Structural, optical, and electrical properties of indium tin oxide films with corundum structure fabricated by a sol-gel route based on solvothermal reactions

This article reports on the fabrication of the Sn-doped In2O3 (ITO) films with corundum structure by a sol-gel route, using InCl3.4H(2)O, SnCl4 and de-ionized water as starting materials. Based on the hydrolysis of In3+ and Sn4+ a solvotherinal system using ethylenediamine as solvent, the aqueous sol was prepared, and acted as the precursor of the ITO films. The films were coated on quartz glass by the dip coating process, and annealed in air in the range of 350-750 degrees C, The structure, morphology, and composition of the films were investigated by X-ray powder diffraction, electron diffraction, transmission electron microscopy, scanning electron microscopy, and X-ray photoelectron spectrometer, indicating that the films were composed of ITO nanoparticles with corundum structure. The spectral transmittance of the films was measured in the wavelength range of 250-950 nm using an UV-vis spectrophotometer. The electrical resistivity of the films was measured by the four-probe me hod at room temperature. It was found that the optical and electrical properties of the films were affected significantly by the annealing temperature in the range of 350-580 degrees C due to the improvement of the crystallinity of the films with increasing temperature, and became stable when the annealing temperature was higher than 580 degrees C. The 6.8 at.% Sn-doped film annealed at 680 degrees C had high transmittance above 78% in wide visible range with maximum of 83% at 875 nm wavelength, and showed the lowest resistivity of 2.0 x 10(-2) Omega cm. (C) 2002 Elsevier Science B.V. All rights reserved.