Development of porous silica thick films by a new base-catalyzed sol-gel route

SiO₂ aerogel particles with a size of 2 nm were successfully dispersed into the SiO₂ gel solution, which was prepared by a modified base-catalyzed sol-gel process. These fine SiO₂ aerogel particles play an important role in releasing internal stress within the porous films and avoiding cracking of the porous thick films. As a result, the porous SiO₂ film with the thickness of 22 μm could be obtained on silicon substrates by spin coating the SiO₂ gel precursor solution with 0.02 wt.% SiO₂ aerogel particles while this film still retained the high porosity of 48% after annealing at 550°C. The effect of the SiO₂ aereogel particles on the roughness of the films was also discussed. This porous SiO₂ film can be applied in large-scale uncooled IR detectors as a thermal-insulating layer.