Temperature-Dependent Optical Properties of Titanium Oxide Thin Films Studied by Spectroscopic Ellipsometry

The electron-beam evaporation method was devoted to fabricate anatase-phase TiO₂ thin films on silicon substrate. The optical constants of the thin films determined by spectroscopic ellipsometry in the spectral range from 300 to 800 nm were studied in a temperature range from 293 to 533 K. The refractive indices decrease apparently with increasing temperature, and the thermal expansion and electron-phonon interaction can be introduced to elucidate this phenomenon. The absorption edge in extinction coefficient spectra shows a redshift at elevated temperature, which is attributed to thermally driven band gap shrinkage and electron lifetime loss of optical electron transition.