Experimental study of internal fields and movement of single ferroelectricdomain walls

We have made a direct and submicron scale measurement of the strain, intern al electric field of single 180 degrees domain walls in ferroelectric LiTaO 3 using a collection mode Near-Field Scanning Optical Microscope. We unambi guously identify single domain walls by simultaneously recording nanometer scale topographic and optical images. The birefringence at the domain wall is used in the optical imaging. From the internal field structure we estima te the interface energy. We have also studied the pinning and movement of a single 180 degrees domain wall under an uniform applied electric field. Th e domain wall was observed to curve between the pinning defects with a radi us of curvature uniquely given by the material parameters and the applied e lectric field. The change in birefringence with applied field is related to the second order electro-optic and piezo-optic coefficients and is used to infer the orientation of the internal field. (C) 1999 Published by Elsevie r Science Ltd. All rights reserved.