On-demand doping of graphene by stamping with a chemically functionalized rubber lens

A customized graphene doping method was developed involving stamping using a chemically functionalized rubber lens as a novel design strategy for fabricating advanced two-dimensional (2D) materials-based electronic devices. Our stamping strategy enables deterministic control over the doping level and the spatial pattern of the doping on graphene. The dopants introduced onto graphene were locally and continuously controlled by directly stamping dopants using a chemically functionalized hemispherical rubber lens onto the graphene. The rubber lens was functionalized using two different dopants: poly(ethylene imine) to achieve n-type doping and bis(trifluoromethanesulfonyl)amine to achieve p-type doping. The graphene doping was systematically controlled by varying both the contact area (between the rubber lens and the graphene) and the contact time. Graphene doping using a stamp with a chemically functionalized rubber lens was confirmed by both Raman spectroscopy and charge transport measurements. We theoretically modeled the conductance properties of the spatially doped graphene using the effective medium theory and found excellent agreement with the experimental results. Finally, complementary inverters were successfully demonstrated by connecting n-type and p-type graphene transistors fabricated using the stamping doping method. We believe that this versatile doping method for controlling charge transport in graphene will further promote graphene electronic device applications. The doping method introduced in this paper may also be applied to other emergent 2D materials to tightly modulate the electrical properties in advanced electronic devices.