Photoluminescence of silicon nanoclusters with reduced size dispersion produced by laser ablation

We report a photoluminescence study of silicon nanoclusters produced by las er ablation. It was found that by varying the preparation parameters it was possible to change the mean cluster size in the range 1-5 nm. Within this size variation, the photoluminescence band shifts in a wide spectral region from near ultraviolet to near infrared. This size-dependent photoluminesce nce of Si nanoclusters is consistent with a quantum confinement effect. The observed influence of cluster oxidation on the luminescence properties als o supports the quantum confinement interpretation. We proposed a discrete s ize model which supposes that the spectral position of the luminescence ban d is essentially determined by the volume of clusters with a complete outer atomic layer. In the framework of this model, we were able to deconvolute the observed luminescence bands into a set of fixed Gaussian bands. The mod el is supported by the observation of a size selective doping of Si nanoclu sters whose effect was well explained by Auger recombination. Finally, our model allowed us to obtain a dependence of the optical gap on the cluster s ize which is in good agreement with existing calculations of Si nanocrystal electronic structure. (C) 2000 American Institute of Physics. [S0021-8979( 00)06708-6].