Effect of Residual Gases on Superconducting Characteristics of Tin Films

Abstract

A special oil-free, ultra-high vacuum system has been used to deposit tin films at pressures less than 10-9 mm Hg onto room temperature substrates. These films were found to possess extremely sharp and reproducible magnetic field transitions as compared to films deposited by more conventional techniques. This resulted from breakup of the penumbra of a film deposited through a mask into electrically discontinuous islands leaving a film of uniform thickness. Specific residual gases were found to decrease the surface mobility of the tin atoms which contributed to continuous film edges and higher critical fields. For example, the critical field extrapolated to OaK increased from 370 oe for a pure film to 490, 590, and 820 oe as the ratio of oxygen molecules

Oxygen Incorporation in Reactive-Sputter-Deposited TiN Films: Influence of the Metal to O2 Gas Flux Ratio

“…Therefore, the O 2 pressure should be signiˆcantly reduced after ignition of the sputtering discharge. In the vacuum evaporation case, a reduction in the impurity gas pressure was observed and was attributed to the similar gettering eŠect 44) . The eŠect of gas gettering is included in the wellknown reactive sputtering model proposed by Berg et al 15,16) In that model, the incident reactive gas ‰ux is split into three parts: (1) that pumped out by the evacuation port of the system, (2) that gettered onto the active area of the target surface, and (3) that gettered onto the active area of the chamber wall.…”

Crystal growth and orientation in vacuum-condensed metal deposits: a systematic correlation with residual pressure, rate of deposition and thickness

“…Practically plane faces can indeed be seen on many of the crystal grains in the electron micrographs of the thicker tin deposits. The effect of oxygen present at an appreciable partial pressure during the deposition of the tin is also found to result in a much rougher form of the deposit surface than is found in deposits prepared in ultra-high vacuum (Caswell 1961.…”

Structure of Evaporated Metal Films

“…Some properties of thin films depend upon the impurity atoms adsorbed from the residual gases in the vacuum on to the surface of the growing film, and subsequently built into it (Caswell, 1961;Paul and Hanson, 1966). Clearly at pressures less than 10~9 torr, a film thrown in 100 sees can contain at most 0.1 of a monolayer.…”