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.

在过去的十年中，铁电畴演化的机械控制引起了极大的兴趣。然而，双向 180° 机械切换，即机械写入然后擦除铁电纳米域的完整循环，尚未在尖端膜结构中实现。在这里，通过基于第一性原理的分子动力学模拟，我们证明了当铁电薄膜的筛选条件和尖端加载力在适当的窗口内时，尖端薄膜结构中的双向 180° 机械切换是可能的。这种切换利用了挠曲电场和被忽视的有效偶极场之间的微妙竞争。有效偶极场在小尖端力下占主导地位，并触发从向下的单域状态切换到向上的多域状态，而挠曲电场在相对较大的尖端力下占主导地位并能够实现反向切换。通过施加具有交替变化的强度的尖端力脉冲来实现双向机械切换。偶极-偶极相互作用动力学在机械切换中起重要作用。