...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Ultramicroscopy >Quantitative analysis of image contrast in phase contrast STEM for low dose imaging
【24h】

Quantitative analysis of image contrast in phase contrast STEM for low dose imaging

机译：低剂量成像相衬STEM中图像对比度的定量分析

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

This work quantitatively evaluates the contrast in phase contrast images of thin vermiculite crystals recorded by TEM and aberration-corrected bright-field STEM. Specimen movement induced by electron irradiation remains a major problem limiting the phase contrast in TEM images of radiation-sensitive specimens. While spot scanning improves the contrast, it does not eliminate the problem. One possibility is to utilise aberration-corrected scanning transmission electron microscopy (STEM) with an A ngstrom-sized probe to illuminate the sample, and thus further reduce irradiation-induced specimen movement. Vermiculite is relatively radiation insensitive in TEM to electron fluences below 100,000 e/A~2 and this is likely to be similar for STEM although different damage mechanisms could occur. We compare the performance of a TEM with a thermally assisted field emission electron gun (FEG) and charge coupled device (CCD) image capture to the performance of STEMs with spherical aberration correction, cold field emission electron sources and photomultiplier tube image capture at a range of electron fluences and similar illumination areas. We show that the absolute contrast of the phase contrast images obtained by aberration-corrected STEM is better than that obtained by TEM. Although the STEM contrast is higher, the efficiency of collection of electrons in bright field STEM is still much less than that in bright field TEM (where for thin samples virtually all the electrons contribute to the image), and the SNR of equivalent STEM images is three times lower. This is better than expected, probably due to the absence of a frequency dependent modulation transfer function in the STEM detection system. With optimisation of the STEM bright field collection angles, the efficiency may approach that of bright field TEM, and if reductions in beam-induced specimen movement are found, STEM could surpass the overall performance of TEM.
机译：这项工作定量评估了通过TEM和像差校正的明场STEM记录的thin石晶体的相衬图像中的对比度。电子辐照引起的标本运动仍然是限制辐射敏感标本的TEM图像中相衬的主要问题。尽管点扫描可以改善对比度，但不能消除问题。一种可能性是利用具有埃大小的探针的像差校正扫描透射电子显微镜（STEM）照射样品，从而进一步减少辐照引起的样品移动。石在TEM中对100,000 e / A〜2以下的电子注量相对辐射不敏感，这可能与STEM类似，尽管可能发生不同的破坏机理。我们将具有热辅助场发射电子枪（FEG）和电荷耦合器件（CCD）图像捕获的TEM的性能与具有球差校正，冷场发射电子源和光电倍增管图像捕获的STEM的性能进行了比较电子注量和类似的照明区域。我们显示，通过像差校正的STEM获得的相衬图像的绝对对比度要比通过TEM获得的相衬图像的绝对对比度更好。尽管STEM对比度更高，但在明场STEM中电子的收集效率仍然远低于明场TEM中的电子收集效率（对于薄样本，几乎所有电子都对图像有所贡献），等效STEM图像的SNR为低三倍。这好于预期，这可能是由于STEM检测系统中没有频率相关的调制传递函数。通过优化STEM明场采集角度，效率可能接近明场TEM，并且如果发现光束感应的标本移动减少，STEM可能会超过TEM的整体性能。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号