Surface Plasmon Mediated Optical Manipulation For Emission And SERS Application

Nowadays, metal nanostructures, owing to its special surface plasmon resonance (SPR) property and various potential applications, have gained much attention and been developed as an important research area. The SPR effect is well known as the coherent oscillation of the electrons near the surface of metal nanostructures when interacting with the incident light at a specific wavelength, and its resonance frequency is sensitive to the material’s type, size, shape and the exterior dielectric environment. A strong local field enhancement would be induced near the surface of the metal nanostructures when SPR phenomenahappens, and can be as high as103times on certain spots or regions. This enhanced local field, also known as the photon density of states (DOS), can be used to improve the spontaneous radiative recombination rate in semiconductor materials and thus the emission efficiency.Also, the strong local field can be applied to enhance the Raman scattering of moleculars near the surface of metal nanostructures, which is well known as the SPR based Surface Enhanced Raman Scattering (SERS) effect. On the other hand, the enhanced light scattering effect in far field due to the SPR effect has been widely used to enhance the light trapping on solar cells or light extraction on light emitting devices (LED).So, it can be concluded that the well-controlled SPR assisted light manipulation properties on the precisely designed metal nanostructures are the fundamental basis for above mentioned applications. However, up to now, in order to achieve required LSP resonance frequencies and the corresponding local field enhancements, limited fabrication methods still hinder the successful configuration of suitable metal nanostructures, especially to realize LSP resonances and local field enhancements in deep UV region, and multiple plasmonic resonances within extended broadband light region. Futhermore, the inside enhancement mechanisms of surface plasmon enhanced light emission and scattering effect still need to be investigated systematically.In this thesis, with the concern of above metioned issues existing in SPR assisted light manipulation and its practical applications like emission enhancement and SERS detecting, comprehensive fundamental investigations and reacerches have been carried out as following:Firstly, various kinds of nano-fabricating techniques have been developed to prepare size and morphology controllable metal nanostructures, and thus to realize adjustable LSPR frequencies ranging from deep UV to near-infrared region. Also, by utilizing the specific metal-semiconductor composite nanostructures, multiple plasmonic resonances have been realized and a broadband SPR based light manipulation was proposed. The nanosphere lithography (NSL) techniques, template based methods and thermal-annealing processes will be introduced to produce the metal nanostructures or metal-semiconductor nanostructures with different morphologies. RIE etching, solution heating, film thickness change and other related adjusting methods were used to control the size and distribution of the fabricated nanostructures. The LSPR properties as well as the light manipulation abilities of the prepared nanostructures also were systematically investigated by the spectroscopic characterizations and FDTD simulation.Furthermore, the as-fabricated metal nanostructures exhibiting adjustable LSPR frequencies and local field enhancements have been applied to the emission enhancements of semiconductor materials and SERS detection, and also used to verify the superior light manipulation abilities on these metal nanostructures. UV or deep UV light emission enhancements have been accomplished on ZnO or AlGaN multiple quantum well (MQW) structures decorated with LSPR-frequency-adjustable metal nanoparticles, and the corresponding mechanisms, including emission channel, enhancement ratio, defect emission suppressing, LSPR band dependence and other emission characters influenced by the SP-exciton coupling process, charge transfer process, surface modification and so on, have been systematically investigated as well. Moreover, the prepared unique metal-semiconductor nanostructures were successfully demonstrated as high sensitive SERS substrate. The physical and chemical enhancement mechanisms were further studied in more details by means of establishing the metal-semiconductor energy band model assisted and FDTD simulation.The final part of the thesis will introduce a kind of metal/semiconductor composite cavity structure with the aim to realize multiple LSP resonances showing broadband light manipulation properties. The strongly enhanced local field originated from the inter-coupling of plasmonic cavities has been verified by the high sensitive SERS detecting and the further high efficient photocatalytic reactions evidence the multiple palsmonic resonance mediated broadband light manipulation.