Evaluation of electrically polar substances by electric scanning force microscopy. Part II: Measurement signals due to electromechanical effects

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Abstract
The influence of electromechanical effects upon the signals from an electric scanning force microscope (EFM) in repulsive contact mode have been analysed. For this aim, electrically polar substances are investigated by EFM and two other methods, and the phases of higher harmonic signals are compared. Analysis shows that for a lead zirconate titanate thin film: in the 1st harmonic EFM signal, the influence of the piezoeffect outweighs that of Maxwell stress due to spontaneous polarization. In the 2nd harmonic EFM signal, the Maxwell stress due to permittivity dominates the influence of electro-striction. It is shown that the contribution of electromechanical effects to the EFM signal depends on the distance of the EFM tip to the sample surface. First proof is given for lateral variation of electrostriction on a nanometer scale.