Laser fluence dependence of stoichiometry and superconductivity of iron chalcogenide superconducting films on metal tapes

Abstract

Iron chalcogenide Fe(Se,Te) films with thicknesses of 150 nm were deposited on CeO2-buffered metal tapes via pulsed laser deposition using various laser fluences. The film crystallinity and stoichiometry improved upon increasing the laser fluence. This was explained by the ablation threshold that the superconducting performance was better at higher laser fluences and was attributed to the joint contribution of higher Te contents, better texture, and strengthened in-plane strain. In addition, the pinning mechanism was studied by analyzing the in-field performance characteristics of the Fe(Se,Te) films. The dominant pinning center remained point pinning and was independent of the magnetic field direction and temperature. A collective pinning theory-based analysis showed that the vortex pinning behavior in the Fe(Se,Te) film varied from δl pinning to δTc pinning as the temperature approached the critical temperature. This was related to film superconductivity inhomogeneity, which was driven by unreacted Se and Te atoms.