Graphene memorises data in a flash


31 August 2011

A flash memory material based on graphene has been created for the first time and shows big advantages over current state-of-the-art technology. The material is almost twice as energy efficient compared to the industry standard and can store double the information. 

Graphene has long been tipped as the material which will eventually replace silicon semiconductors in electronics. Compared with competitor materials graphene should be cheaper, more robust and highly efficient. 

Flash memory uses tiny cells to hold information as a binary code. Each cell can be read as either a 0 or a 1 depending on whether it has been loaded with a charge or not. Graphene appears to be a promising material for flash memory. This is because it is good at holding a charge due to its high capacity for storing electrons because of densely packed electronic states at each of its energy levels. 

Graphene flash memory

The new structures lose only 8 per cent of their charge over a 10 year period

© ACS Nano

Now, a team led by Kang Wang from the University of California, Los Angeles has constructed a prototype graphene-based flash memory (GFM) material. The team discovered that, in practice, the cells only loose 8 per cent of their charge over 10 years, whereas the current state of the art devices lose 50 per cent over the same time period. This stability also means there is much less interference between cells and so they can be packed closer together. The result is that the new material already outperforms industry standards in data storage and energy efficiency at the prototype stage. 'By utilising graphene's unique properties, flash memory can be further scaled beyond what polysilicon, the current state-of-the-art, can achieve,' says Emil Song, a co-author of the work. 

GFM could be of use in any application where information needs to be written and rewritten. The term 'flash memory' conjures up images of USB pen drives, but the technology is also used in internal computer processors. The denser information storage capabilities of GFM could lead to further miniaturisation and better performance in consumer electronic equipment. 

'I'm quite astonished that it can already be done with a material which is far from perfect,' says Andrei Khlobystov, a reader in chemical nanoscience at the University of Nottingham, UK. 'One can draw a very beautiful diagram of graphene - with perfect hexagons - but this is far from the reality...you will have some holes, some carboxyl groups. There's still a lot of chemistry to do there in terms of perfecting the material, but it's exciting that already it's doing a very useful job.' 

Khlobystov says that fabricating the material involved applying some quite harsh conditions to the graphene, including etching with chlorine gas and oxygen plasma. The fact that the material can retain shape and function after these treatments is a testament to the strength of its covalent bonds. 

Josh Howgego 

 

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References

A J Hong et al, ACS Nano, 2011, DOI: 10.1021/nn201809k

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