SUPPRESSION OF THE SPIRAL-GROWTH MECHANISM IN EPITAXIAL YBA2CU3O7-X FILMS GROWN ON MISCUT SUBSTRATES

The growth mechanism and surface microstructures of epitaxial YBa2Cu3O7-x films are extremely sensitive to substrate miscut angle. The screw dislocation-mediated growth that is so prominent in YBa2Cu3O7-x films grown on well-aligned (001) substrates can be completely eliminated by growing YBa2Cu3O7-x on a substrate that is miscut only 2-degrees-3-degrees away from (001). Films grown on miscut near-(001) LaAlO3 and SrTiO3 substrates consist of overlapping tilted platelets, one c-axis unit cell thick, that are epitaxially aligned with the underlying crystal lattice. This morphology, and the absence of screw-growth features, persists even in relatively thick (approximately 200 nm) films. The dominance of miscut-aligned growth is explained by the large number of surface steps that act as both nucleation and rapid-growth sites on a miscut surface.