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)

Abstract

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.