Influence of background oxygen pressure and post - deposition annealing on the structural, morphological, optical and luminescence properties of laser ablated SrWO4 thin films

Poly-crystalline strontium tungstate films with tetragonal scheelite phase were prepared on quartz substrate using pulsed laser ablation technique at different background oxygen pressures. These films were then post-annealed at a temperature of 800 degrees C for 2 h in air. The films prepared under oxygen ambience show a textured nature with preferred direction of crystal growth along < 004 >. The low value of FWHM of the XRD peaks exhibited by the annealed films compared to that of the as-deposited films suggests an enhancement in crystalline quality of the films with annealing. AFM and FESEM micrographs show that the morphology of the as-deposited films exhibit a tendency to form bigger clusters whereas the annealed films depict a dense distribution of grains. The films prepared under oxygen ambience show higher values of transmittance compared to those prepared in oxygen free ambience. All the films show luminescence emission similar to 388 nm and 468 nm region originating from lattice defects and surface defects respectively. The chromaticity diagrams show that the CIE coordinate of the films are very close to blue light region, suggesting the suitability of these films for the fabrication of blue light emitting device applications.