Ferroelectric domain structures of polycrystalline PbTiO3 thin films prepared by MOCVD

Abstract

Ferroelectric domain structures of polycrystalline PbTiO3 thin films were investigated by using transmission electron microscopy. The grain size of the prepared films ranged from 300 Angstrom to 2000 Angstrom. It was observed that 90 degrees domains displayed the shape of simple lamella twinning, with neighboring grains connected across grain boundaries; even at very small grains such as 300 Angstrom, domain structures were found. In some 90 degrees domain boundaries, defects such as dislocations were found. These configurations of 90 degrees domains are associated with stress relief due to the very large tetragonality of PbTiO3 thin films which was estimated to be about 1.057; this value was nearly constant independent of grain size. 180 degrees 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.