In situ epitaxial growth of Y1Ba2Cu3O 7-x films by molecular beam epitaxy with an activated oxygen source

Abstract

Highly oriented, epitaxial Y1Ba2Cu3O 7-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 an Y1Ba2Cu3O7-x film 1000 Å thick are ρ(300 K)=325 μΩ cm, ρ(300 K)/ρ(100 K)=2.4, Tc(onset)=92 K, and Tc(R=0)=82 K. The transport J c at 75 K is 1×105 A/cm2, and increases to 1×106 A/cm2 at 70 K.