Single Molecule Electronics. [email protected] Arizona Biodesign Institute. Single molecules as a tool for understanding. More Single molecules for better understanding. Photosynthesis and single molecule electronics The ASU-Physics-Chemistry-Engineering-Motorola group:. The Program.
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Single Molecule Electronics
Arizona Biodesign Institute
Single molecules as a tool for understanding
More Single molecules for better understanding
Photosynthesis and single molecule electronics
The ASU-Physics-Chemistry-Engineering-Motorola group:
Measure Single Molecule in well-defined conditions
Compare with theory (repeat as needed!)
‘Calibrated’ molecules and contacts for devices
Make fixed-gap (useful? T-dep?) devices
The molecule-metal contact problem
Many Few-Molecule-Devices have been made but measurements/theories generally do not agree:
For example, DNA is:
AN INSULATOR (D. Dunlap et al. PNAS 90, 7652, 1993)
A SEMICONDUCTOR (D. Porath et al, Nature 403,635, 2000)
A CONDUCTOR(Fink and Schoenberger, Nature 398, 407,1999)
A SUPERCONDUCTOR (A.Y. Kasumov et al. Science 291, 280, 2001)
Making Single Molecule Junctions
(Science 294, 571, 2001)
Alkanedithiols – STM Images
NI(V )/N (nA)
IV-Curves are integral multiples
Two Models for ‘quantized ‘ data
Histogram of curve multipliers
IV-Curves of bonded molecules not very stress dependent!
Current not stress-dependent – through bond?
(Nanotechnology 13 5-14, 2002)
I is closer to theory for bonded molecules
Comparison with electrochemistry:
K=105s-1, EA=21kJ/m, R(C8)=300M
More chain lengths give (V)
(J. Phys. Chem. B 106 8609-8614, 2002 )
Clue: I-V doesn’t fit tunneling model well
What if the top contact is not so good? Coulomb Blockade?
Coulomb Blockade: Quantized charge transfer
Coulomb Blockade fits
(Removes Beta anomaly)
r1 = 1M
c1 = 0.318aF
(from fitting C8)
r8 = 128.36M
r10 = 252M
r12 = 875M
(c1, r1 fixed)
C8=c10 =c12= 0.085aF
Good agreement for I,
- Phenylene-ethylenine oligomers
-Technique reveals mobility of Au contacts
(J. Phys. Chem. B, 107, 6162-6169, 2003)
Simple Tunneling with Coulomb Blockade fits well
No ‘free’ parameters
Carotene easily oxidized but vibronic contribution not dominant
and Negative Differential Resistance
Applied Physics Letters 81 3043-3045 (2002)
Single Molecule NDR
Asymmetry, but molecules NOT oriented?
c.f. Reichert et al. PRL 88 2002
Confirms NDR but see non-reversible behavior
Single Molecule Bonding Fluctuations(Science 300 1413, 2002)
Single Molecule Bonding Fluctuations – Property of Au-S
Transport in gold-n-alkane-gold fits ab-initio tunneling calculations well: One molecule, well defined environment.
Gold nanocluster introduces Coulomb Blockade
Carotene – good agreement with tunneling calculations
Phenylene-ethylenine oligomers, confirm NDR.
Technique reveals mobility of Au contacts
Gold filaments stretch – maximum force ca 1nN
Xu, Xiao, Tao, JACS 2003
Major peaks are right peaks
Kubatkin et al. (2003) – (but3 devices/paper)
EBL, Electrochemistry, Electromigration
Molecule free molecular transistor
Atomic-scale control needed!
Our Fixed Gaps: 10% “Success Rate”?
What we think we know
What we don’t know/Can’t do