Keywords

Graphene, graphene oxide, field effect transistor, electron transport

Abstract

Reduced graphene oxide (RGO) sheet, a chemically functionalized atomically thin carbon sheet, provides a convenient pathway for producing large quantities of graphene via solution processing. The easy processibility of RGO sheet and its composites offer interesting electronic, chemical and mechanical properties that are currently being explored for advanced electronics and energy based materials. However, a clear understanding of electron transport properties of RGO sheet is lacking which is of great significance for determining its potential application. In this dissertation, I demonstrate fabrication of high-yield solution based graphene field effects transistor (FET) using AC dielectrophoresis (DEP) and investigate the detailed electronic transport properties of the fabricated devices. The majority of the devices show ambipolar FET properties at room temperature. However, the mobility values are found to be lower than pristine graphene due to a large amount of residual defects in RGO sheets. I calculate the density of these defects by analyzing the low temperature (295 to 77K) charge transport data using space charge limited conduction (SCLC) with exponential trap distribution. At very low temperature (down to 4.2 K), I observe Coulomb blockade (CB) and Efros-Shklovskii variable range hopping (ES VRH) conduction in RGO implying that RGO can be considered as a graphene quantum dots (GQD) array, where graphene domains act like QDs while oxidized domains behave like tunnel barriers between QDs. This was further confirmed by studying RGO sheets of varying carbon sp 2 fraction from 55 – 80 % and found that both the localization length and CB can be tuned. From the localization length and using confinement effect, we estimate tunable band gap of RGO sheets with varying carbon sp 2 fraction. I then studied one dimensional RGO nanoribbon iv (RGONR) and found ES VRH and CB models are also applicable to the RGONR. However, in contrast to linear behavior of decrease in threshold voltage (Vt) with increasing temperature (T) in the RGO, sub linear dependence of Vt on T was observed in RGONR due to reduced transport pathways. Finally, I demonstrate synthesis and transport studies of RGO/nanoparticles (CdS and CeO2) composite and show that the properties of RGO can be further tuned by attaching the nanoparticles.

Notes

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Graduation Date

2012

Semester

Fall

Advisor

Khondaker, Saiful

Degree

Doctor of Philosophy (Ph.D.)

College

College of Sciences

Department

Physics

Degree Program

Physics

Format

application/pdf

Identifier

CFE0004785

URL

http://purl.fcla.edu/fcla/etd/CFE0004785

Language

English

Release Date

June 2014

Length of Campus-only Access

1 year

Access Status

Doctoral Dissertation (Open Access)

Subjects

Dissertations, Academic -- Sciences, Sciences -- Dissertations, Academic

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Physics Commons

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