Transparent Substrates for Plasmonic Sensing by Lithography-Free Fabrication

Anil Haraksingh Thilsted

    Research output: Book/ReportPh.D. thesis

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    Abstract

    This Ph.D. thesis presents fabrication and optimization of transparent plasmonic substrates that can be used for biological and chemical sensing by surface enhanced Raman spectroscopy (SERS) sensing and localized surface plasmon resonance refractive index (LSPR RI) sensing. These substrates are: glass nanopillars with gold caps for SERS sensing; polymer nanopillars with gold caps for SERS sensing; transferred gold nanocaps to polymer foil for SERS sensing; and glass hollow-core nanocylinders with gold nanorings for LSPR RI sensing.
    These substrates were achieved using lithography-free fabrication methods, and resulted in large-area, high throughput and low cost production techniques. The fabrication techniques consisted of using aluminum patterned areas and reactive ion etching (RIE) to achieve nanopillars or nanocylinders in glass; using RIE to achieve nanopillars in silicon as a mould for polymer injection; and using RIE and imprinting to transfer gold nanocaps to a polymer foil.
    The SERS substrates showed a 91%, a 94% and 8% Raman signal intensity compared to gold-capped silicon nanopillars for the glass nanopillars, the polymer injected nanopillars and the transferred gold nanocaps, respectively. As the substrates were transparent, measurements from the backside were possible, showing a 44%, 1:7% and 71% Raman signal intensity in comparison to the measurements from the front, for the glass nanopillars, the polymer injected nanopillars and the transferred metal nanocaps, respectively.
    For LSPR, the glass hollow-core nanocylinders with suspended gold nanorings showed a sensitivity of 658 nm RIU{1 with a gure-of-merit of 10. The LSPR wavelengths could be shifted by tuning the plasma etching parameters.
    Due to the low electrical conductivity of glass substrates, electrodes could be incorporated onto the glass nanopillars, resulting in a device that could be used for both electrochemistry and SERS measurements. The polymer injected nanopillars used an industrial high throughput and robust fabrication technique. The substrate was integrated into high throughput fluidic devices for in-situ SERS measurements. The fabrication methods presented in this Ph.D. thesis are scalable, high throughput and low cost, and result in high performance plasmonic surfaces for sensing.
    Original languageEnglish
    PublisherDTU Nanotech
    Number of pages158
    Publication statusPublished - 2016

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