Oxidation of polycrystalline zinc and cadmium surfaces by wet and dry oxygen studied by ultraviolet photoelectron spectroscopy

Abstract

He I/II ultraviolet photoelectron spectroscopy (u.p.s.) has been used to record the early stages of the oxidation of polycrystalline zinc and cadmium. The metals were cleaned by the process of continuous scrape so that all oxygen doses are given over a period of 0.5 s. Ionization from the O 2p valence bands indicates the formation of the simple metal oxide at all doses. Study of the metal valence d feature has enabled the fraction of metal atoms oxidized in the surface layers to be estimated. The oxide features proved to be very sensitive to the presence of low pressures of H₂O. Hydroxide features have been identified by using wet oxygen and it is suggested that this sensitivity to hydrolysis might explain the “anomalous” oxygen 1s feature reported in X-ray photoelectron spectroscopy (X.p.s.).