  Conventional dynamic atomic force microscopy (AFM) can be extended to bimodal
and multimodal AFM in which the cantilever is simultaneously excited at two ore
more resonance frequencies. Such excitation schemes result in one additional
amplitude and phase images for each driven resonance, and potentially convey
more information about the surface under investigation. Here we present a
theoretical basis for using this information to approximate the parameters of a
tip-surface interaction model. The theory is verified by simulations with added
noise corresponding to room-temperature measurements.
