PREPARATION OF NB AL-ALOX/NB JOSEPHSON-JUNCTIONS WITH CRITICAL-CURRENT DENSITIES DOWN TO 1-A/CM(2)/

A new method For preparing Nb/Al-AlOx/Nb Josephson junctions with very low critical current densities is reported. an ultraviolet light assi sted aluminum oxidation process in pure oxygen atmosphere. A better re producibility of the critical current density of the junctions is reac hed in comparison to junctions prepared by the double oxidation techni que. Series arrays of Josephson tunnel junctions with up to 960 juncti ons are produced and tested for Josephson voltage standard application s. The thickness of the aluminum oxide barrier is determined by Ruther ford backscattering spectrometry and is compared with the results of s pecific capacitance measurements. (C) 1998 Elsevier Science B.V.