AbstractsBiology & Animal Science

Large-area low-cost fabrication of complex plasmonic nanostructures for sensing applications

by Jun Zhao

Institution: University of Stuttgart
Department: Fakultät Mathematik und Physik
Degree: PhD
Year: 2015
Record ID: 1110389
Full text PDF: http://elib.uni-stuttgart.de/opus/volltexte/2015/9980/


In this thesis, we introduce hole-mask colloidal lithography and nanosphere lithography techniques for low-cost nanofabrication of large-area (about 1 cm^2) plasmonic nanostructures with different complex shapes. For the first one, we use thin film PMMA-gold hole-masks, which are first prepared with polystyrene colloids, combined with following tilted-angle-rotation evaporation to fabricate large-area randomly deposited plasmonic nanostructures. For the second one, we use hexagonal close-packed polystyrene nanosphere monolayers directly as evaporation masks to fabricate large-area periodic plasmonic nanostructures. We describe the fabrication process step by step, and manufacture a variety of different plasmonic nanostructures for different sensing applications. For example, we use split-ring-resonators for antenna-assisted surface-enhanced infrared absorption measurements to detect monolayer molecules with an up to 20000-fold enhancement factor. We also utilize asymmetric double split-ring- resonators for localized surface plasmon resonance sensing with experimental sensitivities of up to 520 nm/RIU and figures of merit up to 2.9. Furthermore, we investigate plasmonic oligomers consisting of touching triangular building blocks, which show fundamental modes, higher-order modes, as well as Fano resonances due to coupling between bright and dark modes within the same complex structures. Large-area low-cost direct contact Au-Pd hydrogen sensors are demonstrated, which show much improved spectral shifts as large as 30 nm upon hydrogen exposure. Additionally, we improve hole-mask colloidal lithography for three-dimensional and multishape fabrication. With multiple repetitions of hole-mask lithography, single-layer metasurfaces with complex, multi-shape plasmonic nanostructures can be created that exhibit desired optical functionalities. Large-area and low-cost fabrication of different samples with independently tunable resonances is demonstrated. These single-layer metasurfaces could find possible applications as bifunctional surface-enhanced infrared absorption and surface-enhanced Raman spectroscopy, multi-line, as well as broadband substrates. The fabrication method is particularly suited for the creation of large-area, single-layer C3-symmetric chiral metasurfaces, and this approach circumvents common problems with elliptical birefringence and can be utilized for interaction with chiral substances. In dieser Arbeit führen wir zwei kostengünstige Herstellungsmethoden für großflächige (ca. 1 cm^2), komplexe, plasmonische Nanostrukturen mittels verschiedener Nanokugellithographietechniken ein. Für die erste Methode verwenden wir Dünnschicht-PMMA-Goldlochmasken, die mit Hilfe von Polystyrolkolloiden hergestellt werden. In Kombination mit gekipptem und rotierendem Aufdampfen lassen sich großflächige, willkürlich angeordnete, metallische Nanostrukturen herstellen. Bei der zweiten Methode verwenden wir eine hexagonal dichtest gepackte Monolage aus Polystyrolnanokugeln als Aufdampfmaske, um großflächige, periodische,…