Non-planar and curved architectures of otherwise flat 2D materials present an important paradigm for nanoscale analysis and design of emergent material properties. Atomically-thin transition metal dichalcogenides (TMDs) have emerged at the forefront of the 2D materials field in recent years largely due to their attractive and tunable chemical, optical, and electronic properties. Inducing structural changes by curving TMDs naturally invokes elements vital to engineering material properties, notably topological defects, localized strain, and interfaces. Non-planar TMD forms can exhibit diverse curvatures, morphologies, and 3D architectures across a hierarchy of length scales, resulting in a large parameter space for material design. This dissertation centers on a particular class of curved multidimensional nanocomposites – the TMD core-shell architecture – and investigates the link between structure and properties in this system through the lens of synthesis and characterization. The TMD core-shell architecture offers valuable design levers for manipulating the properties of a curved TMD shell, including (1) hybridization through intimate contact with a functional nanoparticle core; (2) curvature-induced strain and defect engineering; (3) and complex hierarchical assemblies through directed assembly and patterning, with the potential for potent synergistic effects when these capabilities are combined. To fully realize these engineering opportunities, an atomic-scale understanding of structure is required. The first part of this thesis (Chapters 2-4) is dedicated to studying the nature of curvature in TMD core-shell architectures, specifically the intricate relationship between synthesis, structure, and topology. This insight allows for the construction of a unified geometric framework built upon dimensionality and mathematical definitions of curvature to classify a wide variety of structures and identify opportunity areas in the field of curved TMDs. The following section discusses how the TMD chemical vapor deposition synthesis platform can be adapted for non-planar geometries and analyzes the nucleation and growth of TMD shells. By finely tuning synthesis parameters, these findings allow for deterministic engineering of the morphology of TMD core-shells. This part of the thesis concludes with an analysis of the rich variety of topological and non-topological defects in TMD shells, which are examined using scanning/transmission electron microscopy and theoretical energy calculations. The second part this thesis (Chapters 5-6) focuses on opportunities for deploying TMD core-shell architectures in emerging technologies. Because this system allows for intimately interfacing dissimilar materials, a pathway to engineer optical properties through synergistic core-shell interaction is first presented. Further, the versatility of this platform enables synthesis of a more complex variety of the core-shell structure (i.e. an MoS2/WS2 heterostructure shell) and new application opportunities through a solution preparation platform. Finally, directions for future research based on these topics are presented, along with a broader perspective of opportunities in the field of curved layered materials. An appendix summarizes relevant collaborative studies furthering the application of TMD core-shell architectures in energy, electronics, and optoelectronics.

Creator

• DiStefano, Jennifer G

DOI

• https://doi.org/10.21985/n2-rena-4b57

Subject

• Nanotechnology
• Nanoscience
• Materials Science

Language

• en

Alternate Identifier

• etdadmin_upload_788467
• http://dissertations.umi.com/northwestern:15438

Date created

• 2020-01-01

Resource type

• Dissertation

Rights statement

• In Copyright