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

Siliconfilms 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\u200a\ub0C. 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 filmsgrown on the amorphous substrates at temperatures less than 414\u200a\ub0C are entirely amorphous, but exhibit c-Si features at higher temperatures. Filmsgrown 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 (\u223c290\u200a\ub0C) than for the amorphous substrates.Peer reviewed: NoNRC publication: Ye