Specimen charging on thin films with one conducting layer: Discussion of physical principles
Specimen charging on thin films with one conducting layer: Discussion of physical principles
复制标题
DOI：
10.1017/s1431927604040668
复制
发表时间：
2004-12-01
影响因子：
2.8
通讯作者：
Downing, KH
中科院分区：
文献类型：
--
作者：
Glaeser, RM;Downing, KH
虽然在透射电子显微镜中最常见的样品充电的后果可以通过在绝缘样品上蒸发薄导电膜（如碳膜）或直接在这样的导电膜上制备样品来消除，但仍然存在更微妙的充电效应。我们认为，在这种情况下，试样充电可能会产生一个偶极子片，而不是一层正电荷在试样的表面。一个简单的模型的因素，控制试样充电的动力学，和它的中和，进行了讨论，试图尽量减少试样充电量的实验作为指导。可信的静电力和电子光学干扰，可能会发生的估计表明，试样弯曲和翘曲可能有最大的影响，在高分辨率的图像质量下降。电子光学效应很可能是可以忽略不计的，除非在样品是倾斜到高角度的情况下。提出了一个模型来解释如何形成一个偶极层的机械和电子光学效应将有更大的影响，在垂直于倾斜轴的方向上的图像分辨率，一个众所周知的效果，在电子显微镜的二维晶体。
Although the most familiar consequences of specimen charging in transmission electron microscopy can be eliminated by evaporating a thin conducting film (such as a carbon film) onto an insulating specimen or by preparing samples directly on such a conducting film to begin with, a more subtle charging effect still remains. We argue here that specimen charging is in this case likely to produce a dipole sheet rather than a layer of positive charge at the surface of the specimen. A simple model of the factors that control the kinetics of specimen charging, and its neutralization, is discussed as a guide for experiments that attempt to minimize the amount of specimen charging. Believable estimates of the electrostatic forces and the electron optical disturbances that are likely to occur suggest that specimen bending and warping may have the biggest impact on degrading the image quality at high resolution. Electron optical effects are likely to be negligible except in the case of a specimen that is tilted to high angle. A model is proposed to explain how both the mechanical and electron-optical effects of forming a dipole layer would have much greater impact on the image resolution in a direction perpendicular to the tilt axis, a well-known effect in electron microscopy of two-dimensional crystals.