Spectroscopy evidence for directional oxygen ionic transport in correlated oxide heterostructures with tunable migration dynamics

Abstract

Oxygen chemical potential mismatch (Δμ O ) spontaneously drives directional ionic transfer across oxide heterointerface, offering a facile route to introduce oxygen deficiency beyond traditional thermal stimulus in monolayer materials. Here, we provide compelling spectroscopy evidences for directional oxygen ionic transport in TiO 2 /VO 2 heterostructure through a built-in Δμ O gradient, uncovering underneath critically balanced Peierls-Mott physics. Given the exceptional sensitivity of VO 2 to external stimuli, the band filling in t 2g band of VO 2 , together with the suppression in V-V dimerization, is clearly clarified by using synchrotron and Raman spectroscopy techniques, circumventing the artifacts typically introduced by electron beam illumination. Oxygen off-stoichiometry in the TiO 2 overlayer functionalized as an oxygen reservoir is identified as a powerful tuning knob for actively accelerating the ionic transport dynamics. Harnessing the symmetry mismatch between VO 2 and Al 2 O 3 , either inclined or vertically aligned domain boundary configuration achieved in VO 2 can offer an efficient pathway for oxygen ionic diffusion, extending the horizons in material design for iontronic devices. Our findings establish a feasible strategy to controllably manipulate the oxygen ionic transport in oxide heterostructures, driven by the Δμ O gradient, while offering direct spectroscopy evidences that deepen the understanding of defect-associated correlated physics.