Discrimination between Coherent and Incoherent Interfaces using STEM Moire
Discrimination between Coherent and Incoherent Interfaces using STEM Moire
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使用 STEM 莫尔条纹区分相干和非相干界面
DOI：
10.1017/s1431927621008369
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发表时间：
2021
影响因子：
2.8
通讯作者：
Keisuke Arimoto
中科院分区：
文献类型：
--
作者：
Junji Yamanaka;Daisuke Izumi;Chiaya Yamamoto;Mai Shirakura;Kosuke Hara; Keisuke Arimoto
STEM莫尔莫尔是指STEM扫描线与晶格之间的莫尔莫尔，近年来研究进展迅速[1-4]。特别是对于分析半导体材料中的晶格应变，它被认为是非常有用的。然而，大多数关于STEM过程的研究都是基于高度指定的TEM，例如cs校正机。我们的团队一直专注于在不使用高度指定的机器的情况下使用STEM模型，因为我们认为这可能有助于材料科学领域的许多研究人员[5-7]。在这项研究中，我们展示了半导体的相干和非相干异质界面的实验结果，并展示了与这些样品相对应的STEM moir<s:1>模拟图像。利用MBE在Si（110）衬底上生长了A Si层和复合阶梯梯度SiGe层。我们也用MBE法制备了Ge/Si（100）。然后在样品上沉积非晶碳、Pt-Pd和钨作为FIB工艺的保护层。然后，在40和10 kV的加速电压下，用FIB将试样制作成箔片进行STEM观测。采用场发射型STEM (FEI Tecnai Osiris)，没有任何Cs校正器，加速电压为200 kV。观察了样品的{111}面与附带电子扫描线之间的STEM变化。扫描线的标称周期设置为311和632 pm，因为周期必须接近目标晶体平面的d-间距的简单整数。(dSi （111)= 314 pm, dGe (111)= 327 pm）通过以下方式获得模拟的STEM moir<s:1>图像：(1)确定样品的单元格，(2)获得单元格在{110}平面上的投影，(3)绘制出附加电子束的二维点阵点，如2048 × 2048或1024 × 1024，(4)将上述两幅图放在一起，(5)在原子位置与电子束位置接近时显示亮点。当它们不接近时（在HAADF的情况下）显示暗点。对于STEM亮场图像的模拟，可以使用反向图像。这是一个简单的模拟，但对解释实验中所采取的STEM过程非常有用。
Studies about STEM moiré, which is a moiré between scanning lines of STEM and crystal lattice, are progressing recently [1-4]. Especially it is considered to be very useful to analyze lattice strains in semiconductor materials. However, most of the studies about STEM moiré are based on highly specified TEM, such as Cs-corrected machines. Our group has been focusing on the usage of STEM moiré without using highly specified machines, because we think that may contribute to many researchers in the field of materials sciences [5-7]. In this study, we show experimental results about both coherent and incoherent heterointerfaces of semiconductors, and demonstrate a simulated images of STEM moiré corresponding to those specimens.A Si and compositionally step-graded SiGe layers were grown onto Si (110) substrate using MBE. We also prepare Ge/Si (100) using MBE. Then we deposited amorphous-carbon, Pt-Pd and tungsten onto the specimens as protection layers for the FIB process. After that, the specimens were fabricated into the foil for the STEM observation using FIB with the acceleration voltage of 40 and 10 kV. A field-emission type STEM (FEI Tecnai Osiris) without any Cs correctors was utilized with an acceleration voltage of 200 kV. STEM moiré between the specimens’{111} planes and the incidental-electron scanning lines were observed. The nominal period of the scanning lines was set to 311 and 632 pm because the period must have been close to a simple integer of the d-spacing of the target crystal planes.(dSi (111)= 314 pm, dGe (111)= 327 pm) Simulated STEM moiré images were derived from the following way:(1) Decide the unit-cell of the specimen,(2) obtain the projection of the unit-cell to the {110} plane,(3) draw 2D lattice points of the incidental electron beam such as 2048 by 2048 or 1024 by 1024,(4) put together the above-mentioned two figures,(5) show bright point when the position of atom and that of the electron beam are close, show dark point when those were not close (in the cases of HAADF). For the simulation of the STEM bright field images, reverse images can be used. This is a simple simulation but very useful to interpret the STEM moiré which was taken experimentally.