Surface etching and edge control of hexagonal boron nitride assisted by triangular Sn nanoplates

Hexagonal boron nitride (hBN) is an ideal insulating substrate and template for other two-dimensional (2D) materials. The combination of hBN and 2D materials of group IV atoms, such as graphene, is interesting, because it can offer attractive physical properties and promising applications. Here, we demonstrate the unique behavior of tin (Sn), one of the group IV elements, on multilayer hBN which was grown by chemical vapor deposition (CVD). At high temperatures, triangular nanoplates formed after thermal deposition of Sn on the hBN surface, with their orientations determined by the hBN lattice. The triangular Sn nanoplates moved on the hBN surface, leaving monolayer-deep nanotrenches. Low-energy electron microscopy (LEEM) revealed that the nanotrenches are aligned in the armchair directions of the hBN. Furthermore, an additional Ar annealing without supplying Sn vapor induced the structural change of the linear trenches to triangular pits, indicating the preferential formation of zigzag edges in the absence of Sn. Our work highlights the unique behavior of Sn on hBN and offers a novel route to engineer the hBN surface.