Quantum Confined Electron-Phonon Interaction in Silicon Nanocrystals

D. M. Sagar, Joanna M. Atkin, Peter K.B. Palomaki, Nathan R. Neale, Jeffrey L. Blackburn, Justin C. Johnson, Arthur J. Nozik, Markus B. Raschke, Matthew C. Beard

Research output: Contribution to journalArticlepeer-review

50 Scopus Citations


We study the micro-Raman spectra of colloidal silicon nanocrystals as a function of size, excitation wavelength, and excitation intensity. We find that the longitudinal optical (LO) phonon spectrum is asymmetrically broadened toward the low energy side and exhibits a dip or antiresonance on the high-energy side, both characteristics of a Fano line shape. The broadening depends on both nanocrystal size and Raman excitation wavelength. We propose that the Fano line shape results from interference of the optical phonon response with a continuum of electronic states that become populated by intraband photoexcitation of carriers. The asymmetry exhibits progressive enhancement with decreasing particle size and with increasing excitation energy for a given particle size. We compare our observations with those reported for p- and n-doped bulk Si, where Fano interference has also been observed, but we find opposite wavelength dependence of the asymmetry for the bulk and nanocrystalline Si. Our results have important implications for potentially controlling carrier energy relaxation channels in strongly confined Si nanocrystals.

Original languageAmerican English
Pages (from-to)1511-1516
Number of pages6
JournalNano Letters
Issue number3
StatePublished - 2015

Bibliographical note

Publisher Copyright:
© 2015 American Chemical Society.

NREL Publication Number

  • NREL/JA-5900-62876


  • carrier energy relaxation
  • Electron-phonon coupling
  • Fano-interference
  • Raman spectroscopy
  • silicon nanocrystals


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