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September 16, 2011

CICC talk: Graphene could succeed CMOS and Sweden makes nanoribbons of graphene

1. EETimes - CMOS semiconductor technology could run out of gas at about 7 nm in 2024, and graphene is the leading candidate to replace it, according to a keynote address to be delivered at next week's Custom Integrated Circuits Conference (CICC).

Graphene faces plenty of challenges before it can become a successor to CMOS. "We have to make multiple billons of transistors in a sheet of graphene, but we've made less than a handful of transistors so far," said Meindl.




The graphene transistors have better electrical and thermal conductivity and current carrying capabilities than copper interconnects. They also are very attractive as a way to make MEMs, Meindl said.

"The most impressive graphene transistors described to date have been RF transistors," such as an amplifier for a 500 GHz analog signal, said Meindl. "Graphene switches are more challenging to make for many reasons including their leakage current," he added.

Meidl's lab is working on ways to make 15nm wide ribbons of grapheme that could be building blocks for graphene switches that are as fast and power efficient as silicon. The chief challenge is making the ribbons without damage at the edges that degrades the positive characteristics of the material.

2. Physicists from Umeå University and Finland have found an efficient way to synthesize graphene nanoribbons directly inside of single-walled carbon nanotubes.

They discovered a way to use the hollow space inside carbon nanotubes as a one-dimensional chemical reactor to make encapsulated graphene. An intriguing property of this space is that chemical reactions occur differently here compared to under bulk three-dimensional conditions.

– We used coronene and perylene, which are large organic molecules, as building blocks to produce long and narrow graphene nanoribbons inside the tubes. The idea of using these molecules as building blocks for graphene synthesis was based on our previous study, says Alexandr Talyzin.

The new material seems very promising, but we have a lot of inter-disciplinary work ahead of us in the field of physics and chemistry. To synthesize the material is just a beginning. Now we want to learn its electric, magnetic and chemical properties and how to use the hybrids for practical applications, says Alexandr Talyzin.

Nanoletters - Synthesis of Graphene Nanoribbons Encapsulated in Single-Walled Carbon Nanotubes


A novel material, graphene nanoribbons encapsulated in single-walled carbon nanotubes (GNR@SWNT), was synthesized using confined polymerization and fusion of polycyclic aromatic hydrocarbon (PAH) molecules. Formation of the GNR is possible due to confinement effects provided by the one-dimensional space inside nanotubes, which helps to align coronene or perylene molecules edge to edge to achieve dimerization and oligomerization of the molecules into long nanoribbons. Almost 100% filling of SWNT with GNR is achieved while nanoribbon length is limited only by the length of the encapsulating nanotube. The PAH fusion reaction provides a very simple and easily scalable method to synthesize GNR@SWNT in macroscopic amounts. First-principle simulations indicate that encapsulation of the GNRs is energetically favorable and that the electronic structure of the encapsulated GNRs is the same as for the free-standing ones, pointing to possible applications of the GNR@SWNT structures in photonics and nanoelectronics.

7 pages of supplemental material

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