摘要:

The diffusion of gold into the grain boundaries of copper bicrystals was studied for couples of both a continuous and an instantaneous source. The concentration contours along the grain boundaries were measured by means of electron‐probe microanalysis. For the continuous source conditions at 750°C, the ratio of the coefficients of grain‐boundary diffusion and lattice diffusion decreased from 6×105to about 103with increasing gold concentration from 0.5 to 15 at. % gold. The rate of grain‐boundary diffusion decreases even though there is some increase in the rate of lattice diffusion. There was found some contribution of surface diffusion to the couples with an instantaneous or thin source, i.e., 0.5 &mgr; thick. The concentration contours observed in these couples agreed generally with the theoretical solutions.

ISSN:0021-8979    

DOI:10.1063/1.1702448

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Whipple's exact solution to the idealized grain‐boundary diffusion problem has been evaluated numerically for ranges of parameters appropriate to existing and contemplated experiments. From these evaluations the concentration at the grain boundary, the integrated concentration at fixed depth of penetration, and the angle at which isoconcentration contours intersect the grain boundary are obtained, these results being presented in either tabular or graphical form. The ranges of validity of approximate solutions obtained by various authors are discussed on the basis of the numerical results, as is the use of the graphs and tables for the interpretation of experimental data.

ISSN:0021-8979    

DOI:10.1063/1.1702449

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Emitter cells with Al2O3film thicknesses between 67 and 150 Å and Au film thicknesses between 200 and 300 Å were operated at voltages up to 10 V. TypicalI‐Vcharacteristics for the total cell currents are presented. The curves suggest tunnel emission through the barrier at the Al‐Al2O3interface when the cell is operated for the first time and only small currents have been drawn. After passage of large currents, theI‐Vcharacteristics become temperature dependent. The normal energy distribution of the emitted electrons is measured and a linear dependence of the average energy on cell voltages is established. The fractions of current emitted through the Au into the vacuum is determined as a function of the Al2O3thickness. Using the attenuation lengths of gold reported recently by Mead, an attenuation length of about 24 Å is deduced for electrons, which within the insulator have gained an energy of nearly 3 eV. The emitted current could be increased considerably by depositing a low work function material (Ba) at the gold surface. The maximum fraction of current emitted into the vacuum was 10−2, at an emitted current density of nearly 5 mA/cm2.

ISSN:0021-8979    

DOI:10.1063/1.1702450

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The scattering of plane compressional or shear waves by a cavity ribbon with widthain an elastic medium is computed by the use of the Mathieu functions when the displacement of the incident wave is inxyplane. The diffraction patterns forkca/2=1, 2, and 4, and forks=2kcare obtained; the diffraction patterns by a cavity ribbon are similar to those of the sound wave by a perfectly absorbing ribbon only when the incident compressional waves propagate to the direction normal to the plane of the ribbon. The scattering cross sectionsQ/aare of the order of (ka)3in the Rayleigh case. These facts support the conclusion of the previous paper (rigid ribbon).

ISSN:0021-8979    

DOI:10.1063/1.1702451

出版商:AIP    

年代:1962

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1702453

出版商:AIP    

年代:1962

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1702454

出版商:AIP    

年代:1962

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1702455

出版商:AIP    

年代:1962

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1702456

出版商:AIP    

年代:1962

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1702458

出版商:AIP    

年代:1962

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1702459

出版商:AIP    

年代:1962

数据来源: AIP