Raman mapping analysis of graphene integrated silicon micro-ring resonators

Siham Mohamed Ahmed Hussein, Iain Crowe, Nicholas Clark, Milan Milosevic, Aravind Vijayaraghavan, Frederic Y. Gardes, Goran Z. Mashanovich, Matthew Halsall

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    We present a Raman mapping study of monolayer graphene G and 2D bands, after integration on silicon strip-waveguide based micro-ring resonators (MRR’s) to characterize the effects of the graphene transfer processes on its structural and opto-electronic 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 0.2eV from its intrinsic value, with a corresponding peak hole concentration of ~31012cm-2. We attribute variations in observed G-peak asymmetry to a combination of a ‘stiffening’ of the E2g 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 = 10μm and the other with r = 20μm indicates that the device geometry has no measureable effect on the level of doping.
    Original languageEnglish
    Article number200
    JournalNanoscale Research Letters
    Early online date22 Nov 2017
    Publication statusPublished - 22 Nov 2017


    • graphene
    • silicon photonics
    • Raman

    Research Beacons, Institutes and Platforms

    • National Graphene Institute


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