STRUCTURE AND STABILITY OF THE SI(001) C(4X4)-SB SURFACE

Results of low-energy electron diffraction, Auger electron diffraction , low-energy ion scattering, and ab initio pseudopotential studies of submonolayer coverages of Sb on the Si(001) surface indicate the exist ence of an ordered c(4x4)-Sb reconstruction between 0.2 and 0.3 ML. An alysis of the ion-scattering data from this surface suggests an overla id above-row structure in which Sb dimers are situated directly above Si dimer rows. Ab initio pseudopotential calculations support this con clusion and confirm that such a uniform distribution of Sb ad-dimers o nly becomes stable for a very narrow coverage range around 0.25 ML.