Abstract
In order to clarify the best condition for the growth of iron chalcogenide superconductor thin films, we investigated the effect of the substrate on the transport and structural properties of films. Thin films of FeSe0.5Te0.5 grown by pulsed laser deposition were characterized by DC electrical resistivity, Hall effect, X-ray diffraction measurements, and transmission electron microscopy (TEM) observation. The c-axis length of the FeSe0.5Te0.5 thin films revealed a non-systematic change with the cell constants of the substrates. In the films with poor or no superconductivity, we found the occurrence of oxygen penetration to the film and the formation of amorphous layer between the film and the substrate. The origin of the oxygen penetration and the amorphous layer was the chemical properties of substrate. From the chemical viewpoint, LaAlO3 and MgO substrates were confirmed to be appropriate to grow FeSe0.5Te0.5 films.