Oxygen Diode Formed in Nickelate Heterostructures by Chemical Potential Mismatch*

Deliberate control of oxygen vacancy formation and migration in perovskite oxide thin films is important for developing novel iontronics devices. In this talk, we will discuss our observation that the concentration of oxygen vacancies formed in LaNiO₃ (LNO) during pulsed laser deposition is strongly affected by the chemical potential mismatch between the LNO film and its proximal layers. Increasing the oxygen vacancy concentration in LNO drives the metal-insulator transition and thereby significantly modifies the degree of orbital polarization. Changes in the nickel oxidization state and carrier concentration of the films have been confirmed by soft x-ray absorption spectroscopy and optical spectroscopy. Our discovery on the unidirectional-control the oxygen flow across the heterointerface, e.g. a so-called “oxygen diode”, owing to the chemical potential mismatch at interfaces in oxide heterostructures provides a new avenue to tune the physical and electrochemical properties of complex oxides useful for developing advanced information and energy materials and devices.