A theoretical study of various effects on the wavelength of photoluminescence in Si nanostructures

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Abstract
The photoluminescence in Si nanostructures is studied theoretically through the effects of size, shape and condition of the cluster surface on the energy gap of the Si cluster. Si clusters with a spherical shape or columnar shape are considered. The effect of the condition of the cluster surface is investigated through the chemisorption of hydrogen atoms at the surface. It is found that the energy gap of a cluster decreases with increase in cluster size. For the cluster to simulate an Si column, the calculated energy gap can fall into the energy region of visible-light luminescence with decrease in the cluster size. In the size range (less than 20 AA) considered, the energy gap of the cluster is strongly dependent on the shape, and the surface condition might be important for the determination of the electronic structures of Si nanostructures. These results might be useful in the understanding of photoluminescence in porous Si. The electronic structures of clusters are also investigated in detail.