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1 Sep 1960

Volume 31, Issue 9, pp. 1511-1697

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Statistics of the Occupation of Dislocation Acceptors (One‐Dimensional Interaction Statistics)

R. M. Broudy and J. W. McClure

J. Appl. Phys. 31, 1511 (1960); http://dx.doi.org/10.1063/1.1735883 (6 pages) | Cited 10 times

Online Publication Date: 16 June 2004

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It is known that dislocations in semiconductors can act as acceptors. This effect has been explained by noting that dislocations with edge components can have unpaired electrons at the terminating half‐plane which act as acceptors; thus a dislocation contains a line of uniformly spaced acceptors only a few angstroms apart. In n‐type materials the dislocation line becomes negatively charged and a positive space charge develops around the line. The occupation statistics are strongly modified by the electrostatic energies involved. Certain approximate solutions to this problem have already been given by W. T. Read. This paper derives improved statistics which, in addition, explicitly take into account interactions between nearest‐neighbor electrons; the results are valid over the complete range of occupation. The statistics are given in terms of two functions which occur in the form of infinite series; the series have been evaluated over a considerable range of occupation and are herein tabulated. Techniques for use of the results are presented. Our theory was applied to a specific problem originally chosen by Read. The results fall between his most accurate approximations for this problem. Statistics have also been derived which take into account the proper spin degeneracy of acceptor states.

Ion‐Bombardment Etching of Synthetic Fibers

Franklin R. Anderson and V. F. Holland

J. Appl. Phys. 31, 1516 (1960); http://dx.doi.org/10.1063/1.1735884 (3 pages) | Cited 6 times

Online Publication Date: 16 June 2004

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An ion‐bombardment etching method was used to prepare synthetic fiber samples for study in the electron microscope. Reproductible results were obtained by bombardment in a constantly changing argon atmosphere at a pressure of 1–2 cm Hg for 2–5 min. The etch patterns produced by this method were characteristic of the orientation of the fiber samples which were investigated.

The Oscillistor—New Type of Semiconductor Oscillator

R. D. Larrabee and M. C. Steele

J. Appl. Phys. 31, 1519 (1960); http://dx.doi.org/10.1063/1.1735885 (5 pages) | Cited 37 times

Online Publication Date: 16 June 2004

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A new magneto‐oscillatory effect has been observed in the electron‐hole plasma within a semiconductor. The plasma can be produced by such agents as contact injection and optical or thermal excitation of minority carriers. When the semiconductor specimen is subjected to an electric field (through suitable contacts) and a magnetic field, current oscillations can be detected across a series load resistance. This device has been termed the oscillistor to suggest a semiconductor oscillator. The experiments suggest that the oscillistor mechanism involves a magnetically induced interaction of the bulk plasma of electrons and holes with the exposed free surface areas of the specimen.

Large Temperature Range Annealing

William Primak

J. Appl. Phys. 31, 1524 (1960); http://dx.doi.org/10.1063/1.1735886 (10 pages) | Cited 55 times

Online Publication Date: 16 June 2004

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Vand's analysis of distributions in activation energy is reexamined through a new derivation which leads to a better approximation to the activation energy spectrum and which permits a treatment of step annealing data. The cases of distributions in frequency factor and the twofold distributions in activation energy and frequency factor are also treated.

Elastic Constants of Bismuth

Yakov Eckstein, A. W. Lawson, and Darrell H. Reneker

J. Appl. Phys. 31, 1534 (1960); http://dx.doi.org/10.1063/1.1735888 (5 pages) | Cited 64 times

Online Publication Date: 16 June 2004

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See Also: Erratum

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The six adiabatic elastic stiffness constants of bismuth have been determined at 301°K by an ultrasonic pulse echo technique. The results are: c11 = 63.5, c33 = 38.1, c44 = 11.30, c66 = 19.4, c14 = +7.23, and c13 = 24.5, all in units of 1010 d∕cm2. These values were redundantly determined by the measurement of 14 different velocities in four different single crystals of zone‐purified bismuth. The velocities are believed accurate to better than 1%, the principal error arising from the uncertainty of the transducer transit time correction. The moduli are in poor agreement with the previously determined static elastic compliance constants reported by Bridgman. Some data on the velocity of sound in bismuth at 98° and at 4.2°K are also presented.

Dislocations in Indented Magnesium Oxide Crystals

A. S. Keh

J. Appl. Phys. 31, 1538 (1960); http://dx.doi.org/10.1063/1.1735889 (8 pages) | Cited 47 times

Online Publication Date: 16 June 2004

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Dislocation rosette patterns produced by spherical and pyramidal indentors on the cleaved surfaces of magnesium oxide crystals were studied in detail. The three‐dimensional arrangement of dislocation loops as deduced from the two‐dimensional etching patterns is discussed. Cracks formed on {110}90 planes around pyramidal indentations are believed to be due to the interaction of dislocations on {110}45 planes. The temperature dependence of hardness was found to be related to the widening of dislocation bands, rather than to the distance of travel of leading dislocations. Some observations were also made on the pinning of dislocations and recovery at elevated temperatures, and on the interaction of dislocations with grown‐in subboundaries.

Temperature Dependence of the Velocity of Sidewise 180° Domain‐Wall Motion in BaTiO3

A. Savage and R. C. Miller

J. Appl. Phys. 31, 1546 (1960); http://dx.doi.org/10.1063/1.1735890 (4 pages) | Cited 9 times

Online Publication Date: 16 June 2004

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The velocity of the sidewise 180° domain‐wall motion in single‐crystal BaTiO3 has been measured over a temperature range from 25° to 100°C as a function of the applied electric field. The velocity, described by v = v∞ exp(−δ∕E), where δ is the activation field, E the applied electric field, and v∞ the extrapolated wall velocity for E = ∞, increases by about four orders of magnitude with this increase in temperature. It was found that the temperature dependence of v lies primarily in δ and not in v∞. The magnitude of δ decreases with increasing temperature and is also dependent on the impurity concentration in the crystal as well as the crystal thickness. The effects of impurities are most pronounced at room temperature, where (1∕δ) (dδ∕dT) is 1% °C−1 for undoped samples and 2% °C−1 for Fe doped samples. Though δ itself is very sensitive to the sample thickness, (1∕δ) (dδ∕dT) does not appear to depend on the crystal thickness. Additional data are required before a critical comparison can be made between experiment and theory.

Circuit Dynamics of the Pinch

J. Killeen and B. A. Lippmann

J. Appl. Phys. 31, 1549 (1960); http://dx.doi.org/10.1063/1.1735891 (6 pages) | Cited 1 time

Online Publication Date: 16 June 2004

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Instead of analyzing a portion of an hydromagnetic pinch apparatus in detail, and replacing the remainder by a boundary condition, the entire pinch apparatus is treated here as a single dynamical system. A circuit equation and a mechanical equation, coupled together, result. These equations describe the dynamical development of the pinch and exhibit explicity its dependence on the physical parameters (electrical and mechanical) of the system. As examples, the equations have been used to analyze the snow‐plow model and the adiabatic pinch, yielding curves that show the geometrical development of the pinch in time, as well as the distribution of mechanical and magnetic energies at any stage. Analogous analyses may be made for other physical quantities of interest, and can be used to adjust the parameters of the system so as to optimize specific pinch characteristics.

Irradiation Effects and Short‐Range Order in Fused Silica and Quartz

R. A. Weeks and C. M. Nelson

J. Appl. Phys. 31, 1555 (1960); http://dx.doi.org/10.1063/1.1735892 (4 pages) | Cited 50 times

Online Publication Date: 16 June 2004

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The eigenvalues of the g tensor of an irradiation produced defect of the quartz structure have been found to be g1 = 2.0003, g2 = 2.0006, g3 = 2.0018. The data on the center are consistent with the assignment of S = ☒. Assuming that the hyperfine interaction with Si29 (I = ☒ and 4.7% abundant) is negligible, the envelope of the line is calculated for 4 widths of the line. Good agreement is found between the calculated envelope for a width of 0.2 oe and the envelope observed in γ‐ray and in neutron‐irradiated (≤1018 fast neutrons∕cm2) silica. The observed envelope deviates from the calculated envelope for increasing neutron irradiation. It is suggested that a correlation of the Si‐O tetrahedra, similar to α‐quartz, exists around any point in the more common forms of silicas and has a diameter of ≥5 A.

Some Electrical Properties of Amorphous Selenium Films

Richard A. Fotland

J. Appl. Phys. 31, 1558 (1960); http://dx.doi.org/10.1063/1.1735893 (8 pages) | Cited 15 times

Online Publication Date: 16 June 2004

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The dark current and photocurrent characteristics of amorphous selenium and arsenic‐selenium alloy films have been investigated. One millisecond after the application of an electric field, the dark current (neglecting capacitance charging) is several orders of magnitude higher than the steady‐state dark current. A hysteresis effect is observed in the dark volt‐ampere curves with the descending voltage branch exhibiting an exponential volt‐ampere relationship. The voltage of a charged Se plate in the dark discharges logarithmically with time as anticipated from the exponential volt‐ampere relationship. Upon admitting air to a freshly evaporated Se plate, a negative surface potential of 150 mv is observed. The phenomenon of ``fatigue'' (i.e., the temporary increase in dark current following an exposure to illumination) obtained with highly absorbed radiation indicates surface barrier effects exert a large measure of control over dark currents. Photogenerated holes and electrons in Se films are trapped with trapping parameters such that the hole range∕unit field is on the order of 10−8 cm2∕v, and the electron range is less than 10−9 cm3∕v. The addition of As to the Se greatly increases the electron effective lifetime. Trapped holes are eliminated in the dark exponentially with time through a process having an activation energy of 0.77 ev. A 40‐mv negative surface photovoltage is observed in Se films upon illumination. This voltage may be accounted for by hole diffusion away from the surface. The addition of As to Se extends the spectral response into the red end of the spectrum, results in the initiation of secondary photocurrent effects, intensifies fatigue effects, and increases the softening temperature of the film.

Chromium‐Doped Titania as a Maser Material

H. J. Gerritsen, S. E. Harrison, and H. R. Lewis

J. Appl. Phys. 31, 1566 (1960); http://dx.doi.org/10.1063/1.1735894 (6 pages) | Cited 27 times

Online Publication Date: 16 June 2004

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A discussion of the paramagnetic properties of Cr3+ in TiO2 is given with particular reference to its use in solid‐state masers. Energy level diagrams are included for magnetic fields in the (110), (1l0), (001), and (100) planes.

Crystallography and Domain Walls in Antiferromagnetic NiO Crystals

Glen A. Slack

J. Appl. Phys. 31, 1571 (1960); http://dx.doi.org/10.1063/1.1735895 (12 pages) | Cited 89 times

Online Publication Date: 16 June 2004

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Twin‐domain walls in large crystals of antiferromagnetic NiO have been observed by specular reflection in optically polished and annealed crystals. These walls can be moved in annealed crystals by small mechanical stresses (<106 d∕cm2) or by moderate magnetic fields (<25 000 oe) to yield completely untwinned crystals. The ease with which a twin wall moves appears to be limited by a spin‐rotation energy loss. Crystallographic measurements of the rhombohedral distortion agree with the x‐ray data, and verify the [111] antiferromagnetic contraction. The anisotropy in the magnetic susceptibility vs field has been measured for untwinned crystals, and is compared with earlier work.

Surface Cleaning by Cathode Sputtering

O. C. Yonts and Don E. Harrison

J. Appl. Phys. 31, 1583 (1960); http://dx.doi.org/10.1063/1.1735896 (2 pages) | Cited 45 times

Online Publication Date: 16 June 2004

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Evidence is presented to indicate that surface recontamination from background gases may be a significant factor in quantitative sputtering measurements, even for beam current densities of 0.1 ma∕cm2 and operating pressures of 5×10−5 mm of Hg. An oversimplified mechanism is discussed which leads to criteria for a cleansurface sputtering experiment.

Apparatus for the Measurement of the Thermal Diffusivity of Solids at High Temperatures

B. Abeles, G. D. Cody, and D. S. Beers

J. Appl. Phys. 31, 1585 (1960); http://dx.doi.org/10.1063/1.1735897 (8 pages) | Cited 50 times

Online Publication Date: 16 June 2004

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An apparatus is described for measuring the thermal diffusivity of solids in the temperature range 30°–1000°C. It employs a method in which the dispersion and the attenuation of a thermal wave, propagated through the solid, are measured. The theory underlying this method is presented, and results are given of measurements on Armco iron and germanium.

Negative Hydrogen and Deuterium Ion Beams

Sanborn F. Philp

J. Appl. Phys. 31, 1592 (1960); http://dx.doi.org/10.1063/1.1735898 (5 pages) | Cited 3 times

Online Publication Date: 16 June 2004

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The charge state of a monoenergetic beam of hydrogen atomic and molecular ions traversing a hydrogen gas target has been measured as a function of the energy of the beam and the thickness of the gas target. The yield of negative ions from protons has a maximum of 1.5% at 13 kev. From diatomic and triatomic molecular ions the maximum yields were 3.0% and 4.5% at 26 and 39 kev, respectively. The experiments have also been performed with deuterium ions traversing the hydrogen gas target. The deuterium results are almost identical with those of hydrogen if the energy scale for the hydrogen data is multiplied by two.

Scattering of Electromagnetic Waves from an Infinitely Long Magnetized Cylindrical Plasma

P. M. Platzman and H. T. Ozaki

J. Appl. Phys. 31, 1597 (1960); http://dx.doi.org/10.1063/1.1735899 (5 pages) | Cited 16 times

Online Publication Date: 16 June 2004

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The magnetically contained plasma is characterized, in an average way, in terms of its macroscopic dielectric tensor. The problem of the scattering of plane electromagnetic waves from a uniform cylindrically symmetric plasma configuration is solved analytically. Numerical results for the uniform case are obtained and graphed for interesting ranges of the parameters involved. Possible applications of the results for use in investigating the plasma's properties are discussed.

Effect of Orientation on Strength of a Model Solid

A. Robinson, J. E. Osborn, and C. C. Hsiao

J. Appl. Phys. 31, 1602 (1960); http://dx.doi.org/10.1063/1.1735900 (3 pages) | Cited 3 times

Online Publication Date: 16 June 2004

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A mathematical analysis is given to describe the effect of orientation on the variation of the mechanical strength of a model solid. For the simple state of uniaxial orientation the fracture strength in the direction of orientation is evaluated as a function of the degree of orientation in terms of the orientation strain and the strength of the unoriented solid. Assuming the fracture strain remains constant, the maximum fracture strength obtainable for a perfectly oriented solid is found to be six times that of the solid without preferred orientation.

Magnetostatic Modes in Disks and Rods

J. F. Dillon

J. Appl. Phys. 31, 1605 (1960); http://dx.doi.org/10.1063/1.1735901 (10 pages) | Cited 61 times

Online Publication Date: 16 June 2004

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Ferrimagnetic‐resonance experiments have been performed using disk‐ and rod‐shaped samples cut from single crystals of a manganese ferrite and of yttrium iron garnet. A multiplicity of absorption maxima were observed which can be identified as magnetostatic modes. The excitation of different sets of modes by rf magnetic field configurations of varying symmetries aids in assigning indices to the modes observed. By far the narrowest lines were observed in thin disks with the steady field normal to the plane of the disk.

Dielectric Properties of Lead Titanate Zirconate Ceramics at Very Low Frequencies

Robert Gerson

J. Appl. Phys. 31, 1615 (1960); http://dx.doi.org/10.1063/1.1735902 (3 pages) | Cited 3 times

Online Publication Date: 16 June 2004

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Dielectric properties of lead titanate zirconate were determined between room temperature and 140°C at frequencies between 0.1 and 10 cps. A measured increase in dielectric constant and dissipation factor at low frequency and high temperature was interpreted as an anomalous conduction phenomenon, rather than as an effect due to ferroelectric polarization. Over the frequency and temperature range studied the relationship between the real and the imaginary components of the dielectric constant was found to be linear. The data for unpoled ceramic and for material which had been poled to a maximum in piezoelectric activity were quite similar.

High‐Frequency Breakdown of Air

Donald Kelly and Henry Margenau

J. Appl. Phys. 31, 1617 (1960); http://dx.doi.org/10.1063/1.1735903 (4 pages) | Cited 4 times

Online Publication Date: 16 June 2004

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Kinetic theory is applied to the problem of ionization breakdown of the air surrounding a high‐speed vehicle. It is found that electrons are removed primarily by being swept out of the field of the moving antenna, and that in the interesting cases this action predominates over diffusion losses. Breakdown voltages are plotted against altitude for frequencies of 225 Mc, 1 kMc, and 10 kMc. The theory may offer an explanation of some types of signal loss during missile flights.

Bounds on the Nonlinear Diffusion Controlled Growth Rate of Spherical Precipitates

J. A. Morrison and H. L. Frisch

J. Appl. Phys. 31, 1621 (1960); http://dx.doi.org/10.1063/1.1735904 (7 pages) | Cited 3 times

Online Publication Date: 16 June 2004

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This paper considers a nonlinear diffusion problem in which there is a change of phase. The physical situation is e.g., the diffusion of solute in a crystal towards a growing precipitate. The nonlinear‐diffusion coefficient is a function of the local concentration of solute. A radially symmetric precipitate which grows at a rate proportional to the square root of the time is considered in n dimensions (n=1, 2, 3); thus ρ=s(D0t)☒, where ρ is the radius, D0 is a constant having dimensions of area∕time and s is a number, the quantity of particular interest. A comparison theorem is established which, in part, states that s increases with increasing diffusion coefficient. A consequence of the theorem is that a unique value of s is associated with a prescribed diffusion coefficient. The comparison theorem also leads to bounds on s. Some other bounds, involving functionals of the diffusion coefficient, are also obtained for s.

Temperature Dependence of the Adiabatic Elastic Moduli of Single‐Crystal Alpha Uranium

H. J. McSkimin and E. S. Fisher

J. Appl. Phys. 31, 1627 (1960); http://dx.doi.org/10.1063/1.1735905 (13 pages) | Cited 22 times

Online Publication Date: 16 June 2004

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The ultrasonic‐wave velocities in small alpha‐uranium single crystals have been measured at various temperatures using the phase‐comparison technique. Details in the experimental procedure, direct computation of the stiffness moduli, and cross‐checking by indirect methods are given. The temperature dependence of the moduli are reported for the range −195° to +300°C for c11, c22, and c33 and −195° to +35°C for the remaining 6 principal moduli. The results show a very marked abnormal temperature dependence of the elasticity in the [100] direction; c11 decreases with temperature below −17.2°C and the linear compressibility in [100] increases from +35° to −195°C. The bulk modulus passes through a maximum at −100°C. These abnormalities indicate a strong temperature dependence of the electron interactions involved in the second nearest‐neighbor bond.

Photovoltaic Effect Derived from the Carnot Cycle

A. Rose

J. Appl. Phys. 31, 1640 (1960); http://dx.doi.org/10.1063/1.1735906 (2 pages) | Cited 12 times

Online Publication Date: 16 June 2004

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An expression for the maximum power derivable from any photovoltaic device is developed in terms of the incident light intensity measured in units of black body radiation. The expression shows the linear dependence of photovoltage on light intensity at low light levels, the logarithmic dependence at intermediate light levels and the saturation at high light levels. The analysis is used to resolve a paradox proposed by W. Shockley.

Walker Modes in Large Ferrite Samples

B. A. Auld

J. Appl. Phys. 31, 1642 (1960); http://dx.doi.org/10.1063/1.1735907 (6 pages) | Cited 40 times

Online Publication Date: 16 June 2004

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The modes of resonance for a ferrite strip and a ferrite post resonator between conducting planes are found by taking appropriate combinations of uniform plane‐wave solutions. It is shown that magnetostatic resonances (Walker modes) may exist even when the resonator dimensions are arbitrarily large, provided the mode indices satisfy certain restrictions.

Generation of Phonons in High‐Power Ferromagnetic Resonance Experiments

Ernst Schlömann

J. Appl. Phys. 31, 1647 (1960); http://dx.doi.org/10.1063/1.1735909 (10 pages) | Cited 86 times

Online Publication Date: 16 June 2004

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The magnetoelastic energy of ferromagnets leads to a coupling between spin waves and elastic vibrations. Because of this coupling the normal modes are not purely magnetic or purely elastic but contain admixtures of both kinds of excitation, the mixing being strongest when the unperturbed waves have the same frequency and wavelength. It is shown theoretically that under suitable conditions (of frequency, dc field, and sample shape) coupled magnetoelastic waves with wavelengths of the order of 1 μ or less can be generated in high‐power ferromagnetic resonance experiments. The magnetoelastic interaction increases the threshold precession angle of the uniform mode, the fractional increase being proportional to the group velocity times the relaxation time for spin waves divided by the same quantity for transverse phonons.
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