Visible photoluminescence from a si-rich oxide and the electronic structures of silicon quantum dots

A silicon-rich oxide film was deposited using a plasma generated by an electron cyclotron resonance source with a mixed phase of silane and oxygen gases. The blue-color light emission from the film, observable at room temperature, was investigated for the as-deposited and the rapidly thermally annealed samples. The stable luminescence band at 3.04 eV was observed with the estimated diameter range of 10 - 35 Å. The temperature dependence of the light emission showed that the quantum efficiency of the 3.04-eV band was significantly enhanced by lowering the temperature, indicating the effect of the quantum size on the luminescence mechanism. Both the energy gap and the quantum efficiency were strongly related to the passivating species. The surface-related quantum-size effect was associated with the band broadening effect, indicating a typically broad photoluminescence spectra for quantum dots. The light emissions from the Si-rich oxides were compared with the other experimental results from porous silicon and with the theoretical calculations in the context of the quantum-size effect of the optical energy gap.