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Towards Single Molecule Electronics
Can a single molecule behave like a
diode, transistor (switch), memory ?
If that’s possible, how long will the molecule last ?
First, let’s look at many molecules acting in parallel.
Nitzan and Ratner, Science 300, 1384 (2003); Heath and Ratner, Physics Today, May 2003, p. 43
HP Molecular Memory
40 nm line width, 40 Gbit/inch2
Molecular Memory
DRAM
Input:
Address
Crossbar Memory
Architecture
MRAM
(Magnetic Random Access Memory)
1
0
Output:
Stored
Data
HP Molecular Memory
Rotaxane molecules switch
between high and low resistance by receiving a voltage
pulse.
The blue ring can shuttle back
and forth along the axis of the
rotaxane molecule, between
the green and red groups.
HP Molecular Memory
Change the resistance between
low and high by voltage pulses.
Is the resistance change really due
to the rotaxane ring shuttling back
and forth? Other molecules exhibit
the same kind of switching.
One possible model is the creation
and dissolution of metal filaments
which create a short between the
top and bottom electrodes. (Something like that happens in batteries).
(Many Molecules)
Collier et al., Science 289, 1172 (2000).
Other Molecular Switches
Large On-Off Ratios
Chen et al., Science 286, 1550 (1999)
Robert F. Service,
Science 302, 556
(2003).
Synthesis of a Rotaxane Molecule
Amabilino and Stoddart, Chemical Reviews 95, 2725 (1995).
Some Fancy Molecules
Rotaxane
Catenane
Pretzelane
Handcuffcatenane
Data Storage via the Oxidation State of a Molecule
Electrochemistry
Self-Organizing Memory + Data Processor
People have been thinking about
how to combine memory with logic
(= a microprocessor) in a molecular
device.
Self-assembly is the preferred
method. It generates errors, though.
They need to be absorbed by a
fault-tolerant architecture (e.g. in the
HP Teramac)
Quantum
Dot
Heath et al., Science
280, 1716 (1998)
Molecular Switch
Local Hotspots Appear
after Switching
The latest from HP
on how molecules
switch.
Miao et al., Phys. Rev. Lett.
101, 016802 (2008)
“Conductivity”
of DNA
Tunneling at short distances (independent of temperature)
Hopping at large distances (thermally activated)
Berlin et al., Chem. Phys. 275, 61 (2002)
Using a Single Molecule
Using a Single Molecule
Coulomb Blockade
Magnetic (Kondo) Resonance
at the Fermi level (zero voltage)
Park et al., Nature 417, 722 (2002)
Using a Few Molecules
Observe tunneling through 1, 2, 3, 4, 5 alkanethiol molecules
Cui et al., Science 294, 571 (2001)
A Molecular Transistor
(a) Structures of the long and short linked cobalt coordinated terpyridine thiols used
as gate molecules. (b) A topographic AFM image of the gold electrodes with a gap.
(c) A schematic representation of the assembled single atom transistor.
Break Junctions
At the beginning of single molecule
electronics, break junctions were very
popular: Just crack a thin Au wire open
in a vice and adjust the width of the
crack with piezos (as in STM). Then
pour a solution of molecules over it.
Alternatively, one can burn out the
thinnest spot of a thin Au wire by
running a high current density through
it (using the effect of electromigration).
These days, many try to achieve a
well-defined geometry using a STM
or AFM, with a well-defined atom at
the end of the tip and another welldefined atom at the surface as contacts to a single molecule.
A schematic representation of Reed and Tour’s molecular junction containing a
benzene-1,4-dithiolate SAM that bridges two proximal gold electrodes.
Conductance through a C60 Molecule
Distance dependence tells whether it is tunneling (exponential decay)
or quantum conductance through a single or multiple orbitals (G0).
Kröger et al., J. Phys. Condend. Matter 20, 223001 (2008)
Many Ideas for Single Molecule Devices
Heath and Ratner, Physics Today, May 2003, p. 43