Wawra Jonas, Nielsch Kornelius, Hühne Ruben
Leibniz Institute for Solid State and Materials Research, Helmholtzstrasse 20, D-01069 Dresden, Germany.
Institute for Applied Physics, TUD Dresden University of Technology, D-01062 Dresden, Germany.
Materials (Basel). 2023 Sep 2;16(17):6036. doi: 10.3390/ma16176036.
Substrate-induced strains can significantly influence the structural properties of epitaxial thin films. In ferroelectrics, this might lead to significant changes in the functional properties due to the strong electromechanical coupling in those materials. To study this in more detail, epitaxial Ba0.7Sr0.3TiO3 films, which have a perovskite structure and a structural phase transition close to room temperature, were grown with different thicknesses on ScO3 (-rare earth element) substrates having a smaller lattice mismatch compared to SrTiO3. A fully strained SrRuO3 bottom electrode and Pt top contacts were used to achieve a capacitor-like architecture. Different X-ray diffraction techniques were applied to study the microstructure of the films. Epitaxial films with a higher crystalline quality were obtained on scandates in comparison to SrTiO3, whereas the strain state of the functional layer was strongly dependent on the chosen substrate and the thickness. Differences in permittivity and a non-linear polarization behavior were observed at higher temperatures, suggesting that ferroelectricity is supressed under tensile strain conditions in contrast to compressive strain for our measurement configuration, while a similar reentrant relaxor-like behavior was found in all studied layers below 0°C.
衬底诱导应变会显著影响外延薄膜的结构特性。在铁电体中，由于这些材料中存在强机电耦合，这可能会导致功能特性发生显著变化。为了更详细地研究这一现象，在与SrTiO3相比具有较小晶格失配的ScO3（稀土元素）衬底上生长了不同厚度的具有钙钛矿结构且结构相变接近室温的外延Ba0.7Sr0.3TiO3薄膜。使用完全应变的SrRuO3底部电极和Pt顶部接触来实现类似电容器的结构。应用不同的X射线衍射技术来研究薄膜的微观结构。与SrTiO3相比，在钪酸盐上获得了具有更高晶体质量的外延薄膜，而功能层的应变状态强烈依赖于所选衬底和厚度。在较高温度下观察到介电常数的差异和非线性极化行为，这表明与我们测量配置下的压缩应变相比，在拉伸应变条件下铁电性受到抑制，而在所有研究的低于0°C的层中发现了类似的再入弛豫铁电体行为。
