This technology provides a process for coating high-temperature superconductor materials with a thin, oxide coating that serves to prevent their degradation via ambient oxygen, temperature, or moisture conditions. This coating also enables formation of improved high-Tc tunnel junctions and could possibly improve on present efforts to fabricate Josephson tunnel junctions based on high Tc and other non-metallic superconductors. This achievement could provide extensive technological advances in electronic computer circuitry.
• How it Works
Ultrathin oxide films are created by first condensing a hydroxylated metal oxide superconductor surface (e.g., YBa2Cu3O7, YBCO) with an extremely pure, highly reactive metal oxide (e.g., n-propyl orthozirconate) and then hydrolyzing the resulting surface. The condensation-hydrolysis process is repeated until films with the desired properties are achieved.
Increasing the molecular density on the surface of YBCO potentially forms a robust zirconium oxide (ZrO) tunneling barrier, and tunnel junctions can be fabricated, a phenomenon that illustrates the insulating, ultrathin, and pinhole-free nature of the oxide films.
• Why It Is Better
Previous techniques for reliably fabricating tunnel junctions cause significant damage to the surface of the high-Tc superconductor. Most successful techniques are based on evaporation of reactive metals on the surface of YBCO and rely on a highly invasive chemical interaction between the YBCO and the metal overlayer, which necessarily disorders the surface of YBCO.
Since this novel technology involves a significantly gentler chemical interaction, presumably reacting with surface oxide species only, it enables greater selection of materials for use and does not result in damage to the superconductor surface.
Its existence as a coating provides an impervious barrier to ambient conditions, allowing greater freedom in storage and use and eliminating costs associated with strict environmental control measures.
Tunnel junctions achieved with this novel technology provide high device quality; the electronic structure of such high-Tc superconductors is extremely sharp and detailed.