Berlin 2024 – scientific programme

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 8: Microscopy and Tomography with X-ray Photons, Electrons, Ions and Positrons

KFM 8.2: Talk

Monday, March 18, 2024, 12:30–12:50, TC 010

Three dimensional classification of dislocations from single projections — •Tore Niermann, Laura Niermann, and Michael Lehmann — Technische Universität Berlin, Berlin

Many material properties are governed by dislocations and their interactions. Examples range from strengthening of metals and alloys to efficiency in semiconductor laser devices. Thus, knowledge of the three dimensional topology of dislocation networks is crucial for material engineering. A two-dimensional projection of dislocation networks can be readily obtained by conventional (scanning-) transmission electron microscopy (S/TEM) images. However, the reconstruction of the three-dimensional structure of the network so far is mainly achieved by tomographic tilt series with high angular ranges, which is experimentally challenging and additionally puts constraints on possible specimen geometries. Here, we present a new way to reveal the three dimensional position of dislocations and simultaneously classify their type from single 4D-STEM measurements. The dislocation's strain field causes inter-band scattering between the electron's Bloch waves within the crystal. This scattering in turn causes characteristic interference patterns with sufficient information to uniquely identify the dislocations type and position in electron beam direction by comparison with multi-beam calculations. We expect this principle to lead to fully automated methods for reconstruction of the three dimensional strain fields from 4D-STEM measurements in future.

Keywords: (Scanning-) Transmission Electron Microscopy; 4D-STEM; Multi-Beam Simulation; Dynamic Diffraction