Structural, morphological and opto-electrical properties of transparent conducting SnO2 thin films: Influence of Sb doping

Pure and antimony doped tin oxide (Sb:SnO2) thin solid films were synthesised through a simple and low-cost nebulised spray pyrolysis (NSP) route. The influence of Sb doping on the different physical properties of these films was systematically investigated. The results of X-ray diffraction (XRD) study exhibited polycrystalline in nature of all films with tetragonal cassiterite structure of single phase SnO2. XRD analysis also revealed the reduction in crystallite size as well as the grain size observed in scanning electron microscopy (SEM) with Sb doping concentration. The average transmittance of all the films was greater than 73% at the visible wavelength region and the transparency was reduced by Sb inclusion. The direct optical band gap value was the lowest of 3.94 eV for pure SnO2 and enhanced by Sb doping level. The effects of Sb doping concentration on extinction coefficient, refractive index, dielectric constant, optical conductivity and optical density of the films were examined. Photoluminescence spectrum revealed a broad violet emission peak near 390 nm and Sb doping intensified the peak. Both the resistivity and sheet resistance were found to vary in the range of 1.61 × 10−3 Ω.cm to 3.92 × 10−4 Ω.cm and 32.73 Ω/□ to 134.41 Ω/□, respectively with the variation of Sb doping concentration. The highest mobility and carrier concentration were 54.74 cm2/Vs and 7.02 × 1021 cm−3 for undoped and 10% Sb doped films, respectively. However, the figure of merit was found to be maximum of 1.38 × 10−3 (Ω/cm2)−1 for 5% Sb doping concentration among the films.