CC BY 4.0 UnportedYuan, FeifeiIida, KazumasaGrinenko, VadimChekhonin, PaulPukenas, AurimasSkrotzki, WernerSakoda, MasahitoNaito, MichioSala, AlbertoPutti, MarinaYamashita, AichiTakano, YoshihikoShi, ZhixiangNielsch, KorneliusHühne, Ruben2017-07-222019-06-282017https://doi.org/10.34657/4799https://oa.tib.eu/renate/handle/123456789/1225Epitaxial Fe(Se,Te) thin films were prepared by pulsed laser deposition on (La0.18Sr0.82)(Al0.59Ta0.41)O3 (LSAT), CaF2-buffered LSAT and bare CaF2 substrates, which exhibit an almost identical in-plane lattice parameter. The composition of all Fe(Se,Te) films were determined to be FeSe0.7Te0.3 by energy dispersive X-ray spectroscopy, irrespective of the substrate. Albeit the lattice parameters of all templates have comparable values, the in-plane lattice parameter of the FeSe0.7Te0.3 films varies significantly. We found that the superconducting transition temperature (Tc) of FeSe0.7Te0.3 thin films is strongly correlated with their a-axis lattice parameter. The highest Tc of over 19 K was observed for the film on bare CaF2 substrate, which is related to unexpectedly large in-plane compressive strain originating mostly from the thermal expansion mismatch between the FeSe0.7Te0.3 film and the substrate.application/pdfenghttps://creativecommons.org/licenses/by/4.0/620Lattice constantsSuperconducting thin filmsBuffer layersSuperconducting transitionsTransmission electron microscopyArticle