30 June 2013

Molecular electronics meets the #graphene rescue squad

The IEEE’s excellent nanotechnology blog, Nanoclast has an interesting take on research at the University of Copenhagen and the Chinese Academy of Sciences in Beijing. The story, Graphene Comes to the Rescue of Molecular Electronics, describes a chip design “whose initial application could be testing the molecular chips researchers envision”.

The news item leads us to a paper in Advanced Materials, Ultrathin Reduced Graphene Oxide Films as Transparent Top-Contacts for Light Switchable Solid-State Molecular Junctions. The paper's abstract, you'll have to pay to read the whole thing, describes "A new type of solid-state molecular junction ... which employs reduced graphene oxide as a transparent top contact that permits a self-assembled molecular monolayer to be photoswitched in situ, while simultaneously enabling charge-transport measurements across the molecules".

The IEEE based its write up on a press release from the University of Copenhagen, Danish chemists in molecular chip breakthrough. (Scientists always complain when journalists write in terms of 'breakthroughs' but don’t seem to mind using them when it suits their own needs.) The Danish take on the research is that "for the first time, a transistor made from just one molecular monolayer has been made to work where it really counts". It seems that Kasper Nørgaard, an associate professor in chemistry at the University of Copenhagen, sees the work as a first step towards proper integrated molecular circuits.

New platform for memory and chips


MIT was bound to be an active player with graphene, even though, excellent as it is, the place isn't quite as all conquering as the reputation might suggest. It does, though, have a world class media machine and its has just come up with the press release Ferroelectric-graphene-based system could lead to improved information processing. This tells us that "a new system that combines ferroelectric materials — the kind often used for data storage — with graphene, a two-dimensional form of carbon known for its exceptional electronic and mechanical properties".

The release reports on a paper in Applied Physics Letters by associate professor of mechanical engineering Nicholas Fang, postdoc Dafei Jin and three others. Like the Danish paper, this one makes some pretty bold claims. as the MIT release put its "The system would provide a new way to construct interconnected devices that use light waves, such as fiber-optic cables and photonic chips, with electronic wires and devices. Currently, such interconnection points often form a bottleneck that slows the transfer of data and adds to the number of components needed."

Unlike some papers on graphene, this one is based on a real device rather than a theoretical notion. “The team’s initial proof-of-concept device uses a small piece of graphene sandwiched between two layers of the ferroelectric material to make simple, switchable plasmonic waveguides.”

An interesting twist to the story is where the release quotes Dimitri Basov, a professor of physics at the University of California at San Diego “who was not connected with this research”. He told them that the MIT team has “proposed a very interesting plasmonic structure, suitable for operation in the technologically significant [terahertz] range”. But then he goes on to warn that “The key issue, as in all of plasmonics, is losses. Losses need to be thoroughly explored and understood.”

It isn't often that you read a press release that raises the sort of question that a writer should pose when following up a press release. But MIT's PR machine is seriously good, which partly explains the wider perceptions of the place.

Plasmonic switches on the infrared

There’s another contribution to graphene’s possibilities with  plasmonic devices over at Optics Express (open access). The paper, Graphene-based plasmonic switches at near infrared frequencies, describes research done at the École Polytechnique Fédérale de Lausanne where they designed various switches that can “dynamically control the propagation of plasmons on graphene surfaces at near infrared frequencies”. The Swiss researchers say that their results “have demonstrated that controlling the properties of very reduced graphene areas provides extremely large isolation levels between the input and output ports”.

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