Quantum confinement, surface roughness, and the conduction band structure of ultrathin silicon membranes

Feng Chen; Edwin B. Ramayya; Chanan Euaruksakul; Franz J. Himpsel; George K. Celler; Bingjun Ding; Irena Knezevic; Max G. Lagally

doi:10.1021/nn100275z

Quantum confinement, surface roughness, and the conduction band structure of ultrathin silicon membranes

Feng Chen, Edwin B. Ramayya, Chanan Euaruksakul, Franz J. Himpsel, George K. Celler, Bingjun Ding, Irena Knezevic, Max G. Lagally

Research output: Contribution to journal › Article

31 Scopus citations

Abstract

We report direct measurements of changes in the conduction-band structure of ultrathin silicon nanomembranes with quantum confinement. Confinement lifts the 6-fold-degeneracy of the bulk-silicon conduction-band minimum (CBM), Δ, and two inequivalent sub-band ladders, Δ₂ and Δ₄, form. We show that even very small surface roughness smears the nominally steplike features in the density of states (DOS) due to these sub-bands. We obtain the energy splitting between Δ₂ and Δ₄ and their shift with respect to the bulk value directly from the 2p_3/2→Δ transition in X-ray absorption. The measured dependence of the sub-band splitting and the shift of their weighted average on degree of confinement is in excellent agreement with theory, for both Si(001) and Si(110).

Original language	English (US)
Pages (from-to)	2466-2474
Number of pages	9
Journal	ACS Nano
Volume	4
Issue number	4
DOIs	https://doi.org/10.1021/nn100275z
Publication status	Published - Apr 27 2010
Externally published	Yes

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All Science Journal Classification (ASJC) codes

Materials Science(all)
Engineering(all)
Physics and Astronomy(all)

Keywords

Quantum confinement
Silicon nanomembrane
Surface roughness
Thermoelectric
Valley splitting

Cite this

Chen, F., Ramayya, E. B., Euaruksakul, C., Himpsel, F. J., Celler, G. K., Ding, B., ... Lagally, M. G. (2010). Quantum confinement, surface roughness, and the conduction band structure of ultrathin silicon membranes. ACS Nano, 4(4), 2466-2474. https://doi.org/10.1021/nn100275z

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abstract = "We report direct measurements of changes in the conduction-band structure of ultrathin silicon nanomembranes with quantum confinement. Confinement lifts the 6-fold-degeneracy of the bulk-silicon conduction-band minimum (CBM), Δ, and two inequivalent sub-band ladders, Δ2 and Δ4, form. We show that even very small surface roughness smears the nominally steplike features in the density of states (DOS) due to these sub-bands. We obtain the energy splitting between Δ2 and Δ4 and their shift with respect to the bulk value directly from the 2p3/2→Δ transition in X-ray absorption. The measured dependence of the sub-band splitting and the shift of their weighted average on degree of confinement is in excellent agreement with theory, for both Si(001) and Si(110).",

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AU - Chen, Feng

AU - Ramayya, Edwin B.

AU - Euaruksakul, Chanan

AU - Himpsel, Franz J.

AU - Celler, George K.

AU - Ding, Bingjun

AU - Knezevic, Irena

AU - Lagally, Max G.

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N2 - We report direct measurements of changes in the conduction-band structure of ultrathin silicon nanomembranes with quantum confinement. Confinement lifts the 6-fold-degeneracy of the bulk-silicon conduction-band minimum (CBM), Δ, and two inequivalent sub-band ladders, Δ2 and Δ4, form. We show that even very small surface roughness smears the nominally steplike features in the density of states (DOS) due to these sub-bands. We obtain the energy splitting between Δ2 and Δ4 and their shift with respect to the bulk value directly from the 2p3/2→Δ transition in X-ray absorption. The measured dependence of the sub-band splitting and the shift of their weighted average on degree of confinement is in excellent agreement with theory, for both Si(001) and Si(110).

AB - We report direct measurements of changes in the conduction-band structure of ultrathin silicon nanomembranes with quantum confinement. Confinement lifts the 6-fold-degeneracy of the bulk-silicon conduction-band minimum (CBM), Δ, and two inequivalent sub-band ladders, Δ2 and Δ4, form. We show that even very small surface roughness smears the nominally steplike features in the density of states (DOS) due to these sub-bands. We obtain the energy splitting between Δ2 and Δ4 and their shift with respect to the bulk value directly from the 2p3/2→Δ transition in X-ray absorption. The measured dependence of the sub-band splitting and the shift of their weighted average on degree of confinement is in excellent agreement with theory, for both Si(001) and Si(110).

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KW - Silicon nanomembrane

KW - Surface roughness

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KW - Valley splitting

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10.1021/nn100275z