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 1605

"We visit Barcelona, one of the smartest cities in the world, to find out what makes it so special. What does it look like and what is the future?"

E&T jobs

  • Web and Database Developer

    Hercules Site Services Ltd
    • Swindon, Wiltshire
    • £36,000 - £40,000 p/a

    Web and Database Developer to join Engineering department to develop the company website and support the Existing infrastructure.

    • Recruiter: Hercules Site Services Ltd

    Apply for this job

  • Software Compliance Consultant

    BAE Systems
    • England, Lancashire, Preston
    • Negotiable

    Software Compliance Consultant Would you like to be a part of an exciting and growing team, responsible for the long-term strategic management of software for BAE Systems? We currently have a vacancy for a Software Compliance Consultant at our site in Pr

    • Recruiter: BAE Systems

    Apply for this job

  • Consultant Engineer - Information Assurance

    BAE Systems
    • Barrow-In-Furness, England, Cumbria
    • Negotiable

    Consultant Engineer - Information Assurance Would you like to have a strategic influence on the development of Information Assurance (IA) policies for a national nuclear deterrence programme? We currently have a vacancy for a Consultant Engineer - Informa

    • Recruiter: BAE Systems

    Apply for this job

  • Junior Business Analyst - IKM

    BAE Systems
    • Hampshire, England, Portsmouth
    • Negotiable

    Junior Business Analyst - IKM Would you like to forge a career in the defence industry? We currently have a vacancy for a Junior Business Analyst - IKM at our site at Portsmouth Naval Base. As a Junior Business Analyst - IKM, you will be supporting the I

    • Recruiter: BAE Systems

    Apply for this job

  • Control Engineer

    Bank of England
    • Debden
    • Competitive

    We’re looking for a qualified engineer with experience of computer programming for engineering systems and instrumentation.

    • Recruiter: Bank of England

    Apply for this job

  • Principal Engineer - Software Verification

    BAE Systems
    • England, Cumbria, Barrow-In-Furness
    • Negotiable

    Principal Engineer - Software Verification Would you like an opportunity to work with military based software tackling some of the greatest software complexities and associated risk levels? We currently have a vacancy for a Principal Engineer - Software V

    • Recruiter: BAE Systems

    Apply for this job

  • Systems Engineer

    National Air Traffic Services
    • England, Hampshire, Fareham
    • Negotiable

    NATS is a leading air navigation services specialist, handling 2.2 million flights in 2013/14, covering the UK and eastern North Atlantic. NATS provides air traffic control from centres at Swanwick, Hampshire and Prestwick, Ayrshire. NATS also provides a

    • Recruiter: National Air Traffic Services

    Apply for this job

  • Field Application Engineer

    Intel
    • Madrid

    Responsible for giving product presentations to the customer describing how Intel products provide the optimum solution to their application.

    • Recruiter: Intel

    Apply for this job

  • Rail Engineer

    Frazer-Nash Consultancy Ltd
    • Burton, Dorking, Glasgow
    • £ Competitive + Benefits

    Some of the most exciting infrastructure projects in the UK over the coming years are in rail.

    • Recruiter: Frazer-Nash Consultancy Ltd

    Apply for this job

  • Electrical Power & HV Engineers

    Frazer-Nash Consultancy Ltd
    • Bristol, Burton, Glasgow, Gloucester, Plymouth, Warrington
    • £ Competitive + Benefits

    Frazer-Nash is currently embarking on a period of significant growth of our electrical, electronics, control and instrumentation capability.

    • Recruiter: Frazer-Nash Consultancy Ltd

    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