Size and Interface State Dependence of the Luminescence Properties in Si Nanocrystals

For Si nanocrystals, which are formed by Si ion implantation into a SiO2 layer, the effects of crystal size and interface states on the photoluminescence property are investigated. The Si-implanted SiO2 samples are annealed in an N-2 ambience at different temperatures to obtain Si nanocrystals of different sizes. The sample annealed at I 100'C shows a strong and broad photoluminescence (PL) peak at 700mn (1.77eV). The observed PL spectrum, redshifts when the annealing temperature increases, blue shifts when the samples are oxidized, and redshifts followed by blue shifts when the average size of the Si nanocrystals increases and then decreases with etch depth of the SiO2 layer. Low-temperature annealing in an H-2 ambience increases the PL intensity but does not change the PL spectral distribution. Experimental observations indicate that the size of the Si nanocrystal determines the quantum state for carrier excitation and that the, interface states at the Si nanocrystal/SiO2 interface provide the nonradiative recombination centers.