Xenon ion irradiation of superconducting YBa₂Cu₃O₇ thin films

Abstract

Recently it was reported that the critical current density(J c ) of YBa 2 Cu 2 O 7 , in the presence of magnetic field, is enhanced by ion irradiation. The enhancement is thought to be due to the pinning of the magnetic flux lines by radiation-induced defects or by structural disorder. The aim of the present study was to understand the fundamental mechanisms of the defect formation in association with the pinning effect in YBa 2 Cu 3 O 7 by means of high-resolution electron microscopy(HRTEM). The YBa 2 Cu 3 O 7 specimens were prepared by laser ablation in an insitu process. During deposition, a substrate temperature and oxygen atmosphere were kept at about 1073 K and 0.4 mbar, respectively. In this way high quality epitaxially films can be obtained with the caxis parallel to the <100 > SrTiO 3 substrate normal. The specimens were irradiated at a temperature of 77 K with 173 MeV Xe ions up to a dose of 3.0 × 10 16 m −2 .