Evidence of photoluminescence related to subsurface Si–O–Si bonds in sputtered silicon nanoparticles

We have prepared silicon nanoparticles by depositing the dc sputtered Si material on the cooled surface of a liquid-nitrogen-cooled trap. The photoluminescence in the region of 300–550 nm is found to be independent of the surface chemical structure of the particles. FTIR investigations suggest that the photoluminescence peak is related to the Si–O–Si bonds whose stretching vibration wavenumber is about 1080 cm−1. The results show a definite correspondence between the photoluminescence intensities and the 1080 cm−1 FTIR peaks for the different annealed samples. Moreover, this 1080 cm−1 FTIR vibration species arises not from the surface layer but from the deeper subsurface layer of the particles, which explains why the photoluminescence is stable and fairly independent of the oxidation of the surface Si bonds through aging or annealing in the atmosphere.