The surface structure of TiO2(210) studied by atomically resolved STM and atomistic simulation

The (210) surface of rutile (TiO2) has been studied by the experimental tec hniques of scanning tunnelling microscopy (STM), low energy electron diffra ction (LEED) and X-ray photoelectron spectroscopy and by atomistic simulati on. Atomic scale imaging in STM is most easily achieved at positive sample bias, thereby sampling empty electronic states. Images from surfaces prepar ed by ion bombardment and UHV annealing are dominated by terraces supportin g bright rows with a similar to 10 Angstrom separation along the [1 (2) ove r bar 0] direction as expected for a (1 x 1) reconstruction. The STM images are interpreted in terms of a structure with a lower energy than found in previous atomistic simulation studies. This is built up from {110} nanoface ts of dimension a/root 2 and 3a/root 2, where a is the tetragonal lattice p arameter. Several characteristic defect features on the TiO2(210) (1 x 1) s urface are discussed in relation to this model. LEED indicates that superst ructures involving periodicities of up to 50 Angstrom along [1 (2) over bar 0] co-exist with the (1 x 1) terraces, particularly after prolonged anneal ing in UHV. Some of these enlarged nanofacets have also been imaged by STM. (C) 2000 Published by Elsevier Science B.V. All rights reserved.