Tailoring the UV–visible reflectivity range of VO2 thin films

Abstract

• Facile doping method of VO 2 films with TiO 2 nanoparticles. • Ultraviolet–visible spectral operating range of VO 2 sensitive to TiO 2 doping. • Gaussian and Lorentzian oscillators adequately describe the experimental data. • Doping level changes size and morphology of agglomerates in thin films. A simple chemical method for the tunability of the optical properties of TiO 2 nanoparticles-doped VO 2 thin films is reported. Although deposited thin films revealed granular morphology, an increase in dopant concentration showed increased homogeneity (smaller crystallite size). The insulator-to-metal transition, monitored by UV–vis-NIR reflectivity, is adjusted through a simple model based on a sum of Lorentzians and Gaussians to follow the changes in the optical spectra, which in turn allows us to extract the corresponding refractive index and extinction coefficient. In addition, the reflection spectrum in low frequency range ( < 700 nm), reveals new variations in the doped samples triggered by the changes in temperature, which allows an extended optical operating range, for instance, in smart windows applications.