Localization and pair breaking parameter in superconducting molybdenum nitride thin films

We have investigated the superconductor-insulator transition in molybdenum nitride films prepared by deposition onto MgO substrates. It is indicated that the T _c depression from [Formula: see text] for thick films with increase of the normal state sheet resistance [Formula: see text] was well explained by the Finkel'stein formula from the localization theory. Present analysis suggests that the superconducting-insulator transition occurs at a critical sheet resistance [Formula: see text]. It is found that the [Formula: see text] above [Formula: see text] shows different characteristics of [Formula: see text] and [Formula: see text] in the regions [Formula: see text] and [Formula: see text], respectively, where [Formula: see text] is the classical residual resistance and A is a constant. The excess conductance [Formula: see text] due to thermal fluctuation has been analyzed by the sum of the Aslamazov-Larkin and Maki-Thompson correction terms with use of the pair breaking parameter [Formula: see text] in the latter term. The sum agrees well with the data, although the experimental results of the [Formula: see text] dependence of [Formula: see text], that is, [Formula: see text] shows the disagreement with a linear relation [Formula: see text] derived from the localization theory.