Structural and electronic properties of c-BN (111) surface with hydrogen/fluorine functionalization and...

Using first-principles density functional theory calculations, we systematically investigate the structural and electrical properties of pure, hydrogen (H) and fluorine (F) functionalized polar (111) cubic boron nitride (c-BN) surface. In the absence of surface functionalization, the reconstructed B-terminated surface is energetically preferable. The hydrogenation is favorable for stabilizing N- and B-terminated surfaces, while the fluorination leads to the stable unreconstructed B-terminated structure due to strong site preference of F atoms. The reconstructed c-BN surface has magnetic characteristic, and the spin density distributions are mainly localized around the interlayer weak B-B bonds. The unreconstructed structures are nonmagnetic. Meantime, the adsorption behavior of nitric oxide (NO) and ammonia (NH₃) molecules are investigated on the reconstructed c-BN surface. It is found that the adsorption of NO has a considerable effect on the energy levels near the Fermi level, while the energy levels of NH₃ are located at the deep energy level below the Fermi level. Our theoretical results are helpful for understanding experimental phenomenon in practical applications and designing novel c-BN based molecule sensors.