Radiation effects in superconducting NbN/AlN multilayer films

The results of neutron irradiation up to a fluence of 1023 m−2 (E>0.1 MeV) are reported for sputtered NbN/AlN multilayer films. The superconducting properties change only slightly with neutron fluence. For the best multilayers, which exhibit critical current densities Jc of >108 A/m2 at 4.2 K and 20 T, the high-field data show virtually no change in Jc. It is therefore proved experimentally that NbN/AlN multilayers, which exhibit higher Jc than single NbN thin films, exhibit the same extremely radiation-hard, high-field behavior which was reported previously for such NbN films.