Tunable Electrical and Optical Performance of Monolayer HfX2 (X=S, Se) by Strain

2D transition metal dichalcogenides (TMDs) have wide range of exceptional properties compared with graphene that has the potential in the application of optoelectronic devices due to the tunable electrical and optical performance. In this work, the electronic and optical properties of monolayer HfS
2
and HfSe
2
under uniaxial and biaxial strain are investigated by density functional theory(DFT). The results show that the bandgap of monolayer HfX
2
(X=Se, S) will increase significantly with the enhance of tensile force while decreasing linearly with the raise of compressive force in great linearity by adding various gradients of strain in uniaxial and biaxial directions, which can potentially make the monolayer HfX
2
(X=Se, S) become good semiconductor material. Besides, the work function of HfX
2
increases (decreases) significantly with tensile (compressive) strain. For the optical properties, the absorption coefficient of different wavelength change regularly with different strain. The present findings make monolayer HfX
2
(X=S, Se) suitable for the potential applications in various semiconductor and optoelectronic devices.