▎ 摘　　要

Patterning graphene with noble metal plasmonic nanostructures to enhance and to manipulate the optical and electronic properties of graphene promises a variety of technological innovations in the field of nano-optoelectronics. In this report, we briefly revisit photoconduction experiments done recently on graphene plasmonic sensors and show that the excess electrical current generated in response to spatially non-uniform optical excitation is primarily induced by a photo-thermo-electric effect in the graphene itself. As this mechanism has nothing to do with the excess free carrier generation common with conventional semiconductors, the plasmonic nanostructures cannot be utilized to regulate the free carrier density and doping of graphene, in contrast to what has been proposed recently. (C) 2014 AIP Publishing LLC.