Dynamical effects in strain measurements by dark-field electron holography
Dynamical effects in strain measurements by dark-field electron holography
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DOI：
10.1016/j.ultramic.2014.06.005
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发表时间：
2014-12-01
期刊：
影响因子：
2.2
通讯作者：
Hytch, M. J.
中科院分区：
文献类型：
--
作者：
Javon, E.;Lubk, A.;Hytch, M. J.
在这里，我们研究了动态散射对投影几何相位和应变图重建使用暗场电子全息（DFEH）的非均匀应变晶体的效果。所研究的结构由生长在（001）-Si衬底上的{SiGe/Si}超晶格组成。用有限元法模拟了TEM薄片内的三维应变。所观察到的投影应变模拟在两种方式，通过乘以在晶体中的每个深度的应变由最近开发的分析双光束动力学理论确定的加权函数，并通过简单地取平均值。我们表明，实验结果需要理解的动力学理论和良好的协议之间的实验和模拟结果。在某些情况下，离散性仍然存在，可能是由于实际双光束衍射条件的不精确性，特别是偏差参数，并指出了双光束近似的局限性。最后，提出了一种应变场三维重建的方法。(C)2014爱思唯尔有限公司版权所有。
Here, we study the effect of dynamic scattering on the projected geometric phase and strain maps reconstructed using dark-field electron holography (DFEH) for non-uniformly strained crystals. The investigated structure consists of a {SiGe/Si} superlattice grown on a (001)-Si substrate. The three dimensional strain held within the thin TEM lamella is modelled by the finite element method. The observed projected strain is simulated in two ways by multiplying the strain at each depth in the crystal by a weighting function determined from a recently developed analytical two-beam dynamical theory, and by simply taking the average value. We demonstrate that the experimental results need to be understood in terms of the dynamical theory and good agreement is found between the experimental and simulated results. Discrepancies do remain for certain cases and are likely to be from an imprecision in the actual two-beam diffraction conditions, notably the deviation parameter, and points to limitations in the 2-beam approximation. Finally, a route towards a 3D reconstruction of strain fields is proposed. (C) 2014 Elsevier B.V. All rights reserved.