Berlin 2024 – scientific programme

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 6: Instrumentation and Methods for Micro- and Nanoanalysis

KFM 6.1: Talk

Monday, March 18, 2024, 10:40–11:00, TC 010

Dynamical diffraction effects of inhomogeneous strain fields investigated by scanning convergent beam electron diffraction — •Laura Niermann, Tore Niermann, Frederik Otto, and Michael Lehmann — Technische Universität Berlin, Berlin

Strain fields have a large influence on optical and electronic properties of semiconductors. Several transmission electron microscopy (TEM) techniques exist to measure the strain with high precision on a nanometer scale. The models behind these techniques make the assumption that the strain is constant along the electron beam direction. However, if the strain is inhomogeneous in beam direction, the strong diffraction conditions required for the strain mapping cause a non-linear influence on the resulting diffracted electron beam. This effect in turn can also be used to characterize the three dimensional strain field in the specimen. We report on systematical investigations of dynamical diffraction at inhomogeneous strain fields in electron beam direction by using an inclined layer structure producing a continuous change in the depth of the strain field. The strain mapping was performed by means of scanning convergent beam electron diffraction (SCBED) using a fast pixelated detector to record the whole diffraction pattern for each scan position. By comparing the experimental results to calculated diffraction patterns using multi-beam simulations and including effects like surface relaxation and specimen bending, the observed intensity variations can directly be attributed to the dynamical diffraction behavior.

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