Direct observation of ferroelectric domains in MOCVD-grown PbTiO3 thin films by means of transmission electron microscopy

Transmission electron microscopic observations of domain structures have been made on the PbTiO3 ferroelectric thin films prepared on (100) NaCl by metalorganic chemical vapor deposition (MOCVD). Both single-domain and alternating 90 degrees a-a and a-c domain configurations were observed in the as-deposited thin films. 180 degrees domain boundaries were also detected in the films which can compensate the polarization charges in grain boundaries. Domain formation in closely-packed polycrystalline thin films was different from that in free crystallites without boundary clamping. Domain width was found to decrease with decreasing grain size and domain splitting cannot be observed in ultrafine grains less than about 40 nm. An interesting phenomenon of polar microregions was also observed and attributed to the effect of surface electric field arising from electron irradiation during the observations.