Superconducting niobium nitride thin films deposited by metal organic plasma-enhanced atomic layer deposition

Superconducting NbN¬x thin films were deposited by plasma enhanced-atomic layer deposition (PE-ALD) using the metal organic precursor (tert-butylimido)-tris (diethylamino)-niobium (TBTDEN) and hydrogen plasma. The transition temperature TC and the resistivity of the NbN-thin films were measured by four-point probe measurement. Their composition was analyzed by x-ray diffraction and Rutherford backscattering spectroscopy. The deposition process was optimized to obtain a low resistivity as well as a high superconducting transition temperature. A TC close to 10 K and a resistivity of 2.5 µΩm as well as a critical current density of 8.9 * 105 A/cm² were achieved. Originally, a high oxygen concentration was detected in the compound. By variation of the plasma parameters, the concentration could be reduced from 57 atom (at.) % to 11 at. %. Because of the excellent thickness control and conformality, such ALD films may be suited very well for applications in superconductor electronics and sensing devices.