High Tc Superconducting Thin Films

Abstract

While high Tc superconductivity was first discovered in bulk material, it was apparent that thin films of these materials, particularly the compound YBa2Cu3O7-δ, would be of great interest to both science and technology. In this sense the development of these materials parallels a similar history in the low Tc materials. Initially, most of the low Tc materials of interest were single element metals such as Nb, Pb and Al in bulk form. Later work, mostly in magnets, led to the development of compounds or alloys of such metals as Nb-Sn, Nb-Ti, and many others. However, many physical and technological investigations required thin films with thicknesses in the range of 0.1-10μm. Microwave, infrared, and critical current studies are examples of some of the scientific uses of thin films. A few examples of the applications would include josephson junction-based digital computer circuits, SQUID (Superconducting Quantum Interference Devices), transmission lines, and interconnects and rf mixers. These studies are also of great interest in the high Tc materials. It is readily apparent that scientific and technological developments in superconductivity are closely interwoven.The high level of interest in thin films can be appreciated by observing that it was barely a few months after the announcement of superconductivity above 77 K that the first films of these complex, multi-element materials, superconducting at about 86 K were announced. These early efforts at thin film fabrication were generally accomplished using multi-element deposition techniques but subsequent development has seen many varieties of film fabrication techniques used quite successfully to fabricate high-quality films.