The re-oxidation of the substoichiometric TiO2(110) surface in the presence of crystallographic shear planes

Re-oxidation of reduced oxide surfaces is a fundamental step in catalysis and related fields. This paper reports the first study of the re-oxidation, at elevated temperature, of crystallographic shear planes (CSPs) occurring on the non-stoichiometric rutile TiO2(110) surface by scanning tunnelling microscopy (STM). The re-oxidation occurs by the reaction of interstitial Tin+ ions dissolved in the crystal bulk with oxygen at the surface to re-grow new TiO2 layers on the surface. The CSPs act as nucleation centres for the re-growth and are, in general, preserved during the early stages of the re-oxidation. CSPs appear in pairs on the surface and sandwich a layer of rutile that is displaced by one half an atomic step height from the original terrace. Each step edge of the pair shows markedly different structure and growth rate. The growth of the surface also takes place on the displaced region between CSP pairs.