Spectroscopic ellipsometry study of thin film thermo-optical properties

Spectroscopic ellipsometry (SE) was employed to realize in-situ monitoring and the determination of thermo-optic coefficients (TOC) of thin films by integrating a temperature controlled hot stage to the ellipsometer and applying the empirical relationship of Cauchy between the refractive index and wavelength in the data analysis. Magnetron sputtered titanium oxide thin films of 350 nm thick both as-deposited and post-deposition annealed were prepared on silicon wafers for this investigation. Results of ellipsometric analysis show that as-deposited TiO₂ films have a negative TOC of ? 1.21 × 10^? 4 K^? 1 at 630 nm over the test temperature range 304–378 K. The post-deposition annealing at 923 K for 2 hours leads an increase in film refractive index to 2.29 from 2.17 for as-deposited TiO₂ films, and an enhancement in TOC up to ? 2.14 × 10^? 4 K^? 1. X-ray diffraction (XRD) and scanning electron microscopy (SEM) cross-sectional analysis were performed for film structure characterization.