Coadsorption patterns of NH3 molecules on the Si(001) surface observed using scanning tunneling microscopy

Abstract

We have studied the coadsorption of NH3 molecules on the Si(001) surface using scanning tunneling microscopy. Three adsorption patterns are predominantly observed to be attributed to two NH3 molecules dissociated into NH2 and H. The most abundant one is a zigzag pattern where the dissociated NH2 groups reside on the alternating sides of a dimer row, which is followed by a combined adsorption of the on-dimer and the inter-dimer (ID) configuration. The last one is a linear pattern of the IDs. These observations suggest a substrate-mediated effective repulsion between NH2 groups.