Switching enhancement in VO₂(M) thin films through structural design and oxygen vacancy engineering

This study investigates single-phase VO₂(M) thin films grown on amorphous SiO₂ and examines the effects of film thickness and oxygen partial pressure on the electrical switching behavior of lateral and vertical devices. Phase-pure VO₂(M) films were achieved by controlling the O₂/Ar ratio during reactive sputtering, enabling systematic tuning of electrical properties. In lateral devices, the switching behavior is governed by Joule-heating-assisted and spatially inhomogeneous phase-transition dynamics, where localized metallic domains nucleate at preferential sites and evolve through percolative propagation, resulting in gradual and device-dependent switching. In contrast, vertical devices exhibit a strong thickness dependence. Thinner films show gradual and asymmetric switching due to interfacial and defect-related effects that disrupt domain evolution, whereas thicker films enable efficient domain expansion and connectivity, leading to abrupt, symmetric, and reproducible switching. Overall, the switching behavior can be understood within a unified framework of localized nucleation and domain propagation, and can be effectively tuned by controlling oxygen partial pressure and film thickness.