Nanoposts of 10-40 nm top diameter on an InGaN/GaN quantum well structure were fabricated using electron-beam lithography and inductively coupled plasma reactive ion etching. Significant blue shifts up to 130 meV in the photoluminescence (PL) spectrum were observed. The blue-shift range increases with decreasing post diameter. For nanoposts with significant strain relaxation, the PL spectral peak position becomes less sensitive to carrier screening. On the basis of the temperature-dependent PL and time-resolved PL measurements and a numerical calculation of the effect of quantum confinement, we conclude that the optical behaviours of the nanoposts are mainly controlled by the combined effect of 3D quantum confinement and strain relaxation.

The photo-response of a ZnO nanoparticle embedded in a nanopore made on a silicon nitride membrane is investigated. The ZnO nanoparticle is manipulated onto the nanopore and sandwiched between aluminum contact electrodes from both the top and bottom. The asymmetric device structure facilitates current-voltage rectification that enables photovoltaic capacity. Under illumination, the device shows open-circuit voltage as well as short-circuit current. The fill factor is found to increase at low temperatures and reaches 48.6% at 100 K. The nanopore structure and the manipulation technique provide a solid platform for exploring the electrical properties of single nanoparticles.

We demonstrate an all-optical modulation of surface plasmon resonance by photo-irradiation induced dielectric constant change of CdSe quantum dots on the gold surface. The dipole-dipole interaction between the surface plasmon and the photo-induced excitons in the dots gives rise to a shift in the surface plasmon resonance peak. This shift is found to sensitively reflect a tiny change in the dielectric constant, which is useful for investigating the nonlinear effect in active plasmonic components.

Voltage controlled photoluminescence (PL) blinking behavior in CdSe nano-particles (NPs) is studied. The NPs are sandwiched between a p-type silicon substrate and a thin Au electrode, which serve respectively as source and drain electrodes. The blinking PL from the NPs can be controlled by the bias voltage across the two electrodes. However, luminescence diminishes when photo excitation power is weak or bias is lower than a threshold voltage. The observed PL blinking is explained by a circuit model, which involves charge tunneling, Fowler-Nordheim (F-N) emission, and charging effect. The blinking intensity is controlled by the number of F-N emitted electrons whereas the pulse interval is associated with the time required for hole accumulation in the NPs. The intensity of luminescence blinking for NP clusters is found to be much higher compared to that of blinking from isolated NPs. This is explained by a collective recombination of F-N emitted electrons and accumulated holes in the NP clusters. This study provides a simple way of controlling PL blinking.