Sol-gel derived hard optical coatings via organic/inorganic composites

Hard optical coatings via TiO2/organically modified silane composites have been prepared by the sol-gel technique using (gamma)-Glycidoxypropyltrimethoxysilane (GLYMO, used as organically modified silane source) and tetrapropylorthotitanate (TPOT, used as TiO2 source) as precursors. Scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy have been used to investigate the morphology and structural properties of the coatings. The hardness and Youngʹs modulus of the coatings have been characterized by a Nanoindenter and found to depend on the heat-treatment temperature and titanium content. Hardness as high as 10 Gpa was achieved at a heat-treatment temperature of 1000 °C. It was proposed that the high hardness of the coating is related to the carbon and titanium content in the coating.