Molecular Beam Epitaxy (MBE) Growth of Model Thin Films to Study Interfacial Interactions

To address the increasing demand for energy storage technology, model thin films battery cathode systems are highly desirable since they avoid the complexity associated with polycrystalline or nano-sized powders which make detailed study of surfaces and interfaces difficult. However, the behavior of thin films depends highly on defect concentration, grain boundaries, and surface terminations [1,2]. An ideal way to study the material and interface properties is by isolating a particular crystallographic orientation and investigate the orientation dependent performance. To study such behavior, we have developed model thin films systems of different orientations by using molecular beam epitaxy (MBE) to study the interfacial ion diffusion and structural defects, and characterized them using aberration corrected transmission electron microscopy (STEM), electron energy loss spectroscopy (EELS), and energy dispersive x-ray spectroscopy (EDXS). These model thin film cathode framework will be used for monovalent Li⁺ ions as well as divalent Mg²⁺ ions intercalation to quantify the evolution of defect concentrations and surface structures.