Upgrade of the existing transmission electron microscope for 4D STEM microscopy

• Subject Area: Materials Science
• Term: Funded in 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 552804360

The professorship for Structure and Microstructure of Materials operates the only transmission electron microscope (TEM) available at the TU Bergakademie Freiberg (TU BAF). This device and the corresponding technical expertise of this research group are involved not only in its own research, but also in the research of many other institutes at the TU BAF. The existing device is a high-resolution, analytical TEM that is equipped with a field emission gun, a Cs corrector lens in the primary beam for correction of the spherical aberration, a high-resolution objective lens, an in-column filter for energy filtering and electron spectroscopy, and a high-angle annular dark-field detector. The device was purchased in 2010 within the Saxon Cluster of Excellence “Functional Structure Design of New High-Performance Materials by Atomic Design and Defect Engineering (ADDE)”. Within the requested upgrade, the existing analytical methods are to be extended to incorporate 4D STEM, the non-functioning EDX detector is to be replaced and the wear components overhauled. The acronym 4D STEM stands for the acquisition of two-dimensional electron diffraction images in two-dimensional TEM scan mode. 4D STEM microscopy is intended to work with a nanoscale primary beam that either has an adjustable convergence or is directed onto the sample as a parallel precessing beam. The convergence or precession of the primary beam create a tilt of the Ewald sphere around the origin of the reciprocal space, which enables scanning of a larger area of the reciprocal space - either in an integrating mode or in discrete steps. This allows additional reciprocal lattice points from the Zeroth Order Laue Zone (ZOLZ) and from the High Order Laue Zone (HOLZ) to be measured. This option improves significantly the accuracy of the determination of the distances in the reciprocal space and enables a reliable determination of the local lattice strain. The higher coverage of the reciprocal space also enables rapid phase identification and orientation analysis in nanoscale objects, and thus rapid mapping of the phase composition and orientation relationships between neighboring crystallites or neighboring phases. Concurrently, the precession of the primary beam suppresses dynamic effects in the diffraction pattern, which makes the determination of the crystal structure of nanoscale phases using kinematic diffraction theory more reliable. The requested upgrade includes the procurement and installation of the hardware and software for controlling the electron optics and for recording and evaluating the 4D STEM data, the upgrade of detectors (EDX detector, CMOS camera) and the overhaul of the electron gun and the getter pump. On this application, working groups from three of the six faculties at TU BAF are participating.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Upgrade des vorhandenen Transmissionselektronenmikroskops für 4D STEM-Mikroskopie
• Instrumentation Group: 5100 Elektronenmikroskope (Transmission)
• Applicant Institution: Technische Universität Bergakademie Freiberg
• Leader: Professor Dr. David Rafaja