Measurement of the Growth of Oxide Layers on Metals by Low-Energy Electron Spectroscopy: Aluminum

Abstract

The energy-loss spectra of 350-eV electrons reflected from aluminum were observed during the oxidation of a freshly evaporated film. The loss spectra due to surface plasma showed characteristic variations in the process of oxidation. The thickness of the oxide layer was measured by using the dispersion relation of surface plasmons. This method was shown to be useful for studying thin oxide layers (<20 Å). Oxide films grew on aluminum in different ways when the pressures were 1×10−7 and 1×10−8 Torr, where most of the residual gas was hydrogen and water. In the former case, the oxide layer in the initial stage was islandlike, whereas in the latter case it was uniform. Oxide films grew abruptly about 20 min after evaporation of the aluminum, as was confirmed by an analysis of the residual gas. The rate of growth of uniform oxide layers was consistent with a logarithmic law.