SIMILARITY OF SCANNING TUNNELING MICROSCOPY AND ATOMIC FORCE MICROSCOPY IMAGES OF YBA2CU3O7 THIN-FILM SPIRAL GROWTH-PATTERNS

The surface morphology of highly oriented c-axis YBa2CuO7 films grown by off-axis sputtering on MgO has been examined by scanning tunneling microscopy (STM) and atomic force microscopy (AFM) at room temperature. Spiral growth patterns were well resolved by both techniques, and the shape of the structures is qualitatively and semiquantitatively similar. The terraces tend to be uneven, with troughs near the steps. The mean height of the steps is close to a multiple of the unit cell, but individual step heights are often not. We conclude that the observed surface topography is not artifactual. The YBa2Cu3O7 appears to be covered by a thin layer (of unknown composition or structure) whose thickness may vary by several A, and whose electrical properties are temperature dependent.