J. App. Phys. 84, 6070 (1998).

Adsorption and desorption of S on and off Si(001) studied by Ab initio Density Functional Theory


M. Çakmak and G.P. Srivastava

School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL, UK


Abstract

We present detailed ab initio density functional calculations of equilibrium atomic geometry, electronic states and chemical bonding for the adsorption of elemental S on Si(001). Following recently reported room temperature LEED, AES, TDS and WF measurements by Papageorgopoulos et al, three different adsorption models have been studied: hemisulfide-(2 x 1) structure, monosulfide-(1 x 1) structure, and disulfide-(1 x 1) structure. For hemisulfide and monosulfide structures, the calculated location of S above the Si(001) surface is in excellent agreement with experiment. An analysis of surface free energy suggests that, in the allowed range of S chemical potential, the monosulfide structure is more stable than the hemisulfide and disulfide structures. A signature of desorption of SiS unit is obtained from the study of the disulfide structure.