Gnanasekaran Karthikeyan, de With Gijsbertus, Friedrich Heiner
Laboratory of Materials and Interface Chemistry, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, Eindhoven, The Netherlands.
Institute for Complex and Molecular System, Eindhoven University of Technology, Eindhoven, The Netherlands.
R Soc Open Sci. 2018 May 2;5(5):171838. doi: 10.1098/rsos.171838. eCollection 2018 May.
Many functional materials are difficult to analyse by scanning transmission electron microscopy (STEM) on account of their beam sensitivity and low contrast between different phases. The problem becomes even more severe when thick specimens need to be investigated, a situation that is common for materials that are ordered from the nanometre to micrometre length scales or when performing dynamic experiments in a TEM liquid cell. Here we report a method to optimize annular dark-field (ADF) STEM imaging conditions and detector geometries for a thick and beam-sensitive low-contrast specimen using the example of a carbon nanotube/polymer nanocomposite. We carried out Monte Carlo simulations as well as quantitative ADF-STEM imaging experiments to predict and verify optimum contrast conditions. The presented method is general, can be easily adapted to other beam-sensitive and/or low-contrast materials, as shown for a polymer vesicle within a TEM liquid cell, and can act as an expert guide on whether an experiment is feasible and to determine the best imaging conditions.
许多功能材料由于其束敏感性以及不同相之间的低对比度，难以通过扫描透射电子显微镜（STEM）进行分析。当需要研究厚样品时，这个问题会变得更加严重，对于从纳米到微米长度尺度有序排列的材料或者在透射电子显微镜液体池中进行动态实验时，这种情况很常见。在此，我们以碳纳米管/聚合物纳米复合材料为例，报告一种优化厚且对束敏感的低对比度样品的环形暗场（ADF）STEM成像条件和探测器几何结构的方法。我们进行了蒙特卡罗模拟以及定量ADF-STEM成像实验，以预测和验证最佳对比度条件。所提出的方法具有通用性，可以很容易地应用于其他对束敏感和/或低对比度的材料，如透射电子显微镜液体池中的聚合物囊泡所示，并且可以作为判断实验是否可行以及确定最佳成像条件的专业指南。
