Superconducting properties and chemical composition of NbTiN thin films with different thickness

摘要

In this research, we systematically investigated the superconducting properties and chemical composition of NbTiN thin films prepared on single-crystal MgO substrates. The NbTiN thin films with different thicknesses (4-100nm) were deposited by reactive DC magnetron sputtering at ambient temperature. We measured and analyzed the crystal structure and thickness dependence of the chemical composition using X-ray diffraction and X-ray photoelectron spectroscopy depth profiles. The films exhibited excellent superconducting properties, with a high superconducting critical temperature of 10.1 K, low resistivity (p_(20) = 93 μΩcm), and residual resistivity ratio of 1.12 achieved for 4-nm-thick ultrathin NbTiN films prepared at the deposition current of 2.4 A. The stoi-chiometry and electrical properties of the films varied gradually between the initial and upper layers. A minimum p_(20) of 78 μΩ cm and a maximum residual resistivity ratio of 1.15 were observed for 12-nm-thick films, which significantly differ from the properties of NbN films with the same NaCl structure.