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

与具有自发磁化的铁磁体类似，铁电体是具有自发电极化的材料，可以通过外加电场进行切换。虽然铁电体已经有许多成熟的应用，利用其优越的压电、热释电和介电性能，但它们也被积极研究为下一代低功耗电子和神经形态计算中的存储器、晶体管和记忆元件的主要材料。这些应用需要纳米尺度的铁电体，它们的性质会发生巨大的变化。在纳米尺度上，铁电体呈现出复杂的奇异极化模式，具有有趣的拓扑结构。纳米级铁电畴对外部刺激的反应非常灵敏，导致介电性能的显著增强。也许更令人兴奋的是，局部打破大块材料对称性的畴壁，可以承载与它们分离的畴不同的属性，使它们能够作为自己的功能实体。我们利用电场随意创建和破坏畴的能力使其成为可重构电子器件的理想选择，推翻了我们的电子电路需要由固定硬件组件组成的经典想法，并导致畴壁纳米电子学领域的出现。然而，要利用它们的真正潜力，还有大量的基础物理学有待发现。由于畴壁通常只有几个原子厚且高度动态，因此在相关的空间和时间尺度上表征它们是必不可少的。该项目旨在研究铁电薄膜和超晶格中复杂的纳米级极化模式的物理特性，包括它们的结构、对应用刺激的响应以及它们对这些材料功能特性的影响。

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.