STRONG AND WEAK INTERLAYER INTERACTIONS OF TWO-DIMENSIONAL MATERIALS AND THEIR ASSEMBLIES Public Deposited

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Last Modified
  • March 21, 2019
Creator
  • Farnsworth, Tyler
    • Affiliation: College of Arts and Sciences, Department of Chemistry
Abstract
  • The ability to control the properties of a macroscopic material through systematic modification of its component parts is a central theme in materials science. This concept is exemplified by the assembly of quantum dots into 3D solids, but the application of similar design principles to other quantum-confined systems, namely 2D materials, remains largely unexplored. Here I demonstrate that solution-processed 2D semiconductors retain their quantum-confined properties even when assembled into electrically conductive, thick films. Structural investigations show how this behavior is caused by turbostratic disorder and interlayer adsorbates, which weaken interlayer interactions and allow access to a quantum-confined but electronically coupled state. I generalize these findings to use a variety of 2D building blocks to create electrically conductive 3D solids with virtually any band gap. I next introduce a strategy for discovering new 2D materials. Previous efforts to identify novel 2D materials were limited to van der Waals layered materials, but I demonstrate that layered crystals with strong interlayer interactions can be exfoliated into few-layer or monolayer materials. The strategy relies on a mechanistic similarity between mechanical exfoliation and scratching in layered materials: both involve crack propagation between layers. I therefore use the Mohs hardness scale, a measure of scratch resistance, to identify promising layered materials, and I test these predictions using mechanical exfoliation. We find that a Mohs hardness of five is a threshold below which mechanical exfoliation occurs. To understand why, we examined 1,000 crystals and find an intuitive correlation between Mohs hardness and the nature of interlayer bonding. Finally, we show how our approach can be extended to computational searches of large databases of material properties to find additional 2D materials that can be used as building blocks for new 3D solids with custom-designed properties.
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Rights statement
  • In Copyright
Advisor
  • You, Wei
  • Cahoon, Jim
  • Brennaman, Matthew
  • Warren, Scott
  • Atkin, Joanna
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2018
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