sputter-deposited nanocristalline Ta$_3$N$_5$/TaON for the photoelectrolysis of water under sunlight exposition
Résumé
Ta$_3$N$_5$ is a material under investigation for photo-electrolysis of water. Up to now, a lot of effort has been devoted to synthesize this material by chemical routes, substituting nitrogen to oxygen inside Ta$_2$N$_5$ commercial particles by annealing under ammonia. Yellow or green TaON crystals with an ideal bandgap around 2.3eV are produced in the same way by annealing under nitrogen gas. This leads generally to quite large particles and then to a small photo-catalytic activity. Besides, little work has been done to investigate physical routes, for example vapor deposition processes for this kind of material despite certain advantages regarding the nanoscale roughness and the nano-morphology of deposited films. The reason for that might be the abundantly present $\delta$-TaN phase that forms over wide ranges of nitrogen molar fractions and is a metallic phase without a bandgap. Impeding the formation of these crystallites is thus a first step to prepare the route for sputter-deposited TaON or Ta$_3$N$_5$ films.
Domaines
Matériaux
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