Influence of structural variations on high-resolution electron microscopy images of poly[1,6-di(N-carbazolyl)2,4-hexadiyne] nanocrystals
Influence of structural variations on high-resolution electron microscopy images of poly[1,6-di(N-carbazolyl)2,4-hexadiyne] nanocrystals
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结构变化对聚[1,6-二(N-咔唑基)2,4-己二炔]纳米晶高分辨率电子显微镜图像的影响
DOI：
10.1080/01418610010009388
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
David C. Martin
中科院分区：
文献类型：
--
作者：
C. Kübel;David C. Martin
摘要利用高分辨电子显微镜（HREM）研究了聚[1，6-二（N-咔唑基）-2，4-己二炔）（polyDCHD）纳米晶的结构变化。不同晶带中的多个颗粒以高达0.19nm的高空间分辨率成像，产生亚基-晶胞水平的图像信息（a = 1.74nm，B = 1.29nm和c = 0.49nm; β = 108.3°，P21/a; Z = 2）。平均尺寸约为40 nm × 80 nm，主要生长方向沿着聚合物链（001）。大多数HREM图像对应于[100]或[120]区。在少数情况下，它也可以在[001]区与垂直于碳基板的聚合物链轴取向的晶体的图像。通过与基于晶体结构和成像条件的近似的多层HREM图像模拟进行比较来进行图像解释。对polyDCHD进行的这些模拟表明，HREM图像对分子几何形状的微小变化敏感。确定了一个参数来描述这些变化的衍射图案中的强度变化ΔI。Pendellösung图显示，根据成像区域，原子位置的百分之一纳米量级的变化导致强度变化ΔI高达70%，这使我们预期实验图像受到少量无序的强烈影响。在动态电子衍射的无序和预期的变化之间的关系进行了评估，使用各种模型的晶体结构，在不同的温度下通过分子动力学模拟获得。无序对动态衍射和HREM图像的影响变得特别重要，用于分析缺陷或近表面，其中预计会发生畸变。然而，在纳米晶体的表面附近没有观察到晶格间距的显著变化。使用局部快速傅里叶变换比较和傅里叶滤波的图像处理用于获得关于这些polyDCHD纳米晶体中的小角度晶界的几何形状的详细信息，例如具有3°取向差的三重结。
Abstract High-resolution electron microscopy (HREM) was used to obtain information about structural variations in poly[1,6-di(N-carbazolyl)-2,4-hexadiyne) (polyDCHD) nanocrystals. Several particles in different crystallographic zones were imaged with high spatial resolution of up to 0.19nm, resulting in image information on a subunit-cell level (a = 1.74nm, b = 1.29nm and c = 0.49nm; β = 108.3°, P21/a; Z = 2). The average nanocrystal had a nominally rectangular shape and a size of about 40 nm × 80 nm with the major growth direction along the polymer chains (001). Most of the HREM images correspond to the [100] or [120] zone. In a few cases, it was also possible to image crystals oriented in the [001] zone with the polymer chain axis normal to the carbon substrate. Image interpretation was done by comparison with multislice HREM image simulations based on an approximation for the crystal structure and imaging conditions. These simulations performed for polyDCHD indicate that the HREM image is sensitive to small changes in the molecular geometry. A parameter to describe these changes in terms of intensity variations ΔI in the diffraction pattern was determined. Pendellösung plots show that depending on the zone imaged a change in the atomic positions of the order of a hundredth of a nanometre results in intensity variations ΔI of up to 70%, leading us to expect that experimental images are strongly influenced by small amounts of disorder. The relationship between disorder and expected changes in dynamic electron diffraction has been evaluated using a variety of models for the crystal structure obtained by molecular dynamics simulations at different temperatures. The influence of disorder on dynamic diffraction and HREM images becomes especially important for the analysis of defects or near surfaces, where distortions are expected. Nevertheless, no significant change in lattice spacing was observed near the surface of the nanocrystals. Image processing using local fast Fourier transform comparison and Fourier filtering was used to gain detailed information about the geometry of small angle grain boundaries in these polyDCHD nanocrystals, for example a triple junction with a misorientation of 3°.
透射电子显微镜
DOI：
10.1007/978-3-319-26651-0_3
发表时间：
2016
期刊：
--
影响因子：
--
作者：
Burke M
通讯作者：
Burke M