从ADF-STEM中的位错观察图像对比度
Insights into image contrast from dislocations in ADF-STEM
摘要：
在环形暗场扫描透射电子显微镜ADF STEM中，竞争机制有助于位错的图像对比度。因此，对ADF STEM对比度的机制的明确理论理解对于正确解释位错图像至关重要。本文报道了一个系统的研究ADF干对比度从GaN样品中的位错，实验和计算。系统的实验ADF STEM图像的边缘字符位错揭示了一些特性的对比度功能，显示依赖于角度检测范围和特定位置的位错在样品中。基于电子沟道和布洛赫波散射理论，结合Grillo应变沟道方程的多层模拟，提出了一个理论模型，用以解释这种复杂对比度现象的物理起源。
英文摘要：
Competitive mechanisms contribute to image contrast from dislocations in annular dark field scanning transmission electron microscopy ADF STEM. A clear theoretical understanding of the mechanisms underlying the ADF STEM contrast is therefore essential for correct interpretation of dislocation images. This paper reports on a systematic study of the ADF STEM contrast from dislocations in a GaN specimen, both experimentally and computationally. Systematic experimental ADF STEM images of the edge character dislocations revealed a number of characteristic contrast features that are shown to depend on both the angular detection range and specific position of the dislocation in the sample. A theoretical model based on electron channelling and Bloch wave scattering theories, supported by multislice simulations using Grillo s strain channelling equation, is proposed to elucidate the physical origin of such complex contrast phenomena.
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