Paper PS-TuP17
Atmospheric Plasma Deposition of Vanadium Oxide Thin Coatings on Cold and Heated Substrates

Tuesday, October 23, 2018, 6:30 pm, Room Hall B

Atmospheric plasma deposition of vanadium oxide thin coatings on cold and heated substrates

A. Remy¹, M.J. Gordon², F. Reniers¹

1. Université libre de Bruxelles, analytical and interfacial chemistry, Brussels, Belgium

2. University of California Santa Barbara, Department of Chemical Engineering

Vanadium oxides present interesting applications in thermochromic devices, electronic components, optoelectronics sensors, battery electrodes and catalysis. They can be synthesized by chemical vapor deposition (CVD) [1], or by magnetron sputtering [2]. In this research, we report, to the best of our knowledge, the first synthesis of vanadium oxide with a reactive atmospheric dielectric barrier discharge. This approach allows the direct synthesis of oxide layers on a wide variety of substrates, starting from an organometallic precursor in the vapor phase. Vanadium(V) oxytriisopropoxide vapours were injected in a DBD operating with argon as the main plasma gas. Variable quantities of the precursor and of oxygen (from 50 mL/min to 100 mL/min), operating as secondary reactive gas, were introduced in the discharge, and the plasma power was varied from 40 W to 60 W.

The coatings were deposited at room temperature, or, thanks to a new home made internal heating device, at higher substrate temperatures (ranging from 373 K to 573 K). Some coatings were post-annealed in air at 573 K.

The samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy and Infrared Spectrometry, in the IRRAS mode, and the electrical characteristics of the plasmas were studied by a high voltage probe. It is shown that the plasma power decreases with the introduction of oxygen, but remains virtually unchanged when the precursor is injected. Although, according to XPS, a significant amount of carbon still remains embedded in the final coating in the normal conditions of operation, typical IR bands for V₂O₅ at 1020 cm^-1 and 850 cm^-1 were observed for samples prepared with 50 mL/min of oxygen flow and at 300°C of sample temperature. This is confirmed by the oxidation state of vanadium (V5+), as observed by the XPS peak at 517.2 eV. The oxidation state seems to change with the conditions of the synthesis, starting from +5 for the original precursor, going down to +4, and then reaching +5 again for V₂O₅.

References

Acknowledgements : this work is supported by the Belgium EOS Nitroplasm project, and by the Walloon region projects Cleanair and Amorpho.