Raman and transmission electron microscopy study of disordered silicon grown by molecular beam epitaxy

Silicon films were deposited by molecular beam epitaxy onto crystalline silicon (c-Si) and native oxide on c-Si (001) substrates at temperatures ranging from 98 to 572 degreesC. Raman spectroscopy of these films showed that both the short-range disorder and intermediate-range disorder decreases as the deposition temperature increases. The onset of a phase transition in the amorphous Si films can be effectively identified by the appearance of the polycrystalline and crystalline Si Raman bands, which allowed quantification of the crystalline volume fractions present. Both the transmission electron microscopy and Raman results confirmed that films grown on the amorphous substrates at temperatures less than 414degreesC are entirely amorphous, but exhibit c-Si features at higher temperatures. Films grown on c-Si substrates exhibit a characteristic limiting thickness for epitaxy and the transformation of the resulting upper amorphous layer into crystalline form takes place at a much lower temperature (similar to290 degreesC) than for the amorphous substrates. (C) 2004 American Vacuum Society.