Deposition and properties of Fe(Se,Te) thin films on vicinal CaF2 substrates

• Published in: Superconductor science & technology 2017-10, Vol.30 (11)
• Main Authors: Bryja, Hagen, Hühne, Ruben, Iida, Kazumasa, Molatta, Sebastian, Sala, Alberto, Putti, Marina, Schultz, Ludwig, Nielsch, Kornelius, Hänisch, Jens
• Format: Article
• Language: English
• Subjects: anisotropy; critical current density; thin films; vicinal substrates
• ISSN: 0953-2048; 1361-6668
• DOI: 10.1088/1361-6668/aa8421

We report on the growth of epitaxial Fe1+δSe0.5Te0.5 thin films on 0°, 5°, 10°, 15° and 20° vicinal cut CaF2 single crystals by pulsed laser deposition. In situ electron and ex situ x-ray diffraction studies reveal a tilted growth of the Fe1+δSe0.5Te0.5 films, whereby under optimized deposition conditions the c-axis alignment coincides with the substrate [001] tilted axis up to a vicinal angle of 10°. Atomic force microscopy shows a flat island growth for all films. From resistivity measurements in longitudinal and transversal directions, the ab- and c-axis components of resistivity are derived and the mass anisotropy parameter is determined. Analysis of the critical current density indicates that no effective c-axis correlated defects are generated by vicinal growth, and pinning by normal point core defects dominates. However, for H ab the effective pinning centers change from surface defects to point core defects near the superconducting transition due to the vicinal cut. Furthermore, we show in angular-dependent critical current density data a shift of the ab-planes maxima position with the magnetic field strength.