Sputtering-induced vacancy cluster formation on TiO2(110)

Defects are introduced on an atomically clean TiO2(110) surface in a controllable manner via bombardment by 0.5 keV Ar+ ions, and the resultant material is probed with scanning tunneling microscopy and x-ray photoelectron spectroscopy. It is shown that ion bombardment leads to a change of stoichiometry and the formation of vacancy clusters, while annealing after prolonged bombardment forms regular rectangular cavities with single-atomic-layer steps. It is concluded that curvature-dependent sputtering in combination with adatom and vacancy diffusion is responsible for the observed structures.