World’s first carbon nanotube computer

26 September 2013
By Edd Gent
Mobile version
Share |
This wafer contains tiny computers using carbon nanotubes (Credit: Norbert von der Groeben)

This wafer contains tiny computers using carbon nanotubes (Credit: Norbert von der Groeben)

The world’s first carbon nanotube (CNT) computer has been built by Stanford University engineers.

Scientists have tried for years to harness the promising material – a semiconductor that has the potential to launch a new generation of electronic devices that run faster, while using less energy, than those made from silicon chips.

And while it has been roughly 15 years since carbon nanotubes were first fashioned into transistors, the on-off switches at the heart of digital electronic systems, imperfections have frustrated efforts to build complex circuits using the material.

But using new processes that overcome these imperfections the Stanford team has assembled a basic computer able to perform tasks such as counting and number sorting as well as running a basic operating system that allows it to swap between these processes.

"People have been talking about a new era of carbon nanotube electronics moving beyond silicon," said professor Subhasish Mitra, an electrical engineer and computer scientist and Chambers Faculty Scholar of Engineering who co-led the research. "But there have been few demonstrations of complete digital systems using this exciting technology. Here is the proof."

The team hope the research, published in the journal Nature, will galvanize efforts to find successors to silicon chips, which could soon encounter physical limits that might prevent them from delivering smaller, faster, cheaper electronic devices.

Progress in electronics has meant shrinking the size of each transistor to pack more transistors on a chip, but as transistors become tinier they waste more power and generate more heat.

"Carbon nanotubes (CNTs) have long been considered as a potential successor to the silicon transistor," said Professor Jan Rabaey, a world expert on electronic circuits and systems at UC Berkeley.

"There is no question that this will get the attention of researchers in the semiconductor community and entice them to explore how this technology can lead to smaller, more energy-efficient processors in the next decade."

Unlike silicon based electronics, CNTs – long chains of carbon atoms that are extremely efficient at conducting and controlling electricity – are so thin that it takes very little energy to switch them off, according to professor HS Philip Wong, co-author of the paper.

"Think of it as stepping on a garden hose," Wong said. "The thinner the hose, the easier it is to shut off the flow. CNTs could take us at least an order of magnitude in performance beyond where you can project silicon could take us."

However CNTs do not necessarily grow in neat parallel lines, as chipmakers would like, and depending on how the CNTs grow a fraction of these carbon nanotubes can end up behaving like metallic wires that always conduct electricity, instead of acting like semiconductors that can be switched off.

Since mass production is the eventual goal, researchers had to find ways to deal with misaligned and metallic CNTs without having to hunt for them like needles in a haystack prompting them to design a two-pronged approach that they call an "imperfection-immune design."

"We needed a way to design circuits without having to look for imperfections or even know where they were," Mitra said.

To eliminate the wire-like or metallic nanotubes, the Stanford team switched off all the good CNTs before pumping the semiconductor circuit full of electricity that concentrated in the metallic nanotubes, which grew so hot that they burned up and literally vaporized into tiny puffs of carbon dioxide.

To bypass the misaligned nanotubes the researchers created a powerful algorithm that maps out a circuit layout that is guaranteed to work no matter whether or where CNTs might be askew.

"This ‘imperfections-immune design’ (technique) makes this discovery truly exemplary," said Sankar Basu, a program director at the National Science Foundation.

The Stanford team used this imperfection-immune design to assemble a basic computer with 178 transistors, a limit imposed by the fact that they used the university’s chip-making facilities rather than an industrial fabrication process.

In a demonstration of its potential, the researchers also showed that the CNT computer could run MIPS, a commercial instruction set developed in the early 1980s by then Stanford engineering professor and now university President John Hennessy.

Though it could take years to mature, the Stanford approach demonstrates the possibility of industrial-scale production of carbon nanotube semiconductors, according to Naresh Shanbhag, a professor at the University of Illinois at Urbana-Champaign and director of SONIC, a consortium for next-generation chip design research.

"The Wong/Mitra paper demonstrates the promise of CNTs in designing complex computing systems," Shanbhag said, adding that this "will motivate researchers elsewhere" toward greater efforts in chip design beyond silicon.

 

How the Stanford team overcame the problems of misaligned and metallic carbon nanotubes

Latest Issue

E&T cover image 1607

"As the dust settles after the referendum result, we consider what happens next. We also look forward to an international summer of sport."

E&T jobs

  • Design Delivery Leader, Palace of Westminster Restoration & Renewal (R&R) - Engineering Lead

    House of Commons
    • City of Westminster, London (Greater)
    • Circa £65,000 (There may be more for an exceptional candidate)

    You will lead on a number of engineering infrastructure and associated workstreams under direction from the Deputy Director

    • Recruiter: House of Commons

    Apply for this job

  • Senior Engineer, Network Equipment

    Energy Networks Association
    • Westminster
    • £49-58k per annum, dependent on experience

    Manage issues and working groups relating to all types of equipment and assets used on the UK Transmission and Distribution Networks.

    • Recruiter: Energy Networks Association

    Apply for this job

  • Programme Manager, Network Resilience

    Energy Networks Association
    • Westminster
    • Competitive salary, dependent on experience

    Co-ordinate the network resilience, emergency planning and the Single Electricity Number (SEN) work in the ENA Engineering team.

    • Recruiter: Energy Networks Association

    Apply for this job

  • Assistant Professor (Tenure Track) of Smart Building Solutions

    Premium job

    ETH Zurich
    • Zurich, Canton of Zürich (CH)

    The successful candidate is expected to develop a strong and visible research programme in the area of control and diagnostics of building systems

    • Recruiter: ETH Zurich

    Apply for this job

  • Process Controls Leader

    Premium job

    Phillips 66
    • Humber Refinery, South Killingholme, North Lincolnshire DN40 3DW
    • £60k - 75k plus extensive Compensation and benefits package, dependent upon experience

    Experienced Process Control Leader providing leadership and technical support for Oil Refinery. Extensive Compensation and benefits package.

    • Recruiter: Phillips 66

    Apply for this job

  • Regional Technical Support Manager

    Premium job

    Siemens
    • Warwick, Warwickshire

    You will be required to lead the regional Customer Services strategy and resources to maximise Customer satisfaction.

    • Recruiter: Siemens

    Apply for this job

  • Communications Engineer

    BAE Systems
    • England, Hampshire, Portsmouth
    • Negotiable

    Communications Engineer Would you like to play a key role supporting the UK's Maritime Communications Infrastructure? We currently have a vacancy for a Communications Engineer at our site in Portsmouth. As a Communications Engineer, you will be carrying o

    • Recruiter: BAE Systems

    Apply for this job

  • MetOp-SG Receiver Project Manager

    Science and Technology Facilities Council (STFC)
    • STFC Rutherford Appleton Laboratory, Harwell, Oxfordshire
    • £37,213 - £50,926 (depending on experience)

    Project Manager to oversee the development, production and test of spaceflight components and integrated receiver systems

    • Recruiter: Science and Technology Facilities Council (STFC)

    Apply for this job

  • Financial Controller

    MBDA
    • Stevenage
    • Competitive Salary & Benefits

    An opportunity has arisen to manage a diverse range of financial controlling activities within the Equipment Team (ET) and newly Centres of Excellence (CofEx) function...

    • Recruiter: MBDA

    Apply for this job

  • Weapon System Product Support Manager

    MBDA
    • Stevenage
    • Competitive Salary & Benefits

    The Opportunity An opportunity has arisen within MBDA?s Customer Support & Services organisation for a strong competent leader to deliver a key Weapon capability primarily...

    • Recruiter: MBDA

    Apply for this job

More jobs ▶

Subscribe

Choose the way you would like to access the latest news and developments in your field.

Subscribe to E&T