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 highly mobile 2D electron gas (2DEG) at SrTiO₃‐based interfaces. Oxygen vacancies in these systems play a crucial role in the emergence of interface conductivity and ferromagnetism. In this work, A. Chikina et al report a lithography‐like writing of a metallic state at the interface between SrTiO₃ and amorphous Si using X‐ray irradiation. Combining transport techniques and operando photoemission spectroscopy at the ADRESS beamline of SLS, they discover that the X‐ray radiation induces transfer of oxygen from SrTiO₃ to Si across the interface. This process leads to formation of oxygen vacancies in SrTiO₃, which inject electrons into the interfacial 2DEG (see Fig. 1). As the interface oxygen vacancies are stabilized by the Si capping, the 2DEG formed in this way stays stable in ambient conditions. The study provides a fundamental understanding of X‐ray‐induced redox reactions at the SrTiO₃‐based interfaces. In the device perspective, the X‐ray induced formation of oxygen vacancies may provide means for the spatially controlled superconductivity, magnetism, and memristive functionalities in oxide heterostructures.