TaOxNy Sputtered Photoanodes For Solar Water Splitting

A series of TaOxNy photoelectrodes were deposited on F:SnO2 (FTO) substrates by DC reactive sputtering at room temperature, under a mixture of Ar, N2 and O2. The effects of the O2 partial pressure during deposition (Po2) on the films crystallinity, their chemical composition, their morphology as well as their absorption and photoelectrochemical properties have been investigated. The increase of PO2 led to the modification of film crystallinity, which evolved from a semicrystalline Ta3N5 structure to an amorphous state. The increase of the Po2 also led to the increases of the oxygen content, of the bandgap energy and of the films roughness. Preliminary photoelectrochemical (PEC) investigations have been performed through current-voiltage measurements. An optimal Po2 has been highlighted, corresponding to a tradeoff between, on the one hand, the amorphization of the films -which degrades PEC performances - and on the other, the tuning of the chemical composition as well as of the bandgap energy