MSE PhD Final Oral Defense of Serap Aksu

TITLE: Nanostencil Lithography for Plasmonic Metamaterials and Application on Vibrational Biospectroscopy ABSTRACT: Development of low cost nanolithography tools for precisely creating a variety of nanostructure shapes and arrangements in a high-throughput fashion is crucial for next generation biophotonic technologies. Although existing lithography techniques offer tremendous design flexibility, they have major drawbacks such as low-throughput, and fabrication complexity. In addition, the demand for the systematic fabrication of sub-100 nm structures on flexible, stretchable, non-planar nanoelectronic/photonic systems and multi-functional materials has fueled the research for innovative fabrication methods in recent years. This thesis research investigates a novel lithography approach for fabrication of engineered plasmonic nanostructures and metamaterials operating at visible and infrared wavelengths. The technique is called Nanostencil Lithography (NSL) and relies on direct deposition of materials through nanoapertures on a stencil. NSL enables high throughput fabrication of engineered antenna arrays with optical qualities similar to the ones fabricated by standard electron beam lithography. Moreover, nanostencils can be reused multiple times to fabricate series of plasmonic nanoantenna arrays with identical optical responses providing high throughput manufacturing. Using nanostencils, very precise nanostructures could be fabricated with 10 nm accuracy. Furthermore, this technique has the flexibility and the resolution to create complex plasmonic nanostructure arrays on the substrates that are difficult to work with e-beam and ion beam lithography tools. Combining plasmonics with polymeric materials, biocompatible surfaces or curvilinear and non-planar objects enable unique optical applications since they can preserve normal device operation under large strain. In this work, mechanically tunable flexible optical materials and spectroscopy probes integrated on fiber surfaces that could be used for a wide range of applications are demonstrated. Finally, the first application of NSL fabricated low cost infrared nanoantenna arrays for plasmonically enhanced vibrational biospectroscopy is presented. Detection of immunologically important protein monolayers with thickness as small as 3 nm, and antibody assays are demonstrated using nanoantenna arrays fabricated with reusable nanostencils. The results presented demonstrate that nanostencil lithography is a promising method for reducing the nanomanufacturing cost while enhancing the performance of biospectroscopy tools for biology and medicine. As a single-step and low cost nanofabrication technique, NSL could facilitate the manufacturing of biophotonic technologies for real-world applications. COMMITTEE: Advisor: Hatice Altug, MSE/ECE; Theodore Moustaks, MSE/ECE; Selim Unlu, MSE/ECE; Siddharth Ramachandran, MSE/ECE; Chair: Roberto Paiella, MSE/ECE