Magnetism and piezoelectricity of hexagonal boron nitride with triangular vacancy

First-principle calculations reveal that the configuration system of hexagonal boron nitride (h-BN) monolayer with triangular vacancy can induce obvious magnetism, contrary to that of the nonmagnetic pristine boron nitride monolayer. Interestingly, the h-BN with boron atom vacancy (V_B-BN) displays metallic behavior with a total magnetic moment being 0.46μ_B per cell, while the h-BN with nitrogen atom vacancy (V_N-BN) presents a half-metallic characteristic with a total magnetic moment being 1.0μ_B per cell. Remarkably, piezoelectric stress coefficient e₁₁ of the V_N-BN is about 1.5 times larger than that of pristine h-BN. Furthermore, piezoelectric strain coefficient d₁₁ (12.42 pm/V) of the V_N-BN is 20 times larger than that of pristine h-BN and also one order of magnitude larger than the value for the h-MoS₂ monolayer, which is mainly due to the spin-down electronic state in the V_N-BN system. Our study demonstrates that the nitrogen atom vacancies can be an efficient route to tailoring the magnetic and piezoelectric properties of h-BN monolayer, which have promising performances for potential applications in nano-electromechanical systems (NEMS) and nanoscale electronics devices.