EFFECT OF THE TIP STRUCTURE ON ATOMIC-FORCE MICROSCOPY

Theoretical simulation of atomic-force microscope (Arm) images is performed with a model of a single-atom tip or two kinds of multiple-atom diamond tips scanned on a graphite substrate surface. Several fundamental effects on AFM images are systematically investigated. First, it is made clear how the AFM images and the force distributions change as the load varies. Then, for the multiple-atom tips, the effects of the tip orientation and the tip apex structure, including the bond length, are examined. The characteristics of the AFM images, such as their detailed microscopic pattern, the symmetry, and the corrugation amplitude, depend strongly on these effects. In the cluster models, the interatomic potential within the tip and the surface is assumed to be harmonic, and that between the tip and the surface is taken as being of the Lennard-Jones type. It is clearly shown that AFM images reflect not merely the geometrical structure of the surface, but also various microscopic properties of the tip and the surface.