Effects of small specimen tilt and probe convergence angle on ADF-STEM image contrast of Si0.8Ge0.2 epitaxial strained layers on (100) Si

被引：7

作者：

Wu, X. ^{[1
]}

Robertson, M. D. ^{[2
]}

Kawasaki, M. ^{[3
]}

Baribeau, J-M ^{[1
]}

机构：

[1] Natl Res Council Canada, Inst Microstruct Sci, Ottawa, ON K1A 0R6, Canada

[2] Acadia Univ, Dept Phys, Wolfville, NS B4P 2R6, Canada

[3] JEOL USA, Peabody, MA 01960 USA

来源：

ULTRAMICROSCOPY | 2012年 / 114卷

基金：

加拿大自然科学与工程研究理事会;

关键词：

Annular dark field scanning transmission electron microscopy; Semiconductor heteroepitaxial strained layers; RELAXATION; GROWTH; FILMS;

D O I：

10.1016/j.ultramic.2012.01.001

中图分类号：

TH742 [显微镜];

学科分类号：

摘要：

The effects of specimen tilt and probe convergence angle on annular dark field (ADF) image contrast of Si0.8Ge0.2 heteroepitaxial strained layers on (100) Si were investigated in a 200 kV scanning transmission electron microscope (STEM) for a TEM specimen thickness of 195 nm. With 0.5 degrees of specimen tilt away from the exact < 011 > zone-axis orientation, the signal-to-noise level of atomic columns was significantly reduced for both Si0.8Ge0.2 and Si in high resolution ADF-STEM lattice images. When the specimen was tilted 0.5 degrees around the < 011 > axis, or the STEM probe convergence semiangle was reduced from 14.3 to 3.6 mrad, the ADF-STEM image intensity profiles across the Si0.8Ge0.2 and Si layers changed significantly as compared to those obtained at the exact < 011 > zone axis orientation, and no longer reflected the composition changes occurring across the layer structure. Multislice image simulation results revealed that the misfit strain between the Si0.8Ge0.2 and Si layers, and strain relaxation near the surface of the TEM specimen, were responsible for the observed changes in image intensity. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.

引用

页码：46 / 55

页数：10