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TV-rate Atomic-resolution STEM Imaging

Since the development of aberration correction technology, atomic-resolution imaging is routinely available in STEM and the spatial resolution is now reached into deep sub-ångström down to 40.5 pm [1]. In addition to the electron optics, detectors such as complementary metal-oxide-semiconductor (CMOS) camera and silicon drift detector (SSD) have also significantly improved. Although static materials’ analyses are remarkably progressed with the aid of these technologies, it is still lacking in the capability of dynamic observations in atomic-resolution STEM imaging. This is because the present scanning probe system takes a finite time to form an atomic-resolution image, and the temporal resolution is normally in a second per frame [2]. Therefore, in-situ observations are mostly performed in TEM mode owing to their high reading-out time of recent CMOS cameras. Towards high temporal resolution STEM imaging, several approaches have been proposed such as sparse or spiral scanning of the electron probe [3,4], which can reduce the number of sampling pixels or avoid fly-back time. However, the demonstrated temporal resolutions are still in the same order or even worse, compared with the current STEM imaging. In this study, we have developed a new scanning probe system, which has electromagnetic scan coils with a considerably small inductance combined with a short lifetime scintillator for annular dark-field (ADF) STEM. Using this probe scanning system, we have achieved 25 frames per second (fps) with the image size of 512×512 pixels in atomic-resolution ADF STEM imaging, where the acquisition time is 83 ns/pix and the fly-back time for respective line scans is 35 μs. The present scanning system leads to the temporal resolution of 40 msec.