The epitaxial growth of single-crystal thin films relies on the availability of a single-crystal substrate and a strong interaction between epilayer and substrate. Previous studies have reported the roles of the substrate (e.g., symmetry and lattice constant) in determining the orientations of chemical vapor deposition (CVD)-grown graphene, and Cu( 111) is considered as the most promising substrate for epitaxial growth of graphene single crystals. However, the roles of gas-phase reactants and graphene−substrate interaction in determining the graphene orientation are still unclear. Here, we find that trace amounts of oxygen is capable of enhancing the interaction between graphene edges and Cu(111) substrate and, therefore, eliminating the misoriented graphene domains in the nucleation stage. A modified anomalous grain growth method is developed to improve the size of the as-obtained Cu(111) single crystal, relying on strongly textured polycrystalline Cu foils. The batch-to-batch production of A3-size (∼0.42 × 0.3 m 2 ) single-crystal graphene films is achieved on Cu(111) foils relying on a self-designed pilot-scale CVD system. The as-grown graphene exhibits ultrahigh carrier mobilities of 68 000 cm 2 V −1 s −1 at room temperature and 210 000 cm 2 V −1 s −1 at 2.2 K. The findings and strategies provided in our work would accelerate the mass production of high-quality misorientation-free graphene films.
Electron-phonon (e-ph) interaction in Ca2N monolayer, the first electrene material with two-dimensional (2D) electron gas floating in free space, is expected to be very weak and such a character can be used to design weak-scattering transport channels. Therefore, it is highly desirable to quantitatively evaluate the carrier mobility of electrene. In this study, e-ph interaction in Ca2N monolayer is investigated using a precise Wannier interpolation-based first-principles technique. The calculated e-ph coupling matrix elements of Ca2N monolayer are indeed small compared to other 2D materials such as graphene, which leads to an intrinsic mobility of 189 cm 2 V −1 s −1 , much higher than those of conventional metals. Other factors affecting mobility are discussed in a comparison with graphene. It is predicted that, based on a momentum mismatch mechanism, mobility of Ca2N monolayer can be increased further to above 3000 cm 2 V −1 s −1 via hole doping. Our results confirm that Ca2N electrene is a promising electronic material.
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