Nano-circuits promise powerful palmtops.
© Y. Huang, X. Duan and C.M. Lieber, Harvard University
Ultra-minaturized electrical components could shrink supercomputers.
Researchers in the Netherlands and the United States have constructed simple computer circuits with electrical components many times smaller than those on commercial silicon chips1,2. These ultra-minaturized logic circuits hold out the prospect of hand-held computers as powerful as today’s state-of-the-art supercomputers.
Cees Dekker and co-workers at the Delft University of Technology in the Netherlands have used single molecules to produce logic circuits capable of basic arithmetical calculations1. The molecules are carbon nanotubes, tiny tubes of pure carbon just a few millionths of a millimetre (nanometres) wide.
Conventional diodes and transistors are etched out of flat sandwiches of silicon and other materials using acids. This approach struggles to make components smaller than about 200 nanometres across. Dekker and Lieber assemble their devices atom by atom. It is the difference between an artist chiselling away at a block of wood or gluing together matchsticks.
Carbon-nanotube transistors and even logic circuits have been made before. In 1998, Dekker’s group was the first to build a nanotube transistor; and last June, a team from IBM’s research laboratories in Yorktown Heights, New York, created logic circuits, called NOT gates, from nanotube transistors3. Dekker and colleagues have now wired up groups of nanotubes to make a variety of logic circuits, including a memory cell that could form part of a random-access memory.
One of the difficulties in making nanotube circuits on a large scale, Lieber points out, is that it is very hard to control the way the tubes conduct electricity. Some nanotubes are like metal wires, others act like semiconductors such as silicon. To make a nanotube transistor requires semiconducting rather than metallic conduction. But which kind of tube you get using existing synthesis methods is largely a matter of chance.
Lieber has much more control over the electrical properties of his nanowires. Transistors and other elements of logic circuits typically require two kinds of semiconductor, called p-type and n-type. The electrical currents are carried in these by positively and negatively charged particles, respectively. Lieber can grow both p- and n-type semiconducting nanowires.
Lieber crosses p-type silicon nanowires at right angles to n-type gallium-nitride nanowires. Devices form at the crossing points. By wiring several different devices together, the researchers produce all the major logic gates of computer circuitry.
PHILIP BALL | © Nature News Service
21.08.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau
AI implications: Engineer's model lays groundwork for machine-learning device
18.08.2017 | Washington University in St. Louis
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
22.08.2017 | Life Sciences
22.08.2017 | Life Sciences
22.08.2017 | Life Sciences