Domain structure of epitaxial PbTiO3 thin films:effects of substrate selection and film thickness

摘要

The status of strain relaxation related with theformation of crystallographic twin domains in epitaxial PbTiO3thin films grown on various substrates such as MgO (001),KTaO3(100), and SrTiO3 (001) was extensively analyzed usingsynchrotron X-ray diffraction. Each system showed thecharacteristic domain structures depending on a thermos-elasticinteraction between the film and the substrate as reflected in thevalue of c/a ratio. Perfectly c-axis oriented PbTiO3 films wereobtained on SrTiO3 (001) substrates, while the films grown onKTaO3 (100) showed a-domain dominant structures with only abit amount of c-domains embedded in matrix a-domains.Thickness dependence of the domain structure was alsocharacterized for the films grown on MgO (001), in which degreeof c-axis orientation, α, increased as a function offilm thickness within a few tens of nm regionand exhibited a saturation value of ~~0.75above a certain critical film thickness.