YBa₂Cu₃O_7-δ formation by processing of laser-ablated, fluorine-free precursor films

Epitaxial YBa₂Cu₃O_7-δ (YBCO) was formed by processing of laser-ablated, fluorine-free precursor films. The depositions were conducted at room temperature in low oxygen pressure on LaAlO₃ (LAO) single crystal substrates. Processing was done in the same deposition chamber by heating the precursor film to reaction temperatures of 750-850°C in a reducing gas ambient, and then raising the oxygen pressure to the conversion point. Typical processing times are a few minutes, corresponding to minimum YBCO growth rates of 1 nm/s. XRD analysis shows epitaxial growth and high crystallinity, although measured T_c values are somewhat suppressed at 88 K, with resulting critical current density, J _c of about 1 MA/cm at 77 K, as determined by magnetic hysteresis. Properties indicate that the materials lack appropriate level of defects needed both for rapid oxygenation and flux pinning.