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.