Coadsorption patterns of N H3 molecules on the Si(001) surface observed using scanning tunneling microscopy

We have studied the coadsorption of N H3 molecules on the Si(001) surface using scanning tunneling microscopy. Three adsorption patterns are predominantly observed to be attributed to two N H3 molecules dissociated into N H2 and H. The most abundant one is a zigzag pattern where the dissociated N H2 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 N H2 groups.