Structural and electrical properties of YBa2Cu3O7 []-tilt grain boundary Josephson junctions with large IcRn-products on SrTiO3 bicrystals

• Published in: Physica. C, Superconductivity Superconductivity, 2002-08, Vol.372-376, p.115-118
• Main Authors: Divin, Y.Y., Poppe, U., Jia, C.L., Shadrin, P.M., Urban, K.
• Format: Article
• Language: English
• ISSN: 0921-4534
• DOI: 10.1016/S0921-4534(02)00859-6

The microstructure of 2x12 infinity [100]-tilt grain boundary Josephson junctions was investigated by AFM and cross-sectional TEM. The junctions were prepared by depositing about 100 nm thick epitaxial YBa2Cu3O7 films on the vicinal bicrystal substrates of SrTiO3 with high pressure O sputtering and showed a 2x12 infinity tilt of the YBa2Cu3O7 c-axis toward the grain boundary. The film grain boundary was straight and followed the bicrystal substrate boundary. It showed a low degree of meandering in comparison to the behavior of conventional [001]-tilt grain boundaries. Due to step bunching, the film surface exhibited a profile of 12 degree inclined terraces with a valley depth of 5-20 nm, and at the grain boundary a straight V-shaped surface suppression of about 40 nm depth was observed. The fact that the IcRn-products of such Josephson junctions showed high values of up to 1.2 mV at 77 K and up to 8 mV at 4.2 K as well as a smaller scattering of the values for Ic and Rn in comparison to [001]-tilt grain boundaries is attributed to the microstructure. The junctions showed clear Shapiro steps as a response to 94 GHz microwave radiation. 5 refs.