光子计数技术用于SEM二次电子信号检测的理论探讨

本重点在分析比较PMT视频放大系统与PMT光子计数系统的噪声源，信噪比及探测灵敏度的基础上，就光子计数技术在扫描电镜（Scanning Electron Microscope，简称SEM）二次电子信号检测中的可能应用进行了初步的理论探讨。分析表明，SEM采用光子计数技术后，信号探测灵敏度可提高一个量级以上，从而在相同的电子枪发射亮度与既定的电子光学系统下，可获得更高的图象分辨率与清晰度。

THEORETICAL DISCUSSION ON THE PHOTON COUNTING TECHNIQUE USED FOR TESTING SEM SECONDARY ELECTRON SIGNAL

This paper analyses the noise source, signal-to-noise ratio and detectaive sensitivity of PMT video amplifing system and PMT photon counting system. The possible application of the photon technique in testing SEM seconding electron signal has been proposed and discussed for the first time. The analysis show that when SEM make use of photon counting technique, the detective sensitivity of testing secondary electrom signal may be raised about ten times, therefore more high distinctness and resolution of SEM secondary electron image may be obtained.