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.