Epitaxial Zintl aluminide SrAl₄ grown on a LaAlO₃ substrate

Zintl phases are a class of intermetallic materials that have simultaneously ionic and covalent bonding resulting from charge transfer between two different atomic species. We present a combined first principles and experimental study of Zintl-phase SrAl₄, which is grown in thin film form on the perovskite oxide LaAlO₃ using molecular beam epitaxy. The structural properties are investigated using reflection-high-energy electron diffraction, x-ray diffraction, and cross-section transmission electron microscopy, which reveal relaxed epitaxial island growth. Photoelectron spectroscopy measurements verify the Zintl-Klemm nature of the bonding in the material and are utilized to determine the band offset and the work function of SrAl₄, while transport measurements confirm its metallic behavior. The experimentally observed properties are confirmed using density functional calculations.