X-Ray Writing of Metallic Conductivity and Oxygen Vacancies at Silicon/SrTiO₃ Interfaces

Tunable electronic properties of transition metal oxides and their interfaces offer remarkable functionalities for future devices. The interest in these materials has been boosted with the discovery of a 2D electron gas (2DEG) at SrTiO₃ (STO)-based interfaces. For the majority of these systems, oxygen vacancies play a crucial role in the emergence of interface conductivity, ferromagnetism, and high electron mobility. Despite its great importance, controlling the density and spatial distribution of oxygen vacancies in a dynamic way remains extremely challenging. Here, lithography-like writing of a metallic state at the interface between SrTiO₃ and amorphous Si using X-ray irradiation is reported. Using a combination of transport techniques and in operando photoemission spectroscopy, it is revealed in real time that the X-ray radiation induces transfer of oxygen across the interface leading to the on-demand formation of oxygen vacancies and a 2DEG in STO. The formed 2DEG stays stable in ambient conditions as the interface oxygen vacancies are stabilized by the capping of Si. The study provides a fundamental understanding of X-ray-induced redox reactions at the SrTiO₃-based interfaces and in addition shows the potential of X-ray radiation for patterning stabile conductive pathways for future oxide-based electronic devices.