ZnO nanocrystals synthesized by evaporation of Zn in microwave plasma torch in terms of mixture ratio of N2 to O2

Abstract

Zinc oxide (ZnO) nanocrystals synthesized by an atmospheric microwave plasma torch are characterized in terms of the mixture ratio of N2 and O2 in the torch gas. Zinc (Zn) granules as a source material placed on the plasma reactor were evaporated and oxidized to ZnO immediately as soon as Zn granules were in contact with the plasma torch flame. The samples obtained from the different gas mixtures were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), x-ray photoelectron spectroscopy (XPS), and photoluminescence (PL). As the N2 content in the gas mixture increased to 93.6%, the aggregates or clusters of ZnO crystals were synthesized without nanorod-like and multipod-like structures. Especially, ZnO crystals synthesized in the N 2 content of 55.6% mainly revealed the tripod and tetrapod. Also, the visible to ultraviolet (UV) intensity ratio in the PL analysis was increased with increasing of the N2 content, revealing that the aggregated ZnO crystals have the high concentration of oxygen vacancies. © 2006 American Institute of Physics.