Improved anisotropy and piezoelectricity by applying in-plane deformation in monolayer WS2

摘要

Two-dimensional (2D) piezoelectric materials are mechanically flexible and atomically thin, enabling new emerging applications, such as wearable electronics, human-machine interfacing and strain sensors. The main obstacles for 2D piezoelectric materials are their low in-plane polarization and weak piezoelectric effect. In this study, we found piezoelectric effect in monolayer WS2 for the first time. Further, the in-plane uniaxial deformation was applied along the polarized armchair direction of WS2, giving rise to an enlarged in-plane polarization as evidenced from the higher Raman anisotropy of angle-resolved polarized Raman spectra. As a result, engineered WS2 exhibited a significantly improved dynamic piezoelectric signal by almost one order of magnitude. This study demonstrates a new strategy to artificially engineer monolayer WS2 by applying in-plane deformation for the larger anisotropy, higher polarization and more superior piezoelectricity, which can open up a new way for applications in 2D-based piezotronics and angle-dependent electronics.