Deposition-Temperature-Mediated Selective Phase Transition Mechanism of VO₂ Films

A clear experimental explanation of the contribution of Mott and Peierls transitions to the insulator–metal transition (IMT) characteristics in vanadium dioxide (VO₂) is still lacking. Examining the crystal and electronic structures of epitaxial VO₂ films grown at various deposition temperatures, a Mott or a Peierls transition was observed. The VO₂ film deposited at 500 °C showed suppressed Peierls transition characteristics because of the large in-plane compressive strain in the insulating phase. The VO₂ films deposited at 600 and 650 °C had a higher IMT temperature because of the relaxation of both the in-plane and out-of-plane strain, and there were abundant V⁴⁺ states. Therefore, it was related to a collaborative Mott–Peierls transition. Finally, the VO₂ film deposited at 720 °C showed a suppressed Mott transition because of the abundance of V³⁺ states in the insulating phase. Furthermore, an analysis of the electronic structure of the insulating and metallic phases using in situ X-ray photoelectron spectroscopy and X-ray absorption spectroscopy provide a complete band diagram to support the above explanation of the deposition-temperature-dependent IMT characteristics.