Interfacial characteristic of (Ba,Sr)TiO3 thin films deposited on different bottom electrodes

Barium strontium titanate (Ba1−x Sr x )TiO3 (BST) thin films were deposited on Pt, Ru, RuO2, and Pt/RuO2 electrodes by radio frequency magnetron sputtering. The interfacial structure characteristic of the BST films deposited on various electrodes was investigated. X-ray photoelectron spectroscopy investigations showed that the interfacial diffusion layer in BST/Pt and BST/Ru are approximately 6 and 10 nm, respectively. The BST films are short of Ba and O elements comparing with the stoichiometry Ba0.65Sr0.35TiO3 in the interface region. Dielectric measurement of the BST films with thickness ranging from 70 to 400 nm revealed that the BST films deposited on Pt and Pt/RuO2 bottom electrodes have similar dielectric property, the BST films deposited on Ru have the highest bulk dielectric constant, and the thickness dependence of dielectric constant on the BST film deposited on RuO2 electrode can be neglected. The interfacial layer dielectric constant of BST films deposited on Pt and Ru electrodes are estimated to be about 34.5 and 157.1, respectively. The effect of interfacial dead-layer on the dielectric constant could be eliminated through selecting appropriate bottom electrodes.