The adsorption geometry of Cs on Si(110)

The adsorption site of Cs on Si(110)“16 × 2” has been investigated by using X-ray standing-wave fields. The (111) and (220) Fourier components of the Cs distribution function were measured for different Cs coverages and annealing conditions. In all cases the experimental results favour the hollow adsorption site. After Cs deposition, different surface reconstructions were observed depending on the Cs coverage. For saturation coverage (θ$_{Cs}$ = 0.5ML, the surface displayed a 1 × 1 LEED pattern; at θcs = 0.15 ML a 2 × 2 pattern appeared, which reverted into a 5 × 4 at θ$_{Cs}$$¯0.10 ML. For even smaller coverages the 5 × 4 pattern weakened and streaks along [001] appeared. Plausible atomic models for these reconstructions are proposed on the basis of the determined adsorption site and the LEED patterns