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
40 nm line width, 40 Gbit/inch2
HP Molecular Memory
Output: Stored Data
Input: Address
Molecular Memory
MRAM(Magnetic Random Access Memory)
Crossbar Memory Architecture
DRAM
1
0
HP Molecular Memory
The blue ring can shuttle back and forth along the axis of the rotaxane molecule, between the green and red groups.
Rotaxane molecules switch between high and low resis- tance by receiving a voltage pulse.
Collier et al., Science 289, 1172 (2000).
(Many Molecules)
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. (Some-thing like that happens in batteries).
Other Molecular Switches
Chen et al., Science 286, 1550 (1999)
Large On-Off Ratios
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
Quantum Dot
Molecular Switch
Self-Organizing Memory + Data Processor
Heath et al., Science 280, 1716 (1998)
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)
Miao et al., Phys. Rev. Lett. 101, 016802 (2008)
Local Hotspots Appear
after Switching
The latest from HP on how molecules
switch.
“Conductivity” of DNA
Berlin et al., Chem. Phys. 275, 61 (2002)
Tunneling at short distances (independent of temperature)
Hopping at large distances (thermally activated)
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) 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.
A Molecular Transistor
A schematic representation of Reed and Tour’s molecular junction containing a benzene-1,4-dithiolate SAM that bridges two proximal gold electrodes.
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 well-defined atom at the surface as con-tacts to a single molecule.
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)
Heath and Ratner, Physics Today, May 2003, p. 43
Many Ideas for Single Molecule Devices