Evaluation of systems 1 and 2

Following the WP15 program two superconducting systems (Nb3Sn as System 1 and NbN as System 2) were studied in a single layer in terms of deposition parameters (substrate material and surface preparation, temperature, base and deposition partial pressure of reactive (N2) and nonreactive (Ar and Kr)), film characterisation (structure and composition) and DC superconducting properties. It has been shown that System 1 (Nb3Sn) can be successfully deposited from an alloy target and demonstrate good SC properties when it is deposited at high temperature (around 550-
650 °C).
System 2 (NbN) can be produced from an Nb metal target by reactive sputtering in N2 rich atmosphere. A few SIS structures have been investigated using Nb as a base layer followed by AlN and Nb3Sn as insulating and superconducting screening layer. For a practicality of SIS structure deposition, the screening layer materials should be one containing nitrogen such as NbN and NbTiN, especially when insulation layer is AlN.

The finding should be finally applied to QPR samples and tested at RF conditions as a part of WP15 programme in the following years.