Piezotronic Effect Enhanced Flexible Humidity Sensing of Monolayer MoS₂

We report the piezotronic effect on the performance of humidity detection based on a back-to-back Schottky contacted monolayer MoS₂ device. By introducing an upswept mechanical strain, the in-plane electrical polarization can be induced at the MoS₂/metal junction region. The polarization charges can modify the Schottky barrier height at the interface of MoS₂/metal junction, subsequently improving the sensitivity of the humidity sensing. An energy band diagram is proposed to explain the experiment phenomenon of the humidity sensor. This work provides a simple way to enhance the sensitivity of ultrathin two-dimensional-materials-based sensors by the piezotronic effect, which has great potential applications in electronic skin, human-computer interfacing, gas sensing, and environment monitoring.