Bidirectional mechanical switching window in ferroelectric thin films predicted by first-principle-based simulations
Jianyi Liu, Weijin Chen, Mengjun Wu, Fei Sun, Xiang Huang, Yue Zheng
Abstract
Abstract Mechanical control of ferroelectric domain evolution has attracted much interest over the past decade. Nevertheless, bidirectional 180° mechanical switching, i.e., a complete cycle of mechanical writing and then erasing of a ferroelectric nanodomain, has not yet been realized in tip-film architectures. Here, via first-principles-based molecular dynamics simulations, we demonstrate that bidirectional 180° mechanical switching is possible in tip-film architectures when screening condition of ferroelectric films and tip loading force are within an appropriate window. The switching utilizes a delicate competition between the flexoelectric field and an overlooked effective dipolar field. The effective dipolar field dominates at small tip force and trigger switching from a downward single-domain state to an upward poly-domain state, whereas the flexoelectric field dominates at relatively large tip force and enables a back-switching. Bidirectional mechanical switching is achieved by applying tip force pulses with alternatively varying strength. The dipole-dipole interaction dynamics play important roles in mechanical switching.