Growth and characterization of superconducting spinel oxide LiTi2O4LiTi2O4 thin films

Epitaxial films of LiTi2O4LiTi2O4 on single crystalline substrates of MgAl2O4MgAl2O4, MgO, and SrTiO3SrTiO3 provide model systems to systematically explore the effects of lattice strain and microstructural disorder on the superconducting state. Lattice strain that affects bandwidth gives rise to variations in the superconducting and normal state properties. Microstructural disorder, such as antiphase boundaries that give rise to Ti network disorder, reduces the critical temperature, and Ti network disorder combined with Mg interdiffusion lead to a much more dramatic effect on the superconducting state. Surface sensitive X-ray absorption spectroscopy has identified Ti to retain site symmetry and average valence of the bulk material regardless of film thickness.