Interfacially engineered oxygen octahedral rotations and their impact on strain relief in coherently grown SrRuO3 films

Abstract

We report synchrotron x-ray diffraction investigations of interfacially engineered oxygen octahedral rotations and their impact on strain relief in perovskite $\mathrm{SrRu}{\mathrm{O}}_{3}$ films. We show that octahedral rotations with distinct patterns and magnitudes can be accommodated into coherently grown films. The $\mathrm{SrRu}{\mathrm{O}}_{3}$ film grown directly on the $\mathrm{GdSc}{\mathrm{O}}_{3}$ substrate has the $\mathrm{Ru}{\mathrm{O}}_{6}$ octahedral rotation with the ${a}^{\ensuremath{-}}{b}^{+}{c}^{\ensuremath{-}}$ pattern in the Glazer notation and the rotation angles of ${\ensuremath{\alpha}}_{\mathrm{rot}}=6.6\ifmmode\pm\else\textpm\fi{}0.{2}^{\ensuremath{\circ}}, {\ensuremath{\beta}}_{\mathrm{rot}}=5.5\ifmmode\pm\else\textpm\fi{}0.{2}^{\ensuremath{\circ}}$, and ${\ensuremath{\gamma}}_{\mathrm{rot}}=3.6\ifmmode\pm\else\textpm\fi{}0.{2}^{\ensuremath{\circ}}$. On the other hand, when a 1-nm-thick $\mathrm{BaTi}{\mathrm{O}}_{3}$ layer without $\mathrm{Ti}{\mathrm{O}}_{6}$ rotations is inserted between the $\mathrm{SrRu}{\mathrm{O}}_{3}$ and $\mathrm{GdSc}{\mathrm{O}}_{3}$, the $\mathrm{SrRu}{\mathrm{O}}_{3}$ has the $\mathrm{Ru}{\mathrm{O}}_{6}$ rotation with ${a}^{\ensuremath{-}}{b}^{0}{c}^{+}$, and ${\ensuremath{\alpha}}_{\mathrm{rot}}=5.6\ifmmode\pm\else\textpm\fi{}0.{8}^{\ensuremath{\circ}}$ and ${\ensuremath{\gamma}}_{\mathrm{rot}}=3.6\ifmmode\pm\else\textpm\fi{}0.{8}^{\ensuremath{\circ}}$. These results indicate that there are some degrees of freedom in the octahedral rotations accommodated in $\mathrm{SrRu}{\mathrm{O}}_{3}$ depending on the interface structure and that the ${\ensuremath{\gamma}}_{\mathrm{rot}}$ rotations play the important roles in the film's structural properties when the rotation about the ${[010]}_{\mathrm{pc}}$ axis is blocked. We also found that the strain relief in the film is influenced by the interfacially engineered octahedral rotations. The interfacial $\mathrm{BaTi}{\mathrm{O}}_{3}$ layer results in the in-plane periodic lattice modulation in the t-SRO film, allowing for the anisotropic relief of the substrate-induced strain. The results highlight the importance of the interface structure as a factor, determining not only octahedral rotations in coherently grown SRO films but also the strain reliefs in them.