Characterization of NbTiN Thin Films Deposited on Various Substrates

Niobium titanium nitride (NbTiN) thin films were deposited on a selection of different substrates to explore the optimum depositing condition of high-quality NbTiN thin films. The NbTiN films deposited on MgO, Al<sub>2</sub>O<sub>3</sub>, and fused quartz substrates showed excellent superconducting properties with a high <i>T</i><sub>C</sub> of 14.7 K, 14.5 K, 15.2 K, and low resistivity ρ<sub>20 K</sub> of 55 μΩcm, 116 μΩcm, 78 μΩcm, respectively. The chemical composition, crystal structure, and relationship between superconducting properties and crystal structure were systematically investigated by changing the N<sub>2</sub>/(Ar+N<sub>2</sub>) ratio in sputtering gases. The lattice parameter systematically changed as N<sub>2</sub>/(Ar+N<sub>2</sub>) ratio was varied. We found that the superconducting properties depend on the lattice parameter, and the film with the best superconducting properties had a lattice parameter of 4.380 Å (on MgO), 4.345 Å (on Al<sub>2</sub>O<sub>3</sub>), 4.335 Å (on fused quartz).

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