Intrinsic piezoelectricity in monolayer MSi₂N₄ (M = Mo, W, Cr, Ti, Zr and Hf)

¹ School of Electronic Engineering, Xi'an University of Posts and Telecommunications - Xi'an 710121, China
² Key Laboratary of Advanced Semiconductor Devices and Materials, Xi'an University of Posts and Telecommunications - Xi'an 710121, China
³ Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Science 110016 Shenyang, Liaoning, China
⁴ School of Materials Science and Engineering, University of Science and Technology of China Shenyang 110016, China

^(a) sandongyuwang@163.com

Received: 22 September 2020
Accepted: 1 December 2020

Abstract

Motived by experimentally synthesized (Hong Y. L. et al., Science, 369 (2020) 670), the intrinsic piezoelectricity in monolayer (, W, Cr, Ti, Zr and Hf) are studied by density functional theory (DFT). Among the six monolayers, has the best piezoelectric strain coefficient d₁₁ of 1.24 pm/V, and the second is 1.15 pm/V for . Taking as a example, strain engineering is applied to improve d₁₁. It is found that tensile biaxial strain can enhance d₁₁ of , and the d₁₁ at 4% strain can improve by 107% with respect to the unstrained one. By replacing the N by P or As in , the d₁₁ can be raised substantially. For and , the d₁₁ is as high as 4.93 pm/V and 6.23 pm/V, which is mainly due to smaller and very small minus or positive ionic contribution to piezoelectric stress coefficient e₁₁ with respect to . The discovery of this piezoelectricity in monolayer enables active sensing, actuating and new electronic components for nanoscale devices, and is recommended for experimental exploration.