Tunneling α2F(ω) from sputtered thin-film NbN

High-quality NbN/oxide/Pb tunnel junctions on sputtered NbN have been fabricated. The 2Δ/k/sub B/T/sub c/ value is 4.25, showing this to be a strong-coupled superconductor. These junctions have satisfactory characteristics for taking derivative measurements. The data were reduced with the use of the modified McMillan-Rowell proximity-gap inversion analysis developed by Arnold and Wolf to generate α2F(ω) and related microscopic parameters for the first time for a B1 compound. The spectra show two main peaks of comparable strength at about 13 and 47 meV (with a shoulder at about 40 meV). The electron-phonon coupling constant lambda = 1.46 +- 0.10, in reasonable agreement with the strong coupling seen in 2Δ/k/sub B/T/sub c/