Modification of YBa2Cu3Oy Thin Films by Exposure to Argon Plasma and Ozone: A Structural Study

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The effects of argon plasma bombardment and subsequent heat treatments on the structure of YBa2Cu3O y thin films were studied. We find that the argon plasma processing modifies the yttrium composition through the formation of Y2O3 islands (serving as an yttrium reservoir) and solid-state diffusion. The scanning electron microscopy (SEM) images show that the argon plasma bombardment accelerates the growth of Y2O3 islands which are thinned and washed away during the subsequent annealing in vacuum. Complimentary techniques (X-ray diffraction and X-ray absorption spectroscopy) show that the structural disorder caused by argon plasma processing is recovered by heat treatment in vacuum while oxygen vacancies are compensated by the final ozone treatment. The results reveal the individual roles of sequential treatments of YBa2Cu3O y thin films which improve the electrical properties of ramp-edge Josephson junctions.