Edge geometry superconducting tunnel junctions utilizing an NbN/MgO/NbN thin film structure

摘要

An edge defined geometry is used to produce very small area tunnel junctions (30) in a structure with niobium nitride superconducting electrodes (14, 28) and a magnesium oxide tunnel barrier (24). The incorporation of an MgO tunnel barrier with two NbN electrodes results in improved current-voltage characteristics, and may lead to better junction noise characteristics. The NbN electrodes are preferably sputter- deposited, with the first NbN electrode deposited on an insulating substrate maintained at about 250° to 500° C. for improved quality of the electrode.