Superconducting Thin Films for Magnetic Confinement Fusion: Growth, Electrical and TEM Microstructural Characterization, with Insights into Ion Irradiation

The development of efficient magnetic confinement systems for nuclear fusion reactors requires superconducting materials capable of operating under high magnetic fields, intense irradiation, and demanding thermal conditions. High-temperature superconductors (HTS) are promising candidates for these applications due to their high critical current densities and enhanced magnetic-field tolerance compared to conventional superconductors. This thesis focuses on the growth and comprehensive structural, microstructural, and electrical characterization of superconducting thin films, with particular emphasis on YBa₂Cu₃O₇₋δ (YBCO) and Fe(Se,Te) compounds deposited on engineered substrates and buffer layers. The study aims to investigate vortex pinning mechanisms and their impact on transport properties under conditions relevant for magnetic confinement applications. Thin films were deposited using physical vapor deposition techniques, with growth parameters optimized to achieve high crystalline quality and epitaxial alignment. Structural and interfacial properties were investigated by transmission electron microscopy (TEM and STEM), combined with Fast Fourier Transform analysis and Geometric Phase Analysis, enabling a detailed correlation between lattice matching, strain distribution, and superconducting performance. Electrical transport measurements as a function of temperature, magnetic field, and field orientation were performed to determine the critical temperature, critical current density, and pinning behavior. Special attention was devoted to defect engineering through heavy-ion irradiation, employed to introduce artificial pinning centers. The induced correlated defects were found to significantly modify the pinning landscape, enhancing the in-field critical current density and reducing its angular anisotropy, while preserving the overall crystalline quality of the films.