Structural, Electronic, and Magnetic Properties of the Semifluorinated Boron Nitride Bilayer: A First-Principles Study

Using density functional theory calculations with dispersion correction, we present a comprehensive study on the semifluorinated boron nitride (BN) bilayers. We find that the semifluorination leads to a nonbonded configuration in BN bilayers spontaneously, which would transform to the diamondized configuration via moderate pressure. Due to the combined effect of intrinsic intralayer strain and interlayer charge transfer, the ferromagnetic coupling is favored in both configurations, which exhibit intriguing half-metallic behavior for BN bilayers. While these nonbonded and diamondized configurations could undergo a 2 x 1 reconstruction, this requires overcoming a fair energy barrier owing to the sliding and warping of BN planes. With such reconstruction, the stability is greatly enhanced, and the system is converted into a nonmagnetic direct-band-gap semiconductor. Our studies demonstrate that the semifluorination can bring diverse electronic and magnetic properties into the BN bilayer, which could be half-metals or semiconductors depending on the structural types and would have potential applications in spintronics and nanodevices.