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 (alpha-phase and beta-phase). Our calculations for the first time reveal that a majority of the monolayers possess extremely high piezoelectric coefficients d(11), i.e., 118.29, 142.44, and 243.45 pm/V for alpha-SbN, alpha-SbP, and alpha-SbAs, respectively, comparable to those of recently reported group-IV monochalcogenides (d(11) = 75-250 pm/V) with an identical mm2 symmetry. It is found that the giant piezoelectric responses of alpha-phase monolayers as compared to those of beta-phase monolayers are induced by their flexible structures and special symmetry. Meanwhile, the piezoelectric coefficients of alpha-phase monolayers are found to be surprisingly anisotropic and obey a unique periodic trend which is not exactly identical to that for the beta-phase monolayers. To gain a comprehensive understanding of the periodic trends in piezoelectricity, several factors which influence the piezoelectric coefficients are quantitatively determined.