High quality epitaxial FeSe0.5Te0.5 thin films grown on SrTiO3 substrates by pulsed laser deposition

Superconducting epitaxial FeSe0.5Te0.5 thin films are prepared on SrTiO3(001) substrates by pulsed laser deposition. The high purity of the phase, the quality of the growth and the epitaxy are studied with different experimental techniques: x-rays diffraction, reflection high energy electron diffraction, scanning tunneling microscopy and atomic force microscopy. The substrate temperature during the deposition is found to be the main parameter governing sample morphology and superconducting critical temperature. Films obtained under optimal conditions show an epitaxial growth with the c axis perpendicular to the film surface and the a and b axes parallel to the substrate, without evidence of any other orientation. Moreover, such films exhibit a metallic behavior over the whole measured temperature range and the critical temperature is above 17 K, which is higher than the target value.