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 similar to 170-nm-thick film with an average grain size of similar to 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.