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

Abstract

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.