Dilute anion alloyed III-nitride nanowires for photoelectrochemical water splitting†

Abstract

Dilute anion alloyed III-nitride nanowires exhibited band gap reduction to around 2.4 eV with anion concentrations ranging from 5.6 to 8.8 at% and exhibited photoelectrochemical activity (∼8 mA cm⁻²@10 sun) under AM1.5 visible light. The nanowire electrode also exhibited photoelectrochemical activity using 470 nm wavelength light up to 8.75 mA cm⁻² at 10 sun (470 nm) radiation. The nanowires are grown using a plasma assisted vapor liquid solid (PA-VLS) technique using N₂ gas. The anion-alloyed antimony alloyed gallium nitride (GaSb_xN_1−x) and bismuth alloyed gallium nitride (GaBi_yN_1−y) wurtzite nanowires were grown using PA-VLS employing gold and copper as metallic seeds on a variety of substrates such as silicon, sapphire, and stainless steel. The PA-VLS technique allowed for increasing the antimony and bismuth incorporation levels with temperature as the dissolution of these species into the metals was favored with growth temperatures. Photoelectrochemical spectroscopy measurements showed light absorption of 620 nm photons in the case of the GaSb_0.056N_0.944 sample.