摘要
透射电镜三维重构成像可以在三维空间上分析样品内部纳米颗粒、界面等微观组织的结构或成分,已成为材料表征中的重要研究方法。目前的三维重构成像方法要求所收集图像的强度与样品性质的积分呈线性关系,即投影近似。本文利用实验以及图像模拟研究了不同成像参数对环形暗场倾转系列像三维重构的影响。实验发现,当环形探测器的内角越大时,收集到的图像信号强度随样品厚度的变化将更加接近线性关系,因此更满足三维重构的投影近似原理,重构结果的误差越小。另外,图像模拟表明,当环形探测器内角足够大时,会聚角的大小不影响投影近似条件,即使用不同大小的会聚角记录环形暗场图像时,其信号强度随样品厚度的关系仍然是接近线性的。提高会聚角的尺寸可以减弱环形暗场图像信号在样品处于较低指数晶带轴时产生的电子通道效应。球差、欠焦量等的变化对投影近似条件以及通道效应的影响很小,但对二维图像分辨率的影响很大,因此影响三维重构的分辨率。
Three-dimensional electron tomography in transmission electron microscpe has been widely used due to its specific advantages in determing morphology or composition of nano particles or interfaces in materials.Current algorithms based on radon transform suppose that the acquired signal should be linear with the sample property projection,termed as projection approximation.In the present study,the influence of parameters of annular dark field scanning transmission electron microscope imaging on the accuracy of electron tomography has been investigated using both experiment and theoretical simulation.It is found experimentally that bigger inner angle of the annular detector improves the linearity of the signal and the accuracy of the reconstruction.Convergent angle has little influence on the linearity of the annular dark field signal as long as the inner angle is big enough.Whereas,the channeling effect can be decreased by using larger convergent angle.It is also found that even though the Cs and defocus heavily influence the resolution of images and reconstruction,they have little influence on both the projection approximation and channelling effect.
作者
明文全
陈江华
沈若涵
何玉涛
陈志逵
MING Wen-quan;CHEN Jiang-hua;SHEN Ruo-han;HE Yu-tao;CHEN Zhi-kui(Center for High-Resolution Electron Microscopy,College of Materials Science and Engineering,Hunan University,Changsha Hunan 410082,China)
出处
《电子显微学报》
CAS
CSCD
北大核心
2019年第5期502-511,共10页
Journal of Chinese Electron Microscopy Society
基金
国家重大科研仪器研制项目(No.11427806)
国家自然科学基金重点资助项目(No.51831004)
关键词
三维重构
图像模拟
投影近似
环形暗场像
通道效应
three-dimensional electron tomography
image simulation
projection approximation
ADF STEM
channeling effect
