Ferroelectric domain structures of polycrystalline PbTiO3 thin films prepared by MOCVD

Ferroelectric domain structures of polycrystalline PbTiO3 thin films were i nvestigated by using transmission electron microscopy. The grain size of th e prepared films ranged from 300 Angstrom to 2000 Angstrom. It was observed that 90 degrees domains displayed the shape of simple lamella twinning, wi th neighboring grains connected across grain boundaries; even at very small grains such as 300 Angstrom, domain structures were found. In some 90 degr ees domain boundaries, defects such as dislocations were found. These confi gurations of 90 degrees domains are associated with stress relief due to th e very large tetragonality of PbTiO3 thin films which was estimated to be a bout 1.057; this value was nearly constant independent of grain size. 180 d egrees domains showed 90 degrees-domain-dependent structures with irregular morphologies. The structure of 180 degrees domains was discussed in terms of energy minimization during phase transitions.