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  4. QUANTUM METAMATERIALS DIRECTED BY BLOCK COPOLYMER SELF-ASSEMBLY VIA ADVANCED MANUFACTURING

QUANTUM METAMATERIALS DIRECTED BY BLOCK COPOLYMER SELF-ASSEMBLY VIA ADVANCED MANUFACTURING

File(s)
Yu_cornellgrad_0058F_14127.pdf (8.03 MB)
Movies.zip (71.65 MB)
Permanent Link(s)
http://doi.org/10.7298/0j05-7z42
https://hdl.handle.net/1813/115767
Collections
Cornell Theses and Dissertations
Author
Yu, Fei
Abstract

Materials manufacturing and processing is the key to the adoption and widespread application of revolutionary materials that have indelibly shaped human civilization. The current landscape of quantum materials fabrication is overwhelmingly dominated by solid state chemical reactions and physical deposition techniques, typically under stringent synthetic conditions such as ultrahigh vacuum. In this dissertation, quantum materials structure-directed by block copolymer (BCP) self-assembly and prepared by advanced manufacturing techniques are presented using three examples to illustrate the promise of BCP-enabled quantum metamaterials. The self-assembly of BCPs offers an alternative pathway toward quantum materials that is versatile, tunable, and bottom-up via solution-based processing. The structure engineering by BCP self-assembly imparts a quantum-level influence on the materials behavior in ways unattainable by compositions alone, signifying distinct characteristics of quantum metamaterials. Facilitated by advanced manufacturing, the convergence of BCP self-assembly and quantum materials is embodied by its dual scientific and technological merits.Firstly, crystalline silicon with a mesoscale symmetry suggesting topologically protected Weyl points was prepared through non-equilibrium laser heating. The unique symmetry was broken from the alternating/single gyroid morphology self-assembled by BCPs and carbon precursors, which formed a mesoporous template after pyrolysis. After deposition into the template in the amorphous form, silicon attained otherwise inaccessible mesoscale ordering in the crystalline form following transient laser heating in air on a nanosecond time scale. The short heating duration melted and crystallized the silicon under highly non-equilibrium conditions that far outpaced the decomposition kinetics of the organically derived template, thus preserving the mesostructural integrity. The resulting topologically relevant symmetry was revealed by grazing incidence small-angle X-ray scattering and represented the first of its kind as topological quantum metamaterials. Secondly, mesoporous superconductors directed by BCP self-assembly were expanded into the thin film regime. Technologically more important than previous monolithic pieces derived from evaporation-induced self-assembly, thin films were prepared by spin-coating the hybrid solution containing the structure-directing BCP and niobia sol on a silicon substrate. Mesoporous superconducting niobium nitride thin films were prepared after heat treatments in air and reactive gases of ammonia and carburizing gas. The granular nanocrystals in a network morphology displayed a thermally activated conduction mechanism. The upper critical field derived from measurements of field-dependent critical temperatures exceeded values reported in literature for bulk niobium nitride. Moreover, the spin-coated films could be integrated into typical nanofabrication processes. Using lithography to define patterns, the thin films again exhibited superconductivity. Lastly, self-assembled mesoporous superconductors were complemented by the diverse form factors enabled through 3D printing (additive manufacturing). Direct ink writing commercially available Pluronic BCPs mixed with niobia sol in a hydrophobic bath ensured proper mechanical strength due to ink precipitation. After similar heat treatment to convert into niobium nitride, the 3D printed superconductors were hierarchically ordered across several length scales, from the nanocrystals, through the periodic hexagonal mesostructure, to the macroscopic woodpile shape. Moreover, embedded printing yielded complex non-self-supporting geometries such as helices, which were also converted to superconducting niobium nitrides. Such 3D printed superconductors had a specific surface area of over 120 m2/g. The confinement resulting from both the BCP structure direction and the nitride crystal granularity led to an upper critical field of 50 T, amongst the highest reported for niobium nitride. The enhanced performance in the upper critical field could be further tuned by the molar mass of the structure directing Pluronic BCPs, a clear fingerprint of quantum metamaterials behavior. The dissertation commences with an introduction reviewing the existing research effort surrounding BCP self-assembly-directed quantum materials. The body of the dissertation, including the three examples summarized above, is adapted from scientific articles of respective work, either published or under preparation at the time of dissertation writing. The dissertation concludes by offering critical perspectives for further directions in this emerging field that may help navigate through the challenges in the future.

Description
212 pages
Supplemental file(s) description: Movies.
Date Issued
2023-12
Keywords
additive manufacturing
•
advanced manufacturing
•
block copolymer
•
metamaterial
•
quantum material
•
superconductor
Committee Chair
Wiesner, Ulrich
Committee Member
Gruner, Sol
Milner, Phillip
Degree Discipline
Chemistry and Chemical Biology
Degree Name
Ph. D., Chemistry and Chemical Biology
Degree Level
Doctor of Philosophy
Rights
Attribution-NonCommercial-ShareAlike 4.0 International
Rights URI
https://creativecommons.org/licenses/by-nc-sa/4.0/
Type
dissertation or thesis
Link(s) to Catalog Record
https://newcatalog.library.cornell.edu/catalog/16454759

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