Depletion layer thickness and Schottky type carrier injection at the interface between Pt electrodes and (Ba, Sr)TiO3 thin films

The electrical conduction properties of rf sputter-deposited (Ba, Sr)TiO3 ( BST) films on Pt and IrO2 electrodes and metalorganic chemical vapor deposi ted (MOCVD) BST films on a Pt electrode were investigated and a new energy band model that satisfactorily explains the observed leakage current charac teristics and film thickness dependent dielectric properties is proposed. T he BST and Pt junction constituted a blocking contact with interface potent ial barrier heights of 1.6-1.7 eV and 1.2 eV for the sputtered and MOCVD fi lms, respectively. Schottky emission behavior was observed at measurement t emperatures higher than 120 degrees C and tunneling related conduction beha vior appeared below that temperature for a film thickness of 40 nm. A parti al depletion model with a very thin (about 1 nm) layer devoid of space char ge at the interface with the Pt electrode is proposed to explain the V-1/2 dependent variation of ln(J(0)) as well as the decreasing dielectric consta nt with decreasing film thickness. (C) 1999 American Institute of Physics. [S0021-8979(98)04920-2].