Thickness influence on optical and electrochemical properties of dititanium trioxide (Ti2O3) films deposited on glass substrates by electron beam gun evaporation

Dititanium trioxide (Ti2O3) films with thickness between 13 and 100nm on glass substrates were prepared by electron beam gun evaporation at low temperature. They were characterized by transmittance absorbance and reflectance curves. The optical properties of film include band gap calculation, band to band transitions and electrochemical polarization in phosphate buffer solution were studied. The films produced have fairly high transmittance >62% between 330 and 400nm wavelength region which was decreased by films thickness increasing. The films also showed poor transmittance below 330nm but have good absorbance in the UV region. Furthermore, these films have good reflectance >67% between 400 and 800nm wavelength region which was increased by films thicknesses increasing. By plotting the Taue plot ((αhυ)n Versus hυ) for Ti2O3 films, we also found that the band to band indirect transitions were most probable than the direct transitions by films thickness increasing. Band gaps of 4.08eV for allowed direct transition and 3.81eV for allowed indirect transition for the thinnest film were also obtained. Electrochemical polarization of Ti2O3 films in phosphate buffer solution (pH 7) results showed higher current for thinner films. Schottky barriers were produced for both films (13 and 30nm in thickness) in contact with aqueous solution