Base Metals Induced Oxygen Migration and Adjustable Performance in Multifunctional Oxide Heterojunction Devices

The chemical and electronic interactions at metal/oxide heterojunctions is pivotal in determining the electronic properties of oxide devices utilized in microelectronics, catalysis, and photovoltaic systems. In this study, interfacial oxidation migrations within a model heterostructure system, consisting of a La_0.7Sr_0.3MnO₃ film overlaid by various metallic (Ti, Al, Cu, Ag, and Au) ultrathin layers are systematically investigated. It is experimentally demonstrated that at elevated deposition temperature, the oxygen-active ultrathin overlayers of base metals such as Ti and Al significantly derive oxygen from the underlying La_0.7Sr_0.3MnO₃ film, inducing a perovskite to brownmillerite phase transition in the underlying functional oxide film. Conversely, no structural transitions are observed for La_0.7Sr_0.3MnO₃ film when it is capped by noble metals (Au, Ag), which possess relative high oxidation formation energy. These observations are crucial for the development of novel crystalline and electronic architectures in metal/oxide heterostructures, offering a refined approach to modulate interfacial reactivity without compromising the functionality of oxide-based heterojunction devices.