title: Structure of excited-state transitions of individual semiconductor nanocrystals probed by photoluminescence excitation spectroscopy.
abstract: We perform for the first time photoluminescence excitation (PLE) studies of individual nanocrystals (NCs) that reveal the structure of excited-state transitions not obscured by ensemble averaging. Single-NC PLE spectra strongly deviate from a traditional idealized picture of sharp, quasiatomic resonances. We detect only a few relatively narrow transitions (3-4 meV) at the band edge, while at higher spectral energies, we observe a broad structureless feature separated from the band-edge peaks by a >50 meV "minigap." These observations can be rationalized by analyzing hole intraband relaxation behavior.
authors.affiliation: Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: Han
authors.initials: H
authors.lastname: Htoon
authors.forename: Paris J
authors.initials: PJ
authors.lastname: Cox
authors.forename: Victor I
authors.initials: VI
authors.lastname: Klimov