in which this new cooling effect takes place. It is shown that a given dc electrical energy may be used to pump nearly an equal amount of heat energy from one of the junctions to the neighboring ones provided that the junction temperatures are sufficiently close to each other.
Isotope Effect in an Electric Field and Jump Frequencies for Diffusion in Ionic Crystals
Authors: Manning John R.
Published: April 2005

The simultaneous diffusion of two isotopes of a given ionic impurity in an electric field is considered, and an improved method of analyzing the experimental data to obtain ΔD/D is discussed. (Here D is the diffusion coefficient of one of the isotopes, and ΔD the difference between those of the two isotopes.) As noted by Chemla, an electric field increases the accuracy with which ΔD/D can be determined. Equations are found giving this increase in accuracy as a function of field and diffusion time. If the ratio w2α/w2β of the jump frequencies of the two isotopes is known, relative values of the vacancy or interstitialcy jump frequencies near an impurity can be calculated from ΔD/D and μ/D, where μ is the drift mobility. As an example, data in the literature for Na22 and Na24 diffusing in KCl are considered. For self-diffusion, w2α/w2β may be calculated from ΔD/D and known values of the correlation factor. When data in the literature are used to estimate w2α/w2β for Na22 and Na24 diffusing in NaCl, a value smaller than that predicted by classical rate theory is found.
Interaction of Sliding Metal Surfaces
Authors: Cocks M.
Published: April 2005

The friction of sliding metal surfaces is often attributed to the formation and shearing of welded junctions between the surfaces. This paper describes a more detailed investigation of the phenomena which occur in the junctions. Experiments were performed with a hemispherically ended copper rider sliding against the surface of a large cylindrical copper drum. Observation of the sliding contact through the microscope shows that most of the time during sliding, the drum and rider are held apart by a wedge of displaced metal from the drum, which becomes trapped between them. Whenever a wedge escapes from between the drum and rider, another wedge forms rapidly to replace it. The wedges are also observed with several other combinations of metals, and with pairs of flat copper surfaces. Sections cut through the wedges and adjacent copper contact members were examined. It is found that the shearing of the metal by which the sliding proceeds occurs in a direction slightly inclined to the drum surface. This causes the formation and growth of the wedges. The shearing is primarily a continuous plastic deformation process somewhat similar to the shearing process by which the chip is generated in the cutting of ductile metals with machine tools. It is possible that the adhesion between the rider and wedge may often be weaker than the junctions usually assumed to be responsible for friction. Wear debris is observed to be produced in a number of different ways.
On the Conductivity of Cadmium Sulfide Following Electron Bombardment
Authors: Schulze R. G. , Kulp B. A.
Published: April 2005

Fine rod and whisker-type crystals of undoped CdS whose dark conductivity was of the order of 10−10 (Ω-cm)−1 were bombarded with 100-keV electrons. Following bombardment dark conductivity of the order of 10−3 (Ω-cm)−1 was observed. Heat treatment to about 200°C reduced the conductivity to near its original value. Because of the high efficiency with which the electron beam raised the conductivity of the crystals, an explanation based on the redistribution of electrons and holes over existing levels rather than the production or removal of defects is required.
Dislocations and Plastic Flow in NaCl Single Crystals. I
Authors: Mendelson S.
Published: April 2005

Dislocation multiplication and motion in NaCl was studied using etch pit and birefringence techniques. The observations show that dislocations in glide bands of NaCl are in the form of large concentric loops with sources staggered in the center of the bands. They propagate and multiply by cross-slip and are braked through intersection jogs. The slip distance parallel to b is estimated to be 2–3 mm and that normal to b 0.5–1 mm, at a stress of 30 g/mm2 in crystals having 5×104 dislocations/cm2. ``Deformation bands'' form normal to the operating system during the latter part of stage I by ``glide polygonization'' of edge dislocations on closely spaced slip planes. These limit dislocation motion to shorter distances in stage II. Stage III appears when significant flow occurs on a secondary system oblique to the primary operating one.
Oxygen Precipitation Effects on the Deformation of Dislocation-Free Silicon
Authors: Patel J. R. , Chaudhuri A. R.
Published: April 2005

The yield phenomenon observed in dislocation-free crystals of silicon is critically dependent on prior heat treatment at 1000°C. Since oxygen is always present in crystals grown from quartz crucibles, heat treatment at 1000°C is believed to result in silicon-oxygen clusters. It is shown that these clusters are effective sites for the generation of dislocations. Since the velocities of dislocations in heat-treated and unheat-treated crystals is not altered, the lowered maximum stress is largely due to the increased numbers of dislocations generated at a relatively early stage of the deformation process.
Electrification of the Dust of NaCl and KCl Whiskers
Authors: Jakubiszyn Stanisław , Nikliborc Jan , Wolniewicz Henryk , Szaynok Anna
Published: April 2005

The dust of NaCl and KCl ordinary monocrystals shows greater charge per particle surface area than the dust of whiskers of these materials. The main reason is a greater cleavage surface of monocrystals than the cleavage surface of whiskers. The electrification of the dust is also influenced by the presence of contaminations in the crystal.
Axial Quasi-Brillouin Streams
Authors: Miller M. H.
Published: April 2005

A nonlaminar model for axially uniform electron streams is postulated and conditions for which the model is consistent with physical requirements are derived. The character of the current density profiles permitted by the model are discussed.
A Note on Logarithmic Rate Laws
Authors: Landsberg P. T.
Published: April 2005

An earlier theory for the rate law ψ(t)=β ln(1+t/τ) for strain, or q(t)=b−1 ln(1+t/τ) for chemisorption, is extended to cover a law for creep in materials which has been of interest recently, and takes the form ψ(t)=(β/ν)[(1+t/τ)ν−1]. The theory is formal in that it utilises only general concepts such as probability of success and attempt frequency.
A Simple Approximation for Classical Scattering at Large Angles
Authors: Leibfreid G. , Oen O. S.
Published: April 2005

The classical scattering for repulsive potentials is treated approximately by a matching method. The matching potential is a cut-off potential which matches the value and the slope of the actual potential at the distance of closest approach. The method is thought to be successfully applicable to interatomic potentials of the screened Coulomb type. Comparison is made with machine results for an exponentially screened Coulomb potential. The differential cross section and the stopping power are compared for various energies. The agreement in the differential cross section is fair except for very low energy transfers. The stopping powers agree over a wide energy range with an error of only a few percent. Further comparison is made with another approximation given by Lehman and Shapiro.
Kinetic Interpretation of Non-Newtonian Flow
Authors: Denny D. A. , Brodkey Robert S.
Published: April 2005

A new theoretical approach to the problem of describing the nonlinear behavior of non-Newtonian materials is presented. The theory is based upon the assumption that the nonlinear characteristics can be associated with some structural change of the material, and that reaction kinetics can be applied to this breakdown. The theory allows treatment of time-dependent (thixotropic) materials, and in a limiting form (equilibrium) can be applied to time-independent materials. The theory has been applied to a variety of materials, including polymer latex solutions, polyethylene polymer melts, and a heavy thixotropic mineral oil. The results are gratifying.
Determination of Plasma Properties by Free-Space Microwave Techniques
Authors: Buser R. , Buser W.
Published: April 2005

Time-resolved free-space microwave measurements are used to study the loss mechanisms in the afterglow of an intense He discharge between 100 and 1000 μ. The method of evaluation is developed in detail and the results of the measurements and their accuracy are given. Some of the problems and limitations of the microwave method are discussed; in particular, plots of the field pattern between the horns are presented indicating that a reasonable interpretation in terms of an integrated path length is possible.
Elastic Constants of Single-Crystal CaMg2
Authors: Sumer Ali , Smith J. F.
Published: April 2005

The five independent elastic constants of hexagonal CaMg2 have been determined by the ultrasonic pulse-echo technique over the temperature range, 100–300°K. In keeping with normal metallic behavior, the measured elastic constants do not fit the Cauchy relations. The degree of elastic isotropy is high, particularly so with respect to compressive or tensile strains. The compressibility of the compound is slightly less than the average of the compressibilities of the constituent elements. This compressibility behavior is reasonable on the basis of the small negative heat and volume of formation of the compound.
Comments on ``Thermal Conductivity in Two-Phase Alloys''
Authors: Ure Roland W.
Published: April 2005

It is shown that there is an error in Schroeder's calculation of the electronic thermal conductivity due to circulating currents in a two-phase material. With reasonable values for the properties of the two phases, quantitative agreement between the predictions of the model and the experimental data of Cosgrove, McHugh, and Tiller is obtained for both the electronic thermal conductivity and the Seebeck coefficient.
Transport in a Semiconductor with Anisotropic Mobilities and the Photopiezoresistance Effect
Authors: Van Roosbroeck W. , Pfann W. G.
Published: April 2005

Theory is given for current-carrier transport in nondegenerate semiconductors with anisotropic electron and hole mobilities and diffusivities. Two perpendicular principal directions are considered along each of which mobility of one carrier is maximum and mobility of the other minimum. This anisotropy might be obtained by elastic strain of a cubic semiconductor, or might occur without strain in certain semiconductors of noncubic structure. The ``photopiezoresistance effect'' in a slab with strongly absorbed radiation incident on one surface is analyzed in detail. Short-circuit current and open-circuit voltage between and electrodes are calculated, as well as efficiency of the transducer with an external load resistance. In the small-signal range, the current, voltage, and efficiency are proportional to photon absorption rate. In the large-signal range, with load matched for maximum power, similar proportionality holds for the current, while the voltage and efficiency have limiting large-signal values. For maximum power there is an angle of optimum orientation of the principal directions relative to the surface of the slab. It is determined by the ratio of the maximum relative mobility variations for the respective carriers. Maximum attainable efficiency, the large-signal value for pronounced anisotropy, is about 0.4 times thermal energy divided by the average energy required to produce one electron-hole pair; the numerical factor is the root of a simple transcendental equation. This efficiency is about 0.4% for germanium at room temperature, and is consistent with an estimate from small-signal theory with mobilities that are probably obtainable in strained material.
Infrared Wavelength Dependence of the Total Absorptivity of Electroplated Silver
Authors: Cline David
Published: April 2005

The total hemispherical absorptivity of electroplated silver at 75.8°K has been measured as a function of blackbody radiation temperatures from 268°K to 367°K. The measurements were made in a Dewar-like calorimeter. The total hemispherical absorptivity is found to increase with decreasing blackbody radiation temperature. Assuming a simple relationship between hemispherical absorptivity and normal absorptivity, the normal absorptivity increases with increasing mean wavelength.
Attenuation of Fast Electrons in Crystals and Anomalous Transmission
Authors: Heidenreich R. D.
Published: April 2005

The two-beam dynamical theory of electron diffraction (Laue case) with attenuation is treated using imaginary potentials and a damping vector α in the Schrödinger equation. Explicit formulas are obtained for centrosymmetric crystals when the Bragg condition is realized relating the damping vectors for the two wave fields with the mean imaginary inner potential P0 and the imaginary Fourier coefficient Pg.

Using a simplified model, the imaginary Fourier coefficients are expressed in terms of the imaginary potential Pf for nearly free electrons (plasma) and Pc for bound atom cores. It is shown that the imaginary potentials can be directly related to the total inelastic collision cross sections and absolute numerical values so calculated. The values computed in this way are sufficiently near experimental results reported in the literature to warrant confidence in the approach. For 105-V electrons, the damping vectors α are around 10−3 Å−1, and the imaginary potential Pf≅0.6 V.

The question of anomalous transmission or an electron ``Borrmann effect'' is considered on the basis of the results obtained. It is concluded at this stage that the effect will not be large for metals but will increase with atomic number and may become significant for Z>30. Uncertainties in both plasma and core electron cross sections make such predictions unreliable except for a few elements.

A calculation of the contribution of those electrons that have lost energy to E1<E indicates that the E1 electrons also can produce an ``anomalous transmission.'' A velocity filter will be necessary to distinguish this E1 effect from a true anomalous transmission.
Effects of Elevated Temperatures on the Fluorescence and Optical Maser Action of Ruby
Authors: Wittke James P.
Published: April 2005

Measurements are made of the wavelengths, linewidths, and fluorescent efficiencies of the fluorescent R1 and R2 lines in ruby, in the temperature range 300° to 500°K. The results are used to explain the degradation of ruby optical maser performance at elevated temperatures.
Alpha and Beta Grain Boundaries in Indium Antimonide
Authors: Mueller R. K. , Jacobson R. L.
Published: April 2005

Grain boundaries in indium antimonide with misfit angles of 6° have been prepared which, according to the dislocation model for grain boundaries, consist of rows of α or β dislocations. Current flow across these boundaries in n- and p-type material has been studied. Alpha boundaries were found to present a barrier to current flow in n- and p-type material, β boundaries only in p-type material. This indicates for α dislocations donor behavior in p-type material, acceptor behavior in n-type material and for β-dislocations donor characteristics. A theoretical model for the boundary states is proposed.
High Resolution Ammonia (N14H3) Maser
Authors: Holuj F. , Daams H. , Kalra S. N.
Published: April 2005

A N14H3 maser based on Ramsey's principle of separated oscillatory fields has been used to increase the resolution over a conventional maser. A single component of the 3.3 inversion line of N14H3 can be isolated. This type of maser overcomes the difficulties arising from the composite structure of the line.
Model for Transient Oscillations in a Three-Level Optical Maser
Authors: Kaplan Jerome I. , Zier Robert
Published: April 2005

The transient response of a three-level optical maser is calculated for a density of homogeneously broadened atoms coupled to one homogeneously broadened cavity mode. The atoms are treated in terms of the density matrix and the cavity mode is treated classically. Solutions are found analytically for the steady state and for the linearized form of two simplifications of the general equations. These special solutions have been previously obtained by Bloom and Statz and de Mars. Numerical solutions are found for a certain set of parameters. The response linewidth is found assuming one cavity mode coupled to a density of inhomogeneously broadened atoms.
Some Experimental Consequences of Flux Conservation within Multiply-Connected Superconductors
Authors: Hildebrandt Alvin F. , Elleman Daniel D. , Whitmore Frank C. , Simpkins Randall
Published: April 2005

A removable ferromagnetic core is used to increase the trapped flux in a multiply-connected superconductor. This original trapped flux is then compressed by a superconducting piston so as to produce an intense magnetic field within a relatively large volume. Additional experiments are described in which superconducting switches are used to compress the flux in a cyclic manner.
Specific Surface Area of Evaporated Aluminum
Authors: Swaine James W. , Plumb Robert C.
Published: April 2005

The variations in the specific surface area of evaporated aluminum due to substrate temperature, film thickness, and angle of incidence have been determined experimentally. Increasing the substrate temperature from 0° to 100°C decreases the specific surface area by a factor as large as 9. Increasing the film thickness from 3000 to 12 000Å increases the specific surface area by a factor as large as 17. The specific surface area increases with increasing angle of incidence and has been observed to change in the range of 1.0 to 25.2. Atomistic models for the growth of rough films from vapor are considered. One model which has been proposed in which asperities grow from islands which form during the initial stages of condensation is rejected on the basis of experiment. A second model in which asperities grow from crystallites having preferred crystallographic orientations is found to be adequate to explain the observations of this and certain other investigations.
Partition Effects in Transverse Electron Beam Waves
Authors: Hart P. A. H.
Published: April 2005

Theory is presented concerning the attenuation of the original beam waves, the fast, the slow, and two synchronous waves, and the generation of noise waves if part of the beam is intercepted.

To obtain compact equations matrix notation is used throughout. The matrix notation offers the additional advantage that both the behavior of the waves and their mutual correlation can be studied simultaneously. This renders the theory, which accounts both for pure interception and for partial scattering of the beam, much more general in nature. The electron beam diameter is finite.

In addition to attenuation of the original and generation of noise waves it is found that two new synchronous waves related to the original fast and slow waves are generated.

Experiments at 550 Mc with an Adler-Wade tube containing a movable vane show good agreement with the theory presented, provided the forward scattering is taken into account. The experiment indicates that the theory is probably correct at least insofar as the fast wave, the slow wave, and the correlated components of the synchronous waves are concerned.
Transverse Electron Beam Noise Described by Filamentary Beam Parameters
Authors: Blo/tekjær K.
Published: April 2005

The paper is concerned with the transverse velocity and position noise on electron beams. The equivalence between the actual noisy beam and a modulated filamentary beam is pointed out, and the frequency components of the equivalent filamentary beam modulation is calculated. It is shown that the transverse position noise is reduced by a factor Γ2, which is identical to the space-charge reduction factor for the longitudinal shot noise. The noise excitation is also expressed in terms of self-power and cross-power densities of the four normal modes on a rectilinear filamentary beam in a longitudinal magnetic field.
Applicability of the Taylor Theory of the Polycrystalline Aggregate to Finite Amplitude Wave Propagation in Annealed Copper
Authors: Bell James F. , Werner W. Meade
Published: April 2005

This paper provides additional experimental evidence for the Taylor theory of dislocations and the Taylor theory of the polycrystalline aggregate. For annealed copper (as had been found by Bell for annealed aluminum) the governing stress-strain curve for plastic wave propagation is a parabola, as predicted by the Taylor theory of dislocations. Using the Taylor theory of the polycrystalline aggregate, the parabolic stress-strain law for annealed copper, as had been shown earlier for annealed aluminum, is determinable from compression stress-strain curves for single crystals.

These experimental data in annealed copper are obtained from the free-flight constant-velocity impact of identical specimens using the diffraction-grating technique for the measurement of strain and surface angle.

From the results given in this paper, together with those obtained earlier by Bell for annealed aluminum and the recent results of Sperrazza for pure lead, it may be concluded that strain rate does not play a significant role in the dynamic plasticity of these annealed face-centered-cubic metals. As in annealed aluminum and pure lead, plastic strain propagation velocities, maximum strain amplitude, surface angle behavior, time of contact, and the coefficient of restitution for annealed polycrystalline copper are found to be given by the strain-rate independent theory of plastic wave propagation.
Properties of a Plasma Created by an Electron Beam
Authors: Hedvall P.
Published: April 2005

Some properties of a plasma formed by an ionizing electron beam have been investigated. The electron beam and the plasma were confined by an axial magnetic field. The experiments, which were performed in argon in the pressure range 5·10−5−1·10−3 mm Hg, showed that densities of the order 1012–1013 ion pairs/cm3 could easily be achieved. Some types of oscillations that occurred are discussed.
Containment of Plasmas by High-Frequency Electric Fields
Authors: Ericson Magda , Ward C. Seabury , Brown Sanborn C. , Buchsbaum S. J.
Published: April 2005

A cylindrical plasma column was produced in hydrogen by a microwave electric field crossed with a static magnetic field. Under certain conditions of gas pressure, magnetic field, and strength of the microwave field, the plasma did not entirely fill the volume available to it but appeared as a narrow, perfectly stable, cylindrical column with a diameter as small as one-fourth of the diameter of the discharge tube. The experimentally observed properties of this ``constricted'' discharge are described. It is shown that they can be explained by treating the plasma as a compressible dielectric medium.
Ferrimagnetic Resonance with Orthogonal and Parallel Pumping
Authors: White Robert M. , Schlömann Ernst
Published: April 2005

An rf magnetic field of sufficient amplitude gives rise to a nonlinear absorption caused by the unstable growth of certain spin waves. We have calculated the threshold for the case in which an rf field of frequency ω0 is applied orthogonally to the dc field and another rf field at frequency 2ω0 is simultaneously applied parallel to the dc field.

We find that under these conditions the wave number of the spin waves with the lowest instability threshold varies discontinuously with the ratio of the two rf magnetic fields. If the orthogonal rf field is relatively small, the unstable spin waves have wavelength comparable with the sample dimensions. In this region the critical parallel field decreases linearly with the square of the orthogonal field.
Study of the Growth Mechanism and Twin Habits of Ba2TiP2O9
Authors: Harrison D. E. , Tiller W. A.
Published: April 2005

Crystals of Ba2TiP2O9 were grown from the melt by the Bridgman technique. Two types of twinning occur, namely: growth twins and mechanical twins. The growth twins form with the (100) plane as the twin plane and mechanical twins form with the (001) plane as the twin plane. In twinned crystals, growth proceeds most rapidly in the [010] direction. Rapid growth in this direction is believed to result from efficient nucleation at the re-entrant corners formed by the 〈310〉 faces of the twin components. The mechanical twins form according to pseudo-merohedral symmetry by reflection across the (001) twin plane. The angle of obliquity is 4° and the twinning shear is 0.140.
Pressure Effects on the Internal Friction of Aluminum
Authors: Seely J. L. , Baker G. S. , Gibbs P.
Published: April 2005

Internal friction measurements were made as a function of hydrostatic pressures up to 3 kb by use of a piezoelectric torsional oscillator inside the pressure vessel, as well as with a Marx composite oscillator both before and after pressure treatment. Specimens were prepared by cold-working 99.99% aluminum polycrystals to a 50% reduction in width, followed by an anneal at 300°C. Measurements outside the pressure vessel showed that the strain amplitude dependence was irreversibly increased by amounts up to 1500% of the initial values as a result of the application of 3 kb for 15 min at 25°C. The original amplitude dependence was restored by annealing 15 min at 300°C. A subsequent compression again increased the amplitude dependence but to a lesser extent. After several such annealing-compression cycles there was no irreversible effect within 4% of background. Additional cold-work followed by annealing again produced the effect. The effect increased with increasing pressure. An increase in amplitude dependence of up to 600% also occurred in samples which had not been previously cold-worked. The internal friction at constant strain amplitude increased faster than linearly with increasing pressure and decreased linearly with decreasing pressure. Successive pressure cycles gave the same effect but with decreasing magnitude. After about 3 cycles, both increasing and decreasing pressure gave the same linear dependence of the damping, corresponding to within 8% of the background damping. It is suggested that irreversible dislocation effects might occur as the result of shear stresses produced near voids by the hydrostatic stress.
Coupling of Modes between a Slow-Wave Plasma Mode and a Helix
Authors: Paik S. F.
Published: April 2005

Propagation of waves in a transmission system consisting of a plasma column and a coaxial helix is investigated. The propagating characteristics of the structure are analyzed by a straightforward field analysis. It is demonstrated that the field solution can be reduced to a simple circuit equation describing two coupled tuned circuits. This analytical result shows that the propagation of waves in the plasma-helix structure can be described by a purely capacitive coupling of modes between the space-charge modes of plasma column and the helix mode. The result of this study is compared with the earlier Russian work by Bulgakov et al. The limitation of the perturbation techniques is discussed and the condition for the validity of the small perturbation assumption is given. The experimental method of separating and measuring the two coupled modes of propagation by means of mode-selecting techniques is described.
Microparticles Diodes
Authors: Maisonnier Ch. , Haegi M.
Published: April 2005

Using a simple model, the motion of an ensemble of small conducting spheres located between two parallel electrodes is investigated theoretically in the case where the flow is space-charge-limited. A more realistic but more complicated model is proposed. The experimental apparatus used to check the theoretical predictions is described; agreement between theory and experiment is fair. Possible applications of such diodes are mentioned.
Resistance of Elastically Deformed Shallow p-n Junctions
Authors: Rindner W.
Published: April 2005

Anisotropic elastic stress was applied to semiconductor surfaces parallel to the plane of shallow p-n junctions. The resistance of diffused and alloyed junctions was found to be highly stress-sensitive under both forward and reverse bias. Reversible resistance decreases under stress by factors of more than 103 were observed.
Electron Temperature in Partially Ionized Gases Subject to Intense ac Fields
Authors: Visvanathan S.
Published: April 2005

A strong external electric field in a plasma produces electrons with a temperature considerably higher than the temperature of the neutral gas in a plasma. We investigate here the currents produced by such electrons in a strong ac field. We discuss several cases of interest. Case 1 deals with the effect of a strong ac field on the plasma. It is found that the current has a component of frequency ω and a weaker component of frequency 3ω. The results are valid if ν0>ω>δν0. Here ν0 is the collision frequency of the electrons and δ is the fraction of energy transferred to the neutrals in a single collision. Case 2 deals with the effect of a strong steady electric field on which a weak ac field of frequency ω is superimposed. Here the current has a steady component plus an additional ac component of frequency ω which leads the ac field by a phase given by Eq. (33). Case 3 is similar to case 2 except that electron-ion collisions have been considered. The measurement of the current and phases should lead to a determination of the collision frequency.
Kikuchi Patterns from Evaporated Tin Films
Authors: Vook Richard W.
Published: April 2005

Evaporated single-crystal white tin films having an (001) orientation were examined by transmission electron diffraction. Sharp Kikuchi patterns were obtained and are discussed in terms of previous work. Their presence indicates a very high degree of crystal perfection in these ultra-high vacuum evaporated films.