The superconducting transition in a million Josephson element snap array

Square arrays of one million Josephson junctions have been fabricated using the Selective Niobium Anodization Process (SNAP). The arrays consist of 2.5 micron square Josephson junctions on a square lattice with a spacing of 29 microns. Clear evidence of a Kosterlitz-Thouless transition has been found in measurements of current-voltage charcteristics and resistance as a function of temperature. Measurements of the resistance vs magnetic field exhibit minima at fields corresponding to both one and one-half of a flux quantum in a fundamental cell.