Designing N-Graphene Nanowalls Via Plasma-Enabled Nitrogen Incorporation and Substitution

Surface engineering of graphene-based materials with nitrogen is a potential technique for tailoring the electrical and electronic features of the nanostructures. Surface engineered graphene can be fabricated by adsorbing foreign molecules into the graphene lattice or substitutional doping. Considering different chemical and physical doping techniques, plasma-assisted surface treatment is one of the fastest approaches to design nitrogen-incorporated graphene (N-graphene) with different nitrogen bonding configurations. However, it is still a great challenge to create N-graphene with controlled concentrations and desired configurations of nitrogen. Several studies demonstrated that the structural defects in graphene have a critical role in incorporating N-atoms, which has been well-explained by DFT theories. However, there is a lack of experimental studies to confirm the DFT theories explained for the influence of structural defects for nitrogen incorporation in graphene. In this study, we have demonstrated a systematic study on designing N-graphene with controlled concentration and configuration of nitrogen by plasma post-treatment on vertically oriented graphene nanowalls (GNWs). A low-pressure inductively coupled radio-frequency plasma is used for surface engineering with nitrogen gas as the reactive gas. The structural and morphological analysis describes a remarkable difference in the plasma surface interaction, nitrogen concentration, and nitrogen configurations in GNWs concerning the plasma treatment conditions. As the result of plasma treatment, the creation of structural defects and their healing upon prolonged treatment is determined with several spectroscopic and microscopic techniques. These results, along with the other measurements, revealed that the configurations of the nitrogen groups in graphene are highly influenced by the structural defects formed during the processes. Also, the electrical conductivity of the N-GNWs is strongly influenced by the concentration and different configurations of C-N bonding. These findings demonstrate the potential of plasma to tune the graphene lattice by controlled surface engineering in a fast and facile green approach, which can be fruitful for several future electronics and energy devices.