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 Å to 2000 Å. It was observed that 90° domains displayed the shape of simple lamella twinning, with neighboring grains connected across grain boundaries; even at very small grains such as 300 Å, domain structures were found. In some 90° domain boundaries, defects such as dislocations were found. These configurations of 90° 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° domains showed 90°-domain-dependent structures with irregular morphologies. The structure of 180° domains was discussed in terms of energy minimization during phase transitions.

Keywords:

• PbTiO₃ thin films
• ferroelectric domains
• 90° domains
• 180° domains
• simple lamella twinning
• tetragonality
• grain size