Formation of the ferroelectric domains in epitaxial PbTiO3 thin films grown by metalorganic chemical vapor deposition

Epitaxial PbTiO3 thin films have been prepared by metalorganic chemical vapor deposition under reduced pressure. The formation of ferroelectric domains in films grown on SrTiO3 and LaAlO3 substrates was investigated by synchrotron radiation and Rutherford backscattering spectroscopy. Single-domain (3000-Angstrom thick) and multi-domain (4500-Angstrom thick) PbTiO3 films were produced on SrTiO3. For multi-domain PbTiO3 film, the c-domain presented epitaxial structure with its c-axis perpendicular to the substrate surface, while a-domains aligned four-fold symmetrically with c-domains by 2.79 degrees off the c-axis of c-domains. In the film, the measured lattice constants (a, b and c) of the a- and c-domains were different from each other, indicating that the films suffered a modulated strain during domain formation. In contrast, both the a and c domains of films on LaAlO3 were alternatively aligned on substrate with the a-axis of the a-domain and the c-axis of c-domains perpendicular to the substrate surface. Two-dimensional distribution of these domains is proposed and the formation of these kinds of domains is discussed. The surface morphology and phase transition process of single and multi domain PbTiO3 him on SrTiO3 were studied by atomic force microscope (AFM) and high temperature X-ray diffraction, respectively.