The electronic, structural and sensing properties of graphene nanostructures / Ye Lu.

Format:

Book

Manuscript

Thesis/Dissertation

Author/Creator:

Lu Ye.

Contributor:

Johnson, A.T. Charlie, advisor.

Drndic, Marija, advisor.

University of Pennsylvania.

Language:

English

Subjects (All):

Penn dissertations--Physics and astronomy.

Physics and astronomy--Penn dissertations.

Local Subjects:

Penn dissertations--Physics and astronomy.

Physics and astronomy--Penn dissertations.

Physical Description:

xiii, 145 pages : illustrations (some color) ; 29 cm

Production:

2011.

Summary:

The work presented in this thesis focuses on the electronic, structural and chemical properties of graphene nanostructures.

In the first set of experiments we investigate the intrinsic sensing properties of pristine graphene, prospects of chemical sensors derived from single stranded DNA (ss-DNA) decorated graphene and photosensitivity of polyhistidine-tagged (His-tagged) protein functionalized graphene transistors. As a true 2D material, graphene has all its atoms on its surface, very high room temperature carrier mobility and relatively low electrical noise. These advantages render graphene as a very promising candidate for sensor/detector applications. These applications require the fabrication of graphene electronic devices through lithography techniques. However, we find that conventional lithography leaves a layer of resist residue on top of the graphene surface which has substantial impact on its electronic and sensing characteristics. Using an oven annealing procedure, we are able to clean off the residue and measure the intrinsic properties of the graphene devices. To move forward, we start with clean graphene devices and functionalize them ssDNA, where the ssDNA acts as the sensitizing agent allowing the concentration of chemical analysts to the device's surface and enhances the sensing responses. Last, we functionalize clean graphene devices with His-tagged fluorescent proteins (FPs), and developed a new type of protein-graphene hybrid devices. These devices can be used as photodetectors with wavelength selectivity.

The second part of the thesis focuses on the fabrication and characterization of graphene nanostructures. Graphene naturally lacks an energy band gap thus graphene field effect transistors (FETs) do not have sufficient current on/off ratio to operate in logic circuits. One way to solve this issue is to pattern the graphene to a narrow channel so that an energy gap is opened due to quantum confinement and edge effects. We developed the first "top-down" approach to fabricate graphene nanoconstriction FETs with critical dimension less than10nm and current on/off ratio larger than 1000. Furthermore, in order to accurately measure the geometry of the graphene nanostructure, we fabricated suspended graphene ribbon on free standing silicon nitride (SiN) membranes which are transparent inside a transmission electron microscope (TEM). We performed in-situ electrical measurements of graphene nanoconstrictions (GNCs) fabricated inside the TEM and found that GNCs have an ultra high current density and the conductance of GNCs decreases with constriction width in a sub-linear power law form.

Finally, we present the characterization of graphene oxide devices and large area graphene synthesis using a chemical vapor deposition method. These approaches are expected to produce scalable sheets of large area graphene in the future and enable commercialization of graphene based devices.

Notes:

Advisers: A.T. Charlie Johnson; Marija Drndic.

Thesis (Ph.D. in Physics and Astronomy) -- University of Pennsylvania, 2011.

Includes bibliographical references.