Screw dislocation mediated growth of sputtered and laser-ablated YBa₂Cu₃O_7-δ films

By imaging the as-grown surfaces of sputtered and laserablated YBa2Cu3O7-δ films with scanning tunneling microscopy (STM), we have directly observed spiral-shaped growth terraces which emanate from screw dislocations. The density of screw dislocations was observed to decrease with increasing growth temperature and substrate misorientation. The surface structures observed by STM together with cross-sectional transmission electron microscope (TEM) images provide insights into the mechanisms of crystal growth operative during the formation of YBa2Cu3O7-δ films grown using these two widespread techniques. © 1992 Springer-Verlag.