Influence of Strain on VO₂ Stoichiometry and its Metal-Insulator Transition

VO₂ is a canonical example of a strongly correlated system that exhibits a wide range of polymorphs such as monoclinic (M1, M2, T) and rutile (R) with each exhibiting unique electronic and optical properties. VO₂ undergoes a metal-insulator transition (MIT) around 340K accompanied by a first order phase transition from high temperature metallic rutile phase to low temperature insulating monoclinic phase. Understanding and controlling this MIT by varying chemical composition, and external stimuli, such as strain, temperature, and electric field is necessary to realize VO₂ based devices. In this talk, we will explore the coupling between experimentally realizable strain and oxygen vacancy (V_O^q) formation as well as diffusion energies in VO₂ using beyond-DFT methods (e.g. DFT+U, meta- and hybrid DFT), benchmarked against very accurate many-body Quantum Monte Carlo (QMC) calculations. Theory predicts that strain facilitates electron-doping via creation of oxygen vacancies in VO₂, consistent with our experimental findings on the strain control of the MIT in VO₂ thin-films.