Center for Functional Nanomaterials Seminar

Carrying out electron holography (EH) in gaseous and liquid environment offers a whole new range of opportunities to study in-situ physical and chemical reactions of nanomaterials, plasma effects, and beam effects in general. Inelastic interactions between beam electrons and the molecules of the gas or liquid produce ions, radicals, molecular fragments, free electrons and protons, and many other reactive species that promote local chemical/physical transformations of the sample, whose effects can be directly observed with the phase-sensitive eye of EH.

To establish gas-EH in an environmental TEM (ETEM), we have designed and fabricated an exchangeable electron biprism, which is resistant to corrosive gasses. We have assessed its performance with various gasses, H2, N2, O2, by measuring the change in overlap width, visibility, electron count and phase sensitivity as a function of pressure. The analysis of the data shed light into fundamental aspects of gas-electron interactions, especially regarding coherence loss. Our findings reveal that gas-EH is a viable setup that opens the door to a whole new class of experiments, within fields such as magnetic nanoparticles, catalysis and doped semiconductors.

The combination of liquid-phase TEM and EH, realized at DTU Nanolab with a custom-made nanochannel holder specifically designed for holography experiments, is an entirely new playground for studying liquid-solid interfaces, charge layers, and transport/diffusion processes. I will present our recent results on the determination of the mean inner potential of liquid water, its significance and a range of perspectives and opportunities that this new setup provides.

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