Doping and quantum confinement effects in single Si nanocrystals observed by scanning tunneling spectroscopy

O. Wolf, M. Dasog, Z. Yang, I. Balberg, J. G.C. Veinot*, O. Millo

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

92 Scopus citations

Abstract

We have applied scanning tunneling spectroscopy in studies of the electronic level structure of surface-functionalized colloidal Si nanocrystals (Si-NCs) as a function of their size for various capping ligands. The energy gaps extracted from the tunneling spectra increase with decreasing NC size, manifesting the effect of quantum confinement. This is consistent with the blueshift revealed by photoluminescence (PL) from dodecene functionalized Si-NCs. The tunneling spectra measured on NCs functionalized with NH 4Br or allylamine show band-edge shifts toward higher energies, akin to p-type doping. This behavior can be accounted for by the combined contributions of the ligands' dipole moments and charge transfer between a Si-NC and its surface groups. Concomitantly, size-independent PL spectra, which cannot be associated with NC band gap variations, were observed for the latter Si-NCs.

Original languageAmerican English
Pages (from-to)2516-2521
Number of pages6
JournalNano Letters
Volume13
Issue number6
DOIs
StatePublished - 12 Jun 2013

Keywords

  • Silicon nanocrystals
  • photoluminescence
  • quantum confinement
  • scanning-tunneling-spectroscopy
  • surface-doping

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