Scanning tunneling microscopy (STM) has been used to investigate the microstructure of DyBa2Cu3O7-x films grown on (100) SrTiO3 by ozone-assisted molecular beam epitaxy. The surface roughness is found to be higher than that reported for sputtered films of YBa2Cu3O7-x. Intensity oscillations were observed in the specular spot of in situ reflection high energy electron diffraction patterns, a result which suggests that surface smoothness is not a requisite for the observation of such intensity oscillations. The observation of spiral morphology in STM pictures indicates the presence of screw dislocations, in excess of 109 cm-2. A zeroth order approximation has been used to evaluate the shapes of the spirals and reasonable agreement is obtained with experiment.