single-crystal hexagonal boron nitride monolayer on the symmetry broken substrate

The ability to grow high-quality large single crystals of essential 2D materials, is at the heart for the industrial applications of 2D devices. Atom-layered hexagonal boron nitride (hBN), with its excellent stability, flat surface and large bandgap, has been reported to be the best 2D insulator. However, the size of single-crystal 2D hBN is still typically less than the wafer scale, mainly due to the extreme difficulties in its single-crystal growth: the three-fold symmetry of hBN lattice leading to antiparallel domains resulting in twin boundaries on most substrates. Here, we report the first epitaxial growth of a 10 × 10 cm² single-crystal hBN monolayer on a low symmetry Cu(110) “vicinal surface” obtained by annealing an industrial Cu foil. Our experimental and theoretical work indicate that epitaxial growth is made by Cu<211> step-zigzag hBN edge coupling that serves to break the equivalence of antiparallel hBN domains, enabling unidirectional domains alignment of > 99%. The findings in this work can significantly boost the applications of 2D devices, and also pave the way for the epitaxial growth of broad non-centrosymmetric 2D materials, such as various transition metal dichalcogenides, into large-sized single crystals.

Reference:
Li Wang et al., Nature, 2019, 570, 9