STRUCTURAL STUDIES OF SI(001) SB(0.25 ML)-C(4X4)/

Recent experimental work reveals a c(4 X 4) reconstruction of the Si(0 01)/Sb surface in the coverage range between 0.2 and 0.3 monolayers. I n this paper we present the results of ab initio pseudopotential densi ty functional calculations for the 0.25 monolayer covered surface, We consider three possible structural models for the c(4 X 4) reconstruct ion: in the first, Sb dimers sit directly above the Si(001) dimer rows , in the second they bridge the gap between neighbouring Si(001) dimer rows, and in the third they are embedded into the existing Si(001) di mer rows. We determine that the configuration in which Sb dimers sit d irectly above the dimer rows is the most energetically favourable of t he three geometries. The structural parameters of this reconstruction are discussed in some detail. (C) 1998 Elsevier Science B.V.