Tunable Surface-enhanced Raman Scattering (SERS) from nano-aperture arrays




Zhang, Xiaoqiang

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Research work on fabricating organized and reproducible SERS substrates has been done in this thesis. Nano-aperture arrays with circular, bow-tie and cross bow-tie shapes were fabricated by using FIB milling. These arrays were imaged under SEM and their parameters were measured. The optical transmission properties of these arrays were measured by white light transmission. It was found that the shape of the nano-aperture could determine these arrays’ abilities to support SPR. Different shapes would give different SPR modes and generated optical transmission peaks at varied wavelengths. For nano-aperture array with identical shapes, the varied parameters, such as periodicity or tip-to-tip distances, would affect the position of the transmission peaks. Slight increase or decrease of these parameters can be manipulated to adjust the peak positions, catering to the best resonance of the excitation laser used in Raman spectroscopy. The enhancement properties of these arrays as SERS substrates were measured by Raman spectroscopy. Different SERS enhancement properties could be found across different shaped nano-aperture arrays and cross bow-tie nano-aperture arrays give the best SERS enhancement. For nano-aperture array with identical shapes, the varied parameters would affect its ability of SERS enhancement. Near field simulations were carried out in order to explain the relationship of the SERS results and these arrays’ SPR ability. Electrochemical study on these ordered nano-aperture arrays was also carried out in this thesis.



SERS, nano-aperture, arrays