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Graphene FET: High Saturation Velocity

Saturation velocity. v sat (10 8 cm/s). V top = -3 V. V top = -2 V. E F (eV). For comparison:. V top = -1.5 V. v Fermi = 1x10 8 cm/s. Silicon: 1x10 7 cm/s. V top = 0 V. GaAs: 0.7x10 7 cm/s. V top Dirac = 2 V @ V g = -40 V. Operation current density > 1 mA/ m m.

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Graphene FET: High Saturation Velocity

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  1. Saturation velocity vsat (108 cm/s) Vtop = -3 V Vtop = -2 V EF (eV) For comparison: Vtop = -1.5 V vFermi= 1x108 cm/s Silicon: 1x107 cm/s Vtop = 0 V GaAs: 0.7x107 cm/s VtopDirac = 2 V @ Vg = -40 V Operation current density > 1 mA/mm Graphene FET: High Saturation Velocity Meric, Han, Young, Kim, and Shepard (2008)

  2. Graphene Device Fabrication • Developing Graphene Nanostructure Fabrication Process graphene Contacts: PMMA EBL Evaporation Graphene patterning: HSQ EBL Development Graphene etching: Oxygen plasma Local gates: ALD HfO2 EBL Evaporation • Graphene device structure with local gate control Oezyilmaz, Jarrilo-Herrero and Kim APL (2007)

  3. Graphene Nanostructures AB Ring Quantum Dot Graphene with local barrier Goldhaber-Gordon (Stanford) Geim (Manchester) Morpurgo (DELFT) Graphene nanoribbons & nanoconstrictions Graphene PN junctions Graphene Side Gates Ensslin (ETH) Marcus (Harvard) Kim (Columbia)

  4. Dirac Particle Confinement Graphene Gold electrode W W 1 mm 10 nm < W < 100 nm x y Graphene nanoribbon theory partial list W Zigzag ribbons Egap~ hvF Dk ~ hvF/W Graphene Nanoribbons: Confined Dirac Particles

  5. 100 Eg (meV) Eg = E0 /(W-W0) 10 P1 P2 P3 P4 D1 D2 1 0 30 60 90 W (nm) Scaling of Energy Gaps in Graphene Nanoribbons Han, Oezyilmaz, Zhang and Kim PRL (2007)

  6. G (e2/h) 10-7 10-5 10-3 10-1 SEM image of device Top gate source drain top gate Hf-oxide graphene 1 mm 30 nm wide x 100 nm long 75 OFF 10-1 50 10-2 25 G (e2/h) VBG (V) 10-3 0 10-4 -25 10-5 -50 10-6 -75 -8 -4 0 4 8 -8 -4 0 4 8 VLG (V) VLG (V) Top Gated Graphene Nano Constriction source drain graphene SiO2 Back gate

  7. Son, et al, PRL. 97, 216803 (2006) Eg (meV) 2mm q (degree) 40 20 0 60 0 30 90 Graphene Nanoribbons Edge Effect Crystallographic Directional Dependence Rough Graphene Edge Structures

  8. Transport ‘gap’ Localization of Edge Disordered Graphene Nanoribbons See also: Gunlycke et al, Appl. Phys. Lett. 90 (14), 142104 (2007). Areshkin et al, Nano Lett. 7 (1), 204 (2007) Lherbier et al, PRL 100 036803 (2008) Querlioz et al., Appl. Phys. Lett. 92, 042108 (2008)

  9. Graphene Electronics: Challenges Pros: High mobility High on-off ratio High critical current density Small channel length Small gate capacitance Large Fermi velocity Con: Controlled growth tunability of band gaps Edge control This can be turned into advantage: doping site, functionality, and etc…

  10. Graphene quantum dot Band gap engineered Graphene nanoribbons FET (Manchester group) Nonconventional Devices Graphene Veselago lense Graphene psedospintronics Graphene Spintronics Son et al.Nature (07) Cheianov et al.Science (07) Trauzettel et al.Nature Phys. (07) Graphene Electronics: Conventional & Non-conventional Conventional Devices

  11. Non-local Spin Transport and Spin Coherence Length Spin Relaxation Length ~ 2 mm @ RT

  12. Beyond Simple Spin Transport in Graphene

  13. Coherent Electron Wave Function Manipulation

  14. 1 Pd (under HfO2) Conductance (mS) SWCNT (under HfO2) 0 Pd (over HfO2) 1 mm HfO2 on SiO2/Si+ Pd (under HfO2) 20 nm 60 nm Carbon Nanotube Superlattice Purewal, Takekosh, Jarillo-Herrero, Kim (2008) Kouwenhoven PRL (1992)

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