  Large hexagonal boron nitride (hBN) single-layer islands of high crystalline
quality were grown on Ir(111) via chemical vapor deposition (CVD) and have been
studied with low-energy electron microscopy (LEEM). Two types of hBN islands
have been observed that structurally differ in their shape and orientation with
respect to iridium, where the former greatly depends on the iridium step
morphology. Photoemission electron microscopy (PEEM) and IV-LEEM spectroscopy
revealed that the two island types also exhibit different work functions and
bindings to iridium, which provides an explanation for differences in their
shape and growth modes. In addition, various temperatures were used for the CVD
synthesis of hBN, and it was found that at temperatures higher than ~950
{\deg}C boron atoms, originating either from decomposed borazine molecules or
disintegrated hBN islands, can form additional compact reconstructed regions.
The presented results are important for advancement in synthesis of
high-quality hBN and other boron-based layered materials, and could therefore
expedite their technological implementation.
