Structural studies of nanoparticles with an objective-lens Cs-corrected Titan microscope

Recent tremendous progress in HRTEM made it possible to achieve sub-A resolution in a ‘midvoltage’ microscope through both hardware Cs corrector and software correction, i.e., focus-series reconstructions, to extend the resolution defined by Scherzer defocus to an expected information limit less than 1 A. [1-3]. Such development in microscopy offers improvement for direct interpretation of image contrast and microanalysis with improved spatial resolution in materials science applications. With the tunable Cs, a novel imaging mode is exploited by a combination of a negative Cs and a small overfocus, giving the ‘bright atoms’ contrast [3], which is of great importance and particularly beneficial when imaging weakly scattering light elements. It thus opens up a way to look at the material at atomic level in more detail. Further significant benefits provided by aberration-corrections are the characterization of nanometer–sized particles without delocalized contrast and with largely suppressed phase contrast of the supporting substrate, which make precise size measurement and structure analysis as well as particle evolution observation possible.