Properties of n x n square arrays of proximity effect bridges

We have studied the I-V characteristics, the dc resistance at the origin R(T), and the critical current I/sub c/(T) of arrays consisting of n x n(n = 10, 20, 30, and 40) In squares separated by Au/In regions. The superconducting squares have side d/sub s/(In) from 7.5 to 15 μm and d/sub N/(Au/In) from 2.5 to 11 μm. These devices show two transition temperatures in their R(T) curve; one at T/sub c/G near T/sub c/(In) and another one at T/sub c/ above T/sub c/(Au/In). The I-V curves for each temperature region resemble recent puslished results on NbN granular films. These arrays follow a formalism proposed by Wolf, Gubser, and Imry to describe the transition to a resistanceless state at T/sub c/. The measured values of I/sub c/(T) are larger than expected from n noninteracting Bardeen-Johnson junctions in parallel, although the exponential behavior in temperature is followed. They are compatible with the idea of bands in the quasiparticle spectrum in the Au/In regions. Deviations in I/sub c/(T) from an exponential behavior in T near T/sub c/ have been analyzed by appling to SNS arrays ideas developed for phase transitions in SIS arrays. Evidence that at T/sub c/ we may be observing a phase transition at T/sub c/J due to the Josephson coupling between In squares exists but it needs the developement of theoretical work to be put on more solid grounds