Magneto-optical properties of II-VI semiconductor colloidal nanostructures

Abstract

Recently, colloidal nanocrystals attract much attention due to their importance in fundamental research on zero-dimensional structures and great potential in a variety of practical applications. The aim of this research is to investigate fundamental properties of a variety of colloidal nanostructures and explore new interesting phenomena in these colloidal nanostructures. By means of magneto-optical experimental techniques, g-factor, spin dynamics and fine structure of the exciton complex in three types of colloidal nanostructures, including core/shell CdSe/CdS nanocrystals, Thoil-capped CdTe NCs and CdSe-based colloidal platelets, were characterized at cryogenic temperatures and in high magnetic fields. A long spin relaxation time was observed in thick-shell CdSe/CdS nanocrystals and mechanisms responsible for different behaviours of exciton spin dynamics observed in thick-shell CdSe/CdS NCs and CdTe NCs were discussed. Additionally, it was found that the Förster resonant energy transfer in ensembles of CdTe colloidal NCs could be enhanced by magnetic field and temperature. Finally, we characterized two types of CdSe-based colloidal platelets which show much smaller bright-dark splitting energy of excitons compared with that in CdSe NCs with similar diameter. This can be explained by the strong decrease of the electron-hole exchange interaction resulting from the reduction of the electron-hole wavefunction overlap in colloidal platelet structures.