Giant Piezoelectric Effects in Monolayer Group-V Binary Compounds with Honeycomb Phases: A First-Principles Prediction

Two-dimensional (2D) piezoelectric materials have gained considerable attention since they could play important roles in the nanoelectromechanical systems. Herein, we report a first-principles study on the piezoelectric properties of monolayer group-V binary compounds with theoretically stable honeycomb phases (α-phase and β-phase). Our calculations for the first time reveal that a majority of the monolayers possess extremely high piezoelectric coefficients d11, i.e., 118.29, 142.44, and 243.45 pm/V for α-SbN, α-SbP, and α-SbAs, respectively, comparable to those of recently reported group-IV monochalcogenides (d11= 75-250 pm/V) with an identical mm2 symmetry. It is found that the giant piezoelectric responses of α-phase monolayers as compared to those of β-phase monolayers are induced by their flexible structures and special symmetry. Meanwhile, the piezoelectric coefficients of α-phase monolayers are found to be surprisingly anisotropic and obey a unique periodic trend which is not exactly identical to that for the β-phase monolayers. To gain a comprehensive understanding of the periodic trends in piezoelectricity, several factors which influence the piezoelectric coefficients are quantitatively determined.