Thermodynamic mechanism of controllable growth of two-dimensional uniformly ordered boron-doped graphene

Two-dimensional (2D) boron-doped graphene (B-G) exhibits remarkable properties for advanced applications in electronics, sensing and catalysis. However, the synthesis of large-area uniformly ordered 2D B-G remains a grand challenge due to the low doping level and uncontrolled distribution of dopants or even the phase separation from the competitive growth of boron polymorphs and graphene. Here, we theoretically explored the mechanism of the epitaxial growth of 2D uniformly ordered B-G on a metal substrate via ab initio calculations. We show that, by establishing the substrate-mediated thermodynamic phase diagrams, the controllable growth of 2D ordered B-G with different B/C stoichiometry can be achieved on appropriate substrates within distinct chemical potential windows of the feedstock by beating the competitive growth of graphene and other impurity phases. It is suggested that a suitable substrate for the controllable epitaxial growth of 2D ordered B-G can be efficiently screened based on the symmetry match and interaction between 2D B-G and the surfaces. Importantly, by carefully considering the chemical potential of boron/carbon as a function of temperature and partial pressure of the feedstock with the aid of the standard thermochemical tables, the optimal experimental parameters for the controllable growth of 2D ordered B-G are also suggested accordingly. This work provides a comprehensive and insightful understanding of the mechanism of controllable growth of 2D B-G, which will guide future experimental design.