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 r eleasing internal stress within the porous films and avoiding cracking of t he porous thick films. As a result, the porous SiO2 film with the thickness of 22 mum could be obtained on silicon substrates by spin coating the SiO2 gel precursor solution with 0.02 wt.% SiO2 aerogel particles while this fi lm still retained the high porosity of 48% after annealing at 550 degreesC. The effect of the SiO2 aereogel particles on the roughness of the films wa s also discussed. This porous SiO2 film can be applied in large-scale uncoo led IR detectors as a thermal-insulating layer. (C) 2001 Elsevier Science B .V. All rights reserved.