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Structure and Transport Properties of Organic Low-Dimensional Systems for Application to Information Technology

Objective

Microelectronics is developing and advancing by making the electron-transporting structures smaller through more sophisticated microfabrication. Molecular electronics seeks to take the smallest building block, the organic molecule, and assemble it into structures that can be used for information processing.
This Action aimed to assemble electron-transporting molecules and molecules possessing dipole moments. The goal was to achieve molecular-scale information processing by the manipulation and control of charge motion or the orientation of molecular dipoles.
Organic molecule structures that can be used in molecular electronics were addressed. 2 kinds of organic molecules were studied: conjugated molecules (ie, those with electron transport properties) to be used for wiring, and lipid molecules (ie, with defined dipole moments) which can be used to represent information. The molecules were controlled and assembled by the Langmuir Blodgett (LB) technique into films. New knowledge about molecular scale information technology (IT) devices will be derived.

New phthallocyanine and bis-diacetylene molecules have been synthesized and characterized and new donor and conjugated wire acceptor moleculeshave been prepared and assembled as LB films. A new ladder polymer has been synthesised and is capable of acting as a superior molecular wire, as both parts of the ladder have to be simultaneously defective to block wire operation.
LB films of diacetylene polymers and new phthallocyanine molecules have been prepared.
Computer modelling of the LB film has been set up in 2 contrasting ways. The first is detailed molecular dynamics and the second models molecular groups as cellular automata.
An automated system to view dipolar moments by fluorescent labelling now exists. These are being studied in phospholipids.
A prototype now exists for a new scanning tunnelling microscope (STM) and progress has been made on the related scanning near field optical microscope (SNOM), with the creation of a novel SNOM tip; plasma propagating on a fine wire to a tip convert to light on reaching the tip.
Photoelectrons have been timed in their transit across up to 48 molecular layers. Recently, insertion of 2 molecular blocking layers has been shown to stop the electron transit, ie, electron motion is manipulated on a molecular scale. Designs for memories in which electrons are shifted between layers, in a controlled manner, by electric fields or by light pulses, have been developed.
APPROACH AND METHODS
-The molecules were assembled into films by the LB technique.
-New organic molecules were synthesised. These were designed both for their electron-transporting properties and for their behaviour in LB film formation.
-Techniques successful in surface chemistry (such as scanning electron microscopy, STM) were used to characterise the LB films produced.
-Two techniques were used to structure the films and electrode systems: laser ablation and electron-beam lithography.
-The motion of photo-electrons was studied on the picosecond time-scale. Dipolar domains were studied by optical techniques.
Computer modelling was used to:
-Model the intermolecular interactions and packing of the LB film structure. This aids the search for better molecules.
-Study elemental information processing steps, and their collective behaviour, both for information as charge, and information as dipole orientation.
PROGRESS AND RESULTS
New phthallocyanine and bis-diacetylene molecules have been synthesised. Inter-partner work on their characterisation has been conducted. New donor-conjugated wire-acceptor molecules have been prepared and assembled as LB films. A new ladder polymer has been synthesised. It is capable of acting as a superior molecular wire, as both parts of the ladder have to be simultaneously defective to block wire operation.
LB films of diacetylene polymers have been prepared. Rapid electron motion on a polymer backbone in the plane of the film has been seen for the first time. These films have been used in work on ablative and electron beam lithographic patterning, with characterisation by ellipsometry and Resonance Raman Spectroscopy.
LB films of the new phthallocyanine molecules have been prepared, characterised, and the interlayer electron tunnelling measured. The tunnel time is sub-nanosecond, and is related to designed molecular parameters.
Computer modelling of the LB film has been set up in two contrasting ways. The first is by detailed molecular dynamics, staying close to molecular reality, and is consequently fairly limited along the time axis. The second models molecular groups as cellular automata, and can follow motion for a long time, but at the expense of accuracy.
An automated system to view dipolar moments by fluorescent labelling now exists. These are being studied in phospholipids.
Progress on the manufacture of a new STM has been good, and the first prototype now exists. In addition, considerable progress has been made on the related scanning near-field optical microscopy (SNOM), with the creation of a novel SNOM tip; plasma propagating on a fine wire to a tip convert to light on reaching the tip.
Photoelectrons have been timed in their transit across up to 48 molecular layers. Recently, insertion of 2 molecular blocking layers has been shown to stop the electron transit, ie, electron motion is manipulated on a molecular scale.
Designs for memories in which electrons are shifted between layers, in a controlled manner, by electric fields or by light pulses, have been developed.
POTENTIAL
Charges on molecules, or the orientation of a molecular dipole, can be used to represent information. Information processing then requires manipulation and control of the motion of charge and dipole orientation. Information processing devices substantially smaller than those in conventional microelectronics can be foreseen.

Coordinator

Queen Mary and Westfield College
Address
Mile End Road
E1 4NS London
United Kingdom

Participants (5)

HELMUT HUND
Germany
Address

Wetzlar
Max-Planck-Gesellschaft zur Förderung der Wissenschaften eV
Germany
Address
Heisenbergstraße 1
70569 Stuttgart
UNIVERSITÄT TÜBINGEN
Germany
Address
Auf Der Morgenstelle 10C9
72076 Tübingen
University of Dublin
Ireland
Address
Trinity College
Dublin 2
Università degli Studi di Genova
Italy
Address
Via All'opera Pia 11A
16145 Genova