Force Microscopy Imaging of Rest Atom on Si(111)7×7 Surface under Strong Tip–Surface Interaction

We investigated NC-AFM imaging mechanism on a Si(111)7×7 surface under the strong interaction condition working between dangling bonds on the tip and the surface atoms. The surface adatom appeared in the image as a bright spot, which became larger with stronger interaction condition. Upon further strong interaction, we could detect the rest atoms in the unfaulted half unit of the 7×7 surface image as prominent sharp bright dots with 1 Å width. Besides, the dot appeared with the lateral shift by 2 Å as compared to the surface adatom image. We found the strong covalent interaction between the dangling bonds on the tip atom and the surface atoms influenced onto the image variation.