| Summary: | 碩士 === 國立臺灣海洋大學 === 材料工程研究所 === 101 === Highly c-axis-textured ZnO-Ag composite thin films with var ious degrees of Ag addition were grown on c-axis-oriented sa pphire substrates by sputtering at 300 oC in this study. Str uctural analyses show that Ag nanoparticles seriously aggreg ated to form clusters with a high Ag content in the ZnO thin film. The ZnO thin-film surface was further roughened with A g addition; a markedly rugged surface morphology of the ZnO-Ag thin film was observed for the 13W Ag co-sputtered thin f ilm. The Ag addition in the ZnO thin film changed the densit y of native point defects in the ZnO prepared in an oxygen-d eficient ambient by sputtering. This caused different photol uminescence characteristics of the ZnO thin films with and w ithout the Ag addition. The blue emission band was found to dominate the pure and 3W Ag co-sputtered thin films. The UV emission band dominated the 9W Ag co-sputtered thin film. Ma ny ZnO-Ag composite grains clustered on the thin-film struc ture when the Ag-sputtering power level was increased to 13 W. This incurred more oxygen-related point defects in ZnO la ttices; thus, a green emission band was further enhanced.
On the other hand, ZnO-Ag composite layered thin films were grown on the Si substrates by alternating sputtering de posited ZnO and silver layers. The as-deposited ZnO thin fil m without an insertion of silver island layer is c-axis text ured. The insertion of silver island layer in the ZnO thin f ilms caused the microstructural changes. The highly c-axis-o riented crystallographic feature of the ZnO thin film is sli ghtly decreased and the surface of the ZnO thin film became quite rough. Comparatively, the PL results show the near-ban d-edge (NBE) emission peak intensity was enhanced up to appr oximately two orders for the 150 nm ZnO-Ag island layer/Si c omposite thin film; this is attributed to the plasmon resona nces of Ag nanoislands with the light. However, further incr eased the insertion number of silver island layer in the ZnO thin film caused the different sizes and distribution densit ies of Ag nanoislands on the Si substrate and ZnO surfaces; these suppressed the effectively resonant coupling between t he localized surface plasmon resonances with light. Instead, the visible emission band intensity was markedly increased b ecause of the deteriorated microstructure of the ZnO thin fi lm with the insertion of silver nanoisland layers.
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