Measurements of the admittance of Ag/TiW-(Ti-V-Pd) oxide-Si structure as a function of frequency at fixed measurement conditions (i.e. gate voltages, temperature, humidity and light illumination) have been performed and a large dispersion in the measurement results has been observed. The analysis of experimental spectra on the basis of electrical equivalent circuit model, consisting of resistors, capacitors and constant phase elements, has enabled us to identify three relaxation processes attributed to the physical phenomena in different regions of the examined structure. (c) 2005 Elsevier B.V. All rights reserved.