Reoxidation of TiO2(110) via Ti interstitials and line defects

The interaction of oxygen with line defects of Ti interstitials on a TiO2(110) surface is investigated using scanning tunneling microscopy (STM) measurements and first-principles calculations. Ab initio molecular dynamics calculations show that an oxygen molecule dissociatively adsorbs on a row of Ti interstitials. Oxygen atoms subsequently surround a Ti interstitial to form the equatorial plane of a partially complete octahedron, a basic building block for single- and double-strand formation. Upon the exposure of single strands to oxygen at room temperature, bright spots preferentially agglomerate on and along strands. The STM images of the bright spots, interpreted with density functional theory, indicate that they are TiOx (x < 2) aggregates and that strands may serve as nucleation sites for the surface growth.