Metastable structures with composition fluctuation in cuprate superconducting films grown by transient liquid-phase assisted ultra-fast heteroepitaxy

Rare earth-barium-copper oxides superconducting tapes are key candidate materials for high-field magnet applications. The synergetic realization of high-speed growth and high field current carrying capacity of superconducting film is gaining prominence in academics and industry. In this paper, a pulsed laser deposition technique with an ultra-high growth rate two orders of magnitude higher than that of conventional methods (up to 100 nm/s) is engaged to grow nanocomposite EuBa2Cu3O7-delta (EuBCO) superconducting films. Dynamic heating and rapid quenching deposition process make intermediate phases to persist in the EuBCO matrix. As an evidence of the vapor-liquid-solid growth mechanism, a dome-like wetting structure composed of Ba-Cu-O and Eu-rich particles, is observed on the top of the EuBCO layer. In addition, high-density column-like copper-rich meta-stable amorphous structures appear from the EuBCO matrix to the dome-like structure, resulting in a high level of nanostrain and a large number of nanodefects (i.e., oxygen vacancies). The mixture of artificial and natural defects attributes to a pinning behavior dominated by random pinning at which the pinning force exceeds 345 GN/m(3) at low temperature (20 K) and high field (14 T).