Strong strain gradients and phase coexistence at the metal-insulator transition in VO2 epitaxial films
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 finge...
| Autores: | , , , , , , |
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| Tipo de recurso: | artículo |
| Fecha de publicación: | 2021 |
| País: | España |
| Institución: | Universitat Autònoma de Barcelona |
| Repositorio: | Dipòsit Digital de Documents de la UAB |
| Idioma: | inglés |
| OAI Identifier: | oai:ddd.uab.cat:268421 |
| Acceso en línea: | https://ddd.uab.cat/record/268421 https://dx.doi.org/urn:doi:10.1016/j.actamat.2021.117336 |
| Access Level: | acceso abierto |
| Palabra clave: | Metal-insulator transitions Phase coexistence Martensitic transitions Local strain fields |
| Sumario: | 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. |
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