Control of the metal–insulator transition in vanadium dioxide by modifying orbital occupancy

External control of the conductivity of correlated oxides is one of the most promising schemes for realizing energy-efficient electronic devices. Vanadium dioxide (VO 2 ), an archetypal correlated oxide compound, undergoes a temperature-driven metal–insulator transition near room temperature with a concomitant change in crystal symmetry. Here, we show that the metal–insulator transition temperature of thin VO 2 (001) films can be changed continuously from ∼285 to ∼345 K by varying the thickness of the RuO 2 buffer layer (resulting in different epitaxial strains). Using strain-, polarization- and temperature-dependent X-ray absorption spectroscopy, in combination with X-ray diffraction and electronic transport measurements, we demonstrate that the transition temperature and the structural distortion across the transition depend on the orbital occupancy in the metallic state. Our findings open up the possibility of controlling the conductivity in atomically thin VO 2 layers by manipulating the orbital occupancy by, for example, heterostructural engineering.