Investigation on sol–gel synthesized Ag-doped TiO2 cermet thin films

Undoped TiO 2 and Ag–TiO 2 (up to 23 at.% Ag) cermet thin films and polycrystalline powders have been prepared by sol–gel process. Their structure, composition, surface morphology and optical properties have been investigated by X-ray diffraction (XRD), differential thermal analysis (DTA), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS) and ultraviolet–visible spectroscopy (UV–VIS spectroscopy). It has been observed that while Ag does not form a solid solution with TiO 2 , it promotes the anatase to rutile phase transformation. The transformation temperature decreases from 827 °C for undoped TiO 2 to about 650 °C for 23 at.% Ag-doped TiO 2 . SIMS analyses show that Ag is mostly present on the surface of the films. XPS studies confirm that these Ag are in the Ag 0 state. Optical analyses show that with increasing Ag content, the refractive index ( n ) increases and the optical absorption behavior of the cermet films is modified, but the band gap of the anatase TiO 2 is not influenced.