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Journal of Applied Physics

Issue 6 • Date May 1967

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Displaying Results 1 - 25 of 78
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • Domain Formation in a Ferromagnetic Plate

    Page(s): 2413 - 2416
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    The nonlinear micromagnetic equations are used to obtain an approximate analytical solution for the distribution of the magnetization vector in the central plane of a ferromagnetic plate with uniaxial magnetocrystalline anisotropy. It is shown that the micromagnetic nucleation mode derived from the linearized equations develops into a strip domain pattern with well‐defined Bloch walls in a rather narrow range of applied magnetic field near the saturation value. The stability of the domain pattern is discussed qualitatively. View full abstract»

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  • Defects in the Compound Bi2Te3 caused by Irradiation with Protons

    Page(s): 2417 - 2422
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    Single‐crystal foils of the compound Bi2Te3 were irradiated with 7.5‐MeV protons at two levels of flux to the same integrated dose of 5.5×1018 protons/cm2. The specimens were examined by transmission electron microscopy. After irradiation with a flux of 1.8×1013 protons/cm2·sec, clusters of point defects ranging in size from approximately 50 to 250 Å were observed. These clusters annealed out during examination in the electron microscope. After irradiation with a flux of 3.0×1013 protons/cm2·sec, clusters of interstitial atoms and clusters of vacancies could be distinguished. Hexagonal areas were observed after irradiation with the higher flux. Irradiation also promoted the rearrangement of dislocations. Segments of dislocations intersected the surface of the specimens, and some dislocations acquired a jagged appearance. View full abstract»

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  • Microwave Faraday Rotation in Nickel‐Powder Artificial Dielectric—A Suggested Explanation

    Page(s): 2422 - 2424
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    It is shown that the anisotropic permeability of the magnetic particles constituting an artificial dielectric provides an explanation for the rotation of the plane of polarization and the variation of the attenuation of a plane‐polarized electromagnetic signal propagating through the dielectric in the presence of a longitudinal magnetic field. The attenuation curve is found to be readily explainable from the nature of variation of the power transmitted into the particles. A more detailed agreement between experimentally observed rotation, attenuation, and computed values is shown to follow if Lewin's formulas for the permeability and permittivity of an artificial dielectric is assumed to be valid also for circularly polarized signals. The effect of the size and permeability of the metal particles on the figure of merit of rotation is also discussed. View full abstract»

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  • Longitudinal Magnetoresistance and Hall Mobility of n‐Type Germanium at High Electric Fields

    Page(s): 2425 - 2427
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    The longitudinal magnetoresistance and Hall mobility of 5‐Ω·cm n‐type germanium have been measured for electric fields applied in the (111) direction up to 4 kV/cm. It has been found that (i) longitudinal magnetoresistance at a particular electric field decreases with an increase in the magnetic field, (ii) for small magnetic fields the longitudinal magnetoresistance decreases with an increase in the electric field, and (iii) the Hall mobility and the ratio of Hall mobility to the conductivity mobility decrease with an increase in the electric field. The experimental value for fields above 1 kV/cm are found to agree with the theoretical values calculated with the assumptions that (i) the scattering is due to the acoustic, optical, and intervalley phonons, (ii) the average energy of the electrons is much larger than that of the optical phonons, (iii) the intervalley phonons affect only the carrier repopulation in the different valleys, and (iv) the value of the optical‐phonon deformation potential constant is 0.8×109 eV/cm. View full abstract»

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  • Cathodoluminescence of MgS:Ce,Ni

    Page(s): 2427 - 2428
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    The phosphor MgS:Ce,Ni is an efficient cathodoluminophor with green to yellow emission and very short decay time. The addition of nickel produces lower efficiency and correspondingly faster decay, the exact relation depending on the cerium concentration. The optimum composition for high efficiency (5–10 lm/W) and fast decay (0.25–0.35 μsec) was found to be MgS:Ce (0.001), Ni (0.0002). The primary green luminescence was shown to result from cerium doping rather than from some other impurity. View full abstract»

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  • Light Scattering by Oriented Dipoles

    Page(s): 2429 - 2432
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    Soleillet's theory of light scattering by a random aggregation of dipoles has been extended through Mueller matrix algebra to formulate a matrix for light scattering by an array of oriented dipoles. The proposed matrix reveals certain interesting characteristics of dipolar scattering. Linear relations between the parameters of the Stokes' vectors of incident and scattered beams have been obtained for the case of oriented dipoles. The applicability of the matrix has been indicated in the case of radiations in the horizontal plane from an ungrounded antenna or an array of antennas oriented in the vertical plane, and in polarization studies of light scattering by oriented polymer films and fibers which have completely aligned long‐chain molecules. View full abstract»

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  • Effect of Impurities on the Annealing Behavior of Irradiated Silicon

    Page(s): 2433 - 2438
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    The effect of impurities on the annealing behavior of irradiated silicon was studied through an investigation of isothermal annealing of minority carrier lifetime in silicon crystals containing phosphorus, arsenic, antimony, or bismuth in the temperature range 100°–180°C. The activation energy for the annealing of vacancy‐impurity complex increased with increasing atom size of the dopant. The values are 0.93, 1.27, 1.84, and 2.22 eV. The frequency factor was also found to be dependent on impurity as well as concentration of the complex. The variation of these parameters is discussed in terms of the lattice strain associated with impurity atoms which have a larger covalent radius than silicon. View full abstract»

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  • Nature of Electrical Contact between Tarnished Surfaces

    Page(s): 2439 - 2441
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    The variation of contact resistance with temperature has been measured on clean and tarnished silver contacts between 77° and 420°K. It is shown that the temperature coefficient of resistance provides a direct method of distinguishing film conduction from metallic conduction in contacts, and conversely that a single measurement at room temperature cannot reliably yield this information. Clean contacts have the positive temperature coefficient of resistance of the conductor metal. A film‐covered contact on the other hand exhibits either of two distinct types of temperature dependence: one with a large negative temperature coefficient, and one that is metallic. It is suggested that these occur according to whether mechanical contact is made on the film or through a small fissure in it. If the contact is mechanically disturbed, the nature of the conduction fluctuates randomly between these two modes. Further, the temperature coefficient of resistance provides a means for distinguishing between semiconducting and tunneling contacts. The experimental observations on silver sulfide tarnish film suggest that electron tunneling is dominant at cryogenic temperatures, but that at normal temperatures the film is an n‐type semiconductor. View full abstract»

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  • Thickness Effects of Electron Scattering at Au‐Film Surfaces

    Page(s): 2442 - 2446
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    The electron scattering at the surfaces of an Au film vacuum deposited on Bi2O3 is analyzed as a function of film thickness using the Fuchs‐Sondheimer theory modified to allow the determination of the scattering parameters separately at each of the film surfaces. The scattering at the air‐Au interface becomes less specular as Au‐film thickness increases. In the analysis the assumption is made that the scattering parameter at the Au-Bi2O3 interface is unaffected by variation in Au‐film thickness. The justification for this assumption is the strong influence of the Bi2O3 on the growth characteristic of the Au film. It is known that a given Au‐film thickness will become continuous when deposited on Bi2O3, whereas a film of that same thickness would be discontinuous deposited on bare glass or quartz. View full abstract»

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  • Fe‐Co and Fe‐V Alloys for Pressure Calibration in the 130‐ to 300‐kbar Region

    Page(s): 2446 - 2449
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    Fe‐Co and Fe‐V alloys, tested in static ultrahigh pressure apparatus, have been found to have resistance jumps resulting from the α to ϵ transformation, as in pure Fe. The pressure of initiation of the transformation increases with the alloy content; from 131 kbar for pure Fe up to 290 kbar for 20 wt% Co. The V alloys rise much faster: 280 kbar at 6 wt%. The Fe‐Co alloys can serve as convenient samples to pressure‐calibrate apparatus in the 160 to 300‐kbar region. The difference between the pressures of initiation of transformation under static conditions, compared to shock conditions, is zero for pure Fe and progressively greater as the alloy content increases. View full abstract»

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  • Anisotropy of Nonelastic Flow in Bone

    Page(s): 2450 - 2455
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    The microdeformation characteristics of 0.010‐in.‐diam compact bone filaments have been measured under torsional loading conditions. The effects of prestrain, recovery, cyclic loading, and specimen orientation on the nature and extent of the nonelastic flow were determined. Correlations are considered between the mechanical behavior and the composite structure of compact bone. View full abstract»

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  • Phase‐Shift‐Corrected Thickness Determination of Silicon Dioxide on Silicon by Ultraviolet Interference

    Page(s): 2455 - 2460
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    A spectrophotometer operating in the ultraviolet region can be used to obtain accurate and precise silicon dioxide thickness determinations on silicon. Excellent accuracy and precision is obtained by considering: (1) the refractive‐index dispersion of the silicon dioxide; and (2) the theoretically calculated phase shifts at the silicon dioxide‐silicon interface based on known optical constants of silicon. Experiments comparing spectrophotometric oxide thickness determinations against VAMFO (variable‐angle monochromatic fringe observation) thickness determinations indicate an accuracy of ±25 Å and a precision of ±15 Å. View full abstract»

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  • Two‐Stream Instability in Semiconductor Plasmas

    Page(s): 2461 - 2465
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    Pines and Schrieffer demonstrated that the two‐stream instability could occur in a high‐mobility semiconductor such as InSb if the conditions ωp+τ+≫10 and T-»T+ are satisfied, where ωp+ is the hole‐plasma frequency, τ+ is the hole‐collision time and T- and T+ are the electron and hole temperatures, respectively. Either condition is difficult to obtain in bulk InSb. The possibility of observing such an instability in a structure consisting of adjacent p and n InSb is considered. The collision condition is reconsidered using a collision term which conserves particles and assuming the somewhat higher electron‐drift velocities (≃electron‐thermal velocity) which are now believed possible. It is concluded that the condition can be relaxed by about an order of magnitude (ωp+τ+≫1). The layered structure could provide the condition T+«T- if it were in contact with liquid helium while a current, passed only in the n region, produced both relative streaming and elevated electron temperatures. A comparative stability analysis in the zero‐temperature fluid limit indicates that the surface space‐charge waves of the layered structure can grow at rates only slightly less than those of the bulk space‐charge waves of the corresponding penetrating stream system. View full abstract»

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  • Fluctuations in Luminescent Junctions

    Page(s): 2465 - 2469
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    Optical‐emission fluctuations from three types of GaAs and Ga(AsP) p‐n junction luminescent diodes have been examined. Characteristic time constants of 12×10-3 and 0.45×10-3 sec are observed in both the optical noise spectra and forward‐current noise spectra of a GaAs diode in which carrier recombinations occur in the junction space‐charge region. More heavily doped junctions (∼1019 cm-3), in which tunnel currents predominate, exhibit 1/f noise. In either case, correlation exists between optical‐emission noise and forward‐current noise, suggesting that carrier transitions responsible for both effects are the same. Only simple photon noise is observed from a Ga(AsP) diode in which junction diffusion currents are significant, although the forward noise spectrum is also 1/f noise. View full abstract»

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  • Effect of MgO on the Crystal‐Growth Defects and Optical Absorption of Flux‐Grown In2O3

    Page(s): 2469 - 2471
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    Crystals of In2O3 grown from a pure flux have inclusions and striations and, because of oxygen deficiency, are nonstoichiometric and almost black. The addition of MgO to the melt produces crystals that have no inclusions or striations, and that have optical properties characteristic of stoichiometric In2O3. Therefore, Mg acts as an efficient compensator of the oxygen deficiency. This paper describes the effect of MgO on the visible optical absorption spectrum and on the crystal defects. One possible model of the role of Mg in compensating In2O3 is discussed briefly. View full abstract»

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  • Microscopic Evidence of Plastic Deformation on Cleaved Germanium Surfaces

    Page(s): 2472 - 2477
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    A study of cleaved germanium surfaces by transmission electron microscopy and gold transfer replicas provides direct and indirect evidence of plastic deformation introduced by the cleavage process at room temperature. The results are interpreted as showing that dislocations move by glide on {111}‐type planes parallel to the surface and at 70°32′ to the surface. Experiments are also reported using copper plating as a technique for decorating surface damage. View full abstract»

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  • Dislocations and Fault Surfaces in Synthetic Quartz

    Page(s): 2477 - 2483
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    Defects in a rather perfect synthetic quartz crystal have been surveyed by x‐ray topography. Etching behavior and stress birefringence were also studied. The crystal, grown from a z‐plate seed, contained Na and Al in concentrations of 50 ppm by weight. The crystal had grown in the c direction with low dislocation density (∼ 3000 lines cm-2). The majority of dislocations made about 10° with the c axis, only 15% had Burgers vectors with a c‐axis component. Cellular growth had developed as growth in the c direction proceeded. The cell walls were identified with fault surfaces made visible by diffraction contrast. These surfaces were inclined at fairly small angles with [0001] and their intersections with (0001) formed an irregular polygonal network. Dislocations congregated in or near the fault surfaces in the later stages of growth. The fault surfaces outcropped at the grooves between protuberances on the rough external crystal surface of mean orientation (0001). The presence of fault fringes indicates impurity segregation in the cell walls: the fringe contrast could arise from a layer a few microns thick with a lattice parameter a few parts in 105 different from that of surrounding material. View full abstract»

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  • Sink‐Terminated Concentration Quenching of Trivalent Gadolinium and Ytterbium Fluorescence

    Page(s): 2484 - 2488
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    The lifetimes of Gd3+ 6P7/2 and Yb3+ 2F5/2 fluorescence in a glass host have been studied at room temperature as a function of concentration, and in the case of Gd3+ as a function of added Eu3+ concentration. The results show that the ions ``concentration quench'' by a mechanism involving the migration of excitational energy from ion to ion until a sink in the structure is reached. This result is significant to the preparation of laser materials. View full abstract»

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  • Observations of Sub‐Unit‐Cell Stacking Elements in Mixed‐Layer Structures by Electron Microscopy

    Page(s): 2488 - 2496
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    The ``hexagonal ferrites'' comprise a quasipolytypic series of ferrimagnetic oxides containing Ba, Fe3+, and a divalent metal cation (Me2+). These encompass a family of hexagonal and rhombohedral mixed‐layer structures derived by the c‐axis stacking of two complex invariant building blocks, mainly ``M'' and ``Y''. The M stacking element is a 5‐anion‐layer block, 11.6 Å in height with the composition BaFe12O19, and the Y stacking element is a 6‐anion‐layer block, 14.5 Å high with the composition Ba2Me22+Fe12O22. The largest series, M2Yn(n=0 to 21), involves the stacking of two M blocks and a variable number of Y blocks. Permutation of the M and Y elements allows mixed‐layer polytypism within a given stoichiometry, i.e., M to Y ratio. More than twenty (20) mixed‐layer structures and their polytypes have been examined by electron microscopy after direct replication of the basal face. Basal faces which were etched with dilute hydrochloric acid exhibit etch steps of sub‐unit‐cell heights. The specific M and Y stacking sequence of a mixed‐layer structure may be obtained by measuring the step‐height ratio, MYx/MYn-x, of two adjacent steps, provided either the shadow angle or the x‐ray c‐axis dimension is known. In addition it has been found that the c‐axis dimension and the specific stacking sequence may be uniquely determined by counting the individual M and Y building blocks which are replicated as separate and distinct etch‐planes on a crystal surface that has been process‐etched. View full abstract»

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  • X‐Ray Study of Proton‐Induced Disorder in Cu3Au

    Page(s): 2497 - 2499
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    Measurement of fundamental and superlattice x‐ray diffraction lines as a function of integrated proton‐bombardment current has been used to determine induced disorder in the surface layers of fully ordered polycrystalline targets of Cu3Au. It is shown that a proton range for induced disorder and the number of disordered atoms created per proton can be inferred from the data. View full abstract»

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  • p‐n Junctions in Compensated Solution‐Grown GaP

    Page(s): 2500 - 2508
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    Two distinct processes are suggested for the formation of p‐n junctions in crystal platelets of GaP grown from Ga solution doped with Zn, Te, and O, over wide ranges of composition and growth conditions. In each growth melt, about one half of the p‐type crystals contain a shallow n‐type surface layer, ∼2 μ in thickness, formed by out‐diffusion of Zn after growth. These p‐n junctions have relatively high (≫10-3) external electroluminescence quantum efficiencies at room temperature. The remaining p‐type crystals contain deeper, less efficient junctions, built into the crystals by impurity segregation effects during growth. The efficiencies of p‐n junctions degrade with the heat treatment at 600°C used to alloy the Ohmic contacts. The extent of degradation correlates with the dislocation density and is ascribed to precipitation. The precipitates nucleate preferentially in the junction plane and grow with subsequent heat treatment. View full abstract»

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  • Elastic Moduli of Single‐Crystal Spinel at 25°C and to 2 kbar

    Page(s): 2508 - 2511
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    The elastic properties of a synthetic single-crystal spinel with a composition of MgO·2.6Al2O3 have been determined at 25°C and up to 2 kbar by measuring propagational velocities of ultrasonic waves using the method of pulse superposition. The isotropic moduli and Poisson's ratio were computed from the single-crystal values using the Voigt-Reuss-Hill approximation. Values of the adiabatic elastic moduli at 1 bar and 2 kbar and at 25°C are c11 c12 c44 1 bar 2985.7 1537.2 1575.8 (kbar) 2 kbar 2995.5 1545.0 1577.5 (kbar). The adiabatic bulk modulus was computed to be 2019.9 kbar, and the pressure derivative of the adiabatic bulk modulus was found to be 4.18. View full abstract»

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  • Dynamic Mechanical Properties of the Transcrystalline Regions in Two Polyolefins

    Page(s): 2512 - 2516
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    The dynamic Young's moduli E of molded films of a polyethylene and a polypropylene were found to decrease with increasing thickness t. An upper limit of E appears to exist when the film thickness is reduced to less than 1 mil. For thicker films, E is inversely proportional to t. Finally, the modulus approaches a lower asymptotic value when t is in excess of 20 mil. The results can be represented quantitatively by a model in which the surface transcrystalline region and the bulk phase of the polymer respond in a parallel combination to the applied stress. The modulus of the transcrystalline region in each polymer is higher than that of the bulk phase. The thickness of a surface region is about 12 μ in polypropylene and 15 μ in polyethylene. The effects of thermal history and the nature of the molded surface were examined briefly. View full abstract»

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  • Comment on the Initial‐Rise Method for Determining Trap Depths

    Page(s): 2516 - 2519
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    For the determination of the trap depth from thermoluminescence and thermally stimuated current‐glow curves commonly the initial‐rise method by Garlick and Gibson is used. This method provides accurate results only if the condition Rh(T0)[2/z-1] ≤f(T0) is fulfilled. R is the retrapping factor, z the filling ratio of the traps at the temperature T0, f the concentration of unoccupied recombination centers, and h the density of trapped electrons. 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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P. James Viccaro
Argonne National Laboratory