Correlation between structural and optoelectronic properties of tin doped indium oxide thin films

Spin coating method was employed to deposit the thin films using redispersed nanoparticle suspensions of tin doped indium oxide (ITO). These films were then annealed in air at 450, 500, 550, 600, and 650 °C for 1 h. The effect of annealing temperature on the structural, optical, morphological, and electrical properties were studied by XRD, UV-vis spectroscopy, SEM, and four point probe technique, respectively. XRD analysis revealed that all thin films have cubic bixbyite structure with dominant (2 2 2) plane. Williamson-Hall analysis of XRD patterns showed that crystallite size increases with the rise in annealing temperature. SEM images of ITO thin film depicted spherical and non-spherical shaped particles of uneven size. The transmission spectra obtained from UV-vis spectroscopy reveals that transparency of thin films undulate with annealing temperature. With the rise in annealing temperature the optical band gap increases, while the Urbach energy and electrical resistivity decreases. The optical band gap, Urbach energy, and electrical resistivity were found to have systematic dependence on the crystallite size. The figure of merit is maximum for ITO thin film annealed at 550 °C.