Blue–violet photoluminescence from colloidal suspension of nanocrystalline silicon in silicon oxide matrix

We report room temperature visible photoluminescence (PL), detectable by the unaided eye, from colloidal suspension of silicon nanocrystals (nc-Si) prepared by mechanical milling followed by chemical oxidation. The PL bands for samples prepared from Si wafer and Si powder peak at 3.11 and 2.93 eV respectively, under UV excitation, and exhibit a very fast (∼ns) PL decay. Invasive oxidation during chemical treatment reduces the size of the nc-Si domains distributed within the amorphous SiO2 matrix. It is proposed that defects at the interface between nc-Si and amorphous SiO2 act as the potential emission centers. The origin of blue–violet PL is discussed in relation to the oxide related surface states, non-stoichiometric suboxides, surface species and other defect related states.