Graphene-Based Computers Come a Step Closer

Graphene is one of those materials that promise computers which can work much faster than they do today. Due to its very low electrical resistance, much less than that of silicon, it has great potential to be used in fast computers of the future. This superb conductivity is what helped the discoverers of graphene win the physics Nobel prize in 2010.

"It's an extremely promising material," says Konstantin Novoselov, who shared the Nobel prize with his co-discoverer, Andre Geim, both at the University of Manchester, UK.

However, this easy electron flow must be able to be stopped and started on command using transistors made out of it if the material is to be used in a computer - and this is tricky. Various attempts to make transistors out of it have been made, all with varying degrees of success, but these transistors suffered from significant leakage current (electron flow) when in their off state, making them reasonably useless for practical applications.

Now, the researches have found a way to reduce this leakage to the point where it's no longer a problem, by making a graphene sandwhich consisting of two layers of graphene with a filling of yummy molybdenum disulfide. The improvement is so good, that the leakage has been reduced by a factor of 10 compared with previous attempts at graphene-based transistors.

The molybdenum disulfide normally acts as a good insulator, preventing current flow, but a tiny current remains, due to the quantum tunnelling effect. This current can be amplified hugely by applying a voltage across the barrier, because it gives the electrons much more energy making them much more likely to "leak" across the barrier. This makes the device a transistor.

Unsurprisngly, the researches want to improve this leakage performance even further and suggest that the way to achieve this is to make the insulating layer thicker. Of course, doing so would require a higher drive voltage to get the current going, which would tend to produce more heat, so there's a trade-off here and they will need to find the sweet spot and/or work on using improved materials.

Source: New Scientist

This research was published in Science, DOI: 10.1126/science.1218461 (paywall)