π-conjugated and inorganic materials for bottom-up self-assembly and top-down lithographic fabrication of nanostructures
Date
2025
Authors
MacKenzie, Harvey
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Abstract
Nanostructured materials have emerged as critical components in every day applications ranging from microchips in electronic devices to lipid nanoparticles in the recent COVID-19 mRNA vaccines. A key challenge in nanoscience is the ability to generate low dispersity nanostructures of controlled length, morphology with tunable chemistries and functionalities, since these parameters influence their resulting properties. To address the needs of next-generation technology and applications, accessing nanostructures reproducibly and reliably is of critical importance. This dissertation explores the development of new fabrications techniques and materials to address the challenges associated with producing well-controlled nanomaterials of various morphologies and compositions using either bottom-up self-assembly or top-down photolithographic approaches.
Chapter 1 provides a detailed introduction into polymer self-assembly, living crystallization-driven self-assembly (CDSA) and its emerging applications as well as an introduction and overview for state-of-the-art photolithographic techniques and current technologies. Chapter 2 of this dissertation describes the development of a new living CDSA approach to access π-conjugated non-centrosymmetric 1-dimensional (1D) polymer nanofibers, structures that pose a significant challenge to fabricate. The described approach uses a combination of block-selective nanoparticle attachment that enables selective fragmentation of the undecorated block upon ultrasonication, enabling the fabrication of a variety of 1D non-centrosymmetric nanoparticle-nanofiber hybrids. The resulting asymmetry in these hybrid nanoparticles was then leveraged to enable their use as multifunctional nanomotors.
Chapter 3 explores the synthesis and self-assembly of complex and hierarchical π-conjugated micelles that combine 1D and 2D morphologies also known as scarf-like micelles. Using 2D platelets as seeds to initiate epitaxial growth of 1D fiber-like and 2D ribbon-like tassels, several low dispersity scarf-like architectures of various compositions were fabricated. These micelles were shown to be highly tunable, as it was possible to control both the area of the 2D platelets and/or the lengths of the tassels. These structures exhibit energy funneling and light harvesting properties and by incorporating lower bandgap corona in the micelle tassels it is possible to achieve energy transfer from the micelle cores of the 2D platelets to the tassel coronas.
Chapter 4 describes the development of a bismuth oxide cluster extreme ultraviolet (EUV) photoresist material for next generation photolithography applications. It was determined this material has an exceptional EUV absorption cross section, with a linear attenuation of 24 µm-1, approximately five times larger than commercially available chemically amplified resists (CARs) (~ 5 µm-1). Additionally, the resist was determined to be highly sensitive to EUV exposure and displayed a dose-to-gel of 10 mJ/cm2, undergoing ligand decomposition during exposure and crosslinking during the post exposure bake, which is supported by FTIR and residual gas analysis. This bismuth oxo cluster resist represents a new sub-class of inorganic resist material which lays the groundwork for further development of bismuth cluster photoresists.
Chapter 5 concludes with potential future directions for each project and provides an overall summary and outlook for this work.
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Keywords
Self-assembly, Materials Science, Polymer Chemistry, Photolithography, Inorganic Chemistry