Technique confirms graphene can be used in computer chips

The team used a new side-view imaging technique to visualise individual atomic graphene layers separated by a layer of insulating material within graphene-based devices. They found that each of the graphene layers within the devices — made by Roman Gorbachev of the university’s Condensed Matter Physics Group — had perfect alignment.

‘This is quite a surprising result,’ said Dr Sarah Haigh from Manchester University’s School of Materials and lead author of a paper written on the research in Nature Materials. ‘If you layer things up at that sort of scale, we would expect them to be distorted and full of gunk.’

According to Haigh, the alignment of the layers determines their properties. She said that ‘gunk’ would increase resistance and lead to an overall degradation in the material’s properties.

Graphene is a single-layered sheet of carbon atoms with excellent electrical conductivity and very low resistance.

The graphene devices made at Manchester University are handed to Haigh after their electrical properties have been measured. She then carves out a slice from the device and studies the layers.

‘I use something called a focus ion beam to fire a beam of gallium ions at the material,’ said Haigh. ‘That erodes and digs into the material.’

After the slice has been removed, it is turned on its side and studied with a transmission electron microscope down to the atomic level.

‘We use the X-rays that are emitted from the sample to analyse the composition because the energy of the X-ray is related to the elements that we’re looking at,’ explained Haigh.

The fact that the layers are perfectly aligned means that graphene layers can be used to design computer chips in three dimensions instead of just two.

‘You can imagine the order of magnitude improvement in processing speed and storage capacities,’ said Haigh. ‘It opens up new possibilities for designing chip architectures.’

The team will continue to use the new imaging technique to improve the performance of its graphene devices.