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

Abstract

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 SnO2 phase was not detected in terms of XRD, TEM analysis techniques and the resultant phase was only In2O3 cubic bixbyite. The sheet resistance of 250 nm thin films annealed at 400 degrees C was 6.18 x 10(3) Ohm/rectangle in air, 1.09 x 10(3) rectangle/Ohm in nitrogen, 15.21 x 10(3) Ohm/rectangle 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 Angstrom for a 50 nm film and 25 Angstrom for a 350 nm film, respectively. XPS results revealed that Sn was incorporated into In2O3 structure substitutionally. (C) 1999 Elsevier Science S.A. All rights reserved.