High-Q Tantalum Superconducting Resonators Fabricated at Room Temperature

The use of α-tantalum in superconducting circuits has enabled a considerable improvement of the coherence time of transmon qubits. The standard approach to grow α-tantalum thin films on silicon involves heating the substrate, which takes several hours per deposition and prevents the integration of this material in wafers containing temperature-sensitive components. In this presentation, we will demonstrate the potential of an alternative growth method, achieved at room temperature through the use of a seed layer, for the fabrication of superconducting resonators. Despite substantial differences in material properties between the films deposited at high and room-temperature, resonators produced with both types of films are found to have comparable state-of-the-art quality factors. We will discuss how this finding challenges previous assumptions regarding correlations between material properties and microwave loss of superconducting thin films.