Structural analysis of SiO2 gel films by high energy electron diffraction

The structure of SiO 2 gel-films prepared from acid and basic TEOS solutions is analyzed by high energy transmission electron diffraction method. The Si-O bond length of gel-films is 1.58 to 1.60 Å, which is shorter than that of vitreous silica (1.61 Å) but similar to that of 80 Å thick evaporated a-SiO 2 film. An atomic pair peak with 0.81 Å distance exists on the reduced radial distribution functions of the gel-films, which is believed to be O-H, but being smaller than that of H 2 O (0.969 Å).