Abstract
Tunnel junctions made with NbN base electrodes and Pb counterelectrodes are investigated and characterized in terms of their potential for high-performance digital Josephson circuits. The NbN is deposited by dc magnetron reactive sputtering onto substrates which are held near room temperature (T /SUB s/ < 90/sup 0/C) to assure compatibility with conventional photoresist liftoff; the process results in films with a T /SUB c/ of 14.2K and an energy gap parameter ..delta.. /SUB NbN/ = 2.4meV. Tunnel junctions are formed by ion cleaning and reactive ion beam oxidation, and typically have low leakage and no excess conduction above the sum of the gaps. The effective penetration depth of NbN/Nb bilayers is shown to be small, while the specific capacitance of the junctions is comparable to that of Nb base-electrode junctions.
Published Version
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