Photoelectric structure and magnetic changes caused by niobium disulfide adsorbing (non)-metal atoms under defects.

CONTEXT: The property transition between metal and semiconductor is the key to improving the properties of transition metal dichalcogenides (TMDCs). The adsorption of the NbS2 compound in the defect state was adjusted for the first time. The hybrid system overwrites the original surface mechanism of NbS2 and induces indirect band gaps. This modulation mode makes NbS2 convert into a semiconductor and effectively improves the catalytic activity of the material in the system. In addition, the original local magnetic moment of the compound is concentrated in the vacancy region and is improved. The optical properties of the adsorption system indicate that NbS2 compounds can be effectively applied in visible and low-frequency ultraviolet regions. This provides a new idea for the design of the NbS2 compound as a two-dimensional photoelectric material.

METHODS: In the study, we assume that only one atom is adsorbed on the NbS2 supercell of the defect, and the distance between the two adjacent atoms exceeds 12.74 Å, so the interaction between atoms is ignored in the study. Adsorbed atoms include nonmetallic elements (H, B, C, N, O, F), metallic elements (Fe, Co), and noble metal elements (Pt, Au, Ag). The density functional theory (DFT) was used in the experiment. The non-conservative pseudopotential method was used in the calculation to optimize the crystal structure geometrically. The approximate functional is Heyd-Scuseria-Ernzerhof (HSE06). The calculation method includes the spin-orbit coupling (SOC) effect. The crystal relaxation optimization uses a 7 × 7 × 1 k point grid to calculate niobium disulfide's photoelectric and magnetic properties. A vacuum space of 15Å is introduced in the direction outside the plane, and the free boundary condition is adopted to avoid the interaction between atomic layers. For the convergence parameter setting, the interatomic force of all composite systems is less than 0.03 eV/Å, and the lattice stress is less than 0.05 Gpa.