Atom-Sized Electronic Devices Identified Within Carbon Nanotubes
Berkeley, California - Researchers at the Ernest Orlando Lawrence Berkeley National Laboratory has confirmed the presence of atomic size of the nanotubes electronic devices, hollow cylinders of pure carbon 50,000 times thinner than a human hair Qatar. Nanotube devices have been predicted by theorists, but this is the first evidence that such devices exist in reality.
Alex Zettl, a physicist with the Materials Science Division, Berkeley Lab (MSD) and professor of physics at the University of California, Berkeley, a study in which pure carbon nanotubes has been shown to act as a unit and two e-government, known as the diode.
"What we see is the world's smallest rate in the temperature, and one of only a few atoms in size," says Zettl. "When we grow nanotubes, electronic devices in the form of a natural for them."
Previous attempts to identify devices using nanotubes submicron electrical contact pads, which can only measure a small isolated parts of the tube. It is clear that researchers have measured the wrong sections. Zettl monitored by measuring the nanotubes over their entire length. Achieves this through the use of confidential information to clear the microscope micro-tunneling.
According to research reports in the latest issue of Science magazine (10/3/97). Also co-authored the paper with Zettl has Phil Collins, Zettl Research Group, Hiroshi Bando, electrical laboratory in Japan, and Andreas Thessaloniki and Richard Smalley of Rice University.
The nanotubes are only a few nanometers (billionths of a meter on) in diameter. If you exclusively from carbon particles, it is chemically inert, about 100 times stronger than steel, and offer a full range of potential electrical conductivity and thermal.
Carbon nanotubes were discovered by electron microscopy Japanese Sumio Iijima. They are created by heating ordinary carbon until boiling, then condense in a vacuum or inert gas. The carbon condenses in a series of six countries, like sheets of graphite, which loops and communication in the hollow tubes.
According to Qatar, is a pure carbon nanotube can conduct electricity if they were metal, it can serve as a semiconductor, meaning it will only make the current work is far from critical. According to the theory proposed by Berkeley Lab physicist Marvin Cohen, Steven and Louis, both also with the University of California at Berkeley, which is an electronic device that may occur at the interface between two different nanotubes, one containing a metal, which is playing the role of semi-conductors. This would result in a Schottky barrier ", which means that the current flowing in one direction - from the semiconductor to the metal. The plan proposed by Cohen and Louis, and two tubes are connected by the creation of a Ministry of Defense of the disadvantages of pair SBO (gangs of five to seven carbon atoms) in the interface zone.
Zettl and Collins was able to confirm that Schottky barriers exist along the length of carbon nanotubes. The key was the scanning tunneling microscope, or training in the workplace. And the monitoring mechanism and is characterized by a decrease in the smallest pyramid in the world of metal: a few layers of atoms in the decrease down to a single atom at a point. Berkeley researchers, the tip of the monitoring mechanism as part of a tangle of nanotubes on the surface and then slowly withdrawn. Forces Van der Waals could carry a single nanotube to adhere to the end of the training effort, careful researchers would be extended by the nanotubes on the substrate, on the other hand, much as fragmentation, fiber and the a nest of wire. Once in a single nanotube is extracted, the researchers that the tip-up mechanism to slide over the surface to measure changes in electrical current through it.
"We measure changes in the individual offer and the length of the nanotube force increased, suggesting that different segments of the nanotube exhibit different electronic properties," says Zettl. "The changes over very short periods, and was to propose a nano-tube.
Zettl nanotubes do not expect the night to replace the silicon in the electronics industry, but sees the possibility of the road. Should doping with atoms of silicon in electronic devices. The contract size, dopant atoms at the end and start moving and degrading device performance. Also the temperature of a problem in spite of silicon in the thermal conductivity is good. The use of diamond films with high thermal conductivity of an exception is proposed to protect the devices based on silicon, but this adds further complications in the production process. The size and the heat is not the case with nanotubes because they are linked by covalent bonds (which means that atoms believes firmly in place), and is expected to have a better heat conductor than either silicon or diamond at room temperature.
"Silicon will eventually hit a dead end, where devices can not be made any smaller," says Zettl. "Nanotubes are already smaller and have no problem with heat. You could not ask for anything better in the material. "
Instead of wiring devices in separate nanotubes for specific purposes, as is the case with silicon chips, Zettl suggests a better approach may be to a cube "tube", a mass of nanotubes are packed with billion devices. The tube can then be connected to a network of arbitrary shape "minicomputers". This network of lots will be able to train tasks and restructuring of the input / output architecture for its performance as it learns and grows. In other words, this computer is arbitrary and not only older, it gets even better.
"The idea is not far when you think about it," says Zettl and his group had built metal and tube feet of its kind. The cube can not fulfill its useful function, but Zettl says that does not result in an "interesting" to respond to input signals.
"Nanotechnology can be used in the traditional manner or you may have to leave in a completely different direction," says Zettl. "The technology is simply unable to learn much to use it."
Berkeley Lab is a U. S. Department of Energy national laboratory located in Berkeley, California. They were classified, scientific research and is managed by the University of California.
