Displacement processes on germanium surfaces

Abstract

Some displacement experiments were carried out on germanium surfaces produced by crushing. In these a monolayer of either water, methanol, n-butanol, isopropanol or atomic hydrogen was first adsorbed, the excess gas removed from the gaseous phase and then a known amount of oxygen admitted to the system. The results show that oxygen reacted with the germanium surface in spite of the material already adsorbed thereon. For those surfaces covered with a monolayer of water it was found that oxygen displaced most of the water from the surface. The take-up of oxygen was retarded in the early stages of the reaction, compared with a clean germanium surface, but was greater at longer times. The logarithmic rate law was not obeyed. Where alcohols were the “pre-adsorbed” material the results were qualitatively very similar to water but the retarding effect at the beginning of oxygen adsorption was greater for the larger molecules. Oxygen adsorbed to a considerable extent on surfaces covered with a monolayer of hydrogen and, as with the other materials, the early take-up of oxygen was less than with a clean surface. The oxygen take-up after long times was approximately the same as that on the clean germanium surface. Only a small fraction, if any, of the hydrogen was desorbed during the adsorption of oxygen. This certainly suggests that the binding of the hydrogen atoms to the germanium surface is not of the simple covalent type that might have been expected.