Study On The Preparation And Optical Property Of Flowerlike ZnO Micro-nanostructure By Water Bath Method

ZnO is an important II-IV semiconductor material due to its direct, wide band-gap (3.37 eV), large excitation binding energy (60 meV) and interesting properties, such as near-UV emission, transparent conductivity, piezoelectricity and electronic property. For the versatile properties above, it has great potential applications in transparent electrode, piezoelectric, varistors, acoustic wave devices and solar cells.Currently, ZnO films, dopping, and ZnO nanostructures are three main research aspects. As for nanostructures, although great progress has been made, the application of ZnO nanometer devices still have a long way to go. As is known to all, material properties are dependent on their structures, while preparation methods and processes have great effects on structures and properties. So, in order to study the application of ZnO nanometer device, it is crucial to obtain high quality ZnO nanomaterials by using non-metal catalyst or catalyst-free method and control the morphology of the nanostructures.In this paper, flowerlike ZnO micro-nanostructures were fabricated from aqueous solution in the zinc?ethylenediamine (EDA)?hexamethylenetetramine (HMT) tertiary system via simple water bath method. Effects of different factors, such as reaction concentration, temperature, time, HMT and EDA on structures and morphology have been discussed. The photoluminescence spectrum and ultra-violet and visible spectrum have also been characterized. In addition, flowerlike ZnO arrays have been synthesized on glass slide by water bath method, and we also studied sulfur doped flowerlike ZnO arrays. The main results are as follows:(1) The obtained ZnO micro-nanostructures exhibit well-defined flowerlike morphology, hexagonal wurtzite structure and strong UV photoluminescence. The petals, which present hexagonal pyramidal feature, are single crystal and preferentially growing along [0001] direction.(2) Effects of concentration, temperature, time, EDA and HMT were investigated. It shows that the EDA is crucial to the formation of 3D flowerlike ZnO by selective adsorption and site-specific second nucleation, while HMT have an effect on the petal morphology. Moreover, lower concentration leads to smaller size and lower crystallization quality; lower temperature makes nuclei liable to aggregate and not completely growth; and relatively longer reaction time makes petals dissolve. In addition, the growth process of 3D flowerlike ZnO was also discussed.(3) PL spectrum of the micro/nano flowerlike ZnO present two emission peaks. One is strong sharp UV emission located at 365 nm, the other is weaker broad UV-purple emission nearby 406 nm. Different reaction conditions (solution concentration, growth temperature, reactant ratio) also have influence on PL property .(4) S-doped flowerlike ZnO arrays presents rough surface and higher uniformity and orientation compared to un-doped flowerlike ZnO arrays. Besides, UV emission becomes weak and green emission peak appears after S-doped.