Investigation of silver doping on structural, optical and electrical properties of spray deposited tungsten trioxide thin films

Abstract

The spray pyrolysis technique is used to synthesize un-doped tungsten trioxide (WO3) and silver (Ag) doped WO3 thin films onto the glass substrate at 450 C. The surface morphology and the structural, optical and electrical properties of Ag doped as-prepared WO3 thin films with doping concentrations of 2, 4, 6, 8 and 10 at.% have been investigated by the Field-Emission Scanning Electron Microscopy (FESEM), X-ray Diffraction (XRD), UV-Visible spectroscopy (UV-vis) and four-point probe resistivity measurement. The FESEM investigations of un-doped and Ag doped WO3 films have shown grain formation with the crack surface. The XRD pattern of un-doped and Ag doped WO3 thin films has confirmed the monoclinic structure. The observed results have shown that the thin films with high crystallinity and Ag substitution effect lead to an increase of crystallite size. Higher Ag concentration has shown a different nature. The optical properties have been studied in the wavelength range of 300-1000 nm. The calculated band gap for un-doped WO3 is found at 3.20 eV and 2, 4, 6, 8 and 10.% Ag doped WO3 thin films are 3.15, 3.07, 2.95, 2.90 and 3.02 eV, respectively. The electrical properties have shown that the resistivity of WO3 decreased with increasing doping concentrations of Ag and gradually decreased with the increase of temperature. All the samples of thin films are reflected the semiconducting nature. The activation energy is calculated with higher and lower temperature regions. An overall analysis has indicated that Ag doped WO3 thin films are potential candidates for optoelectronic device applications.