Single Molecule Electronics
MCC075 Molecular Electronics
Kasper Moth-Poulsen, Chalmers University of Technology
September 2013
Kasper.moth-poulsen@chalmers.se
Outline
Lecture 1
Background and Motivation
Experimental Methods
Lecture 2 (Friday)
Molecular Design of Diodes, Switches etc.
Part 3
Self-assembly
What did we learn last time?
Statistics
“Contacting Individual Molecules Using Mechanically Controllable Break Junctions”
Jan van Ruitenbeek, Lecture Notes in Physics 680, 253-271 (2005)
The Vision II: Aviram and Ratner
• “the molecular rectifier”
A. Aviram and M. A. Ratner, “Molecular Rectifiers” Chem. Phys. Lett. Vol. 29, pp. 277-283, 1974.
A. Aviram and M. A. Ratner, “Molecular Rectifiers” Chem. Phys. Lett. Vol. 29, pp. 277-283, 1974.
Solution Based Systems
Rotaxanes
Initially No electrodes directly involved
Fraser Stoddard and co-workers eg early work: Pure &App/. Chem.,Vol. 65, No. 11, pp. 2351-2359,1993.
Important factors for the single molecule systems
The chemical anchor point: controls the self-assembly and is of
paramount importance for the nature of the electron transport
Molecular orbitals
Electrodes
Interface
Nature Nanotech. 4 (9), 551-556, 2009
Nature Nanotech. 4 (9), 551-556, 2009
Nature Nanotech. 4 (9), 551-556, 2009
Importance of the chemical contacts
Nano Letters 8 (1) 1-5, 2008.
Nature Nanotech. 4 (9), 551-556, 2009.
Solid state device
Resistance
b
~1 GΩ range
~0,63 Å-1
0.2-1 MΩ
~0,39 Å-1
STM measurement
Nano Letters 8 (1) 1-5, 2008.
Nature Nanotech. 4 (9), 551-556, 2009.
Intermezzo: Chemistry 101
Orbitals in Carbon and Chemical Bonds
Molecular Back-bone: does it matter?
Optical band gaps for ”infinite” polymers obtained
by extrapolation of monodisperse oligomers
1.4 - 1.8 eV
2.5 - 2.8 eV
2.3 eV
nsat = 10
2.2 - 3.2 eV
nsat = 20
Calculation
5.7 eV
nsat = 2
3.8 - 3.9 eV
nsat = 9
3.3 - 3.5 eV
nsat = 10
Slide courtesy of prof. MB Nielsen, Univ. Copenhagen
Molecular Back-bone: does it matter?
Kushmerik, TS Mayer and co-workers J. Phys. Chem. B 2004, 108, 2827-2832
Molecular Back-bone: does it matter?
Tunnelling vs Hopping,
where is the transition from small
molecules to polymers?
Seong Ho Choi, BongSoo Kim, C. Daniel Frisbie, Science 2008
Tunnelling vs Hopping
Hopping is temperature dependent
Tunnelling is NOT temperature dependent
Seong Ho Choi, BongSoo Kim, C. Daniel Frisbie, Science 2008
Molecular Switches, 3 types
1) Conformation switches
2) Electronic switches
3) Translational switches
Conformational Switch
“Microfabricated Molecular Break Junction”
Emanuel Lörtscher, Jacob W. Ciszek, James Tour, and Heike Riel, Small 2006, 2, No. 8-9, 973 – 977
Switch
No-Switch
Emanuel Lörtscher, Jacob W. Ciszek, James Tour, and Heike Riel, Small 2006, 2, No. 8-9, 973 – 977
“Switching Driven by rotation in the central bond in the bipyridine unit, induced by
alignment of the dipoles in the Nitro groups with the electric field”
Ferdinan Evers and co-workers small 2009, 5, No. 19, 2218–2223
Conductivity and torsion angle: detailed investigation
Conductivity vs torsion angle
Mayor, Wandlowski and co-workers Nano Lett. 2010, 10, 156-163
Molecular Switches, 3 types
1) Conformation switches
2) Electronic switches
3) Translational switches
Tunneling barrier
Source
Tunneling barrier
3-terminal devices
Drain
”Diamond plot”
Kubatkin et al. Nature 2003
Molecular Back-bone: does it matter?
Optical band gaps for ”infinite” polymers obtained
by extrapolation of monodisperse oligomers
1.4 - 1.8 eV
2.5 - 2.8 eV
2.3 eV
nsat = 10
2.2 - 3.2 eV
nsat = 20
Calculation
5.7 eV
nsat = 2
3.8 - 3.9 eV
nsat = 9
3.3 - 3.5 eV
nsat = 10
Electron delocalization via cross conjugation is less efficient than via linear conjugation
Slide courtesy of prof. MB Nielsen, Univ. Copenhagen
Cross-conjugation, where does it come
from?
• It is all pz orbitals so why is the delocalization
different?
So surprizing that the physists has come up with
their own name for it:
“Quantum interference”
Chemist might say: we have known about it all the time:
ortho/para vs meta directing? Michael addition?
Position of the Anchor Groups
para:
linear conjugation
meta:
cross conjugation
Smaller conductance
(by 2 orders of magnitude)
M. Mayor, H.B. Weber, J. Reichert, M. Albing, C. von Hänisch, D. Beckmann, M. Fischer,
Angew. Chem. Int. Ed. 2003, 42, 5834-5838.
Switching via changes in electronic states: Cross Conjugation and Quantum Interference
Hummelen and Solomon
dx.doi.org/10.1021/ja202471m |J. Am. Chem. Soc. XXXX, XXX, 000–000
Synthesis and initial Charactarisation: Hummelen and co-workers Org. Lett., 2006, 8 (11), pp 2333–2336
Transport and Thery „evidence of Quantum Interference” JACS ASAP 2011 dx.doi.org/10.1021/ja202471m
Ox
Red
Brønsted-Nielsen and co-workers Org. Lett. 2006 Vol. 8, No. 6 1173-1176 J. Org. Chem, Vol. 73, No. 8, 2008
Conjugation/cross conjugation photoswitch
D. Dulic , S. J. Van Der Molen , T. Kudernac , H. T. Jonkman ,
J. J. D. de Jong , T. N. Bowden , J. van Esch , B. L. Feringa ,
B. J. van Wees , Phys. Rev. Lett. 2003 , 91 , 207402 .
Molecular Switches
1) Conformation switches
2) Electronic switches
3) Translational switches
Dripling C60 for six weeks
Danilov/Kubatkin
D
Hedegård
Danilov and Kubatkin, NANO LETTERS Volume: 8 Issue: 8 Pages: 2393-2398
TPS
• We have discussed 3 types of switches,
describe each type of Switch
How to Switch a Molecular Switch
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1) thermal activation
2) level allignment (gating)
3) redox chemistry with reorganisation
4) photoreaction
5) magnetic switch
level allignment (gating)
Kubatkin nature 2003
Redox Switch
Redox Switch 2
Photo Switches
Photo Switch
Magnetic Switch
TPS
• Describe the different ways to activate
switches
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1) thermal activation
2) level allignment (gating)
3) redox chemistry with reorganisation
4) photoreaction
5) magnetic switch
“Molecular Trains: and organized molecular tranlational switch”
Molecular Machines
Fraser Stoddart and co-workers
Summary
Molecular Switches:
Conformational Switches
Electronic Switches
Translational Switches
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•
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•
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1) thermal activation
2) level allignment (gating)
3) redox chemistry with reorganisation
4) photoreaction
5) magnetic switch
Seminar on Oct 5
Methods of contacting molecules
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Scalability?
Tunability of a nanogap?
Single-molecule device possible?
Possible artifacts
Is gating possible?
For industry or for research?
How was it made?
How was the molecules designed?
What kind of switching?
5 min report (3 slides) + 1 A4 Written summary
e-mail your presentation before oct 3 to
mkasper@chalmers.se