Atomic geometry and energetics of native defects in cubic boron nitride

Abstract

We use first-principles calculations to investigate the electronic structure, atomic geometries and formation energies of point vacancies (VB, VN), antisites (BN, NB) and interstitials (Bi, Ni) in cubic boron nitride (c-BN). We find that nitrogen and boron vacancies exhibit the lowest formation energies in nonstoichiometric c-BN for p-type and n-type conditions, respectively, showing intrinsic donor (VB) and acceptor (VN) characters. The equilibrium geometries show large outward breathing relaxations for both vacancies and for BN, with slight Jahn-Teller distortions from Td symmetry. For NB we find an off-center distortion inducing a negative-U behavior in this center. For both interstitial centers we find stable configurations in which an atomic pair occupies a nitrogen site in the lattice, N-N for Ni and N-B for Bi. These systems are stable for the different charge states investigated.