  The contrast mechanism for the visualization of ferroelectric domain
boundaries with lateral force microscopy is generally assumed to be caused by
mechanical deformation of the sample due to the converse piezoelectric effect.
We show, however, that electrostatic interactions between the charged tip and
the electric fields arising from the surface polarization charges dominate the
contrast mechanism. This explanation is sustained by quantitative analysis of
the measured forces as well as by comparative measurements on different
materials.
