March 8, 2011
Ultra-fast Photodetectors Out Of Carbon Nanotubes
Speed detection of electrons in nanoscale photodetectors
Carbon nanotubes have a multitude of unusual properties which make them promising candidates for optoelectronic components. However, so far it has proven extremely difficult to analyze or influence their optic and electronic properties. A team of researchers headed by Professor Alexander Holleitner, a physicist at the Technische Universitaet Muenchen and member of the Cluster of Excellence Nanosystems Munich (NIM), has now succeeded in developing a measurement method allowing a time-based resolution of the so-called photocurrent in photodetectors with picosecond precision.
At the heart of the photodetectors in question are carbon tubes with a diameter of about one nanometer spanning a tiny gap between two gold detectors. The physicists measured the speed of the electrons by means of a special time-resolved laser spectroscopy process "“ the pump-probe technique. It works by exciting electrons in the carbon nanotube by means of a laser pulse and observing the dynamics of the process using a second laser.
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, photo-switches and solar cells.
The studies were funded by the German Research Foundation (Cluster of Excellence Nanosystems Initiative Munich, NIM) and the Center for NanoScience (CeNS) at Ludwig-Maximilians-Universitaet Muenchen. Further contributions to the publication came from physicists of the University of Regensburg (Germany) and the Swiss Federal Institute of Technology, Zurich.
Original publication: Time-Resolved Picosecond Photocurrents in Contacted Carbon Nanotubes, Leonhard Prechtel, Li Song, Stephan Manus, Dieter Schuh, Werner Wegscheider, Alexander W. Holleitner, Nano Letters 2011, 11 (1), pp 269, DOI: 10.1021/nl1036897
Image Caption: Single-walled carbon nanotubes are promising building blocks for future optoelectronic devices. With this measurement set-up physicists led by Professor Alexander Holleitner (Technische Universitaet Muenchen) can resolve the ultra fast optoelectronic dynamics of carbon-nanotubes. A first laser exites electrons in the carbon-nanotubes spanning the gap between two gold electrodes while a second laser measures the resulting photo-current. Credit: Prof. Dr. A. Holleitner, TUM
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