Effect of applied biaxial strain in O-doped system on the optoelectronic properties of monolayer GeS

In this study, we apply first-principle calculations to systematically investigate the synergistic regulation of physical properties of monolayer GeS materials by oxygen doping and biaxial strain. Theoretical calculations show that oxygen doping improves the charge uniformity of the system, and the strain enhancement reduces the degree of orbital hybridization and enhances the electron delocalization; doping broadens the bandgap of the material, which reaches a maximum at 2 % tensile strain, shrinks with increasing strain, and decreases monotonically under compressive strain. Differential charge density analysis shows that the tensile strain weakens the electronic reconfiguration of Ge-O bonds, reduces the bonding strength, and weakens the jump dipole moment; the compressive strain enhances the electron accumulation and orbital coupling, and improves the responsiveness of the material to low-energy light. The absorption spectra show that the biaxial strain decreases and blueshifts the absorption peaks, reflecting the broadening of the bandgap, while the compressive strain strengthens and redshifts the absorption peaks; in the reflectance spectra, the tensile strain diminishes the reflection peaks, while the compressive strain strengthens the reflection intensity. The study provides a theoretical basis for the energy band engineering of two-dimensional GeS materials as well as the application of flexible optoelectronic devices and tunable spectral sensors.