High quality superconducting resonators from a magnetically-contaminated sputter system

Magnetic impurities are known to rapidly degrade superconductivity. For this reason, physical vapor deposition chambers that have been used previously for magnetic materials have generally been avoided for making high-quality superconducting resonator devices. In this talk, we show by example that such chambers can in fact still be used following some simple steps to minimize contamination. With niobium films sputtered in a chamber that has been and continues to be used for magnetic materials, we demonstrate compact, 3-μm gap, co-planar waveguide resonators with low-power internal quality factors surpassing one million. We additionally tested three methods of preparing silicon substrates prior to deposition, including anneal steps in the chamber at 700C, finding comparable quality factors. We are using this chamber to test various novel materials for superconducting resonators and Josephson junctions.