Surface Plasmon Resonance Effect on the Optical Properties of TiO2 Doped by Noble Metals Nanoparticles

Nanocomposite thin films composed of a TiO2 matrix doped with noble metals nanoparticles (MNPS), Au and Ag, were deposited on Si (100) and glass substrates by dc magnetron sputtering. The samples were annealed in a protective atmosphere at temperatures ranging from 200 to 700 °C. The main goal of this work is to characterize and compare the Surface Plasmon Resonance (SPR) behaviour in both systems. The studies have been focused on the growth of the nanoclusters and on their role on the optical properties of the films. Size, shape and distribution of the nanoclusters embedded on the titanium oxide dielectric matrix are reported as key factors on the SPR behaviour in both systems (Au:TiO2 and Ag:TiO2). The MNPs grew due to diffusion mechanisms, which were led by the annealing treatments, even at the highest annealing temperatures. Evidences of the correlation between the nanocomposite film structural changes and the evolution of the optical properties due to the SPR activity are reported. The SPR phenomenon manifests itself as a wide band on the visible range on the absorption spectra, and it is confirmed by an important change on the surface colour tones of the samples.