STRUCTURE-ANALYSIS OF AN ALKALI-METAL ADSORBED SI(001)(2X1) SURFACE BY TENSOR LEED

The structures of the alkali metal (K, Cs) adsorbed Si(001)(2 x 1) sur face have been studied by tensor LEED. A reliability factor (R factor) analysis has been carried out for models having different sites for t he alkali atoms, that is, a pedestal site model (so called Levine's mo del), a cave site model and a double-layer model. Although the differe nce between the numerical values of R is small for these models, the s mallest R factor is obtained for the double-layer model with a symmetr ic dimer model for the topmost Si atoms.