A linear oligosilane, permethyldecasilane was synthesized and vapor-deposit
ed onto quartz substrates at room-temperature or -150 degrees C with variou
s film thickness. X-ray diffraction measurements exhibited a highly ordered
layer structure in the films deposited at room-temperature, while such an
ordered structure could hardly be observed in those deposited onto cooled s
ubstrates. Deduced spacing of the layer was found to be smaller than the le
ngth of the oligosilane molecule along the main chain in all-trans conforma
tion, suggesting that the molecules are not oriented normal to the substrat
es but with a certain tilt angle. The tilting structure is also supported b
y the dependence of the polarized absorption spectra on the incident angle.