Thin films of CeOx are radio frequency magnetron sputtered on n-type (100) Si wafers from CeO2 target. Structural investigations of CeO2/Si system after rapid thermal annealing (RTA) in the range of 800-1300 degrees C are presented. As-grown films are a mixture of amorphous and polycrystalline phases Of CeO2, CeO3 and SiO2. Structure and phase composition of the films after RTA treatment are strongly time and temperature dependent. Complete transition from amorphous to polycrystalline phase is observed after RTA treatment at 1100 degrees C for 180 s. A-rising of Ce-Si interlayer is assumed for these conditions. Formation of p-n junction is observed at elevated RTA temperature of 1300 degrees C. (c) 2007 Elsevier B.V All rights reserved.