Lithium outdiffusion in LiTi2O4 thin films grown by pulsed laser deposition

Abstract

We report surface chemical cation composition analysis of high quality superconducting LiTi${2}$O${4}$ thin films, grown epitaxially on MgAl${2}$O${4}$ (111) substrates by pulsed laser deposition. The superconducting transition temperature of the films was ~13.8 K. Surface chemical composition is crucial for the formation of a good metal/insulator interface for integrating LiTi${2}$O${4}$ into full-oxide spin-filtering devices in order to minimize the formation of structural defects and increase the spin polarisation efficiency. In consideration of this, we report a detailed angle resolved x-ray photoelectron spectroscopy analysis. Results show Li segregation at the surface of LiTi${2}$O${4}$ films. We attribute this process due to outdiffusion of Li toward the outermost LiTi${2}$O${4}$ layers.