In situ high-temperature x-ray diffraction study on domain evolution in ferroelectric (Pb,La)TiO3 epitaxial thin films

The cooling process encountered during fabrication of epitaxial Pb1-xLaxTiO3(PLT, x=0.00-0.12) thin films prepared on MgO(001) single-crystal substrates is simulated using an x-ray high-temperature attachment, and x-ray diffraction measurements are performed at various temperatures, during which a ferroelectric 90 degrees domain structure has been evolved. The lattice constants and the degree of c-axis orientation (alpha) of the epitaxial PLT films are evaluated as a function of temperature below the deposition temperature (650 degrees C). The 0.00 La-PLT film shows nucleation of c domains at T-C, growth of them at the expense of a domains below T-C, and c-domain dominant structure at room temperature. By contrast, the 0.12. La-PLT film shows an abrupt evolution of the c-domain dominant structure at T-C, and a higher degree of c-axis orientation at room temperature. The full width at half-maximum of the 003 perovskite peak is used to quantify the crystal quality of the films as a function of temperature. Considerable change in crystal quality occurs after the cubic-to-tetragonal phase transformation. Significant improvement of the crystal quality of the PLT films with high La concentration have been realized predominantly at the curie temperature when the films transformed to the tetragonal phase. (C) 1997 American Institute of Physics.