Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ, UK.
J Microsc. 2010 Feb;237(2):148-54. doi: 10.1111/j.1365-2818.2009.03318.x.
We present an evaluation of electron tomography of buried InAs quantum dots using dark field 002 imaging conditions. The compositional sensitivity of this imaging condition gives strong contrast among III-V materials of differing compositions and, in principle, should allow an accurate 3D model of the buried structures to be produced. The large extinction distance allows specimens several hundred nanometres in thickness to be examined and reduces the effect of strain contrast in the images, with the advantage that it can be performed using conventional transmission electron microscopy techniques. A two-beam condition must be maintained for all images, and the presence of other strong diffraction effects at certain specimen orientation results reduces the number of orientations available for tomography by approximately 10%. The data presented here are limited due to a lack of angular range in the data set but we find that an acceptable 3D model of a buried quantum dot may be produced by imposing cylindrical symmetry on the data set.
我们提出了一种使用暗场 002 成像条件对埋入式 InAs 量子点进行电子断层扫描的评估。这种成像条件的组成灵敏度在不同组成的 III-V 材料之间提供了强烈的对比，并且原则上应该允许生成埋入式结构的精确 3D 模型。大的消光距离允许检查几百纳米厚的样品，并减少了图像中的应变对比度的影响，其优点是可以使用传统的透射电子显微镜技术进行。对于所有图像都必须保持双束条件，并且在某些样品取向存在其他强衍射效应会将可用于断层扫描的取向数量减少约 10%。由于数据集缺乏角度范围，这里呈现的数据受到限制，但我们发现通过对数据集施加圆柱对称性，可以生成可接受的埋入式量子点 3D 模型。
