Effect of the surrounding oxide on the photoabsorption spectra of Si nanocrystals

Laura Koponen, Lasse O. Tunturivuori, Martti J. Puska, Risto M. Nieminen

Research output: Contribution to journalArticleScientificpeer-review

23 Citations (Scopus)
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Abstract

A systematic study of the optical absorption of small silicon nanocrystals (Si-NCs) embedded in silicon dioxide is performed using real-time time-dependent density-functional theory. The modeled Si-NCs contain up to 47 Si atoms with the surrounding oxide being described by a shell of SiO2. The oxide-embedded Si-NCs exhibit absorption spectra that differ significantly from the spectra of the hydrogen-passivated Si-NCs. In particular, the minimum absorption energy is found to decrease when the Si-NCs are exposed to dioxide coating. Unexpectedly, the absorption energy of the oxide-embedded Si-NCs remains approximately constant for core sizes down to 17 atoms, whereas the absorption energy of the hydrogen-passivated Si-NCs increases with decreasing crystal size. This trend suggests a different mechanism for producing the lowest-energy excitations in these two cases.
Original languageEnglish
Article number235332
Pages (from-to)1-6
Number of pages6
JournalPhysical Review B
Volume79
Issue number23
DOIs
Publication statusPublished - 26 Jun 2009
MoE publication typeA1 Journal article-refereed

Keywords

  • photoluminiscence
  • Si nanocrystals
  • time-dependent density functional theory

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