Evolutions of defects and blue–green emissions in ZnO microwhiskers fabricated by vapor-phase transport

The corresponding evolutions of morphologies, defect-states and the PL properties have been employed to explore the defect-origins of visible emissions and growth mechanisms of microstructured ZnO. ZnO microtube and microrod whiskers were fabricated by non-catalytic vapor-phase transport using ZnO and graphite powders in air. The microstructures of the samples were studied in detail based on scanning electron microscopy (SEM), x-ray diffraction (XRD), energy-dispersive x-ray spectroscopy (EDX), and electron paramagnetic resonance (EPR). The main PL emission bands evolve from blue to green, which corresponds to that the main defect-states change from Zn interstitials (Zni) to O vacancies (VO). The formation of Zni under the high temperature zinc-rich vapor environment is crucial both for the blue emission and for the formation of the microtubes.

► ZnO micro tubes/rods were fabricated and the growth mechanism was examined.
► The tunable PL evolution was used effectively to clarify the defect origins.
► The instable Zni is crucial for the blue emission and the formation of microtubes.