Interplay of hydrogen-bond and coordinate covalent-bond interactions in self-assembly of NH3 molecules on the Si(001) surface

Abstract

An exchange of hydrogen-bond and coordinate covalent-bond (dative-bond) interactions is found to play a critical role in the self-assembly of NH3 molecules on the Si(001) surface. An NH3 molecule in the height of similar to 3-10 angstrom above the surface is attracted toward the preadsorbed NH2 moiety through the long-range H-bond interaction. Within similar to 3 angstrom, the H-bond interaction becomes repulsive, and instead the dative bond with the buckled-down Si atom governs the adsorption process. The interplay of the two interactions induces the clustering and the zigzag feature of the dissociatively adsorbed NH3 molecules on the Si(001) surface.