Enhancement of resolution and precision of TEM imaging by scanning illumination

通过扫描照明提高 TEM 成像的分辨率和精度

• 批准号: 392948259
• 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: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/392948259?language=en
• 关键词: Enhancement; resolution; precision; TEM; imaging

In transmission electron microscopy (TEM), mainly two imaging modes are differentiated: Conventional TEM (CTEM), which uses a plane coherent electron wave to illuminate the specimen, and scanning TEM (STEM), where the electron beam is scanned over the specimen and scattered electrons are registered by a detector. CTEM has the advantage of direct imaging which is not influenced by errors of positioning the electron beam. In contrast, as STEM is an incoherent imaging mode, the interpretation of images is easier and it provides a better spatial resolution.We were able to demonstrate in an article published in Phys. Rev. Lett. by experiment and simulation that the new imaging mode ISTEM (imaging STEM), which applies scanning illumination in the CTEM imaging mode, combines advantages of CTEM and STEM. It provides better spatial resolution than CTEM, interpretation of contrast patterns is easier and there is no influence of errors in positioning the electron beam. However, the advantages of ISTEM are accompanied by the disadvantage of a more difficult practicability. A first goal of the project is to improve the applicability of ISTEM by writing dedicated scripts to operate and adjust the microscope as well as reducing the contamination of the sample. In addition, advantages of ISTEM imaging that have only been shown by simulation so far will be demonstrated experimentally. These advantages include the higher precision of measuring the positions of atom columns, as well as the outstanding possibilities to image light atom columns in direct vicinity of heavy atom columns. In a recent publication of Prof. L. Allen et al. in Australia it was suggested to apply ISTEM for elemental analysis by energy filtered imaging with reduced artifacts. This approach will be tested in cooperation with the ER-C Jülich.The advantages of ISTEM imaging will be demonstrated using technologically relevant material systems that are connected with highly topical problems. The improved precision of the measurement of atom column positions will be applied to measure polarization domains in only a few nanometers thick ferroelectric tunnel barriers which are potential candidates for application in memory devices. Particularly, we plan to investigate the switching behavior of these barriers using in-situ applied electric fields. In addition, the possibilities of ISTEM to image light atom columns will be applied to measure tilts of oxygen-octahedra across the interfaces between different perovskite materials. Further applications are the measurement of spontaneous wrinkling of lattice planes in Te nanowires which can be applied in NO2 sensors, as well as the investigation of lattice strain close to the surface of nanoporous gold, which influences the catalytic activity of this material system.

在透射电子显微镜 (TEM) 中，主要区分两种成像模式：传统 TEM (CTEM)，它使用平面相干电子波照射样品；扫描 TEM (STEM)，其中电子束在样品上扫描并扫描样品。 CTEM 具有直接成像的优点，不受电子束定位误差的影响，而 STEM 是一种非相干成像模式，因此图像的解释更容易，并且提供了更好的空间。我们通过实验和模拟在Phys Rev. Lett上发表的文章中证明，在CTEM成像模式下应用扫描照明的新成像模式ISTEM（成像STEM）结合了CTEM和STEM的优点。它提供了比 CTEM 更好的空间分辨率，对比图案的解释更容易，并且不受电子束定位误差的影响。然而，ISTEM 的优点也伴随着更困难的实用性的缺点。是为了通过编写专用脚本来操作和调整显微镜以及减少样品污染，提高 ISTEM 的适用性。此外，迄今为止仅通过模拟显示的 ISTEM 成像的优点将通过实验得到证明。 L. Allen 教授等人最近在澳大利亚发表的一篇文章中建议应用 ISTEM 来测量原子柱位置的更高精度，以及对紧邻重原子柱进行成像的出色可能性。用于能量元素分析这种方法将与 ER-C Jülich 合作进行测试。 ISTEM 成像的优势将通过与高度热门问题相关的技术相关材料系统来证明。原子柱测量的精度得到提高。这些位置将用于测量仅几纳米厚的铁电隧道势垒中的极化域，这些势垒是存储器件中应用的潜在候选者，特别是，我们计划使用原位施加电场来研究这些势垒的切换行为。此外，ISTEM 成像光原子柱的可能性将用于测量不同钙钛矿材料之间界面上的氧八面体的倾斜度，进一步的应用是测量 Te 纳米线晶格平面的自发褶皱，这可应用于 NO2 传感器。 ，以及靠近纳米多孔金表面的晶格应变的研究，这影响了该材料系统的催化活性。