Effects of temperature and Ar+ ion bombardment on the initial oxidation stages of polycrystalline aluminium with water vapour

The initial stages of oxide formation following the interaction of water va pour with polycrystalline aluminium surfaces have been studied using x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Att enuation of the electron signal from the metallic substrate has been used t o follow the oxidation kinetics of aluminium as a function of energy and do se of Ar+ ion bombardment and temperature. The effects of energy and doses of Arl ion bombardment on oxidation kinetics have been examined in the ener gy range 1-5 keV and ion dose ranging from 1.3 X 10(16) to 3.8 X 10(17) ion s cm(-2). Although the increase in energy of Ar+ ion bombardment slightly m odified the oxidation kinetics, the effects of ion dose on oxidation kineti cs are shown to be more complex. There is a threshold dose of Arl ions abov e which the surface activity becomes significantly reduced; this is ascribe d to cluster formation blocking the surface diffusion pathway in the near-s urface region. The oxidation kinetics of aluminium also have been studied i n a range of temperature from room temperature up to 573 K. As the temperat ure increases, the oxidation rate of aluminium decreases due to a decrease in the sticking probability of water molecules on the aluminium surfaces. T he observed temperature dependence of the oxidation kinetics is likely to b e due to a precursor mechanism of water desorption. Copyright (C) 2001 John Wiley & Sons, Ltd.