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MM: Fachverband Metall- und Materialphysik
MM 60: Topical Session: In Situ and Multimodal Microscopy in Materials Physics III
MM 60.6: Topical Talk
Thursday, March 21, 2024, 17:00–17:30, C 130
Spatially and Momentum-Resolved Vibrational Spectroscopy in the Electron Microscope — •Benedikt Haas1, Peter Rez2, and Christoph Koch1 — 1Department of Physics & Center for the Science of Materials Berlin, Humboldt-Universität zu Berlin, Berlin, Germany — 2Department of Physics, Arizona State University, Tempe (AZ), USA
Vibrational electron energy-loss spectroscopy was already shown in the 1960s, but it took until 2014 to implement it in an actual electron microscope with sub-nm spatial resolution. This development also allowed for the exploration of larger momentum transfers.
Although optical vibrational spectroscopy techniques (in the form of tip-enhanced methods) have also reached sub-nm resolution, the electron microscope is still unique in being capable of atomically resolving bulk-like specimens, not just surfaces. Recently, we have demonstrated atomically-resolved phonon EELS of extended defects - in excellent agreement with calculations. This study has shown that grain boundaries are not only barriers to phonon transport but can also support localized phonon modes and thus potentially act as phononic waveguides.
Another promising application is momentum-resolved vibrational EELS first demonstrated in 2018. Here, we map phonon dispersion surfaces (in 2D) from momentum-resolved vibrational EELS in combination with suitable theory for quantitative comparison. The technique could be used to visualize anisotropies in phonon transport, e.g. in steady states, or to investigate mode softening.
Keywords: transmission electron microscopy; TEM; electron energy-loss spectroscopy; EELS; phonons