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Abstract In this research, In2O3, SnO2 and 10 SnO2 90 In2O3 ITO thin films were deposited on glass substrates using thermal evaporation technique. The thickness and deposition rate for all the samples are 220 nm and 0.1 nm/s, respectively. The optical properties of the layers were investigated at annealing temperature of 300 ℃. In this study, all annealed samples indicate high transmittance in the visible wavelength region. The highest transmission for the annealed layers is 91 which is related to the SnO2. Refractive indexes of different samples n at a wavelength of 550 nm are in the range of 1.88-1.92. Also, the effect of adding SnO2 as impurity to In2O3 on physical properties of these films were investigated. X-ray diffraction results show that In2O3 and In2O3 doped with tin layer have a polycrystalline structure and are crystallized in the cubic structure. Finally, the influence of nanoparticles of SnO2, In2O3 and ITO for sensing ethanol vapor as an application of transparent semiconductor oxides is discussed. The results show a high sensitivity of SnO2 films compared to the In2O3 and ITO films for detecting ethanol vapor.