Fabrication and measurement of a Nb based superconducting single electron transistor

Abstract
A new four-layer resist system was developed to fabricate small capacitance niobium tunnel junctions. Nb/AlOx/Al junctions were used to make a superconducting single electron transistor composed of two dc SQUIDs in series. The current-voltage characteristics were measured and two types of resonant tunneling of Cooper pairs were observed at different magnetic fields.