Enhanced sensitivity to oxide surface defects using Auger-photoelectron coincidence spectroscopy

We present Auger-photoelectron coincidence (APECS) spectra of the Ti 3p core level obtained in coincidence with Ti M2,3VV Auger electrons from the stoichiometric and Vacuum annealed TiO2(110) surfaces. For both surfaces, emission corresponding to reduced oxidation states has approximately an order of magnitude greater relative intensity in the coincidence spectrum as compared with the corresponding ordinary (singles) photoemission spectrum. We associate the excess coincidence signal from the stoichiometric surface with previously undetected residual defects. The origins and implications of the enhanced sensitivity of APECS to defects at oxide surfaces is discussed. (C) 1997 Elsevier Science B.V.