Transition properties of a YBa2Cu3O7 nanobridge patterned across a twin boundary of a LaAlO3 substrate

Abstract

We have fabricated superconducting YBa2Cu3O7 (YBCO) nanobridges across twin boundaries of LaAlO3 (LAO) substrates by using focused-ion-beam etching and studied their critical transport properties. The nanobridges, nominally 150 nm in width, 100 - 120 nm in length, and 100 nm in thickness, showed T-c = 91K with Delta T-c congruent to 1 K and a high critical current density of J(c) congruent to 1.5 x 10(7) A/cm(2) at 77 K. Measured current-voltage curves of YBCO nanobridges across the substrate twin boundary showed resistively-shunted-junction characteristics near the transition with an excess current associated with flux flow. High-resolution X-ray diffraction spectra strongly indicated the possibility that the epitaxially-grown YBCO film was also twinned commensurate with twinning of the LAO substrate. Misorientation of the c-axis of YBCO at the twin boundary is believed to create weaknesses that dictate the behavior of the bridge across the twin boundary. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3696977]