2-DIMENSIONALLY DISCRETE FRICTION ON THE NAF(100) SURFACE WITH THE LATTICE PERIODICITY

Using the two-dimensional frictional force microscope, we observed two -dimensionally discrete friction on the NaF(100) surface with its latt ice periodicity, which is explained by the two-dimensional stick-slip model quantitatively. By the raster scan, such a discrete friction com poses the lattice periodicity image of the NaF surface. This means tha t one of the AFM contrast mechanisms of the lattice periodicity of the ionic crystal is the discrete friction. On the other hand, with a nor mal load of 14 nN the discrete friction disappeared, so the number of contact atoms is estimated as a few atoms. Thus, even under a near sin gle-atom friction regime the atomic scale friction is explained by the two-dimensional stick-sip model quantitatively.