SURFACE HYDROXYLATION OF SINGLE-CRYSTAL ALUMINUM(110) IN ULTRAHIGH-VACUUM

Water adsorbs dissociatively onto the Al(110) surface at 105 K. About one-third of the first layer of adsorbed water forms surface hydroxyls, and the remainder dissociates completely, forming a surface oxide. After formation of the oxide and hydroxide layer, water adsorbs molecularly and reversibly. The surface retains some order during the early stages of the reaction with water. The fully hydroxylated surface is disordered. The degree of hydroxylation maybe assessed using X-ray photoelectron spectroscopy. The hydroxylated surface is thermally stable up to about 400 K. The surface becomes more oxidized and the total hydroxyl coverage increases by exposing an already hydroxylated surface to additional water, and the relative proportion of hydroxyl to oxidic oxygen increases slightly.