BN analogues of graphene: On the formation mechanism of boronitrene layers - solids with extreme structural anisotropy

Boron nitride is an extremely useful material for applications in material sciences and appears in a manifold of crystalline modifications, with hexagonal and cubic boron nitride as most prominent substances. In hexagonal boron nitride, threefold coordinated boron and nitrogen atoms form two-dimensional layers, which resemble the boron nitride analogue of graphene layers, and we refer to this two-dimensional network as boronitrene layers. So far, there is little knowledge about the elementary growth reactions of these boronitrene layers. Here we show that it is possible to regenerate a previously prepared 14 x 14 BN/13 x 13 Rh(111) superstructure [obtained by CVD of borazine (B3N3H6)] after an oxidation step from an unordered monolayer of a boron-oxygen compound by chemical reactions induced by ammonia as nitrification agent on the surface. The individual steps of the experiment were controlled by a LEED- and XPS- analysis and indicate that the original BN superstructure can be recovered without traceable amounts of oxygen in the film. The presented results indicate that highly mobile species from the B-N-O-H system can be considered as surfactants in the elementary formation and degradation reactions of highly ordered boronitrene layers. An understanding of these reactions is a fundamental issue in tuning the crystal growth and quality of the BN phases. (C) 2010 Elsevier B.V. All rights reserved.