Transmission electron microscopy with atomic resolution under atmospheric pressures
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Transmission electron microscopy with atomic resolution under atmospheric pressures Sheng Dai and Wenpei Gao, Department of Chemical Engineering and Materials Science, University of California Irvine, Irvine, California 92697, USA Shuyi Zhang and George W. Graham, Department of Chemical Engineering and Materials Science, University of California Irvine, Irvine, California 92697, USA; Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA Xiaoqing Pan, Department of Chemical Engineering and Materials Science, University of California Irvine, Irvine, California 92697, USA; Department of Physics and Astronomy, University of California Irvine, Irvine, California 92697, USA Address all correspondence to Xiaoqing Pan at [email protected] (Received 5 July 2017; accepted 25 October 2017)
Abstract Significant developments in micro-electrical-mechanical systems-based devices for use in transmission electron microscopy (TEM) sample holders have recently led to the commercialization of windowed gas cells that now enable the atomic-resolution visualization of phenomena occurring during gas–solid interactions at atmospheric pressure. In situ TEM study under atmospheric pressures provides unique information that is beneficial to correlating the structure–properties relationship of nanomaterials, particularly under real gaseous environments. We here provide a brief introduction of the advanced instrumentation of windowed gas cells and review recent progress of in situ atomic-resolution TEM study under atmospheric pressures, including some application examples of oxidation and reduction processes, dynamic growth of nanomaterials, catalytic reactions, and “operando” TEM.
Introduction Transmission electron microscopy (TEM), combining high spatial and spectral resolution is always considered as a powerful and indispensable tool for structure characterization and chemical analysis.[1–6] Over the past decades, the applications of TEM have expanded from static characterizations to in situ observations and live measurements, providing great opportunities in various fields from materials science to chemistry and biology. With the adoption of the aberration corrector[7–10] and micro-electro-mechanical system (MEMS) devices[11–18], it is now possible to image the real-time dynamic change at atomic scale under various external stimuli, such as applied heat, stress, bias, and gaseous or liquid environments, while simultaneously measuring relevant properties.[19–29] Among them, the in situ TEM study under atmospheric pressures is a fast-growing and fascinating area, attracting attention not only from basic scientific research but also for important industrial applications. By utilizing the advanced windowed gas cell technique, the atmospheric gas phase reactants are allowed to flow over the samples (at elevated temperatures) in a miniaturized space at the tip of the TEM holder, and the morphology and structure evolution can be directly revealed through S/TEM imaging, electron di
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