A team of Stanford researchers has found a way to grow graphene nanoribbons using strands of DNA. This important development could be the key to large-scale production of graphene-based transistors that are orders of magnitude smaller, faster and less power-hungry than current silicon technology.

Graphene transistors

Chip manufacturers happily invest billions of dollars every year into making their transistors just a tiny bit smaller, faster, and less power-hungry. Though they may seem insignificant individually, when taken together these small year-by-year changes are the main factors that drive the exponential growth in the performance of today's microchips.Silicon transistors have come very a long way, but there are hard limits to how much they can shrink and how fast they can run: beyond a certain point, interferences brought on by both waste heat and leakage current make further progress nearly impossible. It should therefore come as no surprise that researchers have been looking into manufacturing transistors with alternative materials.

Graphene, a one-atom-thick layer of carbon atoms, is one of the frontrunners in this race. Because of its excellent electrical conductivity, it holds a lot of promise for producing faster and more efficient transistors that are also cheaper and significantly smaller than what we have today.

Graphene transistors can be produced using nanoribbons – very narrow strips of graphene only 20 to 50 atoms wide. However, mass-producing nanoribbons of such a small size has so far proven a tough challenge.

A little help from DNA

As it turns out, DNA molecules are approximately as big as the graphene nanoribbons that researchers are trying to create, and they also carry carbon atoms, which are the only constituent of graphene. This gave Stanford researcher Zhenan Bao and colleagues the idea to use DNA to help them assemble graphene nanoribbons.Using a known technique, the researchers first "combed" the DNA strands into relatively straight lines. They then exposed them to a solution of copper salt, which resulted in copper ions being absorbed into the DNA itself.

The researchers bathed the DNA strands in copper salt and then immersed it in methane to create nanoribbons (Image: Stanford University)

The DNA was then heated and surrounded in methane gas. The heat freed carbon atoms from both the DNA and the methane, and through a chemical reaction the carbon atoms quickly and orderly assembled to form graphene ribbons that followed the structure of DNA.

Applications

After succeeding in the experiment, the team took things a step further and actually used the technique to manufacture working graphene transistors.

High-performance graphene transistors built using the technique developed at Stanford (Image: Stanford University)

While the assembly process still needs to be refined (the carbon atoms sometimes bunch up together instead of forming in a clean one-atom-thick sheet), this work is truly paving the way toward a highly scalable, cheap and precise way to manufacture graphene electronics.

The researchers are now working on finding out more about the mechanisms that regulate the growth of the graphene sheets, and say that their technique could eventually be used to grow all-graphene integrated circuits directly.

A paper describing the research appears in the journal Nature Communications.

Source: Stanford University