Electronic and Optical Properties of Quantum Dots: Metal-Insulator Transitions and Ultrafast Spectroscopy

Abstract

In this thesis I will discuss crossing the metal-insulator transition in ZnO nanocrystal networks as well as the synthesis, electronic states and optical properties of novel infrared emitting CdSe/HgS/CdS QDs. To observe the metal-insulator transition we use a photonic sintering process to selectively increase both the inter-nanocrystal facet radius and the free electron density. This, combined with atomic layer deposition to infill the film, enables us to clear cross the metal-insulator transition. Second, I discuss the synthesis of high quality CdSe/HgS/CdS QDs. The HgS interlayer creates a 'well' for the electrons while holes are delocalized throughout the CdSe/HgS structure. This quasi-type-II system exhibits tunable emission in discrete steps as a function of the HgS interlayer thickness, which we can control with atomic level precision. We investigate the multi-excitonic properties of these dots, and also show their utility for use as near infrared single photon emitters.