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ST300 - Generic Buffer Layers for Fe-based Superconductors: Epitaxial FeTe1-xSex Thin Films

Generic Buffer Layers for Fe-based Superconductors:
Epitaxial FeTe1-xSex Thin Films

K. Iida1, J. Hänisch1, E. Reich1, F. Kurth1, L. Schultz1, B. Holzapfel1, M. Schulze1,
S. Aswartham2, S. Haindl2, S. Wurmehl2, B. Büchner2,
S. Takeda3, S. Ueda3, M. Naito3, C. Tarantini4, J. Jaroszynski4

1Institute for Metallic Materials, IFW Dresden
2Institute for Solid State Research, IFW Dresden, 01069 Germany
3Tokyo University of Agriculture &Technology, Tokyo 184-8588, Japan
4 National High Magnetic Field Laboratory, FL 32310, USA

Abstract - Iron chalcogenide superconductors are very sensitive to strain. Hence the superconducting transition temperature, Tc, of FeTe1-xSex films can be tuned by strain and even higher Tc values can be realized in films than in bulk material. The biaxial strain is usually induced by a lattice mismatch between film and substrate. However, the correlation between Tc and lattice mismatch for FeTe1-xSex is controversial. A fundamental problem is the formation of an interfacial layer between FeTe1-xSex and oxide substrates, which compromises the epitaxial growth. Therefore, we proposed the implementation of a Fe buffer layer to grow epitaxial FeTe1-xSex thin films. Similar to the Ba-122/Fe bilayers, 1) epitaxial
FeTe1-xSex films with sharp out-of-plane and in-plane texture have been realized on Fe-buffered single crystalline MgO substrates. 2) The clean interface between Fe and FeTe1-xSex has been also confirmed by transmission electron microscopy. These results indicate that Fe can work as generic buffer layer for epitaxial growth of Fe-based superconductors. The FeTe1-xSex/Fe bilayer with a high Tc of 19 K showed strong intrinsic pinning from correlated ab-planes, since the Se(Te)-Se(Te) interlayer distance is almost identical to the out-of-plane coherence length at low temperatures. This work is partially supported by DFG. Project, No. BE 1749/13 and HA 5934/3-1. We also acknowledge the EU (IRON-SEA and SUPERIRON) under project No. FP7-283141 and FP7-283204. A portion of this work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement No. DMR-0654118, the State of Florida, and the U.S. Department of Energy.

Keywords – Fe-based superconductors, FeTe1-xSex, thin film, epitaxy, buffer layer, iron buffer.

[1] T. Thersleff et al., Appl. Phys. Lett. 97, 022506 (2010).
[2] K. Iida et al., Appl. Phys. Lett. 99, 202503 (2011).

IEEE/CSC & ESAS European Superconductivity News Forum (ESNF) No. 22 October/November 2012.  ESNF Reference No.STP300 Categories 2, 5.
This is an invited ASC 2012 presentation 4LF-01 not submitted to IEEE Trans. Appl. Supercond. (2013) for possible publication.