INSULATING NANOPARTICLES ON YBA2CU3O7-DELTA THIN-FILMS REVEALED BY COMPARISON OF ATOMIC-FORCE AND SCANNING-TUNNELING-MICROSCOPY

The surface topography of YBa2Cu3O7-delta thin films has been studied with both atomic force microscopy (AFM) and scanning tunneling microsc opy (STM). The AFM images reveal a high density of small distinct nano particles, 10-50 nm across and 5-20 nm high, which do not appear in ST M images of the same samples. In addition, we have shown that scanning the STM tip across the surface breaks off these particles and moves t hem to the edge of the scanned area, where they can later be imaged wi th the AFM.