Atomic arrangement matters: band-gap variation in composition-tunable (Ga_1–xZn_x)(N_1–xO_x) nanowires

We synthesized single-crystal (Ga_1–xZn_x)(N_1–xO_x) 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. Alloying of semiconductors has gained a certain improvement in regulating their band structures for overall water splitting. However, little attention has been paid to the arrangement of the constituent elements at the atomic scale. Particularly, the variation in the band gap of a nonisovalent alloy photocatalyst, (Ga_1–xZn_x)(N_1–xO_x), following the change in composition, as well as the underlying mechanisms, has been under intense debate, because of the ambiguous atomic-scale element distribution. Here, using composition-tunable single-crystal (Ga_1–xZn_x)(N_1–xO_x) nanowires grown via chemical vapor deposition as a model system, we verify the energetic preference of the valence-matched Ga-N and Zn-O pairs in (Ga_1–xZn_x)(N_1–xO_x) alloys and demonstrate the dominant role of this clustering tendency in controlling their electronic band structures. These findings highlight the vital role of atomic arrangement engineering in modulating the band structures of semiconductor alloys. (Ga_1–xZn_x)(N_1–xO_x) nanowires with fully tunable compositions are synthesized via a customized chemical vapor deposition strategy. Atomic-scale element distribution is found to play a dominant role in determining the electronic band structure of (Ga_1–xZn_x)(N_1–xO_x) and causes a continuous band-gap reduction with increasing ZnO content. This finding highlights the vital role of atomic arrangement engineering in modulating the energy band structures of nonisovalent semiconductor alloys at the atomic scale.