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

    Research output: Contribution to journalArticlepeer-review

    Abstract

    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
    Volume12
    Early online date22 Nov 2017
    DOIs
    Publication statusPublished - 22 Nov 2017

    Keywords

    • graphene
    • silicon photonics
    • Raman

    Research Beacons, Institutes and Platforms

    • National Graphene Institute

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