Fig. 3

Nanoscopic investigation of the crystal structure of \(5\%-{\mathrm{BLSO}}_{{\mathrm{MgAl}}_{2}{\mathrm{O}}_{4}}^{\mathrm{MgO}}\). a The cross-sectional transmission electron microscopic image clearly shows the BLSO film, MgO template layer, and MgAl₂O₄ substrate. b Given the sharp interfaces, fast Fourier transform images of selected areas indicate (001)-oriented epitaxial growth of the BLSO film and MgO template layer. c Energy-dispersive X-ray spectroscopy reveals negligible intermixing of Ba (yellow), La (green), Sn (purple), Mg (blue), and Al (red) atoms among the layers. d Atomic force microscopy reveals the flat surface (roughness ~ 0.9 nm) of a 440-nm-thick BLSO film