Graphene–boron nitride superlattices: the role of point defects at the BN layer

We investigate, by means of first-principles calculations, the role of hBN point defects on the energetical stability and electronic structure of heterostructures composed of graphene atop hBN, rotated at angles of 13.17°, 9.43° and 7.34°. We consider, as possible point defects, boron and nitrogen vacancies and antisites, substitutional oxygen at the nitrogen site O_N, substitutional carbon dimers, and nitrogen interstitials. The electronic and structural properties of all defects were analyzed. Among these, the most stable is O_N, with negative formation energies at several possible rotation angles and chemical environments. Under such conditions, O_N doping can raise the Fermi level of the neutral system by as much as 1 eV relative to graphene’s Dirac point, reaching the band crossing between adjacent Dirac cones at the M point of the heterostructure Brillouin zone. This could lead to interesting electronic transport properties without the need for electrostatic doping. (paper)