Study of structural and optical properties of sprayed WO3 thin films using enhanced characterization techniques along with the Boubaker Polynomials Expansion Scheme (BPES)

In this study, WO3 thin films were grown on glass substrates using an aqueous solution containing tungstate (NH4)2WO4 as precursor. The substrate temperature incremented from 250 to 500 deg. C, by steps of 50 deg. C. The structural properties were investigated using XRD, atomic force microscopy and scanning electronic microscopy techniques. Microprobe analyses showed that a balanced stoichiometric composition was obtained for thin films prepared at Ts = 350 and 400 deg. C. The X-ray diffraction analyses showed different structure crystallography in function of the substrate temperature. Moreover, films deposited at 400 deg. C were annealed in air for 2 h at 450 and 500 deg. C, respectively and the structural changes due to heat treatment were studied. Finally, the optical properties of these films were carried out using optical measurements of transmittance T(λ) and reflectance R(λ) spectra in 300-1800 nm domain. The refractive and absorption indexes, n and k were calculated. The band gap energy value was found lying in 2.6-3.6 eV domain.