Schematic illustration of the fabrication processes of a GNR/SNW heterojunction LED. (a) The as-synthesized large-scale graphene was transferred to a Si/SiO2 substrate. After that, SNW suspension was dropped on the graphene. (b) A photoresist pad was patterned to cover one end of a SNW by UV lithography and development processes. (c) Oxygen plasma etching was used to remove the exposed graphene. After that, the GNR formed under the SNW. (d) After removing the photoresist, In/Au and Au ohmic contact electrodes to SNW and graphene pad were defined, respectively. It is worth noting that because an undercut was formed during the oxygen plasma etching process (Figure 4c) [6, 27], the In/Au electrode on the SNW will not contact with the GNR beneath.