Fig. 4: Built in electric field between nanowires and graphene.

a SEM image of a single nanowire/graphene heterojunction. b Surface potential image of a single nanowire/graphene heterojunction. c Potential line distribution at the edge of heterostructure shows the Fermi level difference between the single nanowire and graphene. Schematic illustration of the energy band diagrams for describing a single nanowire (d) under the initial light stimulation, (e) without light stimulation, and (f) under the second light stimulation.