Development of Super Resolution Phase Electron Microscopy

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In a high-resolution transmission electron microscope, the influence of a spherical aberration which intrinsically remains in the conventional magnetic lenses disturbs the interpretation for the atomic structure directly from the observed images. Defocus image modulation processing (DIMP) is one of the most promising approaches for observing spherical aberration-free phase and amplitude images with a transmission electron microscope. Since DIMP is based on a bipolar weighted image integration of the observed defocus series, all the processing of DIMP is performed in real space without Fourier transform. Therefore, the method can be rather easily applied to real-time processing by using a method of irradiation time control of a primary electron beam during accelerating voltage modulation. We have developed a real-time DIMP-EM using accelerating voltage modulation, recently. The original DIMP has presumed the observation under axial illumination, but DIMP can be extended for hollow-cone … More illumination (HCI) to realize much higher resolution, which has been already confirmed in the experiment using an optical microscope. In the present research, DIMP has been extended to HCI using an electron microscope for the first time. The processed image showed 10% higher resolution than the information limit, resulting in the realization of super resolution phase electron microscope having higher resolution than its attainable resolution under axial illumination.As another method to achieve super resolution electron microscopy, three dimensional Fourier filtering method has been mathematically derived using a proposed three dimensional image formation theory. Phase and amplitude images with spherical aberration correction has been confirmed in experiments. In the results, the resolution of the reconstructed phase image was improved from Scherzer resolution limit to the information limit because of the correction of spherical aberration. The 3D Fourier filtering method can be also applied to correct comprehensive aberrations, such as astigmatic aberration and coma aberration. Less