PFM image from cross-talk
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This is an important question. For several of these topics there may be one answer in terms of fundamental physics and an answer that is specific to a particular microscope design. I hope that we will discuss both.
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I understand that you would not want to use the softest cantilever to minimize the electrostatic interactions, but do you obtain different PFM responses from using cantilevers with various stiffnesses and can you use these different responses to obtain a more complete picture of the piezo-response?
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Theoretically, cantilever stiffness hsould not affect PFM signal in th elow-frequency regime. This is generally true for 1-40 N/m cantilevers, while below 1 N/m electrostatics plays a role.
In some cases (e.g. ferroelectric polumers or biomaterials) there is no chois ebut to use 0.03 - 0.1 N/m levers. -
There can be several indications that you are dealing with cross-talk. In case of polycrystalline films, if you see contours of grain boundaries in your PFM image it is most likely due to cross-talk. Similarly, if all grains appear in a bipolar state with phase boundaries being almost parallel in all grains - it is cross talk.
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Generally, if PFM image "resembles" the error signal for topography it is a bad sign.