Enhanced superconducting properties of FeSe0.8Te0.2 thin films grown by pulsed laser deposition

Despite FeSe1-xTex bulk samples with low Te content are difficult to have a single phase due to phase separation, the superconducting epitaxial FeSe0.8Te0.2 thin films with high phase purity and excellent crystallinity are fabricated on CaF2 (001) substrates by pulsed laser deposition. The superconducting properties are studied by complimentary experimental approaches: structural investigation, elemental analysis, and transport measurements. Prepared films with thickness of 150 nm are c-axis oriented with no evidence of impurity phases. In addition, the critical transition temperature T-c is pushed up to 24 K and the upper critical fields are inferred to be improved compared to the most extensively investigated FeSe0.5Te0.5 films. Furthermore, the transport critical current density J(c) reaches values of 5.05 x 10(5) A cm(-2) in self-field at 4.2 K and shows a small anisotropy value of 2.34 at 9 T. Pinning analysis confirms the presence of ab-correlated pinning centers.