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Yorktown Heights, N.Y., April 27, 2001 ... IBM scientists developed a breakthrough transistor technology that could preview how computer chips can be made smaller and faster than what is currently possible with silicon. As reported in the April 27 issue of the journal Science, IBM researchers have built the world's first array of transistors out of carbon nanotubes -- tiny cylinders of carbon atoms that measure about 10 atoms across, are 500 times smaller than today’s silicon-based transistors and are 1,000 times stronger than steel. The breakthrough bypasses the slow process of manipulating individual nanotubes one-by-one, and is more suitable for a future manufacturing process. This achievement is an important step in finding materials that can be used to build computer chips when silicon-based chips cannot be made any smaller -- a problem chip makers are expected to face in about 10-20 years. “This is a major step forward in our pursuit to build molecular scale electronic devices,” said Phaedon Avouris, lead researcher on the project and manager of IBM’s Nanoscale Science Research Department. "Our studies prove that carbon nanotubes can compete with silicon in terms of performance, and since they may allow transistors to be made much smaller, they are promising candidates for a future nanoelectronic technology.” Using Carbon Nanotubes as Transistors in Chips Depending on their size and shape, the electronic properties of carbon nanotubes can be metallic or semiconducting. The problem scientists had faced in using carbon nanotubes as transistors was that all synthetic methods of production yield a mixture of metallic and semiconducting nanotubes which “stick together” to form ropes or bundles. This compromises their usefulness because only semiconducting nanotubes can be used as transistors; and when they are stuck together, the metallic nanotubes overpower the semiconducting nanotubes. Beyond manipulating them individually, a slow and tedious process, there has been no practical way to separate the metallic and semiconducting nanotubes -- a roadblock in using carbon nanotubes to build transistors. The IBM team overcame this problem with "constructive destruction", a technique that allows the scientists to produce only semiconducting carbon nanotubes where desired and with the electrical properties required to build computer chips. New Technique: “CONSTRUCTIVE DESTRUCTION” The basic premise of “constructive destruction” is that in order to construct a dense-array of semiconducting nanotubes, the metallic nanotubes must be destroyed. This is accomplished with an electric shockwave that destroys the metallic nanotubes, leaving only the semiconducting nanotubes needed to build transistors. Here is how it works: 1. The scientists deposit ropes of “stuck together” metallic and semiconducting nanotubes on a silicon-oxide wafer, 2. Then a lithographic mask is projected onto the wafer to form electrodes (metal pads) over the nanotubes. These electrodes act as a switch to turn the semiconducting nanotubes on and off, 3. Using the silicon wafer itself as an electrode, the scientists "switch-off" the semiconducting nanotubes, which essentially blocks any current from traveling through them, 4. The metal nanotubes are left unprotected and an appropriate voltage is applied to the wafer, destroying only the metallic nanotubes, since the semiconducting nanotubes are now insulated, 5. The result: a dense array of unharmed, working semiconducting nanotube transistors that can be used to build logic circuits like those found in computer chips. Moore's Law states that the number of transistors that can be packed on a chip doubles every 18 months, but many scientists expect that within 10-20 years silicon will reach its physical limits, halting the ability to pack more transistors on a chip. Today, chip makers are constantly battling to make the channel length in transistors smaller and smaller. The channel is the path where data travels from one place to another inside chips. The IBM team has successfully used carbon nanotubes as the channel in the transistors they have built. Transistors are a key building block of electronic systems -- they act as bridges that carry data from one place to another inside computer chips. The more transistors on a chip, the faster the processing speed, indicating why this advance by IBM scientists could have a profound impact on the future of chip performance. Related Carbon Nanotube Work at IBM In the same report, the IBM scientists show how electrical breakdown can be used to remove individual carbon shells of a multi-walled nanotube one-by-one, allowing the scientists to fabricate carbon nanotubes with the precise electrical properties desired. The report also shows how the scientists fabricate field-effect transistors from carbon nanotubes with any variable band-gap desired. In parallel studies of carbon nanotubes, IBM researchers have been working to improve the electrical characteristics of individual nanotube transistors. The unpublished data from these studies show that if the carbon nanotubes are scaled up to the size of today’s silicon-based transistors, the performance would be the same. This proves that the smaller carbon nanotube transistors should allow for Moore’s Law to continue on its path when silicon cannot be made any smaller. The report on this work is published in Science, Vol. 292, Issue 5517, April 27, 2001. The authors of the report "Engineering Carbon Nanotubes and Nanotube Circuits Using Electrical Breakdown" are Phaedon Avouris, of IBM’s T.J. Watson Research Laboratory in Yorktown Heights, N.Y., Philip G. Collins, formerly of IBM, now with Covalent Materials in Emeryville, California, and Michael S. Arnold, an IBM intern from the University of Illinois. Selective breakdown of a multi-walled carbon nanotube and the building of nanotube transistors See "Constructive Destruction" Qucktime animation Read further scientific analysis Visit Nanotubes project page Get Carbon Nanotube Publications March, 2002 Nano-technology Poised for First (But Not Last) Optical Application Following more than 20 years of extensive research, nano-technology is about to make a significant impact in the telecommunications industry, with fiber-optic technology becoming its first “poster child.” What was once considered science fiction in films like “Fantastic Voyage” is being commercialized as optical subcomponents, or subwavelength optical elements (SOEs). First out of the gate with commercial nano-technology products in any industry sector appears to be NanoOpto Corp., a Somerset, NJ-based startup with proprietary nano-technology for designing and manufacturing components for optical networking. Founded in mid-2000 and based on 20 years of multimillion-dollar research in nano-photonics and nano-manufacturing, the company has already shipped prototype components to prospective customers for testing. Nano-photonics sees the light These SOEs take advantage of the physical principles that apply in the interaction of light and structures with dimensions far smaller than the wavelength of the light. With structural dimensions on the order of tens or a few hundreds of nanometers (hence “nano-technology”), the effects of reflection, refraction, and diffraction are highly localized and governed by a blend of classical optical and quantum effects. “Because of the novel interaction between SOEs and light, large optical effects are realized on a very small scale,” says Hubert Kostal, vice president of marketing and sales for NanoOpto. “In general, this allows a size reduction for the integrated component using the SOE and can also allow a reduction in the number of subcomponents required.” The advantages can be seen in the use of SOEs for polarization management. When light is incident on an SOE polarization beam splitter, for example, one polarization passes through and the other and is reflected back, creating a 180-degree separation in the space of less than a millimeter. In a number of optical-component applications where each polarization must be processed independently, that can result in a much more compact integrated optical component. Also, because of the scale of the nano-structures used, SOEs can exhibit a broad acceptance angle to simplify integration and alignment, allowing both architectural flexibility and lower tolerances in the manufacturing process. Proof in nano-technology Nano-structures and their capabilities have undergone extensive research over two decades at several universities, including Princeton University, the University of Minnesota, and Harvard University. For telecom applications, the two key breakthroughs were in gaining a deeper understanding of the usable effects of interactions between light and nano-structures and devising methods to reliably and repeatedly manufacture those nano-structures. These breakthroughs opened the door for adoption in a major industry: optical communications. “While most of the research work using nano-structures is being done in the biomedical field and consumer electronics areas, the first commercial production of what many believe is the next ‘S’ curve in the component and subcomponent fabrication area is going to be for subcomponents in the fiber-optic business,” says Peter Bernstein, president of Infonautics Consulting Inc., a research-analyst firm in Ramsey, NJ. “Thus, the fiber-optic industry is going to be the proof for the entire field of nano-based technologies.” This revelation, says Bernstein, is creating both excitement and challenges for companies like NanoOpto. The communications industry will likely be highly scrutinized in how it harnesses and leverages the potential of such a disruptive technology. But there are benefits beyond size-cost and power consumption are always high on the list for the acceptance of any new telecom technology. SOEs create the opportunity for integrated optical components to be built with much smaller dimensions. That equates to lower integration costs, smaller footprints, and less power consumption for equipment manufacturers. On a more immediate level, because of the simplicity of their integration, the use of SOEs can result in significant time savings and cost reductions in the manufacture of existing integrated optical components. “Some typical products on the radar screen for telecommunications applications would include polarization management equipment, filters, and photodetectors,” says NanoOpto’s Kostal. “SOEs are a platform technology that can be rapidly and easily adapted to numerous customized applications.” Increasing popularity As NanoOpto leverages its “first mover” advantage in commercializing SOEs and related technologies, the benefits of nano-photonics are sufficiently revolutionary to expect more companies to follow. In fact, Pirelli (Milan, Italy) recently announced a five-year alliance with the Massachusetts Institute of Technology to work on research and production of optical components for telecommunications based on nano-technologies.
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