Artifacts in aberration-corrected ADF-STEM imaging

The introduction of an experimental black level may introduce unintended artifactual details into high-resolution annular dark field scanning transmission electron microscopy (ADF-STEM) lattice images. This article presents the multislice simulation results of such possible situations. Three simulated scanning transmission electron microscopy (STEM) probes of sizes 0.8, 1.2 and 2.0 Angstrom are scanned on the surface of a <(1) over bar 10> oriented Si/Ge crystal. The simulation results suggest that high-frequency artifact peaks will appear in the power spectra when an artificial black level clips the lowest (background) signal. The lowest signal in an ADF-STEM image decreases as the incident probe shrinks in size. Therefore, care must be taken when interpreting the resolution limit of the microscope from images taken with nonzero black level setting, especially in case of sub-Angstrom microscope. The simulation result is compared with an experimental image and they agree with each other. The analysis suggests that aberration corrected STEM provide sensitive low level detail. (C) 2003 Elsevier Science B.V. All rights reserved.