IN-SITU STUDY OF THE EVOLUTION OF DOMAIN-STRUCTURE IN FREESTANDING POLYCRYSTALLINE PBTIO3 THIN-FILMS UNDER EXTERNAL STRESS

The ferroelectric domain structure and its evolution with external str ess in free-standing polycrystalline PbTiO3 very thin films (VTF's) (t hickness t<200 nm) and thicker films (t>200 nm), have been studied by in sirtl transmission electron microscopy. It is found that the domain structure of a VTF and its dynamic response to strain are remarkably different from those of a thicker film. The VTF is composed of nanosiz ed grains, mostly single domained. These single-domained grains manife sted a strong resistance against domain formation even under high stre ss. On the contrary, the thicker film is composed of larger grains, mo stly multidomained. The domain structure in the thicker film changes s ignificantly with external stress. The high stability of single domain s in VTF's gives a satisfactory explanation to the abnormal electrical properties of VTF's compared with those of thicker films.