Epitaxial growth of a 100 square centimetre single crystal hexagonal boron nitride monolayer on copper
The development of two dimensional (2D) materials has opened up possibilities for their application in electronics, optoelectronics and photovoltaics, because they can provide devices with smaller size, higher speed and additional functionalities compared with conventional silicon based devices1. The ability to grow large, high quality single crystals for 2D components that is, conductors, semiconductors and insulators is essential for the industrial application of 2D devices2 4. Atom layered hexagonal boron nitride (hBN) with its excellent stability, flat surface and large bandgap, has been reported to be the best 2D insulator5 12. However, the size of 2D hBN single crystals is typically limited to less than one millimetre13 18, mainly because of difficulties in the growth of such crystals; these include excessive nucleation, which precludes growth from a single nucleus to large single crystals, and the threefold symmetry of the hBN lattice, which leads to antiparallel domains and twin boundaries on most substrates19. Here we report the epitaxial growth of a 100 square centimetre single crystal hBN monolayer on a low symmetry Cu (110) vicinal surface, obtained by annealing an industrial copper foil. Structural characterizations and theoretical calculations indicate that epitaxial growth was achieved by the coupling of Cu <211> step edges with hBN zigzag edges, which breaks the equivalence of antiparallel hBN domains, enabling unidirectional domain alignment better than 99 per cent. The growth kinetics, unidirectional alignment and seamless stitching of the hBN domains are unambiguously demonstrated using centimetre to atomic scale characterization techniques. Our findings are expected to facilitate the wide application of 2D devices and lead to the epitaxial growth of broad non centrosymmetric 2D materials, such as various transition metal dichalcogenides20 23, to produce large single crystals.The epitaxial growth of large single crystal hexagonal boron nitride monolayers on low symmetry copper foils is demonstrated.
Nature