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Journal of Applied Physics

Issue 3 • Date Mar 1972

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Displaying Results 1 - 25 of 114
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • Liquid‐Crystal Diffraction Grating

    Page(s): 767 - 770
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    Application of an electric field to a thin layer of nematic liquid‐crystal causes the formation of a lattice of cylindrical lenses within the liquid‐crystal material. An expression for the far‐field diffraction pattern of light transmitted through this lattice is derived. The observed diffraction pattern agrees with that predicted by the theory. View full abstract»

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  • Elastic and Piezoelectric Properties of Ferroelectric 5PbO · 3GeO2 Crystals

    Page(s): 771 - 775
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    The elastic, piezoelectric, and dielectric constants of a new ferroelectric crystal 5PbO · 3GeO2 have been measured. The measurements involve mostly the use of thickness modes in small plates of various crystallographic orientations. The electromechanical coupling factors turn out to be small, which makes this material unattractive for ultrasonic applications. The temperature characteristics of some piezoelectric constants are presented. The piezoelectric constant d31 vanishes above the Curie point (177 °C), while d22 remains constant above and below the Curie point. View full abstract»

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  • Comment on the Electrohydrodynamic Instability in Nematic Liquids

    Page(s): 776 - 777
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    We show that in a nematic liquid carrying an electrolytic current, an infinitesimal stationary distortion of the uniform orientation pattern does not lead to the formation of space charges. This contradicts the basic assumption of the Carr‐Helfrich model. View full abstract»

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  • Comparative X‐Ray Diffraction and Electron Microscopic Study of the Transformation‐Induced Substructures in the Iron‐Nickel Martensites and Their Influence on the Martensite Properties

    Page(s): 778 - 788
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    Transformation‐induced fine substructures in iron‐nickel martensites have been studied by x‐ray diffraction and electron microscopy. The dislocation density, microstrains, and twinning increased while the dislocation cell size (particle size) decreased, with increasing nickel contents. The effect of the substructures on the hardness and yield strength of the martensites has been discussed. The anisotropic particle‐size values obtained from x‐ray analysis are shown to be due to faulting and/or twinning. From the compound fault probability (1.5α + β) obtained through Warren‐Averbach analysis and the β values obtained from measured peak asymmetry, the stacking‐fault probability α values have been derived and the stacking fault energy γ of the bcc iron‐nickel alloys have been calculated. By extrapolation of the stacking‐fault energy‐composition curve a γ value of 50 ± 10 erg/cm2 has been estimated for pure iron. View full abstract»

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  • Gas Analysis in Films by Laser‐Induced Flash Evaporation Followed by Mass Spectrometry

    Page(s): 789 - 793
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    A new technique for determining the concentration of gases in films has been developed which utilizes laser‐induced flash evaporation followed by mass‐spectrometric analysis of the released gas. It is shown that this technique can be used to perform quantitative analysis for the noble gases and nitrogen in most thin‐film materials on a wide variety of substrates. Under ideal conditions, gas concentrations of a few parts per billion can be detected. Qualitative results have been obtained for other chemically active gases such as oxygen and hydrogen. Approaches are suggested which may also allow quantitative measurements to be made for these gases. Several phenomena which could lead to inaccurate or erroneous measurements are evaluated and methods suggested for minimizing their effect. View full abstract»

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  • Influence of Surface Absorption Characteristics on Reactively Sputtered Films Grown in the Biased and Unbiased Modes

    Page(s): 794 - 799
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    A series of metals have been reactively sputtered in N2Ar mixtures. The results indicate that surface adsorption characteristics greatly influence compound growth and/or gas incorporation. It will be shown that the functional relationship between the measured nitrogen concentrations and PN2 places these metals into one of three groups: (1) metals which chemisorb molecular nitrogen and form a nitride, e.g., W; (2) metals which do not chemisorb nitrogen but form a nitride, e.g., Ni; and, (3) metals which neither chemisorb nitrogen nor form a nitride, e.g., Au. It will also be shown that bias sputtering causes the nitrogen content of tungsten and nickel to decrease while it causes the nitrogen content of gold to increase. The increase for gold is caused by bombardment of the film with energetic N2+, which results in increased sorption of nitrogen. The same effect is present in tungsten and nickel but is overshadowed by resputtering of the previously sorbed nitrogen. It is suggested that the high sputtering yield found for chemisorbed gases is related to a poor mass fit between the sorbed atoms and the metal lattice. View full abstract»

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  • Change in the Intrinsic Optical Absorption of Germanium and Silicon upon Irradiation

    Page(s): 799 - 800
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    Optical constants calculated from ellipsometry data at 0.546 and 0.644 μ for germanium and for Ne+-140‐keV‐bombarded germanium indicated a 0.4‐eV displacement of the optical‐absorption edge to longer wavelength. Optical examination of silicon with a photomultiplier tube gave evidence of a radiation‐induced increase of optical absorption in the tail of the absorption edge. View full abstract»

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  • Surface Elastic‐Wave Velocity and Second‐Harmonic Generation in an Elastically Nonlinear Medium

    Page(s): 800 - 804
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    We report the derivation of a closed‐form expression for the acoustic surface‐wave velocity in an isotropic medium which is elastically nonlinear. An expression is given for the particle displacement of the second harmonic generated, and its variation with distance is shown. The amplitude of the harmonic is proportional to the power density of the fundamental frequency input. Numerical results are given for fused quartz. View full abstract»

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  • General Method for Calculating Derivatives of the Lattice Electrostatic Energy

    Page(s): 804 - 806
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    A method for calculating the derivatives of the lattice electrostatic energy is given which is more general, concise, and systematic than any of the calculations previously performed by Fuchs, Cousins, and Suzuki, Granato, and Thomas. View full abstract»

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  • Dielectric Loss Mechanism in Rutile (TiO2)

    Page(s): 807 - 816
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    A new mechanism to account for the anomalously large dielectric loss and apparent dielectric constant frequently observed in TiO2 is presented, which appears to agree well with experiment. The mechanism involves field‐induced donor migration where the field arises from a difference in work function between the rutile and a metal electrode. This migration results in a large decrease in electronic resistivity in the bulk of the crystal, with relatively thin insulating layers near the electrode surface. Experimental results on a variety of crystals are discussed, and the influence of electrode materials, surface condition, heat treatment, and ambient is analyzed. A method for numerically calculating the resistivity profile of such a crystal from dielectric loss data is described. Results indicative of room‐temperature p‐type conductivity and a voltage‐induced conduction process are presented. View full abstract»

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  • Dislocation Arrangements Resulting from the Diffusion of Zn into Cu: Electron Microscopy

    Page(s): 816 - 820
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    Zinc from the vapor of 9.75‐at. % zinc chips was diffused for 100 h at 780°C into (111) surfaces of thick copper crystals. The density and arrangement of the resulting dislocations were observed on (111) sections by etch pitting and in (111) thin films by transmission electron microscopy. 80% of the dislocations observed by transmission have Burgers vectors in the isoconcentration plane; 70% are organized in low‐angle boundaries which have appreciable tilt character. The subgrain size in the isoconcentration plane is about equal to the distance of that plane from the surface. The dislocation density, the subgrain size, and the character of the subgrain boundaries are compared with those predicted for low‐energy dislocation arrays accommodating the lattice parameter gradient. View full abstract»

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  • Berg‐Barrett X‐Ray Observation of Annealing and Laser‐Induced Damage in Zinc

    Page(s): 821 - 825
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    The Berg-Barrett x-ray diffraction contrast technique has been utilized to study the process of laser-induced damage in a zinc crystal and, also to make observations on the annealing characteristics of the dislocation substructure before and after the laser treatment. Annealing caused individual dislocations to become segmented with various sections of their line lengths becoming parallel to <101¯0>. This preference for a crystallographic orientation of the dislocations seemed related to the equally important observation that the subboundary ``lineage'' structure of the crystals was also largely composed of tilt boundaries of {101¯0} and {112¯0} surfaces. The laser-induced damage required a threshold energy which caused melting, possible vaporization, and appreciable plastic deformation of the matrix material by deformation twinning, nonbasal slip, and microkinking. By comparison with the structural rearrangement observed in the preannealed specimen, the laser-damage zone showed only very retarded changes. View full abstract»

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  • Piezoeletric Current from x‐Cut Quartz Subjected to Short‐Duration Shock‐Wave Loading

    Page(s): 826 - 835
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    When an x‐cut quartz disk is subjected to an impulsive load, the piezoelectric current in an external short circuit is ordinarily an accurate time‐resolved replica of the stress history at the input electrode. Recently, it has been observed that stress pulses whose durations are less than the shock‐wave transit time through the disk sometimes produce anomalous current‐vs‐time responses. In the present work, x‐cut quartz disks are subjected to stress pulses of six different durations and with amplitudes from 9 to 29 kbar. Carefully controlled accurately known pulses are applied to the samples by the impact of projectile‐mounted quartz disks of various thicknesses. The piezoelectric current accompanying each stress pulse is continuously monitored as the pulse propagates through the sample disk. It is found that the anomalous current is a consequence of shock‐induced conductivity in the region of the quartz disk that has been shock loaded and subsequently unloaded to a lower stress value. The threshold for conductivity is found to depend upon both stress amplitude and pulse duration. The threshold is further determined to be controlled both by a critical unloading stress value and by a critical electric field value. The critical unloading stress value is found to be 11.2±0.7 kbar, and the critical electric field is found to be (2.8±0.3) ×105V/cm. View full abstract»

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  • Thermal Damping of Dislocations in Copper and Lead

    Page(s): 835 - 840
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    Ultrasonic attenuation measurements were used to study the thermal part of the dislocation damping factor in copper and lead at frequencies between 10 and 90 MHz in the temperature range 1–180°K. With the assumption that the Granato‐Lücke theory is correct in the limits of small and large dislocation damping, it was found that the Lothe expression for the dislocation damping factor well describes the temperature variation of the measured attenuation. The frequency dependence of the attenuation was found to be in serious disagreement with the Granato‐Lücke prediction. View full abstract»

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  • Edge Dislocations in Anisotropic Inhomogeneous Media

    Page(s): 840 - 844
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    A simple method is given for obtaining the elastic stresses of an edge dislocation near a boundary (grain, interphase, or free boundary) using anisotropic elasticity theory. Exact and explicit solutions are obtained for the cases where the adjacent grains possess certain symmetry elements. The stress functions lead to the image force due to the boundary on the dislocation as Fi=- (Kb2q1/4π), (1/a), where K and q1 are constants involving the elastic constants only, a is the vertical distance of the dislocation from the boundary, and b is the Burgers vector of the dislocation. View full abstract»

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  • Existence of Dislocations at Domain Tips in Ferroelectric Crystal KH2PO4

    Page(s): 845 - 852
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    An analysis is made of the mechanical defects in KH2PO4 compatible with the crystal symmetry. With the theory of crystal dislocations, one can explain several experimental results on domain equilibrium states, domain velocities, and the critical electric field to move the domains in the plane perpendicular to the ferroelectric axis c. The most important result is the possible explanation in terms of mechanical phenomena of the long‐range interaction between domains, and domain freezing at low temperatures. View full abstract»

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  • Short‐Circuit Currents in Charged Dielectrics and Motion of Zero‐Field Planes

    Page(s): 853 - 855
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    When a previously charged dielectric is short circuited, discharge currents result due to the movement of charge carriers in the field of the space charge. It is shown for plane‐parallel geometry that the discharge current is given by the product of charge density at, and velocity of, the zero‐field plane. The resulting expression includes the displacement current. It can also be applied to the case where the dielectric is exposed to a beam of penetrating radiation; it then allows one to evaluate the effect of space charge on the external current. View full abstract»

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  • Propagation and Amplification of Rayleigh Waves and Piezoelectric Leaky Surface Waves in LiNbO3

    Page(s): 856 - 862
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    Velocities and attenuations of piezoelectric leaky surface waves in LiNbO3 are analyzed. As a result, we have found that the effective electromechanical coupling coefficient of the leaky surface wave propagating along the X axis of a 64° rotated Y‐cut plane is very large, K2 = 0.113, and the attenuation of this wave, caused by radiation of the energy into the solid, is 0.036 dB/wavelength for a free surface and goes to zero for a metalized surface. Moreover, K2 of the elastic surface wave for a 130° rotated Y‐cut, X propagation, is found to be larger than that for a Y cut, Z propagation. The theory is verified experimentally. The theoretical analysis and experiments on amplification are performed for these types of waves. In an experiment utilizing the leaky surface wave, net terminal gain of 13 dB/cm is observed for the interaction between the carrier in 200‐Ω cm Si wafer (0.3×3×10 mm), separately mounted on a LiNbO3 surface, and the leaky surface wave. The air gap between the Si wafer and LiNbO3 single crystal is about 0.5 mμ. View full abstract»

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  • Mass Spectrometric Study of Sputtering of KB by Low‐Energy Ar+ and Xe+ Ions

    Page(s): 863 - 866
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    A KBr target was bombarded normally with Ar+ and Xe+ ions, with energies ranging from 25 to 180 eV, in the source of a mass spectrometer capable of detecting neutral and negative sputtered species. A relatively strong signal of Br- ions sputtered from the target was detected, and relative sputtering yield curves were obtained. The yield was greater for Ar+ than for Xe+ ion bombardment at all ion energies. No neutral K0 or Br0 atoms, nor KBr0 molecules, were detected as having been sputtered from the target during bombardment. View full abstract»

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  • The Structure of Electroplated and Vapor‐Deposited Copper Films

    Page(s): 867 - 873
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    The structures of electroplated and vapor‐deposited copper films have been studied by x‐ray diffraction. While there was no evidence of stacking faults in any of these films, the electroplated films were characterized by presence of twins, large thickness‐dependent microstrains, and small particle sizes. The vapor‐deposited films, on the other hand, showed no twins, smaller microstrains, and large thickness‐dependent particle sizes. Analysis of the electrical resistivity of the electroplated films indicated that the twin resistivity of copper is, at most, half of the grain‐boundary resistivity. View full abstract»

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  • Area Influences and Floating Potentials in Langmuir Probe Measurements

    Page(s): 874 - 880
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    An analysis has been conducted on the influence of a relatively small reference electrode in a Langmuir probe measurement of plasma density and temperature. The analysis employs the collisionless theory of Laframboise for spherical and cylindrical probes and in a completely general way includes a broad range of electron densities and temperatures as well as all possible values of ion mass and multiplicity of ionization. It is shown that a ratio α of reference‐electrode area to probe area of 104 will guarantee no distortion of the measurement as a result of a shifting reference‐electrode potential. It is further shown that the constraint on α can be relaxed by approximately two orders of magnitude when the charge‐normalized ion mass mi/Z2 is decreased from 200 to 1 amu and the ratio of reference‐electrode radius to Debye length, RrD, is decreased from 100 to 0. An additional result of the analysis is the dependence of a probe's floating potential on its geometry and radius as well as on the properties of the plasma. A discussion of the latter result reveals in a striking manner the significant differences between the ion‐current responses of spherical and cylindrical probes. View full abstract»

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  • Energy Distribution of Transmitted Secondary Electrons from Porous KCl Films

    Page(s): 880 - 885
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    Energy distribution of secondary electrons from three types of porous films (porous KCl films, porous KCl films with intermediate thin Al layer, porous KCl films containing small amount of amorphous Al) was measured by an ac retarding‐field method. The half‐width of each energy distribution curve was found to be about 10–20 eV. The surface potential of these films was also obtained from the rising point of the energy distribution curve. A single relationship between surface potential and yield and independent of collector voltage was found for constant primary energy. Decay characteristics of the surface potential of three films after ceasing the primary electron bombardment were similar to each other. Secondary currents from a porous KCl film containing a small amount of amorphous Al were found to be considerably more stable compared to those from two other films. A secondary electron emission mechanism is proposed using a channel electron multiplier model. View full abstract»

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  • Preionization Control of Streamer Propagation

    Page(s): 886 - 890
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    Streamer velocity is experimentally shown to vary with preionization in N2 and SF6. The velocity has been controlled over orders of magnitude by introducing pulsed preionization ahead of an already propagated streamer. The preionization is produced by pulsed uv irradiation. The pulsed electric field is uniform in the gap. Avalanche‐streamer conversion times were observed which agree well with prediction. View full abstract»

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  • Note on Determining Electrical Ground Constants from the Mutual Impedance of Small Coplanar Loops

    Page(s): 890 - 891
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    Curves are presented for inverting measured mutual impedance to yield the conductivity and permittivity of an equivalent half space. The displacement currents are allowed for, and the loop separation distance is unrestricted. View full abstract»

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Aims & Scope

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

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Editor
P. James Viccaro
Argonne National Laboratory