Amplified plasmonic emission enhancement of PbS quantum dots via Al-oxide/PMMA heterostructures

We study the impact of Al oxide/Poly(methyl methacrylate) (PMMA) interface on plasmonic emission enhancement of infrared semiconductor quantum dots (QDs). For this, PbS QDs embedded in PMMA matrix are deposited on the top of heterostructures consisting of a Au thin film, a dielectric spacer, and an ultrathin layer of Al oxide. Our results suggest that such structures can support an emission enhancement far more than what can be reached in the cases when the QDs/PMMA films are placed on Au thin film/dielectric spacer directly, i.e. in the absence of the Al oxide. We also demonstrate that Au/Si/Al oxide/PMMA heterostructures can increase the photo-induced fluorescence enhancement of PbS QDs, making them brighter as they are irradiated with a laser field. We discuss these results in terms of combined effects of plasmonic field enhancement (Purcell effect) and the carboxylate anion bonds formed at the Al oxide/PMMA interface.