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Number 377, June 17, 1998 by Phillip F. Schewe and Ben Stein
NANOSCALE ELECTROCHEMISTRY, the use of electrodes and an electrically conducting liquid solution to drive chemical reactions that are confined to nanometer scales, has been achieved by German researchers (Rolf Schuster, Fritz Haber Institute, Berlin, Schuster_R@FHI-Berlin.mpg.de) employing a special scanning tunneling microscope called an "electrochemical STM." In their setup, the researchers immersed the STM's needlelike probe and the gold surface they wanted to study in an electrolyte consisting of copper sulfate and sulfuric acid. The STM's electrically conducting needle and the metallic gold surface acted like two electrodes in the setup. Then, the researchers applied 60-nanosecond-length voltage pulses between the needle and the gold surface, resulting in surface pits with 5 nm diameter and depths of 0.3-1 nm. The researchers believe that the voltage pulse oxidized the gold surface (caused it to lose electrons), creating gold ions which were then attracted to the tip, where they were reduced (i.e., they gained electrons). Reversing the voltage, they deposited 1-nm-high, 8-nm-diameter clusters of copper (formed by the reduction of copper ions from the electrolyte). The ultrashort pulses allow the researchers to enforce electrochemical changes on a local level. (Schuster et al., Physical Review Letters, 22 June 1998; figures at Physics News Graphics)
BEST ALPHA HEATING YET IN A TOKAMAK. At the Joint European Torus (JET, a huge donut-shaped vessel 9 m across) in England, the hydrogen isotopes deuterium and tritium are heated until they fuse, creating a helium-4 ion (also called an alpha particle) and a neutron. The ultimate goal, for a fusion reactor, is to render the neutron's energy into usable electricity, while the alpha's energy would be turned back into the plasma as a form of self-heating. Recent tests at JET have clearly observed the alpha self-heating at work: up to 10% of the plasma heating came from alphas and resulted in an increase in plasma temperature (P.R. Thomas et al., upcoming article in Physical Review Letters; paul.thomas@jet.uk). JET had a good year in 1997, establishing several records for fusion experiments: 21 MJ of fusion energy, 16 MW peak power, and 65% of input power turned into fusion output power.
A SMART PIXEL, a light emitting diode (LED) under the control of a field-effect transistor (FET), can now be made entirely out of organic materials on the same substrate for the first time. In general, the benefit of organic over conventional semiconductor electronics is that they should (when mass-production techniques take over) lead to cheaper, lighter, circuitry that can be printed rather than etched. Ananth Dodabalapur and his colleagues at Bell Labs (908-582-4266, anath@physics.bell-labs.com) have made 300-micron-wide pixels using polymer FETs and LEDs made from a sandwich of organic materials, one of which allows electrons to flow, another which acts as highway for holes (the absence of electrons); light is produced when electrons and holes meet. The pixels are quite potent, with a brightness of about 2300 candela/m2, compared to a figure of 100 for present flat-panel displays. (Dodabalapur et al., Applied Physics Lett., 13 July; see figure at Physics News Graphics) A Cambridge University group has also made an all-organic device, not as bright as the Bell Labs version, but easier to make on a large scale (Sirringhaus et al., Science, 12 June.)
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