Effect of biaxial strain on monolayer and defective SnSe2 systems: A first-principles study

Abstract

In this study, the structural stability, electronic structure, and optical properties of monolayer 2D material SnSe₂ and Se vacancy defect systems under biaxial strain were investigated based on first-principle calculations. The findings showed that the structural stability of a single Se vacancy system is higher than that of a single Sn or two Se vacancy systems. In addition, phonon spectra and AIMD calculations verified the rationality and excellent dynamics stability of the SnSe₂ structure. Electronic structure analysis showed that pristine monolayer SnSe₂ is an indirect bandgap semiconductor with a bandgap of 0.851 eV. The vacancies of Se atoms make the SnSe₂ system close to semi-metallic properties, significantly improving its conductivity. Under the compressive strain of 3%, the band gap type of the defect system is transformed. The optical properties showed that the peak of ε₁(ω) and ε₂(ω) for the pristine monolayer SnSe₂ system produced a redshift under biaxial tensile strain. After the Se atom vacancy, the peak of ε₁(ω) and ε₂(ω) increased significantly. The absorption and reflection peaks of the pristine monolayer SnSe₂ and Se vacancy systems were redshifted under the biaxial compressive strain and blue-shifted under the biaxial tensile strain. The combined action of defects and biaxial strain enhances light absorption in the infrared region and provides a powerful theoretical basis for exploring optoelectronics.