Spray-deposited nanocrystalline WO3 thin films prepared using tungsten hexachloride dissolved in N-N dimethylformamide and influence of in doping on their structural, optical and electrical properties

Abstract

Undoped and In-doped nanocrystalline tungsten oxide (WO3) thin films were prepared by chemical spray pyrolysis using tungsten hexachloride (WCl6) dissolved in N-N dimethylformamide as the host precursor solution and indium chloride (InCl3) as the source of dopant. XRD analyses confirm the monoclinic phase of the prepared films with the predominance of triplet (002), (020) and (200) in the spectra. On indium doping, the crystallinity of the films decreases and becomes minimum at 1.5 at. % doping. EDX analyses confirm the incorporation of In dopants into the WO3 lattice network. SEM micrographs show nonspherical grains over the surface and the average grain size decreases with higher In doping. AFM images of the films exhibit large nicely separated conical columnar grains (except in 1 at. %) throughout the surface with coalescence of some columnar grains at few places. UV-visible measurements reveal that the optical transmittance of the 1 at. % In-doped film increases significantly throughout the wavelength range 300–800 nm relative to that of the undoped film. Room temperature photoluminescence spectra show pronounced enhancement in the peak intensity of NBE emission on In doping. Electrical conductivity has been found to increase on In doping.