Formation, properties, and ion irradiation effects of hexagonal structure MoN thin films

Thin films (100-120 nm) of hexagonal structure MoN have been fabricated by reaction of Mo films in an NH3atmosphere. The as-formed films possessed superconducting transition temperatures Tc≃ 13 K, with resistance ratios r = R(296K)/R(Tc) in the range 5 to 10, low-temperature normal state resistivities ρo= 4 to 10 μ Ω-cm, and extrapolated upper critical fields Hc2(0) = 4.0 to 5.0 T. Thin film X-ray diffraction patterns revealed no visible second phase, with measured lattice parameters close to literature values. The effects of lattice disorder on the superconducting and electronic properties were investigated by irradiation with nitrogen ions of energy 45 and 340 keV, resulting in a nearly uniform damage profile without the introduction of any new chemical species. The results indicate that ordered hexagonal MoN shows some of the unusual properties characteristic of moderate-to-high Tctransition metal compounds, but is relatively insensitive to degradation of the superconducting properties by lattice disorder. For ion fluences Φ up to 2 × 10¹⁶N-ions/cm², Tcis found to decrease monotonically and saturate at 9.5 K, almost 3/4 the initial value, while Hc2(0) undergoes a gradual increase to 11T.