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Structural and Electronic Properties of Graphene on 4H- and 3C-SiC
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Graphene is a one-atom-tick carbon layer arranged in a honeycomb lattice. Graphene was first experimentally demonstrated by Andre Geim and Konstantin Novoselov in 2004 using mechanical exfoliation of highly oriented pyrolytic graphite (exfoliated graphene flakes), for which they received the Nobel Prize in Physics in 2010. Exfoliated graphene flakes show outstanding electronic properties, e.g., very high free charge carrier mobility parameters and ballistic transport at room temperature. This makes graphene a suitable material for next generation radio-frequency and terahertz electronic devices. Such applications require fabrication methods of large-area graphene compatible with electronic industry. Graphene grown by sublimation on silicon carbide (SiC) offers a viable route towards production of large-area, electronic-grade material on semi-insulating substrate without the need of transfer. Despite the intense investigations in the field, uniform wafer-scale graphene with very high-quality that matches the properties of exfoliated graphene has not been achieved yet. The key point is to identify and control how the substrate affects graphene uniformity, thickness, layer stacking, structural and electronic properties. Of particular interest is to understand the effects of SiC surface polarity and polytype on graphene properties in order to achieve large-area material with tailored properties for electronic applications. The main objectives of this thesis are to address these issues by investigating the structural and electronic properties of epitaxial graphene grown on 4HSiC and 3C-SiC substrates with different surface polarities. The first part of the thesis includes a general description of the properties of graphene, bilayer graphene and graphite. Then, the properties of epitaxial graphene on SiC by sublimation are detailed. The experimental techniques used to characterize graphene are described. A summary of all papers and contribution to the field is presented at the end of Part I. Part II consists of seven papers.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2016. , 74 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1793
National Category
Condensed Matter Physics Materials Chemistry Textile, Rubber and Polymeric Materials Other Materials Engineering Other Physics Topics
Identifiers
URN: urn:nbn:se:liu:diva-132408DOI: 10.3384/diss.diva-132408ISBN: 9789176856789 (Print)OAI: oai:DiVA.org:liu-132408DiVA: diva2:1045464
Public defence
2016-11-28, Planck, Fysikhuset, Campus Valla, Linköping, 11:15 (English)
Opponent
Supervisors
Funder
Swedish Research Council, 2013−5580VINNOVA, 2011−03486Swedish Foundation for Strategic Research , FFL12−0181Swedish Foundation for Strategic Research , RIF14−055Linköpings universitet, LiU No2009 00971
Note

Research Funders not listed under Research funders and strategic development areas: Marie Curie actions under the Project No.264613-NetFISiC, the centre of Nano Science and Nano technology (CeNano).

Available from: 2016-11-09 Created: 2016-11-09 Last updated: 2016-11-09Bibliographically approved
List of papers
1. Structural properties and dielectric function of graphene grown by high-temperature sublimation on 4H-SiC(000-1)
Open this publication in new window or tab >>Structural properties and dielectric function of graphene grown by high-temperature sublimation on 4H-SiC(000-1)
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2015 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 117, no 8, 085701- p.Article in journal (Refereed) Published
Abstract [en]

Understanding and controlling growth of graphene on the carbon face (C-face) of SiC presents a significant challenge. In this work, we study the structural, vibrational, and dielectric function properties of graphene grown on the C-face of 4H-SiC by high-temperature sublimation in an argon atmosphere. The effect of growth temperature on the graphene number of layers and crystallite size is investigated and discussed in relation to graphene coverage and thickness homogeneity. An amorphous carbon layer at the interface between SiC and the graphene is identified, and its evolution with growth temperature is established. Atomic force microscopy, micro-Raman scattering spectroscopy, spectroscopic ellipsometry, and high-resolution cross-sectional transmission electron microscopy are combined to determine and correlate thickness, stacking order, dielectric function, and interface properties of graphene. The role of surface defects and growth temperature on the graphene growth mechanism and stacking is discussed, and a conclusion about the critical factors to achieve decoupled graphene layers is drawn. (C) 2015 AIP Publishing LLC.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2015
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-117253 (URN)10.1063/1.4908216 (DOI)000351132500070 ()
Note

Funding Agencies|Marie Curie actions [264613-NetFISiC]; Swedish Research Council (VR) [2011-4447, 2013-5580]; Swedish Governmental Agency for Innovation Systems (VINNOVA) under the VINNMER international qualification program [2011-03486]; Swedish foundation for strategic research (SSF) [FFL12-0181]; FP7 EU project Nano-Rf [FP7-ICT-2011-8]; French ANR under the Grafonics Project [ANR-10-NANO-0004]; European Union Seventh Framework Programme under Graphene Flagship [604391]; Knut and Alice Wallenbergs foundation

Available from: 2015-04-22 Created: 2015-04-21 Last updated: 2016-11-09
2. Cavity-enhanced optical Hall effect in epitaxial graphene detected at terahertz frequencies
Open this publication in new window or tab >>Cavity-enhanced optical Hall effect in epitaxial graphene detected at terahertz frequencies
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2016 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584Article in journal (Refereed) In press
Abstract [en]

Cavity-enhanced optical Hall effect at terahertz (THz) frequencies is employed to determine the free charge carrier properties in epitaxial graphene (EG) with different number of layers grown by high-temperature sublimation on 4H-SiC(0001). We find that one monolayer (ML) EG possesses p-type conductivity with a free hole concentration in the low 1012 cmᅵᅵᅵ2 range and a free hole mobility parameter as high as 1550 cm2/Vs. We also find that 6 ML EG shows n-type doping behavior with a much lower free electron mobility parameter of 470 cm2/Vs and an order of magnitude higher free electron density in the low 1013 cmᅵᅵᅵ2 range. The observed differences are discussed. The cavity-enhanced THz optical Hall effect is demonstrated to be an excellent tool for contactless access to the type of free charge carriers and their properties in two-dimensional materials such as EG.

Place, publisher, year, edition, pages
Elsevier, 2016
Keyword
THz optical Hall effect, Epitaxial graphene, Free charge carrier properties
National Category
Physical Sciences Condensed Matter Physics Atom and Molecular Physics and Optics Ceramics
Identifiers
urn:nbn:se:liu:diva-132407 (URN)10.1016/j.apsusc.2016.10.023 (DOI)
Available from: 2016-11-09 Created: 2016-11-09 Last updated: 2016-11-14Bibliographically approved

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