Variations of the local electronic surface properties of TiO2„110... induced by intrinsic and extrinsic defects

Variation of the local electronic structure at rutile TiO2(110) surfaces was studied by scanning tunneling spectroscopy ~STS!. Structural surface features such as step edges, (132) reconstructed strands, and their terminations were correlated to changes in tunneling spectra. In particular, band-gap states, associated with a reduced surface, showed characteristic variations. In addition, electronic variations due to extrinsic defects are discussed. Nanometer wide protrusions in constant current scanning tunneling microscopy images were identified in STS as local electronic alterations. These features are interpreted to be due to local band bending induced by individual, charged impurity atoms.