Plasma Assisted chemical vapor deposition of metal doped TiO2 thin film at low temperature – PATIO

Thin films of anatase titanium oxide were extensively studied due to their unique properties: photocatalysis under UV exposure, self-cleaning, anti-fogging, anti-bacterial… Various deposition processes compatible with deposition on glass were developed: sol-gel, sputtering or conventional chemical vapour deposition (CVD). They generally require a step of heating above 200°C, either during the deposition or post-deposition.
The recent development of flexible electronics and solar cells as well as antibacterial films has created a new demand for materials with transparent conducting or photocatalytic properties which can be deposited at temperature compatible with flexible polymers, typically below 80°C, which means the development of new materials and new processes. Metal doped anatase TiO2 films with tunable dopant content appear to be excellent candidates, as TCO or photocatalytic films. On the other hand, Plasma Enhanced Chemical Vapour Deposition (PECVD) is known to allow deposition of tunable materials at low temperature.
The objective of PATIO project is to develop a pulsed PECVD deposition technique, adapted for mass production of tunable metal doped crystallized titanium oxide layer on thermal sensitive flexible substrates.
Niobium and Tungsten doped anatase films will be deposited in low pressure radiofrequency plasmas upon injection of the vapours of Ti and dopant organometallic precursors mixed with oxygen. Preliminary results obtained in the consortium have shown that undoped TiO2 anatase films could be successfully deposited on thermally sensitive polymers by low pressure PECVD.
First, the injection of the dopant (up to 15 at.% in the film are targeted) will be optimized and its effect on the plasma will be studied. In parallel, the film composition and structure will be investigated by XPS, XRD and Raman spectroscopy. The effect of the ion energy on the film structure will be particularly studied.
Second, pulsed plasmas will be used to decrease the deposition temperature down to 80°C and below while maintaining the crystalline anatase structure of TiO2. The doped TiO2 films will be deposited on stiff and flexible polymers. Their TCO and photocatalytic properties will be measured. A special attention will be paid to the evolution of their conductivity upon bending.
Last, the dopant/process conditions with the best performance in terms of deposition temperature and properties (TCO or photocatalysis) will be transferred to a roll-to-roll reactor for dynamic deposition on rolling polymer foils.