Fabrication and Characterization of Nanopatterned NbN Superconducting Nanowires

Metamaterials are artificially structured materials engineered to exhibit electromagnetic, optical, or mechanical properties not typically found in nature. Patterning a crystal can influence its phonon spectrum, and doing so at the nanoscale opens the possibility of controlling electron–phonon interactions in superconductors. This thesis focuses on the fabrication and characterization of nanopatterned superconducting nanowires and thin films as a platform for realizing nanophononic crystal (NPC) structures. Particular attention is given to optimizing electron beam lithography processes and resist development strategies to achieve high-resolution patterning of epitaxial NbN films. Nanowires with 70 nm pitch grid structures and 22 nm wide subwires were successfully fabricated, demonstrating the capability to produce nanoscale patterns with high fidelity. Additionally, large-area nanopatterned superconducting films with a pattern pitch of 100 nm were realized, establishing a foundation for future THz spectroscopy studies aimed at probing phonon-engineering effects in superconductors. Characterization techniques including scanning electron microscopy (SEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM) are employed to evaluate the fabricated structures. Their capabilities and limitations in resolving increasingly smaller features are analyzed, providing insights into both process optimization and metrology challenges at the nanoscale.