Surface and interface analyses of UHV evaporated Nb/AlOx/Nb tri-layers

We have prepared Nb thin films with e-beam evaporation under UHV conditions . Al thin films were deposited by resistive heating in the UHV chamber. The preparation of these films and the tri-layers of Nb/AlOx/Nb were intended for their use in Josephson junctions. The surface studies of these films we re undertaken by using scanning electron microscope and atomic force micros cope in the non-contact mode, whilst the interface analysis was carried out by depth profiling using scanning Auger microprobe. These studies have rev ealed that Nb films grown on AlOx are smoother than the ones grown on Si. F urther, it is seen that Al diffuses into Nb on both sides and that the inte rface is very broad. This intermixing of various materials results in the f ailure of the tri-layers when subjected to application in SQUIDs.