Dr. Tao Ma Presenting at Oakland University Physics Colloquium

Dr. Tao Ma, (MC)2 Lead TEM Scientist, will be presenting in Oakland University’s Department of Physics Colloquium, on October 10 (12:00-1:00 PM, Room 185 MSC). 

Atomistic characterizations of functional materials via transmission electron microscopy

Transmission electron microscopy (TEM) has revolutionized materials characterization by enabling imaging and spectroscopy at atomic resolution, owing to significant advances such as aberration correctors and different imaging techniques. TEM has become an indispensable tool for bridging material properties with their atomic structures. The talk highlights three examples showcasing various aspects of TEM techniques, and demonstrates the pivotal role of TEM in advancing understanding of functional materials at the atomic level.

  1. In-situ observation of intermetallic phase transformation in Pt–Sn system

This study investigates the phase transformation dynamics of Pt3Sn and PtSn in Pt/SnO2 nanoparticles at elevated temperatures with atomic resolution. We discovered that surface-mediated diffusion of Sn governs the overall reaction dynamics, while the unique coherent interfacial structure is crucial for the PtSn transformation. These findings provide experimental evidence on the alloying mechanism in intermetallic nanoscale systems, offering insights into the synthesis and catalytic properties of intermetallic nanoparticles.

  1. Direct visualization of atomic structures of incommensurate modulations in PbZrO3-based perovskite antiferroelectrics

Using TEM, we revealed the atomic structures of incommensurate modulations in chemically modified lead zirconate antiferroelectrics. By precisely quantifying atom positions, we found that Pb-cation displacements are either antiparallel with different magnitudes or nearly orthogonal, challenging the previously assumed fully compensated antiparallel arrangement. The atomic configuration of 90° domain boundaries was also visualized. While the polarity transition in undoped PbZrO3 can be as narrow as one atomic layer, it can expand to several primitive cells in chemically modified compositions with incommensurate modulations. These findings enhance our atomistic understanding of polar structures in perovskite antiferroelectrics.

  1. Revealing chiral structures in multiscale

Chiral materials exhibit diverse applications, including optical emission, drug delivery, and catalysis. Their properties stem from structural chirality, where materials are categorized as left-handed or right-handed which are “mirror images” of each other. Imaging is the most intuitive method for distinguishing chirality, but normal TEM micrographs compress 3D structures into 2D projections, losing critical information. By employing TEM tomography, we reconstructed the 3D structure of chiral materials, directly revealing their chirality. Furthermore, the chiral lattice was verified by taking atomic-resolution images at various tilt angles. These observations provide direct evidence of structural chirality.