Low energy ion scattering study of oxygen adsorption on a Cu[100] single crystal surface. Pt. 2

The kinetics of the O2/Cu[100] system at room temperature have been studied with Low Energy Ion Scattering. Two measuring methods have been applied: 1) A method in which the coverage is measured as a function of oxygen exposure. In this method the influence of the ion beam is kept as low as possible. 2) A method in which the oxygen coverage is measured as a function of oxygen pressure, after an equilibrium is reached between adsorption and ion-induced desorption. In both methods the O- recoil signal and the Ne+ vertical strokeO reflection signal were evaluated. It is known from other scattering studies that at least two essentially different oxygen positions are involved at the Cu[100] surface. We tried to describe all experimental results with a model in which the two types of sites i become covered independently, with a sticking probability S(thetasub(i))=Ssub(0i)(1-thetasub(i)). With this model it was possible to reproduce all experimental results using physically plausible parameter values, except for the Ne+ vertical strokeO reflection signal when using method 2. (orig.).