In this paper, the effect of Ar+ bombardment of SrTiO3:Nb surface layers is investigated on the macro- and nanoscale using surface-sensitive methods. After bombardment, the stoichiometry and electronic structure are changed distinctly leading to an insulator-to-metal transition related to the change of the Ti d electron from d0 to d1 and d2. During bombardment, conducting islands are formed on the surface. The induced metallic state is not stable and can be reversed due to a redox process by external oxidation and even by self-reoxidation upon heating the sample to temperatures of 300{deg}C.
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