bluuebunny/crossref_metadata_2025 huggingface dataset:
Characteristics of p-i-n Junctions Produced by Ion-Drift Techniques in Silicon
Authors: Mayer J. W.
Published: April 2005

p-i-n junctions were fabricated by ion-drift techniques using lithium in p-type silicon. Highly compensated intrinsic regions from 0.1 to 5.0 mm were obtained. At temperatures between 120° and 200°C, the space charge of thermally generated carriers in the intrinsic region distorted the lithium ion distribution, producing linear graded junctions whose gradients were between 1011 and 1014 atoms/cm3/cm. Room-temperature capacitance measurements were used to determine the impurity distribution. Agreement was found between calculated and measured values of the impurity gradient. Precipitation of lithium ions in the intrinsic region was not observed.

The increase of the direct current under reverse junction potential as a function of the increased width of the depletion region permitted measurement of the diffusion and depletion-region-generated current components. The value of the diffusion current component at any temperature was proportional to the resistivity of the p-type silicon. The depletion-region-generated component was proportional to the width of the depletion region.
A Radiographic Study of Shock-Loaded Iron
Authors: Balchan A. S.
Published: April 2005

A study of shock-loaded Armco iron has been made using a flash radiographic technique. Oblique shock waves were produced in iron samples by the collision of an explosively loaded driver. Details in the radiograph were compared qualitatively with the shock configuration to be expected from the Hugoniot curve of iron. The double shock structure of iron and the rarefaction shock were observed.
Field Emission in Rutile Diodes
Authors: Wagner O. E. , Happ W. W.
Published: April 2005

Tunnel field emission is here proposed as a model for rectification in rutile diodes. This model has been previously applied by Mead [C. A. Mead, J. Appl. Phys. 23, 646 (1961)] to rectification phenomena observed with tantalum and aluminum oxides. In the case of rutile diodes it was found that the forward characteristics were explained by the tunnel field emission mechanism.
High-Field Superconducting Properties of Ti-Mo Alloys
Authors: Hake R. R. , Leslie D. H.
Published: April 2005

Critical current densities Jc for restoration of detectable resistance have been measured for super-conducting Ti-Mo alloys at 1.2°K in steady magnetic fields up to 30 kG, and for approximate Mo concentrations of 6, 9, and 16 at. %. Cold-rolling is observed to increase the Jc values considerably and, in the case of Ti-16 at. % Mo, to result in a marked ``anisotropy'' of Jc similar to that observed in many other cold-rolled alloy superconductors: at high fields Jc is essentially a maximum or minimum when the applied transverse magnetic field (H⊥J) is, respectively, parallel or perpendicular to the rolling plane, apparently independent of specimen geometry. This suggests that Jc is very sensitive to the relative orientation of the field and an anisotropic defect structure normally introduced during cold-rolling. The Jc anisotropy does not appear to be critically dependent upon the angle between the current and the rolling direction for current directions in the rolling plane and can apparently be suppressed by martensitic transformation during cold-rolling. Although an explanation of Jc anisotropy in cold-worked alloys does not fall within the scope of homogeneous alloy-negative surface energy theories, the ``upper'' resistive critical fields [Hr(J=1A/cm2)] for these alloys, ranging from 26.5 to 64 kG, are in fair agreement with predictions of the Ginzburg-Landau-Gor'kov-Abrikosov theory.
Morphological Stability of a Particle Growing by Diffusion or Heat Flow
Authors: Mullins W. W. , Sekerka R. F.
Published: April 2005

The stability of the shape of a spherical particle undergoing diffusion-controlled growth into an initially uniformly supersaturated matrix is studied by supposing an expansion, into spherical harmonics, of an infinitesimal deviation of the particle from sphericity and then calculating the time dependence of the coefficients of the expansion. It is assumed that the pertinent concentration field obeys Laplace's equation, an assumption whose conditions of validity are discussed in detail and are often satisfied in practice. A dispersion law is found for the rate of change of the amplitude of the various harmonics. It is shown that the sphere is stable below and unstable above a certain radius Rc, which is just seven times the critical radius of nucleation theory; analogous conclusions are obtained for the solidification problem. The results for the sphere are used to discuss the stability of nonspherical growth forms.
Elastic-Plastic Properties of Iron
Authors: Taylor John W. , Rice Melvin H.
Published: April 2005

Smooth bore cannons were used to produce plane collisions between plates of Armco iron. Projectile velocities ranged from 60 to 400 m/sec. Time resolved measurements of the target free-surface velocities indicate that the dynamic yielding process is time dependent on a submicrosecond time scale. The shape of the Hugoniot curve in the pressure-volume plane up to 80 kbars shows that true hydrostatic equilibrium has not yet been established behind the elastic wave. On the other hand the substantially constant free-surface velocities behind the plastic front indicate that the material cannot be far from equilibrium after a short time. Some data on the rarefaction sound speed in the high pressure region are interpreted to imply a value very near 6 km/sec.
Development of Substructure in Polycrystalline Aluminum During Constant-Strain Fatigue
Authors: Grosskreutz J. C.
Published: April 2005

Transmission electron microscopy and microbeam x-ray techniques were used to study the substructure developed in pure, polycrystalline aluminum during constant strain fatigue. A complete study was made at strain amplitude ±0.002 over the cycle range 0–100 000 cycles. During the first several thousand cycles, the substructure varies considerably from grain to grain, depending on orientation. In general, dislocations initially cluster along {111} glide planes during the first few hundred cycles. By 2000–3000 cycles subgrain boundaries have formed along {111}, {100}, and {110} planes. Large numbers of dislocation loops are seen in and near the boundaries. As cycling proceeds to fracture, the dislocation density in these boundaries and the misorientation between the subgrains increases. The average subgrain volume decreases from ∼25 μ3 at 5000 cycles to ∼8 μ3 at 100 000 cycles. Subgrains were formed at all strain levels which were investigated, the lowest being ±0.0005; however, the rate of formation decreases rapidly as the strain is lowered. A model of fatigue hardening is proposed based on these observations, and the relation to fatigue fracture is discussed briefly.
Growth of Ferrous-Free Cobalt Ferrite Single Crystals
Authors: Ferretti A. , Kunnmann W. , Wold A.
Published: April 2005

Single crystals of cobalt ferrite were grown from a melt having the composition 95% CoFe2O4−5% NaFeO2 by weight, under an oxygen pressure of 1650 psig and a temperature of 1590°C. Chemical analysis indicated that the crystals contained no Fe2+ and 3 parts per 10 000 sodium.
Reverse-Bias-Dependence of Spectral Photoresponse of Si and GaAs Shallow p-n Junctions Near the Band Edge
Authors: Loh Eugene
Published: April 2005

The spectral photoresponse of Si and GaAs photodiodes near the band edge has been measured with reverse bias up to nearly 100 V at room temperature. The measurement shows that the reverse voltage V raises the photoresponse ΔI, especially in the long-wavelength region, and hence also shifts the spectrum toward longer wavelength. At a fixed wavelength, ΔI is proportional to Vn, where, n decreases as the photon energy increases. For the step-type Si junction, n ranges from ⅕ to ½ as the photon energy changes from 1.6 (α−1=10 μ) to 1.15 eV (α−1=1000 μ); this voltage dependence may mainly result from the widening of the junction depletion-layer by the reverse bias. For GaAs photodiodes, the exponent n changes from ⅙ to 1.3 as the photon energy varies from 1.44 (α−1=1.6 μ) to 1.36 eV (α−1=1000 μ). The strong voltage-dependence of the photoresponse of a GaAs junction, which behaves like a p-i-n junction electrically, in the long wavelength region may result from the photoexcitation of electrons or holes to shallow levels in the pseudointrinsic region followed by some strongly field-dependent ionization process, such as tunneling, etc.
Characteristics of Dislocation Stress Fields Due to Elastic Anisotropy
Authors: Chou Y. T.
Published: April 2005

In the solution of certain dislocation stress fields based on anisotropic elasticity, it is found that for −3>C>−4, where C is an anisotropic factor of the crystal, the σxx field of an edge dislocation is divided into six symmetric sectors of alternating tension and compression, in contrast to the usual case of half plane of tension and half plane of compression (C≥−3). The parameter C also characterizes the σxy field. For C≥−2.5, there is a relative maximum on the x axis as in the isotropic case. When −2.5>C>−4, the maximum changes to a relative minimum. The σyy field is identical to σxy field after a 90° rotation, and thus behaves similarly. Several consequences from these findings are discussed and examples are given.
Influence of Ion Reflection Probability on Potential Distribution in Low-Pressure Thermionic Converters
Authors: Mazur P.
Published: April 2005

Some numerical results are presented as an example to show how, for certain boundary conditions, the voltage—current characteristic in low-pressure large-spaced gas diodes may give the appearance of saturating at a value of output current which is less than the saturated electron current from the emitter. The crucial parameter introduced which is mainly responsible for the phenomenon is f, defined as the probability that a returning ion reflects again as an ion after colliding with the emitter.
Coupling of Electromagnetic and Magnetostatic Modes in Ferrite-Loaded Cavity Resonators
Authors: Auld B. A.
Published: April 2005

A formalism is developed for treating the coupling of electromagnetic and magnetostatic modes in ferrite-loaded cavity resonators. Coupled-field equations are obtained by separating the magnetic field into rotational and irrotational parts. The fields are then expanded in terms of electromagnetic modes and magnetostatic modes, leading to coupled equations for the mode amplitudes. From these equations, one may evaluate the detuning and mode splitting resulting from the interaction of the ferrite with the cavity fields. In this treatment, there is no limitation as to the size of the ferrite sample, and the effects of wall proximity and the dielectric properties of the ferrite are specifically included.
Minority Carrier Thermoelectric Cooling
Authors: Bullis W. Murray
Published: April 2005

The fallacy in a recently proposed theory of minority carrier cooling is pointed out. The correct approach is given and the current literature on the subject is summarized. It is emphasized that cooling devices utilizing minority carrier effects are normally less efficient than conventional thermocouple modules.
Probe Noise in Different Regions of a Gas Discharge
Authors: Hanson D. G. , Van Der Ziel A.
Published: April 2005

Noise flowing to shielded probes in neon gas discharges is measured in the various regions of the discharge between 0.55 and 30 Mc under floating probe conditions. There is a low-frequency noise mechanism that is most pronounced in the negative glow region, a high-frequency noise mechanism that is most pronounced in the positive column but absent in the negative glow region, and a shot noise mechanism that predominates around 4 Mc. The shot noise under floating probe conditions gives a qualitative measure for the carrier density distribution in the discharge. The equivalent noise temperature can be smaller than the electron temperature; in the negative glow region this is caused by the space-charge suppression of the ion shot noise, but in the positive column the low noise temperature of the high-frequency noise mechanism is also an important factor. The high-frequency noise temperature is much smaller than for unshielded probes.
Linewidth and Temperature Shift of the R Lines in Ruby
Authors: McCumber D. E. , Sturge M. D.
Published: April 2005

Improved experimental data have been obtained between 20° and 350°K for the widths and temperature shifts of the R lines in ruby. Above 77°K the results can be accurately described in terms of Raman scattering of Debye-model phonons. There is no evidence for measurable contributions to the widths and shifts from direct processes involving emission or absorption of a single resonant phonon. Below 77°K the principal contributions are from crystal inhomogeneities.
Efficiency Calculations of Thermoelectric Generators with Temperature Varying Parameters
Authors: Cohen R. W. , Abeles B.
Published: April 2005

A simple analytic expression for the efficiency of a thermoelectric power generator with temperature varying parameters is obtained in terms of temperature averages of these parameters. The expression is derived assuming that the Thomson effect may be treated as a small perturbation on the heat flow in the generator. The assumption is also made that half the Thomson heat generated (absorbed) in the generator flows to (from) the hot junction and the other half flows to (from) the cold junction. Using this method, the performances of three hypothetical generators are calculated and found to be in excellent agreement with exact machine calculations.
Ferrimagnetic Resonance Linewidth in Dense Polycrystalline Ferrites
Authors: Seiden P. E. , Grunberg J. G.
Published: April 2005

The linewidth of polycrystalline ferrites has been calculated from the dipole narrowing theory including both anisotropy and porosity effects. It is shown that porosity broadening is successfully accounted for and that porosity is the dominant line broadener even in very dense ferrites. The temperature dependence of the linewidth for samples of yttrium iron garnet and manganese ferrite are in good agreement with the predictions of the theory.
Energy Density Distribution in a Polished Cylinder of Laser Material
Authors: Sooy W. R. , Stitch M. L.
Published: April 2005

A calculation of the flux distribution inside a smooth-walled laser cylinder is made for two limiting assumptions about the nature of the incident pumping flux. The idealized case of a line source at one focus of an elliptical reflector producing a convergent cylindrical wavefront at the other focus leads in the expected way to a singularity at the center of the crystal, and for sufficiently large values of the product of the doping concentration and diameter, the flux density goes through a minimum before increasing. This corresponds to the relatively rare physical situation in which the laser crystal is much larger than the pump source and both are very small compared to the reflector.

A much more realistic assumption of isotropic flux distribution cannot be integrated in closed form and required a machine calculation. This reveals that the distribution is strongly dependent on doping, and that for light doping the flux density in the central region is approximately three-fold higher than in the peripheral regions. This is used as a hypothesis to explain low observed laser efficiencies by postulating that for typical operation the central region is undergoing laser action while the more voluminous peripheral region is absorbing pump energy and converting it to fluorescence. Some experimental evidence to support this hypothesis is obtained by measurements of the inversion, averaged over the whole crystal, by means of absorptivity measurements. It has been shown that laser action commences while the crystal is still, on the average, absorbing.
High-Temperature Steady-State Creep Rate in Single-Crystal MgO
Authors: Cummerow R. L.
Published: April 2005

Steady-state, three-point bending deflection rate measurements on single-crystal MgO samples in the temperature range of 1450°–1700°C show that creep is a thermally activated process without an unique activation energy. The measured energies range from 3.5 to about 7 eV. This range of energies can be explained in terms of self-diffusion data if it is assumed that the creep rate is limited by self-diffusion. Small deviations from stoichiometry are shown to be very important in controlling the creep rate as they are in all ionic or electron transport processes. Understanding and control of these deviations are necessary to obtain a quantitative understanding of either steady-state creep or diffusion.

The variation of creep rate with stress can be described by a power law with an exponent varying from 4 to 7. This range of exponent lends some support to the theory based on edge dislocation climb over barriers as the rate limiting step. On the other hand, such barriers have not been observed in single crystals of MgO and other substances, so that some other mechanism in which diffusion is rate limiting may be operating.

The creep rate is apparently independent of subgrain structure, precipitates observed at room temperature, surface roughness, spectroscopically determined impurity content, the valence state of the iron impurity, and dislocation strain pattern after bending.
Niobium-Thorium Eutectic Alloy as a High-Field, High-Current Superconductor
Authors: Cline H. E. , Rose R. M. , Wulff J.
Published: April 2005

Niobium-thorium eutectic alloys having fine acicular microstructures were produced by fast cooling from a vacuum melt. Although the solidified material was normal, continuity between the superconducting niobium-rich phase, which was essentially pure niobium, was attained by plastic deformation at room temperature. The resulting wire was tested for critical current at 4.2°K, in transverse magnetic fields up to 82.5 kG; at the highest field, critical current densities of slightly more than 104 A per square centimeter were observed. The critical current density was independent of applied field from 20 kG to the highest field used; the level of critical current density depended on diameter in a manner which suggested dependence on cold work. It was concluded that the cold work had reduced the thickness of the needles of niobium below the superconducting penetration depth, and had brought them sufficiently close together to allow the superconducting correlation to interconnect the niobium, in the manner suggested by Cooper; furthermore, the constant critical current region may possibly extend to considerably higher fields.
Structure of Subdivided Bloch Walls
Authors: Bhide V. G. , Shenoy G. K.
Published: April 2005

The subdivision of Bloch walls into periodic right- and left-handed Bloch segments observed by Williams and Goertz, by DeBlois and Graham, and recently by Harrington is shown to be caused by screw rotation of the spin; not only along the width of the wall, but also along the length of the wall with different periodicity. The width of the wall and the distance between the right-handed and left-handed segments are determined by an approximate minimization of the total energy of the wall which is composed of exchange, anisotropy, and magnetostatic energies. These values agree well with the experimental results. The spin structure of this complex wall gives rise, out of itself, to right- and left-handed Bloch segments and the positive and negative Néel segments. The zig-zagging of the wall under externally applied field, observed by DeBlois and Graham, is also explained.
Oxygen Outgassing Caused by Electron Bombardment of Glass
Authors: Lineweaver Jack L.
Published: April 2005

A system employing a mass spectrometer as a continuous flow gauge has been used to study the oxygen evolved from aluminum-coated glass as a result of electron bombardment. The outgassing from most glasses is found to fit the empirical equation Q=Q∞(1-exp-t/K). In this equation Q is the sum of the oxygen released during the bombardment time t and that evolved during a subsequent thermal outgas and Q∞ is the maximum amount of oxygen expected from a sample bombarded for long times. Experimental results from Code 8603 glass indicate that Q∞ is a measure of the range of 10- to 27-keV electrons in glass, K varies inversely with electron current per unit mass of glass affected, and that electron current density may have a secondary effect on electron range in bulk glass. Oxygen outgassing data are presented from 12 commercial glasses subjected to 150 μA of 20-keV electrons bombarding a 3-×¾-in. area. A mechanism of oxygen release is proposed which involves the dissipation of electron energy, the charge produced in the glass by the electrons, and the availability of nonbridging oxygen atoms in the glass structure.
Theoretical Analysis of Plastic Deformation in Superlattices Based on the Body-Centered Cubic Structure
Authors: Marcinkowski M. J. , Fisher R. M.
Published: April 2005

A theoretical analysis has been made of the friction stress opposing the movement of both superlattice slip dislocations and twinning dislocations which arises from their interaction with antiphase domains in B2-, DO3-, and L21-type superlattices, all of which are based on the body-centered cubic structure. In the case of superlattice slip dislocations, this interaction results in the well-known maximum in yield stress at some critical antiphase domain size. Twinning dislocations, on the other hand, require stress levels about twenty times greater than the maximum value calculated for superlattice dislocations; however, this friction stress decreases for domains smaller than the critical size. In both DO2- and L21-type superlattices, second nearest neighbor as well as first nearest-neighbor ordering energies are found to play an important role in the resistance to dislocation motion. These results agree well with the limited number of experimental observations obtained by other investigators with the Fe3Al superlattices.
Vibration of Sphere for Determining the Dilatational Constants of Viscoelastic Materials
Authors: Lee Tung-Ming
Published: April 2005

The forced vibration problem of a finite sphere with an exciting source embedded inside it has been treated. The source is assumed to oscillate sinusoidally and the complex dilatational modulus is used to describe the motion inside the sphere. It is found that if the outer surface of the sphere is restrained from radial displacement, the ratio of the amplitude of a midpoint (between the outer surface of the sphere and the inner exciting source) to the amplitude of a point on the exciting source could be used as an indication of the dilatational properties of the sphere. Therefore, from the criterion of maximum amplitude ratio in conjunction with the frequency, the dilatational properties of a testing material can be determined. This method can be applied to viscoelastic fluids as well as solids.
Influence of Preferred Orientation on the Hall Effect in Titanium
Authors: Roesch Louis , Willens R. H.
Published: April 2005

The effect of preferred orientation on the Hall effect in titanium was examined in an attempt to resolve the inconsistent results of previous investigators. Three specimens of iodide titanium were prepared with different textures and the Hall coefficient of each was measured between 4.2° and 295°K. The Hall coefficient was found to depend on both temperature and preferred orientation. At room temperature, it was determined to be −1.8×10−11m3/C in two specimens and +1.2×10−11m3/C in a third one. From the x-ray analysis of the texture and the Hall coefficient data, it was concluded that the positive component of the Hall coefficient was associated with the hexagonal axis of titanium, being parallel to the magnetic field. An approximate calculation estimated the principal components of the Hall tensor to be R∥ = +4.2×10−11 and R⊥ = −7.7×10m3/C, where R∥ is the Hall coefficient when the magnetic field is parallel to the c axis and R⊥ the Hall coefficient when the magnetic field is perpendicular to the c axis. The values of R∥ and R⊥ given above can account for the spectrum of previously published Hall values for titanium.
Grown-In Dislocations in Calcium Tungstate Crystals Pulled from the Melt
Authors: Chaudhuri A. R. , Phaneuf L. E.
Published: April 2005

Etch pits on (001) surfaces of calcium tungstate crystals, formed on treatment with hot dilute solutions of hydrochloric acid, were identified to be dislocation etch pits. The technique is able to follow the motion of dislocations during annealing by the formation of new sharp-bottomed pits adjacent to flat-bottomed pits at the initial dislocation positions. Inclusions, both solid and gaseous, are an important source of dislocations in crystals of calcium tungstate grown from the melt.
Formation of Point Defects during Plastic Deformation and Their Subsequent Annealing Behavior
Authors: Birnbaum Howard K.
Published: April 2005

The formation of point defects during plastic deformation and their subsequent interactions with dislocations in high-purity copper was studied using a low-temperature strain-aging technique. The point-defect-dislocation interaction gave rise to a small yield point whose magnitude depended on the temperature and time of aging after deformation. The annealing kinetics indicated that two types of point defects were formed by deformation in concentrations which depended on the prestrain and prior history of the specimen. A mechanism for the point-defect annealing was proposed to account for the experimental results and was used to calculate the diffusion-activation energy of the defects in the lattice and along the dislocations. Based on this mechanism, the defects were tentatively identified as the interstitial and the divacancy. The temperature dependence of the yield point was examined and was shown to be consistent with an elastic interaction due to the dilatation around the point defects. The results indicated that the point defects retained their identity on arrival at the dislocation rather than becoming incorporated into the dislocation structure.
A Microwave Method for the Study of Steady and Fluctuating Plasma Number Densities
Authors: Crawford F. W. , Kino G. S. , Self S. A. , Spalter J.
Published: April 2005

A method for the measurement of dc and ac components of number density in cylindrical gas-discharge columns has been studied. The technique is based on a dipole resonance, occurring below the electron plasma frequency. It is excited by an rf signal transmitted along a stripline enclosing the plasma column. By working on the side of the resonance curve, a fluctuating output signal is obtained corresponding to the density fluctuations. The simple theory of the resonance has been extended to take account of stripline size, of the glass surrounding the column, and of a radial variation in number density. The method is considerably more sensitive than cavity perturbation techniques, and the results compare reasonably well with number density measurements made by other methods.
Some Measurements of Steady and Fluctuating Plasma Number Densities
Authors: Crawford F. W. , Kino G. S. , Self S. A. , Spalter J.
Published: April 2005

Observations of dc and ac components of electron number density have been made along the positive columns of hot-cathode, mercury-vapor discharges, at a pressure of about 1 μ Hg. Direct measurements were made by a microwave method involving a dipole resonance of the column, while indirect measurements were made from the accompanying light output and, in the case of fluctuating components, by capacitive pickups sliding on the outside of the tube. The frequency spectra of number density, light output, and potential fluctuations generated by the tube itself were found to be similar, and their variations in amplitude along the column were found to be closely related. For injected ac signals of variable frequency, phase and amplitude variations in the number density are shown to agree closely with the theoretical predictions of Crawford. Unsuccessful attempts were made to excite low-frequency fluctuations by injecting electrons into the positive column from an auxiliary cathode.
Some Preliminary Results on Defects in Irradiated UO2 Single Crystals as Revealed by Transmission Electron Microscopy
Authors: Blank H. , Amelinckx S.
Published: April 2005

Vapor-grown single crystals of nearly stoichiometric UO2 have been thinned for transmission electron microscopy. The as-grown crystals show a dense pattern of precipitates and may contain loops due to quenched-in vacancies but contain hardly any dislocations. Two models for the production of loops are proposed. Dislocation networks (small angle boundaries) are produced on annealing the crystals. Irregular patterns of dislocations arise when sufficient thick parts of the crystal foils are treated with heat shocks in the microscope suddenly increasing the beam current. After exposure to 1015 nvt the crystal foils show fission tracks, short segments of straight dislocation lines and black dots, which are partly distributed at random and partly are aligned on fission tracks. Interaction between fission tracks and dislocations has been observed. The conditions for contrast production on fission tracks have been investigated. The experimental findings can be explained by a model of a displacement field around the fission tracks.
Galvano-Thermomagnetic Phenomena. IV. Application to Anisotropic Adiabatic Nernst Generators
Authors: Harman T. C. , Honig J. M. , Tarmy B. M.
Published: April 2005

Tensor components have been derived for the matrix relating entropy flux and gradient of electrochemical potential to gradient of temperature and electrical current. The entries have been specified in terms of six basic galvano-thermomagnetic transport coefficients; the Casimir—Onsager reciprocity conditions have been utilized to reduce the number of independent coefficients. These relationships have also been employed to extend the Bridgman—Heurlinger identities to anisotropic materials. Using these equations along with the phenomenological relations, the characteristics for galvano-thermomagnetic Nernst generators operating under adiabatic conditions have been formulated. The results are compared with the equations which are valid for the isothermal case.
Theory of Galvano-Thermomagnetic Energy Conversion Devices. V. Devices Constructed from Anisotropic Materials
Authors: Harman T. C. , Honig J. M. , Tarmy B. M.
Published: April 2005

Operating characteristics of galvano-thermomagnetic generators and refrigerators for any anisotropic material are summarized in tabular form for both the longitudinal (thermoelectric) and transverse (Nernst) devices and for isothermal and adiabatic operating conditions. In the most general case, device performance is governed not only by the figure of merit, but also by an anisotropy factor. This factor involves off-diagonal elements of the Nernst and Seebeck tensors for Nernst devices and diagonal elements of the Nernst and Seebeck tensors for thermoelectric devices. It is believed that the ``Umkehr'' effect (such as observed in Bi) is due to a nonvanishing diagonal component of the Nernst tensor.
Electrical Size Effect in Aluminum
Authors: Fo/rsvoll K. , Holwech I.
Published: April 2005

The effect of specimen size on the residual electrical resistivity has been measured for six types of superpurity aluminum. The specimens were strips with thicknesses between 1.5 and 0.01 mm. The results are compared with Fuchs' theory for the resistance of thin films. The measurements on the four purest materials gave good agreement with theoretical curves, but the variations in the constant ρ·l (bulk resistivity times bulk mean free path) were much larger than expected from the experimental error. The measurements on the two least pure materials could not be fitted to a theoretical curve, although the individual points are reproducible.
Pumping Effects Contributing to the Excitation of Phonon Instabilities in Ferromagnetic Insulators
Authors: Auld B. A. , Tokheim R. E. , Winslow D. K.
Published: April 2005

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.
Structural Properties of Cleaved Silicon and Germanium Surfaces
Authors: Lander J. J. , Gobeli G. W. , Morrison J.
Published: April 2005

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.
Effect of Hydrostatic Pressures on the Crystallization Kinetics of Natural Rubber
Authors: Martin Gordon M. , Mandelkern Leo
Published: April 2005

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.
Multiple Charge Exchange of an Accelerated Positive-Ion Beam in a Neutral Gas
Authors: Parzen P.
Published: April 2005

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.
Theory of Pulse Propagation in a Laser Amplifier
Authors: Frantz Lee M. , Nodvik John S.
Published: April 2005

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.
Radio-Frequency Vibrations of Rectangular AT-Cut Quartz Plates
Authors: Koga Issac
Published: April 2005

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.
Ion-Bombardment Etching of Synthetic Fibers. II
Authors: Anderson Franklin R.
Published: April 2005

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.
Crystallinity and Electronic Properties of Evaporated CdS Films
Authors: Dresner J. , Shallcross F. V.
Published: April 2005

The effect of several processing methods on the crystallinity and electronic properties of evaporated CdS films has been investigated. Diffusion of Cu or Ag at temperatures above 450°C has yielded films composed of crystals of controllable size ranging from 10−5 to 1 cm in diameter. The electron mobility depends strongly on the reorientation of the crystallites but is only slightly affected by their size. The best films obtained have shown mobilities for photogenerated carriers of 300 cm2V−1 sec−1, characteristic of the bulk crystal. Typical values of the total trap density are in the range of 1019 to 1021 cm−3, compared to 1014 to 1016 in single crystals. The resistivity of the high mobility films can be controlled by the addition of Cl or Ga at the proper stage of the processing.

In the photoconductive films, the mobility may vary with the illumination level by an order of magnitude. In films processed at temperatures above 400°C, a model of conducting crystallites separated by thin insulating barriers is insufficient account for the observed results.
Ion Bombardment of Silicon in a Glow Discharge
Authors: Strack Hans
Published: April 2005

Silicon was bombarded with low-energy ions in a dc glow discharge and simultaneously doped with phosphorus and boron. A simple theory describes the diffusion of substitutional elements in silicon influenced by ion bombardment. The distribution profile of phosphorus in 200Ω-cm p-type silicon at a bombardment temperature of 820°C can be explained by assuming a diffusion coefficient of the form D(x)=3.6 exp(−x/L)×[μ2/h], with L = 0.3 μ and x the distance from the instantaneous surface. L is interpreted as the diffusion length of excess vacancies created by the bombardment. The diffusion coefficient at the surface is higher by a factor of 105 than the one found in thermally activated diffusions.
A Phenomenological Theory of Spherulitic Crystallization
Authors: Keith H. D. , Padden F. J.
Published: April 2005

To account for spherulitic crystallization from the melt, one must explain the origins (i) of fibrous crystal habits in the absence of appreciable temperature gradients and (ii) of profuse noncrystallographic branching. Attention is drawn to properties held in common by spherulite-forming melts of various types and, in particular, to the facts that (a) they are multicomponent systems, (b) they exhibit small coefficients of self-diffusion, and (c) they crystallize slowly. It is shown that a consequence of these properties is that a plane crystal face cannot grow without suffering an instability of profile. Analagous instabilities lead in metal crystals to a cellular interface but, because of unusual growth kinetics, instability in spherulite-forming melts gives rise to a drastic modification of crystal habit. Bundles of discrete fibers are formed whose widths are determined by δ = D/G, D being the coefficient of self-diffusion and G being the growth rate. δ is generally small in these systems and commensurate with the scale of crystalline disorder in the fibers. It is this circumstance that allows noncrystallographic branching to occur.
First-Order Transition Temperatures in Crystalline Polymers
Authors: Eby R. K.
Published: April 2005

The concept of lamellar, crystalline polymers with molecular ends and comonomer components included in the crystal lattice as defects has been used to derive a relationship between first-order transition temperature, comonomer content, molecular weight, and lamellar thickness. The relationship is reduced to equations for three special cases, which describe the variation of transition temperature with comonomer content, molecular weight, and lamellar thickness, respectively. These equations have the same functional relationship as those obtained previously using the concept of perfect (homopolymer) crystals from which molecular ends and comonomers are excluded. Additionally, if certain constant terms have the appropriate values, the present equations are identical with the earlier ones. These constants measure the difference between the defect regions and the perfect lattice. The constants imply that the transition temperature should vary with the type of comonomer of molecular end as well as with the comonomer content or molecular weight.
Full-Plane Threshold Energies for Cathode Sputtering of Metals with Ar+ Ions
Authors: Henschke Erich B. , Derby Samuel E.
Published: April 2005

Full-plane threshold energies at normal ion incidence of Ar+ ions have been determined for sixteen metals with a method of ``detection of deposits,'' using demountable sputtering tubes of different designs. Since in each case the target, immersed like a Langmuir probe in a high-density plasma, was bombarded by singly charged ions with a high ion current density under background conditions similar to those in Hg+-ion sputtering tubes used for the determination of thresholds, the threshold data obtained for Ar+-ion bombardment are comparable to those formerly published for sputtering with Hg+ ions. This comparison discloses that threshold predictions for Ar+ ions, formerly made by simply exchanging the mass of the Ar+ ion for the mass of the Hg+ ion in a threshold formula, are not correct at all. This result also implies that threshold formulas in which the interaction between the target atom and the impinging ion is only expressed by a mass factor containing the masses of the target atom and of the ion are not adequate to cover simultaneously the thresholds for different kinds of ions. The threshold data can be represented by a calculable factor f′. Applying the simplified threshold formula of the authors' theory of cathode sputtering to the thresholds measured with Ar+ ions, another representation of the data is possible by the dissipation factors δAr+ which are different from those for sputtering of the same metals with Hg+ ions, indicating that the energy loss due to Debye waves during sputtering is different for different bombarding ions. The thresholds for Ar+-ion sputtering are, in general, lower than those for Hg+-ion bombardment; however, they obey the same law of periodicity seen in a plot vs atomic number, as formerly established by the author for sputtering with Hg+ ions.
Spontaneous Polarization Noise in Polar Dielectrics
Authors: Davis Leo
Published: April 2005

The spontaneous fluctuations of polarization in polar dielectrics are considered by using the Einstein thermodynamic method, a general dielectric theory method, and an equivalent circuit method. Mean-square fluctuation of the polarization field is obtained by the first two methods and the frequency spectrum by use of the dispersion properties. The equivalent circuit method gives frequency spectra directly and the two lines of analysis are shown to give consistent results. Noise magnitudes are exhibited and noise is shown to be a consequence of dielectric dispersion in all matter.
Mechanism of High-Power-Density Electron Beam Penetration in Metal
Authors: Schwarz Helmut
Published: April 2005

Electron beams of approximately 2 kW power and acceleration voltages in the range about 100 kV are focused on metal surfaces in spots of 15 to 250 μ so that maximum power densities of more than 1013 W/m2 can be achieved.

Such electrons penetrate several orders of magnitude deeper into the solid or liquid materials than the classical penetration depth of 100 keV electrons would allow for. A high-speed movie (2500 frames per second) of the process shows that the surface is closed by a liquid film most of the time and that it only ruptures during very short intervals. The temperatures at the surface and in the interior of the welds have been determined during the process, experimentally and theoretically, respectively. Also, the dislocation of the metal within the weld has been studied with an electron-probe x-ray microanalyzer and with radio-active tracing. Measurements of mass density show that it decreases after the material has been affected by the electron beam.

In the discussion, a tentative explanation of the effect is offered.
Preliminary Investigation of the Two-Photon Photoelectric Effect
Authors: Bloch Peter
Published: April 2005

The photoelectric current due to the absorption of two photons has been calculated. Its magnitude is dependent upon the square of the incident radiation intensity, whereas, for the photoelectric effect due to the absorption of one photon, the magnitude of the current is linearly dependent upon the intensity.

The magnitude of the photoelectric current due to the absorption of two photons is small. However, under intense radiation, such as is obtainable from a ruby laser, a photoelectric current due to two-photon absorption should be observed.
Stopping by Elastic Collisions of Particles from a Unidirectional Plane Source
Authors: Baroody E. M.
Published: April 2005

Calculations are made of certain averages for particles from a plane, unidirectional source being slowed down by elastic collisions in an infinite medium of randomly located target atoms. Calculations are based on the moments form of the Boltzmann transport equation and follow procedures frequently used in the theory of neutron moderation. Assuming isotropic scattering in center-of-mass coordinates, averages are determined for powers of the distance from the source and for Legendre polynomials which give information on the direction of motion. When the mean free path varies as a power of the energy a number of averages are determined at all energies for equal masses of fast particles and target atoms, and for the first collision interval for unequal masses. Expressions for spatial averages at zero energy are obtained by taking the Laplace transform of the moments equation. For equal masses and λ proportional to Ek, it is verified that the distribution of stopped particles at moderately deep penetrations is of the form zp exp[-z/λ(E0)]. For k>1, p is approximately 2/(2k+1). A few comparisons are made with moments calculated by other methods and comments are included on the place of such calculations in the theory of the stopping of kilovolt ions. An appendix reports some preliminary results for anisotropic scattering.