Asad Rezaee

Date of Award


Degree Type


Degree Name

Doctor of Philosophy




Prof. Silvia Mittler


Metallic nanostructures and their applications is a rapidly expanding field. Nobel metals such as silver and gold have historically been used to demonstrate plasmon effects due to their strong resonances, which occur in the visible part of the electromagnetic spectrum. Localized surface plasmon resonance (LSPR) produces an enhanced electromagnetic field at the interface between a gold nanoparticle (Au NP) and the surrounding dielectric. This enhanced field can be used for metal-dielectric interface- sensitive optical interactions that form a powerful basis for optical sensing.

In addition to the surrounding material, the LSPR spectral position and width depend on the size, shape, and average spacing between these particles. Au NP LSPR based sensors depict their highest sensitivity with optimized parameters and usually operate by investigating absorption peak shifts. The absorption peak of randomly deposited Au NPs on surfaces is mostly broad. As a result, the absorption peak shifts, upon binding of a material onto Au NPs might not be very clear for further analysis.

Therefore, novel methods based on three well-known techniques, self-assembly, ion irradiation, and organo-metallic chemical vapour deposition (OMCVD) are introduced to control the average-spacing between Au NPs. In addition to covalently binding and other advantages of OMCVD grown Au NPs, interesting optical features due to their non- spherical shapes are presented.

The first step towards the average-spacing control is to uniformly form self- assembled monolayers (SAMs) of octadecyltrichlorosilane (OTS) as resists for OMCVD Au NPs. The formation and optimization of the OTS SAMs are extensively studied. The optimized resist SAMs are ion-irradiated by a focused ion beam (FIB) and ions generated by a Tandem accelerator. The irradiated areas are refilled with 3-mercaptopropyl- trimethoxysilane (MPTS) to provide nucleation sites for the OMCVD Au NP growth.

Each step during sample preparation is monitored by using surface characterization methods such as contact angle measurements, ellipsometry, X-ray photoelectron


spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), Rutherford backscattering spectroscopy (RBS), UV-Visible spectroscopy, and time-of-flight secondary ion mass spectroscopy (ToF-SIMS).



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