Researchers have created a new kind of flash memory that uses graphene along with silicon, enabling more data to be packed into portable electronics.
Teams from the University of California and Samsung believe that using the atom thick sheets of carbon could help extend the viability of flash memory technology for years to come. Below a certain cell size, silicon becomes less stable, and this has the potential to halt miniaturisation, so the researchers have concentrated on studying graphene based technology. "We're not totally replacing silicon but using graphene as the storage layer," said Augustin Hong, who worked on the devices at UCLA. "We're using graphene to help extend the capabilities of the conventional technology." The graphene flash memory prototypes can be read and written to using less power than conventional flash memory and can store data more stably over time, even when miniaturised. The UCLA researchers also demonstrated that they meet the industry standard of 10year projected data retention. According to the developers, the graphene memory cells don't electrically interfere with one another; a problem with conventional flash cells that can cause them to malfunction. While similar research is being conducted on new kinds of computer memory that could hold more data, many of these alternatives require expensive materials and totally new manufacturing processes. Replacing silicon with graphene in flash memory cells could provide a simpler, more practical solution. Graphene flash memory cells perform better because of the material's unusual chemical structure and electrical properties. Part of the problem with silicon based flash is that as memory cells get smaller, the transistor gates have to be thicker relative to the rest of the circuit in order to store sufficient charge - and these thick gated cells tend to interfere with their neighbours. Because gates made from graphene are ultra thin they do not interfere with one another. Graphene can also hold much more charge than silicon without it leaking out - another problem with conventional flash as the cells are miniaturised. So far, the graphene flash memory cells the researchers have made are relatively large – around 10µm - but graphene, unlike silicon, has no known physical properties that would cause a dip in performance as the devices are miniaturised. Simulations results suggest that graphene made devices could be scaled down to about 10nm - conventional flash is expected to become unstable below about 22nm. The researchers note that in theory it should not be difficult to add graphene to chips, because the material is relatively stable and can be grown on wafers using processes that are already common in chip manufacturing plants.