Key Laboratory for Physical Electronics and Devices of the Ministry of Education, Department of Electronic Science and Technology, Xi'an Jiaotong University, Xi'an 710049, People's Republic of China.
Micron. 2010 Jul;41(5):490-7. doi: 10.1016/j.micron.2010.01.010. Epub 2010 Feb 11.
Image quality of MeV transmission electrons is an important factor for both observation and electron tomography of microns-thick specimens with the high voltage electron microscope (HVEM) and the ultra-HVEM. In this work, we have investigated image quality of a tilted thick specimen by experiment and analysis. In a 3 MV ultra-HVEM, we obtained transmission electron images in amplitude contrast of 100 nm gold particles on the top surface of a tilted 5 microm thick amorphous epoxy-resin film. From line profiles of the images, we then measured and evaluated image blurring, contrast, and the signal-to-noise ratio (SNR) under different effective thicknesses of the tilted specimen and accelerating voltages of electrons. The variation of imaging blurring was consistent with the analysis based on multiple elastic scattering. When the effective thickness almost tripled, image blurring increased from approximately 3 to approximately 20 nm at the accelerating voltage of 3 MV. For the increase of accelerating voltage from 1 to 3 MV in the condition of the 14.6 microm effective thickness, due to the reduction of multiple scattering effects, image blurring decreased from approximately 54 to approximately 20 nm, and image contrast and SNR were both obviously enhanced by a factor of approximately 3 to preferable values. The specimen thickness was shown to influence image quality more than the accelerating voltage. Moreover, improvement on image quality of thick specimens due to increasing the accelerating voltage would become less when it was further increased from 2 to 3 MV in this work.
兆电子伏特透射电子的像质是高压电子显微镜（HVEM）和超高压电子显微镜进行微米厚样品观察和电子断层扫描的一个重要因素。在这项工作中，我们通过实验和分析研究了倾斜厚样品的像质。在一台 3 兆电子伏特的超高压电子显微镜中，我们获得了位于倾斜的 5 微米厚非晶态环氧树脂薄膜顶表面的 100nm 金颗粒的振幅衬度透射电子像。通过对像的线轮廓的分析，我们测量和评估了在不同倾斜样品有效厚度和电子加速电压下的像模糊、对比度和信噪比（SNR）。成像模糊的变化与基于多次弹性散射的分析一致。当有效厚度几乎增加三倍时，在 3 兆电子伏特的加速电压下，像模糊从大约 3nm 增加到大约 20nm。在有效厚度为 14.6 微米、加速电压从 1 兆电子伏特增加到 3 兆电子伏特的情况下，由于多次散射效应的减少，像模糊从大约 54nm 降低到大约 20nm，图像对比度和 SNR 都明显增强了大约 3 倍，达到了较好的值。结果表明，与加速电压相比，样品厚度对像质的影响更大。此外，在本工作中，当加速电压从 2 兆电子伏特进一步增加到 3 兆电子伏特时，由于进一步增加加速电压，厚样品的像质改善会变得不那么明显。
