Tuning the stability and optoelectronic properties of SnTe/Sb van der Waals heterostructure by biaxial strain effect

Using density functional theory (DFT), we have investigated the structural, stability, and electronic properties of the isolated antimonene, SnTe monolayers, and the structural, stability, and optoelectronic properties of the SnTe/Sb vdW heterostructure. The results show that the atoms in these monolayers have strong cohesion and that the SnTe/Sb vdW heterostructure is stable. The indirect bandgap energies are calculated to be 1.17eV (PBE) (2.28eV (HSE)), 1.89eV (PBE) (2.93eV (HSE)), and 0.32eV (PBE) (0.89eV (HSE)), respectively. However, these physical properties can be modulated by applying biaxial strain, when the compressive and tensile biaxial strain reached more than 4%, the heterostructure turned into metal, and the electronic bandgap decreased as the tensile and compressive biaxial strain increased from 0 to 8%. The phonon dispersion exhibits imaginary modes, notably above the 6% compressive strain, exhibiting its dynamic instability. The formation energy is negative under all biaxial strain, indicating that the heterostructure is still relatively stable during biaxial strain. An enhancement of optical absorption is observed, especially near the UV-visible regions, when the biaxial strain is incorporated, especially for compressive strains of 4% and 2%, which increases the absorption capacity. Therefore, the application of the biaxial strain can improve the stability, optical, and electronic properties of the SnTe/Sb vdW heterostructure, suggesting its potential for photovoltaic and optoelectronic applications.