Fig. 1: Triangle and hexagonal shapes of hexagonal boron nitride (hBN) islands on Cu(111) substrates.
From: Single-crystal hBN Monolayers from Aligned Hexagonal Islands

a–c Atomic illustrations of the triangle-shaped hBN island with all N-terminated edges (a), and the hexagonal-shaped hBN island with the same number of N- and B-terminated edges (c).