Dirac Fermions in Graphene and Graphiteâa view from angle ...

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strong similarity to that of graphene. It is fundamental to understand how the electronic structure evolves from graphene to graphite as the number of layers increases. Figure 1.6. Brillouin zone and electronic structure of bulk graphite. 7
Chapter 2 Experimental techniques 2.1 Angle resolved photoemission spectroscopy (ARPES) 2.1.1 ARPES and the photoelectric effect Photoemission describes the ejection of electrons from a metal when a beam of light is shine on the clean surface. It was discovered by Hertz in 1887 and explained by Einstein in 1905. The photoelectric effect was very puzzling when it was first discovered, with a few mysterious key points. First, the electrons were emitted immediately. Second, increasing the intensity of the light increases the number of photoelectrons, but not their maximum kinetic energy. Third, red light will not cause ejection of electrons, no matter how strong it is. Fourth, a weak violet light will eject only a small amount of electrons, but their maximum kinetic energies are larger than those ejected by intense light of longer wavelength. These results cannot be explained without invoking the quantum nature of light, the wave-particle duality. Einstein postulated that light is quantized and that each quanta photon carried energy hν. The maximum kinetic energy of the photoelectrons is E max = hν − φ, (2.1) where φ (typically 4 to 5 eV for most materials) is the work function of the materials, i.e. the minimum energy needed to excite an electron into the vacuum. In Einstein’s theory, light is not just a particle and not just a wave: it can be one or the other, depending on how it is measured. For his explanation of photoelectric effect, Einstein was awarded the Nobel prize in 1921. It was later realized that photoelectric effect could provide useful information about the electronic states inside the materials. As a result of energy conservation, the energy distribution of photoelectrons can provide information about the density of states in the material studied 14 . Started from 1960’s, it was realized that momentum dependent band structure could be mapped from the angle and energy dependence of the photoemission spectra and the first angle resolved photoemission was demonstrated in 1974 15,16 . This technique, today known as angle resolved photoemission spectroscopy (ARPES) is among the most powerful spectroscopic techniques as it provides direct information on the electronic binding energy and the crystal momentum of solids. A schematic drawing of the experimental setup used in ARPES experiment and typical data set is shown in Fig. 2.1. Information on Fermi surface topology and band structure can be directly extracted from the peak position of the photoemitted electrons as a function of energy and angle of emission (momentum). As a result of the uncertainty principle, the width of the ARPES peak can also give 8
Page 1 and 2: Dirac Fermions in Graphene and Grap
Page 3 and 4: Dirac Fermions in Graphene and Grap
Page 5 and 6: Contents Abstract 1 Contents Acknow
Page 7 and 8: 7.6 Conclusions and implication of
Page 9 and 10: Curriculum Vitæ Shuyun Zhou Educat
Page 11 and 12: • Selected as Science Highlight f
Page 13 and 14: The unit cell of graphene contains
Page 15 and 16: Projecting this equation into φ(r
Page 17: Figure 1.5. Schematic drawing of th
Page 21 and 22: dispersion E(k z ). Thus k z values
Page 23 and 24: where ɛ is infinitely small. Accor
Page 25 and 26: Langmuirs (1L=10 −6 torr·s) to c
Page 27 and 28: mean free path, E kin is the kineti
Page 29 and 30: a b c d e f graphite SiC f graphite
Page 31 and 32: Figure 3.3. XPS results showing dat
Page 33 and 34: Figure 3.5. Intensity map at -1 eV
Page 35 and 36: Chapter 4 Gap opening in epitaxial
Page 37 and 38: Figure 4.2. Observation of the gap
Page 39 and 40: the EDCs as well as the region of e
Page 41 and 42: Figure 4.7. Dispersions measured in
Page 43 and 44: Figure 4.9. (a-c) LEEM images taken
Page 45 and 46: Figure 4.10. Proposed mechanism for
Page 47 and 48: Chapter 5 Metal-insulator transitio
Page 49 and 50: Figure 5.2. (a) Dispersions through
Page 51 and 52: Figure 5.3. (a-f) Data taken throug
Page 53 and 54: Chapter 6 Dirac fermions and effect
Page 55 and 56: Figure 6.2. Linear Λ-shaped disper
Page 57 and 58: Figure 6.4. Detailed low energy dis
Page 59 and 60: Figure 6.6. Detailed dispersion nea
Page 61 and 62: Chapter 7 ARPES study of partially
Page 63 and 64: Figure 7.2. (a) Fermi energy intens
Page 65 and 66: direction, i.e. perpendicular to gr
Page 67 and 68: Figure 7.5. ARPES intensity map mea
Page 69 and 70:
Figure 7.7. (a) ARPES intensity map
Page 71 and 72:
Figure 7.9. (a) ARPES intensity map
Page 73 and 74:
19. Hüfner, S. Photoelectron Spect
Page 75 and 76:
59. Jiang, Y. J., Yao, D.-Y., Carls
Page 77 and 78:
99. Luk’yanchuk, I. A. & Kopelevi
Page 79 and 80:
List of Figures 1.1 (a) Sp 2 bondin
Page 81 and 82:
4.8 Thickness dependence of E D and
Page 83 and 84:
7.2 (a) Fermi energy intensity map.
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