Giant Piezoelectricity of Janus M₂SeX (M = Ge, Sn; X = S, Te) Monolayers
Jian Qiu, Fusheng Zhang, Hui Li, Xianping Chen, Bao Zhu, Haojie Guo, Zhaogui Ding, Jiading Bao, Jiabing Yu
Abstract
It is found that many two-dimensional materials are easy to obtain out-of-plane piezoelectric properties because of their Janus structure. Here, based on the monolayer GeSe and SnSe, we study the electronic structure and piezoelectricity of the Janus M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> SeX (M=Ge, Sn; X=S, Te) monolayers. Due to the lack of inversion symmetry and mirror symmetry, as well as flexible mechanical properties, the 2D Janus M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> SeX monolayers have large in-plane piezoelectric coefficients d <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> (up to 345.08pm/V) and out-of-plane piezoelectric coefficients d <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">31</sub> (up to 3.83pm/V). All energy band structures of two-dimensional (2D) Janus M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> SeX monolayers show indirect bandgap and Zeeman-type spin splitting after considering spin orbit coupling (SOC). The lack of mirror symmetry leads to out-of-plane spin polarization. In addition, the calculation based on the deformation potential theory shows that the 2D Janus M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> SeX monolayers have high carrier mobility. The large piezoelectric properties and high carrier mobility show the application potential of 2D Janus M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> SeX monolayers in flexible electronic devices and piezoelectric devices.