High T_c superconducting thin films: Fabrication and electronic applications

Abstract

Summary form only given. Many techniques have been utilized to produce high-quality, high-Tc 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 Tc materials, i.e., YBa2Cu3O7-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-Tc 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.