Graphene could cut cost of semiconductors

A graphene “copy machine” could soon be available to produce cheap, flexible and reusable semiconductors, say scientists.

Engineers at Massachusetts Institute of Technology (MIT) have developed a technique using graphene – single-atom sheets of graphite – to transfer crystalline patterns from a semiconductor wafer to the surface of the semiconductor material.

"You don't have to worry about the cost of the wafer – let us give you the copy machine,” said Jeehwan Kim, mechanical and materials engineer at the university. “You can grow your semiconductor device, peel it off, and reuse the wafer."

Traditionally, silicon is used as the wafer in the manufacture of semiconductors, but once the pattern is transferred onto the microelectronic material it is difficult to separate it from the wafer as they are too strongly bonded, making it a one-time use.

Graphene, on the other hand, has weak bonds – making it ‘slippery’ on surfaces – enabling it to be peeled off the wafer so it can be used for other semiconductors, creating a copy-and-paste effect and reducing the costs of manufacturing, according to the scientists.

The team placed graphene on wafers to grow semiconductor material over it. They discovered that graphene appeared “electrically invisible” when sandwiched between the two, meaning the top layer of the material could see through the graphene to the underlying wafer, imprinting patterns without being influenced by the graphene.

Graphene was once considered for semiconductor devices such as transistors – used to amplify or switch electronic signals and electrical power – but that requires turning the flow of electrons on and off and in graphene the electrons flow non-stop. Instead, the MIT engineers used graphene as an intermediate material, focusing on its mechanical features rather than its electrical properties.

The researchers are now using the technique to improve flexible electronics, by making bendable semiconductor devices such as LEDs and solar cells.

"Let's say you want to install solar cells on your car, which is not completely flat – the body has curves. You coat your semiconductor on top of it, peel it off and bend,” Kim said. “You can do this conformal coating even on clothing.”

The team plans to build a ‘mother wafer’ using graphene to create multifunctional, high-performance devices.

In 2016, semiconductor sales reached £264 billion worldwide, while the semiconductor industry spent £5.6 billion on wafers.

The study was published in the journal Nature.