The outlook for new technology

IBM researchers have created the first single-molecule, electrically controlled light emitter: a carbon nanotube that measures 1.4 nm in diameter (Picture).

The researchers created the nanotube as a three-terminal transistor. The team engineered the device to be ambipolar, which allows the researchers to simultaneously inject into a single nanotube both negative charges (electrons) from a source electrode and positive charges (holes) from a drain electrode. When the electrons and holes meet in the middle of the tube, they neutralize each other, generating light.

By giving researchers electrical control over the emission process, the innovation will permit detailed study of the optical physics of carbon nanotubes. As for commercial potential, the nanotube happens to emit light at 1.5 microns, the wavelength common in today's optical-communications systems. And nanotubes with different diameters would emit wavelengths valuable to other applications. IBM states that designers may eventually build nanotube emitters into arrays or integrate them with silicon or carbon-nanotube electronic components.

Although exotic technologies, such as methanol fuel cells, hold promise for powering electronic devices, researchers haven't given up on squeezing more juice from lithium-ion technology. A team at Sandia National Laboratories has developed a composite anode material that could deliver twice as much energy-storage capacity as current graphite anodes. The material features small particles of silicon within a graphite matrix. Silicon offers more than 10 times the lithium capacity of current anode materials, but battery makers have avoided it because it suffers rapid capacity loss from battery cycling. The Sandia researchers discovered that their matrix arrangement overcomes this problem, resulting in a high-capacity material that maintains its capacity despite cycling.

Chemists at the Georgia Institute of Technology have attached a solid-state fluorescent material used in OLEDs (organic light-emitting diodes) to a universal polymer backbone—a research milestone that could eventually lead to more cost-effective OLED manufacturing (Picture). Current OLED-assembly methods deposit the fluorescent material, aluminum tris (Alq₃), under vacuum conditions. Attaching the material to a polymer makes it amenable to less expensive methods that are already in wide use for applying thin films, such as spin coating. The researchers have also tweaked the chemical composition of the material to produce colors.

Scientists at the Air Force Research Laboratory have demonstrated a 20W continuous-wave laser that creates an artificial guide star by exciting sodium atoms in the mesosphere, 90 km above the earth. Ground-based telescopes use such guide stars to measure and thus correct for atmospheric distortions. The laser produces a diffraction-limited, single-frequency, yellow beam at 589.159 nm and requires only 300W of wall-plug power and a 10-minute warmup time. The device also requires less chilling equipment than previous systems based on pulsed-dye lasers. The Air Force's interest in the technology centers on satellite tracking.