Microanalysis of single-layer hexagonal boron nitride islands on Ir(111)

Abstract

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.Comment: 9 pages, 6 figure

Annealing of ion-irradiated hexagonal boron nitride on Ir(111)

“…Based on their real space periodicities, the ribbons are identified with the (6 × 2) structure found by Petrović et al as a consequence of h-BN decomposition on Ir(111) [27] after growth at 1370 K. H-BN decomposition on Ir(111) at the same temperature and the presence of a decomposition-related B 1s XPS component was already noticed by Usachov et al [24]. According to the data of Petrović et al [27], the ribbons organize upon cooling at around 1220 K, either through condensation of B adatoms or segregation of B that had been dissolved in the selvage after h-BN decomposition. The boron sheets realized by Feng et al [66] through boron molecular beam epitaxy on Ag(111) display a similar striped appearance as the ribbons observed here, which may be a hint for a similarity in structure.…”

“…Besides exfoliation, chemical vapor deposition on catalytically active metals is a way to prepare well-defined monolayers [13]. Examples are epitaxial h-BN layers on Rh(111) [14][15][16], Ru(0001) [17][18][19], Pt(111) [20], and Ir(111) [21][22][23][24][25][26][27].…”

Stoichiometric edges during the intrinsic growth of hexagonal boron nitride on Ir(111)

“…The exact determination of the real space directions in figure 1 is crucial to settle the issue of armchair versus zigzag edges [15,21,22]. Therefore, we will discuss in detail an elegant method of getting exact, direct and quantitative access to this question by means of a brief excursion.…”

“…In this case quite well defined almost equilateral triangular hBN islands emerge as exhibited by figure 6(a). Some islands are oriented oppositely as a result of the mirrored structure of the internal hBN arrangement [22,30]. Both orientations occur in about equal abundance.…”

“…Recently, Petrović et al [22] have used selected area LEED (μLEED) to obtain information on the orientation of the edges of hBN flakes on Ir(111). The reasoning behind this approach is that the base vectors in reciprocal space are perpendicular to the base vectors in real space.…”