Extrinsic and Intrinsic Charge Transfer at Interfaces of Membrane-Based Oxide Heterostructures

Engineering complex oxide heterostructures and their interfaces has revealed a plethora of emergent electronic and magnetic properties. To achieve these functionalities beyond conventional epitaxy, building heterogeneous integrated electronic architectures have been possible from the advances in free-standing oxides and their integration with semiconductors. However, to harness the physical phenomena of oxides in such co-integrated environments, it is necessary to achieve atomically defined membrane-based oxide heterostructures and subsequent control of charge-transfer. Here, we report on the direct growth-control of the surface termination of SrTiO₃ membranes, eliminating any B-HF requirements, and subsequent transfer of TiO₂-terminated SrTiO₃ membranes onto silicon (Si) via a sacrificial layer route. This approach yields atomically defined step-terraced membrane-based substrates on silicon support. By systematic growth control of LaAlO₃ on these templates, we demonstrate distinct signatures of oxygen-vacancy-induced (ionic) and intrinsic (electronic) charge transfer mechanisms. A systematic crossover between these processes is observed, based on near-ambient pressure XPS, probing reversible and irreversible contributions of interfacial charge transfer during redox-cycling. These results indicates that TiO₂-termination in the oxide membrane may have been achieved, which is a prerequisite for tailoring and fine-tuning membrane-based oxide heterointerfaces for electronic and ionic phenomena in confined systems beyond conventional epitaxy.