Adsorbate-induced buckling switch of Si dimers in dissociated phenylamine on Si(001)

Abstract

Using first-principles density-functional calculations, we investigate the adsorption structures of phenylamine, NH2(C6H5), on the Si(001) surface. We find that the N atom initially bonds to the down Si atom of the buckled dimer and subsequently, adsorbed NH2(C6H5) dissociates into NH(C6H5) and H species. Unlike the case of ammonia where the buckling of Si dimers remains unchanged through ammonia dissociation, we find that the N-H dissociation in adsorbed phenylamine gives rise to the buckling switch of the neighboring Si dimers, thereby inducing a charge polarization in neighboring dimers such that the electrophilic (down-buckled) and nucleophilic (up-buckled) sides are oriented adjacent to the Si-NH(C6H5) and Si-H moieties, respectively. This adsorbate-induced buckling switch in dissociated phenylamine is caused by a greater electronegativity of the phenyl group compared to the H atom in dissociated ammonia.