Atomic Arrangement Matters: Band-Gap Variation In Composition-Tunable (Ga1-Xznx)(N1-Xox) Nanowires

We synthesized single-crystal (Ga1-xZnx)(N1-xOx) nanowires with fully tunable compositions (0 < x < 1) using a customized chemical vapor deposition strategy. Despite the uniform distributions of component elements at the nanometer scale, X-ray absorption fine structure analysis in combination with ab initio multiple -scattering calculation verified the existence of a strong clustering tendency, i.e., the energetic preference of the valence-matched Ga-N and Zn-O pairs, in the synthesized nanowires. The strong clustering tendency plays a dominant role in determining the electronic band structures of the nanowires, causing a continuous band-gap reduction with increasing ZnO content, which is interpreted via a type II band alignment among the intracrystalline heterojunctions formed between the incorporated clusters and the host material. This, ultimately, makes the sample with the highest ZnO content show the highest water-splitting activity. Atomic arrangement engineering will provide an additional tool for band-gap engineering of semiconductor alloys, greatly benefiting the development of new functional materials for energy conversion applications.