Transparent conductive ITO thin films through the sol-gel process using metal salts

The electrical and optical properties, structure and morphology of ITO thin films were investigated. Ten percent by weight Sn-doped indium oxide (ITO) films were prepared on soda-lime-silicate glass substrate by the sol-gel spin coating method using inorganic metal salts. All layers studied with a thickness range of 50–350 nm were polycrystalline with grain sizes in the range 20–30 nm depending on the annealing conditions. SnO or SnO 2 phase was not detected in terms of XRD, TEM analysis techniques and the resultant phase was only In 2O 3 cubic bixbyite. The sheet resistance of 250 nm thin films annealed at 400°C was 6.18×10 3 Ω/□ in air, 1.09×10 3 Ω/□ in nitrogen, 15.21×10 3 Ω/□ in oxygen, respectively. Four-hundred degree centigrade-annealed 150 nm films showed more than 85% of the average visible transmittance, regardless of annealing atmospheres. According to AFM analysis RMS roughness was 18 Å for a 50 nm film and 25 Å for a 350 nm film, respectively. XPS results revealed that Sn was incorporated into In 2O 3 structure substitutionally.