AVS 65th International Symposium & Exhibition
    Materials and Processes for Quantum Computing Focus Topic Tuesday Sessions
       Session MP+EM+NS-TuM

Paper MP+EM+NS-TuM1
MBE Grown Nitride Superconductors for Quantum Circuits

Tuesday, October 23, 2018, 8:00 am, Room 203A

Session: High Coherence Qubits for Quantum Computing
Presenter: Christopher Richardson, Laboratory for Physical Sciences
Authors: C.J.K. Richardson, Laboratory for Physical Sciences
A. Alexander, Laboratory for Physical Sciences
C. Weddle, Laboratory for Physical Sciences
Correspondent: Click to Email
Low microwave loss superconducting capacitors and inductors are critical circuit components of superconducting qubits. For transmon qubits, the ability to make high-quality planar resonators is an essential part of fabricating highly coherent qubits. Plasma assisted Molecular beam epitaxy (PAMBE) is used to grow niobium titanium nitride alloys (NbxTi1-xN) directly on silicon (111) wafers. Using a structure first approach to design optimization, the structural, surface topology, chemical characteristics, and superconducting critical temperature of these films are used for optimization of the growth conditions before resonators are fabricated and tested. Here focus will be on the optimization of PAMBE-TiN films grown under slightly nitrogen rich conditions and high growth temperatures. Using films grown on high resistivity wafers, resonators are fabricated from coplanar waveguides with a narrow 6-µm wide center conductor and nominal 500-nm deep trench etch. Cryogenic testing at 100mK demonstrate low microwave loss that is evident from measured internal quality factors that are over 1M in the single photon regime and approach 10M at high powers. The motivation of using PAMBE to grow superconductors and the favorable comparison with resonators made from leading films synthesized with sputter deposition will also be discussed.