Otto F. Sankey 1, Jun Li 1, Gil Speyer 2, and John Tomfohr 1,* 1 Department of Physics and...
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Transcript of Otto F. Sankey 1, Jun Li 1, Gil Speyer 2, and John Tomfohr 1,* 1 Department of Physics and...
Otto F. Sankey1 , Jun Li1, Gil Speyer2, and John Tomfohr1,*1Department of Physics and Astronomy, 2Department of Electrical EngineeringArizona 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
Outline
• N-Alkanes (CH2 )N
• Carotene
• Light Sensitive
Octane
N-Alkanes (CH2)N+ends
Octane dithiol --- Conducting AFM w/ 1.5nm Au Balls.
Fundamental Curve – Tunneling through one molecule
Au(111) in alkane-thiol“Target” molecule(carotene here)
Au Nanoparticle
Solvent (toluene)
The “Fab”
The Main Physics: Fermi's Golden Rule.
LRRL ,,
)]2/(2/[2||)(||2
eVREeVLERLETL
Elastic Tunneling Theory
|<i| V | f>|2 1st order |<i| T | f>|2 order.T(E)=V+V G(E) V
How: Local Orbital DFT
Self-Consistent with zero bias.
Fireballs, Siesta, VASP(PW)
OctaneDithiol
S-(CH2)8-S
Sandwiched between Au
DEPENDENCE ON
LENGTH
Periodic Molecules
Bandstructure Techniques
(Complex Bandstructure)
Easy way to Find G
For Understanding and making simple esitmates.
E
Fermi-Level Lineup
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.
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)
Clicking will bring up netscape. A plugin will play the movie. (Hit BACK to return. Don’t close the window!)
Click here
Carotene
β
Dimerization, (Expt. 1.082) dc cdc c
Tunneling Decay – Effect of Bond Alternation
α=1.299
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
Photochromic molecules: photoswitching
Open Close
LUMOLUMO
HOMO HOMOEg3.1eV Eg1.7eV
UV
VisRH
RH
S SRR
H
HS S
Conductance: G(close)>>G(open)
• Closed -- way unbroken Open -- way broken
Open Closed
• Eg(Open)2Eg(Closed)•ΨH,L(Open)~on broken ring ΨH,L(Closed)~on polyene backbone
RRH
HS S
RH
RH
S S
Next: States in gap of
OPEN
Next: States in gap
CLOSED
Dynamics: Open Closed
RH
RH
S S
RRH
HS S
1 1’
2 2’
1 1’2’2UV
LUMO
HOMOhν
2 2’1 1’L(π*)
H(π)•
Dynamics: Open Closed
RH
RH
S S
RRH
HS S
1 1’2 2’
1 1’2’2UV
LUMO
HOMOhν
2 2’1 1’L(π*)
H(π)•
AS
SA
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.
Dynamics: Open Closed
RH
RH
S S
RRH
HS S
1 1’2 2’
1 1’2’2
UV
2’
(π*)•
3 3’ 3 3’
3 3’2HOMO(π)
32 3’2’
Localized Delocalized
HOMO
State character.
Dynamics: Closed Open
In progress -- multi-photon
I-V curves (Photochromic Molecule)
S SH
HSH SH S S
H
HSH SH
S S
H
HSH SH
Click here for the movie