Aging effect of SiO2 xerogel ®lm on its microstructure and dielectric properties

The properties of porous SiO2 xerogel ®lm strongly depend on the aging process. The morphology of the surface modi®ed SiO2 xerogel ®lm pre-aged for 1 hr at 708C showed a two-dimensional structure. Aging for 12 h at 708C and successive modi®cation of the ®lm induced some particle growth and a three-dimensional network structure. The microstructure of the modi®ed SiO2 xerogel ®lms re¯ects the preformed structure during aging. The surface modi®cation induced the changes of surface coverage from ±OC2H5 and ±OH bonds to ±CH3. However the content of surface chemical species was almost same regardless of aging time. The porosity of the modi®ed sample pre-aged for 12 h at 708C was 89%. The calculated/measured dielectric constants were 1.31/1.42, respectively # 2001 Elsevier Science B.V. All rights reserved.