No abstract available

No abstract available

[en] This study examines the mechanisms governing sustained tin plasma formation in vacuum. The authors have experimentally demonstrated that sustained tin plasmas can form in vacuum at dc power supply voltages as low as 4 V, and present a qualitative model for the observed voltage and current signatures associated with tin plasma formation. Engineering estimates were developed to help quantify tin whisker risk as a function of power supply voltage. Implications for space applications are also discussed

[en] β, the increase of the macroscopic electric field at the tip of a projection, varies with the gap length. The sign and magnitude of this variation depends upon how the gap length is defined. If gap length is defined as x, the distance from the projection tip to the opposing electrode, then β is a strong function of x and may be approximated by β(x) = β/sub infinity/x/(x+h) [h = projection height] in the region where x/h>10/β/sub infinity/. If gap length is defined as d, the interelectrode distance ignoring the projection, then β is a weak function of d and may be set equal to β/sub infinity/ in the region d/h>2

[en] A range of micron-sized Hall probe arrays has been used to investigate the Bean-Livingston surface barrier in single crystal whiskers of the type 11 superconductor Bi₂Sr₂CaCu₂O_8+δ. It is shown that the magnetic properties of the whiskers are dominated by surface barriers, and hysteresis loops exhibit behaviour entirely consistent with such a system, showing very small magnetisation on the return leg. Measurements of the temperature dependence of the field of first flux penetration indicate that above approximately 5mT the vortex lines decouple into stacks of two-dimensional vortex pancakes, which surmount the surface barrier through thermal activation, in agreement with recent models of giant flux creep over surface barriers. Once inside the whisker, the vortices collect in the centre to produce a dome-shaped magnetic flux profile, which is observed experimentally. Careful measurements of the initial leg of the hysteresis loop show a sawtooth structure, which is interpreted as evidence of a hierarchy of stable vortex states. Field-cooled measurements exhibit a sharp drop in the local magnetic induction, which is interpreted as a boundary between a regime dominated by surface barriers and a regime dominated by the inter-vortex repulsion. Transport measurements have also been carried out, and the results support the idea that the transport properties of the whiskers are strongly affected by surface barriers. (author)

No abstract available

No abstract available

[en] Oriented growing of filament type GaAs, GaP, InAs, GaInAs crystals from steam, on the backing from the same compounds (GaAs, GaP) and different compounds (InAs/GaAs, GaInAs/GaAs) was investigated. Regularity of crystal growing on polar A(3), B(3) and non-polar (001), (02) faces was studied. Conditions were determined for ordered (for example, perpendicular to the base layer) growing on polar A(3) and B(3) faces. In all backings discrete spectrum was found of crystallographic filament crystal systems with preferable development of faces B(3). For determination of kinetic coefficients of polar face crystallization, dependence of A³B⁵ filament crystal growing speed on their diameter was used. Periodic instability of diameter was found during growing of InAs and GaInAs filament crystals

[en] Metallic whiskers of pure lead (Pb) have been observed in the solder of several types of transistors. The conditions that lead to these whiskers were evaluated, including characterization of the whisker lengths and whisker density as a function of time and temperature. The potential cause and impact they would have on the reliability of electronics has been investigated. Based on these results, it is hypothesized that these whiskers may be caused by the relief of residual stresses that are created during the evolution of Au-In and/or Au-Pb intermetallic compounds or, possibly, by a decomposition of the AuPb₃ phase. Due to their small size, the Pb whiskers that were observed were considered to not be a reliability concern, but similar or larger Pb whiskers could cause electrical failure in some applications.

[en] The equilibrium thermal fluctuation in metal films is studied with careful consideration of the finite size of the specimen and the boundary conditions on the metal-vacuum and metal-substrate interfaces. For a freely suspended film, the noise spectrum due to bulk fluctuation has two parts, a frequency-independent part below a characteristic frequency and an f/sup -3/2/ part above that frequency. The characteristic frequency is the inverse of the diffusion time across the largest dimension of the specimen. The 1/f spectrum is obtained when two conditions are met : (i) the metal film is deposited on a substrate of very low bulk thermal conductivity; and (ii) the thermal fluctuation in the film is two dimensional and is mainly excited by the random flow of heat between the film and the substrate. In freely standing metal whiskers the 1/f spectrum can be obtained when the fluctuation is excited by white-noise sources at the ends