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1 Aug 1963

Volume 34, Issue 8, pp. 2125-2532

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Tear Marks on Cleaved Germanium Surfaces

D. Haneman and E. N. Pugh

J. Appl. Phys. 34, 2269 (1963); http://dx.doi.org/10.1063/1.1702727 (4 pages) | Cited 18 times

Online Publication Date: 9 June 2004

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A microscopic study has been made of the origin and nature of tear marks in germanium. The observations suggest that the tear marks can originate in two different ways. The majority are thought to occur when the crack attains a critical velocity, the lattice disturbances set up ahead of the advancing crack deflecting the crack onto different levels. The second type is formed when the curvature of the fracture surface changes abruptly. Taper sections show that the steps at both types of tear mark are identical in profile; they are generally perpendicular to the cleavage surface but frequently contain curved segments.

Gradients in Mercury—Rare‐Gas Discharges

P. J. Walsh, G. W. Manning, and D. A. Larson

J. Appl. Phys. 34, 2273 (1963); http://dx.doi.org/10.1063/1.1702728 (5 pages) | Cited 3 times

Online Publication Date: 9 June 2004

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Mercury—rare‐gas discharges at low mercury pressures and moderate rare‐gas pressures form one of the simplest mixed‐gas systems. The mercury supplies the ionization while the rare gas controls particle motions. The product ER is expected to depend upon paR, pmR, I∕Rn. E is the positive column gradient, R the tube radius, pm and pa the mercury and rare‐gas pressures, respectively, and n is expected to vary in the vicinity of 1 or 2. The quantity I∕Rn is a sensitive indicator of any processes in the discharge which are not linear in the electron density. It is important in single‐component discharges also. DC gradient measurements were made in mercury—argon discharges and verify the expected behavior. The ranges covered were 1.0 to 2.1 in., 1.0 to 75 μ, 0.7 to 35 mm, and 0.1 to 3.0 A, respectively, for R, pm, pa, and I, respectively. The behavior of n is partly explained by two‐stage ionization involving resonance atoms whose lifetimes are governed by the imprisonment of resonance radiation. It is also shown how to reduce the gradient measurements in one mercury—rare‐gas combination to those in another rare‐gas combination. Comparison of mercury—argon and mercury—krypton gradients on this basis indicate that the average electron collision cross section in krypton is 1.4 times that in argon for energies near one electron volt.

Applicability of the Band Model to Metal‐Free Phthalocyanine Single Crystals

George H. Heilmeier, George Warfield, and Sol E. Harrison

J. Appl. Phys. 34, 2278 (1963); http://dx.doi.org/10.1063/1.1702729 (4 pages) | Cited 20 times

Online Publication Date: 9 June 2004

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The applicability of the band model to explain conduction in metal‐free phthalocyanine is suggested by the equality of the thermal acrivation energy for electrical conduction, the energy for first optical absorption, and the energy for the initiation of photoconductivity. Further support for the band model is furnished by the similarities between phthalocyanine and anthracene since evidence has been advanced for the band‐model approach in anthracene. The existence of tightly bound excitons is shown to be an unimportant consideration in conduction processes where the band model is applicable and the same equality among the aforementioned experimental data is obtained. Still further evidence for the band approach comes from Hall measurements. If the Hall data are interrpeted assuming the band approach is feasible, the calculated free‐carrier concentration agrees quite well with that found from bulk current measurements.

Pumping Effects Contributing to the Excitation of Phonon Instabilities in Ferromagnetic Insulators

B. A. Auld, R. E. Tokheim, and D. K. Winslow

J. Appl. Phys. 34, 2281 (1963); http://dx.doi.org/10.1063/1.1702730 (6 pages) | Cited 7 times

Online Publication Date: 9 June 2004

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A survey is made of mechanisms contributing to the excitation of phonon instabilities in ferromagnetic insulators. The distinction between the morphic and intrinsic dependence of elastic stiffness on the direction of magnetization is discussed, and conclusions are drawn about the relative importance of morphic and intrinsic pumping effects. Transverse and parallel magnetoelastic pumping effects are described, and a theory of transverse magnetoelastic pumping is developed for both cubic and uniaxial crystals. An estimate of the transverse magnetoelastic pump threshold for Zn2Y is given.

Changes in Electron Concentration of Donor‐Doped GaAs Crystals Caused by Annealing

C. S. Fuller and K. B. Wolfstirn

J. Appl. Phys. 34, 2287 (1963); http://dx.doi.org/10.1063/1.1702731 (3 pages) | Cited 31 times

Online Publication Date: 9 June 2004

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GaAs doped with ∼1019 cm−3 Se or Te shows reversible temperature‐dependent changes in electron (donor) concentration over the temperature range 650 to 1100°C. Crystals containing between 2×1018 cm−3 to approximately 1019 cm−3 donors conform to the same equilibrium curve with an enthalpy of ∼0.5 eV. The behavior is that expected for a solubility equilibrium. Evidence against an equilibrium involving donor precipitation is presented, and the suggestion that the donors may interact to form molecules is discussed.

Spectral Output and Spiking Behavior of Solid‐State Lasers

C. L. Tang, H. Statz, and G. deMars

J. Appl. Phys. 34, 2289 (1963); http://dx.doi.org/10.1063/1.1702732 (7 pages) | Cited 163 times

Online Publication Date: 9 June 2004

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Experiments show that conventional solid‐state lasers can go into oscillation simultaneously in many modes. This is somewhat surprising since it appears impossible to ``eat holes'' in temperature‐broadened lines and thus only one or, at most, a few modes should be able to oscillate. However, the spatial variation in the field intensity of the various modes produces nonuniform distributions in the inverted population and one can show that there is little tendency for these distributions to smooth out due to spatial cross relaxation. Such nonuniform distributions could lead to simultaneous oscillation in many modes. Formulas which relate the number of unstable modes to the pump power and various other maser parameters are obtained. The results show that it is exceedingly difficult to obtain single mode operation in conventional masers at high pumping levels. Ways to avoid a nonuniform distribution density and methods to achieve high‐power single‐mode operation in practice are discussed. It is also possible to show the effect of slow spatial cross relaxation on the spiking behavior.

Visual Observation of Piezoelectric Modes

A. J. DeMaria and G. Barnard

J. Appl. Phys. 34, 2296 (1963); http://dx.doi.org/10.1063/1.1702733 (2 pages) | Cited 1 time

Online Publication Date: 9 June 2004

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The rotation of the optical index ellipsoid of piezoelectric crystals by an electric field has been widely used for the modulation of light. In particular, KDP and ADP crystals have found extensive use because of their large electro‐optical (Pockel) effect; whereas, quartz crystals have found no application for this purpose because of their low Pockel effect. This paper reports experiments in which the rotation of the index ellipsoid of a quartz crystal by the crystal's piezoelectric resonant modes has been used: (1) to modulate in amplitude a laser beam at a fixed frequency and (2) to trace the piezoelectric modes by mean of an X‐Y plotter.

Structural Properties of Cleaved Silicon and Germanium Surfaces

J. J. Lander, G. W. Gobeli, and J. Morrison

J. Appl. Phys. 34, 2298 (1963); http://dx.doi.org/10.1063/1.1702734 (9 pages) | Cited 171 times

Online Publication Date: 9 June 2004

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Structures of silicon and germanium (111) surfaces produced at room temperature by the Gobeli—Allen cleavage technique have been studied by low‐energy electron diffraction. Both have a rectangular unit mesh which measures √3×1 with respect to the parallel threefold symmetrical substrate mesh. Thus three domain orientations can occur and various combinations of them have been observed. Step disorder, generally peripheral, with a high degree of variability was also observed. Transitions at higher temperatures to the structures, probably more stable, reported previously by Lander and Morrison took place. This confirms the conclusion that the latter structures are properties of the clean surfaces. Implications of these results for surface physics and chemistry are discussed. The inherent difficulty of predicting theoretically the surface structures of these and many other systems is emphasized. These results demonstrate the complexity of surface‐structure phenomena, the power of the display type of low‐energy electron diffraction equipment, and uses of proper cleavage techniques.

Analysis of Thin‐Film Germanium Epitaxially Deposited onto Calcium Fluoride

Arnold L. Pundsack

J. Appl. Phys. 34, 2306 (1963); http://dx.doi.org/10.1063/1.1702735 (3 pages) | Cited 9 times

Online Publication Date: 9 June 2004

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An experimental investigation of the formation conditions of thin‐film Ge epitaxially deposited onto (111) surfaces of CaF2 and the resultant physical and electrical character is presented. The amorphous to crystalline transition region was found to be between 320° and 400°C, and the best single‐crystal orientation was found between 550° and 575°C. Average values of the mobility, conductivity, and the hole concentrations are also reported with an explanation of the problems encountered in their determination.

A Reanalysis of Short‐Range Order in Cu3Au

C. B. Walker and D. T. Keating

J. Appl. Phys. 34, 2309 (1963); http://dx.doi.org/10.1063/1.1702736 (4 pages) | Cited 2 times

Online Publication Date: 9 June 2004

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Cowley's measurements of the short‐range order parameters αi in Cu3Au at T=405°C have been reevaluated taking into account the effects of thermal vibrations and static displacements due to differing atomic sizes. The separate corrections for the thermal vibrations and the first‐neighbor atomic size factor are found to be quite large, demonstrating their importance in the usual experiments. When combined, the corrections in this case largely cancel, and only the values of α1 and α3 are appreciably changed. The corrected values are: α1=−0.113, α2=+0.185, α3=−0.009, α4=+0.082, and α5=−0.058.

Effect of Hydrostatic Pressures on the Crystallization Kinetics of Natural Rubber

Gordon M. Martin and Leo Mandelkern

J. Appl. Phys. 34, 2312 (1963); http://dx.doi.org/10.1063/1.1702737 (6 pages) | Cited 7 times

Online Publication Date: 9 June 2004

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The crystallization kinetics of natural rubber were investigated, utilizing dilatometric techniques, over an extended temperature range under hydrostatic pressures up to 800 kg∕cm2. Irrespective of pressure, the isothermal crystallization displayed good adherence to the general mathematical formulation of the kinetics of phase changes as modified for the crystallization of chain‐like molecules. Nucleation control is indicated at the higher temperatures. The rate of crystallization increases with increasing pressure at constant temperature as a consequence of the increased supercooling. At lower temperatures, transport terms dominate with the rate increasing with temperature at constant pressure. Over the temperature range accessible to study, the data are quantitatively explained by utilizing an activation energy for transport which is independent of temperature but which increases slightly with pressure.

Self‐Diffusion in Polycrystalline Yttrium Oxide

Michael F. Berard and D. R. Wilder

J. Appl. Phys. 34, 2318 (1963); http://dx.doi.org/10.1063/1.1702738 (4 pages) | Cited 15 times

Online Publication Date: 9 June 2004

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The self‐diffusion coefficient of yttrium in polycrystalline yttrium oxide determined in the temperature range 1400° to 1800°C is
math
.

Multiple Charge Exchange of an Accelerated Positive‐Ion Beam in a Neutral Gas

P. Parzen

J. Appl. Phys. 34, 2322 (1963); http://dx.doi.org/10.1063/1.1702739 (5 pages)

Online Publication Date: 9 June 2004

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Charge exchange has been suggested as a means of neutralizing the positive‐ion beam in an ion propulsion engine. An important consideration is a study of the multiple charge‐exchange process of a positive‐ion beam in a neutral gas with an accelerating electric field. The problen is treated by solving the transport equation with a collision term corresponding to the charge‐exchange process. Under certain simplifying assumptions, the transport equation is solved in the general case of an arbitrary spatial (one dimensional) variation of electric field and mean free path. Explicit results for the positive‐ion particle density, thrust, and energy flux densities are obtained in the case of a uniform field.

New Type of Thermoplastic Deformation

P. J. Cressman

J. Appl. Phys. 34, 2327 (1963); http://dx.doi.org/10.1063/1.1702740 (4 pages) | Cited 15 times

Online Publication Date: 9 June 2004

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When certain thermoplastics are coated on a conducting substrate and uniformly charged and softened by heat, a wrinkling type of deformation occurs. It is found that the deformation will not occur below a critical value of the surface charge density. A mechanism is proposed in which the surface tension of the thermoplastic is reduced by the presence of the surface charge. Experimental results indicate that the surface potential at threshold varies as the one‐half power of the film thickness, which is predicted by the mechanism proposed. A one‐dimensional model is presented which predicts that a deformation will occur; however, quantitative agreement of the model with experimental data is not obtained.

Compressibility of Solids and Liquids at High Pressures

Melvin A. Cook and Leo A. Rogers

J. Appl. Phys. 34, 2330 (1963); http://dx.doi.org/10.1063/1.1702741 (7 pages) | Cited 21 times

Online Publication Date: 9 June 2004

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An equation for compressibility (identical in form to the Tait equation) derived previously from the virial theorem and the Fermi—Thomas atomic model is modified on the assumption that one of its parameters (αβ0) is reciprocally related to the internal pressure when the cohesive energy density is assumed to be an essential part of the internal pressure. Pressure—volume data for about fifty homonuclear solids, two alloy systems, twenty ionic compounds, and five secondary bonded liquids are analyzed and the model found to fit with surprising accuracy when due consideration is given to pressure‐induced phase or polymorphic changes and thermodynamic ``holes'' (most important near, and above, the melting point) that may contribute appreciably to specific volume. Data from static and shock methods of compression are considered and the differences noted. The model is apparently applicable to the compression of homonuclear solids and liquids, if indeed not all condensed materials in general.

Elastic Stress Field of an Angular Dislocation

J. L. Hokanson

J. Appl. Phys. 34, 2337 (1963); http://dx.doi.org/10.1063/1.1702742 (4 pages) | Cited 12 times

Online Publication Date: 9 June 2004

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An angular dislocation lies along a continuous curve which is the union of two semiinfinite straight lines. The isotropic elastic stress components are derived for three angular dislocations which are distinguished by having orthogonal Burgers' vectors. The stress field of an angular dislocation with an arbitrary Burgers' vector can be found by superposition of these results.

Plastic Deformation in Magnesium Oxide Crystals Subjected to Rolling‐Contact Stresses

M. F. Amateau and J. W. Spretnak

J. Appl. Phys. 34, 2340 (1963); http://dx.doi.org/10.1063/1.1702743 (6 pages) | Cited 5 times

Online Publication Date: 9 June 2004

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Magnesium oxide single crystals were subjected to rolling‐contact loads, in the range from 130 000‐psi to 173 000‐psi Hertz stress, by rolling a ⅛‐in. ball on a (001) plane in the [010] direction. The resulting plastic deformation indicated that the stress distribution is not very different than that predicted for isotropic, elastic media. Slip occurred predominantly on the glide planes, which coincided with the planes of maximum shear stress. Plastic deformation was caused by the operation of dislocation sources beneath the surface near the region of the calculated maximum shear stress. The depth of penetration and the number of slip lines were greater on those {110}45 planes which intersected the rolling surface parallel rather than normal to the rolling direction.

Theory of Pulse Propagation in a Laser Amplifier

Lee M. Frantz and John S. Nodvik

J. Appl. Phys. 34, 2346 (1963); http://dx.doi.org/10.1063/1.1702744 (4 pages) | Cited 247 times

Online Publication Date: 9 June 2004

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The growth of a radiation pulse traversing a medium with an inverted population is described by nonlinear, time‐dependent photon transport equations, which account for the effect of the radiation on the medium as well as vice versa. The equations are solved in closed form for an arbitrary input pulse and an arbitrary initial distribution of inverted population. The solutions are discussed in detail for the particular cases of a square pulse and a Lorentzian pulse, both with a uniform initial population inversion.

Physical Properties of Titanium. III. The Specific Heat

Lawrence Rozier Holland

J. Appl. Phys. 34, 2350 (1963); http://dx.doi.org/10.1063/1.1702745 (8 pages) | Cited 25 times

Online Publication Date: 9 June 2004

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The specific heat of titanium has been measured over a temperature range from 600° to 1345°K. The specific heat at 600°K is 0.72 J∕g°K ±2.5%, and increases to 0.93 J∕g°K ±6% just below the transition, which takes place at 1155°K. Above this point the specific heat drops to 0.75 J∕g°K ±4%, where it appears to remain fairly constant. The increase of the specific heat to 1.7 times the Dulong and Petit value is interpreted as an effect of anharmonic terms in the potential of the atomic oscillators, as proposed by Born and Brody.
The samples were heated by alternating current, varying in frequency from 8.63 to 14.35 cps, causing a temperature fluctuation at twice the heating current frequency, and a resultant resistance fluctuation. The resistance fluctuation was observed electrically, and from it, through the measured temperature coefficient of resistance, the temperature fluctuations and specific heat were calculated.

Radio‐Frequency Vibrations of Rectangular AT‐Cut Quartz Plates

Issac Koga

J. Appl. Phys. 34, 2357 (1963); http://dx.doi.org/10.1063/1.1702746 (9 pages) | Cited 13 times

Online Publication Date: 9 June 2004

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A combined theoretical and experimental study is presented of the coupled thickness shear and flexural vibration modes of rectangular AT‐cut quartz plates. The theoretical approach (taking into account piezoelectric effects) involves a variational technique which allows for a significant refinement of the mathematical analysis over that heretofore presented in the literature. A reliable experimental technique was used to obtain the functional dependence of frequency vs crystal dimensions. Comparison of experimental crystal resonant frequencies and polarization distributions with those derived from our theory reveals excellent agreement. A discussion is included describing the nature and significance of charts relating resonant frequencies with the ratio length∕thickness of crystal dimensions.

Hardening of KCl by Electron and Gamma Irradiation

W. A. Sibley and E. Sonder

J. Appl. Phys. 34, 2366 (1963); http://dx.doi.org/10.1063/1.1702747 (5 pages) | Cited 48 times

Online Publication Date: 9 June 2004

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See Also: Erratum

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Measurements of the flow stress and F‐band coloration have been made at room temperature on a number of different samples of KCl as a function of gamma and electron irradiation. The rate of increase of flow stress with irradiation is found to be greater (or smaller) in those samples and for those irradiation conditions for which the coloring rate is greater (or smaller). Moreover, the flow stress increase in any set of samples is proportional to the square root of the F‐band absorption. The implication is that hardening is caused either by F centers or other defects whose production is related to the production of F centers. Since bleaching of F centers does not produce any softening, and since the magnitude of the hardening is of the order of magnitude to be expected for interstitial type defects, the conclusion is drawn that the increase of flow stress due to irradiation of KCl is caused by interstitial Cl atoms or interstitial clusters.

Ion‐Bombardment Etching of Synthetic Fibers. II

Franklin R. Anderson

J. Appl. Phys. 34, 2371 (1963); http://dx.doi.org/10.1063/1.1702748 (3 pages) | Cited 4 times

Online Publication Date: 9 June 2004

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Ion‐bombardment etching of synthetic polymers is shown to result in an actual preferential removal of material in a manner similar to that producing the etch on natural polymers and on inorganic materials and metals. It is also shown that heat has little effect on the over‐all etch pattern produced. In addition evidence is given relating the structures revealed by ion‐bombardment etching and the low‐angle x‐ray periods which have been reported in the literature for polyethylene.

Determination of Néel Temperatures in fcc Iron

U. Gonser, C. J. Meechan, A. H. Muir, and H. Wiedersich

J. Appl. Phys. 34, 2373 (1963); http://dx.doi.org/10.1063/1.1702749 (6 pages) | Cited 129 times

Online Publication Date: 9 June 2004

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The Néel temperatures of 304 stainless steel and γ‐Fe precipitates stabilized in the copper lattice have been determined by making use of the Mössbauer effect. The Néel temperature for the stainless steel is 38°±2°K and for two different sizes of γ‐Fe precipitates, the Néel temperatures are 55°±3°K and 67°±2°K. The measured Néel temperatures are compared with previous determinations by other methods and the variation of the Néel temperature of precipitates in the Cu—Fe system is discussed. Estimates are made of the magnetic field at the iron nucleus for each case.

Electron Scattering at Small Angles by Carbon

N. H. Sarkar

J. Appl. Phys. 34, 2379 (1963); http://dx.doi.org/10.1063/1.1702750 (4 pages) | Cited 7 times

Online Publication Date: 9 June 2004

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The differential and total elastic and inelastic scattering cross sections of the carbon atom have been estimated theoretically with a more realistic charge distribution for the electrons in the K and L shells. The agreement of the several experimental results with the present theoretical calculation is much better than with the existing theories of Lenz and Leisegang. For scattering by polystyrene latex particles, addition of the contribution of the hydrogen atoms in these particles results in an improvement of the agreement between theory and experiment.

Infrared Spectra of Polyethylene Crystals

R. G. Brown

J. Appl. Phys. 34, 2382 (1963); http://dx.doi.org/10.1063/1.1702751 (6 pages) | Cited 6 times

Online Publication Date: 9 June 2004

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The infrared absorption spectrum of polyethylene crystals grown from solution was investigated. Intensities of bands, attributed to defects, in the region 1250–1400 cm−1 were observed to change with heat treatment, first decreasing and then increasing as the temperature of the treatment was increased in the range 120°–135°C. This observation is interpreted in terms of reduction of the number of folds accompanied by introduction of a different type of defect. The doublet at 720–731 cm−1 was monitored during the process of refolding at T≈130°C. A vestige of the high‐frequency component was observed at all times, indicating the persistence of space‐group symmetry. The suggestion of morphological similarity of polyethylene crystallized from solution and from the melt is supported by the similarity of their spectra. Two new weak bands at 692 and 1243 cm−1 were observed in the spectra of specimens cooled with liquid nitrogen. The frequency 1243 cm−1 is nearly equal to that predicted for a CH2 twisting mode which is inactive under selection rules for an isolated molecule.
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