Synthesis and optical properties of flower-like ZnO nanorods by thermal evaporation method

Flower-like ZnO nanorods have been synthesized by heating a mixture of ZnO/graphite powders using the thermal evaporation and vapor transport on Si (1 0 0) substrates without any catalyst. The structures, morphologies and optical properties of the products were characterized in detail by using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and Raman spectroscopy. The synthesized products consisted of large quantities of flower-like ZnO nanostructures in the form of uniform nanorods. The flower-like ZnO nanorods had high purity and well crystallized wurtzite structure, whose high crystalline quality was proved by Raman spectroscopy. The as-synthesized flower-like ZnO nanorods showed a strong ultraviolet emission at 386 nm and a weak and broad yellow-green emission in visible spectrum in its room temperature photoluminescence (PL) spectrum. In addition, the growth mechanism of the flower-like ZnO nanorods was discussed based on the reaction conditions.

Research highlights▶ In this article, we synthesized flower-like ZnO nanorods on substrates by a simple thermal evaporation process without any catalysts or templates. ▶ The PL spectrum showed that a sharp and strong UV emission band located at 386 nm together with a weak and suppressed yellow-green emission band. ▶ The high intensity ratio of the UV peak to the defect emissions indicates fairly good crystallization of flower-like ZnO nanorods. ▶ The Zn liquid droplets function as catalyst plays an important role in the self-catalytic VLS growth process of flower-like ZnO nanorods at low temperature deposition region. ▶ The possible growth mechanism of these structures is investigated.