Ink aids molecular memory

A technique which could help store trillions of bits of information per square inch and help make quantum computing a possibility is being developed by researchers at

and

(UCL).

According to Dr Sandrine Heutz, of Imperial’s Department of Materials, the technique which involves controlling the magnetic properties of a commonly used blue dye, could revolutionise computer processing power and information storage.

Metal Phthalocyanine (MPc), used as a dye in textiles and paper, contains carbon, nitrogen and hydrogen and can also contain a wide range of atoms at its centre. Using either copper or manganese the team were able to manipulate the atom’s magnetic moment.

By experimenting with how clusters of MPc were grown on a plastic film, Heutz discovered how the metal centres could interact with each other and how these interactions could be controlled.

‘MPc likes to form crystals and stack in columns,’ said Heutz. ‘They are like staircases with the molecules as steps. If you chemically treat the film on which they are grown you can make them point in different directions and if you heat them you can change the steepness of the staircase and how much the molecules overlap.

‘Each cluster can be in one of three states: off, on and a different kind of on -entangled. When it is off or on the molecules are all facing the same direction, but when they are entangled the molecules are able to ‘talk’ to each other and they alternate their direction.

‘At the moment we have been able to get an on/off switch with copper and an on/entangled switch with manganese.’

The use of MPc molecules could help the development of ‘spintronics’ which relies on the spin of electrons to store enormous amounts of information in a small area. The third state means the on/off system of binary calculation can be expanded, meaning exponentially more information could be stored in very small areas. In theory each bit would only require two molecules 1nm³ in size.

Heutz cautioned that it could take a further five years before the technology can be used, as a series of practical problems will have to be looked at first.

‘The way we switch it on and off is very impractical but it demonstrates the effect,’ said Heutz. ‘We don’t need electricity to do the switch which would bring it’s own problems. We use heat, which is a mechanical process.

‘It is stable at room temperature and we can’t switch it on and off. We have to cool the system down to see the interactions and to do this we use liquid helium to get it between one and 10 kelvin.

‘The three main factors we are looking at now are getting it to work at higher temperatures, using different ways to do the switching and scaling it down.

‘We have definitely got ideas how to make it reversible and we know we can scale it down.’

The team have so far used clusters of 50nm² but they believe scaling the technology down is not a problem. Potentially, they could get it down to a two molecule cluster.

Heutz also believes these molecular interactions have the potential to process quantum bits (qubits) of information in quantum computing which could lead to processing power much greater than conventional computing.

‘We are still a long way off from applying this technology to the home PC,’ added Heutz. ‘However, in five years time our experiments will demonstrate that we will have the power to unleash the vast potential of information processing at the molecular level.’

The project is being run by the London Centre for Nanotechnology, a joint enterprise between Imperial and UCL. It is funded by the Royal Society, Research UK and the EPSRC. Industry interest is also starting to pick up, with Kurt J Lesker providing sponsorship to students.