Reducing Threshold of Ferroelectric Domain Switching in Ultrathin Two-Dimensional CuInP<sub>2</sub>S<sub>6</sub> Ferroelectrics via Electrical–Mechanical Coupling
Weijie Yang, Shengjie Chen, Xiangdong Ding, Jun Sun, Junkai Deng
Abstract
Room-temperature out-of-plane two-dimensional ferroelectrics have promising applications in miniaturized non-volatile memory appliances. The feasible manipulation of polarization switching significantly influences the memory performance of ferroelectrics. However, conventional high-voltage-induced polarization switching inevitably generates charge injection or electric breakdown, and large-mechanical-loading-induced polarization switching may damage the structure of ferroelectrics. Hence, decreasing critical voltage/loading for ferroelectric polarization reversal is highly required. Herein, using atomic force microscopy experiments, the ferroelectric domain switching via both electric field and mechanical loading was demonstrated for an ultrathin (∼4.1 nm) CuInP 2 S 6 nanoflake. The relevant threshold voltage/loading for polarization switching was ∼ –5 V/1095 nN, resulting from the electric field and flexoelectric effect, respectively. Finally, the electrical–mechanical coupling was adopted to reduce the threshold voltage/loading of CuInP 2 S 6 significantly. It can be explained by the Landau–Ginzburg–Devonshire double-well model. This effective way for easily tuning the polarization states of CuInP 2 S 6 opens up new prospects for mechanically written and electrically erased memory devices.