Ab-initio study of the adsorption of H2S onto the Si(001) surface

The adsorption of H2S on to the Si(001)-(1 x 2) surface is studied, based u pon ab-initio pseudopotential calculations. We have used a dissociative ads orption model with adsorbed species (SH)(-) and H+. The sulphur atom is loc ated along the dangling bond direction on one component of the Si dimer, th e I-I atom in the (SH)(-) complex is bonded to the S atom, and H+ is bonded along the dangling bond direction of the other dimer component. The adsorp tion of the molecule removes the buckling of the Si dimer. Our calculated b ond lengths for Si-S, Si-H and S-H are 2.15, 1.53 and 1.41 Angstrom, which are very close to the sum of their corresponding covalent radii. We find th at the adsorption of H2S passivates the Si(001) surface. The system is char acterized by the presence of a single surface state just below the bulk val ence band maximum. (C) 1999 Elsevier Science B.V. All rights reserved.