Anatase TiO2 deposited at low temperature by pulsing an electron cyclotron wave resonance plasma source

B Dey,S Bulou,T Gaulain,M Richard-Plouet,P Choquet,A Granier,A Goullet,W Ravisy

doi:10.1038/s41598-020-78956-1

Abstract

Photocatalytic surfaces have the potentiality to respond to many of nowadays societal concerns such as clean H2 generation, CO2 conversion, organic pollutant removal or virus inactivation. Despite its numerous superior properties, the wide development of TiO2 photocatalytic surfaces suffers from important drawbacks. Hence, the high temperature usually required (> 450 °C) for the synthesis of anatase TiO2 is still a challenge to outreach. In this article, we report the development and optimisation of an ECWR-PECVD process enabling the deposition of anatase TiO2 thin films at low substrate temperature. Scanning of experimental parameters such as RF power and deposition time was achieved in order to maximise photocatalytic activity. The careful selection of the deposition parameters (RF power, deposition time and plasma gas composition) enabled the synthesis of coatings exhibiting photocatalytic activity comparable to industrial references such as P25 Degussa and Pilkington Activ at a substrate temperature below 200 °C. In addition, to further decrease the substrate temperature, the interest of pulsing the plasma RF source was investigated. Using a duty cycle of 50%, it is thus possible to synthesise photocatalytic anatase TiO2 thin films at a substrate temperature below 115 °C with a deposition rate around 10 nm/min.

Highlights

Photocatalytic surfaces have the potentiality to respond to many of nowadays societal concerns such as clean H2 generation, CO2 conversion, organic pollutant removal or virus inactivation
In addition to the optimisation of the main experimental parameters, we especially focus on the pulsing of the Electron Cyclotron Wave Resonance (ECWR) plasma source in order to perform the deposition at low substrate temperature
We presented an ECWR PECVD process able to readily deposit well crystallized anatase T iO2 without the need of any post-treatment

Summary

Introduction

Photocatalytic surfaces have the potentiality to respond to many of nowadays societal concerns such as clean H2 generation, CO2 conversion, organic pollutant removal or virus inactivation. The former comprises hydrothermal, electrodeposition, anodization, spin-coating, dip-coating and sol–gel m ethods[8] They represent a cost effective way to synthesise titania layers, wet processes either include a high temperature and/or long post process treatment to get a well crystallized material[9]. Dry vacuum processes such as Physical Vapour Deposition (PVD). Chemical Vapour Deposition (CVD) require a step of heating above 200 °C, either during the deposition process or post-deposition (calcination or annealing) This makes them incompatible with the deposition on thermally labile substrates, namely stiff and flexible polymers. Up to now, most fundamental and applied studies on TiO2 thin film deposition synthesis concerned deposition on glass, which allows deposition temperatures up to 400 °C

Methods

Results

Conclusion