Optical spectroscopy of colloidal CdSe semiconductor nanostructures

Abstract

Using high-spatial-resolution time-resolved and temperature-dependent spectroscopy, this dissertation investigates emission properties of CdSe nanowires (NWs) synthesized using solid-liquid-solid (colloidal) growth. Temperature-dependent near- field scanning optical microscopy (NSOM) achieved spatial resolution of ~50 nm and imaged single NWs having wurtzite(WZ)-zincblende(ZB) polytype structure. Temperature-dependent NSOM and micro-photoluminescence (Ì_å_PL) spectra produce s- shape peak emission energy dependence on temperature, which reveal the formation of band-tail states in the NWs due to the variation of the polytype structure along the length of the NW. Time-resolved photoluminescence (TRPL) measures emission decay data that shows type-I band alignment between the WZ-ZB heterojunction due to the spectral dependence of the emission decay: the decay times decrease as the energy decreases. Finally, a robust rate equation model was completed for a single NW that produces theoretical calculations for the measurements.