Plasmon-coupled Cadmium Selenide/Zinc Sulfide quantum dots for photonic applications

Optical properties of hybrid CdSe/ZnS semiconductor quantum dots (SQDs) in the vicinity of gold metal nanoparticles (MNPs) were studied for photonic applications. The photonic applications include flexible full color displays and light emitting diodes. The hybrid optical materials are of great interest for photonic applications because of their large luminescence enhancement, and wide tunability in the optical spectral region. When the SQDs are placed in the vicinity of plasmonic MNPs, excitons and plasmons are coupled through Coulomb interactions. The change of optical properties may include luminescence intensity, polarizability, and temporal decays. The plasmon-exciton coupling determines the luminescence polarization through the Coulomb interaction of dipole oscillations between SQDs and MNPs. This thesis includes the optical properties of luminescence intensity and polarization of CdSe/ZnS in the vicinity of Au nanoparticles with various coupling distances. The coupling distance was controlled by PMMA plasma etching, which acts as a spacer of varying thickness between the mono layers of SQDs and MNPs.;The work presented studies emission enhancement and its physical origin, showing distance dependent measurements between single layers of plasmonic particles and a single layer of SQDs with near resonant coupling. The Purcell enhancement factor is used to explain the internal quantum efficiency of plasmon-coupled SQDs.;The hybrid CdSe/ZnS-Au nanostructures showed greater photoluminescence (PL) intensity than that of QDs without plasmon coupling. A strong PL enhancement of up to nearly three-fold was observed with plasmon-exciton coupling at the mixture of near and far-field interaction domain. The PL from plasmon-coupled SQDs displayed near linear polarization with certain characteristic distances, which proved the dipolar interaction of plasmon-exciton through Coulomb interaction. SQDs are advantageous over organic materials for photonic applications due to their wide tunability, high color purity and relatively low photobleaching properties. In addition, plasmon-coupled SQDs provide high internal quantum efficiency and relatively fast optical transitions. These properties present exciting possibilities in the use of hybrid SQDs for photonic applications.