X-ray scattering for the atomic structure of a barium-induced Si(111)-3 x 2 surface

Abstract

We have investigated the atomic arrangement of a barium (Ba)-induced Si(111)-3x2 surface by using surface-sensitive synchrotron X-ray scattering. In-plane fractional-order reflections obtained from three rotational domains of 3x1 symmetry have been used to examine several competing structural models including the honeycomb-chain-channel (HCC) and the double-pi-bonded chain (D pi C) models. By fitting two different data sets, both the goodness-of-the fits chi(2) and the residuum R-factor strongly favor the HCC over the D pi C model. We conclude that a Ba-paired HCC structure with a 1/3 monolayer of Ba coverage best describes the Ba-induced 3 x 2 surface with a Ba-Ba interatomic spacing d=1.93 angstrom.