Nanotubes realise uncooled photovoltaic infrared detectors

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Single-walled carbon nanotubes (SWNTs) have been used to create highly sensitive, uncooled photovoltaic infrared detectors.

Expected to be useful for industrial, military, manufacturing and scientific applications including telescopes and optoelectronic communications, so far infrared detectors have had to be cooled to avoid being overwhelmed by stray thermal radiation. But now a team of researchers from Peking University, the Chinese Academy of Sciences, and North Carolina-based Duke University have used SWNTs to create these infrared detectors that they claim are an order of magnitude more efficient than the semiconductor-based traditional mercury-cadmium-telluride alloy detectors.

‘These nanotubes exhibit strong and broadband infrared light absorption, which can be tuned by selecting nanotubes of different diameters. Also, due to their high electron mobility, nanotubes react very rapidly – on the order of picoseconds – to infrared light,’ said Sheng Wang, an associate professor in the Department of Electronics at Peking University in Beijing, China.

The team’s photovoltaic infrared detector is formed by aligning SWNT arrays on a silicon substrate. The nanotube arrays are then placed between asymmetric palladium and scandium contacts. These two metals have properties that collectively create what is known as an Ohmic contact, a region in a semiconductor device that has very low electrical resistance, which helps make the detector operate more efficiently.