Ma L L, Chen W J, Wang Biao, Xiong W M, Zheng Yue
State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Sun Yat-sen University, 510275 Guangzhou, People's Republic of China. Micro and Nano Physics and Mechanics Research Laboratory, School of Physics, Sun Yat-sen University, 510275 Guangzhou, People's Republic of China.
J Phys Condens Matter. 2020 Jan 16;32(3):035402. doi: 10.1088/1361-648X/ab4831. Epub 2019 Sep 26.
Recent experiments have demonstrated the existence of vortex or flux-closure domains in ferroelectric nanostructures, which are attractive to develop high-density data storage and novel configurable electronic devices. However, it remains challenging to stabilize in-plane vortex or flux-closure domains in ferroelectric film for the absence of a lateral geometry confinement. Based on a 3D phase field model, here we show that stabilization of isolated or interacting in-plane vortices in ferroelectric film can be achieved via applying a mechanical tip-force. The formation of such dipole vortices is caused by a conjoint effect of the tip-force-induced depolarization effect and in-plane strain. The effects of factors like film thickness, misfit strain, tip force and temperature on the vortex formation are systematically revealed and summarized as phase diagrams. The interaction between tip-induced vortices is also investigated. It is found that as the two tips get closer than the critical distance, the two initially isolated vortices become coupled, with identical or opposite chirality, depending on the distance between the two tips. A maximum data storage density of isolated in-plane vortices in ferroelectric thin film is estimated to be ~1 Tb in. Our work thus demonstrates a mechanical strategy to stabilize dipole vortices, and provides a comprehensive insight into the characteristics of ferroelectric film under a mechanical tip force.
最近的实验已经证明了铁电纳米结构中涡旋或通量闭合畴的存在，这对于开发高密度数据存储和新型可配置电子器件具有吸引力。然而，由于缺乏横向几何限制，在铁电薄膜中稳定面内涡旋或通量闭合畴仍然具有挑战性。基于三维相场模型，我们在此表明，通过施加机械尖端力，可以实现铁电薄膜中孤立或相互作用的面内涡旋的稳定。这种偶极涡旋的形成是由尖端力诱导的去极化效应和面内应变的联合作用引起的。系统地揭示了薄膜厚度、失配应变、尖端力和温度等因素对涡旋形成的影响，并总结为相图。还研究了尖端诱导涡旋之间的相互作用。发现当两个尖端之间的距离小于临界距离时，两个最初孤立的涡旋会耦合，根据两个尖端之间的距离，其手性相同或相反。估计铁电薄膜中孤立面内涡旋的最大数据存储密度约为1太比特每平方英寸。因此，我们的工作展示了一种稳定偶极涡旋的机械策略，并提供了对机械尖端力作用下铁电薄膜特性的全面洞察。
