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New opportunities and challenges for electron microscopy

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In recent decades, electron microscopy has been radically transformed by revolutionary advances in imaging (at the sub-Angstrom level with aberration-corrected lenses), in spectroscopy (now approaching 10 meV) and in specimen preparation (with the focused ion beam). These advances allow many problems to be addressed more effectively but do not automatically deal with all the current challenges we face. Now that further development is largely left to the manufacturers and the traditional early stage, in-house innovation is not encouraged by research funding, several less ambitious developments in instrumentation or technique which might be useful have stayed in limbo. Another problem arises from the modern microscope designs where somewhat opaque software operating systems make it difficult to implement older imaging procedures that might in some cases be more effective. Many samples with complex 3D structure are quite unsuitable for the 2D projection imaging widely used in high resolution imaging. In some cases tomography has offered a solution and more recently depth section imaging of dislocation core structure looks promising. Simple diffraction contrast imaging has fallen out of fashion but has recently been revived for the observation of charge-discharge processes in batteries and may be important in drive towards phonon imaging. Secondary electron imaging can now reach < 1nm spatial resolution and shows some promise in characterising the nanostructure of solar cells. However we still lag behind the surface scientists in spectroscopy of clean surfaces. Pioneering work on picosecond scale time-resolved electron microscopy clearly demonstrated the value of specimen pumping using tuned EM radiation but its wider potential for improved electron spectroscopy has not been actively taken up. We cannot of course avoid the black body radiation that bathes our specimens giving rise to energy loss and gain processes that are now measureable. At still lower energies, the decoherence effects produced by Johnson noise in the conducting components of the microscope present an intriguing challenge.

This talk is part of the Surfaces, Microstructure and Fracture Group series.

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