| Jan 19, 2011 |
Speed detection of electrons in nanoscale photodetectors |
| (Nanowerk News) In solar cells and photodetectors, an optical radiation excites electrons to higher energy states, thereby a photocurrent begins to flow. Scientists led by Professor Alexander Holleitner, physicist at the Technische Universität Muenchen (TUM), have found a way to directly measure the time during which photo-excited electrons flow in nanoscale photodetectors ("Time-Resolved Picosecond Photocurrents in Contacted Carbon Nanotubes"). |
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| A carbon nanotube network is contacted by two metal strip lines. |
| The scientists could resolve the photocurrents on a picosecond time-scale which is about one-hundred times faster than is possible by conventional methods (a picosecond is one part in a billion of a millisecond). Most importantly, that is the time-scale at which electrons propagate in nanoscale photodetectors. |
| The reported method employs stripline circuits with a THz-band width, which are read-out by an ultrafast pump-probe laser spectroscopy. The researchers demonstrated the technique on carbon nanotubes with a diameter of only a nanometer (one millionth of a millimeter), which were electronically contacted by metal strip lines. |
| The results allowed the researchers to directly measure the speed of photo-excited electrons which is about 375 times slower than the speed of light. |
| The insights and analytic opportunities made possible by the presented technique are relevant to a whole range of applications. These include, most notably, the further development of optoelectronic components such as nanoscale photodetectors, photoswitches, and solar cells. |
| The studies were funded by the Cluster of Excellence Nanosystems Initiative Munich (NIM) of the Deutsche Forschungsgemeinschaft, the Center for NanoScience (CeNS), and LMUexcellent. |
| Source: Nanosystems Initiative Munich (NIM) |
