Principle of In-Situ AFM

AFM relies on the detection of force, not current, and therefore the substrate does not need to be conductive. AFM can also work with an electrochemical interface [6, 17-21]. As force measurements are insensitive to the current flow at the substrate surface, AFM can be used to study electrochemical processes accompanied by faradaic currents. However, gas evolution at the surface should be avoided as bubbles interfere with the light path of the laser beam. 

It should be noted that the force measured in AFM is proportional to the inverse of the tip-sample distance to the power of n. This is less sensitive than the exponential variation of tunneling current as a function of tip-sample distance in STM. In addition, due to the restricted sharpness of the tip apex of an AFM probe (presently, the finest commercial probes have a radius 10 nm), the convolution effect of the tip shape may be 

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