利用软X射线扫描相干衍射成像进行谱学及磁学测量的研究

Ptychography (or named scanning coherent diffractive imaging) is a coherent diffractive imaging technique that has the potential to imaging specimens with nanoscale spatial resolution, using highly coherent X-ray. Since ptychography can be performed on non-crystalline samples and can deliver high resolution images, it has been widely used in biological, environmental, and material sciences, and has been an extremely important development direction in X-ray microscopy field. Compared to the typically ~30 nm spatial resolution of current scanning transmission X-ray microscopes (STXMs), ptychography can improve the spatial resolution to a few nanometers in the soft X-ray region. However, ptychography method is mainly used for sample imaging at present. Using soft X-ray ptychography to measure spectroscopy and magnetism of the specimens has just emerged at a few synchrotron radiation light sources such as Advanced Light Source, and is still a blank in China. This project aims to develop soft-X-ray-ptychography-based near edge X-ray fine structure ( including near edge X-ray absorption fine structure and near edge X-ray refraction fine structure) method and soft-X-ray-ptychography-based X-ray magnetic circular dichroism (XMCD) method at the BL08U1-A beamline (soft X-ray spectromicroscopy beamline) in Shanghai Synchrotron Radiation Facility, in order to characterize and study the chemistry and magnetism of the specimens with spatial resolution of a few nanometers. The resolution of the soft X-ray spectromicroscopy beamline can be highly improved.

X射线扫描相干衍射成像方法（Ptychography）是利用高相干的X光，对样品进行纳米级分辨率成像的X射线显微成像技术。其在生物、环境、医学以及材料等研究领域有着广阔的应用前景，是X射线显微成像领域极其重要的发展方向。在软X射线波段，相比较于扫描透射X射线显微成像方法通常可达到的30nm分辨率，ptychography可以将分辨率提高至几个纳米。然而，ptychography方法目前仍然主要用于对样品成像，将其在软X射线波段用于对样品进行谱学以及磁学测量的相关研究，在国际上刚刚兴起，在国内尚属空白。本项目旨在上海光源软X射线谱学显微线站（BL08U1-A）发展基于软X射线ptychography的X射线近边精细结构谱(包括吸收和折射)以及X射线磁圆二色（XMCD）的实验测量方法，以对样品实现纳米分辨率的元素分布和化学过程分析，以及磁学特性分析，大幅提高软X射线谱学显微成像的分辨率。

软X射线扫描相干衍射成像方法(ptychography)的空间分辨率可以达到几个纳米，在生物科学、环境科学、材料科学、以及能源科学等研究领域有着广阔的应用前景。本项目在上海光源软X射线谱学显微线站(BL08U1-A)开展基于软X射线ptychography的高空间分辨率的谱学显微成像方法学的研究。申请人经过两年的研究，在多个方面取得了良好的研究成果。当前已经完成了对BL8U1-A原有ptychography实验平台的升级改造和优化，实现了基于软X射线ptychography的谱学显微成像方法，包括双能衬度程序和能量堆栈图像，空间分辨率优于10纳米；初步实现了基于软X射线ptychography的磁圆二色谱学显微成像技术，可用于研究磁性材料样品；针对谱学ptychography实验方法原始数据量较大，相位恢复迭代计算量大且费时的问题，完成了数据自动处理流水线的初步开发，集成了利用GPU进行加速的重建程序，大幅提高了数据处理的自动化以及重建速度，减少了对人工的依赖。目前基于软X射线ptychography的高空间分辨率的谱学显微成像方法已经对用户开放。