Electron-phonon coupling and intervalley splitting determine the linewidth of single-electron transport through PbSe nanocrystals
Résumé
The linewidth of the resonances in the single-electron tunneling spectra has been investigated for PbSe semiconductor nanocrystals (NCs) with scanning tunneling spectroscopy at low temperature. The linewidth of the resonances corresponding to tunneling through the first conduction and valence levels is found to increase with decreasing size of the NCs. Based on theoretical calculations, this broadening is mainly induced by the coupling between the tunneling electrons and the longitudinal optical phonon mode of the NC, and by the splitting of the degenerate electronic levels between the different L-valleys in the Brillouin zone. For the smallest sizes, it is shown that the intervalley splitting is the major source of broadening.
The authors wish to acknowledge financial support from NWO/Chemical Sciences (Vidi-Grant No. 700.56.423, P.L.), the European Community (“HERODOT” Project—Grant No. PITN-GA-2008-214954) and Nord Pas de Calais region. We are thankful to Rolf Koole, Arjan Houtepen, and Stephen G. Hickey for the NC samples used in this study.
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