Manipulating the Hydrogen-Associated Insulator-Metal Transition Through Artificial Microstructure Engineering

Hydrogen-associated filling-controlled Mottronics within electron-correlated system provides a groundbreaking paradigm to explore exotic physical functionality and phenomena. Dynamically controlling hydrogen-related phase transitions through external fields offers a promising route for designing protonic devices in multidisciplinary fields but faces high-speed bottlenecks owing to slow bulk diffusion of hydrogens. Here, a promising pathway is presented to kinetically expedite the electronic state evolution in VO₂ system by taking advantage of artificial microstructure design. Typically, inclined domain boundary configuration and c_R-faceted preferential orientation, simultaneously realized in VO₂/Al₂O₃ (1 $\overline{1}$ 02) heterostructure, significantly lower the diffusion barrier through creating an unobstructed conduit for hydrogen diffusion. As a result, the achievable switching speed through hydrogenation outperforms that of counterpart grown on widely-utilized c-plane Al₂O₃ substrate by 2-3 times, with resistive switching concurrently improved by an order of magnitude. Of particular interest, an anomalous uphill hydrogen diffusion observed for VO₂ with a diffusion highway fundamentally deviates from basic Fick's law, unveiling a deterministic role of hydrogen spatial distribution in tailoring electronic state evolution. The present work not only provides a powerful tuning knob for manipulating ionic evolution, endowing with great potential in designing advanced protonic devices, but also deepens the understanding of hydrogen-associated insulator-metal transition in electron-correlated systems.