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

Abstract

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.