New two-dimensional boron nitride allotropes with attractive electronic and optical properties

Using first principles calculations, structural, electronic and optical properties of five new 2D boron nitride (BN) allotropes have been studied. The results exhibit that the cohesive energy for all these five new allotrope is positive such as all these systems are stable; therefore, it is possible to synthesize these structures in experiments. It is found that the band gap of all new 2D BN allotropes is smaller than the h-BN sheet. In our calculations the dielectric tensor is derived within the random phase approximation (RPA). Specifically, the dielectric function, refraction index and the loss function, of the 2D BN allotropes are calculated for both parallel and perpendicular electric field polarizations. The results show that the optical spectra are anisotropic along these two polarizations. The results obtained from our calculations are beneficial to practical applications of these 2D BN allotropes in optoelectronics and electronics.