Atomic-Scale Characterization of Nanometer-Sized Graphene

Ritter, Kyle

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https://hdl.handle.net/2142/82828 Copy

Description

Title

Atomic-Scale Characterization of Nanometer-Sized Graphene

Author(s)

Ritter, Kyle

Issue Date

2008

Doctoral Committee Chair(s)

Lyding, Joseph W.

Department of Study

Materials Science and Engineering

Discipline

Materials Science and Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

Physics, Condensed Matter

Language

eng

Abstract

We have developed a method for depositing atomically clean, nanometer-sized graphene monolayers with 2-30 nm lateral dimensions and we probe the local electronic properties of the graphene using the ultrahigh-vacuum scanning tunneling microscope (UHV-STM). By using tunneling spectroscopy, we measure a size-dependent energy gap for graphene quantum dots (QDs) (aspect ratio ≈1) and determine the energy gap (Eg)---size ( L) relation. Our Eg (eV) = 1.53 +/- 0.41 eV·nm/L1.01 +/- 0.23 least-squares fit quantitatively agrees with the simple model Eg (eV) = 1.68 eV·nm/L resulting from quantum confinement and the linear dispersion of graphene. Predominantly zigzag-edge QDs with 7-8 nm average dimensions are metallic and diverge from the Eg-L scaling law due to the presence of zigzag edge states which spatially decay into the graphene interior with a 1.0-1.2 nm decay length. In addition to graphene QDs, we study the electronic structure of graphene nanoribbons (GNRs) with 2-3 nm widths and 20-30 nm lengths. GNRs with a higher fraction of zigzag edges exhibit a smaller energy gap than a predominantly armchair-edge ribbon of similar width and the magnitude of the measured GNR energy gaps agree with recent theoretical calculations.

Graduation Semester

2008

Type of Resource

text

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http://hdl.handle.net/2142/82828

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