Preparation and characterization of sol-gel processed GeO ₂/methyltrimethoxysilane hybrid thin films

We report on preparation and characterization of GeO₂/ methyltrimethoxysilane hybrid thin films processed by the sol-gel spin coating technique. Acid catalyzed solutions of methyltrimethoxysilane mixed with germanium isopropoxide have been used as precursors for the hybrid materials. The optical properties of the thin films, including refractive index, thickness, and transparency as well as structural characterization, have been studied by using a prism coupling technique, atomic force microscopy, thermal gravimetric analysis, UV-visible spectroscopy, and Fourier transform infrared spectroscopy. The results indicate that a crack-free, low absorption, and high transparency in the visible range optical films with a thickness of about 1.3 μm could be obtained by a single spin-coating process and at low heat treatment temperature. A strong UV absorption region at short wavelength ∼200 nm, accompanied with a shoulder peaked at ∼240 nm, due to the neutral oxygen monovacancies defects, has also been identified.