ELECTRON SPECTROSCOPIC STUDY OF THE INTERACTION OF OXYGEN WITH CO(1120) AND OF COADSORPTION WITH WATER

Coverage dependence of oxygen adsorption on the hexagonal Co(11 ($) ov er bar 20) surface is studied at 100 and 320 K by means of Auger elect ron spectroscopy (AES), photoelectron spectroscopy (XPS, UPS) and chan ge in work function (Delta phi). Adsorption of oxygen at 100 K leads t o the formation of Co3O4-like features together with adsorbed oxygen. An influence of a precursor on the adsorption kinetics is proposed. Ox ygen at 320 K builds up CoO, and the uptake behaviour is explained bes t in terms of chemisorption and oxide nucleation followed by island gr owth of the oxide. The explanation of the nature of a second oxygen sp ecies, observed in the Ols XP spectra, and the characterisation of OH are facilitated by a coadsorption experiment with oxygen and water at 100 K.