Sn addition in the CeO2 thin film by simultaneous Sn metal and cerium oxide magnetron sputtering causes growth of Ce3+ rich films whilst pure cerium oxide sputtering provides stoichiometric CeO2 layers. Ce4+ -> Ce3+ conversion is explained by a charge transfer from Sn atoms to unoccupied orbital Ce 4f(0) of cerium oxide by forming Ce 4f(1) state. XPS and SIMS revealed a formation of a new chemical Ce(Sn)(+) state, which belongs to SnCeO2 species. (C) 2009 Elsevier B. V. All rights reserved.