Preparation Of Nano Ag/ZnO Compound Materials And Study On The Character Of Photoluminescence Enhancement

ZnO, with a wide band gap 3.37eV, has an exciton binding energy 60 meV which is lager than the thermal energy 26 meV at room temperature. So ZnO is much more suitable for the UV laser material at room temperature or even higher, comparing to ZnSe(22meV), ZnS(40meV) and GaN(25meV). In 1996, a paper about the UV emission of ZnO microcrystal film at room temperature brought a renewed interest on the ZnO, especially in the field of semiconductor laser device. During the research on ZnO, the high lasing threshold confines the development of ZnO as laser material. Recent research on some nano metal material, such as Ag nano particles, brings a great help on this difficulty. Under the excitement of light field, the surface of the nano metal particles will produce Local Surface Plasmon Polaritons (LSPs), a kind of electric field which is about 1014 stronger than the incident light. Therefore, we can prepare the composite material of nano metal particles and ZnO in order to reduce the lasing threshold by using the character of LSPs on nano metal particles.There are two parts of dissertation. The first part is the research on the structure properties and photoluminescence properties of ZnO/Ag composite film. The second part is about the research on the photoluminescence properties of composite materials of ZnO nanorods and Ag nanoparticles.1. photoluminescence properties of composite film of ZnO/AgWe have sputtered Ag and ZnO film on Si(111) substrate, and annealed the samples in air condition at the 750℃for one hour. The results of XRD and FESEM indicate that Ag film will condense into nano particles and diffuse in the composite film during annealing. The diffusion will bring a great damage to the qualities of ZnO and leave a great amount of"holes"in the composite film. The more Ag in composite film, the bigger damage to the quality of ZnO. The PL of the samples indicate that the photoluminescence intensities of ZnO/Ag(5nm) and ZnO/Ag(10nm) are stronger than the pure ZnO film with same thickness after annealed under the same conditions. Especially, the intensity ratio of ZnO/Ag(10nm) is up to 12.3. We attribute this enhancement to the LSP of Ag nano particles. However, there are also several samples with weakened photoluminescence, such as ZnO/Ag(15nm),ZnO/Ag(30nm) and ZnO/Ag(55nm). We attribute this weakening to the lower qualities of ZnO, which was brought by the diffusion of Ag nanoparticles during annealing. On one hand, the LSP of Ag nano particles will enhance the photoluminescence of ZnO. On the other hand, the quality of ZnO will be great damaged by Ag nano particles during annealing, and the photoluminescence of ZnO will be weakened as a result. These two parts will compete with each other to determine the photoluminescence of composite film.2. photoluminescence properties of composite material of ZnO nanorods/Ag nanoparticlesWe have prepared the ZnO nanorods with high quality by using solution method and sputtered a layer of 40nm Ag film on the surface of ZnO nanorods. The result of FESEM indicates that the morphology of Ag on nanorods is nanoparticles rather than film. The PL of the composite material shows that the intensity is also stronger than the sample of ZnO nanorods without Ag coated. We also attribute this phenomenon to LSP of silver nanopartiles. This will bring a great help to the development of composite material of ZnO and silver as UV laser materials.