Aging of Superconducting Y sub 1 Ba sub 2 Cu sub 3 O sub 7--x Structures on Silicon

The long-term stability of epitaxial thin film structures of superconducting Y sub 1 Ba sub 2 Cu sub 3 O sub 7--x on silicon wafers (100), using a yttria-stabilized ZrO sub 2 (YSZ) buffer, is presented and compared to identical structures on SrTiO sub 3 (100) and yttria-stabilized ZrO sub 2 (100) single crystals. For Y sub 1 Ba sub 2 Cu sub 3 O sub 7--y /YSZ/Si heterostructures, the maximum Y sub 1 Ba sub 2 Cu sub 3 O sub 7--y film thickness is limited to 50 nm; otherwise thermal strain induces microcracks. Thinner films are more stable, but nevertheless show aging over several weeks, which affects critical current density and room-temperature resistivity, but not the critical temperature T sub c .