Highly adjustable piezoelectric properties in two-dimensional LiAlTe2by strain and stacking.

Two-dimensional (2D) piezoelectric materials have attracted wide attention because they are of great significance to the composition of piezoelectric nanogenerators. In this work, we have systematically studied the piezoelectric properties of 2D LiAlTe2by using the first-principles calculation and found the 2D LiAlTe2monolayer exhibits both large in-plane piezoelectric coefficientd11(3.73 pm V-1) and out-of-plane piezoelectric coefficientd31(0.97 pm V-1). Moreover, the piezoelectric coefficients of 2D LiAlTe2are highly tunable by strain and stacking. When different uniaxial strains are applied,d11changes dramatically, butd31changes little. When 2% stretching is applied to 2D LiAlTe2monolayer along thex-axis,d11reaches 7.80 pm V-1, which is twice as large as the previously reported 2D piezoelectric material MoS2. Both AA stacking and AB stacking can enhance the piezoelectric properties of 2D LiAlTe2, but they have different effects on in-plane and out-of-plane piezoelectric coefficients. AA stacking can greatly increased31but has little impact ond11. In the case of four-layer AA stacking, thed31reaches 3.32 pm V-1. AB stacking can both increased11andd31, butd11grows faster thand31as the number of layers increases. In the case of four-layer AB stacking,d11reaches 18.05 pm V-1. The excellent and highly tunable piezoelectric performance provides 2D LiAlTe2greater potential for the application of piezoelectric nano-generators and other micro-nano piezoelectric devices.