Fabrication,Characterization And Application Of ZnO Nano-structure

ZnO draws great attentions as it possesses a lot of advantages for its special physical and chemical properties,and have great potential for a variety of applications,such as light emission diode,laser diode,sensors,transparent electrodes,solar cells and other optoelectronic devices.Tree-like ZnO/Si nanostructures can extend its specific surface area,increase its.light absorption ability,and also promote the charge separation,which can effectively reduce the recombination of electronic-hole pairs of composite,these excellent properties make ZnO/Si nanostructures have advantages in applications of sensing and photocatalyst.This work focuses on the application of tree-like ZnO/Si nanostructures,i.e.ZnO/Si nanotrees.The main contents are as follows:Firstly,the ZnO/Si nanotree structure is prepared.Si nanowire backbones are grown by the auxiliary metal etching method in AgNO3/HF solution,ZnO seed layer is coated by means of atomic layer deposition technology on Si nanowires,and ZnO nanowires are grown by hydrothermal method.We get a series of ZnO/Si samples by changing the etching time and growth time of Si backbones and ZnO nanowires respectively.Through the study of optical properties of ZnO/Si nanostructures,we observed the band edge emission and defect luminescence of ZnO in the photoluminescence spectrum.In the sense testing,the sensitivity of ZnO/Si nanostructure is greater than the pure Si nanowires or ZnO nanowires,it can reach 1x10-8mol/L.When ZnO/Si nanotree structure act as semiconductor photocatalyst,it is used to degrade methylene blue and rhodamine organic solution under the UV lamp,respectively.In order to enhance the catalyst activity and stability of ZnO/Si nanotrees,the layer of TIO2,Ag,TiO2/Ag and Ag/TiO2 double layers are coated.The results showed that the activity of samples with Ag layer are increased.But only in the experiment of degrading rhodamine solution,the sample with TiO2 layer has improved the stability of photocatalysis.For the samples with TiO2 and Ag double layers,photocatalytic activity and stability has nothing to do with the sequence of TiO2 and Ag layer,but in the degradation of rhodamine solution,photocatalytic activity and stability associated with the coating sequence of TiO2 and Ag.In addition,ZnO film grown on hexagonal boron nitride(h-BN)is fabricated by atomic layer deposition in this thesis.The influence of growth temperature and thickness of ZnO film are studied.It is found that the morphology of ZnO film presents a slender or lamellar structures when the growth temperature is 150?,and when the temperature rises to 250 ?,grains size are bigger and show more regular.When the thickness of film is thin,the surface have some big clusters,along with the increase of thickness,grain size increases and clusters disappear gradually.These clusters are likely located in the edge or corner of the h-BN monolayer,it shows the precursors preferentially nucleate at the h-BN edge or corner.In the photoluminescence spectrum,it is observed the strongest emitting peak in the sample with 450 growth cycles.We associated the changes of morphological and optical properties to the hexagonal monolayer structure of h-BN,and the strain effects induced by the lattice mismatch between ZnO and substrates.