2017 年 125 巻 6 号 p. 458-462
Tetragonal 30-nm thick Pb(ZrxTi1−x)O3 films were grown epitaxially on (100) KTaO3 and (100) SrTiO3 single crystal substrates by pulsed metal organic chemical vapor deposition. High temperature X-ray diffraction (XRD) reciprocal space mapping showed that Pb(ZrxTi1−x)O3 thin films of different compositions have a misfit strain that may not be apparent from room temperature XRD measurements. The misfit strain depends on the combination of the substrate and film composition. The misfit strain revealed by high temperature XRD measurements showed good agreement with previous theoretical predictions, even for relaxed films had except for an anomalous Pb(Zr0.45Ti0.55)O3 film, perfect (100) orientation was obtained for PbTiO3 on (100)-KTaO3 substrates with in-plane tensile and compressive strain. A mixture of (100) and (001) orientations was found for Pb(ZrxTi1−x)O3 thin films with x = 0.22 and 0.30. On (100)-SrTiO3 substrates, however, the (001) orientation was obtained for Pb(ZrxTi1−x)O3 thin films grown with x = 0–0.45. These results reveal the importance of accounting for misfit strain at the growth temperature rather than at room temperature. Anomalous Pb(Zr0.45Ti0.55)O3 films grown on KTaO3 had a perfect (001) orientation, despite having a small misfit strain at the growth temperature owing to relaxation. The lower degree of tetragonality of the crystal structure may contribute to the perfect (001) orientation in these films.