Contrast mechanism for the detection of ferroelectric domains on all faces of LiNbO3 using piezoresponse force microscopy

We apply piezoresponse force microscopy (PFM) to reveal the domain structures on all faces of LiNbO3 single crystals. Therefore we investigated a two-dimensionally poled sample, all faces optically polished. On the z-face the PFM contrast is known to be caused by the piezoelectrically driven thickness change of the crystal. On the x- and y-faces, however, the contrast mechanism was found to be governed by a lateral movement of the surface underneath the tip. Depending on the relative orientation of the cantilever with respect to the crystallographic axes of the sample this results in a torsion or buckling movement of the cantilever. In order to support this explanation we mounted the sample on a high-precision rotation stage. The high stability of the set-up allows to rotate the sample during data acquisition. We could therefore precisely determine the angular dependency of the movement on the tip on the crystallographic axis. The experimental results are in good agreement with the theoretically expected values