Polarisation patterns in nanoscale ferroelectrics for low-power nano-electronics

与具有自发磁化作用的铁磁体类似，铁电体是一种具有自发电极化的材料，可以通过外加电场进行转换。虽然铁电材料已经有了许多成熟的应用，充分利用了它们优越的压电性、热释电性和介电性，但它们也是下一代低功率电子和神经形态计算中存储器、晶体管和记忆元件的主要材料。这些应用需要尺寸为纳米级的铁电体，其性质发生了显著变化。在纳米级，铁电体表现出复杂的奇异极化图案和有趣的拓扑结构。纳米尺度的铁电域对外界刺激非常敏感，导致介电性能显著增强。也许更令人兴奋的是，局部打破块状材料对称性的域壁可以拥有与它们分离的域壁不同的属性，使它们能够作为功能实体发挥作用。我们能够用电场随意地创建和摧毁磁区，这使它们成为可重新配置电子学的理想之选，颠覆了我们的电子电路需要由固定的硬件组件组成的经典想法，并导致了磁区壁纳米电子领域的出现。然而，要利用它们的真正潜力，还有大量的基础物理尚未揭开。铁电薄膜和超晶格中复杂的纳米级极化图案的物理特性，包括它们的结构、对外加刺激的响应以及它们对这些材料功能性质的影响。

By analogy with ferromagnets that have a spontaneous magnetisation, ferroelectrics are materials with a spontaneous electrical polarization that can be switched by an applied electric field. While ferroelectrics already have many well-established applications that exploit their superior piezoelectric, pyroelectric and dielectric properties, they are also actively studied as leading materials for the memory, transistors and memristive components in next generation low-power electronics and neuromorphic computing. These applications require ferroelectrics with dimensions at the nanoscale, where their properties change dramatically.At nanoscale, ferroelectrics exhibit complex exotic polarisation patterns with interesting topologies. Nanoscale ferroelectric domains are extremely responsive to external stimuli, leading to dramatic enhancements in dielectric properties. Perhaps even more excitingly, the domains walls, which locally break the symmetry of the bulk material, can host properties that are distinct from those of the domains that they separate, allowing them to act as functional entities in their own right. Our ability to create and destroy domains at will with electric fields makes them ideal for reconfigurable electronics, overturning the classic idea that our electronic circuits need to consist of fixed hardware components and leading to the emergence of the field of domain wall nanoelectronics.However, to harness their true potential there is a great deal of fundamental physics yet to uncover. As domain walls are usually only a few atoms thick and highly dynamic, it is essential to characterise them at the relevant spatial and temporal scale.This project will aim to investigate the physics of complex nanoscale polarisation patterns in ferroelectricthin films and superlattices, including their structure, response to applied stimuli and their effect on the functional properties of these materials.