de Leon, Nathalie P.Umbarkar, Esha A.2025-08-072025-08-072025-04-28https://theses-dissertations.princeton.edu/handle/88435/dsp01jd473091sTantalum superconducting resonators have demonstrated state-of-the-art performance with long coherence times and high quality factors, motivating further study into the sources of microwave loss that limit their performance. An investigation into these sources reveals that two-level systems (TLSs) dominate loss at low powers and temperatures, but at higher temperatures there is an additional source of microwave loss arising from dissipation due to vortex motion. This microwave loss has been observed to reduce in dirty limit films where the mean free path lis shorter than the coherence length ξ, due to defects and roughness pinning vortices and preventing motion-induced dissipation. These results have been replicated with manufactured artificial defects in clean limit films (l >> ξ) where a pattern of holes with lattice parameter a is fabricated on the resonators. However, this additional patterning increases TLS loss at grain boundaries and edges, motivating further research into pinning pattern design. In this study, we vary the lattice parameter a with a fixed hole diameter d to identify the limits of artificial pinning. We first deposit films and verify that we are in the clean limit through magnetoresistance, x-ray diffraction, surface measurements, and imaging. We then fabricate multiple patterns, and compare the effectiveness of vortex pinning through quality factor measurements conducted at millikelvin temperatures. We estimate theoretically that a0 ≈200µm, and find that for a= 300µm the vortices are fully unpinned, but there is no additional microwave loss from defect patterning. We suggest patterns for future research in order to better probe the depinning transition and partially pinned regime.en-USPrinceton University Senior Theses