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 approximate to 950 degrees 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. (C) 2017 Elsevier B.V. All rights reserved.