I n s i t u epitaxial growth of Y1Ba2Cu3O7−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 Y₁Ba₂Cu₃O_7−x film 1000 Å thick are ρ(300 K)=325 μΩ cm, ρ(300 K)/ρ(100 K)=2.4, T_c(onset)=92 K, and T_c(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.