Strong strain gradients and phase coexistence at the metal-insulator transition in VO2 epitaxial films
Rodríguez Domínguez, Laura (Institut Català de Nanociència i Nanotecnologia)
Sandiumenge Ortiz, Felip (Institut de Ciència de Materials de Barcelona)
Frontera, Carlos (Institut de Ciència de Materials de Barcelona)
Caicedo Roque, Jose Manuel (Institut Català de Nanociència i Nanotecnologia)
Padilla-Pantoja, Jessica (Institut Català de Nanociència i Nanotecnologia)
Catalan, Gustau (Institut Català de Nanociència i Nanotecnologia)
Santiso, José (Institut Català de Nanociència i Nanotecnologia)

Date:	2021
Abstract:	The proximity of a thermodynamic triple point and the formation of transient metastable phases may result in complex phase and microstructural trajectories across the metal-insulator transition in strained VO films. A detailed analysis using in-situ synchrotron X-ray diffraction unveils subtle fingerprints of this complexity in the structure of epitaxial films. During phase transition the low-temperature monoclinic M1 phase is constrained along the {111} planes by the coexisting high-temperature R phase domains, which remain epitaxially clamped to the substrate. This geometrical constraint induces counteracting local stresses that result in a combined tilt and uniaxial in-plane compression of M1 domains, and a concomitant anomalous c-axis elongation. This mechanism progressively transforms the M1 phase into the transitional triclinic phase (T), and ultimately into the monoclinic M2 phase, generating strong strain and tilt gradients that remain frozen after the complete transformation of the R phase upon cooling to RT. The transformation path of VO films, the complex competition between stable and metastable VO polymorphs and its impact on the structure of the low temperature monoclinic state, provide essential insights for understanding the electronic and mechanical properties of the films at the nanoscale, as well as to control their use in functional devices.
Grants:	European Commission 730872 Ministerio de Economía, Industria y Competitividad PID2019-108573GB-C21 Ministerio de Economía, Industria y Competitividad SEV-2017-0706 Ministerio de Economía, Industria y Competitividad MAT2016-77100-C2-1-P Ministerio de Economía y Competitividad RTI2018-098537-B-C21 Ministerio de Economía y Competitividad SEV-2015-0496 Agència de Gestió d'Ajuts Universitaris i de Recerca 2017/SGR-579
Note:	Altres ajuts: ICN2 is funded by the CERCA programme/Generalitat de Catalunya.
Rights:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, i la comunicació pública de l'obra, sempre que no sigui amb finalitats comercials, i sempre que es reconegui l'autoria de l'obra original. No es permet la creació d'obres derivades.
Language:	Anglès
Document:	Article ; recerca ; Versió publicada
Subject:	Metal-insulator transitions ; Phase coexistence ; Martensitic transitions ; Local strain fields
Published in:	Acta Materialia, Vol. 220 (Nov. 2021) , art. 117336, ISSN 1359-6454

DOI: 10.1016/j.actamat.2021.117336

11 p, 2.6 MB

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Research literature > UAB research groups literature > Research Centres and Groups (research output) > Experimental sciences > Catalan Institute of Nanoscience and Nanotechnology (ICN2)
Articles > Research articles
Articles > Published articles