Yakun YUAN

Innovations in the ways we observe the world is the foundation for modern science and technology development. However, traditional methods can only capture the spatially averaged information, and are not sensitive to defects, dopants, and disorders, which usually determines the performance of functional materials. In addition, characterizing the static properties of materials does not meet the needs for understanding various dynamical processes, limiting the exploration of new phenomena of materials on time dimension.

Yakun Yuan’s research interests focus on developing novel multi-dimensional, high-precision characterization methods and solving important problems in materials research.

For epitaxial thin film systems, Yuan developed and improved an interfacial imaging method based on phase-retrieval techniques and synchrotron X-ray radiation, namely, Coherent Bragg Rods Analysis (COBRA). With this method, he ,for the first time, obtained the complete 3D atomic structure of such interfaces and revealed a comprehensive picture of interplays between electric polarization and octahedral tilt, which could serve as a general principle in device design, ‘Tilt Epitaxy’. Based on this principle, he and his colleagues also realized the first artificially stabilized polar metal, with the coexistence of two counter-intuitive properties in one material – electric polarization and metallicity.

For nanomaterials systems, Yuan further developed Atomic Electron Tomography (AET) based on aberration-corrected electron probe and real-space iterative tomography algorithm and achieved the highest spatial precision at single atom level in 3D. Traditional crystallography methods are only applicable to periodic structures and are not compatible with modern materials research at atomic level. The new AET is a unique method that can tackle such problems. With this method, for the first time, he characterized the 3D atomic structures of metallic thin films and nanoparticles near glass transition.