Abstract

SiO₂–GeO₂ films have been synthesized by the sol–gel method starting from an ethanolic solution of Si(OC₂H₅)₄ and Ge(OCH₃)₄. The coatings have been annealed in air at temperatures ranging between 300 °C and 900 °C. The compositional and microstructural evolution of the samples under thermal annealing has been investigated by X-Ray Photoelectron Spectroscopy (XPS), X-Ray Diffraction (XRD), Secondary-Ion Mass Spectrometry (SIMS) and Atomic Force Microscopy (AFM). Pure and molecularly homogeneous films have been obtained after 300 °C thermal treatment. An amorphous network of interconnected SiO₄ and GeO₄ tetrahedra has been observed up to 700 °C. At higher treatment temperatures the formation of crystalline silica in the cristobalite phase has been detected.