bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Frequency Laser Interferometry in Plasma Diagnostics
Authors: Gerardo J. B. , Verdeyen J. T. , Gusinow M. A.
Published: April 2005

The time response of the laser interferometer is studied, and the parameters that are instrumental in limiting its time response are discussed. It is shown that by judicious selection of parameters the laser interferometer is capable of detecting resonances in excess of 50 per microsecond, which is close to the theoretical limit of the resonant structure used. The applicability of the interferometer to measurement of very rapidly changing plasma electron densities is demonstrated.
Behavior of Young's Modulus of a Beta Brass Single Crystal for Various Quench Temperatures
Authors: Martin M. C. , Camp H. E.
Published: April 2005

The standard direct strain method was used to determine the effect on Young's modulus of quenching beta brass in a saturated salt solution. The measurements were made on one beta brass single crystal with orientation function f(l, m, n)=0.121. The measurements were performed at the temperatures of 25°, −30° −90°, and −196°C. From the measurements the reciprocal of Young's modulus was calculated and two anomalous points were determined. The increase in Young's modulus for the quench temperature of 275°C was attributed to isolated wrong pairs of atoms. The increase in Young's modulus at the quench temperature of 450°C was attributed to disorder being quenched in.
Desorption Time Measurements using ac Modulation Techniques
Authors: Perel Julius , Vernon Richard H. , Daley Howard L.
Published: April 2005

A technique was developed to measure the desorption time for ion emission from a heated surface using phase-sensitive lock-in detection of modulated alkali metal atom beams. This technique is described, together with the derivations of equations which relate the desorption time to experimental parameters. The relationships obtained show the dependence of the amplitude and phase of the ion emission ac signal upon the desorption time (i.e., the mean time that adsorbed particles spend upon a heated surface before being emitted as ions.) The measurable effects upon the signal as the desorption time increases are the attenuation of the amplitude and the phase shift of the modulated wave. A description of ac ion emission characteristics is included along with the results of ac modulation measurements of cesium and rubidium ion desorption times from tungsten at various temperatures. The ac modulation technique can be used to determine other mean times involving particle-surface interactions and in general the effective time constants for the passage of ac signals.
Theoretical Determination of Domain Width of Simple-Honeycomb Domain Structures
Authors: Kozłowski G. , Ziętek W.
Published: April 2005

The simple-honeycomb remanent structure that can be produced under specific conditions in uniaxial ferromagnetic monocrystals is theoretically investigated by means of the phenomenological formalism. Particular attention is paid to the simplifying assumption made by some authors while calculating this structure, namely, the ratio of the diameter of those hexagonal rodlike domains to their mutual distance is said to be constant and, thus, independent of the crystal thickness in the magnetically favored direction. It is shown that this assumption is justified for rather large thicknesses, the lower limit being about 1 μm. Furthermore, the dependence of the domain width on the thickness of the crystal is theoretically studied and, since for large thicknesses the calculated widths are still smaller than the measured ones, the conclusion is drawn that it is the neglect of the cuneiform closure domains in the model which is substantially responsible for this discrepancy between theoretical and experimental results, rather than the assumption just discussed. Finally, the stability of the simple-honeycomb domain structure is examined, this being found to be stable for arbitrary thickness of the crystal.
Thermally Induced Strains in Evaporated Films
Authors: Vook R. W. , Witt F.
Published: April 2005

Evaporated films may have different thermal expansion coefficients from their substrates. When the temperature of such a combination is changed, thermal strains are introduced into the film. Calculations of the thermal strains and strain energies for the differently oriented grains in a polycrystalline sample were made. The theoretical results were checked by x-ray diffractometry, using thick gold and copper films bonded to glass substrates by means of thin chromium films. The calculations are useful in investigations of x-ray line shifts, elastic constants, adhesion, and relative grain growth in polycrystalline films formed on cold substrates and annealed.
``Thermoelectric Effect'' of Hot Carriers
Authors: Conwell E. M. , Zucker J.
Published: April 2005

A theory is developed for the voltage arising from a gradient in a high electric field, i.e., a field sufficient to change the average energy of the carriers, and applied to calculations for the warm-carrier region in a semiconductor. For a situation in which there is a region of constant field E next to a region, consisting of the same material, in which the field decreases to zero, it is found that, for E in the warm-electron range, the field-gradient voltage is proportional to E2. This dependence is found experimentally for both n and p germanium at room temperature. Because a region of inhomogeneous material at a contact also makes some contribution to the measured voltage, it is not possible to make a quantitative comparison between experiment and theory. The contribution of the contact is found to depend on the nature of the transition region between semiconductor and metal and, in the hot-electron region, upon the magnitude of the electric field.
Recombination in Gamma-Irradiated Silicon
Authors: Glaenzer Richard H. , Wolf Clarence J.
Published: April 2005

The lifetimes of excess carriers in phosphorus-doped, float-zoned silicon were measured before and after irradiation by cobalt-60 gamma rays. Recombination in the samples prior to irradiation was dominated by a donor-like recombination center located 0.13 eV above the valence band. After irradiation, two recombination centers were found in the samples: one located at Ec-0.17 eV and the other at Ec-0.40 eV. The center at Ec-0.17 eV can be identified with the oxygen-vacancy defect (Si-A center), but no positive identification of the Ec-0.40 eV center can be made. By assuming that the Ec-0.40 eV center is the phosphorus-vacancy complex, the hole capture cross section of the center was estimated as 9 × 10−14 cm2.
Thermally Activated Internal Friction in Aluminum
Authors: Hutchison T. S. , Rogers D. H. , Turkington R. R.
Published: April 2005

A series of maxima in the internal friction of aluminum at temperatures between 4.2° and 270°K are reported and analyzed. These maxima follow cold work and fast cooling of the specimen and occur on warm-up. The maxima are related to a mechanism of vacancy pinning of dislocations. Vacancies are indicated by the annealing characteristics of the phenomena. The vacancies in the model are supposedly produced by the cold work and are associated in strings or clusters. Extended dislocations move over saddle interaction energies and produce the relaxation maxima found at kilocycle frequencies. The megacycle attenuation measurements indicate the temperature at which the dislocation breaks from the pinned configuration.
ESR Study of Free-Radical Production in the Irradiation of Additive-Containing Polymethylmethacrylate
Authors: Atwater H. A.
Published: April 2005

The free-radical density produced in polymethylmethacrylate under x-ray and γ-ray irradiation has been measured as a function of the amount and kind of organic additive substances present in the polymer. The ratio of radical density produced in the pure polymer by a given radiation dose to that produced in polymers containing additives exhibits a strong dependence upon radiation dose, unlike the similarly defined ratio for the protection against radiation damage by polymer chain scission. The time rate of decay of free-radical density was also found to depend upon the additives present. The existence of a radiation-dependent free-radical annihilation process is postulated.
Force-Free Magnetic-Field Solution in Toroidal Coordinates
Authors: Buck G. Joseph
Published: April 2005

A method is presented for the solution of the force-free magnetic-field boundary-value problem in toroidal coordinates. An exact solution utilizing the Stokes' current function is given for the free space surrounding the toroid. The solution of the force-free equations within the current-carrying region of the toroid, however, requires the use of approximate methods. A suitable approximate method is developed which, also in accordance with physical considerations, exactly satisfies the requirement that the divergence of the current be zero. Galerkin's method is chosen for use in this approximation and use is made of the flexibility of this method to reduce the complexity of the approximation process. A sample calculation using this approximation method and the results of this calculation are described. This approximation method is found to give an accurate solution to the boundary-value problem with a minimum of effort. An equation describing the forces still present on the surface of the toroid is developed and the limitation imposed by this equation on the reduction of these forces in the boundary-value problem is noted.
Amorphous Phase in Palladium—Silicon Alloys
Authors: Duwez Pol , Willens R. H. , Crewdson R. C.
Published: April 2005

By rapid cooling from the melt, an amorphous phase has been obtained in palladium—silicon alloys containing 15 to 23 at.% Si. This phase is stable at room temperature and crystallization cannot be detected after one month at 250°C. With rates of heating greater than 20°C/min, rapid crystallization takes place at 400°C, with a heat release of approximately 1000 cal/mole. The electrical resistivity of an alloy containing 17 at.% Si at room temperature is 2.6 times that of the equilibrium alloy. The resistivity decreases linearly with decreasing temperature and is about 95% of the room-temperature value at 2°K. Various factors involved in the retention of amorphous phases in rapidly quenched liquid alloys are discussed.
Effect of Plastic Deformation on the Thermal Conductivity of Various Ionic Crystals
Authors: Taylor A. , Albers H. R. , Pohl R. O.
Published: April 2005

Drastic decreases in the thermal conductivity upon deformation similar to those reported by Sproull, Moss, and Weinstock have been found in NaCl, KCl, and NaF crystals. Unexpected differences in the frequency dependence of the phonon—defect relaxation times lead to an investigation of whether point defects, created during the deformation, might influence the phonon scattering. Studies of the recovery kinetics of the thermal conductivity paralleling those carried out on the mass density changes by Silverstone and Pratt on NaCl, and Vaughan et al. on KCl, seemed to exclude this. Experiments on bent LiF further supported the view of Sproull et al. that the thermal conductivity of deformed alkali halides is determined by coherent scattering of phonons off groups of dislocations.
Interaction of Microwaves with an Inhomogeneous and Anisotropic Plasma Column
Authors: Yeh C. , Rusch W. V. T.
Published: April 2005

The problem of the interaction of microwaves with a radially inhomogeneous plasma column confined by an impressed axial static magnetic field is treated analytically. Extensive numerical results for the backscattering cross sections are presented for various interesting ranges of the parameters involved. It is found that the often-used homogeneous model for interpretation of experimental data can sometimes lead to ambiguous results. This ambiguity arises because of the interdependence of the average plasma frequency, the gyrofrequency, and the inhomogeneity of the plasma density distribution. Further measurements are suggested to distinguish these effects.
Creep in Vacuum of MgO Single Crystals and the Electric Field Effect
Authors: Rothwell W. S. , Neiman A. S.
Published: April 2005

Experimental techniques are described and data are presented on bending creep of single-crystal MgO in vacuum from 800° to 1630°C. Evidence is discussed which supports the conclusion that creep near 1000°C is rate-controlled by cross-slip of screw dislocations with an activation energy of 1.5±0.25 eV. Creep above 1300°C takes place at a constant rate with an activation energy of 5.85±0.73 eV and a stress dependence exponent of 3. This creep is attributed to oxygen-ion diffusion-controlled climb of edge dislocations.

The effect of an electric field to give a transient acceleration of the creep rate is described. Experiments to define and characterize this effect are described and discussed.
Effect of Trivalent Manganese on the Crystal Chemistry of some Lithium Spinels
Authors: Rogers D. B. , Germann R. W. , Arnott R. J.
Published: April 2005

Crystallographic properties of the spinel systems Li0.5Ga2.5−xMnxO4 (0≤x≤0.7), Li0.5Fe2.5−xMnxO4 (0≤x≤0.5), and Li0.5Al2.5−xMnxO4 (0≤x≤0.5) have been investigated in order to determine the effects of trivalent manganese substitution on the crystal chemistry of the ordered spinel hosts. In each system relatively small concentrations of Mn3+ removed long-range ordering of lithium ions on the octahedral sites. This loss of order was accompanied by anomalies in the dependence of lattice parameters on composition. These observations can be qualitatively interpreted by assuming that Mn3+ ions tend to cluster in order to reduce the elastic energies associated with Jahn-Teller stabilization. These effects may provide indirect evidence for lattice imperfections such as have been invoked to account for square B-H hysteresis loops in ferrite materials containing Jahn-Teller ions.
Instantaneous Direct-Display System of Plasma Parameters by Means of Triple Probe
Authors: Chen Sin-Li , Sekiguchi T.
Published: April 2005

A new electrostatic probe method utilizing the triple probe is proposed in which no voltage or frequency sweep (or switching) is required. This feature enables us to determine the instantaneous values of the electron temperature (Te), as well as the electron density (ne), within a short time which is of the order of the intrinsic response time of the probe itself (⪝1μsec). Moreover, the system allows the direct display of the Te values as well as the semidirect display of the ne values on appropriate display units, thus permitting us to eliminate almost all procedures usually required for data processing. In view of the features mentioned, this system may be a useful diagnostic tool not only for stationary plasmas but also for rapidly varying time-dependent plasmas of various types.

This paper presents theoretical considerations for the instantaneous direct-display system using a symmetrical triple probe. Discussions are also presented for the estimation of errors caused by the variation of ion saturation current, for the application to magnetoplasmas, and for the time and spatial resolutions. Experimental confirmation was made through the measurements of stationary magneto- as well as non-magnetoplasmas. As an example of the application to time-dependent plasmas, the electron temperature waves accompanied by the moving striations in hydrogen discharge were observed.
Measurement of Metallic Film Densities by an Optical Technique
Authors: Wolter A. R.
Published: April 2005

Densities of metal films were measured using multiple beam interferometry in combination with an oscillating crystal microbalance. Film densities of Al, Au, Ag, Cr, and Cu were found to be independent of thickness within experimental accuracy of about 5% in the thickness range from 200 to 5000 Å for fixed deposition conditions. Measurements indicate that film densities were equal to bulk densities within measurement accuracy for Al, Au, Ag, and Cu for deposition at about 10−6 Torr. The film density of Cr was found to be strongly dependent on oxygen partial pressure above 10−6 Torr, decreasing sharply as the oxygen partial pressure increased. The effect of condensation coefficients of metal films on the optical measurements is discussed.
Pressure and Temperature Dependence of Creep in Potassium
Authors: Kohler C. R. , Ruoff A. L.
Published: April 2005

The activation energy and the activation volume for diffusion-controlled high-temperature creep were measured by the change-of-slope method. The values obtained were: 9.7±0.4 kcal/g-atom (or 0.42 eV) and 25.2±0.5 cc/g-atom (0.55 atomic volumes); this value of the activation volume is at 1 kbar. From this the value at atmospheric pressure can be estimated to be 26.0 cc/g-atom. It can be assumed that the activation energy and activation volume for self-diffusion are given closely by these creep values inasmuch as the strain rates used were small (ε̇∼10−7 sec−1) and the temperatures were relatively high (T∼0.9TM).
Dislocation Reactions in Silicon Web-Dendrite Crystals
Authors: O'Hara S. , Schwuttke G. H.
Published: April 2005

The origin and reactions of dislocations in silicon web-dendrite crystals are discussed. In particular, x-ray topographs are compared with etching results. Dislocations having [21̄1̄] axes or 〈110〉 type axes have been characterized. In the former case, normal edge and 20° dislocations are seen; however, an apparently new dislocation with a [21̄1̄] axis and [101] type or [110] type of Burgers vector has also been observed. Dislocations having a [11̄0] axis and [110] Burgers vector have been identified and associated with the Cottrell-Lomer reaction. The presence of multiple twin planes parallel to the growth direction of the web, accompanied by regions of very high dislocation density near the dendrites, increases the probability of certain dislocation reactions.
Plasma Microwave Interaction
Authors: Keržar B. , Weissglas P.
Published: April 2005

Transmission characteristics of a rectangular waveguide with a perpendicularly inserted mercury-vapor discharge tube, have been measured. The waveguide was excited in the TE01 mode and the plasma column was either perpendicular or parallel to the electric vector of the waveguide mode. In the first case the transmission spectrum contains the well-known Tonks-Dattner resonances and some additional unexplained small peaks. In the second case the transmission spectrum has only small peaks superimposed on a smooth curve. Noise emission spectra were also measured for both polarizations and showed the same characteristics as the absorption spectrum.

To explain these results, dispersion curves were measured for the symmetric, dipole, and quadrupole modes propagating on the plasma cylinder. In addition the dispersion curve for a new symmetric mode was measured. This mode is of the same nature as the fast dipole modes responsible for the subsidiary Tonks-Dattner resonances. By combining these experimental results it has proved possible to gain an understanding of how the various peaks in the transmission spectrum are caused by coupling to plasma waves. In particular, the small previously unexplained peaks are due to coupling to slow plasma waves as also has been proved by direct measurement of the slow waves leaking out through the holes in the waveguide.
Transmission Electron Microscope Study of Gallium Arsenide
Authors: Meieran Eugene S.
Published: April 2005

A technique is presented for preparing transmission electron microscope samples of gallium arsenide by a combination of chemical and electrolytic polishing. Both A(111) and B(1̄1̄1̄) as well as {100} surfaces of wafers obtained from two sources were examined by transmission electron microscopy after a variety of surface treatments. In general, B(1̄1̄1̄) and {100} surfaces were damaged more heavily than A(111) surfaces by mechanical polishing with 1-μ diamond. Aside from the surface damage the crystals were remarkably dislocation free, although precipitates of different kinds were observed. One type of precipitate clusters in the shape of tori, and can be revealed in the optical microscope by lightly electropolishing a mechanically polished wafer or by etching a polished wafer in the Sirtl etch. The other type of precipitate has contrast in the electron microscope similar to stacking faults, and may be due to an oxide of some type.
Dislocation Kink Chain Model Versus String Model
Authors: Alefeld Georg
Published: April 2005

The Peierls stress for dislocation motion causes characteristic nonlinearities of the micro-stress-strain law of dislocations. Contrary to the string model, the nonlinear stress-strain law of kinked dislocations can be the source of amplitude-dependent internal friction and modulus defect at amplitudes which are below or comparable to the breakaway stress from pinning points. Under the assumption that double-kink generation can be neglected, in terms of a bias stress experiment, the following points have been found to be the essential difference between the dislocation string model and the kink model: (1) The anelastic strain as measured by low-amplitude oscillations increases with bias stress for the string model, whereas it decreases for the kink model, due to the exhaustion of geometric kink motion. (2) The restoring force of kinked dislocations is one to three orders of magnitude more sensitive to bias stress than is the restoring force of dislocation strings. The conditions for measurable changes of the restoring force are, for the kink model, ε> (10−1 b/L) (sin φ+5kT/Gb2a), and for the string model ε> 10−1 πb/L (ε is the bias stress in units of shear modulus G, L is the line length, φ is the average angle against close-packed direction, b is the Burgers vector, a is the lattice constant, and T is the temperature).
Temperature Gradients in Semiconductor Alloying Technology
Authors: EerNisse E. P. , Thompson H. W.
Published: April 2005

Experiments have been conducted with Ge and Si to define the metallurgical effects of temperature gradients in the alloying technology. These effects are defined in terms of the electrical characteristics of alloyed diodes and transistors and in terms of the physical appearance of the p-n junction. The presence of temperature gradients during the dissolution phase of an alloy cycle results in near-planar junctions with identical electrical characteristics on the 111, 110, and 100 alloying surfaces if the melt is hotter than the solid, and results in nonplanar junctions on all alloying surfaces if the melt is cooler than the solid. The presence of temperature gradients during the crystal growth phase of an alloy cycle results in uniform regrowth layers if the melt is hotter than the solid, and results in nonuniform regrowth layers which contain gross crystal defects if the melt is cooler than the solid. The major electrical consequences are due to the gross crystal defects and take the form of soft reverse breakdown behavior and forward lnI-V characteristics that deviate from the single-slope model of p-n junction theory. It is shown that temperature gradients with the melt cooler than the solid should be avoided and that temperature gradients with the melt hotter than the solid can be used to advantage.
Switching of Thin Anisotropic Magnetic Films as a Function of the Rate and Amplitude of the Applied Field
Authors: Hatfield W. B.
Published: April 2005

The switching of thin anisotropic magnetic films by sinusoidal fields varying in frequency from 103 to 106 cps and having amplitudes up to 18 Oe has been studied and the results compared with both theory and previous pulse-field measurements. As the amplitude of the switching field is increased, it is concluded that the reversal mechanism changes from irreversible domain wall motion to nonuniform rotation of the magnetization, the point at which the transition occurs increasing with frequency. This conclusion is in disagreement with previously published work. A possible dependence of the switching coefficients on film thickness is also noted.
Dilatational Wave Velocities and Dynamic Elastic Moduli of Ni-Mn Alloys
Authors: Wazzan Ahmed Rassem , King M. S. , Ahmediah A. A.
Published: April 2005

Dilatational wave velocities in Ni-Mn alloys are measured at 25°C in the composition range 0% to 80% manganese using ultrasonic pulse techniques. Using a value of ⅓ for Poisson's ratio in the alloys, the observed values for the velocities are used to compute the corresponding values of the dynamic elastic moduli E. The dilatational wave velocities, ranging from 5638 in nickel to 3792 m/sec in the alloy with 80% Mn, and the correspondlng elastic moduli, ranging from 19350 to 7570 kg/mm2, are found, almost linearly, to decrease with increasing manganese content over the composition range 0% to 40% Mn; to increase over the range 40% to 50% Mn; and then to decrease again over the range 50% to 80% Mn. The increase in the elastic modulus with % Mn over the range 40% to 50% Mn is associated with the formation of the highly ordered NiMn(δ) phase with a bcc crystal structure. The variation of V and E with % Mn in the range of 60% to 80% Mn is found to be an extension of their variation in the range 0% to 40% Mn. This variation where the Young modulus of nickel decreases at an average rate of 125 kg/mm2 per atomic percent manganese added, is characteristic of the solid solution γ phase. At the tests' temperature, 25°C, the alloys with up to 25% Mn are in the ferromagnetic state whereas the alloys over the composition range 25% to 80% Mn are in the paramagnetic state.
Mechanical Relaxation of a Point Defect in Magnesium Oxide
Authors: Southgate P. D.
Published: April 2005

A center has been observed in MgO which has a [100] symmetry and gives rise to mechanical relaxation with associated activation energy of 0.64 eV. The pre-exponential frequency factor is 1.8×1011 sec−1, an anomalously low value which, it is suggested, indicates that the defect reorientation involves a primarily electronic transition. The center is stable only at high temperatures, decaying to a lower thermal equilibrium value below about 850°C. No spin resonance, dielectric loss, or optical absorption associated with the center has been observed, and studies of the effects of various treatments have not allowed the defect to be identified.
Deformation of and Stress in Epitaxial Silicon Films on Single-Crystal Sapphire
Authors: Dumin D. J.
Published: April 2005

The deformation of epitaxial silicon films grown on single-crystal sapphire has been measured. The range of silicon thicknesses was between 1 and 46 μ and the range of sapphire thicknesses was between 127 μ (0.005 in.) and 508 μ (0.020 in.). The deformation of the films was found to be proportional to silicon film thickness and decreased with increasing sapphire thickness. For sapphire disks of 0.95 cm (⅜ in.) diameter and 250 μ (0.010 in.) thickness the proportionality constant was unity. The stresses in the deformed silicon films have been estimated on the basis of linear beam theory and were of the order of 109 to 1010 dyn/cm2. The silicon films were under compression and the sapphire was under tension. No physical damage to the films was observed under these stresses, but these stresses should be sufficient to affect the electrical properties of the films.
Silicon Oxidation in an Oxygen Plasma Excited by Microwaves
Authors: Ligenza J. R.
Published: April 2005

A preliminary study of the oxidation of silicon by a moderate density oxygen gas plasma has provided two methods for oxidizing silicon rapidly at low temperatures. The oxidation process has unique characteristics which allow for masking against the growth of the film. A probable mechanism for the oxidation process is presented.
New X-Ray Diffraction Microscopy Technique for the Study of Imperfections in Semiconductor Crystals
Authors: Schwuttke G. H.
Published: April 2005

A novel x-ray technique and its application to semiconductor problems is described. The technique is capable of recording large-area transmission topographs of crystal slices as processed in modern semiconductor device technology. The technique is nondestructive and, therefore, crystal slices can be examined after each processing step. This technique and some of the results obtained are discussed, such as x-ray topographs of diffused transistor structures, recorded in the presence of elastic and/or frozen-in lattice deformations.
Role of Traps in a Steady-State Space Charge
Authors: Gold Louis
Published: April 2005

Allowance for traps in certain space-charge environments produces changes in the mathematical formalism which make it difficult to determine spatial variations in potential and the negative-positive charge distribution. The trap-free model for the blocking electrode can be extended into this realm by appropriate accommodation of the equations of continuity for specified kinetics of the trap system. The tendency of traps seems to be a moderation of the spatial fall-off of potential with more gradual build-up and decay of the charge densities. The nonlinear Poisson equation has been solved analytically by the development of powerful series methods, demonstrating that machine integration can be avoided.
Direct Charge Transfer by X Irradiation in the System CaF2:Eu, Tm
Authors: Welber Benjamin
Published: April 2005

Starting with CaF2 containing Eu2+ and Tm3+ ions, we have employed optical techniques to observe the decrease in valence of the Tm ion under x irradiation. We find that the number of Tm2+ ions produced corresponds closely to the number of Eu2+ ions which disappear, and we suggest that the underlying mechanism is a direct transfer of an electron between the two types of ions.
Domain Wall Velocities and the Surface Layer in BaTiO3
Authors: Callaby D. R.
Published: April 2005

The velocity of 180° domain walls in orthorhombic BaTiO3 has been measured over a range of applied fields below 1 kV/cm in dc and in pulsed field conditions. From these measurements it was seen that the domain wall behavior was qualitatively very similar to that reported by Miller and Savage for the tetragonal case. The main difference was the more pronounced effect of the surface layer on the velocities of the walls in the orthorhombic crystals. Accordingly, a number of additional experiments were performed which gave more information on the nature of this surface layer. As a result a completely new model of the surface layer is proposed in which the activation field δL in the layer is much higher than the activation field δB in the bulk of the crystal. The predictions from this model are in satisfactory agreement both with the results reported here for orthorhombic BaTiO3 and with all the evidence available from other sources of the behavior of tetragonal BaTiO3. Comparison is made with previously accepted models and it is shown that these fail to explain many of the experimental results both of the orthorhombic and of the tetragonal cases.
Zener Relaxation in NaCl:KCl
Authors: Laibowitz R. B. , Dreyfus R. W.
Published: April 2005

In metallic alloys the stress-induced reorientation of solute pairs produces an anelastic relaxation called the Zener effect. To determine whether or not this relaxation is also observable in a nonmetallic solid solution, internal friction of single crystals of NaCl plus (1.3% to 1.7%) KCl is measured at 4 to 10 kc/sec. A maximum in the damping occurs near 400°C for nominally pure NaCl:KCl and near 300°C for NaCl:KCl crystals with CaCl2 added to enhance the cation vacancy concentration. This behavior indicates that the Zener relaxation is present in NaCl:KCl. Diffusion constants calculated from this Zener relaxation agree well with the results of radioisotope diffusion experiments.
Shock-Induced Luminescence in Quartz
Authors: Brooks William P.
Published: April 2005

Crystalline quartz shocked parallel to the X axis was luminescent at pressures greater than 30 and 40 kbar in the −X and +X orientations, respectively. Fused quartz and crystalline quartz shocked parallel to the Y and Z axes exhibited practically no luminescence at pressures below 120 kbar. From consideration of (1) the almost instantaneous appearance of the light patterns, (2) a comparison of the electrical results of Neilson, Benedick, and Graham with the luminescence, and (3) sodium present in the quartz, it is suggested that luminescence in quartz shocked parallel to the X axis is caused by the combined effects of piezoelectric voltage and shock compression. The light observed in crystalline quartz shocked parallel to the Y and Z axes and in fused quartz is attributed to triboluminescence.
Detection of Nonlinear Optical Sum Spectra in ADP using Incoherent Light
Authors: McMahon D. H. , Franklin A. R.
Published: April 2005

Using a xenon arc lamp source with a spectral distribution extending from 10 000 to 5000 Å, we have found it possible to generate a detectable nonlinear sum spectrum in ADP over the range from 5000 to 2700 Å. This sum signal distribution has a spectrometer-limited resolution of 20 Å which is sufficiently good to resolve line structure and to permit a comparison of this structure with the xenon lamp line spectrum. It is found that the greater part of the sum signal consists of a structureless background which is attributed to nonlinear mixing involving the xenon blackbody continuuum spectrum. A computer program was used to calculate the expected sum signal distribution assuming that the nonlinear polarization constant is independent of frequency. The calculated spectrum agrees qualitatively with the sum signal spectrum obtained experimentally.
Etching of Dislocations on the Low-Index Faces of GaAs
Authors: Abrahams M. S. , Buiocchi C. J.
Published: April 2005

A new etchant for GaAs consisting of CrO3, HF, AgNO3, and H2O is described which selectively attacks dislocations on the following planes: Ga {111}, As {111}, {100}, and {110}. Dislocations normal, inclined, and parallel to the plane of observation are revealed. The etching figures were correlated with dislocations by equating (a) the etch pits produced on {111} surfaces with those produced by a known dislocation etchant, (b) the {111} etch pits with the linear structure appearing on {100}, and (c) the pits on two matched {110} cleavage planes. Supporting evidence obtained from plastic indentation experiments on {111} and {100} is also presented. It is observed that long, straight dislocations tend to lie in 〈110〉 and 〈112〉 directions. It was established by reverse bending experiments that the etchant produces pits only at As or β dislocations, if no impurity segregation has occurred. If decoration of the dislocations has occurred, as in Bridgman-grown GaAs, pits are produced at both α (Ga) and β dislocations.

The relative etching rates for the {100}, Ga {111}, {110}, and As {111} faces are 1.0, 0.71, 0.69, and 0.50, respectively.

Stacking faults on {100} are also revealed by the etchant on epitaxial films. A second etchant is reported which reveals stacking faults on the As {111} faces of GaAs. This etchant is the same as the dislocation etchant but with the CrO3 absent.
X-Ray Lattice Constants of Crystals by a Rotating-Camera Method: Al, Ar, Au, CaF2, Cu, Ge, Ne, Si
Authors: Batchelder D. N. , Simmons R. O.
Published: April 2005

A rotating x-ray camera is described which yields lattice constants of single crystals with a possible error of 0.00007 kX. Measurements of expansion may be made with a precision of 0.00002 kX. The design of the camera permits accurate specimen alignment at any specimen temperature and requires that few corrections be made. Lattice constants of pure Al, Au, CaF2, Cu, Ge, and Si at 25°C and of pure Ar and Ne at 4.3°K are reported and critically compared with values from the literature.
Growth and Properties of Yttrium Iron Garnet Single-Crystal Films
Authors: Linares R. C. , McGraw R. B. , Schroeder J. B.
Published: April 2005

Techniques were developed to grow single-crystal films of a magnetic garnet (yttrium iron garnet) on a nonmagnetic garnet substrate. Y3Al5O12, Y3Ga5O12, and Gd3Ga5O12 substrates were investigated. Single-crystal YIG films were grown by flux and vapor deposition. The perfection, optical transmission, surface characteristics, and thickness of these films were investigated.
Angular Distribution of Sublimed and Sputtered Particles from Ag Single Crystals
Authors: Cooper C. Burleigh , Comas James
Published: April 2005

When silver (100) and (110) single crystals were sputtered by 160–200-eV argon ions from an arc the well-known spot patterns appeared when the sputtered particles were collected as a thin film on glass plates. To determine whether similar spot patterns would result from sublimation, the same crystals were sublimed at temperatures between 642° and 815°C under high-vacuum conditions. Optical transmission densitometer measurements on the resulting thin films indicated that during sublimation the emission was approximately cosine, and no evidence of preferential ejection of silver particles during sublimation was detected. It is estimated that if preferential ejection is taking place along the close-packed directions of the crystal during sublimation in this temperature range, this emission produced a thickness change of the collected silver films such that the transmitted light intensity varied from a cosinelike curve by less than 5% at those angles.
Dislocation Arrangements in Zinc Tungstate
Authors: O'Hara S. , McManus G. M. , Roessler B.
Published: April 2005

Dislocations in low dislocation density (∼102 cm−2) single crystals of ZnWO4 have been analyzed by the application of standard etching techniques and by Borrmann and Berg-Barrett x-ray diffraction techniques. The majority of dislocations lying on the (010) slip planes were found to have [100] Burgers vectors, while the remainder had [001] Burgers vectors. Dislocations lying on the (100) plane had predominantly [001] Burgers vectors; dislocations with [010] Burgers vectors were present, but uncommon. In Borrmann photographs dislocations which were close to the exit surface of the crystal gave images of increased, rather than decreased, intensity. The effect of the oxygen atom positions on the intensities of the anomalously transmitted x-ray beams was shown to be significant in ZnWO4. Also, impurity segregation, which was revealed in both transmission optical and in x-ray photographs, indicates that facetting occurred on a convex growth interface.
Measurement of Nonlinear Polarization of KTaO3 using Schottky Diodes
Authors: Kahng D. , Wemple S. H.
Published: April 2005

Capacitance vs bias voltage data are presented for Au–KTaO3 surface barrier Schottky diodes. Substantial deviations from the normal Schottky capacitance relationship have been observed and attributed to a field-dependent dielectric constant in the depletion layer. From the capacitance data obtained at room temperature, ε vs E and P vs E curves have been calculated for KTaO3 and found to be consistent with previous measurements made using conventional techniques at 4.2°K.
Cold Electron Sources for Mass Spectrometric Applications
Authors: Testerman M. K. , Raible R. W. , Gilliland B. E. , Williams J. R. , Grimes G. B.
Published: April 2005

Cold electron sources have been studied with particular emphasis on mass spectrometric application. In these sources a relatively weak current from a primary emitter was amplified by an electron multiplier to provide sufficient electron current to ionize neutral gas molecules. The final designs of the cold sources use tantalum photocathodes powered by simulated sunlight as primary electron sources. The sources are highly efficient, consume negligible power, have minimal outgassing and gettering effects, and exhibit considerably less short-term emission fluctuations than a temperature-limited thermionic emitter. These devices would be well suited to calibration work and space flight instrumentation.
A Quantitative Anodic Replica for Electron Metallographic Studies
Authors: Beck A. F.
Published: April 2005

The electron opacity of anodic films formed on aluminum—copper alloys in an alkaline electrolyte under well controlled conditions is a function of the copper content of the alloys. This relation permits the development of a quantitative electron optical replica for application in revealing solute distribution and for measuring solute concentration. These replicas are extremely sensitive to small variations in copper concentrations in solid solution on a finer scale than can be defined by existing electron optical methods. Application of this replica technique to a study of aged aluminum—copper alloys has revealed some new aspects of the decomposition process.
Electron-Stream Diode Instabilities with Elastic Collisions
Authors: Frey Jeffrey , Birdsall Charles K.
Published: April 2005

Instabilities can be induced in parallel-plane (diode) configurations when a very high current is passed through the diode, even if this current is neutralized by ions. This work extends Pierce's original calculation of the critical current for instability to find the growth rate for a wide input—current range, and then goes on to include collisions of the injected stream with background neutrals and allow for mobile neutralizing particles. Collisions damp the instability, increasing the value of input current at which onset of instability will occur; if the collision frequency ν is such that ωp2L/νv0<4π, approximately, then there is no time growth. Allowing the background ions to be mobile also eliminates this type of instability. The results without collisions compare favorably with some experiments involving essentially collisionless diodes; those with collisions included do not agree with some experiments involving collision-dominated triode lasers.
The Transmission of Hydrogen through Palladium by Electrolysis
Authors: Wahlin H. B. , Naumann Virgil O.
Published: April 2005

Whenever a metal is made, the cathode in a dilute sulfuric acid bath the transmission of hydrogen may be observed by means of its reaction with oxygen of the air. A more detailed study of the transmission through palladium shows that the area of the surface at which the hydrogen leaves is the principal controlling factor. Possible applications to hydrogenation studies are discussed.
Ultrasonic-Wave Study of Swollen Buna-N Rubber
Authors: Nolle A. W. , Mifsud J. F.
Published: April 2005

The velocity and attenuation of ultrasonic waves are measured as a function of temperature in specimens of a Buna-N vulcanizate swollen to various degrees with methyl ethyl ketone. The frequencies are 2, 5, and 10 megacycles. The experimental method consists of determining the insertion loss and the time delay due to insertion of a flat sample in the liquid acoustic medium of a pulse-reflection apparatus; an improved technique of observation, in which phase delay as well as envelope delay is examined, leads to more precise time data than previous applications of the method. As solvent content of the specimen increases, the position of the maximum of attenuation with respect to temperature moves to lower temperatures, and the height of the attenuation peak is reduced. It is shown that the height of the attenuation peak, when corrections are made for temperature effects according to the mechanisms of rubberlike elasticity, is proportional to the mass of polymer per unit volume in the swollen specimen; moreover, the temperature of maximum attenuation is a linear function of the ratio, for the swollen specimen, of mass of solvent to mass of polymer. The latter finding indicates, if the concept of energy of activation is applicable, that the reduction of activation energy is proportional to the number of solvent molecules associated with each polymeric ``chain segment.'' The paper contains auxiliary data on dimensional and volumetric aspects of swelling and swelling rate.
Theory of the Single-Wire Transmission Line
Authors: Roberts T. E.
Published: April 2005

Equations are derived for the current induced in an infinitely long, thin, straight wire of nonzero surface impedance when the wire is connected to a flanged coaxial line. Also, radiation field patterns are computed and the input conductance determined. It is found that the current (and likewise the input conductance) can be separated into two components, one of which is a propagating or modal current. Graphs are presented from which the efficiency of excitation of the propagating current can be computed.

A second structure consisting of a single wire between perfectly conducting parallel plates is solved as a boundary-value problem. The solution is used in the discussion of the physical behavior of a finite single-wire transmission line. In particular it is found that the usual transmission line concepts are valid under certain restricting conditions.
The Statistics of Liquid Spray and Dust Electrification by the Hopper and Laby Method
Authors: Dodd Edward E.
Published: April 2005

The electric charges created upon individual microscopic particles of an aerosol during its generation have been determined by the Hopper and Laby oil drop method. In the spraying of nonconducting liquids, the charges produced upon droplets in the diameter range 2–50 microns are found to follow a normal distribution with the average charge zero and the mean square charge proportional to droplet volume. This result favors the electrification mechanism of statistical fluctuation of electrolytic ion concentration among the droplets rather than the more prominent Lenard mechanism. The charge distribution among clean mercury droplets in the diameter range 1–6 microns sprayed from a glass sprayer is asymmetric because of contact effects at the mercury-glass interface: the average droplet charge is positive, relatively large, and increases with droplet diameter. The dependence of dispersive dust charging upon particle surface roughness is illustrated by observations made with relatively smooth microscopic glass spheres and compared with data for rough crushed quartz particles.
Tracer Diffusion in the Ground in Radioactive Leak Location
Authors: Gemant Andrew
Published: April 2005

The diffusion in the ground of a radioactive tracer gas, used for locating leaks in buried pipes, has been calculated, and the results are presented in the form of graphs. It is shown how the information can be used to obtain the amount of radioactivity needed in a test for both beta-emitters (C-14 in carbon monoxide) and gamma-emitters (Br-82 in methyl bromide).
Attenuation of Gamma Rays. I. Transmission Values for Finite Slabs of Lead, Iron, and the Compton Scatterer
Authors: Peebles Glenn H.
Published: April 2005

An approximate integral recursion formula is developed which gives a relation between the probability that a photon will be transmitted through a slab of finite thickness with exactly k+1 collisions and the probability that it will be transmitted with exactly k collisions, where the latter probability is known for suitable ranges of slab thickness, of incident energy, and of incident angle. A similar formula also exists for the expected energy transmitted. The two recursion formulas have been used to calculate the transmissions with one, two, and three scatterings for photons incident on slabs of lead and of iron, and from these calculated transmissions the ``build-up'' factors have been estimated. The build-up factor for normally incident photons of 1 to 20 mc2 are given for lead slabs and for iron slabs having a thickness of 0 to 20 mfp.

A second method, which considers the transmission through a thick slab as a succession of transmissions through thin slabs, is used to check the estimates of the build-up factor obtained by the first method. This second method provides additional information in the form of the distributions of the transmitted photons.

Finally, some transmission and reflection values for thin slabs of the Compton scatterer are presented along with some results for air which are obtained by the second (thin-slab) method.