Controlled synthesis of defects-containing ZnO by the French process modified with pulsed injection and its luminescence properties

Zinc oxide (ZnO) nanoparticles containing oxygen vacancies were synthesized by the French process modified with pulsed injection of nitrogen. Zinc vapor was generated by evaporation of zinc foil and carried by a carrier gas to react with co-currently supplied air. During the reaction, nitrogen gas was injected in pulse, perpendicular to the flow direction of both zinc vapor and air. Low partial pressure of oxygen and turbulence caused by pulsed injection yielded uniform ZnO nanotetrapods that contained oxygen vacancies. The content of oxygen vacancies depended upon the characteristics of the pulse, i.e. flowing and non-flowing period of the gas, pulsing cycle time, and the supplied pressure of the injected gas. Strong correlation between the presence of oxygen vacancies and the intensity of green emission in the photoluminescence spectra of ZnO was also observed.