Preparation of amorphous and crystalline Ag/TiO2 nanocomposite thin films

Highlights: ► Amorphous and crystalline Ag/TiO2 thin films were prepared by sol–gel process tailored by cooling rate. ► Silver diffusion mechanism into the titania matrix was evaluated. ► Amorphous to anatase–rutile crystalline phase transitions was performed during electron exposition in a TEM. ► Silver concentration plays a role in Ag/TiO2 thin films plasmon resonance, making them good candidates for optical applications. - Abstract: Ag/TiO2 thin films have been prepared on glass substrates by the dip-coating technique and sol–gel process using a precursor solution containing titanium alkoxide and silver nitrate in an Ag/Ti atomic ratio of 1:6 and 1:100. These films were annealed at 100 °C and 400 °C and cooled rapidly to obtain silver nanoparticles dispersed in an amorphous TiO2 matrix, confirmed by X-ray diffraction (XRD) analyses. Ag/TiO2 nanocrystalline films were also prepared using slow cooling. Silver nanoparticles coalesced and migrated to the thin film surfaces with increasing annealing temperature as observed by high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) and scanning probe microscopy (SPM). A transmission electron microscope (TEM) was used to induce phase transition in the amorphous matrix into anatase and rutile crystalline phases using a 200 kV electron beam. The variation of the Ag/Ti atomic ratio changed the plasmon resonance absorption and band gap values of the Ag/TiO2 films due to the change in the Ag nanoparticle sizes formed on the surface of films, as verified by UV–vis absorption spectroscopy and spectroscopic ellipsometry.