Room-Temperature NO<sub>2</sub> Sensing of CVD-Modified WS<sub>2</sub>–WSe<sub>2</sub> Heterojunctions
Abderrahim Moumen, Rajashree Konar, Dario Zappa, Eti Teblum, Gilbert Daniel Nessim, Elisabetta Comini
Abstract
High Resolution Image Download MS PowerPoint Slide Two-dimensional (2D) semiconducting heterojunction chemical sensors are in high demand because of their enhanced response, stability, and selectivity. However, fine-tuning heterojunctions using vapor deposition growth still needs further research. Our present study focuses on the ambient pressure chemical vapor deposition (CVD) synthesis of hexagonal tungsten sulfide-tungsten selenide (WS 2 –WSe 2 ) p–p heterojunctions (as a 2D–2D arrangement). We use the liquid-phase exfoliation method to disperse bulk WS 2 and WSe 2 and decorate large flakes of WS 2 with smaller WSe 2 nanosheets in CVD. Electron microscopy and related surface investigations reveal their homogeneity on drop-casting. Two drops from the exfoliated heterojunction dispersion were drop-cast on a transducer to study the NO 2 response and related sensing properties. The sensor showed long-term stability (>2 months), even at high humidity levels (40–90%). The gas-sensing properties of this layered p–p heterojunction-based nanocomposite strongly suggest an affinity toward NO 2 gas, leading to improved response, high stability, independent of humidity effects, and high selectivity.