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

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journal contribution
posted on 2020-07-22, 21:32 authored by Dooyong Lee, Donghyuk Yang, Hyegyeong Kim, Jiwoong Kim, Sehwan Song, Kyoung Soon Choi, Jong-Seong Bae, Jouhahn Lee, Jaekwang Lee, Yunsang Lee, Jiafeng Yan, Jaeyong Kim, Sungkyun Park
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.