Optical and electrical properties of transparent conductive ITO thin films deposited by sol–gel process

Abstract

Indium tin oxide (ITO) thin films have been deposited onto quartz glass substrates by a sol–gel process. The starting solution was prepared by mixing indium chloride dissolved in acetylacetone and tin chloride dissolved in ethanol. 0–20% by weight Sn-doped indium oxide (ITO) films were prepared by heat-treatment at above 400°C. The electrical, optical and structural properties of ITO thin films were investigated. The thickness of ITO film was measured by ellipsometer. The electrical resistivity was measured by using four-point probe method. The ITO thin films containing 10 wt.% Sn showed the minimum resistivity of ρ=1.5×10 −3 Ω-cm. The spectral transmittance of ITO thin films was measured in the wavelength range from 275 to 900 nm by a UV-vis spectrometer. The film has high transmittance above 80% and has an absorption edge at 300 nm. X-Ray diffraction measurements employing CuKα radiation were performed to determine the crystallinity of the ITO films which showed that the ITO films were polycrystalline with a cubic bixbyite structure. XRD results show that a single phase is detected for In-Sn oxide and X-ray photoelectron spectroscopy (XPS) results show that a single valence state and chemical bonding state is observed for In and Sn in In-Sn oxides. Therefore, we can say that Sn is incorporated into the In 2O 3 structure substitutionally.