Properties of Ionic Bombarded Silicon

This paper deals with a new and very interesting technique by which the properties of silicon surfaces are altered very materially by bombardment with ions of such (/ases as hydrogen, helium, nitrogen and argon. The change in rectifying properties has been of special interest but there have been considered also changes in the structural features of the material itself. The effects of bombardment on the rectifying properties are illustrated by a series of characteristic curves systematically arranged to bring out the effects of the several variables of experiment such, for example, as ion velocity, intensity of bombarding current, length of time of bombardment, kind of gas, and the temperature of the specimen during bombardment. The effect of bombardment on materials contaminated with impurities is also illustrated. It is of particular practical importance that silicon contaminated with boron to the point where it shows relatively little rectification can be modified by bombardment to make it even better than most unbombarded materials. Some years ago, the writer discovered that the electrical properties of silicon surfaces could be greatly modified by bombardment with positive ions. The ions in question were generated in a low pressure discharge in some gas, like hydrogen, helium or nitrogen, and after passing through a perforated cathode were accelerated to a suitable velocity before impinging 011 the surface to be treated. This scheme may be contrasted with other methods subsequently reported for treating germanium 1 in which high-velocity ions were derived from radioactive sources.