Epitaxial Fe-Te-S thin films (thickness range 100-200 nm) were deposited by pulsed laser deposition at 400 • C on SrTiO 3 (100) and MgO(100) single-crystal substrates. The films reached the zero-resistance condition: T 0 c = 3.54 K for on SrTiO 3 and 5.37 K for on MgO, and presented a large upper critical field: B c2 (0) = 61.1 T for on SrTiO 3 and 74.2 T for on MgO, using 90% of the normal state resistance and the Werthamer-Helfand-Hohenberg model. The coherence length ξ 0 is very short: 2.30 nm for on SrTiO 3 and 2.10 nm for on MgO. The film grown on MgO showed B c2⊥ (0) = 80.73 T; then the isotropic parameter γ is 1.09. The best J c observed is 10 4 A cm −2 (at 2 K, self-field) for the sample deposited on MgO.

We report on the fabrication of Fe–Te–S epitaxial thin films on SrTiO3(100) and MgO(100) single crystal substrates by pulsed laser deposition. Crystal structure was checked by X-ray diffraction, composition by scanning electron microscopy and energy dispersive spectroscopy (SEM–EDS), and superconductivity by resistance measurements. All the films deposited in the temperature range 300–400 °C were grown epitaxially on both substrates with a 4-fold symmetry. A zero resistance condition was not reached, but even if the films present a stoichiometric excess of Fe there is a clear upturn at 6 K.

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