The theoretical prediction of the structural characteristics and SO2 adsorption-sensing properties of pristine HfS2 and TM-doped HfS2 monolayers (TM = Ni, Pd, or Pt)

This work investigated the structural characteristics and SO2 adsorption-sensing properties of pristine HfS2 and TM-doped HfS2 monolayers (TM = Ni, Pd, or Pt) using DFT and NEGF-based calculations. The most stable doping site for the adatoms is found to be the hollow site between three adjacent sulfur atoms. Our results demonstrate weak physisorption of SO2 molecules on the pristine HfS2. The SO2 adsorption stability on the Ni-, Pd-, and Pt-doped HfS2 monolayers significantly improves compared with the pristine one. The calculated recovery times of Ni-doped, Pd-doped, and Pt-doped HfS2 monolayers after SO2 adsorption are 208.3 s, 92 s and 5.4 s, respectively. In addition, we designed SO2 sensor models containing Au-electrodes to investigate the influence of TM-doped HfS2 monolayers (TM = Ni, Pd, or Pt), as the material of the scattering region, on their I-V relationship and sensitivity. The sensitivities of TM-doped HfS2 monolayer (TM = Ni, Pd, or Pt)-based sensors are calculated to be 28%, 41%, and 44%, respectively. Our results suggest that Pd-doped and Pt-doped HfS2 monolayers are new promising 2D materials for designing SO2 sensors with high sensitivity and repeatability.