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