Characterization of transparent conductive ITO thin films deposited on titanium dioxide film by a sol–gel process

Abstract

Indium tin oxide (ITO) thin films have been deposited on titanium dioxide film by a sol–gel process. The starting solution was prepared by mixing indium chloride dissolved in acetylacetone and tin chloride dissolved in ethanol. ITO thin films containing 0–20% Sn by weight were successfully prepared by heat treatment at above 400°C. The resistivity of ITO films has been minimised by optimising the tin doping concentration in the solution. The electrical, optical and structural properties of ITO thin films were investigated. The thickness of ITO films was measured by ellipsometer. The electrical resistivity was measured by using the four-point probe method. The ITO thin films containing 10 wt.% Sn showed a minimum resistivity of ρ=9.5×10 −4 Ω cm. The spectral transmittance of ITO thin films was measured in the wavelength range 200–900 nm by a UV-vis spectrometer. Films with a thickness of 250 nm have a high transmittance of 90% at 900 nm. X-Ray diffraction measurements employing CuKα radiation were performed to determine the crystallinity of the ITO films, which showed that they were polycrystalline with a cubic bixbyite structure.