Rafal E. Dunin-Borkowski, Lei Jin, András Kovács, Andreas Thust

Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, 52425 Jülich, Germany

When combined with careful sample preparation, modern spherical aberration corrected transmission electron microscopes can be used to provide direct images of the internal structures of materials with a spatial resolution that can approach 50 pm. The positions of individual atomic column positions in such images can be measured with pm precision to provide indirect information about local functional properties, such as ferroelectric polarization, on a unit cell scale. When combined with a precise knowledge of aberration coefficients and other parameters that describe the electron optics and stability of the microscope, quantitative comparisons between individual experimental images and quantum mechanical image simulations on an absolute scale can now be used to obtain information about the local sample thickness and atomic arrangement on the sample surface. With the recent introduction of chromatic aberration correction, a spatial resolution of better than 0.1 nm can be achieved at microscope accelerating voltages of below 50 kV, providing new opportunities for high-resolution imaging of electron-beam-sensitive materials, while the combination of high-resolution transmission electron microscopy with off-axis electron holography and electron magnetic circular dichroism offers exciting prospects for the direct imaging of local magnetic properties in materials and devices on the atomic scale.

In this talk, a selection of challenges and opportunities for the further development of high-resolution transmission electron microscopy will be presented and discussed. In particular, improvements in spatial resolution towards the diffraction limit are likely to require radical changes to the design of electron microscopes, while more precise measurements of local material properties will require the automation of longer experiments, a better knowledge of microscope and specimen parameters, the use of ultra-high-vacuum technologies and improved specimen stages to provide a clean and stable sample environment, quantitative comparisons of experimental measurements with both complementary techniques and advanced simulations, and new approaches for data handling and storage.