Piezoelectricity of Janus BiTeX (X = Cl, Br, I) Monolayer: A First-Principles Study.

2-D Janus materials are easy to produce strong piezoelectric properties due to the lack of mirror symmetry. In this article, we have performed the first-principles study on the piezoelectric properties of Janus BiTe ${X}$ (${X} =$ Cl, Br, I) monolayers. The electronic properties are calculated to analyze the causes of piezoelectric properties. Based on the density functional perturbation theory (DFPT), the piezoelectric tensor of Janus BiTe ${X}$ monolayer is calculated, and the piezoelectric coefficient is further calculated. The in-plane piezoelectric coefficient ${d}_{{11}}$ of BiTeI monolayer reaches 7.79 pm/V and the out-of-plane piezoelectric coefficient ${d}_{{31}}$ reaches 0.62 pm/V. Based on nonequilibrium Green’s function, the ${I}$ – ${V}$ response is calculated to analyze the piezoelectric response of the material in the device. In addition, these materials have suitable carrier mobility. Our research work shows that Janus BiTeI monolayer has potential applications in piezoelectric electronic devices, which provides a theoretical basis for further exploration of more 2-D Janus piezoelectric materials. [ABSTRACT FROM AUTHOR]