The interface microstructure and band alignment of hexagonal boron nitride/diamond heterojunctions

Integrating a two-dimensional (2D) hexagonal boron nitride (h-BN) layer on diamond for establishing a h-BN/diamond heterojunction is of considerable interest for the development of various diamond-based electronic devices. Herein, 2D h-BN layers were directly grown on polycrystalline diamond substrates by using the ion beam sputtering deposition technique. Benefiting from the in situ Ar ion treatment, the h-BN/diamond heterojunction exhibits a smooth surface and a sharp interface. It is found that the growth orientation of the h-BN layer is dependent on the exposed facets of the diamond substrate. The horizontally aligned h-BN layers were achieved on the diamond (111) and (220) planes, whereas the vertically aligned h-BN layers were grown on the diamond (311) and (400) planes. The different orientations of h-BN layers can be well understood as a result of the minimization of the system energy and suitable lattice matching. Furthermore, the valence and conduction band offsets of the h-BN/diamond heterojunction were determined to be 2.08 and 1.86 eV by using Kraut's method, respectively, which provides essential information for designing high-performance electronic devices based on the h-BN/diamond heterojunction.