Topological defects in single and multi-layer graphene

Annevelink, Emil

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https://hdl.handle.net/2142/110422 Copy

Description

Title

Topological defects in single and multi-layer graphene

Author(s)

Annevelink, Emil

Issue Date

2021-03-15

Director of Research (if dissertation) or Advisor (if thesis)

• Ertekin, Elif
• Johnson, Harley T

Doctoral Committee Chair(s)

• Ertekin, Elif
• Johnson, Harley T

Committee Member(s)

• van der Zande, Arend
• Huang, Pinshane
• Admal, Nikhil C
• Pochet, Pascal

Department of Study

Mechanical Sci & Engineering

Discipline

Mechanical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Graphene
• Dislocations
• Grain Boundaries
• Twisted Bilayer Graphene
• linear elasticity
• synthesis
• atomic scale simulations

Abstract

Since its monolayer exfoliation in 2004, graphene has been the focus of intense study revealing a multitude of exciting properties that allow for studying fundamental physics and new engineering devices. In particular, monolayer graphene has unique mechanical properties such as high in-plane strength but very low flexural rigidity. This causes in-plane strains to be accommodated through out-of-plane deformation enabling engineering complex 3D deformation of graphene-based on patterned in-plane strain. In addition, monolayer graphene only weakly bonds with itself enabling non-lattice stacking between two graphene layers or graphene and an arbitrary crystalline surface. Non-lattice stacking has created a whole new sub-field called moir ́e engineering, which takes advantage of the larger scale periodicity caused by two periodic interfaces. An exciting possibility of moir ́e engineering is to enable new physics such as the unconventional superconductivity found in twisted bilayer graphene. Common between these are dislocations. Dislocations can be used to a pattern in plane strain and describe the mismatch between two lattices. Dislocations are topological defects that add an extra half-plane of atoms causing a large strain at the core of the dislocation. Dislocations have been studied for both their role in out-of-plane deformation in mono-layer graphene and periodicity in moir ́e superlattices. However, the effect of out-of-plane deformation and weak interlayer bonding on the mechanics of dislocations has not been fully studied. We focus on how dislocation mechanics appear in grain boundary migration and moir ́e patterns. For grain boundary migration, while the structure and energy of dislocations in single layer graphene have been studied, grain boundary dislocations, which nucleate when grain boundaries form kinks and disconnections, are important to understand structure evolution during annealing. However, it is uncertain how these dislocations are impacted by the out-of-plane deformation observed at edge dislocations in graphene. Or, while it has long been suggested that moir ́e patterns are arrays of inter-layer dislocations, there has not been a rigorous connection to dislocation topology nor a formal presentation of a linear elastic theory of dislocation between two 2D materials. In this thesis, we address these two dislocations by defining their topology and developing continuum dislocation models to isolate the mechanics of dislocations in graphene systems from atomistic calculations.

Graduation Semester

2021-05

Type of Resource

Thesis

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http://hdl.handle.net/2142/110422

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Copyright 2021 Emil Annevelink

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