Interface properties between SrTiO₃ thin films and electrodes

SrTiO3 (STO) thin films were grown by pulsed laser deposition on single crystal STO substrates with a SrRuO3 buffer layer, which also serves as a bottom electrode. Measurements of the low frequency dielectric properties were performed in a parallel plate capacitor configuration for a range of temperatures using different top electrode materials. The contribution to the interfacial potential from Schottky barriers was investigated. In comparison to STO single crystals, thin films have continued dielectric non-linearity above T approx. 70 K. This complicates conventional Schottky barrier height measurements using C-V curves because both Schottky barriers and dielectric non-linearity result in a decrease in dielectric constant under applied electric fields. However, by using I-V data, difficulties related to field dependence of the dielectric constant may be removed. Barrier height measurements for both metal and oxide electrodes were performed for T > 70 K. Calculated barrier heights from a modified Schottky equation were very low for an oxide electrode, and an order of magnitude higher for a normal metal electrode.