A series of TaO x N y photoelectrodes were deposited on F:SnO 2 (FTO) substrates by DC reactive sputtering at room temperature, under a mixture of Ar, N 2 and O 2 . The effects of the O 2 partial pressure during deposition (P o2 ) on the films crystallinity, their chemical composition, their morphology as well as their absorption and photoelectrochemical properties have been investigated. The increase of P O2 led to the modification of film crystallinity, which evolved from a semicrystalline Ta 3 N 5 structure to an amorphous state. The increase of the P o2 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 P o2 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