Strain, stabilities and electronic properties of hexagonal BN bilayers*

Hexagonal boron nitride (h-BN) atomic layers have been regarded as fascinating materials both scientifically and technologically due to the sizable band gap. This sizable band-gap nature of the h-BN atomic layers would provide not only new physical properties but also novel nano- and/or opto-electronics applications [1]. Here, we study the first-principles density-functional study that clarifies the biaxial strain effects on the energetics and the electronic properties of h-BN bilayers [2].$^{\mathrm{\thinspace }}$We show that the band gaps of the h-BN bilayers are tunable by applying strains. Furthermore, we show that the biaxial strains can produce a transition from indirect to direct band gaps of the h-BN bilayer. We also discuss that both AA and AB stacking patterns of h-BN bilayer become feasible structures because h-BN bilayers possess two different directions in the stacking patterns. [1] Y. Fujimoto and S. Saito, Phys. Rev. B 93 (2016) 045402. [2] Y. Fujimoto and S. Saito, submitted to Phys. Rev. B.