  Large, high-quality layers of hexagonal boron nitride (hBN) are a
prerequisite for further advancement in scientific investigation and
technological utilization of this exceptional 2D material. Here we address this
demand by investigating chemical vapor deposition synthesis of hBN on an
Ir(111) substrate, and focus on the substrate morphology, more specifically
mono-atomic steps that are always present on all catalytic surfaces of
practical use. From low-energy electron microscopy and atomic force microscopy
data, we are able to set up an extended Wulff construction scheme and provide a
clear elaboration of different interactions governing the equilibrium shapes of
the growing hBN islands that deviate from the idealistic triangular form. Most
importantly, intrinsic hBN edge energy and interaction with the iridium step
edges are examined separately, revealing in such way the importance of
substrate step morphology for the island structure and the overall quality of
2D materials.
