1 V and 10 V SNS Programmable Voltage Standards for 70 GHz

Abstract

Programmable Josephson voltage standards (PJVSs) in combination with fast switchable DC current sources have opened up new applications in the field of low-frequency AC metrology. The growing interest in output voltages of up to plusmn10 V initiated efforts by several National Metrological Institutes to realize 10 V PJVSs. Presently, only 10 V PJVSs from PTB based on SINIS junctions have been successfully incorporated into existing setups for AC metrology. However, the fabrication of 10 V SINIS arrays that are driven at 70 GHz suffers from very low yield. The recent technological progress made at NIST enabled the drop-in replacement of the low-yield SINIS arrays by more robust SNS arrays. The N-material is an amorphous Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> alloy near the metal-insulator transition and is deposited by co-sputtering. For the first time, fully operational 1 V and 10 V PJVSs with SNS junctions that are suitable for a 70 GHz drive have been fabricated and tested. This work was done in close cooperation between NIST and PTB.