Impact of Deposition Method on Structure and Performance of Nb/Si-based Superconducting Coplanar Waveguide Resonators

Structural defects on surfaces and interfaces in superconducting qubits can lead to decoherence and two-level systems (TLS) loss. Using various electron microscopy, electronic transport, and magnetic characterization methods, we reveal the effects deposition methods have on planar Nb on Si resonator performance and TLS loss, and correlate these to material property variations on average grain size, surface roughness, interface chemistry, magnetic and electronic property differences. We find that differences in microstructure and metal-substrate interface correlate with changes in Qi and TLS losses. Our findings highlight the importance of carefully selecting the deposition method to optimize the microstructure and performance of Nb/Si-based superconducting resonators.