Tag Archives: University of Wuppertal

Carbon nanotubes self-assembling into transistors on a gold substrate

I’m not sure this work is ready for commercialization (I think not) but it’s certainly intriguing. From an April 5, 2017 news item on ScienceDaily,

Carbon nanotubes can be used to make very small electronic devices, but they are difficult to handle. University of Groningen scientists, together with colleagues from the University of Wuppertal and IBM Zurich, have developed a method to select semiconducting nanotubes from a solution and make them self-assemble on a circuit of gold electrodes. …

An April 5, 2017 University of Groningen (Netherlands) press release on EurekAlert, which originated the news item, explains the work in more detail,

The results look deceptively simple: a self-assembled transistor with nearly 100 percent purity and very high electron mobility. But it took ten years to get there. University of Groningen Professor of Photophysics and Optoelectronics Maria Antonietta Loi designed polymers which wrap themselves around specific carbon nanotubes in a solution of mixed tubes. Thiol side chains on the polymer bind the tubes to the gold electrodes, creating the resultant transistor.

Patent

‘In our previous work, we learned a lot about how polymers attach to specific carbon nanotubes’, Loi explains. These nanotubes can be depicted as a rolled sheet of graphene, the two-dimensional form of carbon. ‘Depending on the way the sheets are rolled up, they have properties ranging from semiconductor to semi-metallic to metallic.’ Only the semiconductor tubes can be used to fabricate transistors, but the production process always results in a mixture.

‘We had the idea of using polymers with thiol side chains some time ago’, says Loi. The idea was that as sulphur binds to metals, it will direct polymer-wrapped nanotubes towards gold electrodes. While Loi was working on the problem, IBM even patented the concept. ‘But there was a big problem in the IBM work: the polymers with thiols also attached to metallic nanotubes and included them in the transistors, which ruined them.’

Solution

Loi’s solution was to reduce the thiol content of the polymers, with the assistance of polymer chemists from the University of Wuppertal. ‘What we have now shown is that this concept of bottom-up assembly works: by using polymers with a low concentration of thiols, we can selectively bring semiconducting nanotubes from a solution onto a circuit.’ The sulphur-gold bond is strong, so the nanotubes are firmly fixed: enough even to stay there after sonication of the transistor in organic solvents.

The production process is simple: metallic patterns are deposited on a carrier , which is then dipped into a solution of carbon nanotubes. The electrodes are spaced to achieve proper alignment: ‘The tubes are some 500 nanometres long, and we placed the electrodes for the transistors at intervals of 300 nanometres. The next transistor is over 500 nanometres away.’ The spacing limits the density of the transistors, but Loi is confident that this could be increased with clever engineering.

‘Over the last years, we have created a library of polymers that select semiconducting nanotubes and developed a better understanding of how the structure and composition of the polymers influences which carbon nanotubes they select’, says Loi. The result is a cheap and scalable production method for nanotube electronics. So what is the future for this technology? Loi: ‘It is difficult to predict whether the industry will develop this idea, but we are working on improvements, and this will eventually bring the idea closer to the market.’

Here’s a link to and a citation for the paper,

On-Chip Chemical Self-Assembly of Semiconducting Single-Walled Carbon Nanotubes (SWNTs): Toward Robust and Scale Invariant SWNTs Transistors by Vladimir Derenskyi, Widianta Gomulya, Wytse Talsma, Jorge Mario Salazar-Rios, Martin Fritsch, Peter Nirmalraj, Heike Riel, Sybille Allard, Ullrich Scherf, and Maria A. Loi. Advanced Materials DOI: 10.1002/adma.201606757 Version of Record online: 5 APR 2017

© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

Samsung ‘GROs’ graphene-based micro-antennas and a brief bit about the business of nanotechnology

A Feb. 22, 2013 news item on Nanowerk highlights a Samsung university grant (GRO) programme which announced funding for graphene-based micro-antennas,

The Graphene-Enabled Wireless Communication project, one of the award-winning proposals under the Samsung Global Research Outreach (GRO) programme, aims to use graphene antennas to implement wireless communication over very short distances (no more than a centimetre) with high-capacity information transmission (tens or hundreds of gigabits per second). Antennas made ??of [sic] graphene could radiate electromagnetic waves in the terahertz band and would allow for high-speed information transmission. Thanks to the unique properties of this nanomaterial, the new graphene-based antenna technology would also make it possible to manufacture antennas a thousand times smaller than those currently used.

The GRO programme—an annual call for research proposals by the Samsung Advanced Institute of Technology (Seoul, South Korea)—has provided the UPC-led project with US$120,000 in financial support.

The Graphene-Enabled Wireless Communication project is a joint project (from the news item; Note: A link has been removed),

“Graphene-Enabled Wireless Communications” – a proposal submitted by an interdepartmental team based at the Universitat Politècnica de Catalunya, BarcelonaTech (UPC) and the Georgia Institute of Technology (Georgia Tech)—will receive US$120,000 to develop micrometre-scale graphene antennas capable of transmitting information at a high speed over very short distances. The project will be carried out in the coming months.

The Graphene-Enabled Wireless Communication project, one of the award-winning proposals under the Samsung Global Research Outreach (GRO) programme, aims to use graphene antennas to implement wireless communication over very short distances (no more than a centimetre) with high-capacity information transmission (tens or hundreds of gigabits per second). Antennas made ??of graphene could radiate electromagnetic waves in the terahertz band and would allow for high-speed information transmission. Thanks to the unique properties of this nanomaterial, the new graphene-based antenna technology would also make it possible to manufacture antennas a thousand times smaller than those currently used.

There’s more about the Graphene-Enabled Wireless Communication project here,

 A remarkably promising application of graphene is that of Graphene-enabled Wireless Communications (GWC). GWC advocate for the use of graphene-based plasmonic antennas –graphennas, see Fig. 1- whose plasmonic effects allow them to radiate EM waves in the terahertz band (0.1 – 10 THz). Moreover, preliminary results sustain that this frequency band is up to two orders of magnitude below the optical frequencies at which metallic antennas of the same size resonate, thereby enhancing the transmission range of graphene-based antennas and lowering the requirements on the corresponding transceivers. In short, graphene enables the implementation of nano-antennas just a few micrometers in size that are not doable with traditional metallic materials.

Thanks to both the reduced size and unique radiation capabilities of ZZ, GWC may represent a breakthrough in the ultra-short range communications research area. In this project we will study the application of GWC within the scenario of off-chip communication, which includes communication between different chips of a given device, e.g. a cell phone.

A new term, graphenna, appears to be have been coined. The news item goes on to offer more detail about the project and about the number of collaborating institutions,

The first stage of the project, launched in October 2012, focuses on the theoretical foundations of wireless communications over short distances using graphene antennas. In particular, the group is analysing the behaviour of electromagnetic waves in the terahertz band for very short distances, and investigating how coding and modulation schemes can be adapted to achieve high transmission rates while maintaining low power consumption.

The group believes the main benefits of the project in the medium term will derive from its application for internal communication in multicore processors. Processors of this type have a number of sub-processors that share and execute tasks in parallel. The application of wireless communication in this area will make it possible to integrate thousands of sub-processors within a single processor, which is not feasible with current communication systems.

The results of the project will lead to an increase in the computational performance of these devices. This improvement would allow large amounts of data to be processed at very high speed, which would be very useful for streamlining data management at processing centres (“big data”) used, for example, in systems like Facebook and Google. The project, which builds on previous results obtained with the collaboration of the University of Wuppertal in Germany, the Royal Institute of Technology (KTH) in Sweden, and Georgia Tech in the United States, is expected to yield its first results in April 2013.

The project is being carried out by the NaNoNetworking Centre in Catalonia (N3Cat), a network formed at the initiative of researchers with the UPC’s departments of Electronic Engineering and Computer Architecture, together with colleagues at Georgia Tech.

Anyone interested in  Samsung’s GRO programme can find more here,

The SAMSUNG Global Research Outreach (GRO) program, open to leading universities around the world, is Samsung Electronics, Co., Ltd. & related Samsung companies (SAMSUNG)’s annual call for research proposals.

As this Samsung-funded research project is being announced, Dexter Johnson details the business failure of NanoInk in a Feb. 22, 2013 posting on his Nanoclast blog (on the IEEE [International Institute of Electrical and Electronics Engineers] website), Note: Links have been removed,

One of the United State’s first nanotechnology companies, NanoInk, has gone belly up, joining a host of high-profile nanotechnology-based companies that have shuttered their doors in the last 12 months: Konarka, A123 Systems and Ener1.

These other three companies were all tied to the energy markets (solar in the case of Konarka and batteries for both A123 and Ener1), which are typically volatile, with a fair number of shuttered businesses dotting their landscapes. But NanoInk is a venerable old company in comparison to these other three and is more in what could be characterized as the “picks-and-shovels” side of the nanotechnology business, microscopy tools.

Dexter goes on to provide an  analysis of the NanoInk situation which makes for some very interesting reading along with the comments—some feisty, some not—his posting has provoked.

I am juxtaposing the Samsung funding announcement with this mention of Dexter’s piece regarding a  ‘nanotechnology’ business failure in an effort to provide some balance between enthusiasm for the research and the realities of developing businesses and products based on that research.