Controlled grain-size thermochromic VO2 coatings by the fast oxidation of sputtered vanadium or vanadium oxide films deposited at glancing angles

A. J. Santos*, B. Lacroix, M. Domínguez, R. García, N. Martin, F. M. Morales

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

An original, simple and cost-effective oxidation strategy to attain thermochromic vanadium dioxide thin films is reported. This two-step procedure comprises the initial deposition of DC magnetron-sputtered vanadium or vanadium oxide films by the combination of glancing angle deposition and, if needed, reactive gas pulsing process, followed by fast oxidation of such layers in air atmosphere at high temperatures. Thanks to the careful control of the thermal treatment parameters, and taking advantage of the superior reactivity of the high surface-to-volume porous deposited structures, the formation of pure VO2 (M1) layers was achieved. The comprehensive characterization of such oxidized systems by means of scanning electron microscopy, Raman spectroscopy and scanning-transmission electron microscopy techniques such as electron energy-loss spectroscopy, not only confirmed the presence of the VO2 (M1) phase, but also allowed to shed light on the key role that reaction time plays in the selective formation of vanadium dioxide films of adjustable grain size and crystallinity. The optimal conditions to stabilize thermochromic VO2 consists in using large deposition angles (85 °) and short oxygen pulses (≤ 2 s) during the growth, followed by fast and short thermal treatments (≤ 45 s with a heating rate of 42 °C s−1) in air atmosphere at 550 °C. The metal-to-insulator response of the accomplished VO2 layers was finally evaluated by means of temperature dependent Kelvin probe force microscopy measurements, evidencing surface potential drops at heating, greater than those reported in the literature to date for VO2 thin films.

Original languageEnglish
Article number101581
JournalSurfaces and Interfaces
Volume27
DOIs
StatePublished - Dec 2021
Externally publishedYes

Bibliographical note

Funding Information:
A. J. Santos would like to thank the IMEYMAT Institute and the Spanish Ministerio de Educación y Cultura for the concessions of grants (ICARO-173873 and FPU16–04386). The “Talent Attraction Program” of the University of Cádiz is acknowledged by supporting B. Lacroix contract code E-11–2017–0117214. University of Cádiz and IMEYMAT are also agreed by financing the mutual facilities available at the UCA R&D Central Services (SC-ICYT), the UCA projects reference “PUENTE PR2018–040″ and “PUENTE PR2020–003″, and the IMEYMAT project references “LÍNEAS PRIORITARIAS PLP2019120–3 and PLP2021120–1″. This work was supported by the Spanish State R&D project (Retos y Generación de Conocimiento) ref. PID2020–114418RB-I00/AEI/10.13039/501100011033. The regional government of Andalusia with FEDER cofunding also participates through the projects AT-5983 Trewa 1157178 and FEDER-UCA18–10788. M. Domínguez acknowledges financial support from the Spanish Ministerio de Ciencia e Innovación under project reference EQC 2018–004704-P FEDER 2014–2020, “Modernización del Servicio de Microscopía de Fuerza Atómica (AFM) del IMEYMAT”.

Funding Information:
A. J. Santos would like to thank the IMEYMAT Institute and the Spanish Ministerio de Educaci?n y Cultura for the concessions of grants (ICARO-173873 and FPU16?04386). The ?Talent Attraction Program? of the University of C?diz is acknowledged by supporting B. Lacroix contract code E-11?2017?0117214. University of C?diz and IMEYMAT are also agreed by financing the mutual facilities available at the UCA R&D Central Services (SC-ICYT), the UCA projects reference ?PUENTE PR2018?040? and ?PUENTE PR2020?003?, and the IMEYMAT project references ?L?NEAS PRIORITARIAS PLP2019120?3 and PLP2021120?1?. This work was supported by the Spanish State R&D project (Retos y Generaci?n de Conocimiento) ref. PID2020?114418RB-I00/AEI/10.13039/501100011033. The regional government of Andalusia with FEDER cofunding also participates through the projects AT-5983 Trewa 1157178 and FEDER-UCA18?10788. M. Dom?nguez acknowledges financial support from the Spanish Ministerio de Ciencia e Innovaci?n under project reference EQC 2018?004704-P FEDER 2014?2020, ?Modernizaci?n del Servicio de Microscop?a de Fuerza At?mica (AFM) del IMEYMAT?.

Publisher Copyright:
© 2021

Keywords

  • Eels spectroscopy
  • Fast oxidation
  • Glancing angle deposition
  • KPFM
  • Metal-insulator transition
  • Raman spectroscopy
  • Transmission electron microscopy
  • VO thin film

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