High charge flexibility of the surface dangling bonds on the Si(1 1 1)-7×7 surface and NH 3 chemisorption: a DFT study

Abstract

The dissociative chemisorption of NH 3 on the Si(1 1 1)-7×7 surface has been investigated by means of hybrid density functional (B3LYP) cluster model calculations. It is shown that the dissociation of NH 3 occurs readily on either the restatom site or the adatom site via a molecular precursor, giving rise to NH 2 and H adspecies. Elaborate NBO (natural bond orbital) analyses reveal quite facile and unexpectedly significant charge transfer between the DBs (dangling bonds) of the restatom–adatom pair site even at a very large H 3N–Si distance (e.g., 3.4 Å), evidencing the high charge flexibility of the DB states on the Si(1 1 1)-7×7 surface.