Dielectric Loss in Titanium Nitride and Aluminum Superconducting Resonators*

Uniquely characterizing loss from two-level systems (TLS) in dielectric materials in coplanar waveguide resonators is challenging due to the nearly proportional scaling of the electric field participation in response to changes in geometry and anisotropic trench depth. With isotropic trenching, however, we can design a set of device geometries where each geometry amplifies the participation of a specific dielectric region. We fabricate this set of devices for both titanium nitride (TiN) and aluminum (Al) resonators and characterize the specific loss tangent of each dielectric for both materials [1]. In this talk, we show that the metal-air interface is the dominant loss in Al devices, whereas each dielectric region contributes significantly in TiN. Lastly, a post-process hydrofluoric (HF) etch reduces losses from the substrate-air interface in TiN devices [2].
[1] Woods, Phys. Rev. Appl. 12, 014012 (2019)
[2] Melville, Appl. Phys. Lett. 117, 124004 (2020)