The role of surface irregularities (steps, kinks) and point defects on the chemical reactivity of solid surfaces

Abstract

Abstract The role of surface defects on the chemical reactivity of single crystal surfaces is illustrated here with three examples. In the first example we show how the presence of monatomic steps, on an otherwise flat Pt(111) surface, alters the chemisorption and dissociation of H. It was found by use of a mixed molecular beam of H2+D2that the production of HD depends on the angle of incidence of the beam with respect to the step edges being larger when the incident direction is perpendicular to the open side of the step edges. In the second example, we show how the kinetics of oxide growth in a Ni(100) crystal is affected by the presence of defects induced by ion bombardment of the surface. We have found that the initial rate of oxygen incorporation following the chemisorption stage is directly proportional to the dose of Ar ions used to produce the damage. In the annealed, un-bombarded Ni(100) surface, the incorporation of of oxygen stops after a surface oxide layer is completed. In the third example we show how the presence of oxygen vacancies and Ti+3 ions in the SrTiO3(111) surface affects its chemical properties, both in the chemisorption of 02, H2, and H2O and also in the photodissociation of H2O by illumination of the crystal surface with photons of band gap energy.