Credit: © 2007 AIP

Bolometers are devices widely used in astronomy for monitoring electromagnetic radiation, and, more recently, for terahertz imaging in medicine. Their structure includes a region that absorbs radiation, and minimizing the volume of this feature is important for improving device performance. In conventional thin-film bolometers this volume is typically 0.1 µm3, but further reductions are necessary to meet the demands for faster and more sensitive bolometers.

Now, Mikhail Tarasova of the Institute of Radio Engineering and Electronics, Moscow, Russia and colleagues1 from Sweden have made bolometers with an absorption region made from a stack of single-walled carbon nanotubes. Bundles of thousands of nanotubes, both semiconducting and metallic, were deposited between Ti/Au electrodes on oxidized Si substrates.

The carbon nanotube bolometers were exposed to radiation with a frequency of 110 GHz, and exhibited a temperature response of 0.4 mV K-1 at 4.2 K with high sensitivity — as defined by a quantity called the 'noise equivalent power'. These figures of merit are better than those achieved with conventional metallic thin-film bolometers. The development of procedures for forming low resistance contacts to the nanotubes are expected to yield even higher-performance devices.