Observation of growth-mode change under a magnetic field in YBa₂Cu₃O_7-x

YBa₂Cu₃O_7-x (YBCO) films were grown on metallic substrates by a metalorganic chemical vapor deposition process in high magnetic fields. We used a combination of scanning electron microscopy (SEM), atomic force microscopy (AFM), x-ray diffraction, and transport-property measurements. By imaging the as-grown surfaces of YBCO films with high-resolution SEM and AFM, we have directly observed the growth-mode change from the spiral growth mode at zero field to the two-dimensional or (3D) island growth mode under an external magnetic field. The surface structures observed provide insight into the mechanism of crystal growth operative during the formation of YBCO films grown using the our field-assisted chemical vapor deposition technique. The possible mechanism of the film growth under the influence of a magnetic field is also analyzed.