Toyama Satoko, Seki Takehito, Kanitani Yuya, Kudo Yoshihiro, Tomiya Shigetaka, Ikuhara Yuichi, Shibata Naoya
Institute of Engineering Innovation, School of Engineering, University of Tokyo, 2-11-16, Yayoi, Bunkyo, Tokyo 113-0032, Japan.
Institute of Engineering Innovation, School of Engineering, University of Tokyo, 2-11-16, Yayoi, Bunkyo, Tokyo 113-0032, Japan; PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan.
Ultramicroscopy. 2022 Aug;238:113538. doi: 10.1016/j.ultramic.2022.113538. Epub 2022 Apr 28.
Differential phase contrast (DPC) in scanning transmission electron microscopy can be used to visualize electric field distributions within specimens in real space. However, for electric field mapping in crystalline specimens, the concomitant diffraction contrast is seriously problematic. In particular, for heterostructures with large lattice distortions, such as GaN-based semiconductor devices, the diffraction contrast cannot be reduced using conventional methods such as DPC image acquisition under off-axis conditions. In the present study, the electric field imaging of heterostructures is shown to suppress the diffraction contrast by averaging multiple DPC signals, obtained under various beam-tilt conditions near the zone axis. The remaining diffraction contrast was quantitatively estimated through simulations. This technique was demonstrated to enable the quantitative evaluation of electric field distributions across GaN/AlGaN multi-heterostructures, with errors possibly attributed to the residual diffraction contrast.
扫描透射电子显微镜中的差分相衬（DPC）可用于在实空间中可视化样品内的电场分布。然而，对于晶体样品中的电场映射，伴随的衍射衬度是一个严重的问题。特别是对于具有大晶格畸变的异质结构，如基于GaN的半导体器件，使用离轴条件下的DPC图像采集等传统方法无法降低衍射衬度。在本研究中，通过对在区域轴附近的各种束倾斜条件下获得的多个DPC信号进行平均，异质结构的电场成像显示出能够抑制衍射衬度。通过模拟对剩余的衍射衬度进行了定量估计。该技术被证明能够对GaN/AlGaN多异质结构上的电场分布进行定量评估，误差可能归因于残余衍射衬度。
