Improving Performance of Tantalum Resonators through Deposition, Part II

The cubic phase of tantalum is a very promising material for superconducting transmon qubits, due to its self-limiting surface oxide, low bulk losses, and low kinetic inductance. However, sputtering high-quality tantalum films on silicon often requires using either a seeding layer or high substrate temperatures, both of which introduce possible sources of loss. We present a novel method of growing state-of-the-art tantalum films on silicon with magnetron sputtering using a significantly lower substrate temperature than found in literature. In this second part of a two-part talk, we will present on devices made from our novel state-of-the-art tantalum films deposited on silicon. Using coplanar waveguide resonators, we measure the losses and microwave performance of our films, achieving single photon quality factors above four million for a 3-μm gap resonator.