Anionic Flow Valve Across Oxide Heterointerfaces by Remote Electron Doping.

Abstract

As an analogue of charged electron flows, the ionic flow could be controlled by the electronic band alignment due to the ambipolar nature of diffusion in the ionic crystal. Here, we demonstrate the active control of the anionic diffusion across heterointerfaces through remote electron doping in the capping layers. In contrast to the spontaneous ionic flux from the underlying VO2 layers to the undoped TiO2 capping layers, the activated Nb dopants in the TiO2 capping layers substantially restrict the ionic flux, despite identical growth conditions. The increase of Fermi level by Nb donors in TiO2 prevents electron flux from being generated across the interfaces by the heightening of a Schottky barrier; this electron shortage generates a kinetic close valve for the flow of negatively charged oxygen ions. Thus, these results demonstrate the importance of electron supply on charged ionic flow, thereby suggesting an unprecedented strategy for ionic-defect-induced emergent properties at interfaces.