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扫描电子显微镜中巧用低角电子成像

Tactful Use of Low Angle Electrons in Scanning Electron Microscope

  • 摘要: 利用扫描电子显微镜对不导电样品的成像过程中,荷电效应会导致图像产生畸变、漂移、亮点亮线等缺陷。二次电子成像形貌立体感较好但是容易产生荷电现象,背散射电子成像受荷电影响较小但是一般形貌衬度较差。文章借助Apreo 2S场发射扫描电镜,针对不导电样品在不镀膜的情况下,通过优化工作模式、探测器和工作距离等参数来调控电子信号,巧用低角电子,得到形貌衬度明显的高分辨图像。从二次电子角度出发,使用Optipan模式配合T2探测器通过缩短工作距离以收集低角二次电子从而减弱荷电效应。从背散射电子角度出发,放大倍数较低时可使用Optipan模式配合ETD探测器获得形貌立体感好的高分辨图像,放大倍数高时可使用Immersion模式配合T1探测器缩短工作距离下以得到最佳图像。

     

    Abstract: The charge effect is one of the important reasons for the unexpected scanning electron microscope (SEM) images, such as distortion, drift, bright spots and bright lines. Secondary electrons imaging is beneficial for the topographical contrast, but easily affected by charge effect, while backscattered electrons imaging behaves better to avoid charge effect with shortcoming of mainly presenting material contrast. In this paper, Apreo 2S is used to explore the optimal combinations of the use cases, detectors and work distance to regulate the detected electrons. Considering about the secondary electrons, Optiplan use case combined with T2 detector is applied and the work distance is decreased to collect low angle secondary electrons, thus leading to weakened charge effect. From the point of backscattered electrons, at low magnification, Optiplan use case combined with ETD detector can be used to obtain high-resolution images with good topographic contrast. At high magnification the best quality image is acquired under Immersion use case combined with T1 detector at short work distance.

     

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