Temperature-Dependent Spectroscopic Ellipsometry and Modeling of the Optical Properties of Vanadium Dioxide Thin Films

The metal–insulator transition of vanadium dioxide (VO2), a phase change material, has been utilized for various applications. The characterization of the VO2 thin film structure, in both its optical properties and thickness, remains a critical problem. In this paper, VO2 thin films were fabricated on silicon substrates by magnetron sputtering. By using temperature-varying spectroscopic ellipsometry, VO2 thin films of different thicknesses were characterized in an energy range of 0.5–3.0 eV, and the phase change temperature was determined using ellipsometry data. The optical properties of these samples were determined from temperature-dependent ellipsometry measurements by using the Drude and multiple Tauc–Lorentz model. Broadband temperature-dependent reflectivity spectra were obtained. An analysis of the samples revealed that their bandgaps, plasma frequencies, and other modeling parameters demonstrated a pattern of change with increasing temperature, which could be explained by the underlying physics. This study will help with the design of VO2-based structures for a broad range of applications.