Scientists at Shanghai Jiao Tong University, Stanford University, as well as other institutes in countries like the United States and China, have recently developed a new approach to make graphene nanoribbons or GNRs with smooth edges that are under 10 nanometers in width.

Such an approach, reported, introduced in the paper is based on the role of squashed carbon nanotubes or CNTs, tubes that are made of carbon that usually have diameters in the nanometer gauge.

GNRs as described in this report, are narrow and long graphene strips that are below 100 nm long. GNRs with smooth edges, a substantial bandgap, and high charge carrier mobility could be considerably valuable for a great range of electronic and optoelectronic uses.

Up to this time though, engineers have not introduced yet, an approach to prepare these helpful components on a great scale.

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Science Times - Graphene Nanoribbons Made from Squashed Carbon Nanotubes; A New Technique to Make GNRs Have Smooth Edges
(Photo : Nature Publishing Group on Wikimedia Commons)
Graphene Nanoribbons of controlled width

A Collaborative Study

According to two of the researchers, Professor Changxin Chen and Wendy Mao, who performed the study, the notion behind this work is that, if CNTs or the carbon nanotubes can be squashed into GNRs, "we would be capable" of generating narrow sub-5-nm wide GNRs from CNTs with tiny diameters.

Furthermore, GNRs prepared using this approach will be much slimmer compared to those obtained by previously applied approaches.

The recent research by Prof. Chen, Mao, and Prof. Hongjie Dai, which was published in Nature Electronics, together with their colleagues, was a collaboration between their respective research teams at Shanghai Jiao Tong University and Stanford University, with added input from institutions.

More so, a team Prof. Chen and Dai led primarily developed the approach and processes of the high-pressure or thermal solution to squash the CNTs into the GNRs, and on collecting characterizations of the prepared CNRs, computations, and measurements of device performances.

The research team of Pr. Mao carried out the high-pressure diamond anvil cell or DAC experiments through which CNTs were compressed.

Use of DAC for CNT Treatment

In a similar Reliable UK report, it was specified that another goal of this new collaboration was to attain atomically smooth edges throughout the entire GNRs, by shaping edge-closed GNRs that showed high material and device flexibility.

To generate their sub-10-nanometer-wide and -long GNRs that have atomically smooth-closed edges, the study scientists squashed CNTs together through the use of a high-pressure and thermal treatment approach developed by Chen and his team.

According to Chen and Mao, they used a DAC for the CNTs' high-pressure treatment. Essentially, the CNT samples were sealed in a chamber of samples in the DAC and then were compacted between the tips of a pair of diamond anvils.

For the squashed sample structure to be stabilized, the researchers performed a thermal treatment on the sample while it was at high pressure.

'Edge-Opened Nanoribbons'

The GNRs developed by the collaborating teams have atomically smooth, closed edges, not to mention very few faults.

Through the use of the approach the team devised, they were able to generate sub-5-nm GNRs, with 1.4 nm for minimum width.

Substantially, they discovered that a field-effect transistor or FET based on a 2.8-nm-wide edge-closed GNR showed a high Ion or Ioff ratio of >104, a 2,443 cm2 V-1 s-1 field-effect mobility, and a 7.42 mS on-state channel conductivity.

Describing their research, Chen and Mao said it proves that sub-10-nm-wide semiconducting graphene nanoribbons which have atomically smooth closed edged can be made by squashing carbon nanotubes through the use of combined thermal and high-pressure treatment.

With this method, nanoribbons, as narrow as 1.4 nm can be made. What's described in this report as "edge-opened nanoribbons" were fabricated as well, through the use of nitric acid, as the oxidant to selectively etch the squashed nanotubes under high pressure.

Related information about GNRs and GNTs is shown on Twistednanocarbon's YouTube video below:


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