Lattice distortions and octahedral rotations in epitaxially strained LaNiO3/LaAlO3 superlattices

Using a complementary combination of x-ray diffraction and atomically resolved imaging we investigated the lattice structure of epitaxial LaNiO3/LaAlO3 superlattices grown on a compressive-strain inducing LaSrAlO4 (001) substrate. A refinement of the structure obtained from the x-ray data revealed the monoclinic I 2/c 1 1 space group. The (Ni/Al)O6 octahedral rotation angle perpendicular to the superlattice plane is enhanced, and the one parallel to the plane is reduced with respect to the corresponding bulk values. High-angle annular dark field imaging was used to determine the lattice parameters within the superlattice unit cell. High-resolution electron microscopy images of the oxygen atoms are consistent with the x-ray results.

我们利用X射线衍射和原子分辨成像的互补组合，研究了在产生压应变的LaSrAlO₄(001)衬底上生长的外延LaNiO₃/LaAlO₃超晶格的晶格结构。对从X射线数据获得的结构进行精修，揭示出单斜晶系的\(I2/c11\)空间群。垂直于超晶格平面的(Ni/Al)O₆八面体旋转角增大，而平行于平面的旋转角相对于相应的体相值减小。利用高角度环形暗场成像来确定超晶格单胞内的晶格参数。氧原子的高分辨率电子显微镜图像与X射线结果一致。