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

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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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Date
2009-06-26
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Mcode
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Language
en
Pages
6
1-6
Series
Physical Review B, Volume 79, issue 23
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.
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Keywords
photoluminiscence, Si nanocrystals, time-dependent density functional theory
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Citation
Koponen , L , Tunturivuori , L O , Puska , M J & Nieminen , R M 2009 , ' Effect of the surrounding oxide on the photoabsorption spectra of Si nanocrystals ' , Physical Review B , vol. 79 , no. 23 , 235332 , pp. 1-6 . https://doi.org/10.1103/PhysRevB.79.235332