Ultrafast photodetectors made from carbon nanotubes

Compiled by EuroPhotonics staff

A new time-resolved laser spectroscopy process enables scientists to measure the dynamics of electrons in nanoscale photodetectors – and it’s 100 times faster than existing methods. This research is expected to lead to advances in solar cells and optoelectronic components such as nanoscale photodetectors and photoswitches.

With a measurement setup developed at Technical University of Munich, scientists can resolve ultrafast optoelectronic dynamics of carbon nanotubes. A first laser excites electrons in the carbon nanotubes spanning the gap between two gold electrodes, while a second laser measures the resulting photocurrent. Courtesy of Dr. A. Holleitner, TUM.

The technique, developed by scientists at the Technical University of Munich, allows researchers to measure the precise speed of photoexcited electrons, which in carbon nanotubes travel about 800 nm in 1 ps. Their work appeared in the Jan. 12, 2011, issue of Nano Letters (doi: 10.1021/nl1036897).

At the heart of the photodetectors are carbon nanotubes with a diameter of about 1 nm, spanning a tiny gap between two gold detectors. The team used a pump-probe technique to measure the speed of the electrons. The method involves exciting electrons in the carbon nanotubes with a laser pulse, while a second laser is used to observe the dynamics of the process.

The work was funded by the German Research Foundation and the Center for NanoScience at Ludwig-Maximilians University of Munich.