Temperature-dependent site selection of boron doping in chemically derived graphene

Abstract

Site dependent light element doping in graphene can lead to exciting phenomenological prospects such as tunable bandgap, enhanced electron phonon coupling and anomalous transport properties for superconductivity, ferromagnetism and catalysis. However, they can lead to more additional defect sites and strain dependent effects as a residual fallout of the process and remains open to interpretations. In this work, we delineate a spectroscopic approach combined with ab-initio results to decipher these factors by using a prototypical in-situ boron doped reduced graphene oxide sample specimens and tuning them from low to moderate hole doping concentrations. The selectivity of doping configurations (BC3, BCO2 and BC2O) as well as their concentration is varied by regulating the annealing temperature (up to 1000 °C). We find a competitive relationship between the dopant and the residual surface oxygen atoms with gradual transformation of favorable doping configuration from out of plane to in-plane (substitutional) with increasing temperature. Furthermore, simultaneous induction of point defects and strain related effects in graphene lattice were also observed with increase in doping concentration. This led to anomalous bandgap crossover at high temperatures in boron doped graphene in comparison to the thermally reduced counterpart which could be important for electronic and transport applications.