Phase-Shifting Electron Holography for Accurate Measurement of Potential Distributions in Organic and Inorganic Semiconductors
Phase-Shifting Electron Holography for Accurate Measurement of Potential Distributions in Organic and Inorganic Semiconductors
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用于精确测量有机和无机半导体电势分布的相移电子全息术
DOI：
10.1093/jmicro/dfaa061
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发表时间：
2021
期刊：
影响因子：
1.8
通讯作者：
Tsukasa Hirayama
中科院分区：
文献类型：
--
作者：
Kazuo Yamamoto; Satoshi Anada; Takeshi Sato; Noriyuki Yoshimoto; Tsukasa Hirayama
相移电子全息术（PS-EH）是一种干涉透射电子显微镜技术，可以准确地显示功能材料（如半导体）中的电位分布。本文简要介绍了PS-EH的特点，克服了传统基于傅里叶变换的EH所面临的一些问题。在此基础上，提出了高精度多电子双棱镜PS-EH技术和低温聚焦离子束样品制备技术，这两种技术是半导体精确相位测量的重要技术。我们介绍了几种PS-EH的应用，以展示其在有机和无机半导体中的潜力，然后通过比较它们与以前关于传统EH的报道来讨论它们的差异。我们发现，在偏置条件下，PS-EH不仅可以观察到GaAs p-n结的电势分布，还可以观察到电场和电荷密度，并阐明了局域带结构、耗尽层宽度和空间电荷如何随偏置条件而变化。此外，PS-EH清晰地显示了不同Al成分的AlGaN/GaN界面形成的二维电子气相层的局部电位分布。我们还报告了PS-EH在有机电致发光多层材料中的应用结果，并指出了层间的重大潜在变化。与传统的EH相比，PS-EH可以实现更精确的相位测量，本文介绍的研究结果将有助于高性能半导体材料和器件的未来研究和开发。
Phase-shifting electron holography (PS-EH) is an interference transmission electron microscopy technique that accurately visualizes potential distributions in functional materials, such as semiconductors. In this paper, we briefly introduce the features of the PS-EH that overcome some of the issues facing the conventional EH based on Fourier transformation. Then, we present a high-precision PS-EH technique with multiple electron biprisms and a sample preparation technique using a cryo-focused-ion-beam, which are important techniques for the accurate phase measurement of semiconductors. We present several applications of PS-EH to demonstrate the potential in organic and inorganic semiconductors and then discuss the differences by comparing them with previous reports on the conventional EH. We show thatin situbiasing PS-EH was able to observe not only electric potential distribution but also electric field and charge density at a GaAs p–n junction and clarify how local band structures, depletion layer widths and space charges changed depending on the biasing conditions. Moreover, the PS-EH clearly visualized the local potential distributions of two-dimensional electron gas layers formed at AlGaN/GaN interfaces with different Al compositions. We also report the results of our PS-EH application for organic electroluminescence multilayers and point out the significant potential changes in the layers. The proposed PS-EH enables more precise phase measurement compared to the conventional EH, and our findings introduced in this paper will contribute to the future research and development of high-performance semiconductor materials and devices.