Contributions to in-plane piezoresponse on axially symmetrical samples

We report on the influence of system-immanent asymmetries on the interpretation of in-plane piezoresponse force microscopy (PFM). As PFM is a surface scanning method, the electromechanical interaction of probe tip and sample is a key aspect of all experiments. An initial characterization of topography, surface state, and conductivity is mandatory to separate their signal from the response due to an in-plane polarization state. Our findings underline that any reduction of radial symmetry in the tip-sample system creates an otherwise symmetry-prohibited in-plane signal.