Persistent M2 phase in strongly strained (011)-oriented grains in VO2 films grown on sapphire (001) in reactive sputtering
Matsuoka, K. (Tokai University. Graduate School of Engineering)
Okimura, Kunio (Tokai University. Graduate School of Engineering)
Azhan, Nurul Hasnis (Universiti Kuala Lumpur British Malaysian Institute. Electrical Engineering Section)
Zaghrioui, Mustapha (Laboratoire GREMAN)
Sakai, Joe (Institut Català de Nanociència i Nanotecnologia)

Data:	2019
Resum:	We report on the first observation of the persistent M2 phase in strongly strained (011)-oriented grains in VO₂ films grown on Al₂O₃ (001) substrates by means of conventional rf reactive sputtering under adequate deposition conditions. Spatially resolved micro-Raman spectra clearly showed that (011)-oriented large crystalline grains with the cR-axis parallel to the substrate resulted in the appearance of the M2 phase over a wide temperature range of 30 °C. A close correlation of the appearance range of the M2 phase with the in-plane tensile stress of (011)-oriented grains was revealed by X-ray diffraction. We present a phase diagram for the M1, M2, and R phases in relation to the stress of (011)-oriented grains and temperature. It was shown that (011)-oriented micrometer-sized long grains play a crucial role in the emerging structural phase transition (SPT) via an M2 phase even in a film grown on Al₂O₃ (001), which is ordinarily reserved for the (020)-oriented VO₂ growth. The results shown here will contribute to make clear the conditions for obtaining VO₂ films with the appearance of the M2 phase in their SPT process.
Nota:	This work was supported by a Grant-in-Aid for Scientific Research (Grant No. 15K04652) from the Japan Society for the Promotion of Science.
Drets:	Tots els drets reservats.
Llengua:	Anglès
Document:	Article ; recerca ; Versió sotmesa a revisió
Matèria:	Crystalline grains ; Deposition conditions ; Micro-Raman spectra ; Rf Reactive sputtering ; Spatially resolved ; Structural phase transition ; Wide temperature ranges
Publicat a:	Journal of applied physics, Vol. 125, issue 16 (2019) , art. 165304, ISSN 1089-7550

DOI: 10.1063/1.5068700

Preprint 24 p, 1.1 MB

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