Study of TiO2, SnO2 and nanocomposites TiO2:SnO2 thin films prepared by sol-gel method: Successful elaboration of variable-refractive index systems

In this research TiO2, SnO2 and TiO2:SnO2 nanocomposite thin films were fabricated by the sol-gel dip coating technique. The mixture was prepared by varying the molar ratio of SnO2 to TiO2, i.e. TiO2:SnO2 (9:1), TiO2:SnO2 (8:2) and TiO2:SnO2 (6:4)). The obtained samples were characterized by means of the Raman microscopy, Scanning Electron Microscopy (SEM), UV-Vis spectrophotometry and m-lines spectroscopy (Prism coupler). Raman analysis shows that pure TiO2 and SnO2 thin films are characterized by the vibrational modes of anatase and rutile cassiterite, respectively. Furthermore, the Raman spectra of the TiO2:SnO2 nanocomposites show the presence of a mixture of anatase and rutile TiO2 phases. The SEM images reveal that the morphology is clearly modified with SnO2 content. The ripples in the transmittance spectra decreased with increasing SnO2 content. Also, the evolution of the optical band gap seems to be consistent with the Raman analysis. A great attention has been paid to the refractive index measurements by the prism coupler technique. In this way, variable-refractive index systems have been successfully obtained using TiO2:SnO2 nanocomposite thin films.