Graphene presentation
- 1. GRAPHENE THE NEW WONDER MATERIAL
- 2. WHAT IS GRAPHENE? Graphene is a flat monolayer of carbon atoms packed into two-dimensional honeycomb structure. + = Graphene is expected to replace silicon-based electronic devices. Graphene-based devices are predicted to be substantially faster, thinner and more efficient.
- 3. NOBEL PRIZE 2010 Nobel Prize in Physics for 2010 was awarded to Sir Andre Geim and Sir Kostia Novoselov “for ground-breaking experiments regarding the two-dimensional material graphene”
- 4. PROPERTIES OF GRAPHENE • • • • Highly Conductive Very Strong 2D Honeycomb Structure Extremely Thin
- 5. ELECTRONIC PROPERTIES Electronic dispersion of graphene ordinary semiconductor graphene Electrons in graphene behave like massless relativistic (Dirac) particles
- 6. Semiconductor Band Width No current can flow when an electrical field is put across a semiconductor because electrons cannot flow from the valence band (red) to the conductive band (blue). Electrons need energy to pass from the valence band to the conductive band. This energy is provided by photons. The closer the two bands (smaller the band width) the less energy is required to excite the electrons to the conductive band. Energy of photons: E=ħω P=ħk where k is a wave vector ω=Ck Therefore… E=CP
- 7. Graphene Band Width When graphene is put in an electric field there is no band width a current can flow as electrons can move from the valence band to the conductive band without the need for extra energy i.e. from a photon. Energy of Photons: E=VfP where Vf is 106 ms-1 Similarity: Energy of photons in both cases are proportional relationships. EαP but with different constant values.
- 8. Fermi Levels Pauli Principle: Because of the opposite spin states fermions cannot share the same energy level/state. The highest energy level occupied by a fermion is known as the Fermi level.
- 9. A-Level Physics! Wave-particle duality Electromagnetism Photons Photoelectric effect Waves Double slit interference You should know that electrons demonstrate properties of both particles and waves also…
- 10. Wave Function, ψ ψ Describes the quantum state of a particle and how it behaves, in the case of graphene, we’re look ψ is complex – has real and imaginary parts |ψ|2, is real, |ψ|2 = ψ x ψ* |ψ|2 corresponds to the probability density of finding a particle in a given place in a given time The probability of finding a particle between two x values:
- 11. Quantum Tunnelling Quantum tunnelling is a phenomenon wher In classical physics the electron will rebound In quantum mechanics the electron has a sm In quantum electrodynamics such as if the b
- 12. Structure of Graphene Graphene is a lattice that can go on to infini Unit cell shows it’s the symmetrical at this p Because of this you get a brillouin zone A B Py K K’ K K’ PX S = +1 K S = -1 X K’
- 15. Why Do Electrons in Graphene Behave Differently?