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Young Investigator Group Dr. Knut Müller-Caspary

moreSTEM - Momentum-resolved Scanning Transmission Electron Microscopy

Recent publications

Atomic-scale quantification of charge densities in two-dimensional materials

Knut Müller-Caspary, Martial Duchamp, Malte Rösner, Vadim Migunov, Florian Winkler, Hao Yang, Martin Huth, Robert Ritz, Martin Simson, Sebastian Ihle, Heike Soltau, Tim Wehling, Rafal E. Dunin-Borkowski, Sandra Van Aert, and Andreas Rosenauer,  Publication (PDF, 3 MB)

Charge and transport in 2D materials

This research line focuses on the quantitative experimental mapping of charge densitites at (sub-) atomic scale in 2D-materials with high precision. Enhancing the sensitivity of momentum-resolved STEM to detect bonding, to investigate charge redistributions at point and extended defects, and to study the electrical properties of 2D devices under external bias are major objectives here.

Ferroelectric materials

Ferroelectric materials such as Barium Titanate exhibit a spontaneous electrical polarisation, which can be used in high-density, non-volatile, energy-efficient data storage devices. This research line targets the mapping of the ferroelectric polarisation in ferroelectric tunnel junctions which consist of an ultrathin ferroelectric layer epitaxially grown between 2 contacts. In fact, this work is supposed to shed light on the degradation an dysfunction of ferroelectric devices that exhibit, however, favorable geometries from the application point of view.

1D nanostructures

Nanowires play a central role in the research on sensing, photovoltaics, nanoelectronics and catalysis. Alloying Au nanowires with other metals is expected to enhance the stability over pristine wires, which currently hampers applications. This research line is dedicated to the mapping of the chemical composition in alloy nanowires, which is essential to understand and taylor their physical properties for electrical and catalytic applications. Momentum-resolved STEM is in principle capable of this in terms of evaluating the distinct angular dependence of scattered intensity, but lacks a quantitative understanding of electron scattering at low angles. Improving theoretical models and simulation approaches in this angle regime is hence a key challenge of this project and a paradigm demonstration how fundamental and applied science can complement each other.

Additional Information

Helmholtz Young Investigator Group

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moreSTEM - Momentum-resolved Scanning Transmission Electron Microscopy

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