Event
MSE Seminar: Dr. Yichao Zhang, University of Illinois Urbana-Champaign
Wednesday, March 13, 2024
3:30 p.m.
Room 2110 Chemical and Nuclear Engineering Building
Sherri Tatum
301 405 5240
statum12@umd.edu
Ultrafast and Ultrasmall: Probing Dynamics at Atomic Interfaces with Advanced Electron Microscopy
Abstract: Solid-state dynamic processes, spanning from attoseconds to minutes and beyond, play a major role in advancing the technological frontiers, from superconducting qubit switching to nanoelectronic functionality. The prevalence of structural heterogeneities and the imperative to manipulate energy and matter at the atomic level require investigations extending beyond ideal systems and ensemble measurements both spatially and temporally. In this talk, I will describe our efforts in probing local structure-property relationships at atomic interfaces using a combination of in situ transmission electron microscopy (TEM), aberration-corrected scanning TEM (STEM), 4D ultrafast electron microscopy, and electron ptychography. The combination of these electron microscopy techniques allows us to access spatial and temporal domains spanning from nanometer to deep sub-angstrom (<0.5 Å) and from milliseconds to picoseconds. First, I will present the direct imaging of phonon propagation in a defect-laden van der Waals material and the interaction between a phonon and a single defect at the nanoscale. Next, I will show how moiré superlattices undergo local reconfiguration to form nanoscale aligned structures and the atomic mechanisms governing such structural transformations. Lastly, I will discuss our approach to achieving atom-by-atom mapping of novel phonon modes in moiré superlattices. These fundamental understandings enable functionalization of discrete structure features and the design of low-dimensional heterostructures with precise nanoscale control for next-generation devices. Furthermore, I will describe how we can harness the combined high spatial and temporal resolutions of emerging in situ, time-resolved electron microscopy techniques to observe atomic-scale thermodynamic and kinetic mechanisms of several key dynamic processes, including phase transformation, polarization switching, domain dynamics, strain relaxation, and defect dynamics. These mechanistic insights serve as a blueprint for designing new structures for quantum, energy, and nanoelectronic devices with atomic precision.
Bio: Dr. Yichao Zhang is currently a postdoctoral associate at the University of Illinois Urbana-Champaign. She earned her PhD from the University of Minnesota as a Louise T. Dosdall fellow and Phi Kappa Phi doctoral dissertation fellow. Yichao combines ultrahigh spatial and temporal resolutions of in situ electron microscopy techniques to explore energy transport and structural transformations at the nano to atomic scale. Her work has been recognized by the Microscopy Society of America. Besides scientific pursuits, Yichao is devoted to promoting diversity and inclusivity in STEM.
