Structural studies of Si(001)/Sb(0.25 ML)-c(4 × 4)

Recent experimental work reveals a c(4 × 4) reconstruction of the Si(001)/Sb surface in the coverage range between 0.2 and 0.3 monolayers. In this paper we present the results of ab initio pseudopotential density functional calculations for the 0.25 monolayer covered surface. We consider three possible structural models for the c(4 × 4) reconstruction: 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) dimer rows. We determine that the configuration in which Sb dimers sit directly above the dimer rows is the most energetically favourable of the three geometries. The structural parameters of this reconstruction are discussed in some detail.