• Sarau, G.; Heilmann, M.; Bashouti, M.; Latzel, M.; Tessarek, C.; Christiansen, S.: Efficient Nitrogen Doping of Single-Layer Graphene Accompanied by Negligible Defect Generation for Integration into Hybrid Semiconductor Heterostructures. ACS Applied Materials & Interfaces 9 (2017), p. 10003-10011

10.1021/acsami.7b00067

Abstract:
While doping enables application-specific tailoring of graphene properties, it can also produce high defect densities that degrade the beneficial features. In this work, we report efficient nitrogen doping of ~ 11 at% without virtually inducing new structural defects in the initial, large-area, low defective, and transferred single-layer graphene. To shed light on this remarkable high doping – low disorder relationship, a unique experimental strategy consisting in analyzing the changes in doping, strain, and defect density after each important step during the doping procedure was employed. Complementary micro-Raman mapping, X-ray photoelectron spectroscopy, and optical microscopy revealed that effective cleaning of the graphene surface assists efficient nitrogen incorporation accompanied by mild compressive strain resulting in negligible defect formation in the doped graphene lattice. These original results are achieved by separating the growth of graphene from its doping. Moreover, the high doping level occurred simultaneously with the epitaxial growth of n-GaN micro- and nanorods on top of graphene leading to the flow of higher currents through the graphene/n-GaN rod interface. Our approach can be extended towards integrating graphene into other technologically relevant hybrid semiconductor heterostructures and obtaining an ohmic contact at their interfaces by adjusting the doping level in graphene.