Linear oligosilanes (R(SiR2)(10)R), permethyldecasilane (R = CH3), and perpropyldecasilane (R = C3H7), were vacuum-deposited onto quartz substrates under various conditions. Molecular orientation in the deposited thin films was investigated by X-ray diffractometry and absorption spectroscopy with a varying incident angle to the substrate. Two types of highly ordered multilayered structures, one with molecular orientation normal to the substrate and the other with oblique orientation, were observed in the permethyldecasilane thin films deposited at room temperature. When deposited at -150 degreesC, on the other hand, the molecular orientation was largely normal to the substrates but the multilayered structure was hardly formed. For perpropyldecasilane thin films, an interdigitated structure with molecular orientation normal to the substrate was found when deposited at and above room temperatures.