Zur Oxydation von Metallen bei sehr tiefen Temperaturen

Abstract

The formation of oxide films on various metals has been investigated in the temperature range between 1·5 and 100°K. The metal films (50 to 150Å thick) were produced by condensation of the vapor on a quartz plate at about 100°K. After cooling down the films to helium temperatures, oxygen molecules were condensed to the fresh metal surface. The electrical resistance was measured before, during and after this O₂ condensation at temperatures between 1·5 and 300°K. The formation of an oxide layer causes an increase of the electrical resistance, since the conductivity of the oxide is comparatively low. The resistance behaviour of the metals investigated indicates two different steps of oxidation each one starting at a certain “characteristic” temperature below 25°K. Below the lower characteristic temperature, no reaction takes place. Increasing the temperature slowly, the oxide layer grows up to a final thickness. No further growing is detectable between 50 and 150°K for most of the metals. The results are discussed with regard to theoretical considerations ofMott, Cabrera andHauffe.