Electron Stimulated Desorption (ESD) of Ammonia on TiO₂(110): The Influence of Substrate Defect Structure

Abstract

Electron stimulated processes for NH₃ adsorbed on rutile TiO₂(110) have been studied by means of XPS and mass — resolved ESDIAD (electron stimulated desorption angular ion distribution). We have used three differently prepared TiO₂ surfaces to study the influence of the substrate defect structure on the interaction with NH₃: a stoichiometric nearly perfect surface, a high — temperature annealed slightly oxygen deficient surface and a sputtered highly oxygen deficient surface. In the limit of a stoichiometric surface, electron irradiation induces the desorption of NH₃ molecules. When the highly oxygen deficient TiO₂ surface is used as substrate, both desorption and electron stimulated dissociation of NH₃ take place with atomic nitrogen the final product of the dissociation process. These measurements provide direct evidence for the role of surface defects of an oxide substrate in electron stimulated reaction pathways.