Critical current densities in superconducting granular Al-Al-20-3films

This paper reports measurements of the critical current densities on thin granular superconducting Al-Al-20-3 films as a function of the normal state resistivity of the granular material and as a function of temperature. It is observed that the Al-Al-20-3 films exhibit critical current densities of 10²A/cm²to 10³A/cm²over a broad range of normal state resistivities ranging from 30 μΩcm to 3000 μΩcm; the critical current density is inversely proportional, approximately, to the square root of the normal state resistivity, and in most cases, is directly proportional to (1 - T/Tc). SQUID quantum devices having very large widths of 10 μm to 25 μm have been prepared from these very low critical current films.