1. Otto F. Sankey 1, Jun Li 1, Gil Speyer 2, and John Tomfohr 1,* 1 Department of Physics and Astronomy, 2 Department of Electrical Engineering Arizona State University, Tempe, AZ 85287-1504 *Duke University Electron tunneling current through single molecules - - molecular wires and nanoelectronics. Experimental Team: Stuart Lindsay, Nongjian Tao, G. Ramachandran, Anna Moore, Tom A. Moore, Devens Gust, Larry Nagahara (MOT) et al. BYU Sept 09, 2003

2. Outline N-Alkanes (CH 2 ) N Carotene Light Sensitive Octane

3. N-Alkanes (CH 2 ) N +ends

4. Octane dithiol --- Conducting AFM w/ 1.5nm Au Balls.

5. Fundamental Curve – Tunneling through one molecule

6. Au(111) in alkane-thiol “Target” molecule (carotene here) Au Nanoparticle Solvent (toluene) The “Fab”

8. The Main Physics: Fermi's Golden Rule. Elastic Tunneling Theory | | 2 1st order | | 2 order. T(E)=V+V G(E) V

9. How: Local Orbital DFT Self-Consistent with zero bias. Fireballs, Siesta, VASP(PW)

12. OctaneDithiol S-(CH 2 ) 8 -S Sandwiched between Au

13. DEPENDENCE ON LENGTH Periodic Molecules Bandstructure Techniques (Complex Bandstructure) Easy way to Find G For Understanding and making simple esitmates.

18. Fermi-Level Lineup

24. Bingqian Xu and Nongjian J. Tao. ASU EE. Science 301 1221 (2003) Aug. 29. Length Dependence of Single Molecule Current. N-alkanedithiols C8, C10, C12 Without Gold Balls.

34. Peptide Nanotubes Left-Right-Left-Right-… (8, 10,.. In ring) (D-Gln)-Phe Glutamine, Phenylalanine R=(CH2)2-CONH2, R=(CH2)-Phenyl. Hydrogen Bonded Donuts. (d>4nm) ABABABABAB…… (Expt. Scripps: Ghadiri, Ashkenasy)

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43. Carotene

47. β Dimerization, (Expt. 1.082) Tunneling Decay – Effect of Bond Alternation α=1.299

48. Theory (- - -)Trans, (….)Cis Expt. ( ____). Resistance Theory Trans (1.2GΩ), Cis(2.2GΩ) Expt. 5 GΩ Coulomb Blockade Fit. Theory (ooo) R2=constant Theory (ΔΔΔ) R2(V) Expt. ( ____) CAROTENE

49. Photochromic molecules: photoswitching Open Close LUMO HOMO E g  3.1eV E g  1.7eV UV Vis

50. Conductance: G(close)>>G(open) Closed --  way unbroken Open --  way broken Open Closed E g (Open)  2E g (Closed) Ψ H,L (Open)~on broken ring Ψ H,L (Closed)~on polyene backbone

51. Next: States in gap of OPEN

53. Next: States in gap CLOSED

55. Dynamics: Open  Closed 1 1’ 2 2’2’ 1 2’2’ 2 UV LUMO HOMO hνhν 2 2 ’ 11’ L(π*) H(π)

56. Dynamics: Open  Closed 1 1’ 2 2’2’ 1 2’2’ 2 UV LUMO HOMO hνhν 22’2’ 11’ L(π*) H(π) ASAS SASA

57. Movie Graphic of the HOMO(time) after excitation of light. Light takes an electron from the HOMO to the LUMO and the molecule starts to jiggle and reconfigure itself to a closed conformation.

58. Dynamics: Open  Closed 1 1’ 22’2’ 1 2’2’ 2 UV 2’2’ (π*) 33’ 3 3 2 HOMO(π) 3 2 3’ 2’2’ LocalizedDelocalized HOMO State character.

59. Dynamics: Closed  Open In progress -- multi-photon

60. I-V curves (Photochromic Molecule)

67. Click here for the movie