Upper Critical Fields of Superconducting NbN Films Deposited by Reactive Sputtering

Abstract

NbN films have been examined with respect to their electrical and superconducting properties. These films were deposited by the dc reactive-sputtering technique under argon gas atmosphere mixed with nitrogen. Critical magnetic fields were measured using a pulse magnet. Upper critical magnetic fields ranging from 150 to 290 kG were observed for these films, and the maximum H_c2about 290 kG is higher by 40 kG than the highest one reported so far for NbN films. These films were able to carry large critical current density of the order of 10⁵ A/cm² in field up to 100kG and had the critical temperatures of 14-16 °K.