Enhanced electrical and optoelectronic properties of W doped SnO2 thin films

In the present study, undoped tin oxide (SnO2) and tungsten (W) doped tin oxide (1, 2, 3, 4 and 5 wt% of W doping) thin films were deposited by the homemade spray pyrolysis technique and their structural, microstructural, optical, electrical, and optoelectronic properties are described. X-ray diffraction analysis confirmed that all the prepared thin films belonged to a tetragonal crystal structure with a space group of P42/mnm. The elemental oxidation state of Sn4+, O2− and W6+ was confirmed by the X-ray photoelectron spectroscopy (XPS) analysis. The scanning electron microscopy revealed that the surface morphology of SnO2 thin films was slightly modified by W doping. The presence of Sn, O and W and their elemental compositions were confirmed using the energy dispersive X-ray spectroscopy. The 3 wt% of W doped SnO2 (SnO2:W) thin films showed maximum optical transmittance of about 90% in the visible and NIR region. The direct optical bandgap varied between 3.60 eV and 3.84 eV. Photoluminescence spectra showed noticeable enhancement in the UV emission peak at 362 nm and green emission peak at 525 nm of SnO2:W thin films. The high charge carrier concentration of 2.89 × 1020 cm−3 was observed for 3 wt% of W doping. The Hall mobility of the undoped SnO2 thin films was found to be 94 cm2/Vs. A high figure of merit of 8.30 × 10−3 Ω−1 was obtained for the thin films doped with 3 wt% of W.