Strain Modulated Electronic, Mechanical, and Optical Properties of the Monolayer PdS₂, PdSe₂, and PtSe₂ for Tunable Devices

We study the electronic, mechanical, and optical properties of the monolayer PdS2, PdSe2, and PtSe2 under mechanical strains of various magnitudes and directions. It is found that the band structures of these materials are more sensitive to biaxial strains. Moreover, the Young’s modulus of all three materials are calculated in the a and b directions. Simulation results show the Young’s moduli of monolayer PdS2, PdSe2, and PtSe2 are 116.4, 58.5, and 115.9 GPa in the a direction and 166.5, 123.6, and 117.7 GPa in the b direction. We analyze the peak shift of the real (ϵ1) and imaginary (ϵ2) parts of the complex dielectric constants for these three materials. We found that the peak of the complex dielectric constant red-shifts toward lower energy, and ϵ1(0) monotonously increases with the compressive and tensile strains increase. Among these three materials, PdS2 exhibits excellent electronic and optical tunability under tensile strains; for example, the peak wavelength of the imaginary dielectric constant can be adjusted from 2 to 1 eV when the strain varies from 0% to 10%, leading to an approximately 5% red-shift in wavelength per 1% mechanical tensile strain. The results indicate that these monolayer materials will have potential applications in tunable nano-electromechanical devices.