Schottky junctions have been realized by evaporating gold spots on top of sexithiophen (6T), which is deposited on TiO2 or ZnO with e-beam and spray pyrolysis. Using Mott-Schottky analysis of 6T/TiO2 and 6T/ZnO devices acceptor densities of 4.5 x 10(16) and 3.7 X 10(16) cm(-3) are obtained, respectively. For 6T/TiO2 deposited with the e-bearn evaporation a conductivity of 9 x 10(-8) S cm(-1) and a charge carrier mobility of 1.2 x 10(-5) cm(2)/V s is found. Impedance spectroscopy is used to model the sample response in detail in terms of resistances and capacitances. An equivalent circuit is derived from the impedance measurements. The high-frequency data are analyzed in terms of the space-charge capacitance. In these frequencies shallow acceptor states dominate the heterojunction time constant. The high-frequency RC time constant is 8 mu s. Deep acceptor states are represented by a resistance and a CPE connected in series. The equivalent circuit is validated in the potential range (from -1.2 to 0.8 V) for 6T/ZnO obtained with spray pyrolysis.