Thin film transfer for the fabrication of tantalum nitride photoelectrodes with controllable layered structures for water splitting.

The fabrication of semiconductor films on conductive substrates is vital to the production of high-performance electrodes for photoelectrochemical (PEC) water splitting. In this work, a thin film transfer method was developed to produce Ta3N5 film photoanodes for PEC water oxidation. Phase-pure Ta3N5 thin films were formed on inert Si substrates via magnetron sputtering of Ta films, followed by oxidation and subsequent nitridation in a flow of gaseous NH3. The resulting porous Ta3N5 films were uniformly transferred from the Si substrates using metallic layers that allowed ohmic contact at the Ta3N5 film/metal interface. This film transfer method enables control over the film thicknesses and layered structures of the Ta3N5 photoanodes. Following modification with a Co(OH) x layer acting as an oxygen-evolution catalyst, a Ta3N5 photoanode with a NbN x interlayer exhibited a photocurrent of 3.5 mA cm-2 at 1.23 V vs. RHE under a simulated AM 1.5G light, a value 1.7 times that generated by a photoanode without interlayers. The present film transfer method is potentially applicable to the development of semiconductor thin films for efficient PEC energy conversion.