Manipulating the hydrogen-induced 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-induced 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, we present a promising pathway to kinetically expedite hydrogen-related Mott transition in correlated VO2 system by taking advantage of artificial microstructure design. Typically, inclined domain boundary configuration and cR-faceted preferential orientation simultaneously realized in VO2/Al2O3 (102) heterostructure significantly lower the diffusion barrier via creating an unobstructed conduit for hydrogen diffusion. As a result, the achievable switching speed through hydrogenation outperforms that of counterpart grown on widely-reported 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 highway for hydrogen diffusion 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 versatile strategy for manipulating ionic evolution, endowing with great potential in designing high-speed protonic devices, but also deepens the understanding of hydrogen-induced Mott transitions in electron-correlated system.