Effect of BSO addition on Cu-O bond of GdBa2Cu3O7-xfilms with varying thickness probed by extended x-ray absorption fine structure

We investigated the relation between the Cu-O bond length and the superconducting properties of BaSnO₃ (BSO)-added GdBa₂Cu₃O₇₋ₓ (GdBCO) thin films by using extended x-ray absorption fine structure (EXAFS) spectroscopy. 4 wt.% BaSnO₃ (BSO) added GdBa₂Cu₃O₇₋ₓ (GdBCO) thin films with varying thickness from 0.2μm to 1.0μm were fabricated by using pulsed laser deposition (PLD) method. The transition temperature ( Tc ) and the residual resistance ratio (RRR) of the GdBCO films increased with increasing thickness up to 0.8μm , where the crystalline BSO has the highest peak intensity, and then decreased. This uncommon behaviors of Tc and RRR are likely to be created by the addition of BSO, which may change the ordering of GdBCO atomic bonds. Analysis from the Cu K-edge EXAFS spectroscopy showed an interesting thickness dependence of ordering behavior of BSO-added GdBCO films. It is noticeable that the ordering of Cu-O bond and the transition temperature are found to show opposite behaviors in the thickness dependence. Based on these results, the growth of BSO seemingly have evident effect on the alteration of the local structure of GdBCO film.