NATURE OF TIP-SAMPLE INTERACTION IN DYNAMIC-MODE ATOMIC-FORCE MICROSCOPY

The dependence curve of the resonance frequency shift of a dynamic mod e atomic force microscope (AFM) cantilever on the distance between the tip and the sample is examined. For a system sith clean semiconductor sample and a metal-coated tip, the obtained curve exhibited a larger frequency shift compared to one with a uncoated Si tip, and an increas ing deviation from van der Waals characteristics as the separation dec reased. This is due to an additional attractive force which becomes do minant at a small separation. This force is considered to play a cruci al role in high-resolution imaging of semiconductor surfaces with a dy namic made AFM.