STRUCTURAL CHARACTERIZATION OF SOL-GEL-DERIVED SILICA FILMS BY INFRARED SPECTROSCOPY AND GLANCING ANGLE X-RAY DIFFRACTION

Matsumoto Y.⁽¹⁾ and Nishi F. ⁽²⁾

¹Tohoku University, Sendai, JAPAN,
e-mail:nishi@sit.ac.jp
²Saitama Institute of Technology, JAPAN

Keywords: sol-gel, silica films, XRD

Sol-gel techniques are one of the useful method for producing silica films on various substrate types. In this study, triethoxysilane (HSi(OC₂H₅)₃) was used for the raw material and silicon wafers used for the substrate. Hydrolytic and condensation reactions of triethoxysilane were investigated by Fourier transform infrared spectroscopy and by glancing angle X-ray diffraction.

After treated triethoxysilane with several mm thickness on the silicon wafers, C-H, Si-H and Si-O-Si bands were observed by infrared absorption spectra. Comparing the infrared spectrum of triethoxysilane on the silicon wafers at 298K with that of liquid triethoxysilane, the intensity of C-H stretching band decreased and Si-O-Si band newly appeared. This suggests that hydrolysis and condensation reactions proceeded with an atmospheric moisture at 298K and that siloxane(Si-O-Si) frameworks were formed. The intensity, however, of Si-H band did not decrease on heating in air below at 428K, suggesting that the film contained siloxane frameworks with Si-H functional group on the silicon wafers between at 298K and 428K.

On heating it above at 548K, Si-H band shifted from 2234 cm^-1 to 2254 cm^-1 and its intensity drastically decreased. On heating at 808K, Si-H band disappeared and the glancing angle XRD patterns show that the amorphous silica films were newly produced.