Low damage pre-doping on CVD graphene/Cu using a chlorine inductively coupled plasma

Abstract

This study reports a novel approach for chlorine doping of graphene using low-energy plasma in a low damage inductively coupled plasma (ICP) system, which results in significant reduction (∼60%) of the sheet resistance while maintaining high optical transparency. The chemical vapor deposited graphene on Cu (graphene/Cu foil) was directly doped with low-damage chlorine plasma before transferring to the substrate, i.e. pre-doped, in addition to the normal doping conducted after the transfer. Some of the pre-doped chlorine remained on the graphene surface even after the wet transfer to the substrate due to strong C–Cl bonds formed at the graphene defect site. This technique allowed us to achieve the highest chlorine doping ever reported, 47.2%, through combination of pre-doping with conventional doping. By this additional pre-doping on graphene/copper foil (that is, 90 s pre-doping + 90 s normal doping), a monolayer of graphene with very low sheet resistance of 240 Ω/sq could be obtained without sacrificing the optical transmittance (>97.7% at 550 nm wavelength).