Molecularly interconnected SiO2-GeO2 thin films: sol-gel synthesis and characterization

SiO2-GeO2 films have been synthesized by the sol-gel method starting from a n ethanolic solution of Si(OC2H5)(4) and Ge(OCH3)(4). The coatings have bee n annealed in air at temperatures ranging between 300 degrees C and 900 deg rees C. The compositional and microstructural evolution of the samples unde r thermal annealing has been investigated by X-Ray Photoelectron Spectrosco py (XPS), X-Ray Diffraction (XRD), Secondary-Ion Mass Spectrometry (SIMS) a nd Atomic Force Microscopy (AFM). Pure and molecularly homogeneous films ha ve been obtained after 300 degrees C thermal treatment. An amorphous networ k of interconnected SiO4 and GeO4 tetrahedra has been observed up to 700 de grees C. At higher treatment temperatures the formation of crystalline sili ca in the cristobalite phase has been detected.