Mahr Christoph, Grieb Tim, Krause Florian F, Schowalter Marco, Rosenauer Andreas
Institute of Solid State Physics, University of Bremen, Otto-Hahn-Allee 1, D-28359 Bremen, Germany; MAPEX Center for Materials and Processes, University of Bremen, Bibliothekstr. 1, D-28359 Bremen, Germany.
Institute of Solid State Physics, University of Bremen, Otto-Hahn-Allee 1, D-28359 Bremen, Germany; MAPEX Center for Materials and Processes, University of Bremen, Bibliothekstr. 1, D-28359 Bremen, Germany.
Ultramicroscopy. 2022 Jun;236:113503. doi: 10.1016/j.ultramic.2022.113503. Epub 2022 Mar 7.
The measurement of electric fields in scanning transmission electron microscopy (STEM) is a highly investigated field of research. The constant improvement of spatial resolution in STEM and the development of new hardware for the fast acquisition of diffraction patterns even paved the way for the measurement of atomic electric fields. Although the basic principle that an electric field leads to a tilt of the focussed electron probe that can be detected as a shift of the diffraction pattern in the back focal plane of the objective lens seems quite simple, many challenges arose in the measurement of fields in a quantitative way. In the present study we investigate whether a shift of the diffraction pattern that occurs at an interface between two materials can be related to the electric field which is caused by the difference of the mean inner potentials of the two materials. To this end, experiments and simulations are compared. It is demonstrated that the difference in mean inner potential has an influence on the observed effect, but a quantitative interpretation is difficult. The influence of image recording effects such as shot noise and the modulation transfer function are investigated as well as further effects such as e.g. sample tilt. In addition, the influence of the observed effect on a strain measurement is shown.
扫描透射电子显微镜（STEM）中电场的测量是一个受到广泛研究的领域。STEM空间分辨率的不断提高以及用于快速获取衍射图案的新硬件的开发，甚至为原子电场的测量铺平了道路。尽管电场会导致聚焦电子探针倾斜，而这种倾斜可被检测为物镜后焦平面中衍射图案的偏移这一基本原理看似相当简单，但在以定量方式测量电场时却出现了许多挑战。在本研究中，我们探究了在两种材料的界面处出现的衍射图案偏移是否与由这两种材料平均内势差所引起的电场有关。为此，我们对实验和模拟进行了比较。结果表明，平均内势差对观察到的效应有影响，但定量解释却很困难。我们研究了图像记录效应（如散粒噪声和调制传递函数）以及其他效应（如样品倾斜）的影响。此外，还展示了观察到的效应对应变测量的影响。
