Electrical properties of (Ba, Sr)TiO3 thin films with Pt and ITO electrodes: dielectric and rectifying behaviour

Abstract

The electrical properties of (Ba, Sr)TiO3 (BST) thin films are studied using different combinations of Pt and tin-doped indium oxide (In2O3:Sn, ITO) as electrode material. With Pt as bottom and top electrode the films showinsulating behaviour with a low leakage current. A rectifying current–voltage characteristicis obtained by replacing the top electrode with ITO. As shown by photoemission as well asby electrical measurements, the property of the BST/ITO interface depends strongly on thedeposition sequence, and can be related to the level of oxidation of the ITO film. Highlydoped ITO as top electrode forms an Ohmic contact with BST. This enables thepreparation of highly rectifying diodes that exhibit a space–charge-limited currentbehaviour. Larger barriers are obtained when ITO is used as bottom electrode. This isrelated to the oxidation of the ITO layer during BST deposition and results in a lowinterface-limited current. Due to the large energy gaps of both BST and ITO, thecombination of these materials provides an additional route to transparent electronics.