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1 May 1967

Volume 38, Issue 6, pp. 2413-2714

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Wing‐Slope Techniques for the Analysis of Langmuir‐Probe Characteristics in a Low‐Density Plasma

Richard T. Bettinger

J. Appl. Phys. 38, 2523 (1967); http://dx.doi.org/10.1063/1.1709941 (5 pages) | Cited 4 times

Online Publication Date: 29 June 2004

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The volt‐ampere characteristics of Langmuir probes utilized in ionospheric investigations and employing ideal geometries (spherical or cylindrical) contain a considerable amount of information, much of which is not utilized in the usual analysis programs. The slope of the V‐i curve for large accelerating potentials contain a substantial amount of information on mass density and temperature. We have developed equations for the current and its slope in this region for both of the above geometries and have applied them to a few typical situations. We conclude that the usefulness of Langmuir‐probe techniques may be appreciably improved by performing a ``total analysis'' on the available information. In some cases, measuring the slope directly will supply the same information with a substantial saving in experimental complexity.

Positive Streamer Spark Breakdown at Low Pressures in Air

T. Oshige

J. Appl. Phys. 38, 2528 (1967); http://dx.doi.org/10.1063/1.1709943 (7 pages) | Cited 8 times

Online Publication Date: 29 June 2004

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No data existed as to the lower pressure limits of streamer breakdown in positive point‐to‐plane geometry. Using a combination of Lichtenberg figure techniques in the coplanar mode and a two‐photomultiplier analysis of the movement of luminous pulses between the electrodes, the streamer mechanism has been observed to 4 Torr in room air; below this pressure, it is too faint to observe. A primary streamer starts from the anode. Its speed of the order of 107 cm∕sec varies across the gap, depending on overvoltage and pressure. It is influenced by encounter with photoelectrically initiated avalanches from the cathode and by streamer‐tip‐cathode fields. On arrival at the cathode, fast space waves of potential gradient travel up the branch tips. Where such waves converge at the junction of the channel branches near the anode, a bright secondary streamer pulse appears. The tips of the midgap event move towards cathode and anode as secondary positive and negative streamers, respectively, at speeds around 106 cm∕sec. The luminosity engendered when the streamers are launched initiates a new negative photoelectrically triggered group of electron avalanches that move up the channel at about 106 cm∕sec. When this group meets the positive secondary streamer tip, the arc channel is completed. Observations leading to this picture constitute the content of this paper.

The Voigt‐Reuss‐Hill Approximation and Elastic Moduli of Polycrystalline MgO, CaF2, β‐ZnS, ZnSe, and CdTe

D. H. Chung and W. R. Buessem

J. Appl. Phys. 38, 2535 (1967); http://dx.doi.org/10.1063/1.1709944 (6 pages) | Cited 39 times

Online Publication Date: 29 June 2004

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The Voigt‐Reuss‐Hill (VRH) approximation, a useful scheme by which anisotropic single‐crystal elastic constants can be converted into isotropic polycrystalline elastic moduli, is shown to apply for moderately anisotropic cubic crystals like MgO, CaF2, β‐ZnS, ZnSe, and CdTe. Experimental values of polycrystalline isotropic elastic moduli for these materials are presented here, and the validity of the VRH approximation is established. The VRH approximation is then discussed for these materials with respect to their elastic anisotropy of crystals. To provide further support to this work, a numerical confirmation on the VRH moduli is made with the use of a high‐speed computer by calculating the mean velocity of sound in crystals and comparing this result with the corresponding quantity calculated from the actual polycrystalline elastic moduli. The general agreement is observed.

Behavior of Saturable‐Absorber Giant‐Pulse Lasers in the Limit of Large Absorber Cross Section

L. E. Erickson and A. Szabo

J. Appl. Phys. 38, 2540 (1967); http://dx.doi.org/10.1063/1.1709945 (3 pages) | Cited 7 times

Online Publication Date: 29 June 2004

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Using a rate‐equation model, it is shown that the behavior of the saturable‐absorber giant‐pulse (SAGP) laser can be adequately described in terms of two parameters for values of the ratio of absorber to laser absorption cross section σ>200: nai′ the normalized initial inversion and στs, where τs is the normalized absorber relaxation time. In the general case, specification of nai′, σ, and τs is required. Theoretical curves of the giant‐pulse output power, energy, and rise‐ and falltimes are presented. The results are applicable in particular to SAGP lasers employing organic‐dye absorbers.

A Phenomenological Theory of Dielectric Response

Donald E. Tilley

J. Appl. Phys. 38, 2543 (1967); http://dx.doi.org/10.1063/1.1709946 (4 pages) | Cited 2 times

Online Publication Date: 29 June 2004

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The phenomenological theory of the electret effect, as developed by Wiseman and Feaster and extended by Perlman and Meunier, is cast into a form which allows a unified treatment of a variety of experiments. Introducing Mikusinski operators, a superposition principle expresses the electric displacement operator as ϵE+Pb with
math
and ϵ=ϵ0+χi+χ, where the operator χ characterizes the slow polarization response and the constant χi gives the fast response. Then, the field E within a dielectric of conductivity c is related to the electrode current density J by the operator equation E=Z(J—J), where Z=1∕(c+sϵ) determines the impedance operator and the operator math = {dPb/dt}−ϵiE(−0) gives the effects of fields applied before t=0. Applications include a derivation of interesting relations discovered by Gross, an evaluation of the accuracy of the quasiequilibrium approximation used by Perlman and Meunier, and the construction of an equivalent circuit.

Temperature Dependence of Photoluminescence in Cadmium‐Doped Epitaxial GaAs

E. W. Williams and R. A. Chapman

J. Appl. Phys. 38, 2547 (1967); http://dx.doi.org/10.1063/1.1709947 (6 pages) | Cited 40 times

Online Publication Date: 29 June 2004

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The relative photoluminescence intensities of band‐to‐band and band‐to‐acceptor radiative recombination were measured as a function of temperature. p‐Type cadmium‐doped epitaxial GaAs was studied. The samples that were used had carrier concentrations in the range of 5×1017 to 3.5×1016∕cc as determined from Hall measurements at 300°K. Over the temperature range 40° to 150°K the two emission peaks were sufficiently resolved so that accurate intensity measurements could be made. The temperature dependence of the band‐to‐acceptor luminescence intensity is in agreement with theoretical estimates of the inverse lifetime for this recombination mechanism. The variation of the diffusion of photoexcited minority carriers as a function of temperature must be considered in order to relate the band‐to‐band luminescence with the lifetime for the mechanism. Minority carrier diffusion theory analysis suggests that the good agreement obtained between theory and experiment for the band‐to‐acceptor luminescence occurs because the total lifetime and the diffusion coefficient have similar temperature dependence in the temperature range studied.

Self‐Diffusion of Tritium in Natural and Synthetic Ice Monocrystals

René O. Ramseier

J. Appl. Phys. 38, 2553 (1967); http://dx.doi.org/10.1063/1.1709948 (4 pages) | Cited 32 times

Online Publication Date: 29 June 2004

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The self‐diffusion of tritium in artificially and naturally grown ice monocrystals, parallel and perpendicular to the optical axis, was studied between −2.5° and −35.9°C. The plane‐source solution to Fick's second law was used in treating the data. An anisotropy of ≈ 12% was observed. The activation energy was found to be 0.62 eV for all cases and D0 ≈ 10 cm2∕sec. Based on the experimental data, it is concluded that the diffusion takes place by a vacancy mechanism, and that entire H2O molecules are diffusing, i.e., molecular diffusion occurs. Theoretical calculations using the atomic‐diffusion theory and Zener's theory for D0 are in excellent agreement with the experimentally determined diffusion coefficient.

Radiation from Current Sources in an Isotropic Plasma

Denis J. Connolly and B. Samuel Tanenbaum

J. Appl. Phys. 38, 2557 (1967); http://dx.doi.org/10.1063/1.1709949 (6 pages) | Cited 1 time

Online Publication Date: 29 June 2004

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Using a three‐fluid model, wave equations are developed for the disturbances due to current sources in a partly ionized gas. The formal solutions to the wave equations are obtained for an elementary current source. The power radiated from the source is given in terms of these solutions and, for the special case in which the electrons are much hotter than the other two constituents, the radiated power is determined in detail.

Thick Cylindrical Coil Systems for Strong Magnetic Fields with Field or Gradient Homogeneities of the 6th to 20th Order

Milan Wayne Garrett

J. Appl. Phys. 38, 2563 (1967); http://dx.doi.org/10.1063/1.1709950 (24 pages) | Cited 52 times

Online Publication Date: 29 June 2004

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For strong homogeneous fields the ideal loop and solenoid elements of a prototype system may be expanded into thick cylindrical coils whose current density is (a) uniform or (b) inversely proportional to the cylindrical radius. Error coefficients of the zonal harmonic series for field or gradient that are cancelled in any given prototype continue to vanish as the elements are expanded, even to fusion, if at each stage the coil boundaries are adjusted by an iterative method. This involves the use of (a) the harmonic source functions Un* or (b) the Legendre functions Pn; either set is best computed by a recursion formula. An alternative method based on Lyle's principle requires no iterations and only trivial calculations. Though it also is valid for systems of any order, it can only expand a set of loops into coils with square cross sections of limited area. Also, the true null coefficients are replaced by small residues proportional to 4th and higher powers of the section dimensions when the second method is used.
The number of tabulated prototype systems of the 6th and 8th orders is increased to more than 200. Since multiply infinite sets of prototypes can be computed for every order higher than the 8th, univariate tables would be inadequate and only a few illustrative examples of such systems are given. Some 150 thick‐walled systems of the 6th or 8th order are listed in several tables, but such a selection can only suggest the wide range of possibilities. These systems have more degrees of freedom than do the corresponding prototypes, and even the 6th order is multivariant. At the 8th order and beyond, the growing redundancy of variables permits the design of systems with a common current density in all coils and with all section dimensions proportional to a set of small integers. Systems of order 4n have paired coils with gaps for lateral access, an advantage that is lacking in the 6th‐order designs.
Efficient computer programs have been written to design systems of all the types so far enumerated, including multiple sets of both prototypes and fully adjusted systems of thick coils for orders from 8 to 20 in steps of 4. Since adequate tabulation of results is ruled out by their diversity and sheer bulk, in view of the wide range of potential applications the programs themselves must be considered the basic research tool. They will be described in detail elsewhere.
As a measure of field inhomogeneity, including contributions from all orders and from both axial and radial field components, the concept of total vector error is developed. The tables include error limits for all systems, and some 40 systems or their error contours are shown in the figures.

Double Magnetic Resonance of Coupled Spins

Clayton Wilson Bates

J. Appl. Phys. 38, 2586 (1967); http://dx.doi.org/10.1063/1.1709951 (9 pages) | Cited 3 times

Online Publication Date: 29 June 2004

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A perturbation procedure is introduced to solve for the probability amplitudes of a system of coupled spins under the action of two rf magnetic fields; one a large saturating signal, the other a relatively weak one. The power absorbed when the saturating signal connects two states in the system is affected by the presence of the second signal connecting two other states especially if both signals have one state in common. The mixing of these states by the saturating signal can become large enough in some instances that it becomes meaningless to speak in terms of population differences and rate equations for these levels. It is further shown that the effect of the intermediate levels is to cause a shift in the resonance frequency for these levels. For widely spaced levels this ``intermediate'' effect may be neglected, but for closely spaced levels it can become appreciable.
A four‐level system is used to illustrate the method. Relaxation effects are neglected.

Effect of Stacking Faults and Twins on the Coercive Force of Thin Magnetic Films

G. A. Walker and H. W. Larson

J. Appl. Phys. 38, 2595 (1967); http://dx.doi.org/10.1063/1.1709952 (4 pages) | Cited 2 times

Online Publication Date: 29 June 2004

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The effects of fairly high densities of extrinsic stacking faults (α approximately as large as 0.3) and twins (β approximately as large as 0.15) on the coercive force, Hc, of thin (less than 700 Å) ferromagnetic Fe‐Co‐Ni films are studied.
Once the effects of strain and small crystallite size on Hc are eliminated, it can be shown that stacking faults and twins increase the Hc, stacking faults having a larger effect than the twins. The introduction of the faults was achieved by sputtering onto ``unclean'' substrates, which gave an initial small‐crystallite‐size layer of about 100 Å, where the crystallite size gradually increased to that found on ``clean'' substrates. At the intersection of the two layers, there was a layer of faults extending about 200 Å into the larger‐crystallite‐size film. The x‐ray technique used to evaluate thickness variation of faults is described.

Stability of an Electrified Liquid Jet

J. M. Schneider, N. R. Lindblad, C. D. Hendricks, and J. M. Crowley

J. Appl. Phys. 38, 2599 (1967); http://dx.doi.org/10.1063/1.1709953 (7 pages) | Cited 46 times

Online Publication Date: 29 June 2004

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A capillary wave of the appropriate wavelength will cause a jet to break up into a stream of uniform‐sized droplets. In this paper, a theoretical expression for droplet size, radius, and spacing in terms of the jet parameters and applied frequency is derived and verified experimentally. For a given jet radius and velocity, the droplet size can be varied from its minimum value, rmin, to approximately 1.6rmin by varying the driving frequency. Also, a theoretical expression for the charge on droplets resulting from the disintegration of a charged jet is shown to agree with the measured value of droplet charge.

Dielectric Properties of Films Formed by Vacuum Evaporation of Silicon Monoxide

Thomas A. Anastasio

J. Appl. Phys. 38, 2606 (1967); http://dx.doi.org/10.1063/1.1709954 (5 pages) | Cited 9 times

Online Publication Date: 29 June 2004

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Dielectric constant and dissipation factor at 1 kHz for films formed by vacuum evaporation of silicon monoxide have been measured as a function of deposition rate and residual oxygen pressure. The dielectric properties are found to depend strongly on the ratio of molecular‐impingement rates at the substrate of O2 and SiO. A model based on changes in the film of the concentrations of Si, SiO, and Si2O3 is proposed to explain the dielectric behavior. The model is compared to optical data reported by other workers.

Third‐Order Elastic Moduli of Gallium Arsenide

H. J. McSkimin and P. Andreatch

J. Appl. Phys. 38, 2610 (1967); http://dx.doi.org/10.1063/1.1709955 (2 pages) | Cited 37 times

Online Publication Date: 29 June 2004

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The six third‐order moduli of GaAs have been determined by measurement of ultrasonic wave velocities (time delays) as a function of applied stress. The adiabatic values (in units of 1012 dyn∕cm2) at 25°C and for zero electric field are very similar to those previously obtained for Si and Ge, as can be seen from the following table:
math

Stress and Displacement Fields of an Edge Dislocation that Climbs with a Uniform Velocity

J. Weertman

J. Appl. Phys. 38, 2612 (1967); http://dx.doi.org/10.1063/1.1709956 (3 pages) | Cited 9 times

Online Publication Date: 29 June 2004

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The stress and displacement fields of an edge dislocation that climbs with a uniform velocity are derived. This solution has application for the determination of the stress and displacement field arising from the anomalous edge component of a moving partial dislocation. The climb motion of the anomalous edge component does not involve diffusion of point defects and is not restricted to slow velocities. The self‐energy of a climbing edge dislocation also is determined. It is found that the self‐energy diverges as (1−V2∕c2)−1∕2, where V is the dislocation velocity and c is the transverse sound velocity when the dislocation velocity approaches the slow sound velocity. This divergence is not as strong as that of the gliding edge dislocation [which is (1−V2∕c2)−3∕2].

Effects of Film Geometry on Superconductive Tunneling

C. J. Gillespie and W. A. Rachinger

J. Appl. Phys. 38, 2615 (1967); http://dx.doi.org/10.1063/1.1709957 (4 pages) | Cited 1 time

Online Publication Date: 29 June 2004

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The effect of exceeding the critical current in one film of a superconducting tunnel junction is examined. The position of the normal superconducting boundary is calculated for a simplified model, and the form of the current‐voltage relation is discussed. Nonuniformity of the film is shown to cause anomalous characteristics observed in Pb‐PbO‐Al junctions.

Photo and Thermal Effects in Compensated Zinc‐Doped Germanium

Robert J. Keyes

J. Appl. Phys. 38, 2619 (1967); http://dx.doi.org/10.1063/1.1709958 (4 pages) | Cited 5 times

Online Publication Date: 29 June 2004

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Below 30°K zinc‐doped germanium exhibits a number of unusual photo and temperature effects when the lowest zinc‐acceptor levels have been filled by electrons from compensatory antimony impurities. These effects include negative photoconductivity, a discontinuity in the temperature dependence of the sample conductivity, as well as the storage of free electrons produced by intrinsic photoexcitation. Hole trapping by the Zn atoms which are singly or doubly ionized is the prime source of these effects. A simple theory is presented which qualitatively explains all of the observed effects and quantitatively fits the data in those areas that are accessible to rigorous measurement.

Slip‐Induced Directional Order in Fe‐Ni Alloys. II. Experimental Observations

G. Y. Chin, E. A. Nesbitt, J. H. Wernick, and L. L. Vanskike

J. Appl. Phys. 38, 2623 (1967); http://dx.doi.org/10.1063/1.1709959 (7 pages) | Cited 7 times

Online Publication Date: 29 June 2004

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The results of an extensive investigation into the nature of slip‐induced directional order in Fe‐Ni alloys near the 75% Ni composition are reported in this paper. Single crystal rods of 4–79 moly‐Permalloy were swaged in the [111] and [001] orientations, as were crystals of the following orientations subjected to plane strain compression: (001) [100], (001) [110], (110) [001], (110) [112], (110) [110], (111) [112], (112) [110] and (112) [111]. Magnetic torque measurements show that all crystals developed a uniaxial anisotropy upon deformation, with the easy magnetic direction in good agreement with our previous theoretical deductions. In the [001] swaged crystal, deviation of the observed easy axis from the calculated value was rationalized in terms of unequal participation of the expected slip systems.
In all cases of plane strain compression, the induced anisotropy constant rose to a maximum value, and then decreased, as the thickness reduction was increased. In one experiment, crystals of a 2%Mo‐76% Ni‐22%Fe alloy received a long‐range‐ordering treatment at 475°C for 190 h prior to plane strain compression in the (110) [112] orientation. The anisotropy energy reached a maximum value of 460 000 erg∕cm3, the highest value of slip‐induced anisotropy thus far reported in Fe‐Ni alloys. As for the anisotropy decrease at large reductions, reorientation of slip‐induced atom pairs as a result of lattice rotation, is undoubtedly a factor. However, this explanation is not valid for the (110) [112] orientation, which remained stable even after 98% reduction. A more widely applicable mechanism is advanced, whereby the decrease in anisotropy is attributed to randomization of the atom pairs through slip across antiphase ordered domain boundaries, both those grown‐in and those created by intersecting slip.
Additional observations have been made of the crystallographic texture and magnetic squareness in cold‐formed polycrystalline Permalloy tapes, which are currently used as magnetic memory elements in storage devices. The results are satisfactorily explained in terms of slip‐induced directional‐order theory. Implications of seeded single crystals to these results are discussed.

Thermal Emission Microscope Studies of Cesium Surface Ionization on Porous Refractory Metals

D. M. Jamba and O. K. Husmann

J. Appl. Phys. 38, 2630 (1967); http://dx.doi.org/10.1063/1.1709960 (10 pages) | Cited 6 times

Online Publication Date: 29 June 2004

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Quantitative thermal emission microscope studies of cesium surface ionization on porous tungsten emitters show under clean surface conditions a surface migration length in the 2‐μ range. The migration length from the pore exit is under this condition fairly independent of the flow rate per pore and the emitter temperature. It is therefore concluded that 107 pores∕cm2 (traverse counting technique) yield maximum ionization efficiency on porous tungsten.
Clean surface conditions were checked by Richardson work function measurements with the built‐in Faraday cage. Also, the ion‐current transition pattern in the threshold region was used for judgement of the surface condition. In case of a contaminated surface, a smooth transition from high to low ion current with decreasing temperature was observed in contrast to the steep ion‐current change‐over in the threshold region under clean surface conditions. Also the surface migration length increased on the contaminated surface.
Molybdenum, sputtered onto the porous tungsten substrate, showed a uniform work function over the entire emitter area with ϕ=4.20 eV.

The Bi I‐II Transition Pressure Measured with a Dead‐Weight Piston Gauge

Peter L. M. Heydemann

J. Appl. Phys. 38, 2640 (1967); http://dx.doi.org/10.1063/1.1709961 (5 pages) | Cited 19 times

Online Publication Date: 29 June 2004

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See Also: Erratum

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A dead‐weight piston gauge was used to determine the bismuth I‐II transition pressure and the volume change at the transition. The transition pressure at 25°C for one sample, believed to contain less than 0.001% impurities, was found to be 25 306 bar, with an estimated uncertainty of 60 bar. With another sample, of substantially less purity and of larger grain size, a transition pressure of 25 500±60 bar was measured. The average relative volume change was 0.035.

Evidence for Damage Regions in Si, GaAs, and InSb Semiconductors Bombarded with High‐Energy Neutrons

M. Bertolotti, T. Papa, D. Sette, and G. Vitali

J. Appl. Phys. 38, 2645 (1967); http://dx.doi.org/10.1063/1.1709962 (3 pages) | Cited 30 times

Online Publication Date: 29 June 2004

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Evidence is reported for the existence of damage regions in Si, GaAs, and InSb irradiated with mono‐energetic 14‐MeV neutrons. The regions were revealed by using a chemical etch and observing carbon replicas of the surface with an electron microscope.

Electrical Currents Produced during the Solidification of Water (Costa Ribeiro Effect)

D. Pinatti and S. Mascarenhas

J. Appl. Phys. 38, 2648 (1967); http://dx.doi.org/10.1063/1.1709963 (5 pages) | Cited 6 times

Online Publication Date: 29 June 2004

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A new type of cell for investigation of the Costa Ribeiro effect in water is described. The rate of change of water to ice can be controlled and measured, while the associated current is measured. The current is found to be proportional to the rate of change of water to ice and between 1 and 10 μC of charge are liberated for each gram of water frozen. The possible importance of the effect for the explanation of atmospheric electricity is discussed.

Correlated Structure in Evaporated Cermet Films

R. E. Scott

J. Appl. Phys. 38, 2652 (1967); http://dx.doi.org/10.1063/1.1709964 (4 pages) | Cited 3 times

Online Publication Date: 29 June 2004

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Flash‐evaporated cermet films (Cr‐SiO) with 77 wt % Cr were examined by x‐ray diffraction. Bragg peaks corresponding to extremely small particles of Cr were observed. For specimens deposited onto room‐temperature Pyrex substrates, a particle size of 20 Å was calculated from the breadths of the peaks. For specimens deposited at 400°C, the Bragg peaks took on an unusual form, consisting of a central peak flanked by strong subsidiary peaks, or sidebands. These sidebands are interpreted as evidence for a strong crystal‐lographic correlation, in both separation and orientation, between chromium particles. A model consisting of short chains of touching Cr particles, with correlation only between nearest‐neighboring particles, and a particle size of 15 to 20 Å, is consistent with the observations on the 400°C specimens.

Control of Ion‐Acoustic Wave Instabilities in a Gaseous Discharge

James T. Coleman

J. Appl. Phys. 38, 2655 (1967); http://dx.doi.org/10.1063/1.1709965 (5 pages) | Cited 3 times

Online Publication Date: 29 June 2004

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The marginal‐stability boundary for spontaneous generation of ion‐acoustic waves in a nonequilibrium plasma is investigated experimentally. The transition from inverse Landau damping to normal Landau damping of the acoustic wave modes is demonstrated by observing the change in forward‐scattering cross section of microwave electromagnetic energy. The measured scattering cross section is compared with that predicted by Ichimaru, using a simple relaxation‐time collision term in the Boltzmann equation. In addition, the collision term of Bhatnagar et al. is used to construct a new marginal‐stability boundary. The latter expression seems to give a better comparison with the observed microwave scattering and demonstrates the superiority of the more realistic collision‐term model.

Bolometric Detection of Coherent 9‐GHz Longitudinal Phonons in X‐Cut Quartz

John M. Andrews and M. W. P. Strandberg

J. Appl. Phys. 38, 2660 (1967); http://dx.doi.org/10.1063/1.1709966 (3 pages) | Cited 8 times

Online Publication Date: 29 June 2004

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Coherent longitudinal phonons at 9.0 GHz in X‐cut quartz rods have been detected by means of high‐speed superconducting bolometers. This type of detector is responsive to ultrasonic intensity and is insensitive to the ultrasonic phase distribution over the endface of the quartz rod, which often disguises the true nature of the echo‐decay envelope when piezoelectric detection of microwave phonons is employed. These bolometers are also capable of detecting the incoherent phonons produced in the dissipation and thermalizing of the coherent microwave phonons.
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