Seminar Speaker: Jordan Hachtel, ORNL

The Monochromated Smörgåsbord: A Feast of New Applications for Electron Energy-Loss Spectroscopy at Ultrahigh Spatial and Spectral Resolution

Abstract

Electron energy-loss spectroscopy (EELS) within the scanning transmission electron microscope (STEM) has been widely used to understand composition, bonding, and electronic structure with high spatial resolution in a diverse range of materials. Conventionally, the technique is limited to higher energies (i.e. excitations of greater than 2 or 3 eV) due to the spread of energies from the electron gun. However, over the last ten years breakthroughs in monochromation of the electron source have enabled that limit to drop down orders of magnitude, enabling ultrahigh energy resolution STEM-EELS and access all the way down into the mid-infrared spectral regime. Critically, these breakthroughs have come without compromising spatial resolution, enabling a diverse range of new types of experiments to perform and a rich field of new phenomena to explore. In this talk, I will present a range of materials systems and infrared phenomena that we have been studying at Oak Ridge National Laboratory using our monochromated STEM. Specifically, we will address applications to nanofluidics, thermal heterostructures, biological specimens, and quantum materials. Furthermore, I will focus on the different experimental geometries that become critical in this spectral regime to isolate and enhance different types of scattering and signals that occur in the infrared.

Biography

Jordan Hachtel has been working on spectroscopy in the Nion STEM instruments at ORNL since he first came to the lab as a visiting graduate student in 2013. He received his Ph.D. in physics from Vanderbilt and was hired at ORNL as a postdoctoral researcher in 2016. During his postdoc, he focused heavily on monochromated EELS and was then hired as a staff scientist in 2019. His work in monochromated EELS has been awarded internally by ORNL (winning Outstanding Postdoc of the Year and the Team Research Accomplishment Awards), as well as by major electron microscopy organizations (winning the Cosslett and Heinrich Awards from the Microanalysis Society, the Crewe Award from Microscopy Society of America, and the Innovation Award from the magazine Microscopy Today). As part of the user center, he has applied monochromated EELS to a wide range of materials, such as micro/power electronics, biological specimens, nanophotonic systems, and quantum materials, and is an expert in the different types of phenomena that exist in the ultra-low-loss regime (<1 eV). He is also an expert in advanced data analysis and has an extensive background in applying custom code analytical solutions to monochromated EELS and 4D-STEM through Python and has published extensive curated analyses for public use that have seen wide usage in the community