Controllable N-Doping of Graphene

Abstract

Opening and tuning an energy gap in graphene are central to many electronic applications of graphene. Here we report N-doped graphene obtained by NH₃ annealing after N⁺-ion irradiation of graphene samples. First, the evolution of the graphene microstructure was investigated following N⁺-ion irradiation at different fluences using Raman spectroscopy, showing that defects were introduced in plane after irradiation and then restored after annealing in N₂ or in NH₃. Auger electron spectroscopy (AES) of the graphene annealed in NH₃ after irradiation showed N signal, however, no N signal was observed after annealing in N₂. Last, the field-effect transistor (FET) was fabricated using N-doped graphene and monitored by the source−drain conductance and back-gate voltage (G_sd−V_g) curves in the measurement. The transport property changed compared to that of the FET made by intrinsic graphene, that is, the Dirac point position moved from positive V_g to negative V_g, indicating the transition of graphene from p-type to n-type after annealing in NH₃. Our approach, which provides a physical mechanism for the introduction of defect and subsequent hetero dopant atoms into the graphene material in a controllable fashion, will be promising for producing graphene-based devices for multiple applications.