Low frequency and microwave performances of Ba0.6Sr0.4TiO3 films on atomic layer deposited TiO2/high resistivity Si substrates

Abstract

We report on high tunablity of Ba0.6Sr0.4TiO3 (BST) thin films realized through the use of atomic layer deposited TiO2 films as a microwave buffer layer between BST and a high resistivity (HR) Si substrate. Coplanar waveguide (CPW) meander-line phase shifters using BST/TiO2/HR-Si and BST/MgO structures exhibited a differential phase shift of 95 degrees and 24.4 degrees, respectively, at 15 GHz under an electric field of 10 kV/cm. The figure of merit of the phase shifters at 15 GHz was 30.6 degrees/dB for BST film grown on a TiO2/HR-Si substrate and 12.2 degrees/dB for BST film grown on a MgO single crystal substrate. These results constitute significant progress in integrating BST films with conventional silicon technology.