The fabrication and characterization of NbCN/AlN heterostructures

Very high quality niobium nitride based superconductor-insulator-superconductor (SIS) junctions have been prepared using aluminium nitride barrier layers deposited by dc reactive magnetron sputtering. These barriers have been shown to grow epitaxially on high quality epitaxial niobium carbonitride (NbCN) base electrodes. High total gap voltages, equal to the maximum that can be expected theoretically, illustrate that there are no degraded layers at the superconductor/insulator interfaces. We have also demonstrated the first SISIS double barrier devices. Transmission electron microscopy has been used to study the growth of a thick AlN layer sandwiched between NbCN and the microstructure of NbCN/AlN multilayers prepared with several different orientation relationships.<>