Graphene atoms (right) and a double strand of DNA (left). White spheres represent copper ions integral to the chemical assembly process. The fire represents the heat that is an essential ingredient in the technique. [Credit: Anatoliy Sokolov]

DNA template for graphene transistors breakthrough

DNA could be used as the template for producing a new generation of computer chips made from graphene, research from chemical engineers at Standford University, led by Professor Zhenan Bao, has revealed.

Their invention involved using DNA to assemble ribbons of carbon.

Graphene has all the hallmarks for becoming a next-generation semiconductor material – tiny dimensions and favourable electrical properties – if researchers are able to work out how to mass-produce it.

Many researchers, including Prof Bao and her co-authors Anatoliy Sokolov and Fung Ling Yap, believe that graphene ribbons, laid side-by-side, could create semiconductor circuits.

“Making something that is only one atom thick and 20 to 50 atoms wide is a significant challenge,” co-author Sokolov was quoted as saying on the Stanford engineering website.

The Stanford team came up with the idea of using DNA as an assembly mechanism because, physically, DNA strands are long and thin and exist in roughly the same dimensions as the graphene ribbons. Chemically, DNA molecules contain carbon atoms, the material that forms graphene.

Prof Bao and her team started with a tiny platter of silicon as support for the transistor, and then dipped the silicon platter into a solution of DNA (derived from bacteria) and used a known technique to ‘comb’ the DNA strands into relatively straight lines. Next, the DNA on the platter was exposed to a copper salt solution, which allowed the copper ions to be absorbed into the DNA.

The platter was then heated and bathed in methane gas, which contains carbon atoms. The heat sparked a chemical reaction that freed some of the carbon atoms in the DNA and methane. These free carbon atoms quickly joined together to form stable honeycombs of graphene.

“The loose carbon atoms stayed close to where they broke free from the DNA strands, and so they formed ribbons that followed the structure of the DNA,” Yap said.

The researchers also wanted to show that these carbon ribbons could perform electronic tasks. So they made transistors on the ribbons. 

“We demonstrated for the first time that you can use DNA to grow narrow ribbons and then make working transistors,” Sokolov said.

The paper drew praise from UC Berkeley associate professor Ali Javey, an expert in the use of advanced materials and next-generation electronics.

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