Structural, electrical and optical characterization of fe and zn doped tio2 thin films prepared by spray pyrolysis technique

Abstract

Pristine and TiO2 thin films with Fe and Zn doping are successfully synthesized by a simple and cost effective spray pyrolysis technique (SPT). The as grown thin films are deposited on commercial glass slides at a substrate temperature of 450ºC using titanium (IV) butoxide as the Ti precursor. All synthesized thin films have been characterized as a function of Fe and Zn content, changing from 0, 2, 4, 6, 8 at.% by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Energy dispersive X-ray (EDX), and UV–Vis spectroscopy (UV–Vis). The XRD shows crystallinity of highly oriented tetragonal TiO2 films with the strong characteristic peaks. The value of the crystallite size is estimated to be about 31.82 nm for undoped TiO2. After doping Fe as an impurity metal, the crystallite size reduces from 31.82 to 17.26 nm. FESEM images display that the surfaces are fibrous in nature and nanofibers are observed around the nucleation center. The existence of Fe dopant and other compositional elements in both pristine and doped films are confirmed observing corresponding peaks in the EDX analysis. The Fe doped thin films exhibit high transparency almost 80% maximum transmittance in the visible and near-infrared wavelength. The band gap ascertains from transmittance data is in the range of 3.81-3.69 eV with the increase of Fe content. The Fe doping in TiO2 thin films results a significant effect on the electrical resistivity. The XRD result of Zn doped TiO2 indicates that all of the films are crystalline with the tetragonal crystal structure of anatase TiO2. In pure TiO2, film the crystallite size is found to be 31.82 nm, which decreases drastically to 9.95 nm for Zn doped TiO2 film. It is observed that the Zn doped TiO2 films are uniform without cracks and voids and with dense morphology. The films are highly transparent in the visible and near infrared regions of the electromagnetic spectrum with an average transmittance value up to 80 %. The evaluated band gaps are 3.81 eV, 3.84eV, 3.83 eV, 3.81 eV and 3.75 eV for Zn= 0, 2, 4, 6 and 8 at.% doped TiO2 films respectively. Electrical properties show that the deposited films are semiconducting in nature.