Effects of nozzle-to-substrate distance and annealing atmospheres on V2O5 thin films prepared by spray pyrolysis technique

In this research, vanadium pentoxide (V2O5) thin films were prepared on glass substrates by spray pyrolysis technique and the effect of nozzle to substrate distance (NSD) was investigated. The field emission Scanning electron microscope (FESEM) images and EDX analysis indicated the formation of nano-grains that improved their stoichiometry with increasing NSD. The XRD and Raman spectra showed that structural properties (orthorhombic/tetragonal phases) depend on NSD. The analysis of optical transmittance spectra revealed that with increasing NSD the direct band gap of the samples is increased from 2.27 to 2.60 eV due to improvement of chemical stoichiometry and crystalline phase change of the layers. Finally, sample with weak tetragonal phase was annealed in various atmospheres (N-2, air and O-2). We found the atmosphere of annealing process had profound effect on morphological, structural and optical properties of the as-grown sample.