Sol–Gel Strategy for Self-Induced Fluorination and Dehydration of Silica with Extended Vacuum Ultraviolet Transmittance and Radiation Hardness

Fluorinated silica glasses with improved vacuum ultraviolet (VUV) transmittance have been synthesized following a sol-gel route starting from fluorinated alkoxide precursors. Matrix dehydration and fluorination have been investigated by Raman, IR, and refractive index measurements. The results show that, during the densification step, the residual hydroxyl and fluorine content can be controlled by governing the kinetic equilibrium between matrix collapse and fluorine evolution. This highlights the pivotal role of in situ reactions of fluorine-containing molecular precursors in the networking mechanism of a sol-gel material after thermal activation. Superior VUV transmittance and radiation hardness with respect to pure commercial silica and undoped sol-gel silica have been confirmed by synchrotron light absorption measurements before and after X-ray exposure. These properties make the material very attractive for applications in VUV photolithography technologies and optical fibers, especially for use in environments with a high level of ionizing radiation, such as spacecrafts and nuclear power plants.