MEIS analysis of an ion-beam-modified YBCO surface and interface

Ion-beam-bombarded YBa₂Cu₃O₇ (YBCO) surfaces and interfaces have been investigated by using medium energy ion scattering (MEIS) analysis. Ion-beam bombardment and subsequent heat treatment of the YBCO surface have been newly employed to modify the ramp-edge interface of a high-temperature superconducting (HTS) Josephson junction, which is more reliable than an epitaxially deposited barrier interface. However, further study is needed to understand the nature of the ion-beam-modified YBCO surface and interface for the enhancement of the reproducibility of the HTS Josephson junction. The channeling technique along the c-axis of YBCO has been used to observe the damage profile near the surface and the subsurface regions. A noncrystalline damaged layer of about 11 nm in thickness has been found at the surface bombarded with 700 eV argon ions. After the deposition of a thin YBCO layer on the ion-beam-modified surface, which has a role of a counter-electrode in the HTS Josephson junction, the noncrystalline damaged layer is re-crystallized to a stable phase. There is no evidence of dislocations of Ba, Y, and Cu atoms perpendicular to the c-axis at the interface-engineered junction.