Evidence for crystalline silicon oxide growth on thin silicon

Thermal oxidation of a silicon-on-insulator (SOI) substrate gives evidence that an ordered silicon oxide structure exists on the upper, thermally oxidised SiO₂-Si interface. The ordered structure of silicon oxide was observed by transmission electron microscopy (TEM) in samples of thin monocrystalline Si film less than 3 nm thick encased by thermal SiO₂. Based on TEM measurement, the ordered silicon oxide has 1.9 A˚ spacing along the [110] direction of the Si structure and 17 A˚ thickness along the (100) direction of the Si structure. Its existence may be related to the fact that the silicon layers were very thin, which may have influenced factors such as their pliancy, since ordered oxide phases were not observed on our samples with silicon layers thicker than 3 nm.