Effect of UV Treatment on Structure and Optical Properties of Spin-Coated TiO2:Ag Thin Films

In this work, the impact of UV (ultaviolet) radiation combined with thermal treatments and Ag doping in TiO2 transparent films on crystal structure and light absorption in the visible spectral region is investigated. The nanostructured TiO2:Ag films were obtained via sol–gel spin-coating deposition, using UV radiation between layers. The substrates used were quartz and silicon wafers. X-Ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy revealed that the structural features of TiO2:Ag films were strongly dependent on the annealing temperatures. The presence of Ag nanoparticles and a small silver oxide fraction in the film structure was found. The formation of AgO and Ag nanoparticles is affected by thermal annealing and the UV radiation treatment. The transmittance, absorbance and reflectance spectra were used for determining the optical behavior and localized surface plasmon resonance (LSPR) properties of TiO2:Ag thin films. Optical characterization revealed increased optical absorption in the whole visible range of TiO2 thin films with incorporated Ag NPs. The dependence of the plasmonic absorption bands, the values of the optical band gap on the number of layers (from one to five) and the high-temperature treatments (from 150 to 800 °C) were studied.