SELECTIVELY DISORDER ACTIVATED RAMAN-SCATTERING IN SILICON FILMS

Raman spectra have been registered and discussed, for a series of silicon films grown by low pressure chemical vapour deposition (LPCVD). The amorphous-microcrystalline phase transition of the samples has been investigated, as a function of the deposition and annealing parameters. These results have been compared to transmission electron microscopy (TEM) observations on these films. A Raman line near 500 cm-1 has been also evidenced on the low frequency side of the optical vibration mode of silicon, in the as-grown samples and in the phosphorus-doped ones; we assign this line to a selectively disorder-activated mode, due to the numerous stacking faults present in the microcrystalline films.