Local hole doping concentration modulation on graphene probed by tip-enhanced Raman spectroscopy

We investigate local doping concentration modulation of graphene flakes on a SiO2/Si substrate that has been exposed to the same chemicals in device fabrication using tip-enhanced Raman spectroscopy (TERS). By spectral line scanning across the edge of graphene, it is observed that the D peak enhancement is localized in the vicinity of the edge boundary, and the TERS spatial resolution of ∼228 nm is obtained. In the TERS spectra significant peak shifts of both the G and 2D peaks are observed more than 7 cm−1 across the hump on graphene within the distance of 1 μm, while both G and 2D peaks are shifted less than 2 cm−1 in the far-field spectra. This indicates that the modulation of hole doping concentration in close proximity on graphene/SiO2/Si can be probed by using TERS surpassing the resolution of a laser diffraction limit of conventional micro Raman spectroscopy.

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