RBS studies of the absolute coverage of Cs on the Si(1 1 1)-7×7 surface

The absolute saturation coverage of Cs adsorbed on the Si(1 1 1)-7×7 surface at room temperature has been measured using Rutherford backscattering spectrometry. At saturation, coverage is 0.51±0.02 monolayers (ML) where 1 ML=7.83×1014 atoms/cm2. This value constrains proposed ordered structural models by placing a strict upper limit on the absolute coverage of the first Cs layer adsorbed on Si(1 0 0) at room temperature. Proposed structural models with lower coverages of ordered Cs must include substantial disordered components.