Strain tunable ferroelectricity of SnSe/SnTe van der Waals heterostructures

Two-dimensional (2D) van der Waals heterostructures (vdWHs) have attracted significant attention due to their potential applications in nanoscale electronic devices. Based on the firstprinciples calculations, we design the SnSe/SnTe and SnSe/SnTe/SnSe vdWHs with dynamical stability and thermal stability and investigate their mechanical and electronic properties. We find that the SnSe/SnTe and SnSe/SnTe/SnSe vdWHs have better flexibility than other 2D vdWHs. The SnSe/SnTe and SnSe/SnTe/SnSe vdWHs show reduced direct bandgap and indirect bandgap, respectively. They can also realize the transition between direct and indirect bandgap, and even exhibit the metallic property under external strains. Furthermore, the SnSe/SnTe and SnSe/SnTe/ SnSe vdWHs exhibit stable ferroelectric spontaneous polarizations with small potential barriers. The ferroelectric spontaneous polarization of SnSe/SnTe vdWH increases rapidly as the biaxial tensile strain (<1%) increases, and then decreases slightly. Under the action of 1% biaxial tensile strain, the SnSe/SnTe vdWH has the largest ferroelectric spontaneous polarization 1.721 x 10(-10) C/m and a smaller potential barrier 7.593 meV. Our work confirms that IVA-monochalcogenides vdWHs have tunable ferroelectric spontaneous polarization, which can provide new clues for the study and application of novel 2D ferroelectric heterostructures.