In situ photoluminescence/Raman study of reversible photo-induced structural transformation of nc-Si

A cubic-to-hexagonal phase transition in Si nanocrystals (NCs) is observed in situ by recording their Raman and photoluminescence (PL) spectra simultaneously. The formation of the hexagonal structure is concluded from the appearance of characteristic Raman peaks and intense PL with spectral positions reported previously for hexagonal Si. The phase transition occurs due to heating of the NCs by the laser beam, but it is supposed to be a photo-induced effect, as it does not occur as a consequence of solely thermal heating. Both the structural transition and concomitant switching of the bright PL emission are reversible and are supposed to be of interest from the viewpoint of application.