YBa2Cu3O7-δ Formation by Processing of Laser-Ablated, Fluorine-Free Precursor Films

Epitaxial YBa₂Cu₃O_7-delta 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 750-850degC 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/cm₂ 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.