Near-Field nanoscopy of current-induced excess noise in graphene

We describe a near-field nanoimaging method employed to spatially map the current-induced excess noise occurring in a bilayer graphene constriction with passive scanning near-field microscope (s-SNOM). We find that the excess noise, manifesting itself as fluctuating electromagnetic evanescent fields generated on the sample surface, is discernible only in the constricted region and increases linearly with increasing current. The passive s-SNOM thus proves to be a unique non-invasive experimental tool for investigating the electron transport mechanism via noise mapping in graphene device at the nanometer scale.