  SupeSuperconducting resonators play a crucial role in developing forthcoming
quantum technologies such as quantum computing or high performance detectors.
Yet, one of their main limitations regarding to noise and sensitivity is the
interaction with two-level systems present in oxide layers in the device.
Focused on mitigating this problem, we study a superconducting device combining
a niobium circuit with a 10 nm gold capping layer. Our investigation covers a
wide range of temperatures and driving powers, revealing that adding the Au
layer reduces the density of two-level system defects while maintaining a very
high quality factor. Moreover, an increase in the non-linearity response is
also observed. Our findings suggest the potential of Nb/Au lumped element
resonators as versatile and promising tools for advancing superconducting
quantum technologies. Among others, the presence of gold allows anchoring alkyl
thiol groups to form self-assembled monolayers, improving the integration with
molecular spin qubits for the development of hybrid quantum processors.
