Influences of the [(Ba,Sr)TiO3]-modified RuO2 interface on the dielectric constant and current-voltage characteristics

The electrical properties of (Ba,Sr)TiO3 (BST) thin films on modified RuO2 electrodes were investigated. The surfaces of rf magnetron sputtered RuO2 electrode were modified by rf plasma etching, O-2 annealing, and overlayer coating of Pt. BST thin films were deposited on the various electrodes at identical conditions. There was no significant influence of the surface roughness on the phase formation and columnar, hillock-free, and dense BST films were obtained in all cases. BST films on different electrodes showed analogous dielectric constant when the effective electrode area was considered in calculation. But the roughened surface having large charge accumulation area is advantageous for carrying larger charge storage capacity. The leakage current of the BST film on RuO2 electrode without any modification at 1.5 V was 5.06 X 10(-5) and it increased to 7.92 x 10(-5) and 1.07 X 10(-4) A/cm(2) for the BST films on annealed RuO2 and rf plasma etched RuO2, respectively. The BST film on Pt/RuO2/SiO2/Si showed the lowest leakage current of 9.64 X 10(-7) A/cm(2) The Schottky barrier height acquired from the temperature dependence of I-V characteristics turned out to be 0.94, 0.79, 0.72, and 1.65 eV for the interface between the BST film and the RuO2 reference, rf plasma etched RuO2, annealed RuO2, and Pt(50 nm)/RuO2. (C) 1997 American Vacuum Society.