Effects of annealing conditions on optical and electrical characteristics of titanium dioxide films deposited by electron beam evaporation

We report measured evolutions of the optical band gap, refractive index, and relative dielectric constant of TiO2 film obtained by electron beam gun evaporation and annealed in an oxygen environment. A negative shift of the flat band voltage with increasing annealing temperatures, for any film thickness, is observed. A dramatic reduction of the leakage current by about four orders of magnitude to 5×10−6 A/cm2 (at 1 MV/cm) after 700 °C and 60 min annealing is found for films thinner than 15 nm. An equivalent SiO2 thickness of the order of 3–3.5 nm is demonstrated. An approach is presented to establish that at different ranges of applied voltage the hopping, space charge limited current, and Fowler–Nordheim are the basic mechanisms of carrier transport into the TiO2 film.