High-Resolution Field Mapping using Electron Ptychography

直接可视化的原子结构和铁电有序的材料在原子薄的限制是令人兴奋的，不仅从基础物理学的角度来看，但也是关键的应用，包括信息存储和逻辑技术中使用的铁电和铁磁材料的特性。超快直接探测器是一种新兴的高分辨率相位成像技术，叠联成像技术因其在超分辨率成像中的潜在应用而引起了X射线和电子界的极大兴趣。重叠关联是一种基于扫描同轴全息术的相位恢复方法，最初由Hoppe提出。该方法使用辐射源照射样品，并记录一系列衍射图案作为照射位置的函数，以使用迭代算法恢复样品出射平面波函数。电子重叠关联技术可以在低温下以前所未有的高分辨率和灵敏度对功能材料（如二维铁性薄膜）内的铁性有序进行高灵敏度观察。在本研究项目中，我们将开发一种新的有序场成像，使用电子重叠关联技术和"大数据"处理方法，并通过加速其在功能材料中的应用来开拓机会。将通过与详细的图像模拟进行比较来提取磁化配置的定量成像。结合层析成像方法，电磁场映射将有可能扩展到纳米结构材料内部的三维场映射。该项目的成功也可能为下一代纳米器件带来令人兴奋的机会。

Direct visualisation of atomic structures and ferroic orderings in materials at the atomically thin limit is exciting not only from a fundamental physics perspective but is also critical for the characteristics of ferroelectric and ferromagnetic materials used in applications that include information storage and logic technologies. With ultrafast direct detectors, a new emerging high-resolution phase imaging technique, so-called ptychography has attracted considerable interest from both X-ray and electron communities for its potential applications in super-resolution imaging. Ptychography is a phase recovery method based on scanning in-line holography, as originally proposed by Hoppe. This approach uses a radiation source to illuminate a sample and records a series of diffraction patterns as a function of the illumination position to recover the sample exit plane wavefunction using iterative algorithms. Electron ptychography can potentially enable high-sensitivity observations of the ferroic-orderings within functional materials (such as 2D ferroic thin films) at unprecedentedly high resolution and sensitivity at a low temperature. In this research project, we will develop a novel ordering field imaging using electron ptychography together with "big data" processing methods and exploit opportunities by accelerating its application in functional materials. The quantitative imaging of the magnetization configurations will be extracted by comparison with detailed image simulations. Combined with tomographic methods, the electromagnetic field mapping will be potentially extended into three-dimensional field mapping inside nanostructured materials. The success of this project can also lead to exciting opportunities in next-generation nanoscale devices.