Reducing electron beam damage through alternative STEM scanning strategies. Part I -- Experimental findings

TL;DR

This study experimentally compares traditional raster and interleaved STEM scan patterns on zeolite samples, finding that scan strategy significantly influences electron beam damage, with interleaved patterns reducing damage by up to 11%.

Contribution

It introduces a programmable scan engine to systematically compare scan patterns, revealing that scan strategy impacts damage independently of dose parameters.

Findings

Interleaved scan pattern reduces damage by up to 11%.

Scan strategy affects beam damage beyond dose and dose rate.

Reproducible experimental approach for damage assessment.

Abstract

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 irreproducibity issues, circumstantial evidence, rumours, 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 behaviour 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 mutliple 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.