High-T_c superconducting thin film from bismuth cuprate nano-colloids

With the colloidal suspension of superconducting nanoparticles as a precursor, we have successfully fabricated well-oriented high-T_c superconducting Bi₂Sr₂CaCu₂O_y films by an electrophoretic deposition method. The colloidal suspension of superconducting nanoparticles can be prepared by the exfoliation of Bi-based cuprates through the intercalation of long chain organic molecules. According to zeta potential measurement, the surface of the resulting nanosheets in an acetone solvent is positively charged with a potential of + 25 mV. Such a presence of surface charge allows us to apply the electrophoretic deposition process with a silver metal substrate. A post-annealing process for the as-deposited film improves significantly the electrical connectivity and the c-axis alignment of the superconductor grains. The thickness of the resulting films can be easily tuned by the control of deposition conditions such as an applied electrical potential and a deposition time.