Microscopy of Metal Oxide Surfaces

Widespread application of metal oxides in catalysis, gas sensing, and as substrates for thin film growth has stimulated a strong interest in the atomic and electronic surface structure of these materials. The electronic structure of many metal oxide surfaces is characterised, and complicated from the theoretical modelling point of view, by the presence of strong on-site Coulomb repulsion (strong correlations) between valence electrons localised on the metal ions. Additionally, experimental studies have to deal with the difficulties associated with the electrically insulating nature of many of these oxides. We have overcome these problems through the development of novel experimental and theoretical techniques capable of providing structural and electronic information about strongly correlated insulating metal oxide surfaces.The surfaces of NiOand CoOwere investigated through elevated temperature scanning tunnelling microscopy (STM)thereby overcoming problems of low electrical conductivity of the samples.We show atomically resolved elevated temperature STMimages of (001) cobalt and nickel monoxide surfaces obtained under similar conditions which show an order of magnitude difference in the atomic corrugation heights.