Real-time observation of surface reactivity and mobility with scanning tunneling microscopy

Scanning tunneling microscopy allows the direct observation of reactions on surfaces on the atomic scale that otherwise must be inferred from the statistical behavior of hundred of trillions of molecules or atoms. Since the study of the details of reactions on this length scale began, our conception of surface reactivity has changed profoundly. In this Account we focus attention on our real-time observations of reactions for a number of systems, including the island growth of surface oxide on Cu(110), the anisotropic and site-specific reactivity of this oxide with carbon monoxide and ammonia, the collective motion of laterally interacting O(a) and SO(3)(a), and the incorporation of metal atoms into the structures of molecular intermediates formed in the reaction of ammonia with O(a) on Ag(110). These nanoscale, time-resolved movies capture the events as they occur, providing a dynamic picture of the distribution of reactants and products on the surface, thus providing a better understanding of the roles of reactant distribution and site specificity in surface reactivity.