Effect of annealing on the structural and optical properties of laser ablated nanostructured barium tungstate thin films

Abstract

High quality BaWO4 thin films are successfully deposited on quartz substrate for a duration of 30min using pulsed laser ablation technique and using a laser radiation of wavelength 355nm and the effect of thermal annealing on the structural and optical properties is studied by using techniques like X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy, micro-Raman, FTIR and UV–visible spectroscopy. All the films show monoclinic crystalline structure with (202) plane as the preferred orientation of crystal growth. From the XRD analysis it is found that the optimum annealing temperature for better crystallization of the BaWO4 film is 700°C and there is no phase change observed with annealing temperature. The presence of the characteristic bands for the BaWO4 in the Raman spectra of the films suggests the formation of BaWO4 crystalline phase in all the films. SEM and AFM analyses show that as the annealing temperature increases the connectivity between individual grains increases and shows an ordered packing. The geometrical optimization and energy calculation of the title compound were done using the Gaussian 09 software package and the calculations were carried out using the CAM-B3LYP functional combined with standard Lanl2Dz basis set. The thickness of the films was calculated using lateral SEM images and also from optical transmission spectral data using PUMA software.