A strategy for dose-efficient atomic-resolution OBF-STEM imaging of zeolites.

Observation of beam-sensitive materials in scanning transmission electron microscopy (STEM) requires not only the development of highly dose-efficient imaging techniques but also the selection of appropriate imaging conditions such as the raster-scan sampling rate and optical parameters to realise a low-dose condition effectively. In this study, the convergence angle, sampling rates, and electron dose dependencies of the signal-to-noise ratio in optimum bright-field (OBF) STEM, a recently developed dose-efficient STEM imaging method, are investigated, which guides us in choosing optimal conditions to observe beam-sensitive porous materials such as zeolites. The parameters necessary for real-time OBF imaging are also considered towards practical live imaging at low dose. Experimental atomic-resolution OBF STEM observations of zeolites are then demonstrated using the strategy investigated above.