REFLECTION ELECTRON-MICROSCOPY OF FERROELECTRIC DOMAIN-WALLS IN BATIO3

Ferroelectric domain walls and domain structures in the tetragonal pha se of BaTiO3 were studied by reflection electron microscopy (REM). An a-a 180 degrees domain wall was observed for the first time in REM, wh ich appeared with a zigzag shape, and showed a dark contrast that is n ot explained from phase contrast and also diffraction contrast. It was also found that the a-c 90 degrees domain wall contrast reverses when a sign of defocus changes. A geometrical model is proposed to explain the property of the a-c domain wall, contrast, which describes that t he reflected electron beams from the neighbouring domain surfaces beco me overlapped or apart from each other, depending on the surface confi guration. A domain structure at the a-e 90 degrees domain wall can be determined from the type of surface configuration found from the domai n wall contrast and the observation of the a-a 180 degrees domain wall .