In situ growth of epitaxial YBa2Cu3O7 thin films by on-axis unbalanced direct current magnetron sputtering

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Abstract
Superconducting YBa2Cu3O7−x thin films are prepared in situ by on‐axis dc magnetron sputtering from a single stoichiometric target. The magnetron uses an unbalanced magnetic field configuration to eliminate resputtering effects, and high quality thin films on MgO (100) substrates are realized with excellent reproducibility. The target is sputtered in Ar/O2 mixture at a fixed partial pressure ratio pAr/pO2= 15:1. We report on the growth and properties of films deposited (a) as a function of the total sputtering pressure pt (1–100 Pa) at fixed substrate heater temperature Ts=740 °C, and (b) as a function of Ts (600–860 °C) at fixed pt=42 Pa. Epitaxial c‐axis thin films are obtained over a wide range of deposition conditions (Ts≥700 °C, pt≥30 Pa). These films have superconducting transition temperatures Tc=86–90 K, critical current densities Jc77≥106 A cm−2, and resistance ratios R300/R100=2.0–3.1.