Controlling the orientations of h-BN during growth on transition metals by chemical vapor deposition

Abstract

Hexagonal boron nitride (h-BN) is crucial for many applications, and its synthesis over a large area with high quality is strongly desired. A promising approach to synthesize h-BN is chemical vapor deposition on transition metal catalysts, in which the alignments of BN clusters in the initial growth determine both the types and the amounts of defects in h-BN. In the search for a better catalyst, we systematically studied the interactions between h-BN clusters and various metal surfaces. Our results show that the clusters on nearly all catalyst surfaces, no matter whether the (111) facets of face-centered cubic (FCC) metals or the (0001) facets of hexagonal close packed (HCP) metals, have two local minima with opposite orientations. During the initial growth, h-BN clusters adopt the energy-favored sites, whose registry is well preserved upon further growth owing to the strong interaction between the edge atoms of h-BN and the underlying substrates. On FCC(111), the h-BN domains are always aligned in parallel orientations, while on HCP(0001) they are parallel on the same terrace and anti-parallel on neighboring terraces. Beyond this, on the (111) surfaces of Ir and Rh, the B_hN_t configuration is much more energy favorable than B_fN_t, where, the subscripts h, t, and f represent the adsorption sites, hcp, top and fcc, respectively. Thus, Ir(111) and Rh(111) might promote the growth of h-BN domains with the same alignments, which will greatly improve the quality of h-BN by reducing the possibility of formation of grain boundaries.