Growth of thin films FeSe_1-xTe_x with PbO-type structure by pulsed laser deposition method

FeSe_1-xTe_x thin films with a PbO-type structure are successfully grown on MgO(1 0 0) and LaSrAlO₄(0 0 1) substrates from FeSe_0.5Te_0.5 polycrystalline targets by pulsed laser deposition. The film deposited on the MgO substrate (film thickness ∼55 nm) shows superconductivity at 10.6 K (onset) and 9.2 K (zero resistivity). On the other hand, the film deposited on the LaSrAlO₄ substrate (film thickness ∼80 nm) exhibits only the onset of superconducting transition at 3.9 K, but does not show zero resistivity above 2 K. This indicates the strong effect of epitaxial strain on the superconducting properties of FeSe _1-xTe_x thin films.