Intermodulation atomic force microscopy

A mode of atomic force microscopy (AFM) is demonstrated where an oscillating AFM cantilever having linear response is driven with two frequencies in the vicinity of a resonance. New frequencies in the response, known as intermodulation products, are generated when the linearity of the cantilever response is perturbed by the nonlinear tip-surface interaction. A rich structure of the intermodulation products is observed as a function of the probe-surface separation, indicating that it is possible to extract much more detailed information about the tip-surface interaction than is possible with the standard amplitude and phase imaging methods.