Esiste la nanoscienza?

Dimensione: px

Iniziare la visualizzazioe della pagina:

Download "Esiste la nanoscienza?"

Tito Spano
7 anni fa
Visualizzazioni

1 Esiste la nanoscienza? Possiamo definire uno stato della materia in cui le proprietà dipendono dalla forma e dalla dimensione? Maria Grazia Betti and Carlo Mariani Dipartimento di Fisica, Università di Roma La Sapienza Nanoscienza/nanotecnologia Architettura/Ingegneria di nuove strutture atomiche e molecolari con particolari funzioni

2 La gap del silicio in funzione delle dimensioni

3 Length Scales of Nanostructures Quantum Electrostatic Magnetic Quantum Well: Quantum Well Laser Quantum Dot: Single Electron Transistor Magnetic Particle: Hard Disk d a = V1/3 E2 E1 l Room temperature operation requires a characteristic energy larger than the thermal energy kt = 25 mev Level Spacing Charging Energy 3h /8ml 2e2/ d ( Si) l < 7 nm d < 9 nm 2 2 Spin Flip Barrier ½M2a3 (MFe) a > 3 nm

4 More Length Scales: Scattering Lengths Elastic E = 0 Inelastic E > 0 Scattering Potential Diffraction, Phase Shift ElectronElectron e - ElectronPhonon h+ e- phonon e- Semic: Metal: large large large 1000 nm Trapping at an Impurity e- e- 10 nm 100 nm e- (Room temperature, longer at low temp.) Consequences: Ballistic electrons in smallest transistors (extra speed gain versus Ohmic electrons) Depletion of electrons near an interface with traps

5 Biological Length Scales

6 DNA Tobacco Mosaic Virus (TMV) 3.4 nm pitch 300 nm 10 base pairs 2 nm 18 nm

8 Nanostructures in Real Life Gate Oxide in a Transistor Quantum Well Laser GMR Reading Head for Hard Disks Particles in Magnetic Storage Media

9 Supported Catalysts Rhodium nanoparticles on a TiO2 support

10 Zeolites O Si,Al Tetrahedra Channels for Ions

11 transistor di Shockley (1947) Si N-MOS transistor

12 Electrons in the Conduction Band p-type n-type Holes in the Valence Band Nobel Prize in Physics 2000: Alferov Kroemer Trap electrons and holes in a narrow gap material. Discrete quantum levels lead to increased density of states.

13 6 nm

14 ... Quantized conductance atomic switch K. Terabe1,2, T. Hasegawa1,2,3, T. Nakayama1,2,3 & M. Aono1,2,3

16 nano-electronics with new molecular architectures Top down versus Bottom up

17 Transistor scaling Aggressive scaling in the last years 22 nm node: Intel Core i7, i5 from:

18 single-molecule diode Organic Diode: Reed et al. Science 286, 1550 (1999). nano-chain device

19 nano-electronics with new molecular architectures from the single-molecule device..to the integrated circuit Organic Diode: Reed et al. Science 286, 1550 (1999). S.S. Kim et al., Thin Solid Films (2002) 19 SAM Halik et alii, Nature 431, 963 (2004)

20 from inorganic to organic semiconductors inorganic semiconductors.. organic semiconductors Bloch states inorganic semiconductors van der Waals interactions organic semiconductors mobility (300K) ~bonds 103 cm2/vs covalent Bloch states mobility (300K) ~ 103 cm2/vs band transport excitons ~ 10-3 ev polarons van der Waals interactions mobility (300K) -> 35 cm2/vs* polarons mobility (300K) -> 35 cm2/vs* hopping? excitons ~ 10-1 ev? band transport *Jurchescu et alii, Appl. Phys. Lett. 84, 3061 (2004)

21 graphene GRAPHENE Astonishing fundamental properties: massless Dirac fermions Potential electronical applications: mobility 10 times bigger than Si Novoselov et al., Nature 438, 197 (2005) Geim et al., Nature Mat. 6, 183 (2007)

22 graphene Quasi free standing graphene Epitaxial growth on transition metal surfaces: 5d - Ir(111), Pt(111) 4d - Ru(0001), Rh(111) 3d - Ni(111) Increase of the interaction strength: - more graphene corrugation - less C / TM distance - gap opening at K (as SiC) - hybridization π - d Preobrajenski et al., Phys. Rev. B 78, (2008) Lacovig et al., Phys. Rev. Lett., 103, (2009) STM, local imaging LEED, diffraction M. Scardamaglia et al., J. Nanop. Res. 13, 6013 (2011) Pletikosic et al., Phys. Rev. Lett. 102, (2009)

23 Il futuro dei nostri smartphones? Il grafene è il materiale ideale per elettrodi trasparenti (conduttore e trasparente) A giugno 2010 un gruppo Coreano ha realizzato il primo touchscreen a base di grafene S. Bae et al. Nature Nanotechnology 5, 574 (2010)

24 Il premio EPS che demmo a Geim nel 2008 Andre Geim 22nd Condensed Matter Division of the European Physical Society, Roma, August 2008

Documenti analoghi

Il carbonio: dalla grafite al grafene e al fullerene. C. Mariani

Il carbonio: dalla grafite al grafene e al fullerene C. Mariani Carbon as brick for building-up exotic systems carbon fullerenes: a selection C 60 C 28 C 12 C 60 C 540 C 60 Buckminster Fullerene (Free