Fabrication of plate-like Ta3N5 crystals through evaporation–deposition–re-evaporation of alkali halide fluxes onto tantalum substrates

Abstract

Ta₃N₅ nanostructured films have been explored as photoanodes for photoelectrochemical water splitting. Despite a number of efforts, it is still difficult to control the facet of single-crystalline Ta₃N₅, which directly affects the properties, due to its harsh growth conditions. In addition, the fabrication methods of Ta₃N₅ films involve complex multi-step procedures and/or require complicated equipment. In this study, we report on facile fabrication of plate-like Ta₃N₅ crystals with predominant {010} crystallographic planes covering the Ta substrate surface by flux growth under an ammonia gas flow. Among alkali halide fluxes (KF, KCl, and KI), KF emerged as an effective flux for the growth of Ta₃N₅ crystals. Combining KF and KI promoted further crystal growth, producing larger Ta₃N₅ crystals. The crystals were confirmed as single-crystalline by TEM. The crystal growth process and shape evolution in the flux were investigated and discussed.