Carbon Nanotube Field-Effect Transistors and their possible applications

1. D.L. Pulfrey Department of Electrical and Computer Engineering University of British Columbia Vancouver, B.C. V6T1Z4, Canada pulfrey@ece.ubc.ca http://nano.ece.ubc.ca Carbon Nanotube Field-Effect Transistors and their possible applications Day 4B, May 30, 2008, Pisa

2. Hybridized carbon atom  graphene monolayer  carbon nanotube 2p orbital, 1e-(-bonds) Single-Walled Carbon Nanotube L.C. Castro

3. Structure (n,m): (5,2) Tube VECTOR NOTATION FOR NANOTUBES Zig-zag (6,0) Chiral tube Armchair (3,3) Adapted from Richard Martel

4. CHIRAL NANOTUBES Armchair Zig-Zag Chiral From: Dresselhaus, Dresselhaus & Eklund. 1996 Science of Fullerenes and Carbon Nanotubes. San Diego, Academic Press. Adapted from Richard Martel.

5. Graphene sheet 2D E(k//,k) Quantization of transverse wavevectors k (along tube circumference)  Nanotube 1D E(k//) Nanotube 1D density-of-states derived from [E(k//)/k]-1 Get E(k//)vs. k(k//,k) from Tight-Binding Approximation Carbon Nanotube Properties

6. E-EF (eV) vs. k|| (1/nm) Eg/2 (5,0) semiconducting (5,5) metallic

7. Properties relevant to devices discussed at Pisa • low m* - maybe good for tunneling transistor to reduce sub-threshold slope • low m* and long mfp - high mobility - good for ION, gm, fT • - high conductivity - good for interconnects • - also, may help collection in polymer solar cells • m*e = m*h - ambipolar conduction, maybe good for electroluminescence • cylindrical shape - good for combating SCE Other device possibilities: • molecular size - may be useful as a molecular sensor • biological compatibility - perhaps devices can be assembled via biological recognition.

8. Metallic CNTs as interconnects T. Iwai et al., (Fujitsu), 257, IEDM, 2005

9. CNT-assisted organic-cell photovoltaics Keymakis, APL, 80, 112, 2002

10. Is there a DIGITAL future for nanotubes?

11. Tennenhouse04

12. H. Dai, APS, March, 2006

13. Fabricated Carbon Nanotube FETs 20nm -ve SB R.V. Seidel et al., Nano Letters, Dec. 2004 50nm MOS A. Javey et al., Stanford

14. Small m*: sub-threshold slope improvement Non-thermionic process: S < 60 mV/dec !! J. Appenzeller et al., IEEE TED, 4, 481, 2005

15. Carbon Nanotube FETs for HF 300 nm SB-CNFET A. Le Louarn et al., APL, 90, 233108, 2007 Single-tube drawbacks: Imax~ A Zout ~ k

16. High-frequency Carbon Nanotube FET A. Le Louarn et al., APL, 233108, 2007

17. Experimental results for fT "Ultimate"

18. Schrödinger-Poisson Solver • Need full QM treatment to compute: • -- Q(z) within barrier regions • -- Q in evanescent states (MIGS) • -- resonance, coherence • -- S  D tunneling. D.L. John et al., Nanotech04, 3, 65, 2004.

19. Schrödinger-Poisson Normalization S CNT D Unbounded plane waves

20. E kz kx kx MODE CONSTRICTION and TRANSMISSION Doubly degenerate lowest mode T CNT (few modes) METAL (many modes)

21. Quantized Conductance In the low-temperature limit: Interfacial G: even when transport is ballistic in CNT 155 S for M=2

22. Carbon nanotube FETs: model structures SB-CNFET K. Alam et al., APL, 87, 073104, 2005 C-CNFET D.L. Pulfrey et al., IEEE TNT, 2007

23. Propagation velocity and fT

24. FET QG+qg _ + + + + _ + _ QD+qd QS+qs qe + _ + + _ + qe QB+qb QC+qc Image charges in transistors BJT _ + _ + _ + QB QC FET: qg |qe| BJT: qb < |qe|

25. Comparison of vband:Si NW, Si planar and CNT (11,0) CNT Tight-binding Si NW and planar Si J.Wang et al., APL, 86, 093113, 2005 vb,max (CNT) higher by factor of ~ 5

26. CN oxide Gate Si MOSFET and CNFET: comparison S. Lee et al., IEDM, 241, 2005

27. AMBIPOLAR CONDUCTION Experimental data: M. Radosavljevic et al., arXiv: cond-mat/0305570 v1 Vds= - 0.4V Vgs= -0.15 +0.05 +0.30

28. Mobile electroluminescence and the LET DRAIN SOURCE Gate-controlled light emission Ambipolar CNFET McGuire and Pulfrey, Nanotechnology, 17, 5805, 2006

29. Biomolecular sensing schemes 1. Electroluminescence Spectrometer and/or Photodetector Analyte Source Drain Gate + + VDS VGS

30. CN biomolecular sensors • CARBON NANOTUBES: • size compatibility with biomolecules, • exposed surface, • interactions that modify band structure, • change in LDOS. Gruner, Anal. Bioanal. Chem., 384, 322, 2006

31. Biomolecular sensing schemes 2. Conductance Star et al., Nano Lett., 3(4), 459, 2003

32. Sensing amino acids, dipeptides Protein building blocks Alanine-Glutamine, Glycine-Glutamine: - reduces muscle  wasting in inactive patients. Arginine-Glutamine: - maintains muscle mass - boosts mucosal immunity. Glutamine-Glutamine: - aids glutathione biosynthesis. Tyrosine-Tyrosine: - restores Phe:Tyr ratios in patients with renal disease.

33. Molecular Dynamics GROMACS • Atomic positions Density Functional Theory ATOMISTIX • Electronic band structure • LDOS as f(E, r, θ, z) • Transport • Current • Electroluminescence Non-Equilibrium Green's Function ATOMISTIX Simulation approach

34. MD results (12,11) CNs Dipeptides: Asparagine (hydrophilic) Isoleucine (hydrophobic) Abadir et al., IJHSE, accepted.

35. Single-biomolecule detection Asparagine (top) and isoleucine (bottom) adsorbed on CNT between Al electrodes Abadir et al., IEEE NANO Conf.

36. Self-assembly of DNA-templated CNFETs K. Keren et al., Science, 302, 1380, 2003