Niobium nitride/aluminium nitride superconductor/insulator multilayers and tunnel junctions

Niobium nitride/aluminium nitride multilayers have been fabricated using dc reactive magnetron sputter deposition. By careful optimization a suitable set of deposition conditions has been achieved under which both high quality superconducting and insulating layers may be fabricated. This has allowed automation of the deposition process to fabricate multilayers by simple computer control of substrate position and shuttering. Deposition onto a range of single crystal and amorphous substrates has given a range of different crystal structures. We have measured the transport properties of these multilayers as a function of superconductor and insulator layer thickness in order to study the interlayer coupling, and have fabricated stacked superconductor-insulator-superconductor junctions.