Imaging chemical-bond formation with the scanning tunneling microscope: NH3 dissociation on Si(001)

Abstract

We have directly observed chemisorption-induced changes in surface chemical bonding using a scanning tunneling microscope (STM). The dissociative adsorption of NH3 on Si(001) preserves the (2×1) local symmetry, but STM images reveal changes in the spatial distribution of occupied electronic states which allow us to distinguish reacted and unreacted Si(001) dimers. The STM results on the reacted surface are interpreted in terms of tunneling through localized Si-H bonding orbitals of a Si(001)-(2×1)H monohydride. © 1987 The American Physical Society.