Chemical CeO2-based buffer layers for Fe(Se,Te) films

Among other Fe-based superconductors, Fe(Se,Te) is par-ticularly interesting because of the low structural anisotro-py, large upper critical fields, low field dependence of the critical current density and low toxicity. It can also be grown as an epitaxial film on a metallic oriented substrate, making the fabrication of a Fe-based coated conductor (CC) possible. Less strict requirements on the template mi-crostructure allow for the design of a simplified CC, REB-CO layout. This design requires a buffer layer to promote the oriented growth of the superconducting film and avoid diffusion from the metallic template. In this work, CeO2 based buffer layers are prepared on single crystals via two chemical deposition techniques, metal organic decomposi-tion (MOD) and polymer assisted deposition (PAD). With the design of a suitable thermal treatment, it is possible to obtain oriented buffers with large flat grains and low val-ues of surface roughness. Fe(Se,Te) films are deposited on these templates via laser deposition, and excellent samples are obtained when a Fe(Se,Te) seed layer is used to favour chemical matching with the buffer: sharp superconducting transitions around 16 K and critical current densities ex-ceeding 1 MA cm2 at 4.2 K in self-field are observed. These results are the demonstration of the feasibility of a Fe-based CC architecture, with all the relative advantages con-cerning process simplification and cost reduction