  We report the evolution of superconducting properties as a function of
disorder in homogeneously disordered epitaxial NbN thin films grown on (100)
MgO substrates, studied through a combination of electrical transport, Hall
Effect and tunneling measurements. The thickness of all our films are >50nm
much larger than the coherence length ~5nm. The effective disorder in different
films encompasses a large range, with the Ioffe-Regel parameter varying in the
range kFl~1.38-8.77. Tunneling measurements on films with different disorder
reveals that for films with large disorder the bulk superconducting transition
temperature (Tc) is not associated with a vanishing of the superconducting
energy gap, but rather a large broadening of the superconducting density of
states. Our results provide strong evidence of the loss of superconductivity
via phase-fluctuations in a disordered s-wave superconductor.
