Properties of in-Situ Superconducting Y1Ba2Cu3O7-x Films by Molecular Beam Epitaxy with an Activated Oxygen Source
Highly oriented, epitaxial Y1Ba2Cu3O7-x thin films were prepared on MgO(100) by molecular beam epitaxy at a substrate temperature of 550–600°C. 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 X-ray diffraction, and ion channeling. In-situ reflection high energy electron diffraction showed that a layer by layer growth has produced a well ordered, atomically smooth surface in the as-grown tetragonal phase of an oxygen stoichiometry of 6.2–6.3. A 500°C anneal in 1 atm of O2 converted the oxygen content to 6.7 to 6.8. Typical superconducting transport properties of a Y1Ba2Cu3O7-x film 1000Å thick are ρ(300K)= 325 μΩ-cm, ρ(300K)/ρ(100K)= 2.4, Tc(onset) = 92K, and Tc(R=0) = 82K. The transport Jc at 75K is 1×105 A/cm2, and increases to 1×106 A/cm2 at 70K.
KeywordsReflection High Energy Electron Diffraction Oxygen Stoichiometry Volume Recombination High Temperature Annealing Process Effective Area Coverage
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