Regensburg 2002 – scientific programme

Parts | Days | Selection | Search | Downloads | Help

DF: Dielektrische Festkörper

DF 7: Dielektrische und ferroelektrische Schichten und Rastermethoden

DF 7.8: Talk

Thursday, March 14, 2002, 12:10–12:30, 11

Imaging ferroelectric domains by electro-optically modulated near-field microscopy — •Tobias Otto, S. Grafström, F. Schlaphof und L. M. Eng — Institut für Angewandte Photophysik, TU Dresden, 01062 Dresden

We report on a novel method for imaging domains in a ferroelectric crystal by means of optical near-field microscopy, which makes use of the symmetry breaking induced by the electro-optic effect. The sample is illuminated locally through a glass fiber tip while the power of the transmitted light collected with a microscope objective is monitored. The spatial contrast is due to the birefringence associated with the ferroelectric polarization. We exploit the electro-optic effect for modulating this birefringence by applying an alternating electric field between the tip (made conductive by a thin chromium layer) and the sample back electrode. This makes phase-sensitive detection applicable, providing a very high and 3-dimensional sensitivity. At the same time, the electro-optic modulation breaks the symmetry between antiparallel domains thereby making them optically distinguishable. The resolution achieved at domain boundaries in BaTiO₃ was estimated to be about 250 nm. A simple theoretical model based on Fresnel’s law together with the optical and electro-optical constants taken from literature is in good agreement to the experiment.