Structure of vacuum-deposited permethyldecasilane thin films

A linear oligosilane, permethyldecasilane was synthesized and vapor-deposited onto quartz substrates at room-temperature or −150 ° C with various 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 substrates. Deduced spacing of the layer was found to be smaller than the length of the oligosilane molecule along the main chain in all-trans conformation, suggesting that the molecules are not oriented normal to the substrates but with a certain tilt angle. The tilting structure is also supported by the dependence of the polarized absorption spectra on the incident angle.