Strain Analysis by Nano-Beam Electron Diffraction using convergent electron nanoprobes

使用会聚电子纳米探针进行纳米束电子衍射应变分析

• 批准号: 240620893
• 负责人: Professor Dr. Knut Müller-Caspary
• 金额: --
• 依托单位: Department Chemie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2013
• 资助国家: 德国
• 起止时间: 2012-12-31 至 2016-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/240620893?language=en
• 关键词: Strain; Analysis; Nano; Beam; Electron

The measurement of strain fields in semiconductor crystals is a prerequisite for understanding physical processes in novel GeSi/Si or (Al)GaN/sapphire based heterostructures. This proposal firstly deals with the strain characterization in GeSi/Si islands for a basic understanding of Ge growth on Si. Secondly, strain fields and local Ge composition in GeSi-MOSFETs, being the basic module of high-performance computer processors, are to be measured as electronic properties drastically depend on the strain distribution. Thirdly, GaN/sapphire pseudosubstrates will be investigated with respect to strain since the efficiency of stress reduction in this layer highly determines efficiency and growth of subsequent InGaN/GaN LED active layers.In order to access these strain fields reliably, a scanning transmission electron microscopy (STEM) method for strain measurement is to be developed which exploits the positions of diffracted beams. In particular, a STEM probe is scanned over the specimen while a convergent beam electron diffraction (CBED) pattern is acquired at each scan point. With dedicated algorithms the disc-shaped CBED reflections can be detected accurately, leading to precisions of 7x10-4. To reduce the amount of experimental data drastically, these algorithms are to be implemented in a software for controlling the FEI Titan microscope used, so as to perform in-situ CBED pattern processing while the STEM probe is scanning. This not only enables 2D strain mapping but also provides the strain result immediately after data acquisition. One main prerequisite to exploit the full capability of the method for 2D mapping as to the spatial resolution of 0.5nm already achieved before is a drastic acceleration of CBED pattern acquisition which is not possible with conventional cameras. Therefore, test, modification and final installation of a delay-line detector are planned at the beginning of the project.To study strain fields of large extensions in the micron range, a STEM-precession method will be developed experimentally and in simulations. In precession mode, the incidence of the STEM probe is rotating on a cone while the resulting shift of the diffraction pattern is compensated for. In this way, strong variations of CBED intensities can be eliminated. In addition, the high strain sensitivity of high order reflections can be exploited as they appear brighter.Furthermore, distortions of the diffraction pattern due to post-magnifying lenses are to be measured and accounted for in strain measurements. This is important for the subsequent determination of the full strain tensor including shear.Finally, this technique is to be combined with the so-called Z-contrast signal, being sensitive to the chemical composition and to strain of the specimen. Consequently, the simultaneous measurement of both strain and Z-contrast will improve the precision of composition measurements since strain- and composition-induced Z-contrast variations can be separated.

半导体晶体中应变场的测量是理解新型GeSi/Si或(Al)GaN/蓝宝石异质结物理过程的前提。这一建议首先讨论了GeSi/Si岛的应变特性，以便对Ge在Si上的生长有一个基本的了解。其次，作为高性能计算机处理器的基本模块，GeSI-MOSFET中的应变场和局域Ge组分将被测量，因为电学性质在很大程度上取决于应变分布。第三，由于GaN/蓝宝石伪衬底的应力降低效率在很大程度上决定了后续InGaN/GaN LED有源层的生长和效率，因此我们将从应变的角度研究GaN/蓝宝石伪衬底的应变。为了可靠地获取这些应变场，开发了一种利用衍射束位置的扫描透射式电子显微镜(STEM)应变测量方法。具体地说，在每个扫描点获得会聚束电子衍射(CBED)图案的同时，在样品上扫描STEM探针。使用专门的算法，可以准确地检测到盘状CBED反射，精度达到7x10-4。为了大大减少实验数据量，这些算法将被实现在用于控制所使用的FEI Titan显微镜的软件中，以便在STEM探针扫描的同时进行原位CBED图形处理。这不仅可以实现2D应变映射，还可以在数据采集后立即提供应变结果。对于以前已经达到的0.5 nm的空间分辨率，充分利用该方法的2D映射能力的一个主要前提是CBED图案采集的急剧加速，这是传统相机不可能实现的。为了研究微米范围内的大范围应变场，将在实验和模拟中开发一种STEM-进动方法。在进动模式下，STEM探头的入射在锥体上旋转，同时所产生的衍射图的偏移被补偿。通过这种方式，可以消除CBED强度的强烈变化。此外，高阶反射的高应变敏感性可以被利用，因为它们看起来更亮。此外，由于后放大透镜引起的衍射图案的失真将被测量并在应变测量中被考虑在内。这对于随后包括剪切在内的全应变张量的测定是很重要的。最后，这项技术将与所谓的Z对比信号相结合，对样品的化学成分和应变敏感。因此，应变和Z衬度的同时测量将提高成分测量的精度，因为应变和成分引起的Z衬度变化可以分开。

项目成果

Mazes and meso-islands: Impact of Ag preadsorption on Ge growth on Si(111)

迷宫和中岛：Ag 预吸附对 Si(111) 上 Ge 生长的影响

• DOI: 10.1103/physrevb.94.235410
• 发表时间: 2016
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: T. Schmidt;M. Speckmann;J. Flege;K. Müller-Caspary;I. Heidmann;A. Kubelka-Lange;T.O. Mentes;M. A. Nino;A. Locatelli;A. Rosenauer;J. Falta
• 通讯作者: J. Falta

Two-dimensional strain mapping in semiconductors by nano-beam electron diffraction employing a delay-line detector

• DOI: 10.1063/1.4927837
• 发表时间: 2015-08-17
• 期刊: APPLIED PHYSICS LETTERS
• 影响因子: 4
• 作者: Mueller-Caspary, Knut;Oelsner, Andreas;Potapov, Pavel
• 通讯作者: Potapov, Pavel