Abstract
The topographic image of dynamic force microscopy (DFM) keeping the frequency shift constant at tiny cantilever oscillation amplitudes corresponds to the constant-vertical force gradient surface, while the interpretation becomes complicated at larger oscillation amplitudes. We discuss how and the potential energy act on the tip during DFM topographic scan at various cantilever oscillation amplitudes by measuring the map on the surface at room temperature. The map is numerically converted into and maps. DFM topographic curves at various cantilever oscillation amplitudes are numerically derived by using the experimentally obtained map. In addition, we discuss how the lateral force acts on the tip at various tip-surface distances on various surface sites by an map converted from a map. The positions at which becomes zero are identified as minimum sites, such as the top of adatom sites, and maximum sites (equilibrium positions of ), such as the center positions among three center adatoms. The tip deviated from these sites is then laterally attracted toward the minimum sites. It is also demonstrated that lateral force microscopy performed at cantilever oscillation enables direct measurement of the lateral force gradient by numerically deriving the frequency shift caused by .
1 More- Received 20 February 2008
DOI:https://doi.org/10.1103/PhysRevB.77.195424
©2008 American Physical Society