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Raman mapping analysis of graphene-integrated silicon micro-ring resonators

Raman mapping analysis of graphene-integrated silicon micro-ring resonators
Raman mapping analysis of graphene-integrated silicon micro-ring resonators
We present a Raman mapping study of monolayer graphene G and 2D bands, after integration on silicon strip-waveguide-based micro-ring resonators (MRRs) to characterize the effects of the graphene transfer processes on its structural and optoelectronic properties. Analysis of the Raman G and 2D peak positions and relative intensities reveal that the graphene is electrically intrinsic where it is suspended over the MRR but is moderately hole-doped where it sits on top of the waveguide structure. This is suggestive of Fermi level 'pinning' at the graphene-silicon heterogeneous interface, and we estimate that the Fermi level shifts down by approximately 0.2 eV from its intrinsic value, with a corresponding peak hole concentration of ~3 × 1012 cm−2. We attribute variations in observed G peak asymmetry to a combination of a 'stiffening' of the E 2g optical phonon where the graphene is supported by the underlying MRR waveguide structure, as a result of this increased hole concentration, and a lowering of the degeneracy of the same mode as a result of localized out-of-plane 'wrinkling' (curvature effect), where the graphene is suspended. Examination of graphene integrated with two different MRR devices, one with radii of curvature r = 10 μm and the other with r = 20 μm, indicates that the device geometry has no measureable effect on the level of doping.
1556-276X
Hussein, Siham M.
9ca436a2-f5a2-4c82-a75e-5117f151c4c3
Crowe, Iain F.
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Clark, Nick
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Milošević, Milan
b28da945-84a5-4317-8896-6d9ea6a69589
Vijayaraghavan, Aravind
fa7cec52-c14b-450c-8c86-81f229ed6d55
Gardes, Frederic Y.
7a49fc6d-dade-4099-b016-c60737cb5bb2
Mashanovich, Goran Z.
c806e262-af80-4836-b96f-319425060051
Halsall, Matthew P.
da891598-3a6b-4da7-bb4d-dea2be7abf39
Hussein, Siham M.
9ca436a2-f5a2-4c82-a75e-5117f151c4c3
Crowe, Iain F.
e48916ae-ac94-46da-a552-6af8c7b75f1b
Clark, Nick
799030b7-295b-45b6-bb4c-9622629bb5ab
Milošević, Milan
b28da945-84a5-4317-8896-6d9ea6a69589
Vijayaraghavan, Aravind
fa7cec52-c14b-450c-8c86-81f229ed6d55
Gardes, Frederic Y.
7a49fc6d-dade-4099-b016-c60737cb5bb2
Mashanovich, Goran Z.
c806e262-af80-4836-b96f-319425060051
Halsall, Matthew P.
da891598-3a6b-4da7-bb4d-dea2be7abf39

Hussein, Siham M., Crowe, Iain F., Clark, Nick, Milošević, Milan, Vijayaraghavan, Aravind, Gardes, Frederic Y., Mashanovich, Goran Z. and Halsall, Matthew P. (2017) Raman mapping analysis of graphene-integrated silicon micro-ring resonators. Nanoscale Research Letters, 12 (1). (doi:10.1186/s11671-017-2374-4).

Record type: Article

Abstract

We present a Raman mapping study of monolayer graphene G and 2D bands, after integration on silicon strip-waveguide-based micro-ring resonators (MRRs) to characterize the effects of the graphene transfer processes on its structural and optoelectronic properties. Analysis of the Raman G and 2D peak positions and relative intensities reveal that the graphene is electrically intrinsic where it is suspended over the MRR but is moderately hole-doped where it sits on top of the waveguide structure. This is suggestive of Fermi level 'pinning' at the graphene-silicon heterogeneous interface, and we estimate that the Fermi level shifts down by approximately 0.2 eV from its intrinsic value, with a corresponding peak hole concentration of ~3 × 1012 cm−2. We attribute variations in observed G peak asymmetry to a combination of a 'stiffening' of the E 2g optical phonon where the graphene is supported by the underlying MRR waveguide structure, as a result of this increased hole concentration, and a lowering of the degeneracy of the same mode as a result of localized out-of-plane 'wrinkling' (curvature effect), where the graphene is suspended. Examination of graphene integrated with two different MRR devices, one with radii of curvature r = 10 μm and the other with r = 20 μm, indicates that the device geometry has no measureable effect on the level of doping.

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Accepted/In Press date: 14 November 2017
e-pub ahead of print date: 22 November 2017

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Local EPrints ID: 418291
URI: https://eprints.soton.ac.uk/id/eprint/418291
ISSN: 1556-276X
PURE UUID: 39fc0c79-4085-469e-8a64-68b677aded1d

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Date deposited: 27 Feb 2018 17:30
Last modified: 19 Jul 2019 17:28

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