Journal of Materiomics

Journal of Materiomics

Volume 7, Issue 4, July 2021, Pages 657-664
Journal of Materiomics

Opinion paper
Surface morphology-optical properties relationship in thermochromic VO2 thin films obtained by air oxidation of vanadium nitride

https://doi.org/10.1016/j.jmat.2020.12.005Get rights and content
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Highlights

  • Thermochromic VO2 thin films have been obtained by air oxidation of VN films.

  • The VO2 morphology is strongly dependent on the annealing temperature.

  • The annealing duration has to be optimized to guarantee VO2 films exempt of V2O5 phase.

  • The emissivity switch of the VO2 films is independent of the film morphology.

Abstract

In this paper, vanadium nitride (VN) thin films have been deposited on Al substrates by reactive magnetron sputtering. Thermochromic VO2 films have been obtained by air oxidation of VN samples performed at three temperatures (450, 525 and 550 °C) at various durations (lower than 50 min). X-ray diffraction and Raman spectrometry of the VN oxidized films indicate that VO2 and V2O5 are the only phases produced during the oxidation process. Vanadium dioxide is the first oxide formed. It coexists with VN in a long period at 450 °C or suddenly disappears at 525 and 550 °C. Whatever the temperature, V2O5 is exclusively detected after the total oxidation of VN. This oxide is detrimental to the thermochromic performance of films. The emissivity-switching properties of the oxidized films were analyzed by infrared camera in the 7.5–13 μm range. The comparison among all the samples exhibiting a thermochromic behavior shows that the maximum emissivity switch is independent of the oxidation temperature and the surface morphology of the samples. These results could open a new strategy in the investigation of VN oxidation as a method to obtain VO2, along with an insight into the correlation between surface morphology and optical properties.

Keywords

Vanadium dioxide
Vanadium nitride
Thermochromism
Optical properties
Air oxidation

Cited by (0)

Alexis Carlos García Wong obtained a B.Sc in Physics (Summa Cum Laude) from the University of Havana, Cuba in 2012. He received a M.Sc in Physics from the Federal University of Pernambuco, Brazil in 2016. He is currently finishing a PhD in Materials Science at the Institut Jean Lamour, France. His research focuses on magnetron sputtering deposition, fabrication and characterization of thermochromic materials.

Denis Mangin obtained his B.S. in computer science from I.U.T. Charlemagne, Nancy in 1990 and M.S. from Conservatoire National des Arts et Métiers in 1995. From 1991 to 2013 he worked in Centre de Recherches Pétrographiques et Géochimiques, Vandoeuvre les Nancy, as an analyst on SIMS intruments (Caméca ims3f, ims1270 and ims1280). Since 2013 he is working as an engineer on a Caméca SIMS ims 7f in Institut Jean Lamour, Nancy.

Sylvie Migot was born in 1968. She obtained a Master in materials science in 1993. She worked during 21 years as technician at the University of Lorraine. She prepared samples and characterized them by X-Ray (Laue, Berg-Barret and Lang), optical microscopy, scanning electron microscopy (with EDS, EBSD) and transmission electron microscopy (with EDS). Now she is Engineer of the CNRS and she is responsible of two equipments in the Institut Jean Lamour: TEM Philips CM200 and SEM-FIB Helios Nanolab 600i. She is co-author of 55 papers.

Dr. Jean-François PIERSON is Professor of Materials Chemistry at the University of Lorraine (Ecole des Mines), Nancy, France. He obtained his PhD in 1997. He is currently the head of the department Chemistry and Physics of Solids and Surfaces at the Institut Jean Lamour (UMR CNRS 7198). His research is focused on the development of oxides and nitrides thin films for energy applications. He has published approx. 140 papers in peer-review journals and 6 patents.

Peer review under responsibility of The Chinese Ceramic Society.