Title: Multiscale Electron Microscopy of Defects in Nb-Based Superconducting Materials

Abstract: Niobium-based superconductors underpin technologies ranging from particle accelerators to quantum information devices, yet their performance is often limited by nanoscale defects, interfacial disorder, and localstrain. In this talk, I will demonstrate how advanced, multimodal electron microscopy enables a unified,multiscale understanding of these limitations by directly linking structure and composition to superconducting behavior.

For Nb₃Sn, I will show how different growth methods produce distinct defect populations using Focused Ion Beam–Scanning Electron Microscope (FIB-SEM) and spectroscopic imaging. Next, by combining 4D-STEMwith quantitative Energy Dispersive X-Ray Spectroscopy (EDX), I establish direct correlations between local composition and lattice distortions, and introduce a three-dimensional strain mapping approach thatreveals a strain-stabilized tetragonal phase at room temperature. Furthermore, at the atomic scale, multislice electron ptychography (MEP) visualizes point defects and resolves intermediate configurations in defect formation pathways that are not accessible to conventional approaches.

For superconducting thin films used in quantum devices, I examine interfacial disorder associated with dielectric loss. I will show how capping layers suppress oxide formation, and how MEP enables three-dimensional characterization of nanocrystalline oxide layers.

This multiscale characterization demonstrates how next-generation electron microscopy can uncover the structural origins of performance-limiting defects and guide the design of improved superconducting materials.