Dose efficient annular bright field contrast with the ISTEM method: A proof of principle demonstration

• Published in: Ultramicroscopy Vol. 245; p. 113661
• Main Authors: Krause, Florian F., Schowalter, Marco, Gerken, Beeke, Marquardt, Dennis, Grieb, Tim, Mehrtens, Thorsten, Mahr, Christoph, Rosenauer, Andreas
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.03.2023
• Subjects: ABF STEM; Aperture manufacturing; ISTEM; Light atom imaging; Principle of reciprocity; ABF STEM; ISTEM; Principle of reciprocity; Light atom imaging; Aperture manufacturing
• ISSN: 0304-3991; 1879-2723
• DOI: 10.1016/j.ultramic.2022.113661

The ISTEM mode for TEM has been demonstrated to have several advantages in regard to resolution and precision. While previous works primarily focussed on the advantages due to the reduced spatial coherence, the actual image contrast, i.e. how bright or dark certain atom columns are imaged, has mostly been of secondary concern. The present work sets out to achieve the contrast of annular bright field STEM in ISTEM, producing the high contrast of light elements, for which this method is popular. It is shown from theoretical considerations that using an annular condenser aperture this aim can be realised. The optimal size of this aperture is found by simulative studies. It is then manufactured from platinum foil and installed in an image-aberration corrected microscope. ABF-like ISTEM images of strontium titanate in [100] projection are acquired. The pure oxygen columns are clearly resolved with significant contrast. The image pattern is indeed identical to what is achieved by ABF STEM. A close look at the image formation also shows that the dose needed for a given signal-to-noise ratio is at least a quarter smaller for ABF-like ISTEM compared to ABF STEM, assuming detectors of similar detective quantum efficiency. •ABF-like contrast was achieved with ISTEM imaging mode.•Annular condenser aperture was manufactured for FEI microscope by FIB.•Scan noise and source size effects are avoided.•Light atoms can be detected with relatively high contrast in neighbourhood of heavy atoms.•Oxygen atoms clearly resolved in ABF-like ISTEM images of strontium titanate.