Reducing electron beam damage through alternative STEM scanning strategies, Part I: Experimental findings

• Published in: Ultramicroscopy Vol. 232; p. 113398
• Main Authors: Velazco, A., Béché, A., Jannis, D., Verbeeck, J.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.01.2022
• Subjects: Electron beam damage; Electrons; Scanning strategies; Scanning transmission electron microscopy; Electron beam damage; Scanning transmission electron microscopy; Scanning strategies
• ISSN: 0304-3991; 1879-2723
• DOI: 10.1016/j.ultramic.2021.113398

The highly energetic electrons in a transmission electron microscope (TEM) can alter or even completely destroy the structure of samples before sufficient information can be obtained. This is especially problematic in the case of zeolites, organic and biological materials. As this effect depends on both the electron beam and the sample and can involve multiple damage pathways, its study remained difficult and is plagued with irreproducibility issues, circumstantial evidence, rumors, and a general lack of solid data. Here we take on the experimental challenge to investigate the role of the STEM scan pattern on the damage behavior of a commercially available zeolite sample with the clear aim to make our observations as reproducible as possible. We make use of a freely programmable scan engine that gives full control over the tempospatial distribution of the electron probe on the sample and we use its flexibility to obtain multiple repeated experiments under identical conditions comparing the difference in beam damage between a conventional raster scan pattern and a newly proposed interleaved scan pattern that provides exactly the same dose and dose rate and visits exactly the same scan points. We observe a significant difference in beam damage for both patterns with up to 11 % reduction in damage (measured from mass loss). These observations demonstrate without doubt that electron dose, dose rate and acceleration voltage are not the only parameters affecting beam damage in (S)TEM experiments and invite the community to rethink beam damage as an unavoidable consequence of applied electron dose. •An alternative interleaving pattern is compared to the conventional raster pattern in terms of beam damage.•Both methods provide the same electron dose and spatial resolution. However, a different distribution of the dose in time and space is achieved with the alternative pattern.•Automated experiments on a commercial zeolite sample were performed to increase the reproducibility of the results.•The methodical experiments show that the alternative scanning, compared to the raster scanning, systematically reduces electron beam damage.•A general diffusion model is employed in an attempt to empirically model the observed damaging process.