Hydrothermal Synthesis of Core/Shell ZnO:Mn/Mn3O4 Nanowires

Vertically aligned ZnO nanowires were grown on SnO2:F-coated SiO2 substrates utilizing a low-temperature, seeded chemical bath method. Via additional hydrothermal postprocessing, Mn-doped nanowires were formed with and without a mixed polycrystalline MnO/Mn3O4 shell structure depending upon reagent concentrations. Electron microscopy techniques were implemented to quantify structure, composition, valence state, and morphology. Optoelectronic properties were also measured, including absorption spectra and photoluminescence. These properties were characterized as a function of the duration of both growth and doping time. Our results provide insights about the doping mechanism. ZnO band gaps were found to red-shift and were dependent on both doping time and ZnO growth time. Doping resulted in an increase in lattice spacing as well as an increase in intensity of photoluminescence defect bands.