A Disordered-Ordered TiO2 /TiO2-x Homostructure Hosting a High-Mobility Interfacial Conductive Layer for Robust Symmetric Rectification

Abstract

Silicon’s intrinsic limitations have motivated the exploration of oxide semiconductors with engineered interfacial electronic states for advanced electronics. In this work, we develop a low-cost chemical vapor reduction (CVR) strategy to create homostructural TiO2/TiO2-x interfaces on rutile TiO2 single crystals. CVR systematically increases oxygen-vacancy concentration while preserving the rutile bulk phase and produces a stratified near-surface architecture consisting of a disordered TiO2 overlayer on an ordered TiO2-x. Density function theory suggests preferential interfacial electron accumulation driven by a vacancy gradient, which induces band bending and stabilizes interfacial conductive layer. Electron paramagnetic resonance and Hall measurements verify oxygen-vacancy-related Ti3+ and a high-quality interfacial conductive channel, respectively, while low-frequency noise indicates a low trap density. Leveraging this homostructure, a strictly symmetric Au/TiO2/TiO2-x/TiO2/Au device exhibits robust rectification with a rectification ratio >106 at ±7 V and a reverse breakdown voltage of ~40 V, remaining stable under intense ultraviolet light illumination. The rectification originates from bias-induced depletion/formation of the interfacial conductive layer, as supported by facet/orientation/probe and contact-metal control experiments.