Local catalytic effect of cesium on the oxidation of silicon

We have studied the catalytic effect of adsorbed cesium on the initial sticking coefficient ${\mathit{s}}_0$ of oxygen on Si(100) at room temperature. Two different kinds of cesium sites were observed. ${\mathit{s}}_0$ was found to increase linearly with the coverage of each kind of cesium site. The data show that the effect of cesium is local, but ${\mathit{s}}_0$ does not correlate with the Cs dipole moment. An oxygen-cesium bond is formed in the reaction and cesium is passivated in this process, leading to an exponential decrease of the sticking coefficient with the oxygen coverage.