Theoretical Study on Origin of CVD Growth Direction Difference in Graphene/hBN Heterostructures

Abstract

The origin of chemical vapor deposition (CVD) growth direction difference in graphene/hexagonal boron nitride (hBN) heterostructures is theoretically studied. The study is focused on the advance in energy gain by H termination of the bare hBN N edge on the Cu(111) surface comparing with that of the bare graphene edge. It is found that the difference in the van der Waals correction method affects largely the advance. However, when the most reliable van der Waals correction of the vdw-DF2-B86R method is used, the results consist with our speculation stating that the edge termination of the existing island rather automatically changes depending on whether the island is graphene or hBN. Thus, it is proposed that the graphene island edge is automatically bare and the hBN island edge is automatically terminated by H during the CVD growth. Keywords Graphene; h-BN; Cu surface; First-principles calculation; Crystal growth directly by the surface Cu atoms. On the other hand, when 65 we put a hBNNR with the H-terminated edges on the sur-66 face, the NR remains flat and floats on the surface. The edge 67 termination, thus, dramatically changes the edge shape on 68 the surface. This also affect on the interaction of the edge 69 with precursors on the surface. When we put a C−C dimer 70 near the bare N edge of hBNNR, the dimer prefers attaching 71 to the edge and directly forming chemical bonds to the edge 72 atoms. However, when we put a C−C dimer near the 73 H-terminated N edge of hBNNR, the dimer prefers pene-74 trating under the NR and avoiding the chemical bond for-75 mation to the edge atoms. We have also performed a similar 76 study on the graphene NR (GNR) edge and/or a B−N dimer, 77 and obtained similar results, while the details are compli-78 cated a little bit in some cases. 79 Our experimental and theoretical results thus naively 80 suggest that, since the graphene island edge is bare, laterally 81 401 4.0). You are free to copy and redistribute articles in any medium 402 or format and also free to remix, transform, and build upon articles 403 for any purpose (including a commercial use) as long as you give 404 appropriate credit to the original source and provide a link to the 405 Creative Commons (CC) license. If you modify the material, you 406 must indicate changes in a proper way.

Epitaxial Intercalation Growth of hBN/Graphene Bilayer Heterostructure on Commercial Copper Foil

“…The edge of the as-grown hBN tends to be covalently bonded to the catalyst surface, presenting a recurved edge. , The hBN/Cu is then cooled to 900 °C and annealed in a hydrogen-rich environment. The hydrogen annealing transforms the hBN edge from a curved state adhering to the Cu surface to a hydrogen-terminated state, thus separating it from the catalyst and providing a channel for carbon source diffusion. ,− Such geometry change of the top layer was previously reported in the growth of bilayer graphene. − Finally, the H-terminated hBN/Cu sample is heated again and C 2 H 2 is introduced to achieve the intercalation growth of graphene between hBN and Cu.…”