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本文在前人工作的基础上。总结了在普遍透射电镜上实现会聚束电子衍射的几种方法,介绍了在JEM—100CX(Ⅱ)上操作的具体步聚,比较了各种方法的优缺点,并对有关理论和技术问题作了讨论。实现会聚束电子衍射(CBED)首要的条件是得到适当大的会聚角的电子束,并调节其会聚角的大小。在普通电镜上单用改变聚光镜电流及其光阑尺寸的方法无法做到这一点,必须利用强激励的物镜前场作为“第三聚光镜”来进一步会聚电子束,实行的方法有三种。一种是大幅度地增加物镜电流使象过焦,在成象模式直接得到CBED花样,称成象模式法。一种是较大幅度地降低试样高度,大大加强物镜前场部分,相对地减弱物镜的后场部分,并在衍射模式下得到CBED花样,称衍射模式降低试样高度法。照片就是用这种方法得到的不锈钢<111 带轴的CBED花样。第三种则是利用扫描附件工作时高度激励的物镜磁场会聚电子束,在微微衍射模式下得到
This article is based on the previous work. Several methods to achieve convergent beam electron diffraction (EDF) on universal TEM are summarized. Concrete steps and steps of JEM-100CX (Ⅱ) are introduced. The advantages and disadvantages of each method are compared. The theoretical and technical issues are also discussed Discuss. The primary condition to achieve convergent beam electron diffraction (CBED) is to get a suitably large converging angle of the electron beam and to adjust the size of its convergence angle. In conventional electron microscope alone to change the condenser current and aperture size of the method can not do this, we must use the strong excitation of the objective front field as a “third condenser” to further converging the electron beam, there are three ways to implement. One is to substantially increase the lens current so as to focus, CBED patterns directly in the imaging mode, said imaging mode method. One is to greatly reduce the sample height, greatly enhance the front part of the objective lens, relatively weakening the back field of the objective part, and in the diffraction mode CBED patterns obtained, said the diffraction mode to reduce the sample height method. The photograph is a stainless steel <111 cot CBED pattern obtained in this way. The third is the use of scanning attachment work highly motivated by the objective lens magnetic field convergence electron beam obtained in the pico-diffraction mode