Charting New Territory in Materials Science with Cryo Electron Microscopy

Modern scanning and transmission electron microscopes (S/TEM) have become almost ubiquitous in materials and biological sciences laboratories. They have significantly advanced our understanding of matter at the atomic level, providing unique insights into the structure, chemical composition, and electronic properties of materials. Furthermore, the recent development of stable cryogenic TEM holders, which operate at temperatures ranging from liquid nitrogen (100 K) to 300 K and include electrical contacts, combined with aberration-corrected and monochromated electron optics, has enabled S/TEM to study magnetic, structural, and electronic phase transitions with unprecedented spatial and energy resolutions. <br/><br/>In this talk, I will present two examples of cryogenic STEM measurements done in a set of two-dimensional (2D) transition metal dichalcogenides (TMDs) and hexagonal boron nitride (hBN) samples. In the first example I will address excitonic dephasing in MoS₂, and how local strain can affect the excitonic properties of hetero TMDs bilayers. In the second example, I will present our efforts to try to measure chiral properties in hBN using monochromated EELS in the phonon and core-loss energy regimes. Prospects and limitations of future experiment will be discussed in the detail during the talk. [1]<br/><br/>[1] The EELS part of this research was supported by the Center for Nanophase Materials Sciences, which is a Department of Energy Office of Science User Facility. This research was conducted, in part, using instrumentation within ORNL’s Materials Characterization Core provided by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. This work was also partly funded under the Laboratory Directed Research and Development Program at Pacific Northwest National Laboratory, a multiprogram national laboratory operated by Battelle for the U.S. Department of Energy. The TMDs TEM sample preparation was supported by the UW Molecular Engineering Materials Center, an NSF Materials Research Science and Engineering Center (Grant No. DMR-2308979).