Date of Award

4-2013

Degree Name

Doctor of Philosophy

Department

Physics

First Advisor

Dr. Asghar N. Kayani

Second Advisor

Dr. Sung Chung

Third Advisor

Dr. Dean Halderson

Fourth Advisor

Dr. Suntharampillai Thevuthasan

Keywords

metal nanostructures, structure-property relationships, enhancement factors, surface Plasmon resonance, ion implantation, lithography

Abstract

The confluence of nanotechnology and plasmonics has led to new and interesting phenomena. The industrial need for fast, efficient and miniature devices which constantly push the boundaries on device performance tap into the happy marriage between these diverse fields. Designing devices for real life application that give superior performance when compared with existing ones are enabled by a better understanding of their structure-property relationships. Among all the design constraints, without doubt, the shape and size of the nanostructure along with the dielectric medium surrounding it has the maximum influence on the response and thereby the performance of the device. Hence a careful study of the above mentioned parameters is of utmost importance in designing efficient devices.

In this dissertation, we synthesize and study the optical properties of nanostructures of different shapes and size. In particular, we estimated the plasmonic near field enhancement via surface-enhanced Raman scattering (SERS) and 2-photon Photoemission electron microscopy (2P-PEEM). We synthesized the nanostructures using four different techniques. One synthesis technique, the thermal growth method was employed to grow interesting Ag and Au nanostructures on Si. The absence of toxic chemicals during nanostructure synthesis via the thermal growth technique opens up myriad possibilities for applications in the fields of biomedical science, bioengineering, drug delivery among others along with the huge advantage of being environment friendly. The other three synthesis techniques (ion implantation, Electrodeposition and FIB lithography) were chosen with the specific goal of designing novel plasmonic metal, metal hybrid nanostructures as photocathode materials in next generation light sources. The synthesis techniques for these novel nanostructures were dictated by the requirement of high quantum efficiency, robustness under constant irradiation and coherent unidirectional electron emission. Two designs, (i) partially exposed metal nanostructures in an oxide matrix (ii) metal nanorod arrays, couple with incoming light at particular wavelengths which leads to plasmonic near field enhancement from the nanostructures. This plasmonic response is expected to lead to enhanced photoemission and thereby enhanced quantum efficiency. Moreover, the plasmonic enhancement and the shape of the nanostructure enable coherent unidirectional electron emission. Such an in depth study of the structure-property relationship, particularly the near field enhancement of novel metal, metal-metal oxide nanostructures will lead to applications as photocathode materials in next generation light sources.

Access Setting

Dissertation-Open Access

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