Effects of interfacial roughness on the leakage properties of SrTiO3 thin film capacitors

Recent reports on the current-voltage (I-V) characteristics of SrTiO3 and (Ba,Sr)TiO3 thin film capacitors with Pt: electrode suggest that their leakage properties are controlled by Schottky emission from cathode. However, their dynamic permittivities obtained from the Schottky plot are always much smaller than those expected from optical measurements. The most plausible approach to explain this disagreement is to incorporate the effect of electric field enhancement due to interfacial roughness into the Schottky emission model. Electric field at the interface, for the first order approximation, can be given by [(r+t)/r](V/t), where r, t and V respectively denote radius of curvature representing interfacial roughness, dielectric thickness and applied voltage. This model predicts that I-V characteristics are the functions of r and V for the ultimate case of r << t. We have closely studied the I-V characteristics of sputter-deposited SrTiO3 films and have obtained the results which strongly support our prediction.