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17 Jun 2002
Nanotubes made of carbon, deposited as tiny spikes on a substrate, act as electron emitters that could lead to cheap and efficient displays, light sources and diodes.
A team of Russian researchers, led by Alexander Obraztsov, discovered that carbon nanotubes behave as electron emitters because they exhibit bonding patterns and electronic behaviour between those of diamond and graphite.
The team also found that, if conditions like temperature and pressure are carefully controlled, these tubes can be deposited perpendicular to a surface so that they are several atomic layers thick at the bottom and only one atomic layer thick at the top. These spiked points mean that the tubes are also field enhancers, similar to lightning conductors. The researchers believe that the optimum density of spikes is about 10 000 000 per square centimetre, which provides enough sources to give significant field emission whilst allowing each tube to be a field enhancer.
The emitters formed by this process are of a type known as cold cathodes. These are potentially valuable in displays, light sources, fast switching diodes and other electronic components. The efficiency of cold cathode driven light sources is thought to be higher than light sources based on light emitting diodes.
Cold cathodes based on carbon nanotubes are particularly attractive as they start to emit electrons at a low voltage (at about 1.5 volts per micrometre, the lowest published emission threshold).
The research into carbon-based cold cathodes was started in Moscow State University about five years ago and is now being commercialised in conjunction with CFB, a technology transfer company based in the UK, Russia and the US. Andrea Mica of CFB said that the company is currently in discussions with manufacturers of light sources and field emission displays.
This technology will be demonstrated at exhibitions in London and Birmingham the UK in September 1999.
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