A low power 10 V programmable array based on Nb x Si1−x Josephson junctions for metrology applications
in: Superconductor Science & Technology (2016) 095015-1
Josephson junctions generate, when subjected to microwave irradiation, voltages with a veryhigh precision and are used in metrology applications. So-called PJVS (programmableJosephson voltage-standards) are capable of generating both AC and DC voltages of up to 10 V.Our work addresses a full fabrication scenario for 10 V PJVS arrays driven at 70 GHz to be usedin low microwave-power conditions as in, but not limited to GUNN diodes or cryocoolerapplications. NbxSi1−x in its function as a barrier material was characterised with AFM, RBSand reflectometry in order to establish a reliable technological foundation. A 10 V PJVS arraydriven with microwave power below 50mW is further presented, which was achieved byoptimising the fabrication technology regarding the degree of homogeneity of the Josephsonjunctions composition and thickness. Control over these parameters is crucial in choosing astable and well-suited characteristic voltage (IcRnproduct) and critical current density jc. Withthis, a low-power operation of a PJVS array is possible without the need for liquid heliumcooling, which is currently limiting the availability of PJVS based metrology.