Effects of titanium content on properties of sol-gel silica-titania films via organically modified silane precursors

The effects of titanium content on the properties of silica-titania films b y the sol-gel method using gamma -glycidoxypropyltrimethoxysilane (GLYMO), tetraethoxysilane (TEOS) and tetrapropylorthotitanate (TPOT) as the startin g materials have been investigated. Atomic force microscopy (AFM), ellipsom etry, thermal gravimetric analysis (TGA), UV-visible spectroscopy (UV-VIS), Fourier transform infrared (FT-IR) spectroscopy, x-ray photoelectron spect roscopy (XPS) and Raman spectroscopy have been used to investigate the opti cal and structural properties of the films. These results showed that crack -free and high transparency tin the visible and near infrared range) silica -titania films with a thickness of 0.75 mum could be obtained by a single s pin-coating process after a heat treatment at 500 degreesC. The hardness an d Young's modulus of the films were also characterized by a nanoindenter an d showed a linear dependence on the titanium content. Hardness as high as 9 .0 GPa was achieved in a high titanium content film at a heat treatment tem perature of 800 degreesC.