The Effect of Annealing on Structural, Optical and Electrical Properties of Nanostructured Tin Doped Indium Oxide Thin Films

Mohammad Hossein Habibi* and Nasrin Talebian
Department of Chemistry, University of Isfahan, Isfahan, 81746-73441, Ira

Abstract
A low level tin doped indium oxide, ITO, (ca. 10 w % SnO₂) thin films were prepared on glass substrate by electron beam technique. Deposited films with deposition rate of 0.1–0.25 nm s^–1 were annealed at different temperatures from 250 to 550 °C in air. The thin films were characterized using low and high angle X-ray diffraction and UV-visible spectroscopy. The lattice constant and the grain size of ITO thin film were 10.118 Å and 36 nm, respectively. UV-visible transmission spectra confirmed the formation of high quality ITO nano-particles. These low level tin doped indium oxide thin films showed higher transparency over the visible wavelength region (ca. 95%) than those of already reported with higher level tin doped indium oxide thin films deposited at 350 °C. The transmission data were used for direct and indirect optical band gap calculations ca. 3.6 and 3.8eV, respectively. The refractive index and porosity of ITO films annealed at different temperature were calculated from measured transmittance data. The results showed that the refractive index of thin films increased with increasing annealing temperature, but the porosity of ITO thin films showed opposite trend. The lowest resistivity (2.9 ×10^–6 Ω m) and highest porosity (40.1%) were obtained for the annealed film at 550 °C.

Keywords: Nanostructure ITO, low and high angle XRD, UV-visible transmission spectra, annealing, electron beam evaporation.