Technology of Ultrathin NbN and NbTiN Films for Superconducting Photodetectors

Abstract

We report fabrication and characterization of ultrathin NbN and NbTiN lms designed for superconducting photodetectors. Our NbN and NbTiN lms were deposited on Al2O3 and Si single-crystal wafers by a high--temperature, reactive magnetron sputtering method and, subsequently, annealed at 1000 C. The best, 18 nm thick NbN lms deposited on sapphire exhibited the critical temperature of 15.0 K and the critical current density as high as 8 10 6 A/cm 2 at 4.8 K.