Fluorine-Assisted Low-Temperature Synthesis of GaN:ZnO-Related Solid Solutions with Visible-Light Photoresponse

Wurtzite-structured Ga_1-Zn(N,O,F) was successfully synthesized by nitridation of mixtures of a Ga-containing oxide and ZnF₂. The addition of ZnF₂ lowered the nitridation temperature for the synthesis of Ga_1-Zn(N,O,F) to 823 K, even when bulk ZnGa₂O₄ was used as a paired precursor. This lowering of the synthesis temperature was ascribed to the enhancement of nitridation through the addition of fluorine. The low-temperature nitridation achieved by the addition of fluorine suppressed the volatilization of Zn compared with that during the synthesis of a GaN:ZnO solid solution by a conventional high-temperature ammonolysis reaction. The higher concentration of Zn, as well as the higher N concentration in Ga_1-Zn(N,O,F) achieved through the fluorine-assisted nitridation, led to a redshift of the absorption edge of Ga_1-Zn(N,O,F) to 560 nm compared with that of GaN:ZnO synthesized by the conventional ammonolysis reaction. The visible-light absorption of Ga_1-Zn(N,O,F) can be used to drive the photoelectrochemical oxidation of water.