Photoluminescence Enhancement of Silicon Quantum Dot Monolayer by Double Resonance Plasmonic Substrate

A structure composed of a monolayer of luminescent silicon quantum dots (Si-QDs) and a silver (Ag) film over nanosphere (AgFON) plasmonic nanostructure is prepared by precisely controlling the distance. A AgFON structure modifies both the photoluminescence (PL) and the PL excitation (PLE) spectra of a Si-QD monolayer significantly. It is shown that the spectral shape is very sensitive to the spacer thickness and the wavelength dependence of the PL and PLE enhancement factors agrees well with the absorptance spectra. Due to multiple surface plasmon resonances of a AgFON structure, in proper spacer thicknesses, simultaneous enhancements of the excitation cross section and the emission rate are achieved. In the wavelength range where the absorption cross section of Si-QDs is small, the PL enhancement factor averaged in a relatively wide region (10 × 10 mm 2 ) reaches 12.