Nanodots induced columnar growth of YBa2Cu3Ox films

We report columnar growth of YBa2Cu3Ox (YBCO) films by pulsed laser deposition using nanodots of Au, Ag and Pd deposited on SrTiO3 substrate prior to the growth of the film. The nanodots initiate formation of densely packed YBCO columns with c-axis along the length of the columns. The obtained columnar structure offers enhanced pinning of magnetic flux and provides high critical current density in a magnetic field directed along the c-axis of YBCO while keeping high critical current density for other directions of magnetic field. The evidence of columnar structure is given by the planar and cross-sectional atomic force microscopy, transmissional election microscopy and rotational transport measurements of critical current. By creating the columnar structure, an improvement of critical current up to about 200% is achieved comparable to the reference samples without nanodots in a wide range of magnetic field and thickness of the samples. The largest increase in critical current is observed in magnetic fields close to the matching field calculated from the density of nanoparticles or density of YBCO columns.