Influence of oxygen to argon ratio on the properties of RF magnetron sputtered Ba0.7Sr0.3TiO3 thin films

Abstract

The optical properties of thin films of barium strontium titanate (BST) are important due to its wide band gap, high refractive index and low absorption coefficient and hence find application in electro-optic and non-linear optical devices. Ba0.7Sr0.3TiO3 (BST) thin films were deposited by RF magnetron sputtering on fused silica and Pt/TiO2/SiO2/Si (PtSi) wafers at relatively low substrate temperature. The crystallisation of thin films strongly depends on O-2/Ar ratio in the sputtering gas. The optical parameters like band gap (E-g), refractive index (n) were studied as a function of oxygen to argon ratio in the sputtering gas. The electrical properties of BST thin films deposited on PtSi substrates as a function of O-2 to Ar ratio has also been studied. The films show 50% tunability with a minimum loss of 0.018 at 1 MHz when grown at the optimized O-2 to Ar ratio.