STRUCTURAL MODELS FOR SB ON SI(113) - AN EXPERIMENTAL AND THEORETICALSTM STUDY

We present a combined experimental (scanning tunnelling microscopy) an d theoretical (ab initio calculations) study of the atomic structure o f Sb/Si(113). The structural unit of the clean Si(113)3 x 2 surface co ntains 3 elements: a pentamer above a subsurface interstitial atom, an adatom, and a tetramer. Because the subsurface interstitials are stab le only at very low Sb coverages, we attempt to describe high coverage Sb/Si(113) in terms of the two remaining ''conventional'' elements. T his leads to several possible structures with various coverages and to pologies resulting from various relative positions of adatoms and tetr amers as well as from occupation of atomic positions by either Si or S b. In particular, we present arguments in favour of a specific atomic model for Sb/Si(113) for a coverage of theta(Sb) = 0.75.