Conduction through TiO 2 thin films with large ionic space charge

Abstract

The electrical properties are described for thin film sandwiches of AlTiO 2Al with films varying in thickness from 100 to 410 Å. The results are interpreted in terms of a large ionic space charge in the TiO 2 films. By selecting a sample of appropriate thickness, it was possible to make a detailed comparison of the experimental results with the theory of the preceding paper. (1) Using the barrier energies at the two electrodes determined independently from photoelectric measurements and adjusting a single parameter, the characteristic temperature T 0, to the results, we obtain good agreement for the dependence of both current and capacitance on voltage and temperature. From the value of T 0 so determined we calculate a maximum ionic space-charge density adjacent to the electrode interfaces of approximately 5 mole per cent which conforms with typical values of saturation concentrations of impurities quoted for TiO 2. The dependence of conductance and capacitance on frequency is also considered and shown to be in qualitative agreement with the theoretical model.