Growth and characterization of few unit-cell NbN superconducting films on 3C-SiC/Si substrate

Superconducting δ-NbN ultrathin film has become a key element in extremely sensitive detector applications in recent decades because of its excellent electronic properties. We have realized the epitaxial growth of ultrathin δ-NbN films on (100)-oriented 3C-SiC/Si substrates by dc reactive magnetron sputtering at 760 °C with a deposition rate of 0.054 nm s−1. High-resolution transmission electron microscope images confirm the excellent epitaxy of these films. Even with a thickness of 1.3 nm (∼3 unit cells), the δ-NbN film shows a superconducting transition above 8 K. Furthermore, our ultrathin δ-NbN films demonstrate a long Ginzburg-Landau superconducting coherent length ( G L ( 0 ) > 5 nm ) with a critical current density of about 2.2 MA cm−2, and good stability in an ambient environment.