Effect of Si-Ion Irradiation on Microwave Surface Resistance in YBa2Cu3Oy Thin Films in Magnetic Fields

Abstract

In this study, we examined the effect of Si-ion irradiation on Rs of YBCO thin films. We measured Rs90 and Rs0 of YBCO thin films in a magnetic field applied both normal and parallel to the film plane. Si-ion irradiation conditions were configured as follows: irradiation energy = 50-500 keV, irradiation ion density = 1-8 × 10 12 ion/ cm2. We found that the Rs90 decreased through ion irradiation, and Si-ion irradiation with an irradiation energy of 200 keV and an irradiated ion density of 4 × 1012 ion/cm2 being the most effective configuration for reducing Rs90 in high magnetic fields. Magnetic field-dependent Rs0 was quite small for all YBCO films with and without ion irradiation. When a magnetic field is applied parallel to the film plane, the blocking layers of the YBCO act as strong pins, therefore, R s0 in the magnetic field is small without introduction of artificial pins. However, we found that the Rs0 of YBCO films became small with Si-ion irradiation than that of the YBCO film without Si-ion irradiation, that the condition of ion energy 200 keV and ion irradiation density 1 × 10 12 ion/cm2 could reduce Rs0 most.