Recently, Field Emission Scanning Electron Microscopy (FE-SEM) has been strongly needed in the fields of nano-technology to observe super-fine structure on the sample with ultra high resolution (UHR). In addition, low voltage (30kV) Scanning Transmission Electron Microscopy (STEM) in FE-SEM has been used for inspection and analysis of the nano-scale sample with high contrast image. In order to realize the UHR-STEM observation in FE-SEM, it is essential to have high performance objective lens, high vibration resistance, and contamination free evacuation system. Hitachi S-5500 is an in-lens type UHR FE-SEM with these conditions and provided the new STEM function which can obtain the bright field (BF) and the dark field (DF) images simultaneously. Performance of the objective lens in FE-SEM is a very important factor to obtain the clear STEM images. We have estimated the spatial resolution of the S-5500 optical system by calculation the optical transfer function (OTF). As a result, it is shown that there is an information value at 0.3nm order in the OTF. We have also obtained the carbon nanotube (CNT) BF-STEM image and it is recognized 0.34nm carbon lattice fringes. On the other hand, DF-STEM can obtain the Z-contrast image. DF-STEM detection system in S-5500 can control the detection angle of the scattered electrons in the sample using motorized detector which can be moved up and down along the optical axis. Therefore, the optimum DF signal corresponded to composition or thickness of the sample, can be obtained by detecting signal scattered wide angle and adjusting detection angle continuously. We have obtained the DF-STEM images of the CNT included iron (Fe) as growth catalyst. When the detection angle is set to 200~400 mrad range, iron part of the image is clearly shown with optimized contrast. In this case, image contrast corresponds to composition (material) information.

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1. Structural Characterization of Carbon Nanofibers using Scanning Electron Microscopy