Role of defect engineering in revealing the electronic and sensing applications of Janus WSSe monolayer

Abstract

In the vicinity of DFT, a systematic study of the structural and electronic properties of pristine 2D WSSe and chalcogen vacancy-defected monolayer has been performed. Pristine WSSe reveals semiconducting character with 1.63 eV direct band gap. The S_vc, Se_vc, and S–Se_vc monolayers also exhibit semiconductor character with a decreased band gap. Further, the sensing mechanism of all monolayers toward CH₄, C₃H₈, and C₄H₁₀ indicate significant adsorption energy (of −0.5 to −0.7 eV) and charge transfer (up to 0.171e). These findings reveal higher binding strength through the physisorption of C₃H₈ and C₄H₁₀ with strong interaction. Besides, the restricted recovery time suggests the fastest desorption process for WSSe sensing devices with re-applicability. The impurity states in the electrostatic potential and significant alterations (ΔΦ of ∼1.07 to 1.16 eV) for all adsorbents enable WSSe as Φ-type gas sensor. Besides, I–V analysis exhibits the NDR behavior with remarkable PVCR for pristine and defected WSSe before adsorption, prompting monolayer application as a tunnel diode with lower switching time. Also, the NDR existence for all monolayers after adsorption attribute to high conductance and crucial sensing response toward effective gas detection along with the inflection point at particular bias. Lastly, optical responses of the dielectric function and absorption spectra signify that WSSe effectively interactes with incident photon energy (mainly in the VIS-UV region) to the activation of gas molecules, which highlights advances of WSSe as an optical gas sensor. Particularly, better sensing performances are observed for defected monolayers in comparison to pristine monolayers. Inclusively, overall interesting sensing analysis indicates that the WSSe monolayer is a promising candidate for CH₄, C₃H₈, and C₄H₁₀ detection at room temperature.