INVESTIGATION OF ELECTRON BEAM ANALYZER FOR OBSERVING THE SPECIMEN IN THE AIR

本课题研究的是利用ESEM中使用的低聚散射电子束对空气中试样进行观测的电子束分析仪。通过理论分析和数字仿真，研究了Be或C箔与空气中的寡聚散射现象。并提出了装置设计时应考虑的条件。首先，从理论上推导了通过Be箔将Oligo散射电子束引入空气的要求。其次，介绍了用于分析寡聚散射现象的仿真程序。该程序基于蒙特卡罗模拟，采用单散射模型，是目前应用范围较广的一种，给出的结果与分析和实验结果相吻合。结果表明，该方法能够计算出电子在be或C箔和空气层（或取代气层）中的行为，并能在一定尺寸范围内使用oligo散射光束，这是通过模拟程序可以实现的。并证实了oligo散射光束通过箔和空气层到达试样表面，产生的反向散射电子可用于本文提出的模型尺寸的图像处理。根据计算，样品表面光斑直径可达几个nm，电子反射率为7%，forE=40keV,L (be) =0.2mum,L (Air) =200mum。

This project is concerned with the development of electron beam analyzer for obsevcing the specimen in the air by using Oligo-scattering electron beam which is using for ESEM.The Oligo-scattering phenomenon in the Be or C foil and air is studied by the theoretical analysis and digital simulation. And the conditions which should be considered in design of the device is reauested.First of all, the requirement to take out Oligo scattering electron beam into air through the Be foil is theoretically derived. Next, the simulation program developed to analyze Oligo-scattering phenomenon is described. This program is based on the Monte Carlo simulation by which the single scattering model is adopted and it is the one with a wide range of application to give the result which is corresponding to analysis and the experimental result well so far.It is shown to be able to calculate the behavior of the electron in the Be or C foil and the air layr (or, substituted gas layr) and to use Oligo-scattering beam within the range of the size which can be achieved by the simulation program. And it is confirmed that Oligo-scattering beam reached the specimen surface by passing the foil and the air layr, and generated back scattering elecrons which can be used for image processing in the model size proposed here. According to the calcuation, several nm spot diameter on the specimen surface could be obtained and the reflection rate of electrons could be 7% forE=40keV,L (Be) =0.2mum and L (Air) =200mum.