Size effects on stress relaxation across the metal-insulator transition in VO₂ thin films

We report on in situ stress relaxation behavior of vanadium dioxide thin films across the thermally driven metal-insulator transition (MIT) and size effects. Although the residual stress follows an inverse relationship with film thickness, the metal-insulator phase transition-induced stress varies nonmonotonically with increase in film thickness and grain size. Maximum transformation stress of -447 MPa is observed across the MIT for ∼170-nm-thick film with an average grain size of ∼70 nm. The interplay between constraint effects and nanostructure leads to nontrivial stress relaxation trends and provides insights into design of phase transition materials for switching devices.