Epitaxial growth of LaFeAs(O,F) thin films by molecular beam epitaxy

LaFeAs(O,F) epitaxial thin films were grown on GaAs substrates by molecular beam epitaxy. Two films were grown with different growth time. The film grown for 1 h was single phase, but did not show a superconducting transition because of the absence of doped fluorine. On the other hand, the film grown for 6 h contained LaOF as an impurity, but showed a clear superconducting transition without the need of an ex situ heat treatment. The results of Hall coefficient and lattice constant measurements suggest that the superconducting film was sufficiently doped with fluorine although the transition temperature (T(c)) was rather low, implying that a further improvement in the film quality would increase T(c). (C) 2011 Elsevier B.V. All rights reserved.