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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_2,3 edge

Lookup NU author(s): Professor Lidija Siller, Satheesh Krishnamurthy, Dr Ben Horrocks, Dr Yimin Chao, Professor Andrew HoultonORCiD

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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.

Publication metadata

Author(s): Siller L, Krishnamurthy S, Kjeldgaard L, Horrocks BR, Chao Y, Houlton A, Chakraborty AK, Hunt MRC

Publication type: Article

Publication status: Published

Journal: Journal of Physics: Condensed Matter

Year: 2009

Volume: 21

Issue: 9

ISSN (print): 0953-8984

ISSN (electronic): 1361-648X

Publisher: IOP Publishing Ltd.

URL: http://dx.doi.org/10.1088/0953-8984/21/9/095005

DOI: 10.1088/0953-8984/21/9/095005

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