Atom-Resolved Imaging of the Potential Distribution at Si (111) 7× 7 Surfaces

Si (111) 7×7 surfaces were observed at an atomic scale by noncontact atomic force microscopy (ncAFM) and scanning Kelvin probe microscopy (SKPM). A vacancy at the Si surface was resolved by both ncAFM and SKPM. This indicates that SKPM, as well as ncAFM, has a true atomic-scale lateral resolution. In the atom-resolved SKPM observations, two types of image contrast were acquired even when the observation conditions were the same except for the surface condition of a cantilever tip. The result experimentally revealed that the contrast of an atom-resolved SKPM image strongly depended on the surface condition of the probe tip.