Atomic imaging in aberration-corrected high-resolution transmission electron microscopy

In recent years, the successful implementation of a spherical-aberration corrector in a Philips CM 200 FEG ST microscope achieved by Haider et al. has attracted a great deal of attention. However, thus far extensive applications of this novel high-resolution transmission electron microscope (HRTEM) to materials research have been hampered by the problems concerning optimum imaging conditions and image interpretation. In this paper, we present our points of view concerning atomic imaging in an aberration-corrected HRTEM. Since atomic resolution images can also be obtained with other techniques such as through-focus exit-wave function reconstruction (TF-EWR), we have to emphasis that the strength of the aberration-corrected HRTEM particularly lies on its ability to resolve the atomic structure in real time. However, for this purpose it is mandatory that the image contrast be related in a one-to-one function with the projected structure of the object. We analyzed the atomic imaging conditions in much detail and we come to the following conclusion: this novel facility is no doubt a powerful and advanced HRTEM instrument in achieving atomic images with its highest resolution (information limit). We furthermore demonstrate that the combination of the new microscope and TF-EWR will yield optimal results.