bluuebunny/crossref_metadata_2025 huggingface dataset:
Directional Characteristics in Optical Heterodyne Detection Processes. II
Authors: Corcoran Vincent J.
Published: January 2005

The variation in the ac output current in a coherent optical-detection process as a function of orientation has previously been analyzed for point sources. The work is extended here to include finite sources, finite bandwidth, random-phase sources, and rough surfaces. The general expression for two finite sources in the Fraunhofer region indicates that the directivity is the product of the radiation patterns of the individual sources multiplied by the directivity of the detector due to point sources. For typical lasers the bandwidths are so narrow that the directivity is not practically affected by the finite width. ``White'' surfaces are shown to be equivalent to uniform surfaces with a random phase which is statistically independent from point to point. These surfaces are shown to have effectively the same directivity as far-field point sources.
Recoil of Fission Products in Homogeneous Carbon Structures
Authors: Evans R. B. , Rutherford J. L. , Perez R. B.
Published: January 2005

An experimental investigation of the average range of fission fragments in pyrolytic graphite was performed by exposing coupons of this material bearing a thin electromagnetically deposited layer of 235U to thermal neutrons. For the experiments, reliable and reproducible sectioning techniques were developed for the determination of ranges in thick targets with variable structure. The procedures used to obtain the range average in terms of the experimental data are described in detail, and an empirical formula for the calculation of ranges in pyrocarbons is given.

Analytical expressions were generated for describing the penetration of the recoil-fission fragments in the target material and evaluating various theoretical models of electronic and nuclear-stopping mechanisms in a reference structure. It was found that for carbons of homogeneous structure and with void sizes smaller than Bohr's straggling parameter, the penetration curves could be obtained as convolutions of a kernel of the form of a normal-distribution curve. For the thin extended sources used in this investigation, the various integrations performed mitigate straggling effects so that the only important parameter for data correlations is the average range, which was obtained for four mass chains in six different experiments. The values so obtained compared favorably with Lindhard's and Frank's microscopic models for the calculation of the average range in carbon.
Space-Charge-Limited Current of Holes in Silicon and Techniques for Distinguishing Double and Single Injection
Authors: Marsh O. J. , Viswanathan C. R.
Published: January 2005

Space-charge-limited (SCL) current of holes has been observed in high-resistivity silicon at room temperature through proper sample design and suitable choice of an upper limit for electric fields applied in the sample. Joule heating and hot-carrier effects, which limited the observation of SCL current in previous work, were hardly noticeable in our measurements. Current—voltage characteristics were measured and found to contain an Ohmic portion followed by a region that obeyed the theoretical space-charge-limited-current law J=(9/8)εμpV2/L3. This behavior has been verified for various samples differing in lengths by a factor of 10. The value of the incremental capacitance of the samples, when suitably corrected for fringing capacitance, was found to agree with the value (¾) C predicted by Shao and Wright for SCL currents, where C is the capacitance due to the sample geometry. Values of current were observed to be much greater on some samples than those predicted by the single carrier space-charge-limited-current law. The excess current was identified with double-injection behavior. The double injection was caused by a surface condition that allowed electrons to be injected at the negatively biased contact. Comparison with the capacitance—voltage characteristic and transient response behavior of double-injection structures aided in identifying the nature of the excess current.
Influence of a Superimposed Film on the Electrical Conductivity of Thin Metal Films
Authors: Chopra K. L. , Randlett M. R.
Published: January 2005

The resistance of thin continuous (100–1000 Å thick) Au, Ag, Cu, and Al films as influenced by super-imposed thin layers of conducting, semiconducting, and insulating materials has been studied. An overlay of SiO or Permalloy increases the resistance of Au films, but has little effect on Ag films. An overlay of Ge increases the resistance of Ag films by about 25%, but has negligible effect on Al films. The resistance of Cu films first increases with the thickness of the Ge and Cr overlay and then decreases rapidly to a saturation value. The changes in the resistance are markedly dependent on the thickness of the overlay; saturation values are obtained for an average thickness of less than 10 Å. Changes are observed for both diffuse and specular films. The observed changes are a function of the ratio of the thickness to the mean free path of conduction electrons and can be explained only by a change in the amount of diffuse scattering at the surface rather than in the specularity parameter. The data suggest that the formation of a new interface modifies the nature of the surface potential making both enhanced as well as reduced scattering of electrons possible and thus an increase or decrease of the resistance can result.
Self-Diffusion in Intrinsic and Extrinsic Silicon
Authors: Fairfield J. M. , Masters B. J.
Published: January 2005

Silicon self-diffusion coefficients were determined by studying the diffusion of 31Si into silicon crystals of various degrees of perfection and doping. For intrinsic silicon, the self-diffusion coefficient can be represented by D=9,000 exp− (5.13 eV/kT) cm2/sec. Doping above intrinsic levels increases the diffusion coefficient. It it is assumed that silicon diffuses by means of vacancies, which act as acceptors, the influence of n-type doping can be attributed to the increase in total vacancy concentration caused by the excess electrons through a mass-action principle. It is concluded that the vacancy mechanism is the most probable for silicon diffusion. The data of this investigation would indicate that the vacancy-acceptor level is about 0.34 eV below the conduction band in silicon.
Field-Ion Microscopy of Cobalt
Authors: Nishikawa Osamu , Müller Erwin W.
Published: January 2005

The hydrogen promotion technique for obtaining improved imaging condition for helium field-ion microscopy of cobalt is described. The image quality is satisfactory for viewing stacking faults, twin boundaries, and phase boundaries between hcp cobalt and fcc cobalt in atomic dimensions. The stacking faults are bunched in hcp cobalt, the individual faults being separated on the average by ten atomic layers of the basal plane. Most of the faults jog every 20–30 Å. Many, parallel, thin, fcc plates were found in an hcp matrix. No effect of grain size on the transformation from the fcc to the hcp structure was observed. The ratio of the quantities of the two phases was affected by a small amount of impurity, and cobalt wire from one source had an fcc structure throughout the accessible temperature range and could not be made to transform to the hcp structure by various heat treatments.
Metal Block Thermostats. II
Authors: Babb Stanley E.
Published: January 2005

A method for solving the heat equation for a particular set of discontinuous boundary conditions is presented. Calculated results are compared with a problem where the discontinuities have been averaged out. The method is of wider application than the present problem.
Free-Carrier Faraday Rotation of Dendritic InSb Films in the Microwave X-Band Region
Authors: White D. J. , Dinger R. J. , Wieder H. H.
Published: January 2005

Measurements were made of Faraday rotation on ∼1-μ-thick evaporated and recrystallized, polycrystalline InSb films. The experiments were carried out at room temperature using a microwave bridge circuit and a trimode turnstile as a polarimeter. The relative amplitudes and phases of the transmitted electric-field components were determined with the film placed transversely across a circular waveguide section (TE11 mode). Rotations of 30° to 40° were observed for a field of 2 kOe. The results are interpreted in terms of a theoretical model based on free-carrier Faraday rotation including multiple reflections assuming plane-wave propagation. The experimental data is in good quantitive agreement with the model for H<1.5 kOe and in qualitative agreement for higher fields.
Discontinuity Problem in an Anisotropic Waveguide
Authors: Mittra R. , Lee S. W.
Published: January 2005

The reflection of a dominant mode field at the junction of an air-ferrite interface in a rectangular waveguide is investigated. A singular integral equation is derived for the interface electric field on the basis of the quasistatic approximation. The integral equation is solved by using a function-theoretic technique. Closed-form solutions valid for the entire range of medium parameters are developed assuming that the ferrite is entirely lossless. It is shown that these solutions can be made to satisfy the realness condition on the discontinuity reactance for the entire range of medium parameters. The above condition which can be proven directly on the basis of the Hermitian nature of the permeability tensor of the lossless ferrite was not satisfied by the previously published solution for a partial range of medium parameters. Finally, the modifications caused by the presence of the losses in the medium are discussed briefly.
Interaction between a Magnetic Field and a Plasma Flow Behind a Shock Wave
Authors: Kuriki Kyoichi
Published: January 2005

A theoretical calculation is made from which the electrical conductivity or magnetic Reynolds number of a shock-produced plasma flow can be derived. The results of the analysis predict the effects of the transient magnetic field induced by the interaction between the applied magnetic field and the plasma flow behind a shock wave. The applied magnetic field considered is transversal to the flow. Its intensity is either steady in time and increasing linearly in the flow direction or spatially uniform but increasing linearly with time.

If the applied field extends to infinity, the intensity of the induced magnetic field is proportional to the magnetic Reynolds number and to the intensity of the applied magnetic field. With the aid of the present analysis the magnetic Reynolds number can be determined by comparison of the measured field and the calculated magnetic field. This method is applicable even if the magnetic Reynolds number is greater than unity. The effects of the finiteness of the applied field are considered.
X-Ray-Diffraction Topographic Studies of Magnetic-Domain Configurations in Terbium Iron Garnet
Authors: Basterfield J. , Prescott M. J.
Published: January 2005

The method of x-ray-diffraction topography, which is briefly described is applied to the study of magnetic domains in a single-crystal sample of Tb3Fe5O12. Comparison is made with the same domain structure observed by transmitted polarized light and Bitter patterns, and a general interpretation of the diffraction topograph is suggested. Finally, the possible applications of the technique, particularly with respect to garnet materials, are briefly discussed.
Electromagnetic Scattering from Free-Space Impedance Homogeneous Spheres
Authors: Sawchuk Walter , Trotta Robert
Published: January 2005

The problem of electromagnetic scattering by homogeneous spheres with relative impedance equal to unity is considered. From the Mie series expression for the induced internal fields, the details of the condition responsible for producing a null in the backscattering cross section are deduced. The existence of this null is attributable solely to destructive interference, regardless of frequency, and is valid for either lossy or lossless media. The returned signal in the vicinity of the null is determined from numerical computation of the bistatic cross sections.
Two-Dimensional Model for a Domain Wall
Authors: Aharoni Amikam
Published: January 2005

The magnetization vector in a conventional Néel wall between ferromagnetic domains is modified by a sinusoidal variation along the film thickness. Outside a small ``kernel'' region, the volume charge is cancelled by an appropriate choice of the second component of the magnetization vector (along the film thickness), while the surface charge vanishes everywhere along the wall. This configuration yields a wall energy which is somewhat smaller than the energy calculated by Brown and LaBonte as an absolute minimum of all one-dimensional wall configurations, at least in the thickness of 103 to 104 Å in Permalloy. Since this is the thickness range in which the so called Bloch walls are usually observed experimentally, it seems that these walls do not have the one-dimensional structure that is assigned to them, which can at most take place in bulk materials. For thickness of Permalloy much larger than 104 Å, the energy of the new wall becomes larger than that of the conventional Bloch wall, and eventually it tends to infinity for an infinite film thickness.
Computer Studies of Xenon-Ion Ranges in a Finite-Temperature Tungsten Lattice
Authors: Harrison D. E. , Greiling D. S.
Published: January 2005

We have simulated the passage of heavy ions through a tungsten crystal in which the atoms are thermally displaced and the ions are subjected to a force which represents inelastic-loss mechanisms. Semiempirical Born-Mayer potential functions and inelastic-loss parameters were obtained for the xenon-tungsten and krypton-tungsten systems. Only the xenon-tungsten system was studied in detail. We find that below 500°K thermal displacement of the lattice atoms has little effect upon the collision dynamics for ions moving in the channel center. Energy losses to electronic processes during collisions are calculated, and the loss rates compared to the simulation loss rate parameter. Agreement is good. Simulated integral-penetration curves agree quite well with the experimental results. A mechanism which attributes the strong temperature dependence of ranges to variations in the inelastic-loss constants is presented and compared to experimental results.
Thermal Conductivity and Heat Capacity of the Monocarbide, Monophosphide, and Monosulfide of Uranium
Authors: Moser J. B. , Kruger O. L.
Published: January 2005

The heat-transport properties and heat capacity of UC, UP, and US were determined between room temperature and 600°C. These properties were measured by a transient technique with a laser as a heat pulse source. The thermal conductivity was calculated from the product of the thermal diffusivity, heat capacity, and density. At room temperature the thermal conductivity of the three compounds corrected to theoretical density was found to be 0.057, 0.033, and 0.021 cal sec−1 cm−1°C−1 for UC, UP, and US, respectively. At 600°C the value for UC decreased to 0.041 cal sec−1 cm−1°C−1. The thermal conductivity of UP remained equal to its room-temperature value and that of US increased to 0.029 cal sec−1 cm−1°C−1. The room-temperature heat capacity values for the three compounds investigated were all slightly above 12 cal mole−1°K−1. At 600°C the heat capacity of UC increased to 15.2 cal mole−1°K−1, whereas no appreciable changes were found for UP and US at this temperature. The experimental heat-capacity values were used to formulate expressions of the type Cp=a+bT+cT−2 with the aid of a computer program, and enthalpies and entropies of the compounds were calculated from 400° to 1000°K.

The electronic contributions to the thermal conductivities of the three compounds were calculated by means of the Wiedemann-Franz law with the Lorenz constant for metallic conductors. The limitations of this approach are discussed and an alternate method of separating the phonon from the electronic part of the thermal conductivity is presented. A value of 0.02 cal sec−1 cm−1°C−1 for the lattice conductivity alone was obtained. This value is close to the 0.01 to 0.02 cal sec−1 cm−1°C−1 obtained by using the Wiedemann-Franz law on UP and US. The thermal conductivity of UC above 300°C can be ascribed to electrons if the traditional Lorenz constant is used. However, comparison of the thermal and electrical conductivity for the three compounds indicates that the Lorenz number when applied to UC should be lower, possibly because of the presence of optical scattering. It was found that the lattice resistance to the flow of heat in this group of compounds is essentially temperature independent and that calculations based on the classic models do not give good agreement with measured values.
Deformation Theory of Hot-Pressing
Authors: Kakar Ashok K. , Chaklader A. C. D.
Published: January 2005

The possible deformation behavior of spheres in a compact has been both theoretically analyzed and experimentally verified. The change in contact area radius a relative to the particle radius R has been related to the bulk density and bulk strain for four possible modes of packing: simple cubic (Z=6), orthorhombic (Z=8), rhombohedral (Z=12), and body-centered cubic (Z=8).

An equation relating the above parameters can be represented by D−D0=32D0(a/R)2 for different types of packings, D and D0 being densities at any a/R and a/R=0, respectively. It has been shown experimentally by deforming lead spheres at room temperature, 50° and 100°C in a cylindrical die, that the over-all deformation is similar to that of the orthorhombically packed monosized spheres. A change in the coordination number Z during the deformation process was also observed and may account for the deviation from the theoretically predicted values.

Similar experiments using sapphire spheres were carried out in the temperature range 1570°–1700°C, and the results showed that the deformation behavior was very similar to that of the lead spheres.
Injection and Emission of Hot Electrons in Thin-Film Tunnel Emitters
Authors: Savoye E. D. , Anderson D. E.
Published: January 2005

Results of studies of Al-Al2O3-(Au or Al) thin-film emission diodes are in agreement with a model based on electron injection by internal TF emission with subsequent energy loss in the insulating film, characterized by isotropic scattering with energy loss ΔE=0.1 eV and mean free path λi=6 Å. The experimental results for Au overlayer films are found to be consistent with a modified ballistic transport model allowing weak elastic interactions, with a value for the electron-electron scattering mean free path at 7.0-V bias of λe∼47 Å. Low-energy electron bombardment of the thin-film sample is found to allow detection of overlayer-film porosity, and a quantitative assessment of hot electron emission through holes in Au overlayer films is obtained. The results indicate that preferential electron emission through holes in pure Au films is not of significance over the entire range of Au film thicknesses studied; this conclusion is substantiated by results obtained with composite Al-Au-overlayer films.
Application of the Theory of Heat Conduction to the Absorption of Blackbody Radiation
Authors: Harrington R. E.
Published: January 2005

Formal transport theory for heat conduction requires a constant thermal gradient over a small but finite distance if Q=−KdT/dx is to be a good approximation. The kinetic model is used to show that this relation holds within 2% if the gradient is constant over a minimum range of ±5Λ, where Λ is the mean free path of electrons in metals. The usual differential equation of heat conduction cannot be applied to the absorption of blackbody radiation by metals if the absorption coefficient is high, since it overestimates the effect of thermal conduction and does not give the correct temperature distribution within the first few mean free paths from the surface.
Technique for the Determination of Dynamic-Tensile-Strength Characteristics
Authors: Breed B. R. , Mader Charles L. , Venable Douglas
Published: January 2005

A technique for the examination of the dynamic-tensile-strength characteristics of materials is presented. The dependence of tensile strength upon stress gradient, hence stress rate, is demonstrated for Al, Cu, Ni, and Pb. The results were tested and found to be self-consistent in that once the dynamic-tensile-strength characteristics have been measured they can be incorporated into the numerical calculations, which then can be used to predict complex multilayer spall behavior even in layers of dissimilar materials.
Linear Electro-Optic Retardation Schemes for the Twenty Classes of Linear Electro-Optic Crystals and their Applications
Authors: Hu Chia-Lun
Published: January 2005

All possible linear electro-optic retardation schemes for the twenty classes of linear electro-optic crystals are synthesized in this paper under the single condition that light does not split directionally in a crystal. The result of this synthesis is tabulated in Table II. It gives the retardation and permissible polarization formulas for each class of crystals. It, therefore, may be used as a guide for designing linear electro-optic devices. As an example, a linear transverse scheme for class 4̄2m crystals (KDP, ADP) is selected from this table and verified experimentally. In this scheme, light is along (110) and electric field is along (001). This particular scheme has as advantages: no need for transparent electrodes and that the induced retardation can be increased by increasing the length-to-width ratio of the crystal. Table II depicts also the variations of retardation and permissible polarizations as the direction of light and electric field change under the above condition. This provides the reader with a foundation for synthesizing the electro-optic-polarization modulation and single-side-band-suppressed-carrier modulation (SSBSC). Again, as an example, a new scheme using cubic crystals for single-side-band and/or SSBSC modulation is proposed in this paper.
Effects of Band-Bending on Energy Distribution Curves in Photoemission
Authors: Kindig N. B.
Published: January 2005

A theory is presented which provides insight into the effects of band-bending on the energy distribution of photoemitted electrons. A ``band-bending distribution function'' is introduced to relate the energy distribution of electrons when band-bending is present to that when no band-bending is present. Specific band-bending distribution functions are presented for an exponential, a linear, and a more complicated dependence of potential on distance from the surface. Significant differences between the effects of upward and downward band-bending related to apparent electron affinity and energy shifts in structure are discussed. The accuracy of the analysis improves for electron energies well above the threshold for escape. The density of surface states on homogeneous material required to produce observable effects due to band-bending is estimated.
Viscous Ultrasonic Attenuation in Metals
Authors: Gobran N. K. , Youssef H.
Published: January 2005

Using a pulse technique, the attenuation of longitudinal ultrasonic waves is measured in polycrystalline aluminum, cobalt, nickel, and copper, respectively, in the frequency range from 1 to 15 Mc/sec. The metals have previously received different treatments of loading and annealing. The measurement is extended, for nickel, in the temperature range from −78° up to 450°C. The results indicate that the attenuation-frequency curve can be divided into two parts: In the low frequency part, the (attenuation)2 varies linearly with frequency; the high-frequency part exhibits a constant attenuation corresponding to a diffusion loss as previously reported. The loss associated with the parabolic part is attributed to a viscous origin as that considered in boundary layers. The interaction of a dislocation-free volume and the surrounding dislocations (as a fluid) could explain qualitatively and quantitatively the parabolic viscous behavior.
Interaction of Dislocation Dipoles with Surfaces
Authors: McNeil M. B. , Grosskreutz J. C.
Published: January 2005

Using recent work by Conners on dislocation-image forces, it is shown that, in the isotropic elastic-continuum approximation, the forces of interaction between edge-dislocation dipoles and free or coated surfaces vanish to terms of order r−2, where r is the distance between the dislocation dipole and the surface. This is as would be expected from the response of dislocation dipoles to stress fields.
Intensity of X Rays Diffracted from an Elastically Vibrating Single-Crystal Plate
Authors: Haruta K.
Published: January 2005

The intensity of the x-ray beam diffracted from a single crystal changes when the crystal lattice is distorted. An elastically vibrating quartz plate driven piezoelectrically was used to study relationships between diffracted intensity and lattice distortions for the case of Laue geometry with μt∼1. The main advantages in studying the distortions of a plate vibrating at resonance are that the shape of the displacement of the lattice is amenable to mathematical analysis and that the amplitude of vibration can be varied continuously. Integrated intensity of the diffracted x-ray beam was measured as functions of the position in the crystal plate, the amplitude of vibration, and the phase of a vibration cycle. The following conclusions were drawn, which demonstrate and verify some predictions made by the dynamical theory of x-ray diffraction for a distorted single crystal for the nonabsorbing case: (1) For an intensity change to occur, the distortion in the net plane must have a component along the diffraction vector and have a nonzero second derivative in the plane of diffraction. (2) The measured integrated intensity is a monotonically increasing function of lattice distortions and closely follows the theoretical curve. (3) Increases in the diffracted intensity are independent of the sign of the second derivative of the displacement.
Permeability of Some Oxides and Metals at Low Temperatures
Authors: Van Groenou A. Broese
Published: January 2005

Low-temperature measurements are reported on the initial permeability (μ) of a number of polycrystalline MnZn- and NiZn-ferrites and yttrium iron garnet. In the temperature range of liquid helium, the unsubstituted samples of YIG, NiZn-ferrite, and MnZn ferrite show a μ value of about 60. A time dependence of μ after demagnetization was observed for these samples.

Alloys of composition NixFe1−x show much higher values of μ. At 4°K for x=0.5, a value of μ=3000 is found, together with a coercive force of 0.3 Oe. For x=0.35 and 0.40, a threefold increase in μ is observed between 4° and 20°K. The other alloy samples all have a temperature-independent permeability up to 100°K.
Energy Spectra of Inelastically Scattered Electrons and LEED Studies of Tungsten
Authors: Tharp L. N. , Scheibner E. J.
Published: January 2005

Energy distributions of the electrons inelastically scattered from the tungsten (110) surface for primary energies of 50–350 eV have been obtained using a modified LEED system. The information contained in these secondary electron energy distributions has been coupled with LEED patterns, thereby affording a more complete understanding of the electron scattering processes in the low-energy range. The physical processes contributing to the characteristic losses and other features observed in the energy spectra are discussed, and the expected behaviors are compared with experimental observations. LEED patterns are used to characterize sample-surface conditions.
Bragg Scattering of Infrared Radiation from Coherent Spin Waves
Authors: Auld B. A. , Wilson D. A.
Published: January 2005

A calculation of the characteristics of the Bragg scattering of near-infrared laser light (1.15μ wavelength) from coherent spin waves in ytrrium iron garnet is presented. Previously available experimental data on Faraday rotation is used to determine the magneto-optic coefficient. The calculation is then made by considering the spin wave as a source of a spatially varying index of refraction. The ratio of scattered power to incident power for a saturated spin-wave beam of π-mm2 cross section is calculated to be −63 dB at a spin-wave frequency of approximately 1 GHz.
Diffraction Effects in Lorentz Microscopy
Authors: Wohlleben Dieter
Published: January 2005

Several electron optical techniques are in use to study microscopic magnetic field distributions through deflection by the Lorentz force (Lorentz microscopy). It is shown that for most cases of practical interest the deflected electrons must be treated quantum mechanically in order to extract quantitatively information on the structure of the field inhomogeneity from the experimental electron record. The lateral wave-length of an electron deflected in a weak magnetic field is independent of the initial electron momentum and is often of the order of the lateral extent of the structure under investigation. For instance, in ferromagnetic thin films, λlat≈1000 Å behind domain walls 3000 Å wide, or λlat≈10 μ behind ripples with 2 μ period. It is well known that the geometric approach to contrast formation can break down in such cases (Abbe's sine condition).

High-resolution micrographs of ferromagnetic layers are shown. In the defocused mode, one interference fringe appears in the image per flux unit h/2e in the layer near convergent walls. In the Foucault mode, the transition from bright to dark areas of the image occurs across a finite distance due to diffraction. This distance corresponds to the width of one flux unit h/2e in the layer.

Ripple contrast is smaller than one and is a complicated function of defocusing distance, ripple period, and initial electron momentum due to diffraction. High-frequency-ripple Fourier components tend to be damped in the image, and certain components cannot at all produce any contrast.

Lorentz contrast from the Abrikosov lattice in hard superconductors is expected to be qualitatively similar to, but weaker than, ripple contrast. The Foucault mode is shown to be inferior to the defocused mode for quantitative high-resolution Lorentz microscopy.
Electron Emission from Metal-BaO Systems
Authors: Dore B. V. , Geppert D. V. , Muller R. S. , Spicer W. E.
Published: January 2005

A model is proposed to explain the electron-emission properties of metals coated with thin evaporated films of BaO. The model considers the BaO-metal interface to be rectifying, and the interior of the BaO layer to have a large density of donor sites. Experimental data from both this laboratory and the literature, pertaining to both thermionic and photoelectric emission properties, are shown to be consistent with predictions based on the proposed model. A striking enhancement is reported in the photoemission from BaO-coated cathodes that are either bombarded by electrons or heated. The theory developed explains the observed dependence of work function on BaO-layer thickness, the observed independence of emission work function on the work function of the substrate metals, and the effects of nonuniform BaO deposits on electron-emission properties.
Zero-Field Solutions and Their Stability in the One-Dimensional Low-Pressure Cesium Diode
Authors: Burger Peter
Published: January 2005

The dc potential solutions which have zero slope at the emitter are calculated and examined for the low-pressure cesium diode. It is assumed that ions and electrons are emitted thermionically at the emitter with a given ratio of ion-to-electron saturation currents and a positive dc potential is applied to the collector. Furthermore, the potential is nowhere negative in the diode and electron saturation current flows through it. This assumption limits the range of α's to 0<α<1, where α is the ratio of ion-to-electron saturation currents times the square root of the ratio of their masses. It was found by Auer and Hurwitz that monotonically increasing potential solutions can exist only for the range of α's, 0<α<0.405. In the range 0.35<α<0.405 we found large amplitude oscillations in the diode by computer simulation methods. The static solutions for α<0.35 were found stable. For 1>α>0.405 the static potential solutions have a long zero slope region within the diode or become periodic in space. All these solutions were found unstable and nonexistent in the diode that operates under time-varying conditions just as predicted by Auer and Hurwitz.
The Non-Self-Similar Propagation of a Thermal Radiation Front
Authors: Parks D. E.
Published: January 2005

The non-self-similar diffusion of energy from an enclosure is investigated for plane parallel geometry for the case where the transport of energy is purely radiative. The energy released instantaneously in the cavity is partitioned in arbitrary proportions between radiant energy and internal energy of matter. The mean free path of radiation in the walls bounding the enclosure varies as the cube of the temperature, but the material within the enclosure is assumed to be transparent to radiation.

Solutions for the non-self-similar radiative diffusion of radiation from the cavity are expressed in parametric form and numerical results are displayed graphically. In addition, series solutions are given which apply in the limit of short and long times after the initial release of energy in the cavity.
Some Studies of Electron Cyclotron Echoes from Plasma
Authors: Harp R. S. , Bruce R. L. , Crawford F. W.
Published: January 2005

This paper describes a single-particle collisional theory of the two- and three-pulse echo trains that are stimulated when a magnetoplasma is subjected to repeated pulses at the cyclotron frequency, and presents results of a series of experiments supporting the applicability of the theory. A major prediction of the analysis that has been confirmed experimentally is that, when dissimilar pulses are applied, an arbitrary pulse shape can be stored and recalled. The possible applications of echo phenomena to the study of collision processes, and in memory devices, are discussed briefly.
Quantum Statistics of Multiple-Mode, Superposed Coherent and Chaotic Radiation
Authors: Lachs Gerard
Published: January 2005

This paper is concerned with the determination of the quantum statistics of the photoelectric detection, and the E-field detection of multiple-mode superposed chaotic and coherent radiation. The Glauber P-representation is utilized extensively, and results are obtained by a fully quantum-mechanical treatment. The generating function, the mean, and the variance of the photocount statistics are derived for illumination times of arbitrary duration and for modes of arbitrary statistical interdependence. For short illumination times, the complete photocount distribution is obtained. The distribution has the same form as that for a single mode of superposed chaotic and coherent radiation. The multiple-mode distribution, however, is nonstationary. The difference between experimental determinations of the mean and variance which utilize periodic sampling and those which utilize random sampling is derived. A method for determining the P-representation for modulated fields is described, and the detection statistics are derived. The statistics of the E field are found to be Gaussian, and it is found that for multiple-mode classical statistics and quantum statistics differ.
Noise in Metal Bolometers
Authors: Li S. C. , Chen T. M.
Published: January 2005

The impedances and the noise generated in the Narda model N821B metal bolometers with direct current passing through them are measured over the frequency range of 1 to 100 kc/sec. The impedance measurements indicate that the impedance of the bolometer consists of resistive part and capacitive-reactance part. This agrees with IΔV effect discussed by Becking and van Vliet. The noise measurements indicate that large amounts of noise over Johnson noise are associated with the temperature-fluctuation noise and 1/f noise in the bolometer when direct current is passed through it. For a bias current lower than 6 mA, the temperature-fluctuation noise predominates and the observed noise has spectral distribution in agreement with the theoretical results obtained by Milatz and van der Velden. For a higher current (8.7 mA), the observed noise shows 1/f characteristics.
Nucleation of Magnetic Domain Walls in Single-Crystal Ferrites
Authors: Baldwin John A.
Published: January 2005

A model for the nucleation of magnetic domain walls in single-crystal window-frame samples of ferrite is presented. It is assumed that the wall exists prior to the application of an external field and that it is attracted to the surface by an effective pressure due to surface tension and interaction with surface defects. This pressure is nonconservative since it depends on the direction of wall motion as well as position. Using this model it is possible to explain the experimental dependence of wall velocity on time and of nucleation time on applied field.
Self-Decoration Effect in Lithium Ferrite
Authors: Lessoff H. , Childress J. D.
Published: January 2005

A self-decoration effect has been observed in thermally etched polycrystalline lithium ferrite. Each decoration is generally characterized by a geometric symmetry which apparently is related to and indicative of the crystallographic orientation of the surface on which it is found. An explanation for the formation of these decorations is proposed.
Recombination Processes of the Green-Edge Emission of Red-Excited CdS at 4.2°K
Authors: Condas George A. , Yee Jick H.
Published: January 2005

The two-stage, green-edge fluorescence at 4.2°K of single crystals of CdS excited by laser-produced red light was examined. The green-edge emission was found to be very similar to that produced by ultraviolet excitation. However, a green-edge shift to longer wavelengths, as well as no evidence of a blue-edge emission, was found. These effects could be explained by the existence of a distant-pair recombination process for the green-edge emission, and a low rate of free electron—hole production.
Magnetic Susceptibilities of Some Rare-Earth-Zinc (RZn2) Intermetallic Compounds
Authors: Ray D. K. Deb , Ryba Earle , Mulay L. N.
Published: January 2005

Data on the paramagnetic susceptibilities of the rare-earth-zinc intermetallic compounds, NdZn2, SmZn2, GdZn2, TbZn2, HoZn2, and YbZn2, in the 77° to 300° K region, are presented. The susceptibility obeys the Curie—Weiss law for all the compounds except YbZn2. YbZn2 has a susceptibility which is negative at room temperature but positive at lower temperatures. The data obtained from the paramagnetic region for the other compounds, except GdZn2, yield effective magnetic moments in agreement with the theoretical moments for the corresponding free tripositive ions. The reason for the anomalous value for GdZn2 is not understood.
Charge Collection in Silicon Detectors Operated with Field Region Less than Range of Alpha or Beta Particles
Authors: Keywell Frank
Published: January 2005

The collection of charge in a silicon detector was studied for ionizing radiation of alpha and beta particles. In particular, the characteristics were studied for the case wherein the space-charge width of the detector is less than range of the ionizing particle. In this case there may be charge collection due to diffusion of electrons or holes to the edge of the space-charge region. The factors related to this type of collection are combined in a function termed the back-collection factor which is defined in an integral equation relating number of electron—hole pairs collected as a function of space-charge width. The back-collection factor is considered a function of distance from edge of space-charge region and amplifier-integration time. A method to calculate the back-collection factor as a series expansion is presented. Experimental data for 8.78- and 5.48-MeV alpha particles was analyzed to determine the range of back-collection and the form of its dependence on distance and integration time. The range of back-collection varies from 33 to 50 μ for integration time 0.1 to 5.0 μsec for 8.78-MeV alphas in silicon. Similarly, for 5.48-MeV alphas it varies from 16 to 52 μ. Beta particles required a different treatment because of their distribution of curved trajectories in a solid. The effect of this distribution in trajectories was considered in relation to the response of a silicon detector when space-charge width is less than range. It was noted that the previous experimental work by Agu et al. on absorption of electrons in aluminum foils of varying thickness should be in agreement with the count rate at full energy for a silicon detector when the albedo is included in the calculations. Experimental measurements were made on the number of electrons at full energy as a function of space-charge width for 264-keV conversion electrons from 203Hg and these were shown to be in agreement with Agu's data. The results support the view that solid-state detectors may be used to measure ionization effects within the solid from which they are constructed.
Diffusion in Silicon. I. Effect of Dislocation Motion on the Diffusion Coefficients of Boron and Phosphorus in Silicon
Authors: Parker T. J.
Published: January 2005

A simple dislocation-enhanced diffusion model is proposed to explain the anomalous diffusion of phosphorus and boron in silicon. Jogs created by dislocation intersections undergo climb and emit vacancies as they are carried into the crystal on gliding diffusion-induced dislocations. It is shown that the resulting increase in the vacancy concentration may be fully adequate, when occurring in conjunction with the field-aided diffusion mechanism, to explain the enhanced diffusion.
Diffusion in Silicon. II. Enhanced Diffusion of Phosphorus in Silicon
Authors: Parker T. J.
Published: January 2005

It has recently been reported that the enhancement of the rate of diffusion of phosphorus in silicon in the high concentration range is substantially reduced when the surface concentration is increased beyond a critical value. In this paper it is shown that this effect is consistent with a model which explains the anomalous diffusion by the generation of excess vacancies from edge jogs during the glide of diffusion-induced dislocations into the crystal.
Investigation of Copper Diffusion in Bi2Te3 by Etching Technique
Authors: Sagar A. , Faust J. W.
Published: January 2005

Copper diffusion in bismuth telluride crystals in the room-temperature range was studied by etching technique. Small etch pits due to copper particles along the dislocations were observed in samples in which copper was diffused for a few hours at room temperature. Such pits were not observed along the dislocations in samples in which copper diffusion at room temperature took place for a few days. This suggests that pits observed for short diffusion times represent copper diffusion along the dislocations. No such evidence was found for copper diffusion along dislocations in the high-temperature range.
Photoconductivity of Chromium-Doped Gallium Arsenide
Authors: Broom R. F.
Published: January 2005

Measurements of the dc photoconductivity of chromium-doped semi-insulating GaAs have been made in the wavelength range 0.5–2.0 μ at temperatures of 290° and 80°K. High photoconductive gains of greater than 1000 have been observed with a low light level response extending to less than 10−14 W. A sharp peak in the response is observed at a wavelength of 1.40–1.45 μ having an external photoconductive gain of the same order of magnitude as that at the band edge. Possible mechanisms for this peak are discussed.
Gain Saturation in Neodymium: Glass Laser Amplifiers
Authors: Cabezas A. Y. , McAllister G. L. , Ng W. K.
Published: January 2005

Gain saturation in an Nd3+:glass (Corning 0580) laser amplifier has been investigated using a normal laser driving signal. The study shows that only the average power of the driving signal need be specified. The experimental results obtained agree with the steady-state theory of Schulz-DuBois on the gain saturation of an amplifier with loss. This leads to a value of 3.5±1.0×10−20 cm2 for the amplifier stimulated-emission cross section σa. From this and the measured value of 3.3×103 sec−1 for the spontaneous emission rate A, the critical saturable power Pc is calculated to be about 20 kW/cm2. Pc is defined as the level that reduces the unsaturated steady-state inversion density by 3 dB; it is given approximately by AhvL/σa. When unsaturated, the steady-state gain of the amplifier studied was 29.3±3.8 dB; correspondingly, the gain coefficient β was 0.34±0.04 cm−1 and the inversion excitation rate W was about 30 sec−1. When driven to saturation by 82.5 kW/cm2 (the maximum normal laser driving power used in the experiment), 3.0±0.2 dB of steady-state gain was measured. The loss coefficient α of the amplifier was found to be 0.011±0.002 cm−1 at 1.06 μ.
Charge-Carrier Mobility in Polycrystalline Semiconducting Films Based on Bulk Single-Crystal Theory
Authors: Ramey R. L. , McLennan W. D.
Published: January 2005

The temperature and thickness dependence of charge-carrier mobility in vacuum-deposited germanium films can be represented by the relation 1/μe=1/μL+1/μI+1/μd+1/μF,where the first three terms represent the lattice, impurity, and dislocation scattering in bulk material. The term μF is a function of the surface scattering of the carriers as well as of grain-boundary effects. Thus film-size effects are represented in a large part by the fourth term which satisfies the empirical relation 1/μF=A log(δ/a).For the films studied, this is the dominant term for polycrystalline films less than 5000 Å in thickness or single-crystal films less than 1800 Å in thickness.

The measured value of the coefficient A was 0.0219 V·sec·cm−2 for our polycrystalline films and 0.0176 for the single-crystal films of Sloope and Tiller. The characteristic thickness, δ, was found to be dependent upon grain-boundary scattering, having a value of 8000 Å for polycrystalline films as compared to 2000 Å for the single-crystal films.
Stacking-Fault Contrast in X-Ray Topographs of Annealed Si Web Dendrite
Authors: Meieran Eugene S. , Blech Ilan A.
Published: January 2005

X-ray topographs of annealed Si web dendrite showed the presence of immense stacking faults lying parallel to the web surface. In all cases, the faults were bounded by 〈112〉 partial dislocations, which formed many unusual and complex dislocation networks. In many areas, both extrinsic and intrinsic stacking faults were observed in a single (111) plane, along with nonfaulted crystal regions. The fault and dislocation contrast were generally explainable in terms of dynamical diffraction theory.
Observation of Irradiation-Induced Interstitial Copper Impurity in Germanium
Authors: Hiraki A. , Cleland J. W. , Crawford J. H.
Published: January 2005

The possibility that substitutional impurities can be displaced into interstitial sites in germanium by electron irradiation was investigated by electrical property measurements. The impurity chosen was copper since it is a triple acceptor in a lattice site, but is a donor when interstitial; hence, ejection of a single copper atom adds four electrons to the conduction band. Specimens of n-type germanium doped with both copper and antimony (the ratio of Cu to Sb was ∼1:4) were irradiated with 1.6-MeV electrons at 77°K along with control specimens that contained no copper. The decrease in electron concentration n was appreciably less in the copper-doped specimen than in the control specimen, as would be anticipated if copper impurities were displaced into interstitial sites. Isochronal annealing at several temperatures between 77° and 260°K after irradiation produced a further decrease in n (reverse annealing) in the copper-doped specimens, whereas the control specimens showed a normal recovery of n. A likely explanation of the reverse annealing is that of restoration of irradiation-produced interstitial copper into substitutional sites through interaction with migrating vacancies. A type of negative photoconductivity was also observed in the temperature range in which reverse annealing occurred.