探针电流对场发射扫描电镜图像的影响

Impact of Probe Current on FESEM Images

通过对电镜工作原理的研究,分析了不同探针电流对电镜图像分辨率、景深、荷电现象的影响因素,总结了选择最佳探针电流的原则。探针电流升高,束斑直径变大,信噪比变好,但图像分辨率下降,景深减小,荷电现象增强;探针电流降低,束斑直径减小,分辨率增高,景深增加,有利于减弱荷电现象,但是探针电流过小,噪声增大,聚焦困难,图像分辨率反而下降。实验表明,结合样品的特征,灵活地选择探针电流能显著地提高电镜图像质量。

By studying the working principles of FESEM,the impacts of probe current on the resolution,image depth and charge phenomenon are analyzed.Based on this,the strategies of setting the optimum probe current are established.When probe current increases,the beam spot grows larger and the signal/noise ratio turns better.However,this will lead to reduceing image resolution and depth and increase charge phenomenon.When probe current dwindles,the beam spot becomes small.The image resolution will be improved,the image depth will increase and the charge phenomenon decrease.When the probe current is too small,the noise will increase to an unacceptable extent and thus focusing becomes difficult.Consequently,the image resolution becomes unsatisfactory.According to the characteristics of the sample,the probe current should be strategically chosen to ensure the quality of FESEM image.