Swift heavy ion induced surface modification of YBa2Cu3O7−δ/La0.67Sr0.33MnO3 bilayer superconducting thin films
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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.
The authors are grateful to Inter University Accelerator Center (IUAC), New Delhi for the 15 UD Pelletron facilities. Authors are also grateful to Dr. D. Kanjilal, Director, Inter University Accelerator Center, New Delhi for all the help rendered during irradiation. We acknowledge Prof. T. Som, IOP Bhubaneswar for providing PLD technique for growth of thin film and AFM measurement and P.K Das of North Odisha University, Baripada for providing great support to analyzing the data. I would like to thank S.S Nayak for her support and advice during the work. The author (B. Sahoo) is thankful to DST INSPIRE for providing the financial support to carry out this performance.
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