Gigabytes of data, picometers of precision:

There has been a hardware revolution in transmission electron microscopy in recent
years as advances in aberration correction and electron detectors have pushed both the
achievable resolution and the information that can be extracted. While aberration
correction has resulted in routine measurements of picometer scale displacements in
materials, high-speed direct electron detectors now enable the entire diffraction pattern
to be captured from every scan point. Such multidimensional datasets, also known as
4D-STEM, are the starting points for high precision strain measurements with
nanobeam diffraction, electric field measurements with differential phase-contrast
microscopy, and super-resolution microscopy through ptychography. This talk will focus
on using these techniques to image ferroelectric displacements across domain walls,
charge accumulation at domain walls in polar metals, and picometer precision strain
measurements in catalyst nanoparticles. The associated software toolkits developed for
these analyses will also be presented, along with upcoming developments that combine
advanced computing with the microscope to speed up data analysis bottlenecks.
Biography
Debangshu Mukherjee received his undergraduate degree in Metallurgical and
Materials Engineering from IIT Kharagpur in 2011. Following an MS on photonic
materials at Boston University in 2013, he obtained his Ph.D. in Materials Science &
Engineering from The Pennsylvania State University in 2018. At Penn State, his
research focused on measuring ferroelectric displacements with aberration-corrected
STEM – specifically lithium niobate. Since his Ph.D., he has been at Oak Ridge National
Laboratory as a postdoctoral researcher, and currently as a staff scientist, where he is
working on developing experiments and analysis software for 4D-STEM, specifically its’
applications to catalyst nanoparticles. He is the primary author of the STEMTool Python
package for analyzing electron microscopy datasets, for which he was awarded the
2020 MSA postdoctoral scholar award.