Tailoring the spontaneous emission from silicon nanocrystals with surface plasmons
Résumé
The use of silicon nanocrystals (SiNC) in optoelectronic devices has risen from a decade thanks to the discovery of photoluminescence in porous silicon in 1991. However SiNCs exhibit a low quantum yield, which prevent from currently using them in optoelectronic devices. This problem can be bypassed thanks to the use of localized surface plasmons (LSP). Indeed LSPs can modify emitters’ photoluminescence by changing the optical local density of states and/or increasing the local excitation field. Numerous studies have been realized with different emitters but the study of LSP coupled with SiNC is scarce. Seminal studies by Biteen and coworkers have paved the way for increasing SiNCs’ performances with LSPs. In these preliminary works only the SiNCs’ emission wavelength was coupled to LSPs. In this work, we present a study where LSPs resonances are coupled simultaneously with the absorption and emission wavelengths of SiNCs. Our original fabrication method gives us the control of all the geometrical parameters that modify the SiNCs-LSPs coupling. The use of nanorods with different shapes and metals allows us to have two plasmon modes. One is located at the SiNC’s absorption wavelength and the other is located at the SiNC’s emission wavelength. The SiNC’s photoluminescence enhancement is thus due to two physical phenomena. To understand these phenomena, we study the influence on SiNC’s photoluminescence intensity, polarization and spatial redirection. We also extract the SiNCs’ radiative quantum yield enhancement in presence of these rods.