Alternative Methods and Materials for use in Plasmonics

University of Minnesota Ph.D. dissertation. March 2019. Major: Electrical/Computer Engineering. Advisor: Sang-Hyun Oh. 1 computer file (PDF); vi, 109 pages.Plasmonic devices are extremely useful across a wide variety of fields and have been used for ultra-high-resoulution imaging, drug detection, metamaterials, and single-molecule studies among other things. One major hurdle to achieving useful plasmonic structures is that deeply subwavelength patterns need to be generated, both for coupling the light to the device and to fabricate the device itself. Many plasmonic devices such as optical antennas used for nanofocusing are nonplanar, which vastly increases the difficulty of fabricating subwavelength structures on them. Standard lithographic processes such as photolithography and electron beam lithography are of limited use on three-dimensional substrates, which necessitates the development of novel fabrication techniques. Shadow mask lithography and conformal coating of metallic sidewalls via atomic layer deposition are two techniques that will be used to achieve subwavelength patterning of three-dimensional structures. Additionally, plasmonic materials have typically been dominated by gold and to a lesser extent silver because they exhibit good dielectric properties at optical frequencies and are reasonably robust to ambient conditions. However, these materials do come with their own fabrication limitations that other plasmonically active materials such as titanium nitride and copper do not necessarily have. In particular, atomic layer deposition recipes now exist for titanium nitride that allow sub-10 nm, continuous, and conformal metallic films to be created which opens up the door to novel ultrathin plasmonic structures. In this dissertation, plasmonic structures that were generated using nonstandard nanofabrication techniques and/or metallic materials will be explored, demonstrating the advantages that come with using such techniques and materials