| The mechanism of the photoluminescence of silicon nanocrystals has been hotly debated in recent years. Numerous models have been suggested to explain the strong luminescence, and many authors assume a particle size dependence of the emission spectrum (i.e., due to quantum confinement). Here, it will be shown that particle proximity effects can be more important than particle size in the luminescence of silicon nanocrystals. Several sets of specimens were synthesized in which the emission spectra were found to be highly sensitive to the microstructure of the specimens and nearly independent of particle size in size-selective excitation experiments. Using a multilayering approach where silicon nanoparticles were separated by "buffer" layers, the present work obtained strong evidence in favour of particle-to-particle carrier migration in silicon nanocrystal ensembles. The results show that size and, especially, interactions between nanoparticles must be independently controlled in order to isolate the different mechanisms responsible for the luminescence. |
