Oxygen point defect stabilized metastable M3‐phase VO2 films. (June 2022)

• Record Type: Journal Article
• Authors: Lee, Dooyong; Song, Sehwan; Min, Taewon; Kim, Hyegyeong; Kim, Jiwoong; Han, Seonghoon; Bae, Jong-Seong; Lee, Jisung; Kim, Yoosuk; Lee, Jouhahn; Jang, Jae Hyuck; Lee, Jaekwang; Park, Sungkyun
• Is Part Of: Applied materials today. Volume 27(2022)
• Publication Date: 2022-06
• Subjects: Polymorph phase -- M3-VO2 phase -- Insulator-metal transition -- Oxygen point defect; Materials science -- Periodicals; Materials -- Research -- Periodicals; 620.1105
• DOI: 10.1016/j.apmt.2022.101474
• Languages: English
• ISSNs: 2352-9407

Abstract

Highlights: M3-VO2 phase, a polymorph phase of VO2, was stabilized by oxygen point defect in the ambient environment. Oxygen point defect was located at the tetrahedral interstitial site with the lowest formation energy among defects in VO2 . Oxygen point defect at the tetrahedral interstitial site induces the M3-VO2 phase by increasing the length and angle of the zigzag V-V chain. M3-VO2 phase had a higher phase transition temperature and a sharper phase transition than the M1-VO2 phase M3-VO2 phase transits to the rutile VO2 phase without an intermediate polymorph phase. Abstract: Point defects can stabilize various metastable polymorph phases of complex oxides showing unique physical properties, even though their role in the stabilization of the metastable phase is unclear. In this study, we examined the role of oxygen point defects in stabilizing a polymorph M3-VO2 phase and its transition characteristics. Raman spectroscopy revealed the M3-VO2 phase at the ambient environment for the VO2 film grown on c -Al2 O3 substrate at a higher oxygen flow rate. High-resolution XRD and DFT calculation exhibited that the M3-VO2 phase was stabilized by oxygen point defect incorporated into the tetrahedral interstitial site, the most stable defect type in the monoclinic VO2 system. The M3-phase had a higher IMT temperature and a sharper IMT than the M1-phase due to the decrease in interdimer hopping energy and the small energy barrier for the IMT by the slightly zigzag V-V chain. Furthermore, the temperature-dependent Raman spectra showed the unprecedented structural phase transition from the M3-VO2 phase to the R-phase without an intermediate state. Overall, these findings provide fundamental information on the role of oxygen point defects in realizing metastable polymorph phases in promising new technological materials. Graphical abstract: Image, graphical abstract