Strain engineering the band structure of graphene

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The purpose of this work is to explore whether strain can modify the band structure of graphene and produce a bandgap. This thinnest material possible, has generated interest in the semiconductor industry for many reasons, including its potential for ballistic conduction, very high carrier mobility and saturation velocity, large current density and natural ambipolar (both n- and p-type) carrier transport. However, its lack of a bandgap suggests a limited future as a silicon replacement material in highly scaled electronics. One route towards the use of graphene transistors for logic devices relies on creating a controllable bandgap. A solution to this problem is sought that uses strain as a way to modulate the band structure and potentially open a bandgap. We have characterized changes in the electronic properties of biaxially strained graphene in the elastic range with Synchrotron Radiation Photoelectron Spectroscopy (SRPES) and Near Edge X-ray Absorption Fine Structure (NEXAFS). Biaxial tensile strain was induced in polycrystalline graphene that was attached to a nanostructured substrate. Strain of approximately 1% was determined by shifts in the Raman spectra. Band structure characterization was performed using photoemission from valence bands, shifts in the secondary electron emission, and NEXAFS absorption from the C1s to the unoccupied graphene conduction bands. We also have used 3-terminal FET structures to study changes in the transconductance of transistors with strained graphene as channel material as compared to FETs with flat graphene channel. The results shows that biaxial strain increased the graphene work function, which is due to the shift of the Fermi energy with strain, and induced band broadening in the valence bands and conduction bands. Furthermore, the ambipolar behavior in strained graphene is suppressed at positive gate voltages. This suggests that there is potentially an increase in the effective bandgap in strained graphene. Strained graphene can thus create a possible route toward a broad class of future graphene electronics. In chapter I, an overview of the current state of the nanoelectronic industry is given, followed by an overview of the electronic properties of graphene relevant to the experimental results of this work. Chapter II is a survey of theoretical and experimental work done on strained graphene. In chapter III, fabrication process, SEM images and Raman characterization of graphene is detailed. In chapter IV, band structure characterization of strained graphene is presented. In chapter V, fabrication of field effect transistors is given, and the effect of strain on electrical properties of graphene is examined. Finally, in chapter VI, possible future work about this project is suggested.


Type of resource text
Form electronic; electronic resource; remote
Extent 1 online resource.
Publication date 2016
Issuance monographic
Language English


Associated with Aslani, Marjan
Associated with Stanford University, Department of Electrical Engineering.
Primary advisor Nishi, Yoshio, 1940-
Thesis advisor Nishi, Yoshio, 1940-
Thesis advisor Garner, C. Michael
Thesis advisor Pianetta, Piero
Advisor Garner, C. Michael
Advisor Pianetta, Piero


Genre Theses

Bibliographic information

Statement of responsibility Marjan Aslani.
Note Submitted to the Department of Electrical Engineering.
Thesis Thesis (Ph.D.)--Stanford University, 2016.
Location electronic resource

Access conditions

© 2016 by Marjan Aslani

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