High Tc superconducting thin films: fabrication and electronic applications

Summary form only given. Many techniques have been utilized to produce high-quality, high-T_c superconducting films. These techniques include laser ablation, a variety of sputtering techniques, and electron beam vapor deposition. Molecular beam epitaxy (MBE), chemical vapor deposition (CVD), liquid-phase epitaxy (LPE), and resistance heating of the source materials are also being studied. These methods of film preparation have been applied to the three main classes of high T_c materials, i.e. YBa₂Cu₃ O_7-y (YBCO) and Tl-based and Bi-based films. The maximum supercurrent that these films can sustain appears to depend strongly on the fabrication parameters, and in general the highest values are obtained for epitaxial films of YBCO on polished, single-crystal, (100)-oriented substrates of SrTiO₃. Thin-film applications involving circuits and devices will require lithographic patterning and superconducting materials that do not deteriorate as a result of the processing used. Superconducting, thin-film devices such as superconducting quantum interference devices (SQUIDs) have been developed from the high-T_c materials. An attempt has also been made to fabricate junction-type devices, and such efforts required extending the technology to multilevel processing, adding many steps to the fabrication. The fabrication of multilevel, edge junction SQUIDs is also discussed