The CeOx/Al2O3 thin films on stainless steel with different ceria loading were subjected to a.c. (square wave) pulses at various frequencies in the range 10- 3 to 100 kHz while recording X-ray photoelectron spectra. The resulting binding energy differences were derived from the frequency dependence of the corresponding Al2p, Ce3d and O1s peaks. At low ceria loadings the main constituent on the surface is CeAlO 3 phase, while for high ceria loading the film is constructed from CeO2 and CeAlO3 phases spread over the Al 2O3. Accordingly, it was observed that the ceria loading determines the conductivities of the investigated thin oxide films.