PHONON MODE STUDY OF SI NANOCRYSTALS USING MICRO-RAMAN SPECTROSCOPY

First-order Raman spectra of hydrogenated nanocrystalline silicon (nc: Si:H) films show unexpected features in their optical vibrational mode s for crystallites with sizes ranging from 2 to 6 nm. Two size-depende nt spectral regions, one with the stronger intensity peaking at 505-50 9 cm(-1) and another a shoulder-like band between 512 and 517 cm(-1), are clearly identified using a detailed line-shape analysis and the st rong phonon confinement model. The strong size dependence of the relat ive integrated intensities of the two bands suggests that the modifica tion of the vibrational spectra can be attributed to an effect induced by the atomic vibrations from the near-surface region of the nanocrys tals. (C) 1995 American Institute of Physics.