Ontdekking IBM doorbraak voor nanotechnologie

16 juni 2006

Een nieuwe techniek die nanotubes exact plaatst waar ze nodig zijn kan een van de grootste bottle-necks bij de ontwikkeling van electronische apparaten op basis van nanotechnologie oplossen. Nanotubes zijn minuscule buisjes van koolstofatomen, die feitelijk maar uit één molecuul bestaan. 'The method uses a specially constructed molecule that attaches one end to a carbon nanotube and the other end to a strip of metal oxide that has been placed on piece of silicon. The nanotubes are just a few nanometres in diameter, and knowing exactly where a tube is means researchers can use it to make a transistor', zo zegt James B. Hannon, van IBM's T.J. Watson Research Center in Yorktown Heights, New York. 'We can use this approach to make lots of devices'.

Onderzoekers zijn er in geslaagd transistoren te maken op basis van dit soort nanotubes, die uiteindelijk moeten leiden tot kleinere en snellere computers. Tot nu toe echter was er geen efficiënte manier om nanotubes exact op specifieke posities te plaatsen. De IBM-ontdekking verandert dit. 'Some researchers have manipulated tubes one at a time with atomic force microscopes. Others have laid down thousands at random, and then created contacts and repeatedly tested them until they found a working circuit', zo vertelt Hannon over het werk van collega's. 'We created a molecule that bonds to nanotubes at one end and metal oxides at the other, and mixed this molecule into a solution containing nanotubes. This left each tube attached to a molecule. We then took a piece of silicon and dipped it into the nanotube solution – the silicon had previously had aluminium oxide stripes laid onto it using electron beam lithography. The free end of the molecule stuck to the aluminium oxide, holding the nanotubes in place. The next step was to heat the silicon to 600°C, which removed the sticky molecules and left the nanotubes in place, held there by Van der Waals forces. Finally, we used lithography to attach palladium leads to the nanotubes, completing the transistor'. Chris Papadopoulos, van de University of Victoria in British Columbia (Canada) is enthousiast over de ontdekking. 'What needs to be examined further is whether it can be used for large-scale integration. It's a step in that direction'. De techniek is nog niet perfect. De in totaal 49 testen leverden 'slechts' 28 werkende transistors op. Maar Hannon gelooft dat verfijningen in de techniek uiteindelijk honderdduizenden werkende transistors zullen opleveren waarbij de nanotubes op de juiste plek zijn geplaatst. De ontdekking is beschreven in het laatste nummer van Nano Letters .

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