Deposition of superconducting Ba₂Ca_n-1Cu_nO_2n(O,F)₂thin films by pulsed laser ablation

Abstract

The highest ever superconducting critical temperature (Tc) of 120 K has been reported for the compound Ba2Can-1CunO2n(O,F)2 (F-02(n-1)n). However, only bulk samples have been synthesized to date and extremely high pressures have been required. Here, the deposition of superconducting Ba2Can-1CunO2n(O,F)2 films on a SrTiO3(100) substrate was investigated using Nd-YAG pulsed laser ablation under an O2 pressure of 16-19 Pa at a substrate temperature of 740-750 °C. The films exhibited a superconducting onset temperature (Tco) of 76.5 K and a zero resistance temperature (Tce) of 22.5 K. The dominant diffraction peaks matched those reported for c-axis oriented Ba2Ca2Cu2O6(O,F)2 (n = 3) bulk samples. However, the Tc values for the films were much lower than that for the bulk material, even though the ablation target composition was Ba2Ca2Cu3O6+δ(O,F)2, which yields the highest bulk Tc value.