Thermal properties of TiO2 films fabricated by atomic layer deposition

Abstract

Thin, amorphous, high index, dense, low scattering & absorption (low extinction coefficient) and optical grade TiO2 films of various thicknesses are prepared by Atomic layer deposition (ALD) technique and investigated in terms of thermo-optic coefficient (dn/dT) and temperature dependent density (dρ/dT). The dρ/dT and dρ/dT are calculated by modeling ellipsometric experimental data by developing appropriate optical model such as Cauchy Model. The modeled data was further modeled with Lorentz-Lorenz relation under least-square approach. The dn/dT of TiO2 films shows negative values for thin and positive values for relatively thicker films and reveals no significant changes in dn/dT and dρ/dT when film thickness increases more than ∼ 200 nm. The coefficient values are calculated for a wavelength range of 380-1800 nm. The average values of (dn/dT)60nm= -4.2 ± 0.7 × 10-5°C-1 and (dρ/dT)60nm= -6.6 ± 1.1 × 10-5gcm -3 °C-1 at wavelength of 640 nm. The reported coefficients values are measured and calculated for TiO2 film of thickness t 60 nm and described in detail. © Published under licence by IOP Publishing Ltd.