Self-assembled catalyst growth and optical properties of single-crystalline ZnGa2O4 nanowires

Uniform zinc gallate (ZnGa2O4) nanowires are successfully synthesized by a one-step simple thermal evaporation of a mixture of ZnO and Ga2O3 powders under controlled conditions. Its morphology and microstructures were determined by X-ray powder diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, and photoluminescence spectroscopy. The observations reveal that the as-synthesized ZnGa2O4 nanowires are single-crystalline with a cubic spinel structure, usually several tens of microns in length. The typical diameters of ZnGa2O4 nanowires range from 100 to 200 nm. The room-temperature photoluminescence spectrum of ZnGa2O4 nanowires features four luminescence peaks around 400, 503, and 686 nm, which are attributed to self-activation center of the octahedral Ga-O, electronic transitions of localized Ga3+ ion in the octahedral Ga-O, and single oxygen vacancies (V-O*), respectively. A self-assembled Ga catalytic vapor-liquid-solid (VLS) formation mechanism is also proposed to interpret the growth of ZnGa2O4 nanowires in our work.