Local structure analysis of disordered materials via contrast variation in scanning transmission electron microscopy
Local structure analysis of disordered materials via contrast variation in scanning transmission electron microscopy
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DOI：
10.1063/5.0104798
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发表时间：
2022-09
期刊：
影响因子：
1.6
通讯作者：
K. Kimoto;M. Shiga;S. Kohara;J. Kikkawa;O. Cretu;Y. Onodera;K. Ishizuka
中科院分区：
文献类型：
--
作者：
K. Kimoto;M. Shiga;S. Kohara;J. Kikkawa;O. Cretu;Y. Onodera;K. Ishizuka
无序材料的晶体结构通常使用衍射技术进行分析，例如 X 射线衍射 (XRD)、中子衍射 (ND) 和电子衍射 (ED)。在这里，我们展示了一种新技术，通过扫描透射电子显微镜（STEM）在对比度变化方案下分析无序材料的局部结构。对比度变化是一种用于分析散装材料的方案，它将两种不同的衍射技术与离散散射因子（例如 ND 和 XRD）相结合。同时利用具有不同原子序数依赖性的环形暗场（ADF）和环形明场（ABF）成像的STEM图像对比度。使用傅里叶变换和自相关运算对非晶态 SiO2 的模拟 STEM 图像进行了检查，结果表明 ADF 和 ABF 图像的傅里叶变换分别与传统 XRD/ED 和 ND 技术的结果一致。 ABF 图像的自相关表明轻元素的短程有序性，这是使用传统 TEM、ED 和 XRD 技术无法实现的。因此，在 STEM 成像中采用对比度变化方案为分析非单原子材料的局部晶体结构铺平了道路。
The crystallographic structures of disordered materials are typically analyzed using diffractometry techniques, such as x-ray diffraction (XRD), neutron diffraction (ND), and electron diffraction (ED). Here, we demonstrate a novel technique to analyze the local structure of disordered materials via scanning transmission electron microscopy (STEM) under a contrast variation scheme. Contrast variation is a scheme used for the analysis of bulk materials, which combines two different diffractometry techniques with discrete scattering factors, such as ND and XRD. The STEM image contrasts of annular dark-field (ADF) and annular bright-field (ABF) imaging, which are characterized by different atomic number dependences, are simultaneously utilized. Simulated STEM images of amorphous SiO2 are examined using Fourier transform and autocorrelation operations, revealing that the Fourier transforms of ADF and ABF images are consistent with the results of conventional XRD/ED and ND techniques, respectively. The autocorrelation of the ABF image indicates the short-range ordering of light elements, which cannot be accomplished using conventional TEM, ED, and XRD techniques. As such, employing the contrast variation scheme in STEM imaging paves the way for analyzing the local crystallographic structure of non-monoatomic materials.