Swift heavy ion induced surface modification of YBa₂Cu₃O_7−δ/La_0.67Sr_0.33MnO₃ bilayer superconducting thin films

Here, we examined the swift heavy ion (SHI) induced structural modification of YBCO/LSMO bilayer thin films deposited through pulse laser deposition technique. The films were irradiated by 200 MeV Ag ions with the fluence of 5 × 10¹² ions/cm². Swift heavy ion irradiation causes grain fragmentation leading to the formation of nanograin has been discussed. FESEM and AFM were carried out for surface morphology analysis before and after irradiation of the thin films. FESEM micrographs give confirmation about the fragmentation of larger grains into the smaller grains due to irradiation effect. The degree of the grain fragmentation has been initiated to be increased for bilayer structures. Atomic force microscopy (AFM) analysis also agrees well with the fragmentation due to irradiation. For higher fluence ~ 5 × 10¹² ions/cm² the reduction of grain size with the evolution of cracks has been observed. Power spectral density (PSD) analyses have been carried out to explain the AFM data followed by the fractal model and K-correlation model. XRD analysis gives confirmation about highly improved c-axis oriented growth of all thin films. Utilizing the Williamson–Hall plot on XRD data, the strain and dislocation density was estimated for all the films. The strain and dislocation density increases with the addition of ferromagnetic LSMO.