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Title: Large area plasmonic structure fabrication and tuning of surface plasmon resonance
Keywords: surface plasmon resonance, lasr interference lithography, colloidal lithography, large area, plasmonic structure, bimetallic structure
Issue Date: 27-Mar-2010
Citation: LIU CAIHONG (2010-03-27). Large area plasmonic structure fabrication and tuning of surface plasmon resonance. ScholarBank@NUS Repository.
Abstract: Plasmonics has attracted the great research interest of a wide range of scientists due to its extensive applications in the fields of novel optical devices, sensing applications, light generation and spectroscopy. Currently, numerous researches are being carried out to investigate the plasmonic properties of various nanostructures with different shapes and constituent materials. The research reported in this thesis mainly aims to fabricate large-area metallic nanostructures and to investigate the tunability of SPR by bimetallic layers. Both laser interference lithography (LIL) and colloidal lithography are applied to fabricate large area plasmonic nanostructures. LIL has the advantages of being a non-contact process in air and is able to achieve large-area and maskless nanolithography at a high speed with low system investment. Around centimeter square periodic metal structures can be achieved by the LIL technique. Single layer Au and Ag/Au bimetallic layer nanodot arrays are fabricated by LIL followed by electron beam deposition and lift-off processes. Colloidal lithography adopts a simple and flexible self-assembly process using latex microspheres to produce a particle mask for metal deposition. A large area of ~ 0.8 millimeter square nanoparticle array can be achieved. Various types of nanoparticle arrays with different particle sizes or metal film thicknesses are successfully produced by the colloidal lithography technique. The physical and optical properties of these fabricated nanostructures are examined by OM, SEM, AFM and UV-Vis spectroscopy. To the best of our knowledge, there is yet no extensive research on the surface plasmon behavior of hybrid nanodots localized on quartz substrates. In this thesis, we focus on gold and silver bimetallic nanostructures and study the SPR peaks of these thin films and dot arrays. It is observed that for gold thin film on quartz substrate, the optical spectral peak is blue shifted when a thin silver film is coated over it. Compared to the plasmon band in the single metal gold dot array, the bimetallic nanodot array shows a similar blue shift in its spectral peak. These shifts are both attributed to the electromagnetic interaction between the gold and silver atoms. A simplified spring model is adopted to qualitatively explain the phenomena observed. This study offers a novel way for hybrid materials to be used to tune the SPR peaks of noble metals. Moreover, several variables, such as consistency of monolayer, particle size and metal film thickness on plasmonic effect of these fabricated nanostructures are studied in relation to tuning the SPR peaks. The SPR peak shifts observed in the optical transmission spectra are qualitatively explained using various interaction models. These characterizations have the potential to allow us to extend the applications incorporating plasmonic resonance tuning.
Appears in Collections:Master's Theses (Open)

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