Transition properties of a YBa_2Cu_3O_7 nanobridge patterned across a twin boundary of a LaAIO_3 substrate

摘要

We have fabricated superconducting YBa_2Cu_3O_7 (YBCO) nanobridges across twin boundaries of LaAlO_3 (LAO) substrates by using focused-ion-beam etching and studied their critical transport properties. The nanobridges, nominally 150nm in width, 100-120nm in length, and 100 nm in thickness, showed T_C = 91K with ΔT_C ≌ 1K and a high critical current density of J_c ≌ 1.5 × 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.