Do excited silicon-oxygen double bonds emit light?

Yinan Shu, Benjamin G. Levine

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

Oxidation of the surface of well-passivated silicon nanocrystals introduces defects which dramatically affect the optical properties of the material. One such defect is the silicon-oxygen double bond, which has been implicated as the source of the unusual particle-size-independent S-band photoluminescence of oxidized silicon nanocrystals. Herein, we investigate the photodynamics of this defect by application of a first-principles nonadiabatic molecular dynamics approach to a cluster model containing a silicon-oxygen double bond. Upon excitation, pyramidalization occurs about the double-bonded silicon atom, leading to a conical intersection between the ground and first excited state. This conical intersection facilitates nonradiative decay, resulting in the internal conversion of 7% of the excited population in the first picosecond after excitation. Extrapolation to longer times suggests that nonradiative decay via conical intersection proceeds faster than the microsecond photoluminescence lifetime of silicon nanocrystals and thus that silicon-oxygen double bonds are unlikely to be responsible for the experimentally observed emission.

Original languageEnglish (US)
Pages (from-to)7669-7677
Number of pages9
JournalJournal of Physical Chemistry C
Volume118
Issue number14
DOIs
StatePublished - Apr 10 2014

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