Effects of external electric field on the sensing property of volatile organic compounds over Janus MoSSe monolayer: a first-principles investigation

Janus 2D transition metal dichalcogenide (TMD) is a new generation 2D material with a unique asymmetric structure. This asymmetric structure (or out-off plane symmetric geometry) of Janus 2D TMD has been reported to yield tunable electronic properties through strain and electric field, which can also be applied in gas sensing. In this work, we performed DFT calculations to investigate the gas sensing property of cyclohexane and acetone on MoS(2) and Janus MoSSe monolayers under external electric fields. Our results show that cyclohexane possesses slightly larger adsorption energy on pristine MoS(2) and Janus MoSSe monolayers than acetone without external electric fields. After applying the external electric fields, the adsorption energy for cyclohexane on MoS(2) shows no enhancement. However, the adsorption energy of acetone shows the most substantial enhancement on the Janus MoSSe monolayer. We found that the dipole moment orientations of adsorbates and the monolayer can strongly interact with the external electric fields. Hence, the combination of polar adsorbate and polar material, i.e., acetone and Janus MoSSe, demonstrates the most vital sensitivity under the applied bias. On the other hand, the non-polar adsorbate and non-polar material combination show a negligible effect on external bias. These findings can be applied to the design of gas sensors in the future through polar materials.