Graphene, Polycyclic Aromatic Hydrocarbons and Topological

148 Pages·2013·17.37 MB·English

Graphene, Polycyclic Aromatic
Hydrocarbons and Topological Insulators
A scanning tunneling microscopy study
Louis Nilsson
Interdisciplinary Nanoscience Center (iNANO) and
Department of Physics and Astronomy
Aarhus University, Denmark
PhD thesis
July 2013
ThisthesishasbeensubmittedtotheFacultyofScienceandTechnology
at Aarhus University in order to fulfil the requirements for obtaining a
PhD degree. The work has been performed under supervision of Asso-
ciate Professor Liv Hornekær and Professor Flemming Besenbacher in
the Surface Dynamics Group at the Interdisciplinary Nanoscience Cen-
ter (iNANO) and the Department of Physics and Astronomy, Aarhus
University.
I have not been involved in performing the density functional theory
calculations presented in this thesis. The credit for most of these calcu-
lations should be given to Mie Andersen in Professor Bjørk Hammer’s
group. The sections about these calculations should therefore not be
part of the evaluation of my work; however, they are presented here to-
gether with the corresponding experimental results for the convenience
of the reader.
Contents
List of publications i
List of abbreviations iii
1 Introduction 1
1.1 Motivation. . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2 Techniques and experimental setups 7
2.1 Scanning tunneling microscopy . . . . . . . . . . . . . . . . 8
2.1.1 Tersoff’s and Hamann’s theory for STM . . . . . . . 8
2.1.2 STM setups . . . . . . . . . . . . . . . . . . . . . . . 9
2.1.3 Scanning tunneling spectroscopy . . . . . . . . . . . 13
2.2 Temperature programmed desorption . . . . . . . . . . . . . 14
2.3 Angle-resolved photoemission spectroscopy . . . . . . . . . . 16
2.4 Low-energy electron diffraction . . . . . . . . . . . . . . . . 17
2.5 Density functional theory . . . . . . . . . . . . . . . . . . . 18
2.6 Experimental setups . . . . . . . . . . . . . . . . . . . . . . 21
2.6.1 The green chamber . . . . . . . . . . . . . . . . . . . 21
2.6.2 The coal chamber . . . . . . . . . . . . . . . . . . . . 21
2.6.3 The blue chamber . . . . . . . . . . . . . . . . . . . 22
3 Graphene 25
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.2 Production of graphene . . . . . . . . . . . . . . . . . . . . 28
3.3 Graphene on metal surfaces . . . . . . . . . . . . . . . . . . 29
3.3.1 Graphene on Ir(111) . . . . . . . . . . . . . . . . . . 31
3.3.2 Graphene on Pt(100) . . . . . . . . . . . . . . . . . . 32
3.4 Band gap opening in graphene . . . . . . . . . . . . . . . . 41
3.4.1 Hydrogenation of graphene on Ir(111) . . . . . . . . 45
3.4.2 Hydrogenation of graphene on Pt(100) . . . . . . . . 51
3.4.3 Templating hydrogen on graphene . . . . . . . . . . 53
3.5 Graphene Coatings . . . . . . . . . . . . . . . . . . . . . . . 59
3.5.1 Graphene coatings on Pt(100) . . . . . . . . . . . . . 59
4 Polycyclic aromatic hydrocarbons 83
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
4.2 Coronene . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
4.2.1 Coronene on Cu(100). . . . . . . . . . . . . . . . . . 86
4.2.2 Hydrogenation of coronene on Cu(100) . . . . . . . . 90
5 Topological insulators 93
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
5.2 Bismuth selenide (Bi Se ) . . . . . . . . . . . . . . . . . . . 97
2 3
5.2.1 Pristine Bi Se (111) . . . . . . . . . . . . . . . . . . 98
2 3
5.2.2 Stability of the Bi Se (111) topological state . . . . 103
2 3
6 Summary and Outlook 107
6.1 Graphene . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
6.2 Polycyclic aromatic hydrocarbons . . . . . . . . . . . . . . . 110
6.3 Topological Insulators . . . . . . . . . . . . . . . . . . . . . 111
7 Dansk Resumé 113
7.1 Scanning tunnel mikroskopi . . . . . . . . . . . . . . . . . . 114
7.2 Graphen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
7.3 Polyaromatiske kulbrinter . . . . . . . . . . . . . . . . . . . 119
7.4 Topologiske isolatorer . . . . . . . . . . . . . . . . . . . . . 121
Acknowledgements 123
List of publications
• R. Balog, B. Jorgensen, L. Nilsson, M. Andersen, E. Rienks, M.
Bianchi, M. Fanetti, E. Laegsgaard, A. Baraldi, S. Lizzit, Z. Sljivan-
canin, F.Besenbacher, B.Hammer, T.G.Pedersen, P.Hofmannand
L. Hornekaer. Bandgap opening in graphene induced by patterned
hydrogen adsorption. Nature Materials, 9 (4): 315-319, 2010.
• R. Hatch, M. Bianchi, D. Guan, S. Bao, J. Mi, B. Iversen, L.
Nilsson, L. Hornekær and P. Hofmann. Stability of the Bi Se (111)
2 3
topological state: Electron-phonon and electron-defect scattering.
Physical Review B, 83 (24), 2011.
• L. Nilsson, M. Andersen, J. Bjerre, R. Balog, B. Hammer, L.
Hornekær and I. Stensgaard. Preservation of the Pt(100) surface
reconstruction after growth of a continuous layer of graphene. Sur-
face Science, 606 (3-4): 464-469, 2012.
• L. Nilsson, M. Andersen, R. Balog, E. Lægsgaard, P. Hofmann, F.
Besenbacher, B.Hammer, I.StensgaardandL.Hornekær. Graphene
Coatings: Probing the Limits of the One Atom Thick Protection
Layer. ACS Nano, 6 (11): 10258-10266, 2012.
• L. Nilsson, Z. Sljivancanin, R. Balog, W. Xu, T.R. Linderoth,
E. Lægsgaard, I. Stensgaard, B. Hammer, F. Besenbacher and L.
Hornekær. Linear hydrogen adsorbate structures on graphite and
graphene induced by self-assembled molecular monolayers. Carbon,
50: 2052-2056, 2012.
• L. Nilsson, M. Andersen, F. Besenbacher, B. Hammer, I. Stens-
gaard and L. Hornekær. Graphene Coatings - An atomic investiga-
tionofthecoatingbreakdownbysequentialexposuretoO andH S.
2 2
Submitted.
i
• J. Thrower, E. Friis, A. Skov, L. Nilsson, M. Andersen, L. Ferrighi,
B. Jørgensen, S. Baouche, R. Balog, B. Hammer and L. Hornekær.
The Interaction between Coronene and Graphite from Temperature
Programmed Desorption and DFT-vdW Calculations: Importance
of Entropic Effects and Insights into Graphite Interlayer Binding.
Accepted for publication in The Journal of Physical Chemistry.
• C.Wang,X.Zhu,L. Nilsson,J.Wen,G.Wang,X.Shan,Q-Zhang,
S. Zhang, J. Jia, Q. Xue. In-situ Raman spectroscopy of topologi-
cal insulator Bi Te films with thickness dependence. Accepted for
2 3
publication in Nano Research.
• S. Ulstrup, L. Nilsson, J. Miwa, R. Balog, M. Bianchi, P. Hof-
mann and L. Hornekær. Electronic structure of graphene on a re-
constructedPt(100)surface: Hydrogenadsorption, dopingandband
gaps. Submitted.
Proceedings
• J.D. Thrower, L. Nilsson, B. Jørgensen, S. Baouche, R. Balog,
A.C. Luntz, I. Stensgaard, E. Rauls, and L. Hornekær. Superhydro-
genated PAHs: catalytic formation of H . EAS publications series:
2
PAHs and the Universe, 46: 453-460, 2011.
Public outreach
• L. Nilsson, B. Jørgensen, R. Balog and L. Hornekær. A new age of
carbon electronics. iNano annual report: 24-25, 2010.
• L. Nilsson, B. Jørgensen and L. Hornekær. En ny generation af
elektriskekredsløb. (TitleinEnglish: Anewgenerationofelectronic
circuits). Aktuel Naturvidenskab 4:18-20, 2010
ii
List of abbreviations
ARPES Angle-resolved photoemission spectroscopy
ASTRID Aarhus storage ring in Denmark
CVD Chemical vapour deposition
CyA Cyanuric acid
DFT Density functional theory
DOS Density of states
GPAW Grid-based projector-augmented wave
HOPG Highly oriented pyrolytic graphite
ISM Interstellar medium
LDA Local-density approximation
LDOS Local density of states
LEED Low-energy electron diffraction
PAH Polycyclic aromatic hydrocarbon
PBE Perdew-Burke-Ernzerhof
QMS Quadrupole mass spectrometer
RT Room temperature
STM Scanning tunneling microscopy/microscope
STS Scanning tunneling spectroscopy
SW Stone-Wales
TPD Temperature programmed desorption
TPG Temperature programmed growth
UHV Ultra high vacuum
UV Ultraviolet
VASP Vienna ab-initio simulation package
iii

Chapter 1
Introduction
This chapter gives a short motivation and an outline for the work
presentedinthisthesis. Becauseofthevarietyofdifferentsubjectstreated;
graphene, polycyclic aromatic hydrocarbons and topological insulators, a
more thorough introduction with a literature review for each subject will
be presented in the respective chapters. The motivation in this chapter
will instead provide a broader view of the subjects and the link between
them in a more general way.
1
2 Chapter 1. Introduction
1.1 Motivation
The importance of carbon is accentuated by the fact that it is the fourth
most abundant element in the universe and the second most abundant
element, by weight, in the human body. Indeed, all known life is strongly
dependent on carbon, not only as a vital element in all living organisms
but also in our way of living: The majority of our energy consumption
comes from carbon-based compounds; Carbon is expected to play a vital
role as a catalyst in the formation of the most abundant molecule in the
universe, H ; Plastic, wool, silk etc. are all polymeric forms of carbon;
2
Diamond is used for jewellery but also for drilling and cutting tools owing
to its extreme hardness, however, graphite is used as a lubricant due to
its softness; Activated carbon is used for water purification, in medicine to
extract toxins etc.; Carbon is used for alloying e.g. carbon steel as well as
in batteries and even for printing this thesis. However, at present most of
our electronic world is based on the next element in the 14th group of the
periodic table, silicon.
An enormous development in carbon-based electronics has occurred
since the experimental realization of graphene, a single layer of sp2 hy-
bridized carbon atoms in a honey-comb structure, in 2004 [1]. A search
for the topic “graphene” on Web of Knowledge returns ca. 50.000 hits,
which emphasizes the extreme interest graphene has attracted in the sci-
entific community. Unlike many other scientific breakthroughs that of-
ten that often spend decades maturing in the scientific community before
industrial companies engage in the research, graphene already attracted
companies from a variety of industries. IBM had for instance already fab-
ricatedagraphene-based100GHztransistorin2010[2]. Samsunglikewise
contributedtotheproductionofa30"graphenesheetin2010[3]andthese
and other companies have played a central role in the development of gra-
phene based transistors and fabrication of large sheets of graphene since.
The industrial interest in graphene so shortly after its discovery indicates
that carbon might have the potential to complement silicon in electronic
device fabrication in the future.
The reasons for the great expectations for graphene are many. To
mention a few: it is the material known today with highest electronic con-
ductivity at room temperature; despite the fact that graphene is only one
atomic layer thick and almost transparent, it is extremely strong and at
thesametimeflexible; itischemicallyveryinertandimpermeabletomost
gases. Graphene, however, as a semimetal, has a poor on/off ratio when
used in transistors. Silicon, on the other hand, is a semiconductor and the