Measuring 3D chemistry at 1 nm and below
Robert Hovden
Associate Professor, Materials Science and Physics
University of Michigan
Tuesday, November 5, 2024
11 a.m.
In-person: C2-361
Abstract: For electron tomography, dose and resolution are inextricably linked—the maximum achievable 3D resolution is ultimately limited by the total allowable dose. Higher 3D resolution demands more specimen projections and exceedingly high SNR. This has made high-resolution chemical tomography intractable until recently. Here we show fused multi-modal electron tomography is the essential to enabling 3D chemical imaging at higher theoretical resolutions and dramatically reduced dose. Fused multi-modal electron tomography notably improves both the sampling and dose constraints that limit resolution across a range of radiation sensitive materials. We experimentally demonstrate fused multi-modal tomography by imaging at resolution < 1 nm in a beam sensitive material (Fe/Au embedded in Polystyrene-based ligands). The novel technique is theoretically, computationally, and experimentally validated. We emphasize three innovations for chemical electron tomography when utilizing multi-modal data fusion: (1) By linking the physics of elastic Rutherford scattering and inelastic core-loss scattering, dose can be reduced by upwards of two orders of magnitude. This addresses the key limits to 3D chemical imaging at high-resolution or on beam-sensitive materials. (2) Mixed inelastic and elastic signals can be sampled independently to break traditional 3D resolution limits for chemistry. (3) Chemical stoichiometry can be retrieved with higher precision and do so without knowledge of elemental inelastic cross-sections. These aspects have been discussed theoretically and demonstrated experimentally.
Robert Hovden is an Associate Professor in Materials Science and Physics at the University of Michigan. He completed his BS in Physics at the Georgia Institute of Technology and a PhD in Applied Physics at Cornell University. Utilizing advanced electron microscopy he unveils new understanding of how structure at the pico-, atomic- and nano-scale determines material properties at the macroscale—spanning a wide class of systems including twisted 2D materials, charge density waves, clean energy materials, and biominerals.