Measurement of the chemical composition of nanostructures by quantification of Z-contrast in scanning-transmission electron microscopy

通过扫描透射电子显微镜中 Z 对比度的量化来测量纳米结构的化学成分

• 批准号: 134655250
• 负责人: Professor Dr. Andreas Rosenauer
• 金额: --
• 依托单位: Institut für Festkörperphysik (IFP)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2009
• 资助国家: 德国
• 起止时间: 2008-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/134655250?language=en
• 关键词: Measurement; chemical; composition; nanostructures; quantification

In project we developed a method to precisely analyse the chemical composition in a sample using scanning-transmission electron microscopy (STEM). The method wich is based on a direct comparsion of the experimental high-angle annular dark field (HAADF) intensity with simulations was already applied to many different materials.So far, the intensity was measured by integrating the scattered intensity over a certain angular range which is defined by the camera length and the geometry of the detector. In this renewal proposal we aim at a measurement of STEM intensity as a function of the scattering angle. The angle-dependence of the scattered intensity is not only influenced by the chemical concentration but also by the type of the scattering process (e.g. thermal-diffuse scattering or scattering at static atomic displacements) and by distortions of the crystal lattice. Therefore, the scattering intensity measured with selected detection angles contains additional information which allows for measuring two or more experimental parameters (e.g. thickness and chemical concentration) at the same time. For this purpose we suggest to install a motor-driven diaphragm directly above the HAADF detector in the microscope.The new method will be able to measure the local chemical concentration of a single element (e.g. In in InGaN) and the local specimen thickness or the local chemical concentrations of two elements (e.g. In and Al in InAlGaN) at the same time. Our priliminary studies using a prototype diaphragm show that our method allows for either making strain fields visible or performing quantitative chemical analyses without strain-induced artifacts. The studies further show a difference in the angle-dependend intensity distribution between experiment and simulation at angles smaller than 40 mrad. A main topic of this proposal is the quantification of the small-angle scattering intensity, which includes the investigation of plasmon scattering and its implementation into our simulation software using different apporaches.The method will contribute to various cooperations and projects by its application to investigate quantum dots, quaternary layers, segregation effects, nano particles of non-homogeneous composition, nano-pourous gold and SiGe MOSFETs. Thus, the project will significantly contribute to the understanding of semiconductor nanostructures and catalysists by the suggested method.

在项目中，我们开发了一种使用扫描透射电子显微镜（STEM）精确分析样品化学成分的方法。该方法基于实验高角环形暗场（HAADF）强度与模拟结果的直接比较，已经应用于许多不同材料。到目前为止，强度是通过在一定角度范围内的散射强度积分来测量的，该角度范围是由相机长度和探测器的几何形状定义的。在这个更新方案中，我们的目标是测量STEM强度作为散射角的函数。散射强度的角度依赖性不仅受化学物质浓度的影响，还受散射过程类型（如热扩散散射或静态原子位移散射）和晶格畸变的影响。因此，用选定的探测角度测量的散射强度包含额外的信息，允许同时测量两个或更多的实验参数（例如厚度和化学浓度）。为此，我们建议在显微镜的HAADF检测器正上方安装一个电机驱动的膜片。新方法将能够同时测量单一元素的局部化学浓度（例如InAlGaN中的In）和局部样品厚度或两种元素的局部化学浓度（例如InAlGaN中的In和Al）。我们使用原型膜片进行的初步研究表明，我们的方法既可以使应变场可见，也可以在没有应变诱发伪影的情况下进行定量化学分析。研究进一步表明，在小于40 mrad的角度下，实验与模拟的随角度变化的强度分布存在差异。本文的一个主要课题是小角散射强度的量化，包括等离子体散射的研究及其在我们的模拟软件中使用不同方法的实现。该方法将通过其应用于研究量子点，第四层，偏析效应，非均匀组成的纳米颗粒，纳米多孔金和SiGe mosfet，为各种合作和项目做出贡献。因此，该项目将通过建议的方法对半导体纳米结构和催化剂的理解做出重大贡献。

项目成果

Angle-resolved STEM using an iris aperture: Scattering contributions and sources of error for the quantitative analysis in Si.

使用虹膜孔径的角度分辨 STEM：Si 定量分析的散射贡献和误差源

• DOI: 10.1016/j.ultramic.2020.113175
• 发表时间: 2021
• 期刊: Ultramicroscopy
• 影响因子: 2.2
• 作者: Tim Grieb;Florian F. Krause;Knut Müller-Caspary;Saleh Firoozabadi;Christoph MahrMarco Schowalter;Andreas Beyer;Oliver Oppermann;Kerstin Volz;Andreas Rosenauer
• 通讯作者: Andreas Rosenauer