Surface X-ray structure analysis of the TiO2(100)-(1x3) reconstruction

Using grazing incidence surface X-ray diffraction, we have investigated the superstructure of TiO2(100)-(1 x 3) (rutile). The analysis of both fractional order superlattice rods and integer order crystal truncation rods (229 independent reflections in total), leads to a structure model which can basically be described as the formation of {110} micro-facets on the surface. In addition, strong lateral and vertical relaxations of the titanium and oxygen atoms exist down to about 9 Angstrom below the surface. The surface titanium atoms are found to reside in different environments, namely in three-, five-and;six-fold oxygen coordination and in a bridge site. Furthermore, we determined a 40% occupancy of an interstitial site occupied by one titanium atom per (1 x 3) unit cell. The surface stoichiometry is given by the formula TiO1.68. Our structure model is significantly different from previous X-ray data [P. Zschack et al., Surf. Sci. 262 (1992) 395], but is in good agreement with spectroscopic experiments and scanning tunneling microscopy investigations. (C) 1998 Published by Elsevier Science B.V.