By Topic

Journal of Applied Physics

Issue 1 • Date Jan 1973

Filter Results

Displaying Results 1 - 25 of 108
  • Issue Table of Contents

    Page(s): toc1
    Save to Project icon | PDF file iconPDF (172 KB)  
    Freely Available from IEEE
  • High‐resolution spectroscopy for optical probing of continuously generated surface acoustic waves

    Page(s): 1 - 4
    Save to Project icon | PDF file iconPDF (284 KB)  

    Under conditions of continuous acoustic generation, light scattered from oppositely directed surface acoustic waves on y‐cut z‐propagating lithium niobate was frequency analyzed with a high‐resolution Fabry‐Perot interferometer. The following parameters were measured at 105 MHz: acoustic power standing‐wave ratio, reflection coefficient for both sending and receiving transducers, low‐power acoustic damping coefficients, surface wave propagation velocity, and nonlinear harmonic growth. We note that the method used has an advantage over other methods since it is to a large extent independent of the optical quality of the propagation surface. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Velocity measurements of microwave ultrasonic waves in quartz

    Page(s): 5 - 6
    Save to Project icon | PDF file iconPDF (155 KB)  

    The velocities of microwave ultrasonic waves at 9.2 GHz have been measured using pulse‐echo techniques in X‐cut and Z‐cut quartz rods. In the X‐cut quartz, the longitudinal mode velocity was (5.71±0.05)×105 cm/sec and the transverse mode velocities were (5.20±0.05)×105 cm/sec. The longitudinal velocity for the Z‐cut quartz was (6.33±0.03)×105 cm/sec. In contrast with the measurements of Ogawa and Sakamoto these results agree with the low—frequency velocities reported by McSkimin [J. Acoust. Soc. Am. 34, 1271 (1962)]. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Concentrated force in a cubic anisotropic solid: a single integral solution

    Page(s): 7 - 9
    Save to Project icon | PDF file iconPDF (194 KB)  

    A single integral solution is presented for displacements arising from a concentrated force in an infinite medium with cubic elastic anisotropy. The integrand is an explicit algebraic expression of the three elastic constants and the spherical coordinates of the point at which the displacements are required. The integral gives the displacement components referred to the cubic axes. Although the concentrated force is along a cubic axis, a force in an arbitrary direction can be constructed by the superposition of the solutions for its components along the axes. Applications are suggested that use distributions of point forces to model defects in cubic crystals. Elastic displacement fields are presented for crystals of Na, Cu, Rb I, Nb and W. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Microwave ultrasonic attenuation in topaz, beryl, and tourmaline

    Page(s): 10 - 13
    Save to Project icon | PDF file iconPDF (271 KB)  

    Microwave ultrasonic attentuation measurements have been made on single crystals of topaz, beryl, and tourmaline, and all are found to exhibit very low losses. The room‐temperature attenuation coefficients are consistent with the Akhiezer mechanism which arises from interactions between the ultrasonic wave and the thermal‐phonon assembly. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Low‐temperature epitaxy of Ge films by sputter deposition

    Page(s): 14 - 19
    Save to Project icon | PDF file iconPDF (580 KB)  

    The crystallographic structure and orientation of Ge films formed by sputter deposition onto Ge (111) substrates have been investigated as a function of various deposition parameters. Important parameters affecting the film structure include growth rate, substrate temperature, substrate‐surface cleanliness, and sputtering‐gas purity. The structure of the sputter‐deposited films was examined by HEED, while the substrate surface was characterized by HEED, LEED, and Auger electron spectroscopy. Results show that epitaxy of Ge can be obtained by sputter deposition at substrate temperatures as low as 100 °C, provided the deposition conditions are properly optimized. A plot of the film structure as a function of substrate temperature and growth rate defines the three regions of crystallinity (amorphous, polycrystalline, and single crystalline), indicating the existence of a triple point. The amorphous‐polycrystalline and epitaxial transitions occur at temperatures considerably lower than those reported by previous investigations. Thermal regeneration of the substrate surface results in a considerable reduction of the transition temperatures. Oxygen in the sputtering atmosphere plays a significant role in determining the epitaxial temperature. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Anisotropy of radiation damage and dislocation damping in Cu

    Page(s): 20 - 24
    Save to Project icon | PDF file iconPDF (386 KB)  

    Cu single-crystal cubes have been γ irradiated in the [001] and [11¯0] directions, and the ultrasonic attenuation due to dislocation damping has been determined in the [110] direction after the various irradiation treatments. Fricke dosimetry indicates that about 10% less secondary electron energy exits the crystal in the [11¯0] irradiation than in the [001] irradiation. The fact that more energy is absorbed in the [11¯0] irradiation is consistent with the dislocation damping studies which indicate that more dislocation-pinning point defects are created in this case. The damping data obey the Granato-Lücke damping theory, and quantitative predictions as to the dislocation loop length and number of pinners created during irradiation are made on the basis of the theory. The anisotropy in radiation damage is consistent with theoretical predictions of anisotropy of replacement energy and focusing energy in Cu. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Radiation blistering of polycrystalline niobium by helium‐ion implantation

    Page(s): 25 - 31
    Save to Project icon | PDF file iconPDF (1195 KB)  

    The radiation blistering of polycrystalline niobium surfaces at room temperature has been investigated for different doses of helium ions implanted at 0.5 MeV and for different amounts of initial defect structure in the samples. The cold‐worked samples show large blisters (up to 500 μm in diameter), many of which are ruptured. In samples annealed before irradiation, the blistering at low doses (0.1 C/cm2) was lower than in the cold‐worked sample, but at a higher dose (1.0 C/cm2) the blistering was even greater. The observation of interconnecting bubbles offers a possible explanation for the formation of such large blisters at low temperatures. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Quantitative analysis of damping and modulus effects in copper crystals using the ``vibrating‐string'' dislocation model

    Page(s): 32 - 47
    Save to Project icon | PDF file iconPDF (1533 KB)  

    Internal friction and modulus measurements were made between 13 and 38 kHz as a function of temperature on several copper crystals into which a low density (∼ 105–106 cm-2) of dislocations had been introduced by deformation in compression. The dislocation contributions to damping and modulus defect were determined by comparison with duplicate measurements made after the dislocations had been immobilized by irradiation. Dislocation densities were evaluated by etch‐pit counting, and as a result enough information was obtained to determine absolute values for the loop length and drag coefficient in the vibrating‐string (Koehler/Granato‐Lücke) model of dislocation damping. The loop length was found to have appreciable temperature dependence and the drag coefficient was found to be higher by a factor of ∼ 15–∼65 than values obtained for copper by MHz damping and dislocation velocity measurements. Similar results were obtained in several samples and it is noted that the measured damping and modulus values are not greatly different from those obtained by other experiments. It thus appears that for the kHz frequency range in pure copper crystals basic elements of the string model require revision. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Ultrasonic reflection of a bounded beam at Rayleigh and critical angles for a plane liquid‐solid interface

    Page(s): 48 - 55
    Save to Project icon | PDF file iconPDF (923 KB)  

    Limited beams of low MHz ultrasound are directed at plane interfaces between water and different solids. Reradiated energy is observed by means of schlieren visualization outside the region predicted by Schoch for incidence at the Rayleigh angle. Some of the solids have properties that would cause prediction of a beam displacement many times that for aluminum. Previous thoery would predict the reflected beam to emerge totally separated from the incident beam for several of the materials used, but no such separation is observed. It is concluded that the reradiated field is composed of specular reflection and Rayleigh‐wave radiation at and near the Rayleigh angle. These two radiations are out of phase at low MHz frequencies, and where they coexist and are of equal amplitude, which occurs within the specular region, a null strip occurs. This strip is sharply defined at exactly the Rayleigh angle. Surface waves (sometimes called pseudosurface waves) are also generated at the longitudinal and shear critical angles. These are also shown to radiate into the fluid but are generated to a much lesser degree and are difficult to demonstrate by schlieren visualization. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Lamb‐wave delay lines with interdigital electrodes

    Page(s): 56 - 62
    Save to Project icon | PDF file iconPDF (540 KB)  

    Propagation characteristics and the equivalent circuit model of delay lines using Lamb waves excited by interdigital transducers on unpolarized PZT ceramic plates have been studied. Dispersive characteristics of phase velocities of Lamb waves excited by the interdigital transducers are in good agreement with the numerical solution from the dispersive equation of phase velocities developed by Worlton. When the product of frequency times plate thickness is below 1.3×106 Hz mm, the zeroth symmetric Lamb wave is strongly excited. The Lamb waves are excited most effectively when the half‐period of interdigital electrode is equal to the wavelength of the Lamb wave. Also, the values of the attenuation coefficient and the reflection coefficient from the edge of the specimen are given. It is shown that the generation of symmetrical‐mode Lamb waves by our transducer is equivalently represented by a thickness mode transducer of half‐wavelength inserted perpendicular to the plate. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Elastic energies of disclinations in hexagonal crystals

    Page(s): 63 - 65
    Save to Project icon | PDF file iconPDF (193 KB)  

    The aim of this paper is to investigate the elastic fields of a twist disclination loop and a wedge disclination line in hexagonal crystals. The plane of the twist disclination loop and the wedge disclination line are assumed to be parallel and normal to the basal planes, respectively. Closed‐form solutions have been obtained for disclination stress fields and elastic energies. It is noted that the elastic field of twist loops in thin hexagonal crystals and nonhomogeneous systems can be found by the method of images. Energy values for several common hexagonal crystals are calculated. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Measurement of high‐temperature thermal conductivity of Lucalox (Al2O3) using a heat pipe technique

    Page(s): 66 - 71
    Save to Project icon | PDF file iconPDF (497 KB)  

    The thermal conductivity of Lucalox, a high‐purity form of aluminum oxide, has been measured over the temperature range 870–1400°C. The technique employed is a novel one using a lithium‐filled heat pipe in series with a gas gap variable heat conductance unit as a heat source. The procedure enables one to measure heat flux through the sample directly. The measurements indicate that the thermal conductivity of high‐purity aluminum oxide has a minimum value of about 0.05 W/cm°C at 950°C and increases with higher temperatures to values in the range of 0.3 W/cm°C at 1400°C. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Ultraviolet radiation from electrical discharges in water

    Page(s): 72 - 75
    Save to Project icon | PDF file iconPDF (387 KB)  

    Ultraviolet radiation is one of the principal forms of energy which is dissipated from an electrical discharge in water. For a stored capacitor energy of 1500 J, up to 28% or 420 J has been converted to uv radiation with a peak radiant power of 200 MW. Of the energy transferred to the plasma, 36% was converted to radiation. The efficiency of radiation was maximum for a length of the discharge channel of approximately 3.8 cm. Scaling rules are given. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Finite‐difference simulation of an electrical discharge in water

    Page(s): 76 - 81
    Save to Project icon | PDF file iconPDF (446 KB)  

    The growth of an electrical discharge channel in water has been simulated by a finite‐difference solution of the partial differential equations of motion along with the descriptive equations of the medium. The computation is based upon a set of parameters which describe experimentally controllable conditions. Close agreement is obtained between simulations and experiments by adjusting arbitrary parameters included in the description of the medium. However, the simulation is relatively insensitive to these parameters. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Investigation of the gun aspects of a rotating plasma source

    Page(s): 82 - 90
    Save to Project icon | PDF file iconPDF (802 KB)  

    A crossed field or rotating plasma gun is investigated to determine detailed processes taking place during the ionization and acceleration phases. Measurements suggest that the gun breaks down via a spoke which subsequently rotates at the limiting velocity. Internal shorting occurs subsequent to break down and limits the usefulness of the source. Methods of reducing the effects of this shorting are presented as are some measurements of the properties of the plasma after it leaves the gun region. These suggest that about 1019 particles can be accelerated to energies of several hundred eV. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Scattering of microwaves by a stratified overdense plasma at high collision frequencies

    Page(s): 91 - 95
    Save to Project icon | PDF file iconPDF (325 KB)  

    A study has been conducted, for several electron‐density distributions, of the reflection of electromagnetic waves from stratified overdense plasmas in which the rate of collision frequency to incident frequency is large and the transmission negligible. With positive power profiles where the density changes slowly near the turning point, the reflection coefficient is small, whereas for inverse power profiles where the density gradient is large near the turning point, the reflection is large. In the case of a symmetric type of profile where the maximum density is finite, the results are dependent upon profile type. In an inverse profile type, the reflection is fairly sensitive to maximum density, decreasing with it. With a Gaussian distribution, reflection increases slowly with maximum density, whereas for a sech2 model, the reflection is, for the most part, independent of this parameter. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Photoelectric spectral response of certain solids

    Page(s): 96 - 99
    Save to Project icon | PDF file iconPDF (317 KB)  

    Data taken from the literature on a variety of photoelectric effects are analyzed considering that the maximum photoresponse occurs at the wavelength at which the absorptance of the volume element responsible for the photoeffect is a maximum. The spectral response of certain photosensitive systems is shown to parallel the absorption of a thin volume element next to the rear surface. The thickness of surface recombination layers for cadmium sulfide is estimated from calculations involving the transmittance of the sample at the wavelength at which the maximum photoresponse occurs and the thickness of the sample. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Experimental investigation of the transient formation of a microwave‐generated ionized sheath in air

    Page(s): 100 - 105
    Save to Project icon | PDF file iconPDF (442 KB)  

    Microwave and photometric techniques are used to study the temporal and spatial behavior of a transient microwave‐generated air plasma sheath in a coaxial transmission line. In particular, breakdown times, stabilization times, and thickness of the ionized sheath are investigated at different pressures and generating signal amplitudes. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Electrical explosion of tungsten wires in a vacuum

    Page(s): 106 - 112
    Save to Project icon | PDF file iconPDF (881 KB)  

    The present work demonstrates the disintegration of thin electrically exploding tungsten wires in a vacuum. The drawn tungsten wires split into tiny fibers in a time close to that at which the wire reaches its melting point. Similar results were obtained for wires exploded at low pressures and at atmospheric pressure. The results show, within the limits of the experimental accuracy, that, when the wire reaches its melting point, dips are observed on the current derivative and the voltage oscillograms and x rays are produced. The results support the suggestion that the production of hard x rays from drawn thin exploding tungsten wires is due to the splitting of the wire, which has a fiberlike crystalline structure. Moreover the oscillograms of the first current pulse show that for thin wires the electrical conduction up to melting point is due only to the solid wire material and that the influence of the ambient pressure on the crest value of the first current pulse for wires exploded at the same condenser‐bank voltage is almost negligible. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Production of hot plasmas of solid‐state density by ultrashort laser pulses

    Page(s): 113 - 124
    Save to Project icon | PDF file iconPDF (1119 KB)  

    Ultrashort laser pulses emitted by a neodymium glass laser system were focused on the surface of solid targets situated in a high‐vacuum environment. The laser pulse duration as measured by the two‐photon fluorescence technique was less than 10-11 sec. Pulse energies up to 3 J were obtained corresponding to a maximum energy release of 3×104 J cm-2 in the focal area. The plasmas produced from targets of solid deuterium, carbon, and thin foils of Mylar were investigated by x‐ray measurements, time‐of‐flight measurements using charge collecting probes, and, in the case of deuterium, by neutron counting measurements. Only 10% of the incident light energy was found to be reflected from the targets. Electron temperatures of 500 and 200 eV were measured for deuterium and carbon plasmas, respectively. The experimental results are found to be consistent with the predictions of the model of a thermal wave penetrating into the solid. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Experimental study of the electrification produced by dispersion of dust into the air

    Page(s): 125 - 131
    Save to Project icon | PDF file iconPDF (730 KB)  

    Some laboratory experiments have been performed to study the electrification of dust clouds created by blowing different types of dusts into a dust chamber. The polarity and magnitude of the space charge in such dust clouds have been found to be sensitive to the mineral constituents of the dust. Even a single dust cloud, if allowed to settle under gravity in a field‐free space with no charge added to it, can have opposite polarities of space charge at different times of its sedimentation. The space charge produced increases with an increase in the length of the surface over which the dust is blown. It also increases with an increase in the temperature and velocity and a decrease in the relative humidity of the blowing air. External electric fields of up to a few hundred V/cm, applied to the surface from which the dust is blown, have little effect on the generated space charge. Size distributions of positively and negatively charged particles show a greater abundance of smaller (∼ 3 μ) particles compared to those of small neutral particles. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fine structures and energy distribution of secondary electron emission from Si(111)

    Page(s): 132 - 137
    Save to Project icon | PDF file iconPDF (483 KB)  

    Some secondary electron (SE) emission characteristics, i.e., total SE's, elastically and inelastically backscattered primaries, true SE's, and plasma loss spectra, of single‐crystal Si(111) were observed as a function of primary energy Ep. A small fraction of total SE's was introduced to a retarding field energy analyzer placed at 45° to the normally incident primary beam. As a result, a fraction of total SE's and of elastically backscattered (including diffracted) primaries showed quite similar fine structure even in detail, when observed as a function of Ep. By filtering a fraction of total SE's into individual energy ranges, the fine structures in true SE's were found at the same Ep's as in elastically backscattered primaries, but were in the opposite direction to the corresponding structures in the elastically backscattered primaries. On the other hand, the fine structures of inelastically backscattered primaries, i.e., energy‐loss primaries, showed quite a complex correlation to those of elastically backscattered primaries. It is concluded that the fine structures in σ (total SE yield) vs Ep and η (backscattering coefficient) vs Ep curves should be caused by the elastically backscattered primaries. The considerable number of electrons subjected to the surface and the first bulk plasma losses were found to be emitted from within a few atomic layers from the surface. Some problems on the Auger electron excitation are also discussed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Thermoelectric and photothermoelectric effects in semiconductors: CdS single crystals

    Page(s): 138 - 144
    Save to Project icon | PDF file iconPDF (567 KB)  

    The quantitative reliability of theoretical expressions for Hall and thermoelectric effects has been tested under thermal equilibrium conditions in high‐conductivity, nondegenerate, and degenerate CdS single crystals, and under nonequilibrium steady‐state and transient conditions in low‐conductivity photosensitive CdS crystals. The thermal equilibrium measurements were made as a function of temperature, hence of scattering and degeneracy, and the nonequilibrium measurements were made as a function of excitation intensity and temperature. Good agreement is found in every case between the values of the electron density and mobility calculated from the Hall effect and the values of these quantities calculated from the thermoelectric effect. The results confirm both the reliability of the present state of the theory for materials like CdS, and the extension of this theory far from equilibrium conditions provided that the equilibrium Fermi level is replaced by the steady‐state or quasi‐Fermi level. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Nonanomalous energy distribution of electrons emitted by a thermionic cathode

    Page(s): 145 - 151
    Save to Project icon | PDF file iconPDF (630 KB)  

    An electron gun with an effective concentric‐spheres electrode geometry has been used to investigate the energy distribution of electrons emitted by a space‐charge‐limited dispenser cathode at four different temperatures. A spherical monochromator is used to select different portions of the initial energy spectrum. Electrons so selected are scattered through 90° by an atomic beam of helium. The initial electron energy is inferred from the accelerating potential needed to attain the 19.3‐eV helium resonance energy. Energy spectra so obtained are compared with computed spectra based on an initially half‐Maxwellian distribution filtered by the space charge in front of the cathode. The form of this space charge is known from an exact solution of Poisson's equation in the spherical geometry of the gun. The only adjustable parameter in the computation is Richardson's constant which is given a value of A = 7 × 104 A/m2 (°K)2. The close agreement between the observed and computed energy spectra is in disagreement with observations of many other investigators. Reasons for this disagreement are suggested. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

Journal of Applied Physics is the American Institute of Physics' (AIP) archival journal for significant new results in applied physics

Full Aims & Scope

Meet Our Editors

Editor
P. James Viccaro
Argonne National Laboratory