Activation of forbidden phonon modes in defect-free graphene on Au(111) substrate by tip-enhanced nano confined light
High photon confinement and the field gradient effect can alter selection rules in Raman spectroscopy. We report the first observation of the forbidden combination Raman modes in defect-free monolayer graphene on an Au(111) substrate whose Raman peak lies at 2918 cm-1. The occurrence of the forbidden combination Raman modes alongside the D and D' modes is due to the nano confined light generated at the tip apex that, in turn, generates a strong field gradient.
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