Influence of laser fluence on structural, optical and microwave dielectric properties of pulsed laser deposited Ba0.6Sr0.4TiO3 thin films

Abstract

Barium strontium titanate Ba0.6Sr0.4TiO3 (BST6) thin films are deposited by pulsed laser deposition method at different laser fluences keeping the oxygen pressure constant. X-ray diffraction analysis confirms the formation of single phase cubic BST6 thin films. The strain in the grown films have been investigated, and the results show that the strain is in increased under the application of varying laser fluences. It can be inferred that the laser fluence is an important parameter in tuning the dielectric/ferroelectric properties of the films under optimized conditions. The thin films microstructures have been studied using HRTEM, and the results shows the presence of (110) faceted planes of BST6 with dspacing ~ 2.72–2.79 A. The optical band gap of the BST6 thin films was calculated by applying the Tauc relation from the transmission spectra in the 190–2500 nm range. The BST6 thin films grown at 2 J cm−2 which shows the best microstructural and optical properties was selected for the microwave dielectric measurements by depositing a test circular patch capacitor. The microwave tunability and dielectric constant (er) of a well crystallized BST6 thin film were found to be ~ 56 and ~ 284%, respectively at 1 GHz making it suitable for applications in tunable microwave devices.