Quasi-one-dimensional semiconductor nanomaterials have been stimulated a lot of interests for scientific research due to their unique physical and chemical properties and their potential applications in mesoscopic physics and nanodevices study.Among them

ZnO is one of the most promising oxide semiconductors.It has a direct wide band gap(3.37 eV) and a large exciton binding energy(60 meV).So it becomes a focus material for studies in short wave semiconductor laser nanodevices and visible photoelectronics devices.ZnO tetrapod nanostructures were synthesized by thermal evaporation of Zn powders under different flow rate of argon at 150

180

240 sccm

respectively.Scanning electron microscope(SEM)

transmission electron microscope(TEM) and photoluminescence(PL) were employed to determine the morphology and optical properties of the products.The results showed that argon gas flow rate influence on the ZnO morphology significantly.With the increasing of argon gas flow rate ZnO nanostructures changed from variety of nanostructures

including tetrapods

nanowires

nanosheets and nanodendritics to single uniform tetrapod nanostructure.The luminescence properties show that the emission intensity changes evidently along with the change of argon flow rates in the tube.The luminescence properties show that the UV emission become weaker and the blue emission become stronger

namely the ratio of the blue emission to the UV emission become bigger with the increasing of the argon flow rate.It is suggested that the oxygen vacancy is responsible for strong blue emission. The supposition is confirmed by the results that the blue light emission peaks disappear after the products are oxidized annealing in air at 700℃ and the blue light emission peaks appear again after the oxidized products are deoxidized annealing in H

2

at 700℃.Our experimental results provide the proofs that the blue light emission of nano-ZnO originates from oxygen vacancy.The experimental results are helpful for understanding the mechanism of the blue-green emission of nano-ZnO.Our investigations are significant in providing an effective way to enhance the intensity of blue light emission for various applications.