In-situ Epitaxial Growth of Y sub 1 Ba sub 2 Cu sub 3 O sub (7-x) Films by Molecular Beam Epitaxy with an Activated Oxygen Source.

Highly oriented, epitaxial Y sub 1 Ba sub 2 Cu sub 3 O sub (7-x) thin films were prepared on MgO(100) by molecular beam epitaxy at a substrate temperature of 550C. The in-situ growth was achieved by incorporating reactive oxygen species produced by a remote microwave plasma in a flow-tube reactor. The epitaxial (001) orientation is demonstrated by in-situ reflection high energy electron diffraction, X-ray diffraction, and ion channeling. The oxygen stoichiometry increases from 6.2-6.3 in as-deposited film to 6.7-6.8 after a 550C anneal in 1 atm O sub 2. The resistivity, rho(300K), of a Y sub 1 Ba sub 2 Cu sub 3 O sub (7-x) film 1000angstroms thick is 380 mu OMEGA-cm, and the superconducting transition is T sub c (onset) = 92K, and T sub c (R=0) = 82K.