Towards Z-Contrast Imaging in an Aberration-Corrected STEM

Abstract

Abstract The demonstration of an aberration corrector for the STEM promises enormous improvements in the contrast and signal to noise ratio of Z-contrast images, with similar benefits for atomic column EELS. Here we show that the limiting resolution for a zone axis crystal will become not the probe, as in the case of isolated atoms, but the Is Bloch states. In fact, the Z-contrast image becomes a direct image of the Is Bloch states with limiting intensities for large thicknesses roughly proportional to Z The potential benefits for the (STEM) appear to far exceed those for the conventional TEM. Some of these benefits are intrinsic to incoherent imaging: the lack of interference artifacts and the potential factor of two improvement in image resolution were first pointed out by Lord Rayleigh. This improved resolution has been demonstrated by the achievement of sub-ingstrom information transfer in the VG Microscopes HB603U, and the resolution advantage will still apply after aberration correction.