Room temperature reactive sputtering deposition of titanium nitride with high sheet kinetic inductance

Abstract

Superconducting thin films with high intrinsic kinetic inductance $L_k$ are important for high-sensitivity detectors, enabling strong coupling in hybrid quantum systems, and enhancing nonlinearities in quantum devices. We report the room-temperature reactive sputtering of titanium nitride thin films with a critical temperature $T_c$ of \SI{3.8}{K} and a thickness of \SI{27}{nm}. Fabricated into resonators, these films exhibit a sheet kinetic inductance $L_{k,\square }$ of 394~$\text{pH}/\square$, as inferred from resonant frequency measurements. %from this film and measure quality factors of $4\times 10^4$; these quality factors are likely limited by the low resistivity wafer. X-ray diffraction analysis confirms the formation of stoichiometric TiN, with no residual unreacted titanium. The films also demonstrate a characteristic sheet resistivity of 475~$\Omega /\square$, yielding an impedance an order of magnitude higher than conventional 50~$\Omega$ resonators. This property could enhance microwave single\textendash photon coupling strength by an order of magnitude, offering transformative potential for hybrid quantum systems and quantum sensing. Furthermore, the high $L_k$ enables Kerr nonlinearities comparable to state\textendash of\textendash the\textendash art quantum devices. Combined with its relatively high $T_c$, this thin film presents a promising platform for superconducting devices, including amplifiers and qubits operating at higher temperatures.