The formation of TiO₂/VO₂ multilayer structure via directional cationic diffusion

The alternative VO2/TiO2 nanostructure is a potential candidate for application in optical or electrical devices. A promising and straightforward route to form tunable alternative VO2/TiO2 nanostructure is in high demand. Herein, we demonstrate that the VO2/TiO2 nanostructure could be self-assembled from the VO2 film/TiO2 substrate via directional cationic migration, characterizing Ti-rich nano-lamellas with nanoscale spacing along the c-axis. Through aberration-corrected high-resolution transmission electron microscopy, it has been shown that the realization of directional cationic migration is assisted by the interstitial position inside the VO2 lattice. Non-equilibrium cationic diffusion could even retain these interstitial atoms in the form of incoherent strain lines, which affect the local electronic structure as validated by theoretical calculation. Due to Ti-rich nano-lamellas and incoherent strain lines, the phase transition temperature decreased (∼10 °C). The idea of tailoring the elemental distribution by directional cationic diffusion significantly broadens the functional application of VO2 films.