A research team led by Prof. GONG Jianru from the National Center for Nanoscience and Technology (NCNST) of the Chinese Academy of Sciences (CAS), collaborating with Prof. XUAN Yimin from Nanjing University of Aeronautics and Astronautics and Prof. ZHANG Jing from Institute of High Energy Physics of CAS, studied the atomic arrangement matters in composition-tunable single-crystal (Ga_1-xZn_x)(N_1-xO_x) nanowires. The finding was published in Matter.

(Ga_1-xZn_x)(N_1-xO_x), a nonisovalent semiconductor alloy composed of GaN and ZnO, is known as the state-of-the-art photocatalyst for overall water splitting under visible light. However, the underlying mechanisms of composition dependent band-gap in (Ga_1-xZn_x)(N_1-xO_x) is still under intense debate, because of the ambiguous atomic-scale element distribution.

Herein, the team synthesized a series of composition-tunable single-crystal (Ga_1-xZn_x)(N_1-xO_x) nanowires via a customized chemical vapor deposition (CVD) strategy. In distinct contrast to several days of traditional solid-state nitridation reactions, the researchers reduced the processing time down to 20 minutes.

The existence of a strong clustering tendency in the (Ga_1-xZn_x)(N_1-xO_x) nanowires was verified using X-ray absorption fine structure analysis in combination with ab initio multiple-scattering calculation. Meanwhile, the results demonstrated the relationship between the elemental distribution at atomic scale and band-gap variation in (Ga_1-xZn_x)(N_1-xO_x) solid solution system.

Furthermore, the researchers proposed an innovative evaluation method for the quantification of the degree of short-range order (SRO). They found a clustering tendency to enhance the statistical presence of the valence-matched Ga-N and Zn-O pairs, in (Ga_1-xZn_x)(N_1-xO_x) solid solutions.

In addition, it was verified that the strong SRO effect led to the formation of intracrystalline heterojunctions with type-II band alignments between the incorporated clusters and host material, causing a continuous degree in the band-gap of (Ga_1-xZn_x)(N_1-xO_x) nanowires with increasing ZnO content.

The vital role of atomic arrangement engineering in modulating the energy band structures will open up a new way to engineer band-gaps of alloy semiconductor catalysts for energy conversion applications.