Phys. Rev. Lett. 95, 086801 (2005) [4 pages]Density of States Measured by Scanning-Tunneling Spectroscopy Sheds New Light on the Optical Transitions in PbSe NanocrystalsReceived 15 March 2005; published 17 August 2005 The density-of-states function of individual colloidal PbSe nanocrystals varying in diameter between 3 and 7 nm is measured by resonant tunneling spectroscopy. It is in semiquantitative agreement with tight-binding calculations, but the energy separation between electron (hole) levels of S and P symmetry is systematically smaller than predicted by the theory. These results provide an explanation for the second and third excitonic optical transitions, which have been debated for a long time. © 2005 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevLett.95.086801
DOI:
10.1103/PhysRevLett.95.086801
PACS:
73.22.−f, 73.63.−b, 78.67.−n
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