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.