Structural properties of a thallium-induced Si(111)-1x1 surface

Abstract

We report on the atomic arrangement of a thallium (Tl) induced 1x1 phase on a Si(111) surface determined by utilizing synchrotron x-ray scattering. Based on a quantitative analysis of intensity profiles of several crystal truncation rods, we find that Tl adatoms occupy the T-4 sites to produce a significantly asymmetric bonding geometry with neighboring Si atoms in the first silicon bilayer. The atomic arrangement determined in this study, including the bond length of 3.26+/-0.02 A for the Tl-Si bonds, agrees quite well with the one reported earlier. Our results not only provide bonding parameters of the surface with an improved accuracy, but also confirm the theoretical prediction that the Tl-Si bonding is more ionic than covalent.