Effect of annealing temperature and thickness on the structural and optical properties of strontium bismuth niobate films

Abstract

Strontium Bismuth Niobate (SBN) thin films were prepared by metal organic decomposition method. The effects of post deposition annealing temperature (500–900 °C) and thickness (200–650 nm) on the structural and optical properties have been discussed. X-ray diffraction studies indicate the formation of single phase structure at annealing temperature of 800°C. The crystallinity of the samples improved with the increase in film thickness (200–500 nm), however, structural changes were observed beyond film thickness 500 nm. The changes in surface morphology of the films have been discussed as a function of annealing temperature and thickness. Although well-defined Raman spectra were obtained at higher annealing temperature (≥700 °C) for low thickness film, low frequency Raman modes were observed for higher thickness film (≥500 nm). The optical transmittance of the film decreases with increase in thickness from 200 to 650 nm. The energy band gap and refractive index have been estimated as a function of annealing temperature and film thickness. The band gap values decreased from 4.38 to 3.88 eV with the increase in film thickness. The correlation between structural and optical properties has been done in order to optimize annealing temperature and film thickness at 800 °C/ 500 nm.