Effects of zinc doping on structural, morphological, optical and electrical properties of SnO2 thin films

Abstract

The aim of the present study was to deposited and characterized Zn-doped SnO2 thin films for different weight concentrations (wt.%) 0, 3, 5 and 7% produced by spray pyrolysis. The characterization by XRD showed that the layers are polycrystalline in nature, with tetragonal structure of rutile type due to the presence of intense peak of orientation (110) located around the angle 26° for all the films produced. The variations in FWHM and the crystallite size were very well correlated. The SEM micrograph shows a relatively dense and smooth surface exhibited by the 3 wt.% doped film. This result can be explained by considering the following reasons: the substitution of the Sn+4 cations for the Zn+2 cations facilitate, the crystallite size increase and the decrease in defects. The contact angles measured using water droplets were less than 90° for all the films produced, which proves the hydrophilic characteristic of the films, meanwhile the film doped with 3 wt.% Zn had a high contact angle (88.09°). This result suggests that a doping concentration equal to 3 wt.% Zn can be considered as a critical concentration in changing the surface morphology of the Zn-doped SnO2 films produced. The analysis by UV-visible spectrophotometer showed a transmittance varying between 76 to 87% depending on the doping. The 3 wt.% Zn-doped SnO2 film was found to have high transmittance (87%) and better optical property with minimum resistivity (ρ = 0.044 Ω cm) among the deposited films. This work demonstrated that the 3 wt.% Zn-doped SnO2 film improves the physical properties of the SnO2 film, allowing it to be integrated into the optoelectronic device.