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Core and valence exciton formation in x-ray absorption, x-ray emission and x-ray excited optical luminescence from passivated Si nanocrystals at the Si L-2,L-3 edge

Siller, L.; Krishnamurthy, S.; Kjeldgaard, L.; Horrocks, B.R.; Chao, Y.; Houlton, A.; Chakraborty, A.K.; Hunt, M.R.C.

Authors

L. Siller

S. Krishnamurthy

L. Kjeldgaard

B.R. Horrocks

Y. Chao

A. Houlton

A.K. Chakraborty



Abstract

Resonant inelastic x-ray scattering (RIXS), x-ray absorption spectroscopy and x-ray excited optical luminescence (XEOL) have been used to measure element specific filled and empty electronic states over the Si L-2,L-3 edge of passivated Si nanocrystals of narrow size distribution ( diameter 2.2 +/- 0.4 nm). These techniques have been employed to directly measure absorption and luminescence specific to the local Si nanocrystal core. Profound changes occur in the absorption spectrum of the nanocrystals compared with bulk Si, and new features are observed in the nanocrystal RIXS. Clear signatures of core and valence band exciton formation, promoted by the spatial confinement of electrons and holes within the nanocrystals, are observed, together with band narrowing due to quantum confinement. XEOL at 12 K shows an extremely sharp feature at the threshold of orange luminescence (i.e., at similar to 1.56 eV ( 792 nm)) which we attribute to recombination of valence excitons, providing a lower limit to the nanocrystal band gap.

Journal Article Type Article
Publication Date 2009-03
Deposit Date Oct 7, 2010
Journal Journal of Physics: Condensed Matter
Print ISSN 0953-8984
Electronic ISSN 1361-648X
Publisher IOP Publishing
Peer Reviewed Peer Reviewed
Volume 21
Issue 9
Article Number 095005
DOI https://doi.org/10.1088/0953-8984/21/9/095005
Keywords POROUS SILICON NANOSTRUCTURES; ELECTRONIC-STRUCTURE; BAND-STRUCTURE; QUANTUM CONFINEMENT; FINE-STRUCTURE; SCATTERING; SPECTRA; SPECTROSCOPY; FLUORESCENCE; RELAXATION
Public URL https://durham-repository.worktribe.com/output/1517022