Electronic structure of amorphous silicon nanoclusters

The electronic structure of amorphous silicon nanoclusters is calculated within the empirical tight-binding approximation. The electronic states are classified into three groups: extended and weakly and strongly localized. The last category practically disappears in hydrogenated amorphous silicon clusters for which the blueshift is comparable to what is predicted for crystallites. The radiative recombination rates are comparable for small clusters (similar to 1 nm) but 2 orders of magnitude higher for larger clusters (similar to 2 nm) of the amorphous phase due to disorder induced breaking of selection rules.