CHARACTERIZATION OF NIOBIUM NITRIDE THIN-FILMS PREPARED BY ION-ASSISTED DEPOSITION

The superconductivity of NbN thin films of nearly stoichiometric composition has been investigated, specifically comparing the properties of samples obtained by r.f. reactive magnetron sputtering with those of films prepared by deposition of niobium assisted by a nitrogen ion beam. Both kinds of samples were crystalline, single phase, f.c.c. (B1), as shown by X-ray diffractometry. Auger electron spectroscopy indicates that compound composition is near the ideal stoichiometry, the main difference being the content of gaseous contaminants, which appears easier to control by ion-beam-assisted deposition. The superconducting critical temperature T(c) (7.1 K), the transition width DELTA-T(c) (0.1 K) and the slope dR/dT (910-omega-K-1) of the resistance vs. temperature curve in the transition region have been resistively determined. The results are compared with those reported for NbN films obtained by other techniques.