Scientist from the University of Wisconsin-Madison are working towards making more powerful computers a reality. To that end, they have devised a method to grow tiny ribbons of graphene directly on top of silicon wafers. Graphene ribbons have a special advantage over graphene sheets - they become excellent semiconductors.
“Compared to current technology, this could enable faster, low power devices,” says Vivek Saraswat, a PhD student in materials science and engineering at UW-Madison. “It could help you pack in more transistors onto chips and continue Moore’s law into the future”. The advance could enable graphene-based integrated circuits, with much improved performance over today’s silicon chips.
“The main advantage of graphene nanoribbons is that electrons can travel faster through them, compared to silicon so you can make faster chips that use less energy,” says Mike Arnold, a professor of materials science and engineering at UW-Madison and a world expert in graphene growth.
Arnold is pioneer of a strategy to lay down long, thin strips of graphene—structures known as nanoribbons—on top a material called germanium. That’s useful in many ways. However, since germanium isn’t a widely used semiconductor, it can’t form the basis for computer chips.
Meanwhile, other researchers have not been able to overcome a major barrier in layering graphene nanoribbons onto silicon. Graphene reacts with silicon to form an inert and less useful compound called silicon carbide. Arnold’s group has developed an innovative method to avoid that obstacle.
By laying down a thin protective layer of germanium before applying graphene, the researchers could successfully grow graphene nanoribbons on top of silicon wafers. The thin germanium layers protected graphene from reacting with silicon, yet didn’t interfere with the nanoribbons’ semiconducting capabilities.
It’s an important first step toward creating graphene-based integrated circuits. And because the base layer is composed of silicon, the graphene nanoribbon technology can be easily integrated into existing electronic/computing components. “Our vision is to integrate graphene with existing devices,” says Arnold.
The scientists have patented their technology through the Wisconsin Alumni Research Foundation. One advantage of their synthesis approach is that it takes advantage of a scalable, industry-compatible chemical vapor deposition technique. Now, they’re working to improve the precision with which they lay down their nanoribbons so that they can achieve the complex patterns found in modern computer chips.
“We are using a few strategies to control the thickness and the orientation for the nanoribbons,” says Arnold. “We have a few really cool ideas.”