Effect of Non-Metal Doping on the Optoelectronic Properties of Monolayer 1T-HfS2 under Strain: A First-Principles Study

This paper modulates the band structure of 1T-HfS2 by doping with non-metallic atoms of group IIIA to VIIA of the second period (B, C, N, O, and F atoms) and using biaxial tensile strain in the x–y direction. The optoelectronic properties of the material, including the formation energy, electronic structure, and complex dielectric function, are analyzed based on the first-principles calculations. The results show that n‑type doping is achieved in B-doping and F-doping, and C-doping, N-doping, and O-doping belong to p‑type doping. When B and C atoms are doped, the strong hybridization between the impurity atoms and the Hf atoms causes impurity levels to be introduced in the forbidden band, which has an essential effect on the system's conductivity. Under biaxial tensile strain, the bandgaps of the system of the N-doping, O-doping, and F-doping increase, and the type of bandgap changes from indirect to direct, which improves the luminous efficiency of the material. The formation energy calculations also show that the N-doping and O-doping are easier to form with –2.108 and –2.813 eV, respectively. In addition, the study of the optical properties shows that tensile strain shifts the optical properties of all systems in the low-energy region. The results provide a theoretical reference for applying monolayer 1T-HfS2 in microelectronic devices.