RESIDUAL STRAIN IN EPITAXIALLY-GROWN PBTIO3 AND PZT FILMS PREPARED ON (100)MGO SUBSTRATES BY MOCVD

The residual strain in epitaxially-grown PbTiO3 and PZT films prepared on (100) MgO substrates by CVD was observed by X-ray diffraction. The lattice parameter ratio of c-axis to alpha-axis (c/alpha) in film was smaller than that of the powder. This is caused by the thermal strain owing to the thermal expansion difference between the him and the substrate below the Curie temperature. The large expansion of c-axis and shrinkage of alpha-axis of the film comparing with that of the substrate under the cooling process below the Curie temperature made the large strain in the film. On the other hand, the nonuniform strain in the him was also larger than that of powder. This is thought to be originated to the gradient of the lattice parameters along the film thickness.