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

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 show insulating behaviour with a low leakage current. A rectifying current–voltage characteristic is obtained by replacing the top electrode with ITO. As shown by photoemission as well as by electrical measurements, the property of the BST/ITO interface depends strongly on the deposition sequence, and can be related to the level of oxidation of the ITO film. Highly doped ITO as top electrode forms an Ohmic contact with BST. This enables the preparation of highly rectifying diodes that exhibit a space–charge-limited current behaviour. Larger barriers are obtained when ITO is used as bottom electrode. This is related to the oxidation of the ITO layer during BST deposition and results in a low interface-limited current. Due to the large energy gaps of both BST and ITO, the combination of these materials provides an additional route to transparent electronics.