Oshima Yoshifumi, Nishi Ryuji, Asayama Kyoichiro, Arakawa Kazuto, Yoshida Kiyokazu, Sakata Takao, Taguchi Eiji, Yasuda Hidehiro
Research Center for Ultra-High Voltage Electron Microscopy, Osaka University, 7-1 Mihoga-oka, Ibaraki, Osaka 567-0047, Japan.
Microscopy (Oxf). 2013;62(5):521-31. doi: 10.1093/jmicro/dft031. Epub 2013 May 14.
We quantitatively analyzed the contrast degradation and blur of 20-nm gold nanoparticles adsorbed on the top of amorphous silicon films of thicknesses of 0.54, 1.09, 1.63 and 2.2 μm in bright-field transmission electron microscope (TEM) images taken at accelerating voltages of 0.5, 1, 2 and 3 MeV. The thickness dependence of the transmission was well explained and consistent with our calculations. The blur function, derived by assuming that the TEM image of a thick specimen can be reproduced by convolving the TEM image of a very thin specimen with it, was found to be expressed by a two-dimensional Lorentzian function. Considering the two characteristics of the Lorentzian function, a sharp peak around the center and a long tail, we concluded that, for TEM observations of thick specimens, the image contrast is degraded predominantly by inelastic scattering and the image is blurred predominantly by multiple elastic scattering.
我们在加速电压为0.5、1、2和3兆电子伏特下拍摄的明场透射电子显微镜（TEM）图像中，对吸附在厚度为0.54、1.09、1.63和2.2微米的非晶硅膜顶部的20纳米金纳米颗粒的对比度降解和模糊进行了定量分析。透射率的厚度依赖性得到了很好的解释，并且与我们的计算结果一致。通过假设厚样品的TEM图像可以通过将非常薄的样品的TEM图像与之卷积来再现而得出的模糊函数，被发现可以用二维洛伦兹函数表示。考虑到洛伦兹函数的两个特征，即中心附近的尖锐峰值和长长的尾部，我们得出结论，对于厚样品的TEM观察，图像对比度主要因非弹性散射而降低，图像主要因多次弹性散射而模糊。
