Plasmon coupled photoluminescence from silver coated silicon quantum dots

The surface plasmon enhanced photoluminescence (PL) emission of silver coated Si/SiO2 quantum dots (QDs) is investigated theoretically and numerically for different parameters of the QDs. Due to the interaction of radiation with the silver coat, a local surface plasmon oscillation is established which in turn results in a considerable resonant enhancement of the local field in the QDs. The local field enhancement factor inside of the silver coated spherical Si/SiO2 QDs is solved using the Laplace equation. Utilizing this enhancement factor, the plasmon enhanced radiative recombination rate, the spectral absorption, and the PL intensity of ensembles of silver coated Si/SiO2 QDs embedded in a SiO2 host matrix are studied. The induced electric field increases the overlapping of the electron and hole wave functions in the QDs leading to an increase in radiative recombination rate, spectral absorption, and the PL intensity. Moreover, by varying the thickness of silver coat and SiO2 spacer, the surface plasmon resonance frequency can be tuned to the longer wavelength regions in the visible spectrum. This enhances the coupling between surface plasmon resonance frequency of the silver coat and the energy gap of silicon QDs. It is found that the radiative recombination rate, spectral absorption and photoluminescence intensity increase up to 3 folds compared to the QDs without a metal coat.