Superconducting properties of FeSe1−xTex films with x=0−0.4

We investigate superconducting properties of FeSe1−xTex films with x=0−0.4, which are around the optimal Te contents, on CaF2 substrates. From the results of electrical resistivity measurements, the values of Tc in films with x=0.3,0.4 are about 22 K. These values are very close to that of the film with x=0.2 which was reported to be the optimal composition in FeSe1−xTex films on CaF2 substrates. In addition, a sudden suppression of Tc is observed in very narrow region, that is, 0.1 < x < 0.15. This behavior is different from the dome-shaped phase diagram that is familiar in iron-based superconductors.