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1 Apr 1974

Volume 45, Issue 4, pp. 1487-1927

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Hydrostatics and steady dynamics of spatially varying electromechanical flow structures

Thomas B. Jones

J. Appl. Phys. 45, 1487 (1974); http://dx.doi.org/10.1063/1.1663448 (5 pages) | Cited 7 times

Online Publication Date: 6 October 2003

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The hydrostatic and steady laminar hydrodynamic equilibria of spatially varying electromechanical flow structures are investigated. Under certain conditions the relationship between the dielectric height of rise and the applied voltage is found to be double valued. It is found that one of the two equilibrium values is always unstable. This gives rise to the experimentally observed spontaneous rise of the fluid to the top of the structure, once a certain critical voltage is reached. Starting above this critical voltage with the structure completely filled and decreasing the applied voltage toward the critical value results in pinch‐in failure at an intermediate point along the structure and trapping of dielectric fluid at the top. The simple mathematical model developed predicts all these phenomena, without recourse to tedious point‐by‐point surface force equilibrium determination. Experiments are reported which verify the results for the hydrostatic case.

Incidence angle and polarization dependence of light diffracted by acoustic surface waves

A. Alippi, A. Palma, L. Palmieri, and G. Socino

J. Appl. Phys. 45, 1492 (1974); http://dx.doi.org/10.1063/1.1663449 (6 pages) | Cited 23 times

Online Publication Date: 6 October 2003

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A theoretical analysis of the diffracting effects produced by ASW on light beams contained on the sagittal plane of the wave is presented. The separate contributions have been explicitly studied, produced by periodical changes of the refractive index and by corrugation of the surface in cases of x‐ and y ‐cut crystalline quartz and y ‐cut LiNbO3 for both states of polarization of the incident light. In all cases analyzed, measurements of light‐deflection efficiency have been performed as a function of the angle of incidence in light‐transmission experiments.

Excess vacancy generation mechanism at phosphorus diffusion into silicon

Masayuki Yoshida, Eisuke Arai, Hiroaki Nakamura, and Yukio Terunuma

J. Appl. Phys. 45, 1498 (1974); http://dx.doi.org/10.1063/1.1663450 (9 pages) | Cited 42 times

Online Publication Date: 6 October 2003

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Phosphorus is diffused into silicon at 900 °C from a phosphorus‐doped silicon‐dioxide layer. Since a profile of phosphorus concentration is expressed by a function of x/math, where x is the distance from a surface and t the diffusion time, diffusion coefficients are determined by the Boltzmann‐Matano method. They are larger than the intrinsic diffusion coefficient and are dependent not only on the concentration (the concentration effect) but also on some unknown condition at a surface (the surface effect). The surface effect extends more than 20 μ deep into a bulk of silicon, and is stronger than the concentration effect. All of phosphorus atoms are located at substitutional sites. Diffusion‐induced dislocations are not found. A new mechanism for the generation of excess vacancies is suggested. The new mechanism consists of the following: (i) Phosphorus diffuses by a vacancy mechanism. The diffusion of phosphorus occurs only through the diffusion of E centers. (ii) When phosphorus atoms enter from a surface into a bulk, they should be in a form of E centers. Affected by a surface, a large amount of E centers is formed per unit time at a surface. (iii) The E centers flow into a bulk. (iv) By their dissociations, excess vacancies are generated. The surface effect and the emitter dip effect are attributed to excess vacancies.

Grain‐boundary diffusion and boundary widths in metals and ceramics

R. E. Mistler and R. L. Coble

J. Appl. Phys. 45, 1507 (1974); http://dx.doi.org/10.1063/1.1663451 (3 pages) | Cited 43 times

Online Publication Date: 6 October 2003

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A technique is presented to calculate grain‐boundary widths and grain‐boundary diffusion coefficients in metals and nonmetals using grain growth, sintering, diffusion and∕or creep data. High‐purity metals yield boundary widths of the order of a few atomic diameters, whereas ionic materials yield ``effective boundary widths'' orders‐of‐magnitude wider.

High‐power 2‐ to 6‐μm window material figures of merit with edge cooling and surface absorption included

M. Sparks and H. C. Chow

J. Appl. Phys. 45, 1510 (1974); http://dx.doi.org/10.1063/1.1663452 (8 pages) | Cited 7 times

Online Publication Date: 6 October 2003

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See Also: Erratum

Show Abstract
Values of the total power P that a window can transmit under specified conditions are calculated for use as figures of merit for window materials. New features of the figures of merit are consideration of edge as well as face cooling, treatment of surface as well as bulk absorption, use of P rather than intensity as the figure of merit, effects of improving materials, and calculation for 3.8 and 5.25 μm. New results include the following: For continuous operation, large‐diameter windows should be face cooled, but small‐diameter window may be edge cooled, and P often decreases as the diameter D increases. For pulsed operation, P increases as D increases, as was intuitively expected. Values of the diameter DEF, above which face cooling should be used, are surprisingly large, ranging between 7 and 100 cm, typically. For pulsed operation and for D > DEF in cw operation, P is independent of thermal conductivity K while for D < DEF in cw operation, P∝K. The alkaline‐earth fluorides have the greatest figures of merit for large‐diameter windows with P = 76 MW, ΔT = 50 K, and l=0.5 cm for a 1‐sec pulse on a 10‐cm‐diam window of BaF2 at 3.8 μm with a bulk absorption coefficient of 10−4 cm−1. For small‐diameter windows (1‐cm diameter), Si, BaF2, and GaAs have the greatest values of P = 1.8, 0.94, and 0.76 MW, respectively, for cw or 1‐sec pulse duration.

Diffraction of light by two orthogonal sound waves

Virendra N. Mahajan and Jack D. Gaskill

J. Appl. Phys. 45, 1518 (1974); http://dx.doi.org/10.1063/1.1663453 (3 pages)

Online Publication Date: 6 October 2003

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The diffraction of a light beam by two orthogonal sound waves is described. The Raman‐Nath equation for the diffracting system is derived and is shown to separate into two Raman‐Nath equations, one for each of the two sound‐wave components. Thus it is shown that diffraction by two orthogonal sound waves present simultaneously in a medium is equivalent to diffraction by the two waves present successively. Analytic solutions of the Raman‐Nath equation are obtained in the Raman‐Nath and Bragg regions of diffraction. Practical applications of the diffraction effect in the Bragg region are outlined.

Extension of the unified theory of grain boundaries. I. Structure of the boundaries

K. Sadananda and M. J. Marcinkowski

J. Appl. Phys. 45, 1521 (1974); http://dx.doi.org/10.1063/1.1663454 (12 pages) | Cited 9 times

Online Publication Date: 6 October 2003

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The structures of both low‐ and high‐angle grain boundaries are examined from a dislocation approach, and it is shown that coincidence‐site lattice theory can adequately account for the structure of boundaries of any angle. For simplicity, the structures of symmetric tilt and twist boundaries in simple cubic structures are analyzed. The concepts that are developed, however, are quite general and can be applied to more complex crystal structures. In particular, it is shown that any grain boundary can be considered to arise from some suitable combination of crystal lattice dislocations associated with each one of the two grains comprising the boundary. Although the analysis is done with rigid models, the conclusions reached are independent of any atomic relaxations that occur at the boundary. The results developed from the dislocation approach are compared with those of Bollmann's O‐lattice theory, and it is shown that the relatively complex O‐lattice theory may not be necessary for an understanding of the dislocation structure of grain boundaries. Also, concepts such as the Burgers circuit are rationalized, and it is shown that the defect content described by a given circuit depends directly on its reference lattice whereas the strain fields are related to the relaxations that occur around the defect.

Extension of the unified theory of grain boundaries. II. Deformation of the boundaries

K. Sadananda and M. J. Marcinkowski

J. Appl. Phys. 45, 1533 (1974); http://dx.doi.org/10.1063/1.1663455 (11 pages) | Cited 6 times

Online Publication Date: 6 October 2003

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The deformation of grain boundaries by crystal lattice dislocations is discussed in detail for the case of symmetric boundaries in simple cubic structures. In particular, It is shown that the motion of grain boundary dislocations that are generated as a result of various combinations of crystal lattice dislocations gives rise to either grain boundary sliding or grain boundary migration or both. The structure and motion of various types of ledges such as glide ledges, climb ledges, and compensated and uncompensated ledges are considered in this analysis. Although the analysis is done for simple cubic structures, the concepts developed are quite general and can be applied to more complex crystal structures. It is also shown that some of the grain boundary dislocation arrays can be suitably described as disclination dipoles, and such a dualistic representation is used to interpret the shape changes associated with the grain boundary deformation.

X‐ray diffraction in crystals of intermediate perfection. I. Calculation of the integral diffracted power for flat and curved crystals in symmetrical Bragg geometry

D. B. Brown and M. Fatemi

J. Appl. Phys. 45, 1544 (1974); http://dx.doi.org/10.1063/1.1663456 (11 pages) | Cited 5 times

Online Publication Date: 6 October 2003

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A method for the treatment of x‐ray extinction and absorption is developed for thick flat crystals in symmetrical Bragg geometry and for curved crystals in symmetrical Bragg geometry where the diffraction region may be approximated as a thin crystal in Laue geometry. This method permits the calculation of diffracting power vs wavelength. The crystals may have the full range of properties between the ideally imperfect and perfect cases. The parameters describing the mosaic blocks (mosaic block size and mosaic block misorientation) are related to the dislocation arrangement for crystals of Zachariasen's type I (where extinction is primarily controlled by the mosaic block misorientation). It is indicated that for crystals of type II (where extinction is primarily controlled by the mosaic block size) the mosaic blocks are usually due to defects other than dislocations.

X‐ray diffraction in crystals of intermediate perfection. II. A treatment of LiF in symmetrical Bragg geometry

D. B. Brown, M. Fatemi, and L. S. Birks

J. Appl. Phys. 45, 1555 (1974); http://dx.doi.org/10.1063/1.1663457 (7 pages) | Cited 3 times

Online Publication Date: 6 October 2003

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In part I of this series we presented a method for the calculation of the integral diffracting power applicable to flat and curved crystals in symmetrical Bragg geometry. In the present paper we report a test of the above method. The integral reflection coefficient vs wavelength has been measured and calculated for an unusually perfect crystal of LiF and for a crystal of LiF rendered relatively imperfect by ``flexing''. Agreement was good. The mean mosaic block size and misorientation used in the calculation were deduced by using dislocation etch pitting. It is concluded that LiF is of Zachariasen's type I (i.e., extinction is primarily controlled by the mosaic block misorientation).

Transport properties of bismuth films

Masasi Inoue, Yukio Tamaki, and Hisao Yagi

J. Appl. Phys. 45, 1562 (1974); http://dx.doi.org/10.1063/1.1663458 (5 pages) | Cited 17 times

Online Publication Date: 6 October 2003

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Glass‐coated bismuth films were deposited onto a glass substrate at room temperature and their Hall coefficients and electrical resistivities were measured between 77 and 300°K. Scanning electron micrographs revealed that the films prepared in this way were more polycrystalline than those deposited onto a heated mica substrate. Interesting features were found in the temperature dependence of the Hall coefficient: the thinner films with thickness t <500 Å were p type at higher temperatures and became n type below a critical temperature Tc, where Tc increased with the increase in t, whereas the thicker ones with t >500 Å were always n type over the temperature ranges studied. Hall mobility and magnetoresistance data are also presented here and the experimental results are discussed qualitatively.

Formation of stacking faults and enhanced diffusion in the oxidation of silicon

S. M. Hu

J. Appl. Phys. 45, 1567 (1974); http://dx.doi.org/10.1063/1.1663459 (7 pages) | Cited 213 times

Online Publication Date: 6 October 2003

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The phenomena of the formation of stacking faults and the enhanced diffusion during the oxidation of silicon are shown to be closely related and to have a common cause. A model is presented which at once can consistently explain various aspects of both phenomena; in particular, it is capable of explaining the crystal‐orientation dependence of these phenomena and the parabolic growth of stacking faults. The model envisages a small incompleteness (∼ 10−3) of oxidation, producing silicon interstitials. A concept is introduced that these excess interstitials, as they supersaturate the lattice, will undergo surface regrowth. The rate of interface regrowth is proportional to the density of surface kinks, which is in turn dependent on the surface orientation. The dependence is described. Quantitative analyses are given for the excess interstitials, the growth of stacking faults, and the enhancement of diffusion. The analyses also show that the stacking‐fault embryos are formed within a very short time of the start of oxidation, usually less than 1 sec, consequently leading to uniform stacking‐fault size. The occasionally observed variation in the size of bulk stacking faults is attributed to a continuous formation of stacking‐fault nuclei (e.g., oxide clusters and precipitates). The absence of a surface regrowth would predict a 1∕4 power law of stacking‐fault growth, in contradiction of the experiments.

Wavefront visualization of bulk acoustic waves

R. Torguet, C. Carles, J. M. Rouvaen, E. Bridoux, and M. Moriamez

J. Appl. Phys. 45, 1574 (1974); http://dx.doi.org/10.1063/1.1663460 (4 pages) | Cited 3 times

Online Publication Date: 6 October 2003

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Bulk acoustic waves at frequencies up to several hundred megahertz and acoustic powers down to the nanowatt range have been visualized via acousto‐optic Bragg diffraction. Using double‐optical and electrical‐heterodyne mixing, the acoustic wavefronts have been displayed over several wavelengths along the propagation path. Possible applications of the reported experiments are briefly reviewed.

Optical and channeling studies of ion‐bombarded GaP

S. H. Wemple, J. C. North, and J. M. Dishman

J. Appl. Phys. 45, 1578 (1974); http://dx.doi.org/10.1063/1.1663461 (12 pages) | Cited 27 times

Online Publication Date: 6 October 2003

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Below‐gap optical absorption, above‐gap reflectivity, photoluminescence, and He ion channeling backscattering measurements are reported for ion‐bombarded GaP. Each of the four experiments provides a measure of disorder. A one‐to‐one correspondence exists between the absorption, reflectivity, and backscattering measurements, and all three exhibit comparable sensitivity to damage. Photoluminescence is ∼ 100 times more sensitive. The absorption results suggest that every implanted ion species produces amorphous regions associated with each projectile and that these regions have properties very much like those of cold‐deposited amorphous films. The results are interpreted in terms of a model which ascribes these amorphous regions to localized melting followed by rapid quenching to a glassy (amorphous) state in which short‐range tetrahedral order remains intact. The damaged volume per bombarding ion as determined from absorption data is ∼6 times larger than that determined from channeling measurements. Although the annealing experiments show considerable scatter, the damage‐induced changes in absorption and reflectivity can be largely removed by annealing at ∼600°C for 30 min. Some anomalies are observed in the photoluminescence annealing results.

Dislocation effects in smectic‐A liquid crystals

P. S. Pershan

J. Appl. Phys. 45, 1590 (1974); http://dx.doi.org/10.1063/1.1663462 (15 pages) | Cited 66 times

Online Publication Date: 6 October 2003

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A method for calculating stress‐strain fields around edge dislocations in smectic‐A samples is discussed. In large part the method is isomorphic with the formalism for calculating magnetic fields around lines of electric current. The force law between dislocations that follows from the analogy is equivalent to the accepted force law between dislocations in crystals. In addition to rederiving the expression for the strain field surrounding an isolated edge dislocation that was first given by de Gennes, we present the solutions for the stress‐strain fields surrounding dislocations near one or two boundaries and also the strain field surrounding an edge dislocation that is curved to form a circular loop. The stress‐strain fields surrounding other defects with the same symmetries and boundary conditions can be expressed in terms of the above‐mentioned solutions using Green's function techniques. The relative stability of dislocations in samples with different types of boundaries and also the effects of dislocations on the elastic properties of smectic samples are also discussed in some detail. We comment briefly on the relation between the analogy discussed here and an earlier one developed by de Gennes.

Impurity control of domain switching in ferroelectric bismuth titanate

T. E. Luke

J. Appl. Phys. 45, 1605 (1974); http://dx.doi.org/10.1063/1.1663463 (6 pages) | Cited 5 times

Online Publication Date: 6 October 2003

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Bismuth titanate (Bi4Ti3O12) crystals grown from ``high‐purity'' melts are shown to have significantly lower activation fields than those reported previously when switching times are > 1 μsec. Controlled doping experiments demonstrate that the switching characteristics of Bi4Ti3O12 are controlled by the crystal impurity content. Specifically, the pseudothreshold for switching is not intrinsic to the material. A model is proposed for the activation‐field control which invokes the anisotropic conductivity due to the combination of impurity content and crystal structure.

Differential thermal analysis of ferroelectric and ferroelastic transitions in barium sodium niobate

J. C. Toledano and L. Pateau

J. Appl. Phys. 45, 1611 (1974); http://dx.doi.org/10.1063/1.1663464 (4 pages) | Cited 18 times

Online Publication Date: 6 October 2003

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Differential thermal analysis has been performed on barium sodium niobate single crystals. A thermal effect is detected for the first time at the 260°C ferroelastic transition. A large thermal peak is also observed at the 570°C Curie point. For both transitions an estimate of the latent heat is obtained by comparison with thermal effects recorded in gadolinium molybdate and quartz single crystals. The results for the first‐order 570°C transition is in good agreement with existing dielectric data. First order is also assigned to the lower ferroelastic transition whose features are discussed in the framework of the available thermodynamic theory.

Temperature and time dependence of dislocation pinning‐point density in fast‐neutron‐irradiated copper crystals

V. K. Paré, H. D. Guberman, and P. B. DeNee

J. Appl. Phys. 45, 1615 (1974); http://dx.doi.org/10.1063/1.1663465 (11 pages) | Cited 5 times

Online Publication Date: 6 October 2003

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The effects of fast‐neutron‐induced defects on the dislocation internal friction and modulus defect of copper crystals were studied by two procedures: (i) irradiation at 20°K followed by measurements during heating at a constant rate to room temperature and (ii) measurements during and after irradiations at various constant temperatures between 90 and 410°K. The measurements were made at low enough strain amplitude so that breakaway of dislocations from pinning points did not occur. Samples of known dislocation density were used in many of the experiments so that the ``vibrating‐string'' model of dislocation motion could be used to calculate approximate absolute values for the densities of radiation‐defect pinning points obtained at various temperatures. These were characterized by the ratio g of pinning points collected to freely migrating radiation defects created in the samples, assuming that on the average 20 defects can migrate away from the cascade region of each primary recoil. For the lower‐temperature pinning processes which showed no time delay, values of g increased monotonically from 10−6–10−5 at 60°K to 10−4–10−3 at 204°K. The higher‐temperature process is known to have a broad delay‐time distribution; by collecting all pinning points available at 410°K a g value of ∼0.1 was obtained. Because of uncertainty as to the validity of the vibrating‐string model, pinning‐point densities were obtained primarily from the modulus‐defect data. The damping data often implied the same densities but sometimes disagreed seriously with the modulus‐defect results.

Diffusion coefficient and electromigration velocity of copper in thin silver films

G. DiGiacomo, P. Peressini, and R. Rutledge

J. Appl. Phys. 45, 1626 (1974); http://dx.doi.org/10.1063/1.1663466 (4 pages) | Cited 7 times

Online Publication Date: 6 October 2003

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The objective of this work was to determine the Cu diffusion coefficient in silver thin films as a function of temperature, and Cu electromigration velocity as a function of electric current density and to test whether linearity between electromigration and current density was preserved at high current stress. An Ag stripe was doped with Cu in a limited region, and the movement of Cu out of this region under temperature and current stressing was measured by electron probe. The experiment was conducted at 200, 250, and 300°C and at current densities of 106, 2×106, and 3×106 A∕cm2. From the copper concentration profile, the diffusion coefficient D and the electromigration velocity V were calculated. Results show that the diffusion of Cu in Ag films obtained by extrapolation to use conditions (D=10−15 cm2∕sec at 55°C) is about 2 orders of magnitude greater than bulk, and that electromigration under ∼106−A∕cm2 stress is negligible when compared to thermal diffusion of Cu, even at ambient temperature. At high current density (3×106 A∕cm2), the electromigration velocity becomes much greater than the value predicted on the basis of linearity between V and J. This indicates a departure from the Nernst‐Einstein relationship of ion shift in a field.

Direct observation and identification of long‐period structures of SiC by transmission electron microscopy

H. Sato, S. Shinozaki, and M. Yessik

J. Appl. Phys. 45, 1630 (1974); http://dx.doi.org/10.1063/1.1663467 (5 pages) | Cited 13 times

Online Publication Date: 6 October 2003

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Transmission electron microscopy has been used for the observation of polytypes of SiC having very long periods. The periodicity of these structures can be observed from the direct resolution of structural lattice periods and from the diffraction patterns. The actual structures can be determined from the intensity distribution in the diffraction pattern, and this has been done for two of the structures. These have been identified as [(33)1632]3 or 303R and [(33)634(33)434]3 or 222R, two hitherto unknown structures. A mechanism for conveying the long‐distance information concerning the stacking order which leads to stabilization of the long‐period structures in SiC is suggested. This mechanism essentially involves a transformation from a basic structure of short period to accommodate a constraint from the surroundings.

Role of sequential annealing, oxidation, and diffusion upon defect generation in ion‐implanted silicon surfaces

S. Prussin

J. Appl. Phys. 45, 1635 (1974); http://dx.doi.org/10.1063/1.1663468 (8 pages) | Cited 29 times

Online Publication Date: 6 October 2003

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Ion implantation of boron was substituted for the chemical deposition of boron in the manufacture of a bipolar integrated circuit. The n+p+ test diodes were found to exhibit excessive reverse leakage while the p+n test diodes behaved normally. This was attributed to the defect structures developed by the interaction of sequential diffusion with defect nuclei introduced by ion implantation. We have found that the low‐temperature annealing treatments which are used to return full electrical activity to the implanted atoms leave a high density of defect nuclei in the implanted area. When the silicon surface is subjected to wet oxidation, these defect nuclei expand to form stacking faults or dislocations loops of such size that they can be detected by chemical etching and optical microscopy. This technique has permitted us to determine the annealing temperatures necessary to eliminate these implantation‐induced defect nuclei. A model is presented to describe the manner in which defect nuclei are generated by ion implantation and the means by which these defects are expanded by subsequent oxidation.

Analysis of mode coupling in piezoelectric waveguides

Mitsunori Sugimoto and Toshio Makimoto

J. Appl. Phys. 45, 1643 (1974); http://dx.doi.org/10.1063/1.1663469 (7 pages) | Cited 1 time

Online Publication Date: 6 October 2003

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A perturbed piezoelectric waveguide is constructed from a reference waveguide, which is specified by the eigenvalues and eigenfunctions, by the coordinate transformation, or other methods. In the perturbed waveguide, coupling occurs between normal modes of the reference waveguide. Coupling phenomena are analyzed by transforming Maxwell's and Newton's equations into the variational expression of the phase constant of the normal mode and then by applying the Rayleigh‐Ritz method. As an example, the couplings between purely elastic waveguide modes are discussed; and then the two‐mode approximation is applied in the case when two modes are degenerate or nearly degenerate. Mode conversion phenomena are discussed and from the viewpoint of the network theory, the mode transfer matrix relating the complex amplitudes of the two modes along the waveguide is defined and developed.

Properties of a dielectric‐rod waveguide immersed in plasma

J. N. Maiti and J. Basu

J. Appl. Phys. 45, 1650 (1974); http://dx.doi.org/10.1063/1.1663470 (7 pages) | Cited 3 times

Online Publication Date: 6 October 2003

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The paper presents a study of various aspects of propagation in the TM01 mode along a dielectric‐rod waveguide immersed in plasma. Expressions are derived and characteristics obtained for the dispersion relation, phase and group velocities, as well as power flow in and around the guide in the loss‐free case of propagation. The dispersion relation reveals that the TM01 mode is the dominant one with backward wave characteristics for low negative values of ϵp∕ϵd, where ϵp and ϵd are the dielectric constants of the plasma and the rod, respectively. The phase velocity is found to be always greater than the velocity of a plane wave in the rod medium if ϵp is positive, while for its negative values the phase velocity can be either greater or less. From the point of view of power concentration, the structure acts as a very good surface waveguide, particularly for high negative values of ϵp∕ϵd. The attenuation coefficient is subsequently derived by the standard perturbation method, assuming that both the plasma and the rod are slightly lossy. Finally, the possibility of using the waveguide as a plasma diagonostic tool is discussed, and it is shown how the results reported in the paper can be employed for determining the electron density and electron collision frequency for momentum transfer in a plasma.

Dynamics of intense relativistic electron beams in toroidal fields

James Benford, John Guillory, and Charles Stallings

J. Appl. Phys. 45, 1657 (1974); http://dx.doi.org/10.1063/1.1663471 (10 pages) | Cited 1 time

Online Publication Date: 6 October 2003

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Intense relativistic electron beams were propagated around a 180° toroidal sector to study beam dynamics in toroidal fields. The major beam drift under conditions for neutralization of self‐fields was along ‐ R × B and scaled as γZ∕Bt, where Z is the propagated distance, Bt the toroidal field, and γ the relativistic factor. This is indicative of curvature and ∇B drifts. Use of conducting walls caused an additional F × B drift around the chamber due to image current forces. Analysis of the distortion of a propagating rectangular beam shows that beam electrons follow field lines. Preliminary experiments on counterstreaming beams show inefficient reflection of beams from opposing diodes. Application of these results to beam injection and confinement in toroidal magnetic fields is discussed.

Interdiffusion and compound formation in Ta☒Au thin‐film couples

T. C. Tisone and S. S. Lau

J. Appl. Phys. 45, 1667 (1974); http://dx.doi.org/10.1063/1.1663472 (8 pages) | Cited 5 times

Online Publication Date: 6 October 2003

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An investigation of the interdiffusion between sputter‐deposited bilevel films of bcc Ta☒Au, β‐Ta☒Au, and Ta2N☒Au has been carried out by using x‐ray diffraction, electron microscopy, and electrical resistance measurements. In all three systems only the TaAu phase was observed to form. The temperature range of formation of the TaAu phase for the systems considered increased in the order β‐Ta, bcc Ta, and Ta2N. The resistance change for a given temperature increased in the order Ta2N, bcc Ta, and β‐Ta. It was concluded that the change of resistance occurred by three mechanisms: (1) diffusion of Ta into the Au grain boundaries, (2) diffusion of Ta into the Au bulk, and (3) transformation of the Au into a high‐resistivity TaAu phase. From the resistance measurements the kinetics of the formation of the TaAu phase were found to be diffusion controlled with the diffusion species moving through the TaAu phase grain boundaries.
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