JOSEPHSON-JUNCTIONS AND SQUID AT HIGH CRI TICAL-TEMPERATURES - STATE-OF-THE-ART AND APPLICATIONS

The paper gives an overview of technological methods devoted to high c ritical temperature Josephson Junctions. Two families of junctions are presented : Junctions with intrinsic Josephson barrier (grain boundar y) and Junctions with extrinsic Josephson barrier (normal or insulatin g layer). The first part of the paper ends by depicting a simple appli cation of Josephson Junctions : the Josephson-Fraunhofer magnetometer. The second part of thepaper in devoted to high Tc dc SQUID and their applications. Classical methods to reduce the low frequency noise of t he dc SQUID are summarized and techniques to apply the magnetic field are discussed, especially the directly coupled one, which leads to a s imple single layer processing. The latter avoids technological problem s associated to multilayered structures such that via and cross-over. Finally, a state of the art of performances is given which shows the a bility of SQUID to be applied in Non Destructive Testing, geophysics, under sea communications and biomagnetism.