Uncovering atomic arrangements in epitaxial systems using synergistic computational and experimental approaches

In nanostructured materials, every atom counts; thus, determining the atomic arrangements is critical for their precise design and fabrication for targeted applications in energy and electronics. However, it is often challenging to unambiguously identify the atomic structure, particularly for heterogenous systems, using either theoretical modeling or experimental imaging alone. In our recent studies, we developed and applied a synergistic computational and experimental approach to precisely map the atomic structure and infer growth mechanisms at the nanoscale. In this talk, I will demonstrate our approach in two different case studies. In the first one, we applied a multi-tier density functional theory (DFT), classical force fields, and genetic algorithms in conjunction with in situ characterization to determine atom-by-atom the structure of supported metal clusters on a two-dimensional substrate. In the second application, we examined the Cu₂O nano-island epitaxial growth mechanism using correlated in situ environmental transmission electron microscopy, statistically-validated quantitative analysis, and DFT calculations. We showed that the oxide islands grow layer-by-layer along Cu₂O(110) planes, regardless of substrate orientation, contradicting classical models that predict multi-layer growth parallel to substrate surfaces. Growth kinetics show cubic relationships with time, indicating individual oxide monolayers follow Frank-van der Merwe growth, whereas oxide islands follow Stranski-Krastanov growth. Our results demonstrate that epitaxial systems can be “visualized” at the atomic scale using concerted approaches, which is critical for advanced manufacturing at the nanoscale.