Electronic and optical properties of transition-metal (TM=Sc, Ni, Cu, Zn) adsorbed monolayer SnSe2

Based on the first principles calculations, we have studied the electronic and optical properties of 3 d transition metal atoms (TM = Sc, Ni, Cu, Zn) adsorbed on the surface of monolayer SnSe2. The results show that SnSe2 adsorbed with Ni and Cu are direct band gap semiconductors with band gaps of 0.324 eV and 0.501 eV, respectively, while SnSe2 adsorbed with Sc and Zn are indirect band gap semiconductors with band gaps of 0.728, 0.531 eV. The band gaps of all adsorbed structures are reduced to different degrees compared to the pristine SnSe2. After the adsorption of transition metal atoms by SnSe2, the imaginary part of the dielectric function shifts to the lower energy region and the peak decreases compared to the pristine SnSe2. The absorption coefficients of TM/SnSe2 are significantly higher in the visible (1.64 eV–3.19 eV) and infrared ranges, with Ni/SnSe2 having a larger absorption coefficient near 1.64 eV than the other TM atoms. In the z-direction, Sc/SnSe2 has a peak at 2.51 eV with an absorption coefficient of 7.83 × 104/cm. The results show that the optical properties of SnSe2 can be adjusted by adsorption of transition metal atoms to improve absorption in the long-wave light range, which has potential applications in the field of photoelectric devices.